How do you FIT a boolit or design it for a lever action with a deep throat?

[MBTcustom]

I was recently the honored recipient of a Rossi 92 carbine in 44Mag.
I set about to design a boolit for this rifle and found that perfect fit is impossible.
The throat starts at the case mouth @ .459 and tapers straight to the groove diameter at an angle of 3 degrees, 47 Minutes of angle per side.
What this means is that about .200 from the case mouth to the groove diameter is unsupported in the chamber. Ie, if I had a perfectly flat nosed wadcutter, it would have to stick out of the case .200 just so that the leading edge could touch the rifling.

OK, so I designed a boolit that was .432 in diameter till it touched the rifling .200 from the case mouth, then has a 4 degree 47 minute angle to bore diameter, then about .020 bore rider, then a nice short TC nose about .125 long.
What this equated to was a boolit that protrudes from the brass by .450 with an OAL of 1.720 and I turned said boolit out of tool steel to check fit and function in the rifle.

When single fed into the rifle, this boolit fit's like a glove. Perfecto.
However, it's too blessed long to feed from the magazine tube. Sure looks to me like this rifle will only eat ammo that is 1.575 long and that's probably pushing it.
The problem is that this demands that I jump the boolit to the rifling by about .150 inches. That's one heck of a jump.

So my question is twofold:
1. How is this designed around?
2. How is accuracy achieved jumping a boolit over 1/8" into the rifling?

Any advice is appreciated. Please understand that I am a bolt action guy, and that is probably horribly obvious to those of you who are reading this, so please feel free to line me out.
Thank you!

[DeanWinchester]

Would this work?

Wonder if it'd feed reliably.


http://www.accuratemolds.com/bullet_...=43-270H-D.png

[C. Latch]

Doesn't sound any worse than shooting .38s in a .357........

[MBTcustom]

Would this work?

Wonder if it'd feed reliably.


http://www.accuratemolds.com/bullet_...=43-270H-D.png

It would if the .430 diameter went all the way to the radiused edge!

[MBTcustom]

Doesn't sound any worse than shooting .38s in a .357........

Yeah, unless of course you are doing like I do and shooting 200grain RN boolits in it.

I'm OK with jumping, I just wonder how you design a boolit to jump like that?
Give it wings like a flying squirrel?
LOL!

[BCRider]

Consider that even with the 0.2" jump that it's still FAR less then the jump the bullet makes in a revolver.

Also if your theoretical wad cutter would need to stick out 0.2" then for most bullet shapes that are properly "heavy" for use in a rifle the riding skirts will have engaged at or a little before the point that the heel of the bullet has left the casing mouth. That seems like pretty good support to me. Granted it's not an "engrave upon chambering" like seen in some target rifles. But we're talking about a lever rifle, not a single shot bolt action where the shooter would be willing to live with some tightness in the chambering. So the chamber has to have a little more room in it to allow for round nose bullets.

Speaking of which I just went and checked. The Lee 429-240-2R mold I've got for a full round nose cast with the base of the nose ogive at the same size as the skirt would engage the rifling that much sooner than a SWC shape or a Kieth style.

[MBTcustom]

Consider that even with the 0.2" jump that it's still FAR less then the jump the bullet makes in a revolver.

Also if your theoretical wad cutter would need to stick out 0.2" then for most bullet shapes that are properly "heavy" for use in a rifle the riding skirts will have engaged at or a little before the point that the heel of the bullet has left the casing mouth. That seems like pretty good support to me. Granted it's not an "engrave upon chambering" like seen in some target rifles. But we're talking about a lever rifle, not a single shot bolt action where the shooter would be willing to live with some tightness in the chambering. So the chamber has to have a little more room in it to allow for round nose bullets.

Speaking of which I just went and checked. The Lee 429-240-2R mold I've got for a full round nose cast with the base of the nose ogive at the same size as the skirt would engage the rifling that much sooner than a SWC shape or a Kieth style.

OK, so that design looks like it engraves with a much more acute angle. Is this a design requirement for best accuracy?
Also, that boolit looks like it has only about 50% bearing surface which I would consider "no es bueno" in a bolt gun.
very strange.

[Pb2au]

In reference to your 1.720" OAL target.....
There is a little lee way in the carrier stop you can play with ( please read attack with hacksaw, dull files and a 8" snag grinder to create more room for a longer OAL), but I am not too sure there is 0.145" worth of it. It might be worth some exploratory surgery, but again, I don't remember how much meat is there to play with.
The other challenge after that would be ensuring that the cartridge would transition correctly into the chamber. Rossi was nice enough to bevel the chamber mouth for straight wall cartridges, and there is a little room there for massaging, but not a lot.

[MBTcustom]

In reference to your 1.720" OAL target.....
There is a little lee way in the carrier stop you can play with ( please read attack with hacksaw, dull files and a 8" snag grinder to create more room for a longer OAL), but I am not too sure there is 0.145" worth of it. It might be worth some exploratory surgery, but again, I don't remember how much meat is there to play with.
The other challenge after that would be ensuring that the cartridge would transition correctly into the chamber. Rossi was nice enough to bevel the chamber mouth for straight wall cartridges, and there is a little room there for massaging, but not a lot.

"Attack with dull files and an angle grinder" LOL! Thats funny.
I am very aware of what I can do to improve the problem with my 3700lb magic wands, but im thinking about bullet design only. Bullet design. Not gunsmithing.
Are these rifles accurate? How?
Im going to be shooting this one with an old Ideal RN design and ill see how it works.this rifle is not a target rifle, and I understand that, but I wonder what is the best boolit design for a rifle witb a long throat. What works best when you have to jump?

[Pb2au]

I have one in 45colt, and so far I am hovering around 3 inches at 75 yards. This is with the Lee 255 RNFP boolit kicked with a modest amount of 2400.
The chamber/throat relationship is a bit generous let's say. I hear and understand your agro about the long jump to get the boolit into the rifling.
At least with mine, it seems the rifling is a bit shallow to boot, so the fit (as always) is muy important.
To my shame, I haven't measure the twist rate on mine, but it definitely likes heavier boolits. In a test, I tried Lee's 300 grain RF boolit and the groups fell right into 1.25" at 50 yards. But other than maybe hunting dinosaurs, that boolit is for destroying watermelons here in Ohio.
Another thing to check is the fit of the forearm. Those wacky Brazilians don't waste a lot of time on the fit and finish of the woodwork, and pinching along the forearm is common and can impact your performance.
While you have the forearm off, you will notice the screw that secures the barrel band intercedes a bit to the radi of the barrel. That is a nice way of saying they probably filed a notch in the underside of the barrel to help pass it through. The short story is that is can and will argue with you getting the crazy thing lined back up.
The fix I came up with for a friends rifle was to relieve the center section of the screw and essentially reduce the diameter in the center of the screw. In machine building we called them French screws. (I have no idea why, and the old fellow I apprenticed with never bothered to tell me. He was too busy yelling at me on what a rotten job I was doing scraping in machine ways.....)
Anyway,,,,,
Actually my next plan of attack for this rifle is to
1)utilize 3 F black powder and a softer alloy as a test.
2)and or up my size of boolit, as I think .452" is still leaving too much slop in the throat. Again,,,generous dimensions,,,,,

It sounds like an interesting project Goodsteel, and I plan on staying tuned in here!

[btroj]

Stop thinking of fit as a static thing. Fit changes as the bullet moves, doesn't it? Make a bullet that self centers some in the throat and it will shoot plenty good for that rifle.




Look at that bullet, it is the best shooting bullet in my 45 Colt Marlin. No idea how well it fills the throat, don't care. The nose tapers smoothly into the body so it can find center as long as I get it close.

Fit isn't as simple as making a bullet fill the throat and touch the lands. It is far more than that. It also changes as the bullet moves and obturates. Think about that and the rest is pretty easy.

[GoodOlBoy]

i agree with Btroj as well.

I would also like to throw out that my rossi 45LC old model 92 carbine has no bullet design that can even remotely touch the rifling, and on top of that it has never needed it. a 250-255 grain RNFP BB or PB bullet will shoot 3/4" at 75 yards with iron sights while standing IF I do my part. The only modification I ever made to get it from a 3" group down to that was to replace the rear sight with a marbles semi buckhorn sight. MUCH better sight picture, MUCH faster on target, and MUCH more accurate for ME than that piece of tin that was on it when I got it.

GoodOlBoy

[Tar Heel]

Well....just speculating here....a Rossi lever action for one is not really a precision machined National Bureau of Standards rifle.
As with your bolt action, a little freebore can be a good thing to give the bullet some run-up space. Are you perhaps attempting to get precision and perfection from a rifle designed for "average" work and accuracy? Nothing wrong with that except you may need to change your name to Don Quixote de la Mancha.

[brotherdarrell]

I have a Puma in 45 colt. It shoots the Lee 255 rnfp slightly better than the rcbs 270 saa, which is around an inch at 50 yds. I dont know what the throat looks like and I have never tried to find out. In fact it is the only rifle I have I have never done an impact slug of the throat and I dont imagine I ever will. I would also add that the fired cases have a bulge that would do a glock proud. This is a case of accepting what I have and not questioning it, which is out of character for me.

Darrell

[Motor]

I don't know your difinition of accurate. Are we talking bench rest or what?

There are plenty of very good shooting rifles out there that have a LOT of bullet jump. Ask anyone shooting milsurps like Mosin Nagants. If I loaded my M39 Fin to touch the rifling there wouldn't be any bullet in the case. Yet it will shoot 1" groups with my hand loads.

I think you are over thinking this. Just buy or cast some "normal" boolits and see how it does first.

I'm pretty sure we shot cast 44 special from a Puma 92 44 mag. How much boolit jump is that !

[MBTcustom]

I really apreciate the discussion fellers. Good info.
What is my accuracy standard? Doesn't matter in this case. I want the best I can get from any rifle, and I have always approached that by making an informed scientific decision. Ihave devoted many hours to the study of boolit design as it pertains to bolt guns. My philosophy is:
Match the angles.
.001-.002 oversize
Do not size any more than I have to
Make the GC .001 bigger than the body diameter
Jump .001-.020 to the lands
Use the softest boolit I can get away with.

This lever gun has shot all of that to pieces. It's funny actually. Here I am looking at this rifle and I don't get to use any of my normal tricks LOL!
Heck even the Marlins let my feel the boolit when I close the action! With this gun, the cartridge will be laying in the chamber like a ping pong ball in a piece of PVC pipe. Just hanging there in space. That aint a throat, it's a corral!

Just a different scenario than I am used to.


So, with this gun you just jump to the lands. OK cool. Got it.
How do you decide what sort of nose to put on this baby? I know you want a nice taper so that it guides itself, but what's the ideal scenario? Do you match the lead angle? More acute? More obtuse?
What's you guys opinion on that?

[rpludwig]

suggest you pm forum member NSB on this topic, or perhaps he will chime in...

[MBTcustom]

Thanks, I'll do that!

Hmmmm, we have no member named NSB. Would that be HNSB?
Please advise.
Thank you.

[Nobade]

Tim, take a look at the Ranch Dog 175 designed for the Marlin 357 carbine. Essentially a wadcutter with a very short nose on it. Gets the full diameter part as close to the throat as possible and still allows feeding. So far it's the only 357 boolit I have gotten to shoot very well in rifles using smokeless powder and not paper patched. Something like that scaled up is the ticket. And whatever size fits a fired case well so you don't have to resize your brass as well as get as good a seal as possible. Another thing that goes a long way to helping is granular filler over an appropriate powder charge. It acts like a super gascheck and lets that boolit seal before it gets cut up by gas blowing past it.

-Nobade

[Pb2au]

That aint a throat, it's a corral!

That is a true story....