A new boolit barrel

[Marlin Junky]

Hope everyone had a Merry Christmas...

Now onto my project...

I figure I've got to get a reamer ground anyway so, I was wondering if there's a way to modify the standard SAAMI specs of the 250 Savage to handle castings from Lyman 257420 and RCBS 257-120 equally well. I'll be purchasing a #3 or #4 contour Douglas or Shilen barrel from Brownells to keep the barrel cost down and that'll be good enough for now.

MJ

P.S. I was also wondering if anyone is making 250 brass from 308W and leaving the neck long (obviously incorporating a slightly longer custom 250 chamber).

[badgeredd]

Hope everyone had a Merry Christmas...

Now onto my project...

I figure I've got to get a reamer ground anyway so, I was wondering if there's a way to modify the standard SAAMI specs of either the 250S or 257R to handle castings from Lyman 257420 and RCBS 257-120 equally well. I'll be purchasing a #3 or #4 contour Douglas or Shilen barrel from Brownells to keep the barrel cost down and that'll be good enough for now. SAAMI 250 and 257 chambers below for reference sake.

MJ

P.S. I was also wondering if anyone is making 250 brass from 308W and leaving the neck long (obviously incorporating a slightly longer custom 250 chamber).

I order my chamber reamers from Dave Manson. On the last job, I called him and explained what I wanted, explaining that the rifle would be primarily shot with cast boolits. I then sent him a dummy cartridge with the boolit i intended on using along with 2 others telling him which was the primary and I would also like to be able to use the other 2 boolits. He ground my reamer accordingly and it functions flawlessly with all three boolits.

Edd

P.S. Dave will grind a longer neck if you want, just be sure to communicate your thoughts and he'll work with you.

[Marlin Junky]

Thanks Edd... I just downloaded his catalog.

MJ

[Houndog]

Dave Kiff at Pacific Tool and Guage will do the same and if some demension change from a reamer print on file is needed, it's free.

[Marlin Junky]

Dave Kiff at Pacific Tool and Guage will do the same and if some demension change from a reamer print on file is needed, it's free.

Thanks Houndog.

The next step is to determine if forming 250 brass from 308W is practical... maybe I should start another thread.

MJ

[felix]

MJ, remember, you want zero freebore no matter what. Have the reamer man make the neck long enough to contain the entire (check included) length of the LARGEST bearing surface that WILL be used. That will require a long case so there is enough metal to manufacture a much longer neck. ... felix

[Marlin Junky]

Felix,

I'm glad you brought up throating but doesn't the 250 diagram above depict zero freebore with a 3 degree throat?

I'm pretty happy with the neck diameter on the SAAMI 250 drawing, especially if mil-match 308 brass can be used, but the beginning of the throat at .261" seems a little sloppy... should that be reduced?... which in turn would lessen the throat angle.

MJ

[felix]

It looks like current reamers above are ok, except for neck length. Must equal your longest bearing surface. 120 grainers without a bore riding design are long in 250 bores.
... felix

[rhbrink]

I'm looking at the drawings and see a .125 freebore please correct me if I'm wrong but right at the end of the neck is the dimension 1.9222 the next dimension to the right where the lead angle starts is 1.9347. subtract 1.92222 from 1.9327 equals .125. Maybe I'm not seeing this right.

Sounds like a wonderfull wildcat to me just what the 250 Sav needs and a whole host of others could us the same improvement.

Richard

[felix]

I was hoping that was the length of the leade-in and not freebore. But, Richard, you might be correct. Gotta' ask the picture/designer man; he might be showing it wrong. Besides, the notes say 14 twist and that will be too slow for 120 grainers. If that 14 is correct, then 90 grainers would be tops for exquisit accuracy, and that would require a much shorter neck (for economy). ... felix

[Fluxed]

I posted in your other thread about making cases. I've done this several times and have the T-shirts. There's lots of potential troubles ahead and I'll be glad to help you with this. Tell us more about the rifle you want to end up with. Bench gun or repeater? Bolt, single shot, what?

[rhbrink]

It is hard to tell exactly by the drawing sometimes I look at it and think that he is showing a angle there but to me that is a rather long lead-in. Interesting project anyway and sure hope that it works.

I could see where sizing the 308 shoulder and the almost straight case down to a 250 Sav might be a problem may have to do that in several steps probably lose a few pieces of brass too.

Richard

[shooter93]

I'd get the dies and molds. Make dummy rounds and send those to the supplier. That's generally how I do it if looking for a cast rifle.

[Marlin Junky]

Felix,

Yeah, the neck would be approx. 0.4" if 7.62x51 Military brass (match-type w/o primer crimp) are run through a .250 Savage FL die... assuming that's feasible.

MJ

[Marlin Junky]

I posted in your other thread about making cases. I've done this several times and have the T-shirts. There's lots of potential troubles ahead and I'll be glad to help you with this. Tell us more about the rifle you want to end up with. Bench gun or repeater? Bolt, single shot, what?

Ruger short action... 0.470" bolt face... light weight sporter with varminter level accuracy is the goal.

Like to get RCBS 25-85-CM to shoot < 1MOA at 22LR velocities on the bottom end and RCBS 257-120 at around mach-2 on the top end.

MJ

[rhbrink]

What about the 6.5 X 47 Lapua? Neck it down to .257 it's a lot closer to the 250 Savage case than the .308 still going to be custom dies and reamers. I was looking a diagram of it and it has a .3 long neck already and if you necked it down it would get longer. Lapua brass is expensive but if you loose half of your 308 it might even out?

You might be able to size it to the 250 case size I don't know just guessing?

Richard

[Marlin Junky]

I'm looking at the drawings and see a .125 freebore please correct me if I'm wrong but right at the end of the neck is the dimension 1.9222 the next dimension to the right where the lead angle starts is 1.9347. subtract 1.92222 from 1.9327 equals .125. Maybe I'm not seeing this right.

Sounds like a wonderfull wildcat to me just what the 250 Sav needs and a whole host of others could us the same improvement.

Richard

1.9347 - 1.9222 = .0125" not .125"

MJ

[felix]

Boolit design first, then case capacity and form design to make 2400 fps max with slowest powder to be used, then reamer(s), then barrel and dies both made by barrel maker with reamers purchased. That is the preferred order of things. ... felix

[Marlin Junky]

Boolit design first, then case capacity and form design to make 2400 fps max with slowest powder to be used, then reamer(s), then barrel and dies both made by barrel maker with reamers purchased. That is the preferred order of things. ... felix

Correct... below's a pic of the boolit mold but the real deal maker is the ability to form the ".250 Long Neck" from 7.62x51mm match brass using off the shelf reloading dies.

[oneokie]

Correct... below's a pic of the boolit mold but the real deal maker is the ability to form the ".250 Long Neck" from 7.62x51mm match brass using off the shelf reloading dies.

Consider using 7-08 file trim die as a first step, a 6.5 file trim die, then a 25 cal. file trim die.

[Marlin Junky]

Consider using 7-08 file trim die as a first step, a 6.5 file trim die, then a 25 cal. file trim die.

Well, Larry Potterfield is supposed to have "just about everything for reloading" so I guess I'll take a look there first... thanks.

MJ

[felix]

Neck length:

[Marlin Junky]

Felix,

Some of that forward band is probably gonna have to be in the throat. I would guess you've indicated over .4". I don't have the mold yet but QuickLoad indicates the casting is 1.1" long.

MJ

[Marlin Junky]

Anyone know what'll happen to a .308 case run through the following die?

http://www.grafs.com/retail/catalog/product/productId/15930

I can't find a decent description of this die in Redding's PDF product catalog.

MJ

[rhbrink]

1.9347 - 1.9222 = .0125" not .125"

MJ

My mistake that looks a lot better to me. Dang fat fingers and little key boards. Slow brain too!

Good luck with the project hope that you keep us posted with the progress.

RB

[Nrut]

Anyone know what'll happen to a .308 case run through the following die?

http://www.grafs.com/retail/catalog/product/productId/15930

I can't find a decent description of this die in Redding's PDF product catalog.

MJ
MJ,
I have two old Savage 250-3000's made in the 20's (a 99TD and a 1920 bolt action) with very sloppy chambers..
At both ends of the chamber..
So I did some measuring on various makes of .308 brass I had on hand and found that they would fill the chamber much closer if necked down to .250 Sav.
I used the same die you listed above (Redding Form/Trim die) and it works like a champ forming 250 brass from 308 LC..
Made some dummy rounds to see if they would fit the chamber's..
They did and that's as far as I got..
Did this back in the 90's so I am a little foggy as to exactly my procedure..
IE. partial reform, re-lube and rotate the brass to finish reform..
I didn't need to neck ream because of the sloppy necks IIRC

Recently I reformed a bunch of 30-06 brass to 7X57 by running the 30-06 brass through a Redding 7X57 "shoulder bump die" and trimming and chamfering the brass using a Lee OAL case trimmer with the brass and shell holder in one of those battery operated drills...
Worked slicker than snot!

If you go ahead with this project please do a write up on your build including range work..

[rintinglen]

A couple years back during the last ammo shortage I tried several cases for making 250 savage brass. Based on my experience, I'd recommend necking UP .243 brass to get what you want. I lost a lot of cases due to wrinkles in the neck when necking down 308 cases. Making cases is a PITA that is compounded by losing 10 -20 % of your cases. Then the brass in the neck is very thick and required reaming. The 243 cases worked much better.

[Nrut]

I don't recall losing any .308 cases using the Redding Form & Trim die..
I'll see if I can find that die and some .308 LC cases today and make some more 250 Sav. cases out of them..
Been wanting to get back to shooting that little 1920 Sav. anyway and use it for deer hunting this year if it will stabilize my LBT 100gr. cast bullets..

[Marlin Junky]

I don't recall losing any .308 cases using the Redding Form & Trim die..
I'll see if I can find that die and some .308 LC cases today and make some more 250 Sav. cases out of them..
Been wanting to get back to shooting that little 1920 Sav. anyway and use it for deer hunting this year if it will stabilize my LBT 100gr. cast bullets..

That would be very cool... please post before and after pics of your reformed .308 LC brass. I'd buy the darn die right now but Graf is out of stock! I'll see if I can find it on Larry's website. 7-08 brass may be an option too. I really want the thicker neck walls since it's much easier to remove brass than add it. 8-)

MJ

P.S. Larry's got the following die with the correct Redding product number but the description says trim die only:

http://www.midwayusa.com/product/511069/redding-trim-die-250-savage

Is this the correct die Nrut? It's a 30+ day special order item so I'm concerned about Larry taking it back if it's not the correct die.

[Pat I.]

Why don't you just run a .259 diameter .100 long ballseat/freebore with a 2 degree included angle taper. I'm pretty sure the 250 Savage taper is 6 degrees included (3 degrees per side) and probably not the ideal for best accuracy with cast bullets. Size the bullet .2585 and order so you have a thousandths or two neck clearance either with turned or unturned brass, your choice. I don't know what the neck wall thickness is on factory Savage brass but if you had the reamer cut with the above mentioned throat and a .280 neck diameter you could turn it to .010 and have .0015 clearance. Otherwise decide what kind of brass you want to use, measure the neck wall thickness on a bunch of them. Multiply that times 2, add the bullet diameter, and order the neck a couple of thousndths over that. Save a lot of work that way and should shoot pretty good. I've messed around with a bunch of different wildcats and not only do they become expensive and a PIA but I never built one that did anything I couldn't have done with an existing design. There's no doubt you get the "I did it" rush but that wears off pretty fast when your fingers are aching from turning necks and your wallets a lot flatter from spending money.

[Marlin Junky]

Thanks for the input Pat.

I can sum up in three key points what I'm looking for:

1) Light weight 25 caliber rifle in a short action that'll primarily be a cast boolit shooter but capable of cleanly taking deer at 200+ yards with 100 grain Hornady, Sierra, Nosler, whatever bullets.

2) Cartridge case with a .4" (or thereabouts) long neck to enable the use of a wide range of boolit lengths; i.e., from Lyman 257420 to RCBS 257-120.

3) Cartridge case formed from the very common and readily available .308/7.62 NATO/7-08

That just about covers it. I'm not gonna spend 1000 bucks getting there and I don't need this for my ego. Actually, I prefer someone else had already done it so I can benefit from their experiences.

MJ

P.S. Actually, there's four points: 4) Gotta use reloading dies that already exist.

[Pat I.]

I'm not trying to talk you out of your project because I love this kind of stuff but i'd like to give my opinion on your key points based on my own experience if you don't mind

Thanks for the input Pat.

I can sum up in three key points what I'm looking for:

1) Light weight 25 caliber rifle in a short action that'll primarily be a cast boolit shooter but capable of cleanly taking deer at 200+ yards with 100 grain Hornady, Sierra, Nosler, whatever bullets.

The 250/3000 fits that bill to a T even with the .259 ball seat. The .308 has a .310 ball seat so it has the same .002 over groove diameter ball seat and shoots pretty well with jacketed bullets.

2) Cartridge case with a .4" (or thereabouts) long neck to enable the use of a wide range of boolit lengths; i.e., from Lyman 257420 to RCBS 257-120.

If you think of the ball seat as nothing more than an extension of the cartridge neck, which it is, why not put it in the barrel where it'll provide the maximum guidance. I don't know if it's going to be possible to build a gun that'll handle 65 and 120 gr bullets with equal results so you should consider which way you want to lean and build the gun in that direction. The other bullet weight would still probably shoot good but trying to make one size fit all is going to leave you with neither being at it's best.

3) Cartridge case formed from the very common and readily available .308/7.62 NATO/7-08

The 250-3000 is available and with no special case forming dies or forming required.

That just about covers it. I'm not gonna spend 1000 bucks getting there and I don't need this for my ego. Actually, I prefer someone else had already done it so I can benefit from their experiences.

Start adding up the cost of barrels, reamers, dies, moulds, labor unless you're going to do it yourself or have a freind and the cost of building a rifle for a wildcat adds up pretty quick
MJ

P.S. Actually, there's four points: 4) Gotta use reloading dies that already exist.

Aren't you going to have at least a neck sizer made for your cartridge? Maybe a seater?
-----

If nothing else at least reconsider that 6 degree leade when you order you reamer.

[geargnasher]

Short-chamber a barrel in .260 Remington with a reamer cut to same body/neck specs and case length but with longer/tighter neck. Cut off .260 sizing die same amount as the short-chamber. Use factory .260 brass, at factory trim length. Your chamber will be the same overall length as the .260, but the neck will be longer, shoulder farther back toward the head, case capacity will be less, and the overall body diameter/taper will be set back a bit with both chamber and die, making sizing 1F .308 brass a bit of work at the case head, but will remove any "bulge".

Gear

[45 2.1]

The main problem with standard reamers are:
1. neck is too long
2. neck is too big
3. case body is close to maximum
4. throating does not suit cast boolits

To cure these things:
a. specify neck length (better to trim a little than have them too long
b. form several cartridge cases from 308 and load them with 0.2585" boolits..... measure the neck diameters..... subtract 0.001" and specify that as the reamer neck diameter (tight neck that you have to turn cases for gives you a no slop chamber ....and unexpected accuracy when you get things right)
c. spec the reamer body closer to the minimum side than the maximum side
d. look at all the boolits you want to try..... measure the body lengths and compare to your case neck length..... you may or may not want any free bore, but you definitely want a 2 degree included entrance angle from a throat diameter of 0.259" into the rifling

Tolerances either make or break you here....... don't go with a standard reamer though.

[Pat I.]

MJ not to keep pouring questions and advise on you since you seem to be getting enough already and probably getting sick of it but why do you want a long necked cartridge? The only possible reason I could see for one would be to cover all the lube grooves for something you're going to drag around in the woods but with the quality of lubes available nowadays you can get by with only lubing the bottom groove or in most cases just the groove over the check. Besides that I see no advantage. I short chambered a 30 caliber barrel with an 06 reamer one time and formed the cases out of 35 Remington brass and I didn't see any big advantage when I got done. In fact I saw no advantage over cases like the 30 BR at all. The neck was right around what you're looking for or .400

[Marlin Junky]

All the information provided is extremely appreciated but I'm getting hung up on the following point because we're not getting a consensus of opinion:


..... you may or may not want any free bore, but you definitely want a 2 degree included entrance angle from a throat diameter of 0.259" into the rifling

I always though a freebore with zero tolerance (e.g., a .310" boolit combined with the SAAMI chamber below) would be a good thing but others are saying, no freebore. I would just as well design the .250's chamber so the forward driving band of RCBS 257-120 be outside the neck and supported by a close-fitting freebore section followed by a gentle throat angle as Bob indicated.

MJ

[Pat I.]

I can't understand why anyone would suggest no freebore. They'd have to explain that. A .090 or .100 thousandths long .259 freebore with a 1 1/2 or 2 degree included leade would work very well.

[swheeler]

I think the "zero freebore" becomes null if you have a freebore that is same size as the bullet/slip fit.

[Pat I.]

My only concern with my suggestion is the leade angle. I don't have that RCBS bullet so don't know how long the bore ride section is. I'm basing my leade angle opinion on .30 caliber bullets.

[Marlin Junky]

MJ not to keep pouring questions and advise on you since you seem to be getting enough already and probably getting sick of it but why do you want a long necked cartridge? The only possible reason I could see for one would be to cover all the lube grooves for something you're going to drag around in the woods but with the quality of lubes available nowadays you can get by with only lubing the bottom groove or in most cases just the groove over the check. Besides that I see no advantage. I short chambered a 30 caliber barrel with an 06 reamer one time and formed the cases out of 35 Remington brass and I didn't see any big advantage when I got done. In fact I saw no advantage over cases like the 30 BR at all. The neck was right around what you're looking for or .400

I'll never become sick of the advice, but the neck length issue (vs. some freebore) is the road-block here. Regardless of the possibility that the .257 Roberts may have too much case capacity, it also probably has enough neck to handle RCBS 257-120. Unfortunately, according to QL, with a .257 Roberts COL of 2.85" (short action mag box length), the RCBS 257-120's gascheck will be dangling in the powder space.

MJ

[Marlin Junky]

I can't understand why anyone would suggest no freebore. They'd have to explain that. A .090 or .100 thousandths long .259 freebore with a 1 1/2 or 2 degree included leade would work very well.

Ask Felix, I gotta go for now.

MJ

[geargnasher]

I believe the zero-freebore recommendation was intended to promote barrel longevity, i.e. there WILL be some freebore after the first few hundred shots, and the less there is to begin with the more shots there will be until it's time to set it back and rechamber. This assumed "full-tilt" loads where throat erosion is a concern with cast as well as jacketed.

Gear

[Pat I.]

Most if not all of the fixed cartridge cast bullet bench guns use a ballseat. The 6ppc jacketed guns use a ballseat. The .308 has a ballseat. Nothing wrong with a ballseat obviously and as far as the cast bullet guns go people aren't swapping barrels every year and the throats are lasting a long time. Improper cleaning without a bore guide and a good rod has eaten up more throats than cast bullets ever will.

[HARRYMPOPE]

I have to agree with Pat I on this one.-
The 30-30 has essentially no throat in its standard form.Run a .309 x 1.5 deg throater in a bit and "whammo" bullets fit and they will shoot much better.A 30BR I had with a the above throater run in .100 "wore out" at about 7000-8000 rounds before a set back was needed.This is running 30g of Scot 3032 and 190g bullets at pretty high pressures.I just kept bumping/tapering bullets and fitting them until the GC was about only 1/2in the case neck before i had it "freshed"

[Marlin Junky]

Why don't you just run a .259 diameter .100 long ballseat/freebore with a 2 degree included angle taper.

Problem is, I don't know anything about machining but I do know something about math and in order to step down from .259" to groove diameter (.257") at a rate of 1 degree per side, you'll need to cut only about 1/20" (*see note below)... not 1/10".


I'm pretty sure the 250 Savage taper is 6 degrees included (3 degrees per side) and probably not the ideal for best accuracy with cast bullets. Size the bullet .2585 and order so you have a thousandths or two neck clearance either with turned or unturned brass, your choice. I don't know what the neck wall thickness is on factory Savage brass but if you had the reamer cut with the above mentioned throat and a .280 neck diameter you could turn it to .010 and have .0015 clearance. Otherwise decide what kind of brass you want to use, measure the neck wall thickness on a bunch of them. Multiply that times 2, add the bullet diameter, and order the neck a couple of thousndths over that. Save a lot of work that way and should shoot pretty good. I've messed around with a bunch of different wildcats and not only do they become expensive and a PIA but I never built one that did anything I couldn't have done with an existing design. There's no doubt you get the "I did it" rush but that wears off pretty fast when your fingers are aching from turning necks and your wallets a lot flatter from spending money.

Thanks again for the input... I'll eventually get this to the point where I can communicate simple instructions to a gunsmith so there's no possibility of a screw-up.

Here's a sort of related question:

Looking at the Brownells catalog I see a couple options for .257" barrels. Between Douglas and Shilen, which one would be the better choice? I think I'd rather have the one with the most lands, all else basically equal.

MJ

P.S. It just occurred to me that I might be measuring the angle incorrectly. Is the angle measured from the the end of the free-bore to the center of the bore to or from the end of the free-bore to the top of the rifling?

[felix]

Ian is correct. Freebore becomes naturally extended very fast when pressure is 40K or above. No problem seating the projectile out further keeping up with the expansion. Normally, that is. That depends on the ignition choices which determines the barrel whip. Smoother the whip, the slower the change in muzzle direction which determines grouping. That is why some case capacities are magic for the typical bore and length. The most accurate cartridge (case, powder, primer, bullet combo) in this respect has been the standard 222, and prolly still is. Bigger guns shoot mo'betta' by default because we fail at the bench for all the standard reasons: ambient, recoil, attitude, etc. Freebore allows more critical seating without screwing with case neck diameter adjustments, and will be more accurate when the barrel is new. THESE ARE THE ODDS, nothing more. (My BR gun has 15,000 rounds at 40K and still shoots shotgun shells at 75 percent at a hunnert with "unlimited" freebore. Used to be 100 percent on the brass with cast at 150 yards plus). ... felix

[Pat I.]

Problem is, I don't know anything about machining but I do know something about math and in order to step down from .259" to groove diameter (.257") at a rate of 1 degree per side, you'll need to cut only about 1/20" (*see note below)... not 1/10".


I'm a little confused here. Could you explain what you mean a little better? The 1/20-1/10 is throwing me off.

As far as barrels of the two I like Shilen. The select match barrels I have are 6 groove. Don't know what Douglas uses or if Shilen uses 6 groove on their match barrels if that's what you're looking at. A call to them would be the best thing to do. If you decide to go with a Shilen look up The Barrel Man on google. He has pretty good prices on their barrels.

[Nrut]

That would be very cool... please post before and after pics of your reformed .308 LC brass. I'd buy the darn die right now but Graf is out of stock! I'll see if I can find it on Larry's website. 7-08 brass may be an option too. I really want the thicker neck walls since it's much easier to remove brass than add it. 8-)

MJ

P.S. Larry's got the following die with the correct Redding product number but the description says trim die only:

http://www.midwayusa.com/product/511069/redding-trim-die-250-savage

Is this the correct die Nrut? It's a 30+ day special order item so I'm concerned about Larry taking it back if it's not the correct die.
Yes that is the correct die..
Found the die and a bag of .308 89LC and re-sized some last night..
Tried using Imperial Sizing wax first just for grins thinking that it wouldn't work and it didn't..
Reason being back in the early 90's I tried it trying to size .357 MAX brass in a .256 Win. die and had to resort to using LEE re-sizing lube..
BullShops re-sizing lube worked well also..
The trick is to use very little lube just enough to take the shine off the brass..
The first two I tried I dented the shoulder until I backed off on the lube..
When forming 30-06 to 7X57 brass using a Redding Body die I found it best not to use any lube believe it or not..
The forming took more effort that I recalled using my little RCBS JR3 press and sometimes took two tries..
Changing to my LEE cast 4 hole turret press made the reforming a lot easier and I could do it with one stroke..

You might check out Sinclair for to this trim die as they list it and 4 cents cheaper to boot!!:-D..

You should really decide what brass that you are going to use to accommodate your custom reamer as I found the bases on the .250 R-P brass .465", .308 win. .466" and 89LC .469"+..
I don't have a 25 cal. pilot for my neck thickness measuring tool but got a rough measurement using a digital calipers at .250 .013", .308 .015", and 89LC .016-.017"..
Keep in mind I couldn't get the caliper down into the part of the case neck that was previously the 89LC shoulder so it may be thicker down there..

Oh and be sure to swage the primer pockets before you do any resizing if you are using a RCBS primer pocket swaging die!
Looks like I am going to have to learn how to ream mine..:roll:

In my opinion one of the main advantages of a custom reamer is getting a chamber neck that you can fill with your brass both in length and diameter..
I have a bunch of impact throat slugs from various cartridges and every one of them is .010 to .015 longer than the maximum trim length listed in Hornady's reloading manual..
Diameters are way over sized also..

As far as throats go I am still confused as to what is considered the best throat, leade angle, etc. as I haven't seen a consensus on what is best..



Pictures?
Heck I can barely down load from my camera to the computer and screwed that up last time I tried!

[Pat I.]

The most accurate cartridge (case, powder, primer, bullet combo) in this respect has been the standard 222, and prolly still is. felix

I think you'd have a hard time convincing guys shooting the 6 PPC of that. What's the life of a .308 barrel? Even the standard .222 has a ball seat and they seem to last a while. If the purpose of building a gun is to have it last unchanged for the next 20 generations then you might as well make it out of plastic because you'd have to leave a real one on the shelf anyway. If you want to build a gun with the most chance of success build it so that you'll get the best accuracy with the understanding that just like a pair of shoes it's gonna get some wear.

[felix]

As freebore lengthens, the leade angle is modified to mate with the dynamics of the projectile, that is what the projectile allows behind it and tears out what is in front from the last round. ... felix

[felix]

True, Pat, because most of them did not see and/or appreciate what was done in the warehouse. The PPC has a very restricted component range for its exquisite accuracy. The 308 is the BR choice for ONE relay only! The 222 will shoot in the 1s all day with 4198 thrown any which way (heavy varmint). The PPC shot in the 0s, but with very critical components (hunter). They tried the 25s, all different case sizes, and gave up after a few months. No good combos could be thought up at the time. ... felix

[Marlin Junky]

I'm a little confused here. Could you explain what you mean a little better? The 1/20-1/10 is throwing me off.

We'll just let that slide for now. It's only confusing the issue at hand... especially since I don't know how the angle is being measured.

What I need to figure out is how to make a reamer starting from SAAMI .250 Savage spec's. At this point I'm not even sure there is a single standard reamer to base the modifications. I think I would still like to incorporate a longer neck by reforming more popular cases; i.e., the 7-08, and .260 Remington and I suppose in a pinch even the .243.

MJ

[HARRYMPOPE]

Larry Jennings who held many CBA records when he was still with us had over 20000 on his Lilja before he got a new one.it had three setbacks and he used a very gentle "Ardito" throat that he bumped bullets to fit perfectly.This gun was still shooting nearly .5 MOA the last few matches i shot with him before the replacement.At that point the bore was a taper for about 3" in front of the throat he told me.

George

[Pat I.]

We'll just let that slide for now. It's only confusing the issue at hand... especially since I don't know how the angle is being measured.

What I need to figure out is how to make a reamer starting from SAAMI .250 Savage spec's. At this point I'm not even sure there is a single standard reamer to base the modifications. I think I would still like to incorporate a longer neck by reforming more popular cases; i.e., the 7-08, and .260 Remington and I suppose in a pinch even the .243.

MJ

If that's what you want then that's what you should do and I don't blame you one bit. I was only trying to give other options.

[Marlin Junky]

Felix,

Thanks for the explanation. For the bulk of it's use, the .250 will be operated at < 40K PSI. Only during deer season might it see any 55-60K PSI loads of Re17. If I can't find a good long range deer load by trying the 100 grain Hornady, Sierra and Speer bullets with a couple combinations of around 40 grains of Re17 then, I'll move onto another gun. In other words, the .250 probably won't see 300 rounds of copper patch in its lifetime.

MJ

[45 2.1]

P.S. It just occurred to me that I might be measuring the angle incorrectly. Is the angle measured from the the end of the free-bore to the center of the bore to or from the end of the free-bore to the top of the rifling?

I see that your confused.......... lets say that the angle is 2 degrees included.... which translates to 1 degree draft angle per side. You have a throat of 0.259" and a groove of 0.257" plus some land height (say 0.250" bore diameter for this example). per side you go down 0.001" from throat to groove and 0.0035" from groove to land top. The sum there is 0.0045" diameter change per side at 1 degree draft. The length of the 1 degree taper would be 0.0045" / Tan 1 degree = 0.257" long. You understand?

[Marlin Junky]

Pat,

I'm more concerned about being able to afford it while at the same time not driving a gunsmith over the edge, than I am getting exactly what I think I need. I need to read Nrut's post on case forming before going to work.

Regards,
MJ

[Marlin Junky]

I see that your confused.......... lets say that the angle is 2 degrees included.... which translates to 1 degree draft angle per side. You have a throat of 0.259" and a groove of 0.257" plus some land height (say 0.250" bore diameter for this example). per side you go down 0.001" from throat to groove and 0.0035" from groove to land top. The sum there is 0.0045" diameter change per side at 1 degree draft. The length of the 1 degree taper would be 0.0045" / Tan 1 degree = 0.257" long. You understand?

You betcha... in other words, the angle is measured from the bore (bottom of the groove) to the end of the free-bore rather than...
...from the end of the free-bore to the top of the rifling.

Thanks Bob,
MJ

[45 2.1]

You betcha... in other words, the angle is measured from the bore (bottom of the groove) to the end of the free-bore rather than...

Thanks Bob,
MJ

No..............doesn't matter where the angle is measured from. The angle is in relation to the centerline of the bore (wherever it is applied). Depending on what the specs are it can start at the chamber end, at throat diameter, end of freebore or not be there at all. Don't make it out as more than it is..............

[felix]

George, you prolly meant 3 inches in front of the NECK EDGE as it would be like in my gun. Yeah, it logically would be a taper instead of a straight freebore. I just don't want to know; I need to be optimistic and knowledge would be against me right now because something would have to be done. ... felix

[geargnasher]

Probably a topic for another thread, but since it has been breached here: Is there a consensus on the SHAPE of worn throats? Meaning, if a throat typically wears to a certain angle/curve, why not BEGIN with such via reamer design and zero freebore, such that a custom-matched boolit with plenty of bearing length in reserve will follow the freebore growth over time with no nose modifications down the road?

Gear

[Pat I.]

Have absoluterly no idea what the answer to that would be or if there even is an answer but there's a guy over on the Accurate Reloading forum who's shooting 10 shot 1/2 inch groups with a Finn 39 and 1 1/2 inch groups at 300 yards with one of those country's that start with an S (can't remember which one) milsurps. Think he might even be shooting flys off of cowpies with one of those Eyetalian Carcanos at 200 yds but can't be sure, might only be 175. If he can get those kind of results with one of those old warhorses he'd probably be the guy to ask your question.

[Marlin Junky]

No..............doesn't matter where the angle is measured from. The angle is in relation to the centerline of the bore (wherever it is applied).

Correct, I applied it (the "centerline") normal to the circumference of the bore (the .2500" hole). If the centerline is moved to the bore's axis of rotation, the angle doesn't change, hypotenuse gets longer.

6 of one... etc. Thanks again,
MJ

[Marlin Junky]

Probably a topic for another thread, but since it has been breached here: Is there a consensus on the SHAPE of worn throats? Meaning, if a throat typically wears to a certain angle/curve, why not BEGIN with such via reamer design and zero freebore, such that a custom-matched boolit with plenty of bearing length in reserve will follow the freebore growth over time with no nose modifications down the road?

Gear

The steeper the angle, the more the wear. Are all bench guns throated the same?

MJ

P.S. Ian, you brought up the .260. Has that become a modern standard of some sort of target shooting cult? I should probably get one of those Redding Form/Trim dies, a few cases of 7-08 and 260 and play around a bit. I'm sure the .243 will be around for a long while and easily acquired (I've even found a few empty .243's laying about on the range) but I'd rather neck down than up.

[Marlin Junky]

If there's anyone out there that has an RCBS 257-120 mold, could they please post the distance from the boolit's base to the trailing edge of the forward driving band?

If there's anyone out there who is interested in trading their RCBS 257-120 for a like-new Lyman 245496, (cast only a hundred or so boolits, oiled and stored) PM me. The reason the 245496 was only used once is because I didn't buy the rifle I intended to use it with. I bought the 245496 new from Buffalo Arms (one of their last molds) and it's pretty easy to get .245" on the bands. I didn't try real hard to get perfect castings from it but I'd be glad to send samples if someone is interested in a purchase or trade.

MJ

[Marlin Junky]

Here's what I have so far for the gunsmith & reamer guy. My mod's are in red. The .2578" measurement added to the case length is the .0045"/(tan 1) discussed earlier.

I need to decide how much neck & freebore to add and whether the neck diameters are the best choice. 0.286" at the case mouth will allow .0135" neck walls with .259" boolits.

At this point I'm concerned that I'm gonna end up with a real long throat for my 100+ grain copper patchers. I have plenty of magazine box to house a 2.75" round and the extra powder space should get me near 2900 fps (22" barrel) with Re17 and a 117 grain Sierra SP. According to QuickLoad though, the bullet will only be .23" inside the case neck using a 2.75" COL.

Thank you for the interest,
MJ

P.S. I added .12" of case neck which is an estimated guess of how much length can be added by running .260 brass through a .250 form/trim die. Do I still need some freebore to handle RCBS 257-120? I still want to be able to use copper patch for 200+ yard deer hunting.

[swheeler]

Have absoluterly no idea what the answer to that would be or if there even is an answer but there's a guy over on the Accurate Reloading forum who's shooting 10 shot 1/2 inch groups with a Finn 39 and 1 1/2 inch groups at 300 yards with one of those country's that start with an S (can't remember which one) milsurps. Think he might even be shooting flys off of cowpies with one of those Eyetalian Carcanos at 200 yds but can't be sure, might only be 175. If he can get those kind of results with one of those old warhorses he'd probably be the guy to ask your question.

Heck every gun that guy owns shoots bug holes!:) Those flies he's shooting are swarming BULL pies, and there's lots of bull over there;)

[ammohead]

MJ, 22-250 is just 250 brass necked down. Neck it back up and your in business. It works, I've done it.

[Marlin Junky]

MJ, 22-250 is just 250 brass necked down. Neck it back up and your in business. It works, I've done it.

You don't get the extra neck length I'm looking for and the neck walls will be thinned out.

MJ

[Willbird]

Mr Oliver77 and I made up about a dozen 22-250 cases from 308 brass, it was not fun and the necks ended up really thick..thick enough that the cases in theory would not need re sized to hold a bullet. I'm wondering if you could push the shoulder back into a sharper shoulder then blow the body out to regain the case capacity ?? Maybe not as straight as an Ackley case. If a longer skinnier case would work then have a look at necking 220 swift brass up to 250 and also pushing the shoulder back ?? It still has a .473 rim dia.


The 22-243 middlestead I think is an example of ending up with a longer neck and sharper shoulder angle than the parent ctg had ??

Pushing the neck back on the 243 and making the shoulder angle sharper in the bargain sure does look nice mentally though :-).

Hmm what about taking 6.5 creedmore, and just pushing the shoulder back to get a longer neck and also necking down to 25 ??
http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1487919

[Pat I.]

Pushing the neck back on the 243 and making the shoulder angle sharper in the bargain sure does look nice mentally though :-).

If you're stuck on the long neck idea I'd have to agree 100% even without the sharper shoulder. The neck wouldn't thin out much if at all going up one caliber. You'll be ordering a reamer anyway so could make the chamber neck diameter anything you wanted to compensate if it was a bit thinner. You mentioned you had some .243 range brass. If you have a set of .250 dies anneal a piece and give it a try. It might be just what you're looking for.

[felix]

Sharp shoulders are of no particular advantage for boolits. Enough for solid head spacing is enough, say 20 degrees. Sharp shoulders tend to speed up the mid-speed powder selections, unless the case is long, say more than 2 inches (primer selection problem with the smaller cases is the reason). The long sloping case sides are an advantage as well.

I have no idea what the leade looks like after several hundred 40K rounds. I am sure the freebore plus leade (total throat) was decided upon finally by the warehouse guy (Virgil?) for the PPC. There would be no advantage for anyone to improve the 0s grouping by changing anything discovered, so I would ASSUME no smithy would chance a different reamer design for a competitive gun. Anyway, 25 caliber is a different beast with its own peculiarities when launching BR styled projectiles (weight, ogives, et al for a required slow twist via experience). Besides, I would think the leade will be squirrelly after some time from the swirling gas; definitely not round any more. Could be a reasonable reason why the barrels are taken off-line after 1000 rounds or so. Case neck length would have a lot to do with timing this squirrelliness. ... felix

... felix

[Willbird]

Sharp shoulders are of no particular advantage for boolits. Enough for solid head spacing is enough, say 20 degrees. Sharp shoulders tend to speed up the mid-speed powder selections, unless the case is long, say more than 2 inches (primer selection problem with the smaller cases is the reason). The long sloping case sides are an advantage as well.

I have no idea what the leade looks like after several hundred 40K rounds. I am sure the freebore plus leade (total throat) was decided upon finally by the warehouse guy (Virgil?) for the PPC. There would be no advantage for anyone to improve the 0s grouping by changing anything discovered, so I would ASSUME no smithy would chance a different reamer design for a competitive gun. Anyway, 25 caliber is a different beast with its own peculiarities when launching BR styled projectiles (weight, ogives, et al for a required slow twist via experience). Besides, I would think the leade will be squirrelly after some time from the swirling gas; definitely not round any more. Could be a reasonable reason why the barrels are taken off-line after 1000 rounds or so. Case neck length would have a lot to do with timing this squirrelliness. ... felix

... felix

I have not ponied up for say Quickload yet...but I have not seen much real world data over the years to show that case shape, and even length/dia ratio's within reason making one case that hold 40 grains of H20 behave differently load/velocity wise than another one holding 40 grains of H2O that has a different shoulder angle.

Case shape as I understand it DOES have quite an impact on how cases stretch or do not stretch at a given PSI.

The nice thing about the 6.5 creedmore is you do not have to DRASTICALLY alter the parent ctg.

[felix]

True, Willbird. It's the ignition and barrel whip characteristics, not max pressure per se, but instead it's WHERE/WHEN that max pressure occurs. Light loads are of no concern, really, because coming up with those is half the fun if not more so with a new gun. ... felix

[Marlin Junky]

The nice thing about the 6.5 creedmore is you do not have to DRASTICALLY alter the parent ctg.

Is forming .250 Savage cases from .260 Remington cases a drastic alteration?

MJ

[Willbird]

Is forming .250 Savage cases from .260 Remington cases a drastic alteration?

MJ

After looking at the dims in Lyman 48............I guess not :-). I had just pictured the shoulder further forward in my minds eye :-). It must be all the body taper you have to blast onto the 308 or the 260 that makes you ^%$#@ when your trying to do it :-)...we were going 308 to 22-250 though. If I were to set out to do it I would match case capacity without adding in all the case body taper.

Bill

[rhbrink]

Ha! 25 BR? Take a 30 BR leave the case body and shoulder the same and just squeeze the 30 cal neck down to 25. There are a lot of people that use the 6mm BR for deer and antelope. If you absolutely had to you can make BR cases out of .308 as I believe that is how it was originally done guess that it could be done.

RB

[Marlin Junky]

Bump for my drawing edit in post 66 (http://castboolits.gunloads.com/showthread.php?176454-A-new-boolit-barrel&p=1981022&viewfull=1#post1981022).

MJ

[Marlin Junky]

I decided to base this .25 on the RCBS 250-3000 28º to facilitate brass forming (too much taper in the standard 250 body); so, if anyone runs into said reloading dies that need a home, please PM me.

Thank you,
MJ

[Harter66]

Just as a gee wiz RCBS stocks 308 to 22-250 forming sets. My Dad had a set 30 yr ago.

If I were going to do this cartridge....... I'd use a 300 Savage sizer to get shoulder to head length, then a 7mm08 ,243 and last a 250 Savage sizer.

As far as cutting a chamber I'll opt for a simple solution. I'd rough in a chamber maybe finish it for head space . The use a standard straight reamer to lengthen the neck as desired . Last use a throating reamer to finish to desired shape. A custom throater is much less than a custom chamber reamer.

I've been musing,specing,and tinkering on a 7mm6.8 SPC for a year. While this is of little help it may allow you to look at this from a different angle. My solution is to rough chamber w/7-30 Waters for the neck and throat and finish and head space w/6.8 SPC. Finished I have I've a common case ,a head that fits my bolt face and a bore throat that I've moulds and sizers for and my custom dies are a standard set w/the neck relieved from 295 to 306 dia. While this is not the same as you are wanting it is similar. I figure some engineer was paid a lot of money to make several bad cuts 80 or so years ago on a 250 Savage,I'd follow his leade. Pun intended

[rhbrink]

MJ have you thought about just necking a 308 case down to .25? With you thinking of going to the 250 IMP I just can't see that much difference in those two. I don't have a drawing of the 250 IMP but I'm thinking that you still have to push the shoulder back .030 to .040 how much would you really gain? I just don't know how longer the neck would get I'm thinking that it surely grow some?

RB

[Marlin Junky]

MJ have you thought about just necking a 308 case down to .25? With you thinking of going to the 250 IMP I just can't see that much difference in those two. I don't have a drawing of the 250 IMP but I'm thinking that you still have to push the shoulder back .030 to .040 how much would you really gain? I just don't know how longer the neck would get I'm thinking that it surely grow some?

RB

I want a 2º included angle in the throat so a non-standard reamer needs to be ground anyway. I'll have to see if I can acquire reloading dies for the RCBS 250-3000 (28º shoulder) first, but the goal is to put a 0.4" long neck on the RCBS 250-3000. If the dies are gonna set me back 3 clams, I'll do something else. I'm not even "married" to the .25 caliber bore size but it seems to be the best choice on a short action for small varmints through meat deer at longer ranges (the latter with copper patched boolits).

MJ

[Willbird]

I want a 2º included angle in the throat so a non-standard reamer needs to be ground anyway. I'll have to see if I can acquire reloading dies for the RCBS 250-3000 (28º shoulder) first, but the goal is to put a 0.4" long neck on the RCBS 250-3000. If the dies are gonna set me back 3 clams, I'll do something else. I'm not even "married" to the .25 caliber bore size but it seems to be the best choice on a short action for small varmints through meat deer at longer ranges (the latter with copper patched boolits).

MJ

Here is what Redding lists in that general ctg.

250 Savage (250-3000) group B
250 Savage Improved 40° group D
250 Savage Improved 28° Custom


Their custom 2 die sets retail at $180
Group D retail is $138
Group B is $93.90 retail (85 at midway)

Dave Kiff's reamers are all $155 for live pilot, you spec it how you want it.

RCBS 2 die set is only 138

http://www.midwayusa.com/product/939695/rcbs-2-die-set-250-savage-improved-28-degree-shoulder

[nanuk]

has anyone looked into the base diameters?

I have read where the base of most factory commercial brass is slightly undersized, or at least near the minimum size.

this makes for a sloppy fit, canting the cartridge if the neck fits tight.

necksizing overcomes this a bit, but that assumes the cartridge expanded concentrically.

is it possible to use, say the 6.5x55 brass that is slightly larger, and squeezing that puppy down to fit perfect in the chamber? one might have to ream the primer pockets, but you'd only have to do this once.

perhaps remchester brass in x55 would be the perfect fit without sizing down....

[Willbird]

has anyone looked into the base diameters?

I have read where the base of most factory commercial brass is slightly undersized, or at least near the minimum size.

this makes for a sloppy fit, canting the cartridge if the neck fits tight.

necksizing overcomes this a bit, but that assumes the cartridge expanded concentrically.

is it possible to use, say the 6.5x55 brass that is slightly larger, and squeezing that puppy down to fit perfect in the chamber? one might have to ream the primer pockets, but you'd only have to do this once.

perhaps remchester brass in x55 would be the perfect fit without sizing down....

I do not see how the ctg gets canted if the neck fits tight. With a .002 clearance turned neck the rear of the case cannot flop around much. And the solution is when your buying the reamer, have it made to fit the brass. My 22-250 AI reamer cuts a chamber that will NOT accept cases made from 308 (too tight at the base) a factory saami chamber will.

IMHO the older a ctg is the bigger the difference will be between a saami min ctg and a saami maximum chamber. The way tooling works they get the most life if they start with a minimum ctg and a maximum chamber...plus they know they will fit :-). They only design to use the ctg once.

[Tom Myers]

Bump for my drawing edit in post 66 (http://castboolits.gunloads.com/showthread.php?176454-A-new-boolit-barrel&p=1981022&viewfull=1#post1981022).MJ

MJ

A picture is worth a thousand words. I fed the dimensions from your chamber drawing into the Precision software and came up with some images that might help to envision what the end result would be.

Also, if you intend to maintain the 45° step-down at the chamber mouth, the length of the step from a 0.286" dia. down to a 0.259" dia. would be 0.0135" instead of 0.0125".
If you wish to maintain the 0.125" step length, then the angle would need to be changed to 47° 12" 9"
Please forgive me if I am being too presumptous in taking the liberty of copying your image and added the corrections.

http://www.tmtpages.com/LinkSkyImages/forum_images/250_Savage_Mod/250_Savage_Mod_Marlin_Junky.png


http://www.tmtpages.com/LinkSkyImages/forum_images/250_Savage_Mod/250_Savage~Custom~R.C.B.S.png


http://www.tmtpages.com/LinkSkyImages/forum_images/250_Savage_Mod/Untitled-1.png


http://www.tmtpages.com/LinkSkyImages/forum_images/250_Savage_Mod/Untitled-2.png


http://www.tmtpages.com/LinkSkyImages/forum_images/250_Savage_Mod/Untitled-3.png

Hope this helps.

[Willbird]

Boolit design first, then case capacity and form design to make 2400 fps max with slowest powder to be used, then reamer(s), then barrel and dies both made by barrel maker with reamers purchased. That is the preferred order of things. ... felix

I'm sorry Felix one cannot make a sizing die with a chambering reamer :-). Or so Shilen and others say.

[felix]

Will, the dies would have to be hand dies made out of the same barrel material. Actually, the material is a cut-off section of the barrel, and then made with serious "roughing" reamers that cut small, and then honed to spec. Too much work/time for a "production" barrel maker. Back yard BR folks order barrels independently and do the die work. ... felix

[Willbird]

Will, the dies would have to be hand dies made out of the same barrel material. Actually, the material is a cut-off section of the barrel, and then made with serious "roughing" reamers that cut small, and then honed to spec. Too much work/time for a "production" barrel maker. Back yard BR folks order barrels independently and do the die work. ... felix

But Felix :-)...we can spec everything all out so an off the self die (even a custom but still to a spec) will work, the reamer is the "funny" part of the deal due to non saami specs...but when it comes to good reamers, they all cost the same really, 155, mild or wild...little tiny ones like 22 hornet or 300 blackout cheaper.

[felix]

Very excellent, Tom! Looks like MJ is now about ready to do his thing. Might want to make case neck a constant diameter which would make neck turning functional with current straight-line tools. ... felix

[Marlin Junky]

Wow, that's absolutely beautiful Tom. What is the price of that software package and how long did you spend on these drawings? Correct me if I'm wrong but it looks like one could define a chamber reamer for the reamer guy with this software.

Elsewhere on this forum, I decided because of the work required to form the 250's ample body taper from a .308W/.308W derivative cartridge case, I would be using the RCBS 250-3000 Improved with its 28º shoulder as the basic cartridge design.

I would also like to see how 100-117 grain copper patched boolits from Hornady and Sierra fit this chamber.

I have a quick question about your drawing:

Shouldn't freebore1 and freebore2 have the same diameter if there actually is .0573" (.0708" - .0135") of freebore; i.e., isn't freebore defined as a cylinder?

MJ

[Tom Myers]

felix
Very excellent, Tom! Looks like MJ is now about ready to do his thing. Might want to make case neck a constant diameter which would make neck turning functional with current straight-line tools. ... felix
I agree with the concept of a constant neck diameter. The drawing shows the SAAMI cartridge specs as published.



Wow, that's absolutely beautiful Tom. What is the price of that software package and how long did you spend on these drawings? Correct me if I'm wrong but it looks like one could define a chamber reamer for the reamer guy with this software.

Elsewhere on this forum, I decided because of the work required to form the 250's ample body taper from a .308W/.308W derivative cartridge case, I would be using the RCBS 250-3000 Improved with its 28º shoulder as the basic cartridge design.

I would also like to see how 100-117 grain copper patched boolits from Hornady and Sierra fit this chamber.

I have a quick question about your drawing:

Shouldn't freebore1 and freebore2 have the same diameter if there actually is .0573" (.0708" - .0135") of freebore; i.e., isn't freebore defined as a cylinder?

MJ

MJ,
The four software modules used to create the images are incorporated into the Professional Bullet Design package that is offered for commercial designers and fabricators use and the price varies with the modules that are used. If interested, contact me to discuss your needs.

The majority of the time spent is devoted to entering the values of each chamber, cartridge and bulletl variations into the individual databases. Once that fairly simple but time consuming chore is accomplished, the software modules create and save chamber, cartridge and bullet images. The Overlay module retreives the images and provides for precise control of the positioning of each image to produce the final drawing. The final drawing may then be cropped, adjusted or resized to meaningful viewing dimensions.

About the only feature that the chamber and cartridge drawing modules lack is the ability to display shoulder and neck junction radius values. However those values could be hand-written in if necessary. In the next update of the software modules, I hope to have that feature working.

If all data is in the databases, about twenty minutes is required to draw a finished image, but the image and dimensions must be throroughly checked for validity and this takes additional time. Generally, If I am working from Impact impressions or cerrosafe castings, fired cartridges and bullet samples, the whole process takes between four and five hours. to get it right.

Do you have dimension values for the R.C.B.S. 250-3000 Imp. chamber and cartridges? If so, I could enter those into the modules and do another image.
I'll see if I can scale out some images of the Hornady bullets and produce images to overlay on the chamber drawing. Do you have samples to provide dimensions? Length, meplate dia. ogive length, Tangent or Secant ogive, etc.

The freebore in a barrel is just what the name implies - a portion of the barrel, extending beyond the chamber mouth, that is bored free of rifeling. It may consist of a cone, a clyinder and another cone - or a combination. In this instance, The first cone is the step down from chamber mouth diameter and is a cone consisting of a 90° included angle (45° in relation to the bore axis). The remainder of the freebore is another cone that is an extension of the 2° included angle (1° relative to the bore axis) that forms the leade cut into the rifeling.( 90°cone and a 2°cone ) - When I am using the term cone, it is implied that the shape is actually termed as a truncated cone.
If the cone were a cylinder of 0.259" diameter, it would have another short 2° included angle cone on the forward end to make the transition down to the 0.257" groove diameter and then continue on down to the 0.250" bore diameter. ( 90°cone - 0.259" cylinder - 2°cone ).
I prefere a slighly tapered freebore, especially for cast bullet application, as lead shaving is usually eliminated.

[Tom Myers]

I would also like to see how 100-117 grain copper patched boolits from Hornady and Sierra fit this chamber.
MJ

I found some images of the Hornady bullets and scaled them out for dimensions. However, the images were quite small so the scaled linear dimensions could be inaccurate to some degree.

The bullets in the images are positioned so that the 0.257" diameter just touches the beginning of the rifeling in the throat.

In each image, there is a noticible gap between the top of the bullet diameter and the barrel. This is a result of computer round-off error at the scale of 1,000 pixels to the inch. If the image were drawn to a scale of 2,000 pixels per inch, there would be no noticable difference in groove diameter and bullet diameter but the image would just be too large to view in this forum page.

If anyone has some accurate dimensional values, body diameter, nose diameter overall length, base to cannurel[spl] length, cannurel length, please post and I can re-enter the data for more accurate drawings.

http://www.tmtpages.com/LinkSkyImages/forum_images/250_Savage_Mod/250_Savage~Custom~Hornady_2.png

http://www.tmtpages.com/LinkSkyImages/forum_images/250_Savage_Mod/250_Savage~Custom~Hornady_1.png

[Tom Myers]

I found Speer 100 gr and 120 gr images.

http://www.tmtpages.com/LinkSkyImages/forum_images/250_Savage_Mod/Speer.png
http://www.tmtpages.com/LinkSkyImages/forum_images/250_Savage_Mod/250_Savage~Custom~Speer_120.png

[felix]

Keep in mind, MJ, that the the total throat is going to change after so many rounds. Any freebore, cone or cylinder, tends to protect the leade for a longer time. That might, or might not, be to your advantage in terms of a static load, and is therefore unpredictable in practice. The more freebore you install, the less importance is given to the neck length. The idea I suggested is to have zero freebore and have the boolit placed into turned necks which becomes the "freebore" by default. It looks like the 308 case is what you are looking for in terms in making cases with the long neck. Just push back the case neck junction without changing the case slope in the slightest making a 40 grain boiler room. Then extend the sides of the neck slope making the neck a 25 caliber. Neck turning required. Only loads exceeding 40K-45K CUP can benefit a "sharp" shoulder for better headspace control. Also, the sharper the neck slope, the more the minimum pressure is required to be raised to keep that final shape in terms of a primer hit. ... felix

[Marlin Junky]

First of all I gotta say thank you for all the interest.

Right now my issue is with boolit diameter. If freebore1 has a diameter of .259", shouldn't the leading edge of my castings also have a diameter of .259" (or perhaps .2585")? This is the paradigm I use for my '06 that produces the best results (i.e., constant .311" boolit shanks). I seat my .311" boolits in '06 cases such that the leading band, upon closing the bolt, is swaged into the freebore, which is also a cone, that starts about .311" (just after the "step") and tapers to about .3095-.3100" (IIRC) before there is a hint of rifling.

Back to the drawings above, the COL with Sierra and Hornady spire points wouldn't necessarily be limited to 2.68" since the narrower bullets (.257" diameter) would seat into the leade deeper (obviously depending on ogive radius). Since my magazine box is 2.85" or a tad longer, I welcome the added COL with the narrower copper-patchers which will be intended for meat deer at 200+ yards.

MJ