Accuracy When Using Undersized Bullets

H

huntingsgr8

New member
I'm considering reloading for my M91 Finnish Mosin, the barrel slugs at .310-.3105. What I would like to do is load some lighter varmint bullets, but all the varmint bullets I have local access to are .308, I can get .311 bullets too, but those are 174gr soft points. If I reload with .308 varmint bullets can I hope (pray, beg, make a small animal sacrifice)to get MOA? Will a jacketed bullet obturate to the groove diameter like a cast bullet will? Would it shoot more of a spread than a group? Has anyone tried something similar?
 
I am sorry, but this is a stupid idea..

How do you hope to get any accuracy if the bullets are falling out of the cases, or bullets not contacting the groves. Not to mention the blowby you will get.

Get a 308 to load 308 bullets. If you are going to predator hunt in Canada, then get a 243,223, 22-250 or something like it. I would hate to blow out a $100 pelt with a 308. Shoot 10 coyotes and you would pay for any new predator caliber you pick.
 
I know I'm going to get a lot of flak for this, but I can also use .311 FMJs. Yes I know that they can be unreliable, and inhumane, but a bullet in the head or heart will still put them down, I do not make "hope" shots, they should suffice. There's always 203gr MFS soft points, they're bi-metal jacketed, and from what I've seen online they open up very slow, so a broadside shot shouldn't turn a coyote inside out.
 
Try them and see how they work, you might have to order a 308 expander ball for your sizer die.

I shoot a odd German caliber that the bore has been slugged at .260 and I size .264's down to that. A german reloading book that I have excerpts from suggests using .257 bullets.. I tied it.

It works .257 Hornady V-Max in the .260 bore.



 
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Originally Posted By: AWSTry them and see how they work, you might have to order a 308 expander ball for your sizer die.

I shoot a odd German caliber that the bore has been slugged at .260 and I size .264's down to that. A german reloading book that I have excerpts from suggests using .257 bullets.. I tied it.

It works .257 Hornady V-Max in the .260 bore.





Wow! That's pretty good. I wonder at what pressure JHP bullets obturate, I read somewhere that Barnes TSX (a gilding metal bullet) obturate at 45'000 psi. If a a nearly pure copper bullet can obturate at 45'000 psi surely a jacketed bullet must at or below that pressure.
 
Use the Hornady 123gr SST bullet in .310 diameter,they shoot great and to the point of aim with any Mosin so far. They are made for SKS but shoot very well in Mosins. The heavier bullets shoot high like the .311 Sierra Pro Hunter. What powder are you gonna use? 46gr of Varget works well as does 44gr of IMR4895. A lot of places carry the said bullet.
 
Well, I decided on BlC-2, because it's the cheapest powder the guy at the gun shop has at 40$/lb, I wanted to use 4895, but it's about 46$/lb. I will look into the sks bullets, hopefully I can find them locally because flat rate shipping for those would be 13$, on top of the 40$ for them, and with the tax it would be about 60$ just for the bullets.
 
Back to your original question, yes, you can shoot .308" projectiles in your rifle. You will have to use a smaller expander ball, but you are only talking about .001" all the way around, and a human hair is typically .004".

FWIW, the 7.62 X 39 die sets typically have two expander balls; one is specifically for shooting the .308" bullets, and a lot of guys do quite well with them. Just prep your brass first!
 
Setup for Mosin shooting
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Initial test shots @ 50yd
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Final group @ 50yd with 46gr Varget/123gr SST/ WLR primer seated to cannelure.
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I aint the best shot in the world but that is not bad. Mild recoil and would kill a deer easily. If you use the heavy bullets for moose it is easy to lengthen the front sight pin if necessary. The 180gr Sierra Pro Hunter .311 shoots well but hits a foot high @ 100yds. Practice at home with the dippers and scale is a must but dippers are extremely accurate with practice. Rifle is a M39 VKT Finn Mosin with a like new bore. I shot for hours with 5 cases.
 
Wow! Great group. And Thanks again for the advice. I'm going to find out in a few days just what the MFS 203gr can do, got it sighted in (hit about 9 inches high at 60 yards, so I built up the sight with a bit of tape to get it to POA) found a field that 3 bears are hitting nightly, just need landowner permission.
 


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