Mosin Nagant bore diameters

[Namerifrats]

I have 4 Mosins, 2 91/30's and 2 M44's. All have very shiny bores, 2 are mirror like. Haven't slugged any of them, but prob will. Just wondering what you guys that have slugged them are getting as an average. I'm wanting to order a Lee mould, prob 160 or 180 gr double cavity. Thinking of maybe going with a Lee sizing die as well, 311 Diameter. From what I've searched and read, I'm thinking it may be better to go with a 312 Diameter mould. Then I would have the option of sizing down if needed. Any advice is appreciated. Also, Midway seems to be out of 30 caliber gas checks. Any other source for them?

[fgd135]

I think you're going to find MN bore diameters running anywhere from .3075" for some Finnish MN rifles to .314" for some 91/30s and M44 carbines, even newer ones. It all varies and you will definitely have to slug your rifle's bores to find out.
My suggestion is to shoot cast bullets in the .313" or .314" range, the heavier the better--200 grains is about right. Moulds made for the .303 British caliber shoot well in my MN rifles.
Or have two moulds, one that casts out at about .309"-.310" for the tighter bores and one that casts .314" for everything else. I've never had any chambering issues with the larger diameter bullets, regardless of what is written in some reloading manuals...
Have fun~!

[mooman76]

I believe this has been asked before so if you do a search you should find something. If I remember right the bores usually run about .314 or .315 and if you are lucky they may run .312 or .313. The Russian rifles usually run a little bigger than Americam. The SKS runs a little bigger too for 30 caliber and so does the British .303.

[docone31]

I know my Smelly was a little larger than expected.
If you want to avoid some of the frustrations I had, slug the barrel! It is not that hard, and it will save lots of expense, embarassement, and powder.
I also heard they are large. You might have to beagle the mold for the .303 british for that one. It casts at .312, and I needed reliable .314. I went to paper patching and never looked back.
I would go heavy rather than light. Remember, you are going to need .002 over bore to get anything.

[Larry Gibson]

Given shiney unpitted bores the Russians usually run .311 to .314 though I did find one at .316 once. Some M38 Russians had .308 barrels as did some early Finns. The Chinese Type 53s can be from .312 to .316. The Finn M39s run .310 to .311 but some, the Sako's in particular, have smaller bores of .300-.301 with .310-.311 land depth. I'd suggest the Lyman 314299 or the Lee C312-185-R and a sizer of .312 and one of .314. I use the 314299 sized .314 in all my MNs including the tighter Sako M39 and the M91/28 Sniper. The Lee bullet does quite well in both of those but does not fair well in the M91/2 Dragoon or the M44. I have to size Lymand 324470s (160 gr Lovern made for the 8mm) down to .314 to get any cast bullet accuracy out of my Type 53. I also use Norma cases and have not had any chambering problems with the .314 bullets as mentioned in a couple reloading manuals.

The nice thing about both bullets is they will work nicely in the 7.7 Jap, the 7.65 Argentine and the .303 British. The C312-185-R also works very well sized .312 in worn M1903 and M1917 barrels.

Larry Gibson

[beemer]

Not a bit unsual to find one .314 or slightly bigger,mine run .312-.313. I use the Lee C312-185-1R, mine cast at .314. A .314 die is used to crimp the gas check and lube. I would slug the rifles but I bet the larger mould will work best. Lee also makes a .314 boolit sizer.

beemer

[compass will]

Also, Midway seems to be out of 30 caliber gas checks. Any other source for them?

I guess I bought the last box from midway yesterday [smilie=1: sorry.

[Catshooter]

Bores are like women; you have to take their measure to know for sure.

I have an Ishapur Enfield in 308 that is .299 x .307, and a Noisy Magnet that's .317.


Cat

[Ricochet]

My M91/30s, M38 & M44 are all right around .314", and my New England Westinghouse M91 is right on the .312" specified in the production drawings.

[RugerFan]

My current 91/30 (1934 Tula) has a nice shiny .313" bore.

[BorderBrewer]

Here's what mine slugged at:

1943 M91-30 Bore: 0.300 Groove: 0.312
1948 M44 Bore: 0.300 Groove: 0.3125
1943 M38 Bore: 0.304 Groove: 0.313
1942 M39 Bore: 0.2985 Groove: 0.310

BorderBrewer

[Lead melter]

The Lee C312-185-1R shoots well in all the M-N's I have, but the sizing is a different issue. Some shot well at .312", others at .313" or .314" and one will do best with .315-.316".

I have beagled the Lee mold to cast at .314" and size the gas check to the diameter needed. In the case of the boolit need being larger than the boolit cast, I cast at .314", size at .315-.316" and the boolit then seems to "compress" enough going into the rifling that good accuracy results.

The other sizes are sized as needed with factory sized Lee push through sizers, or with the Lee sizer opened up with sandpaper and a brass rod. This is not as hard a job as it may seem, plus is much cheaper than the $30 plus 4-6 weeks wait for a custom Lee.

Grab the Lee mold, give it a whirl, you might like it.

As a side note, I HAD a Lyman 314299 mold that was cut crooked. The boolits shot better than they had a right to since the base was tilted. This may lead to the belief that a heavier boolit would do better in the M-N. This particular mold was the 2nd new Lyman I've had and both were lemons. I vowed never again to buy a Lyman mold. Just my 2 cents, you can make up your own mind.

[Namerifrats]

Good information everybody! I'll try to pick up some small lead sinkers after while and hopefully get the bores slugged this evening. Never slugged a barrel before but have read alot about it. Plastic or rubber mallet, brass or steel rod (end wrapped with electrical tape) and a lubricated soft lead ball. Watched a video on YouTube about it, shows the guy just driving the ball into in muzzle and then back out. Would that be fine? I wouldn't see any since in driving it all the way through since the muzzle is the last spot the bullet passes through.

[Lead melter]

Quote:
Originally Posted by Namerifrats
Also, Midway seems to be out of 30 caliber gas checks. Any other source for them?

Midsouth Shooters Supply, Cabelas usually lists them, Gator gas checks, most other supply houses that deal in casting equipment, and maybe some on Flea-Bay

[verney]

Grafs has one (1) box of .30 gas checks. I will order when they have more...

[Namerifrats]

Slugged the barrels at the muzzle, results were the average.

M44 LAND .301 GROOVE .313
M44 LAND .301 GROOVE .313
91/30 LAND .301 GROOVE .314
91/30 LAND .302 GROOVE .313

Thing that sucks is I would need at least a .313 mould and I don't see that Lee makes one. I don't care for the Lyman or RCBS stuff really. I read about opening up a mold a little, is that hard to do and wouldn't it make the lube grooves too shallow?

[Ohio Rusty]

We do it all the time for muzzleloaders. I put a brass drift punch in the barrel and pound in a piece of lead. Tipping the gun so the brass drift punch hits the lead slug and it moves forward. Someimes it takes two or three tips to get the slug out. If you don't have a long rod to pound the slug out of the bore from the receiver end of a modern rifle, the brass drift punch allowed to drop down bore and push the slug out works also ...
Ohio Rusty ><>

[Namerifrats]

The Lee C312-185-1R shoots well in all the M-N's I have, but the sizing is a different issue. Some shot well at .312", others at .313" or .314" and one will do best with .315-.316".

I have beagled the Lee mold to cast at .314" and size the gas check to the diameter needed. In the case of the boolit need being larger than the boolit cast, I cast at .314", size at .315-.316" and the boolit then seems to "compress" enough going into the rifling that good accuracy results.

The other sizes are sized as needed with factory sized Lee push through sizers, or with the Lee sizer opened up with sandpaper and a brass rod. This is not as hard a job as it may seem, plus is much cheaper than the $30 plus 4-6 weeks wait for a custom Lee.

Grab the Lee mold, give it a whirl, you might like it.

As a side note, I HAD a Lyman 314299 mold that was cut crooked. The boolits shot better than they had a right to since the base was tilted. This may lead to the belief that a heavier boolit would do better in the M-N. This particular mold was the 2nd new Lyman I've had and both were lemons. I vowed never again to buy a Lyman mold. Just my 2 cents, you can make up your own mind.


I was just looking at the very mould you mentioned. I read the article on "Beagling". I guess it could work out for me too. Would the bullets be alright to shoot right out of the mould, or would they need to be rounded in the Lee .314 Sizing Die? Might just have to give it a try.

[Rick N Bama]

You might try to find one of the "Fat" 30 caliber molds form the group buys.

Rick

[docone31]

A Lee Push Thru sizing die will make a great deal of difference. I find, even when I am only lubing and putting on a gas check, any out of round within that diameter gets cleaned up.
IF the rifleing can do the same thing, even better.
Guess you are just going to have to try a few.
The more you try, the closer you get.

[Lead melter]

Namerifrats, PM sent concerning process.

[warf73]

My M44 is Russian produced in 1944 measures .3121"

[Molly]

Good information everybody! I'll try to pick up some small lead sinkers after while and hopefully get the bores slugged this evening. Never slugged a barrel before but have read alot about it. Plastic or rubber mallet, brass or steel rod (end wrapped with electrical tape) and a lubricated soft lead ball. Watched a video on YouTube about it, shows the guy just driving the ball into in muzzle and then back out. Would that be fine? I wouldn't see any since in driving it all the way through since the muzzle is the last spot the bullet passes through.

Let me give you a few suggestions on slugging the bore. First, go to a GOOD welders supply shop and buy a 7.5mm (0.295 inches) brazing or welding rod. The brazing rod will be less abrasive on the bore.

Second, stop by your gun shop and buy a box of 12 gauge 00 or 000 buckshot loads. The 000 measure 0.36" nominal, and the 00 measures 0.33" if my memory serves. They make great slugs for measuring bore diameters.

Now prepare the bore with a squirt of light oil like WD-40, an wipe it dry afterwards. Stand the rifle on it's butt and set a 000 (or 00) buckshot on the muzzle. Tap gently with a block of hard plastic or wood, something like a 6"x2"x4". The shot will pop into the bore with little difficulty.

Now insert the brass rod from the breech end, and knock the ball out, being sure to catch it on a soft cloth to avoid dinging it. Measure, record the diameter, and set it aside.

Repeat with another ball, but this time, use the brass rod to push the ball all the way through the bore. Chances are you will notice spots where the ball pushes easily, and spots that offer more resistance. These are tight and loose spots in the bore, if it's not as uniform as it may seem when you look down it. This will give you a good idea of the quality / uniformity of your barrel. Again, catch the ball on a soft cloth and measure.

Now comes the most informative step: Measure the throat diameter. First cut a dowel off even with the mouth of the case, and insert the case and dowel into the chamber and close the bolt. Then go through the same porcess as measuring the bore all the way through, but this time the ball will be stopped in the throat by the dowel in the case. Bounce the brass or steel rod off of it a few times with some enthusiasm. It isn't necessary to bend the rod, just use its weight to upset the ball. Open the action, removing the case and dowel. Then use the rod to push the upset ball out, again catching it on a towel. It should have a cylindrical section for measurement. This will be the optimum diameter for sizing your cast bullet, or perhaps 0.0005" under that.

Hope this helps.

[beemer]

As stated above my Lee C312-185-1R cast at .314. Sizes will vary from mould to mould but my experience with Lee is that their moulds will be a little bigger than advertised. You need a sizer to crimp the gas check.

beemer

[Namerifrats]

Good info everybody! I placed an order today for the Lee .312 mould, a .314 sizing die, 30 cal and 50 cal gas checks. So hopefully sometime next week I'll cast a few and see how they are straight from the mould. Then I'll look into any modifications I may need to increase diameter