ultimate 30 cal cartridge

[nekshot]

I am in a down time with my hands but I still can think! I have a specific 308 lite weight barrel and I was planning on building a dedicated cast only gun out of it. My question is if 2000 was max speed and this cartridge was only for slow boolits for hunting, would it be better to have a cartridge case full of slow powder or have a small capacity case with small amounts of fast powder? Sound is no thought in this only accuracy with 150 - 180 gr boolits. I have cut off the breech end to where it (a 308 case shortened) has the same capacity as a 7.62x39. I will use a 307 brass for the rim and form it with a long neck to hold all the boolit. The action is already made and is single shot, I want as close to 30-30 pressure as possible. What think ye great minds? It seems like I am headed to another neck surgery so I have of time to think and I want to finish all my projects as soon as I get going again.
The chamber is 308 and it is a matter of how small I go with the case capacity and yes it will be a wildcat for sure.
thanks for thoughts, nekshot

[Bigslug]

You might do some research on the .30BR for notions as to how long to make the case body. There's also the Ackley version of the .30-30, though that's probably getting close to .308Win specs. The 7.62x39 was the parent for the 6BR case. Given that its standard loading is 125 grains at about 2300-2400, capacity might be just about perfect for 2000 with your heavier slugs - but I would get rid of the body taper. No need for it in a non-autoloader.

[45-70 Chevroner]

I am quite a ways out of my league here when it comes to building cartridge rifles. I do know that the 30 Heret with cast boolits shoots real well at 2000 fps.. The cases are a pain to make but so are almost all wildcats.

[runfiverun]

if you want 30-30 type pressures you need 30-30 type case size.
the 300 savage has the same case capacity only in a different shape.
pull the primer punch from a 300 savage die set and push a 308 case in there fully.
you'll see what you want come back out of the die.
you can then adjust the neck length from there.

or you could do the 308 X 1.5 long neck case which requires a custom die set last I looked, or for you to modify your existing die.

[scb]

The 7.62x39 was the parent for the 6BR case.
No. The 7.62x39 is the parent cartridge of the 6mm PPC. The 6mm BR has the same rim dimension as a 308 case.

[nekshot]

my biggest question is have you guys found a small capacity case (such as 7.62x39) to be more accurate full of slow powder than fast powder in little amounts. I prefer to work more with full cases because I sometimes get screwy in what I do. I only want 1600-1800 fps, but I prefer best accuracy if possible. My limited work with my bolt 7.62x39 is very accurate with 180ish grain boolits and 335, 4895 and blc2. I want to try 4350 in a full case because I usually get good groubs with that in smaller cases.

[RickinTN]

I'm not very familiar with the 30br, but I am very familiar with the 6mmbr. I'm thinking you could look closely at the 30br for what you want to do. From my experience and understanding you have to try very hard with anything on the br case to get it not to shoot well. If the neck is long enough for your needs I'm thinking the 30br should be about perfect.
Good luck with your project,
Rick

[detox]

No need to get exotic. Just build a standard 30-30 and cut chamber to minimum sammi specs. I like the fast powder idea best.

[Hamish]

Hard to argue with the above photo.

30 Bellm?

http://www.bellmtcs.com/store/index.php?cid=106

30BR?

http://www.6mmbr.com/30br.html

I like the idea of a very long neck, I thought the same thing dreaming about making an 8BR with 8mm Max boolit and shortened mil-surp. cases for an AR application.

[nekshot]

excess650, that is almost the same groub as mine would do at 80 yards with 19-20 gr of the powders I listed. I never thought of the 30br but that gives me confidence keep going forward. Right now my case measures from bottom to shoulder 1.140 and a long neck. I simply want to shoot with case full of powder and great accuracy and keep the pressure down.

[Harter66]

The x 3 9 will hold 25gr IMR 4350 to the neck ''loose''.
The 6 . 8 Rem ,1.6 case length rimless 30-30 ,holds 29gr.

FWIW

[nekshot]

303 brit is what I am using right now. I think it would be ok.

[detox]

He already has the remnants of a .308 chamber and the diameter at the shoulder is larger than the base of a 30-30. He might be able to get by with 30-40 Krag or 303 British cases as a basis IF the rear of the chamber in the barrel stub doesn't exceed ~.460".
OK...cut off the whole chamber. The 30-30 has a very long neck much like the old target round 222 Remington.

[detox]

On second thought, it would be easier to use a Remington bolt that is allready cut for either the .223 or .308 style rim.

[Larry Gibson]

nekshot

My question is if 2000 was max speed and this cartridge was only for slow boolits for hunting, would it be better to have a cartridge case full of slow powder or have a small capacity case with small amounts of fast powder? Sound is no thought in this only accuracy with 150 - 180 gr boolits.

Best will be with the slowest powder that ignites easily and burns efficiently under the 150 - 180 gr bullets (probably looking at 2 different powders with that bullet weight range in that case) that will give 100 % load density. I base that on my 30+ year experience with my own 308 CBC (below - left cartridge) based on a shortened .308W case with a long '06 length neck, the 30-30 and the 7.62x39 in a bolt action rifle.

Larry Gibson

[nekshot]

Here is what I'm working towards. 308 case shortened beside RCBS 180.
72131

[nekshot]

thanks Larry, I was hoping you would give your thoughts on this. All I need to do is cut a 308 die to chamber length, shorten a 307 case and should be done I hope. Open the existing throat to accomodate long neck.

[OnHoPr]

Something like a heavy cased 303 savage.

[Cane_man]

i picked up a Lyman 311291 170gr not too long ago, where does it stack up with the other popular 30 cal molds?

[9.3X62AL]

My turn to be The Designated Wet Blanket. If I was to find myself with a good single-shot action and a good 30-caliber barrel I wanted to make into the Ultimate 30 Caliber Cast Boolit Rifle.......I would chamber it in 30-30 WCF and call it good. I suspect that in a stronger action than a Win 94 or Marlin 336, getting 2000 FPS from 200 grain or even 220 grain boolits would not be a huge strain. The 30-30 case isn't mondo-strong, but it is solid-head and if the chamber was cut to minimum SAAMI I'm sure brass life would be reasonable. This is not so much derived from wanting to be "that guy" or a "killjoy", wildcatters "gotta be" too. :) I just think the 30-30 WCF is the single-best 30 caliber factory cartridge ever birthed for the cast boolit.

[9.3X62AL]

i picked up a Lyman 311291 170gr not too long ago, where does it stack up with the other popular 30 cal molds?

Top shelf, in my view. I've surely fired a whole lot of those castings from 30-30 and 30-06 over the years. Thousands, literally.

[captaint]

scb - you are correct about brass (6BR) lineage. The parent case for the 22BR, 6 & 7BR, 30BR is the Rem BR brass. Just a .308 case with zero neck down. With a small primer pocket, of course. Great rounds, those Rem BR's. Mike

[Cane_man]

9.3, thanks! looking to reload for it with my .308

Ridgecrest... I'm in Bako... small world

[9.3X62AL]

Cane Man, it is indeed a small world! We have a fairly decent 600 yard rifle venue out here, so if you can take the heat get on out this way.

[Idaho Sharpshooter]

Look at the cast bullet assn's match reports. The 30BR O-W-N-S all of the records outside of production class. I would love to see Savage build them in the heavy rifle.

[Bigslug]

No. The 7.62x39 is the parent cartridge of the 6mm PPC. The 6mm BR has the same rim dimension as a 308 case.

You right. Me senile. Carry on.

[Outpost75]

If anyone has a recipe which makes paper targets taste good I MIGHT go with one of those few fangled modern calibers, but what's wrong with a plain ole .30-30, .30-40 Krag or .30-'06?722187221972220

[9.3X62AL]

I hear ya, 75. All three calibers have been tipping deer over for more than a century. As foreign as it may seem........there are people here and elsewhere that don't hunt, and limit their shooting to paper targets, iron chickens, or clay discs. Now you and I, we do all of that--but when we do, it is to prepare for the hunt or defensive action. These other folks just leave it at that. Strange, I know. I'm not one to spoil anyone's fun, though.

Reminds me a lot of the folks who fish for Humboldt squid off the California coast, then keep the slimy things. To eat, allegedly. Even after you tenderize it with a roofing hatchet, it still has the flavor and succulence of Michelin truck tire sidewall. Calimari By Goodyear.

[nekshot]

Take a sedative fellas, I am not trying to come up with anything new, I have a feather weight mod 70 barrel chambered in 308 I am simply wanting to use up. I also am bored of the traditional calibers and wanting to do something that I think might work very well. If it doesn't work I simply will be more educated than now and can go back to the old boring stuff! I love challenges and as a former bench rest shooter for a long time, I am never happy unless my guns groub at least 1moa at 100 yards and i have a vision of what this gun might produce.

[Marlin Junky]

Take a sedative fellas, I am not trying to come up with anything new, I have a feather weight mod 70 barrel chambered in 308 I am simply wanting to use up. I also am bored of the traditional calibers and wanting to do something that I think might work very well. If it doesn't work I simply will be more educated than now and can go back to the old boring stuff! I love challenges and as a former bench rest shooter for a long time, I am never happy unless my guns groub at least 1moa at 100 yards and i have a vision of what this gun might produce.

I'm sort of at the same juncture with my .30's, the distinction is I want a rimless case on a short bolt action without a lot of cost. Been thinking lately of necking down virgin '06 brass (which will be made until they confiscate our powder burners) in a .308W FL die and trimming to 2.16-2.17". The goal is to get two lube grooves on a 160-180 grain boolit covered by the resulting case neck which would also probably have thicker neck walls for closer tolerances. Naturally, the .308W reamer would need to be tweaked in the neck/throat area.

I'm not sure how this would differ from Larry's cartridge since I don't know exactly what he means by "shortened".

MJ

[nekshot]

Marlin Junky I share your thoughts. I heard Larry talk of that cartridge application before and I forget his details but I was intriqued by it. Originally I was taking 308 brass thru 300 sav die for the long neck which I am convinced is one of the ingrediants to tight groubs. I then decided to get the case capacity smaller for slower powders to fill it full. I am totally set on 2000 and under speed. I have had amazing tight groubs with fast powders but the speed is always lower than I feel confident to hunt with. Slower powders have given me enough speed and the groubs generally stay together better than fast powders. I think some of this might be the disruption to the boolit from muzzle blast. Yes I can shoot super tight at 50 yards but 100 is another story. So I am searching for an answer.

[johntkd]

what it sounds like to me is your looking for an old Cartridge made by remington called a 32 remington, I used to have one in a pump action, no its not a 32 wspl it was its own round using an auto loading ( rimless) case, of which i had to make my own cases for cutting down and necking 308 cases its easily loaded in a 32 win spl loading die set and they have a few loads listed for it I am sure if you find some very old loading books from the 30s and 40 you will find similar in 30 cal....the 32 rem was discontinued in the 40s as were lots of calibers and rounds

[Marlin Junky]

Marlin Junky I share your thoughts. I heard Larry talk of that cartridge application before and I forget his details but I was intriqued by it. Originally I was taking 308 brass thru 300 sav die for the long neck which I am convinced is one of the ingrediants to tight groubs. I then decided to get the case capacity smaller for slower powders to fill it full. I am totally set on 2000 and under speed. I have had amazing tight groubs with fast powders but the speed is always lower than I feel confident to hunt with.

.308W brass run through a .300S FL die crossed my mind too but one is only gaining 1/16" in neck length and the force required to re-tapper .308W to 300S made the task unsuitable for my purposes. If I just wanted to pick a .30 caliber cartridge for a single shot, I wouldn't restrict myself to rimmed cartridges and would probably select the 30BR.


Slower powders have given me enough speed and the groubs generally stay together better than fast powders.

Makes perfect sense to me... Re7 is a very good powder for the 1900-2000fps velocity level... as is 4198 and others.


Yes I can shoot super tight at 50 yards but 100 is another story. So I am searching for an answer.

Could be a stability issue... make sure you use enough twist when reducing the velocity of a cartridge from its original design.

MJ

[Marlin Junky]

what it sounds like to me is your looking for an old Cartridge made by remington called a 32 remington, I used to have one in a pump action, no its not a 32 wspl it was its own round using an auto loading ( rimless) case, of which i had to make my own cases for cutting down and necking 308 cases its easily loaded in a 32 win spl loading die set and they have a few loads listed for it I am sure if you find some very old loading books from the 30s and 40 you will find similar in 30 cal....the 32 rem was discontinued in the 40s as were lots of calibers and rounds

Actually, the .30 Remington would be more appropriate for a .30 caliber barrel :bigsmyl2: and if Remington would revive it, a lot of boolit casters would be happy... assuming the brass was quality stuff, naturally.

MJ

BTW, the process of making your .32 Remington cases was probably turning the rims on 30-30 cases and necking up to accept .321" bullets. I seriously doubt you (or whoever actually made the 32R cases) started with the .308 (AKA .308 Winchester).

[johntkd]

yep 308 cases are what I used and also what a custom ammunition maker in Ossineke MI used thats sells to many gun shops ( or used to) I had a die made at work after obtaining some of his ammo first to resize the cases after they were cut it squeezed from 3 sides against a pin that fit into casing, then ran thru resizer in die set

[Marlin Junky]

yep 308 cases are what I used and also what a custom ammunition maker in Ossineke MI used thats sells to many gun shops ( or used to) I had a die made at work after obtaining some of his ammo first to resize the cases after they were cut it squeezed from 3 sides against a pin that fit into casing, then ran thru resizer in die set

I'd sure like to see the dies and press that reduced the .308 cases heads .05". Did the flash holes need to be drilled out?

MJ

[Larry Gibson]

what's wrong with a plain ole .30-30, .30-40 Krag or .30-'06?

What's "wrong" with them (for me) is that with rare exceptions the 30-30 and 30-40 are not useable in most bolt actions. The 30-30 in a M94 rifle (24 - 26" barrel) with a 12" twist can easily push a 200 gr cast to 2200 fps and a 170 gr cast to 2300+ fps with hunting accuracy using the right powder. The 30-30 also lacks case capacity for slower powders to boost velocities above that and retain accuracy. Additional problems with the 30-40 and the '06 is they have 10" twist barrels in factory persuasion. The 30-40 may have sufficient powder capacity and the '06 certainly does but the 10" twist is the real limiting factor to consistent high velocities.

"Shortened" as with the .308 CBC means the shoulder is set back so the case capacity is 95% of the 300 Savage with an '06 length neck and the case oal at 2.000"

My next .30 cal CBC will be a shortened '06 case with the shoulder set back so the neck is '06 length and the case is 57mm oal. I use standard FL, NS and seater shortened '06 dies to simplify case forming from '06 brass. A standard '06 match reamer with a tight neck will be used to simply short chamber the barrel using the shortened formed cases to headspace with a slight crush fit. I call it the 30x57. Nothing really "custom" there as standard dies, reamer and brass are used. The '06 taper means it will feed through most any bolt action (Mausers, M70s, M700s, Savage 110/112s, etc.) without any action/feed rail modifications. The barrel will be 28 - 30" Light Palma contour with 4 lands and grooves and a 16" twist. Looking at pushing the LBT 150, the 311466 or the 311465 to 2800- 3000 fps with accuracy while remaining under the RPM threshold. If the 30x57 doesn't have the case capacity using AA4350, RL19, H4831SC or RL22 to achieve that velocity with accuracy while keeping the psi down under 42,000 the I can easily ream the chamber deeper with the same '06 reamer, back out the dies and form longer cases with more case capacity. That will allow more powder and/or reduce the psi while maintaining velocity. It can be continually reamed out until a standard '06 chamber is had if that is needed.

That's the plan anyway..........

Larry Gibson

[Cane_man]

just curious for the .308 how far off the lands will you set the boolit and will use a Lyman M die to expand the neck so it doesn't squeeze down the boolit diameter... thanks

[Fluxed]

I don't think you'll have much meat at the breech with a Featherweight contour barrel, but maybe you have that part figured out already. If you have room, make it a .30-30. You did say a single shot action, right?

[johntkd]

if I still had the dies I would post them here they went with the gun when i sold it,no i never had to do anything with the flash holes but you brought up a good point i may have had some issues using them in colder weather by not doing so, the rims were cut down by a friend with his own machine shop I sent over 250 cases to be turned down and got them back the next night so couldnt have been to big a deal for him, not sure if he used a lathe or his cnc machine,he was the same die maker that made my resizing dies and also eventually bought the rifle from me lol I woukld ask him for the pictures but he passed away about 10 years ago and his family sold almost all his stuff....


I'd sure like to see the dies and press that reduced the .308 cases heads .05". Did the flash holes need to be drilled out?

MJ

[Larry Gibson]

just curious for the .308 how far off the lands will you set the boolit and will use a Lyman M die to expand the neck so it doesn't squeeze down the boolit diameter... thanks

Since I mostly use .311 sized cast bullets I use a .31 M die. I seat so the front of the driving band is slightly engraved by the leade.

Larry Gibson

[HARRYMPOPE]

30 BR there is no other answer.it holds all the records in cast bullet accuracy for over 20 years(except in production class).Good brass(lapua or Norma),easy to form and a standard casehead for you bolt face.its the 6PPC of serious cast bullet competitors.

[nekshot]

Larry, after you explained the rpm deal some time ago I got thinking about this barrel and fermenting ideas took over. Keep us informed on your project.
Fluxed, no fun in that I already have a half a dozen 30-30's

[rintinglen]

30 TC? 30 Marlin? I had seriously contemplated building a SS using one with a 1-12 twist for a strictly target gun. An Aquaintance had an action that he had made for a 30-40 project that had died still born and was interested in selling. The deal died when it was pointed out that would place him in violation of federal firearms manufacturing laws.

[robroy]

My next .30 cal CBC will be a shortened '06 case with the shoulder set back so the neck is '06 length and the case is 57mm oal. I use standard FL, NS and seater shortened '06 dies to simplify case forming from '06 brass. A standard '06 match reamer with a tight neck will be used to simply short chamber the barrel using the shortened formed cases to headspace with a slight crush fit. I call it the 30x57.
I was wondering about the head size of this proposed cartridge being a bit smaller than seemed possible given the taper of the 30-06, or most any bottleneck factory round. After measuring a factory round and seeing that it's only a matter of .002 and maybe a few tenths I'm more sanguine about the idea although still wondering about how much the case head will be sized and how much force needs to be applied.

Perhaps a discussion best left for another thread or a PM. Didn't mean to hijack.

[Marlin Junky]

Anyone have a 30x47 drawing? I've heard it was/is a good BR cartridge (so reamers should be available) and it sounds like it might be easily made from .308W brass. Sounds like it should also work well in a short bolt action.

MJ

[Larry Gibson]

I was wondering about the head size of this proposed cartridge being a bit smaller than seemed possible given the taper of the 30-06, or most any bottleneck factory round. After measuring a factory round and seeing that it's only a matter of .002 and maybe a few tenths I'm more sanguine about the idea although still wondering about how much the case head will be sized and how much force needs to be applied.

Perhaps a discussion best left for another thread or a PM. Didn't mean to hijack.

Actually shortening the '06 standard FL die and forming the case does not swage the case head down at all. A standard FL dies does not size down to original cartridge specifications. Some SB FL dies will but not a standard one. The taper of the '06 chamber reamer also has +/- dimensions since the standard reamer is used to short chamber the barrel the formed cartridge slips into the chamber because it is formed by the front 3/4s of the FL die.

Photo shows 30x57 on left, 8x57 in the middle and a standard '06 on the right. Also shows the bottom of the shortened '06 FL die used to form the 30x57 case.

Larry Gibson

[ATTACH=CONFIG]72391[/ATTACH ]

[Marlin Junky]

Photo shows 30x57 on left, 8x57 in the middle and a standard '06 on the right. Also shows the bottom of the shortened '06 FL die used to form the 30x57 case.

Larry,

That's pretty cool. Did the pictured 30x57 cartridge case start out as a 8x57 or 30-'06?

I'd like to reduced the length just a bit more to 54-55mm so the round loaded with 180-190ish grain boolits will function through a short action. Unfortunately, that would require a custom reamer, which is the reason I'm curious about the even shorter 30x47, mention above.

MJ

[Larry Gibson]

MJ

The case was formed from '06 cases which also allow for thicker formed necks which are better for neck turning to be a slip fit in the "tight neck" of the match chamber.

The 30x57 will fit very nicely in a 3" long magazined Mauser (SRs and "medium" M98s). Might be able to shorten it another .2" so it will fit a new commercial "medium" mag without swaging the head. Would have to try it? If it does then it would require a custon reamer; a standard '06 reamer and standard '06 dies (shortened) would work as well.

Larry Gibson

[Marlin Junky]

Larry,

So you're saying that the 57mm long version can be created by "holding back" a standard '06 reamer by 6mm?

Thanks,
MJ

[Larry Gibson]

Yes, it's called "short chambering".

Larry Gibson

[9.3X62AL]

A sedative, eh? I have 6 in the fridge, care to join me for one? :)

[mpmarty]

Larry, why not neck up a 7x57?

[Larry Gibson]

Larry, why not neck up a 7x57?

That would need special dies = $s, it would necitate a special custom reamer = $s, it would negate the ability to ream the chamber deeper to get more case capacity (with the 30x57 I can go all the way to the original '06 with the same reamer and dies) and the necks would be very thin with not much to turn to fit even a "tight" neck chamber.

Larry Gibson

[Andrew Mason]

what about a .30 remington AR?

[Marlin Junky]

Yes, it's called "short chambering".

Larry Gibson

Larry,

Yeah, I'm familiar with the term... but not by as much as 1/4".

I need to look into this a bit deeper... not sure if it'll work in a M77 short action.

MJ

[Larry Gibson]

MJ

If the M77 mag is set up for modern cartridges with less taper might be better to look at my original CBC based on the .308W. It will fit any mag with an oal of 2.8"

Larry Gibson

[Larry Gibson]

what about a .30 remington AR?

For my quest of 2600 - 3000 fps the neck is to short and the case capacity too small.

Larry Gibson

[Marlin Junky]

MJ

If the M77 mag is set up for modern cartridges with less taper might be better to look at my original CBC based on the .308W. It will fit any mag with an oal of 2.8"

Larry Gibson

Larry,

Please tell us about the 308 CBC. I just performed a search for threads with 308 CBC in the title and it came up goose eggs.

Does it use .308W or 8x57 brass?

Thank you,
MJ

[dtknowles]

72666

I think this would be an excellent cast bullet cartridge. Very similar to what Larry described only maybe a bit shorter. It has the capacity of the 30-30 that is next to it with the same length neck but in a short fat rimless case with minimum taper.

Tim

[Larry Gibson]

MJ

My 308 CBC is my own design I came up with back in the ‘70s. I use US M80 cases (7.62 NATO) to have thicker brass in the neck area for neck turning. It also uses 7.62 NATO brass because I had so many. I can use .308W cases but the necks will be thinner and case capacity larger.

The idea back then, developed over several years, was that the most accurate cast bullet cartridge would give 100% load density with a medium burning powder. The 30-30 was very efficient at 100% load density with 170 – 180 gr cast at 2200 +/- fps out of a M94 rifle with 24” barrel. I wanted to basically duplicate the 30-40 milsurp velocity with 210 – 220 gr cast bullets in a rimless case (for feeding through a bolt action Mauser) that had 100% load density with 4895 also (because I had a lot of it) at 2200 fps. I also wanted the case to have the longer neck of the 30-30 and ’06 to keep the GC and lube grooves in the case neck. Back then all the published experts said the 311284 was just the ticket and a 2 groove 'A3 barrel was just the cat's meow for that cast bullet. I had a new (still in wrapper & cosmoline) and a SR Mauser action for the project so I was heavily watching and reading all about the “inherent accuracy” of the short squat cartridges.

Using a Powley Computer to determine how much case capacity in water a case would need to have to drive a 220 gr bullet at 2200 fps with 4895 I shortened a .308W FL die and began to set the shoulder back Of WCC 7.62 cases until that much water came just to the junction of the case neck and case shoulder. The case neck was then trimmed back to max ’06 length. Turned out the case oal was exactly 2.00”. Seemed like a good plan at the time and I had the chamber cut off the barrel had it installed on the Mauser action. I explained earlier the chambering method.

When it was done I thought I had the “perfect” cast bullet rifle/cartridge. In working up loads I found several things wrong;

1st case capacity was still too large for 4895 as I hit 2200 fps (yes I had an Oehler chronograph back then) at about 80% load density. Seems none of the literary “experts” I read mentioned that cast bullets will give a higher velocity than an equal weight jacketed bullet with a given powder charge of the same powder. Thus I switched to H4831 and and a couple other slow burners and hit 2200 fps at 100% load density. Sounds good right? Well it wasn’t…….accuracy sucked above 1900 – 2000 fps regardless of the powder used.

2nd problem was the scraper groove in a 311284 is a weak point. When accelerated hard the long heavy nose sets back unevenly, even in the broad lands of the 2 groove barrel. I tried different alloys and even went to heat treating and WQing yet accuracy still went south above 1900 – 2000 fps. I switched to 311299 which doesn’t have the scraper groove and managed to hold accuracy (sub 2 moa with 10 shot groups) up to 2050 – 2100 fps. Above that accuracy suffered very quickly.

I was at a loss for numerous years with the 308 CBC rifle languishing in the back of the gun cabinet with little use as it was really no better than any standard ’06. I could get 2200 fps with 2 moa accuracy out of the M94 30-30 with 311291s and 311041s and the same 2 moa accuracy at 2200 fps with the 311299 out of a M70 .308W. . I just couldn’t understand why the 308 CBC wouldn’t do the same. When I queried the “experts” they all said it was balancing the bullet hardness to the psi, the bullet alloy, lube, sizing, powder….yadda, yadda, what we still hear about these days……..

As the years went by and I shot more and more with the .308 CBC trying all the suggestions to not avail I was at a loss. Then I read a question and answer in the American Rifleman that led me to the answer…..Question; why can I get excellent accuracy with a 311359 at 40, 000 psi from my M1 Carbine but when I load the same bullet in my ’06 to the same 40,000 psi the accuracy is nonexistent? Answer; because at 40,000 psi in the ’06 the velocity is a lot higher.

I wasn’t sure of the velocity of that ’06 load but that answer tied in with another observation made by another gun writer about the adverse effect of too much RPM on unbalanced bullets. That got me to thinking. What was the difference between the M1 Carbine (I had a couple) and shot the same 311359 and knew I could shoot it at 1900 fps with excellent velocity? I also knew that same 311359 shot very accurately in my own ’06 up to 1900 fps and in the M70 .308W up to 2200 fps before accuracy went south. It did not appear the .308W and ’06 loads had anywhere near the psi as the .30 Carbine load. Yet the M94 and the M70 would shoot the same bullets 200+ fps faster so what was the difference?

I computed the RPM in the 10” twist ’06 and the 10” twist 308 CBC with a velocity of 1900 fps and the RPM of the M94 and the M70 at 2200 fps and you know what? They were very close to the same RPM!!! That got me to testing numerous other cartridges with different twists and that’s how I developed the RPM threshold. Not going to go into that but suffice to say it is real.

So with the 308 CBC chambered in that 2 groove ‘A3 barrel with 10” twist it is no better than the standard ’06 or .308W in 10” twist barrels. Knowing what I know now about RPM and cast bullets if I had chambered it in a 12” twist barrel. That’s the twist the M94 and M70 had and is the reason they shot well at 2200 fps and the 10” twist barreled 308 CBC shot well up to 1900 – 2000 fps. If I could do it again knowing what I know now the 308 CBC would have a 12” twist and it would shoot the 311299 with good accuracy upwards of the original goal of 2200 fps…….we live an learn………

Larry Gibson

[Marlin Junky]

Thank you for the story Larry; however, I don't just want to shoot cast boolits from it. I would also be shooting 150-165 grain copper patch at deer sized game on the prairie. And yes, I would go with a 22", 1:12 twist barrel. If I wanted to shoot a 180 grain copper patch, I'd use the '06 case and a 24" barrel.

MJ

[Larry Gibson]

MJ

A 12" twist should serve you well.

Larry Gibson

[Marlin Junky]

BTW Larry,

What is the procedure for grinding the base of reloading dies in order to size a shorter cartridge based on the '06 or 308W case? Can any gunsmith with a machine lathe do it?

MJ

[Larry Gibson]

Any gunsmith or machinist can do it. I chuck the die in my lathe. Of course the decapping assembly is removed and you've computed how much to take off the die. If the gunsmith has a good carbide flat faced cutter he could cut through the hardening but I prefer not to.

I use a flat grinding wheel oin a Dremel Tool. With lathe turning the die in reverse (clockwise) I put the flat of the grinding wheel flat (Dremel running) on one side of the die bottom and grind off the hardened surface. The lathe turning keeps the grind even all the way around the bottom of the die. The lathe is put back turning counter clock wise. The with the flat cutting edge of a right cutting tool bit it is easy to face off the die the amount calculated. The outside edge is slightly beveled and the inside is beveled and polished smooth with Cratex polishing wheels used in the Dremel tool with the lathe once again in reverse. The die is then cleaned extremely well as you want the crinding debri completely removed from the die. The decapping assembly is put back in and re-adjusted for the shorter length. The Seating die can be shortend the same way as well as a NS die.

That's it, easy to do.

Larry Gibson

[Marlin Junky]

Larry,

It looks like the inside length of my M77 magazine box is approx. 2.88" so there's really not enough room for a 2.24" long .30 caliber cartridge case ... especially if ammo loaded with 165 grain Sierra/Hornady/Speer bullets is on the menu. What do you suppose the outcome of running once (or multiple) fired 30-'06 brass through a 308W die would be? I'd probably trim to 2.115" and spec a 2.125" maximum case length for the reamer. That'll yield an additional 1/10" long neck beyond SAAMI 308W.

MJ

[Larry Gibson]

That would be basically the .308W with the '06 length neck. It would be good for the action you have. There are standard .308W reamers that do not have neck as part of the reamer. A neck reamer could then finsh ream the neck to the legth you want. Most of those are tight anyway so the formed case necks could be turned to fit. With a 26" barrel and 14" twist you'd get excellent accuracy 2500+ fps with the likes of a 311466 or the 150 gr LBT. With a 22" barrel you could push 2400+ fps with cast. Of course you can push faster but my own experience with the .308W with 14" twist shows you still need the slower burning powders Like RL19, H4831SC and AA4350 for best accuracy at that velocity. The .308W is capcities out at that velocity level with those powders using my 311466 cast. I'm running 2600 - 2650+ with my rifle but it has a 27 1/2" barrel.

With jacketed it would be capable of .308W velocities (because it basically still is one) with upwards of 165 gr bullets for the deer sized game you mention.

Larry Gibson

[Marlin Junky]

Larry,

2400 fps would definitely extend my varmint nailing ability as long as 1MOA or less can be maintained. Obviously, barrel quality will play a role.


There are standard .308W reamers that do not have neck as part of the reamer. A neck reamer could then finsh ream the neck to the legth you want. Most of those are tight anyway so the formed case necks could be turned to fit.

Thank's for that bit of info... I don't have any practical experience with custom chambers. I'm wondering though, what's the likelihood the gunsmith doesn't align the two reamers perfectly?

BTW, my goal is an accurate bolt action ranch rifle that's handy and durable... 26" barrels are out of the question.

MJ

P.S. I guess we're still on topic; however, I apologize if I'm hoggin' this thread... I promise it won't wander to other calibers. :bigsmyl2: