Moisin Bore Mikes .317"

[centershot]

And therein lies the problem. 303 boolits are undersized, 8mm's are oversize. My 303 mould drops at .312" and 8mm is .323. Siz down the 8mm's by .005"??? Seems like a lot............:-|

[JoeJames]

I sure ain't an expert, but from I have read the standard is .002" more than groove size; so I would think you'd just be sizing it down by .004 rather than .005" right?

[kaiser]

There are some companies that market .318 diameter bullets for the older "S" bore 8mm rifles that should work (or make resizing easy). Hawk is one company that produces this diameter and usually have them in stock; there are also cast bullet molds in that size. (I have a "drilling" that uses .318 diameter bullets in a cartridge called a 8X57JR.) Another possibility to reduce the amount of resizing, is using .32 Special round nose 170gr bullets made by Remington that mike out at .320 diameter.

[RU shooter]

You can indeed size down a 8mm bullet like the Lee RN but first make sure you measure the case neck ID of a fired full power load and see what ya got . You may or may not be able to load a bullet big and still have clearance in the chamber neck . If you can safetly you'll need to use the proper neck expanding mandrel if not your brass will just size that fat bullet back down as you seat it

[lar45]

NOE has a wide range of push through bullet sizers and neck expanding tools as well.
My 9.3x57 Mauser has a .369" groove diameter, so I took some Speer .375" 235s and ran them through a .368" sizer so they pop out the other side at .369" Use a good strong press and lots of imperial sizing die wax. I polished the inside of my sizer until it was like a mirror and sizing went much smoother. It may help to take a Qtip and pre lube the inside of the sizer. Screw the sizer in until the bullet just pops out the other side, so you are using the top part of the stroke with the most leverage.
For cast boolits, lube them first then size. The lube will help to keep the lube grooves from being wiped out.

My Mosin's have 4 groove barrels. On one side they measure .312", the other size measures .314".
Does yours measure .317" on both sides?

[northmn]

Was it a carbine. I had one that miked out at 317 also. I sold it, but it was a challenge to get bullets of that diameter. Also it was not worth it to me.

DEP

[centershot]

Yes this is an M-44 carbine. I only load cast boolits for it though I have about 400 rounds of service ammo for it. I was really surprised this bore is so large!

[truckjohn]

That's pretty typical for an old war horse...

It's extremely common on these to have a generous land size with a tight chamber neck.

The NEXT step now is for you to check some of your once-fired brass to find out what size NECK your chamber has. "Typical" MN's generally can take 0.313"-0.314" bullets before you need to neck turn brass but no bigger... But I have several that even need case necks turned to run 0.314" bullets.

Do this BEFORE you go any further down the road of buying molds.... It will save you a lot of grief.

Then - I would load up ONE 0.317" bullet into an empty cartridge and verify it will chamber... ZERO of my Mosins will chamber a 0.317" bullet due to the chamber neck.. Zero! You might get lucky though.. ;)

[waksupi]

If you want to size them down very far, run them through a lubrisizer to fill the grooves first.

[centershot]

That's pretty typical for an old war horse...

It's extremely common on these to have a generous land size with a tight chamber neck.

The NEXT step now is for you to check some of your once-fired brass to find out what size NECK your chamber has. "Typical" MN's generally can take 0.313"-0.314" bullets before you need to neck turn brass but no bigger... But I have several that even need case necks turned to run 0.314" bullets.

Do this BEFORE you go any further down the road of buying molds.... It will save you a lot of grief.

Then - I would load up ONE 0.317" bullet into an empty cartridge and verify it will chamber... ZERO of my Mosins will chamber a 0.317" bullet due to the chamber neck.. Zero! You might get lucky though.. ;)

I've heard about this neck constriction before, how exactly does that happen? Oversize threaded shank gets screwed into the receiver? The Russians should've let the Finns build there rifles for them, at least the Finns did it right! I'll do a pound cast to verify what I've got. Assuming it's a tight throat, can it be reamed somehow?

[Bookworm]

It's not a neck constriction, it's an oversize bore that's the problem.

I had a Mosin with a .315 bore. I had to turn the outside of the neck on some brass to get a .316-sized boolit to chamber..

The specs for the Mosin chamber show a .338 chamber neck. To get the round to chamber, I turned the neck to .010 thickness.

.010 neck wall + .316 boolit + .010 neck wall gave me .336, which chambered and extracted with no problem.

Turned out, the old Mosin shot 2-3 MOA, if I could control the long, heavy trigger.

[AntiqueSledMan]

Hello Guys,

I've sized my RCBS 45-300-FN from .458" down to .452" to shoot in a sabot for my muzzleloader,
the grease grooves almost disappear. I agree with waksupi, lube the bullet before sizing it down that far.

AntiqueSledMan.

[dale2242]

I size .321 bullets down to .315 for my .314 bore MN.
It shoots better with these bullets than it does with milsurp light ball ammo.
16 gr. 2400 and 1 gr dacron....dale

[centershot]

It's not a neck constriction, it's an oversize bore that's the problem.

I had a Mosin with a .315 bore. I had to turn the outside of the neck on some brass to get a .316-sized boolit to chamber..

The specs for the Mosin chamber show a .338 chamber neck. To get the round to chamber, I turned the neck to .010 thickness.

.010 neck wall + .316 boolit + .010 neck wall gave me .336, which chambered and extracted with no problem.

Turned out, the old Mosin shot 2-3 MOA, if I could control the long, heavy trigger.

But, if I ream the throat to .317", expand the case necks accordingly and size my boolits to .318-.319", the boolits are undamaged as they travel down the bore. Yes?

[Bookworm]

But, if I ream the throat to .317", expand the case necks accordingly and size my boolits to .318-.319", the boolits are undamaged as they travel down the bore. Yes?

Ream the throat to .317 ? What throat ?

Are you referring to the chamber of the rifle, where the neck of the cartridge sits ?

If so, that spec is .338". If your boolit is .317, that leaves .021" in which to fit the walls of the cartridge neck (the part into which you insert the boolit), and allow enough room for the case neck to expand, to release the boolit upon firing.

If you cartridge necks are perfectly round (unlikely) and perfectly even .010" thickness all the way around (even more unlikely), then in theory you can chamber a .317 boolit and have .001" remaining as clearance for the neck to expand to release the boolit when fired.

Any rifle made will have a certain amount of +/- from the specs, perhaps more so in the case of the venerable 91/30 Mosin Nagant.

If you are having trouble chambering the rounds with a .317" boolit installed in the brass, then something has to be changed.

The easiest thing to change is the brass. Turn the necks to .009, and see what happens.

[centershot]

Bookworm,
Yes, I see what you're saying, I didn't consider the cartridge neck diameter, just the boolit. My bad! .009" wall thickness, that's like 3 sheets of printer paper....... you said you've done this, so it must work. I have a Forster neck turning attachment for my trimmer, will that work or would you recommend something different?

[am44mag]

And therein lies the problem. 303 boolits are undersized, 8mm's are oversize. My 303 mould drops at .312" and 8mm is .323. Siz down the 8mm's by .005"??? Seems like a lot............:-|

I would do one of three things.

1) Paper patch a 30/.303 cal bullet (I do not know what size your particular guns would need)

2) Size down an 8mm mold. 0.005 isn't that much

3) Buy a mold that will drop at the size you need. Arsenal and Accurate molds might have what you're looking for. I'd check NOE too.

[centershot]

Yeah, paper-patching has been a thought in my mind, I'll need the specs from the pound cast to determine boolit diameter and paper thickness. All things considered, this might make the most sense.

[Bookworm]

Bookworm,
Yes, I see what you're saying, I didn't consider the cartridge neck diameter, just the boolit. My bad! .009" wall thickness, that's like 3 sheets of printer paper....... you said you've done this, so it must work. I have a Forster neck turning attachment for my trimmer, will that work or would you recommend something different?

I have turned necks on some 7.62x54r brass to .010" thickness. I have not gone to .009", but I don't think it would have caused a problem with the brass I turned.

Keep in mind; it doesn't matter how large the boolit drops out if the mould, or how large you size it, if it doesn't chamber it doesn't matter.

Paper patch to whatever size, size down from whatever size, if you can't close the bolt it won't shoot.

You only have so much room in the neck of the chamber. The cartridge has to fit in there first.

As for the trimmer attachment, I see no reason the Forster turning tool wouldn't work. It is an external turning attachment, correct ?
I use a K&M, they custom cut a mandrel for me, and it works perfectly.
Turning the neck is something usually done only once, so even though it's something of a chore, it needn't be done continuously.

[sutherpride59]

Have you gone back and verified that the initial slugged diameter is actually correct? That seems pretty over sized even for a gun that has seen heavy use. Just food for thought.

[centershot]

Yes, I've slugged it several times. The first time I did it I was surprised it was so large so I did it a second time. Same result.

[samari46]

look for a mold that casts at .321 and has a gas check shank. If you are concerned sizing down standard 8mm cast bullets. Try google for .321 cast bullets with gas check shank. I have one of the 1888 Commission rifles that slugs out at .321. So just about any regular 8mm mold can be sized down to .323 and give me a good .002 over the bore size. I've done this for my Finn 1935 model 27 which has a .3115 bore diameter so size to .3135 and away we go.Frank

[centershot]

OK, I finally found some time to do the pound cast. The case neck mikes 0.338", the rifling immediately in front of the case mouth mikes 0.314" and tapers to 0.317" at the muzzle. [smilie=b: Sooooo.......... I'm thinking I'm boogered! I'll beagle the mould to drop 0.315-6" and see if it'll chamber. If not I'll just drop back to 0.314" and shoot'em up! :Fire:

[Bookworm]

So the chamber neck is in spec. Most are. As I stated in my earlier post, you will probably need to neck turn to shoot the bigger boolits.