40 S&W Large Primer Pocket

[arakboss]

Any reasons why a person couldn't turn 10mm large primer pocket brass in to 40 S&W brass by trimming it down to 40 S&W length?

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[2Wheels4Ever]

Sure could. Not sure why you'd want to. 10mm brass is expensive and 40sw is basically given away.

 

[arakboss]

Sure could. Not sure why you'd want to. 10mm brass is expensive and 40sw is basically given away.

It's a primer supply issue. I want to utilize my small primers for cartridges that I don't have with large primer pockets.

 

[ageingstudent]

It's a primer supply issue. I want to utilize my small primers for cartridges that I don't have with large primer pockets.

I don't see any reason why you couldn't you'll just have to rework a couple of loads probably since you're going off the reservation a bit. That's a lot of trimming bro. Start low on your powder charges and work it up easy. The .40 can be a little touchy with the pressure.

 

[DLS]

You may have a "neck" thickness issue trimming that far back on a straight walled cartridge. Trim a few, seat a bullet and see if the outside diameter will still fit in your chamber or chamber gauge.

Other than that ... that's just a lot of trimming, do you have a power trimmer?

 

[arakboss]

You may have a "neck" thickness issue trimming that far back on a straight walled cartridge. Trim a few, seat a bullet and see if the outside diameter will still fit in your chamber or chamber gauge.

Other than that ... that's just a lot of trimming, do you have a power trimmer?

No power trimmer. just a trimpro. I might need a baby chopsaw, then I can make my own 300BO too.

 

[Member 66129]

I will trade you 40 brass for 10mm...

 

[arakboss]

I will trade you 40 brass for 10mm...

I have tons of 40 brass already thanks.

 

[ageingstudent]

You may have a "neck" thickness issue trimming that far back on a straight walled cartridge. Trim a few, seat a bullet and see if the outside diameter will still fit in your chamber or chamber gauge.

Other than that ... that's just a lot of trimming, do you have a power trimmer?

This is a good point the brass might be a little thick back where you chop it off and the bullet might not fit or the round might not want to chamber. Especially in a tighter chamber. Might have to bore a few thousandths out of the neck that would suck.

 

[arakboss]

This is a good point the brass might be a little thick back where you chop it off and the bullet might not fit or the round might not want to chamber. Especially in a tighter chamber. Might have to bore a few thousandths out of the neck that would suck.

I would not want to get that involved in converting brass, I will have to test some and see if that is an issue. Thanks for the advice.

 

[ageingstudent]

I would not want to get that involved in converting brass, I will have to test some and see if that is an issue. Thanks for the advice.

Yeah try a few and see if it's too much work for you it can't hurt. Sometimes you get lucky. If I remember rightly when S&W started messing with the 10mm and cutting it down to the .40 it had a large pistol primer but as the cartridge developed they switched it to a small. It's possible that the case wall isn't too thick you'll know if you try a few pretty quickly. Let us know how that turns out if you try it. Any port in a storm right?

 

[DLS]

I would not want to get that involved in converting brass, I will have to test some and see if that is an issue. Thanks for the advice.

That's no lie ... neck reaming is a major chore.

The little chop saw Harbor Freight sells is perfect for cutting down brass but it's a lot of work ... both .300 BLK from .223 and what you are proposing to make .40 out of 10mm.

Another thought is you can get a trim die for the .40. These dies have a tool steel hardened top. You'd push the 10mm case up into the die (most size as well) and the extra length sticks out the top. You can hack saw off the extra length then take a file to smooth the cut. The top of the die is hard enough to be file safe. You end up with properly sized brass of the proper length. It's not as much work as it sounds actually.

The brass is easy to cut and file, so it only takes a few passes with each per case.

 

[arakboss]

That's no lie ... neck reaming is a major chore.

The little chop saw Harbor Freight sells is perfect for cutting down brass but it's a lot of work ... both .300 BLK from .223 and what you are proposing to make .40 out of 10mm.

Another thought is you can get a trim die for the .40. These dies have a tool steel hardened top. You'd push the 10mm case up into the die (most size as well) and the extra length sticks out the top. You can hack saw off the extra length then take a file to smooth the cut. The top of the die is hard enough to be file safe. You end up with properly sized brass of the proper length. It's not as much work as it sounds actually.

The brass is easy to cut and file, so it only takes a few passes with each per case.

You reminded me of this kit I bought from a NWFA member. It came with a bunch of trim dies but not one for 40 S&W.

 

[Legion489]

The first thing I thought of was case capacity. The 10mm is, I believe, a heavier case and thicker all around. The same reason you can't chop .45 ACP cases back to .45 GAP. The ACP case is thicker farther back and the bullet will bulge the case and pressures go through the roof PDQ! I would suspect the same with 10mm to .40 S&W, thicker/heavier brass, bullets will not fit/bulge the case/won't chamber, erratic pressure spikes and generally a risk to life and gun. Please keep me informed if you do this, but I have absolutely no urge to try it myself/my guns. Any reason you can't just buy a 10mm barrel to fit your gun and shoot .40 S&W level loads through it? With equipment costs, time, labor, loading, it would be about the same cost and much easier.

 

[TTSX]

I'd almost wonder if it'd be easier to bore out the primer pocket to accept larger primers, instead. Then you have to case thickness issues and no trimming, either

 

[DLS]

I was thinking the same. A powered primer pocket reamer tool should be able to do this without too much trouble.

 

[arakboss]

I'd almost wonder if it'd be easier to bore out the primer pocket to accept larger primers, instead. Then you have to case thickness issues and no trimming, either

I think you might be right. If that worked it would save me even more cash because I have much more 40 brass than 10mm brass. I will try that first before sacrificing any 10mm cases.

 

[arakboss]

I was thinking the same. A powered primer pocket reamer tool should be able to do this without too much trouble.

My concern would be centering the primer pocket tool as I am expanding the pocket. I don't have a powered primer pocket reaming tool but I might be able to chuck one of my manual primer pocket reaming tools in a drill?

 

[titsonritz]

I have tons of 40 brass already thanks.

He'll still trade you.

 

[DLS]

My concern would be centering the primer pocket tool as I am expanding the pocket. I don't have a powered primer pocket reaming tool but I might be able to chuck one of my manual primer pocket reaming tools in a drill?

If you chucked one into a drill press or a fastened down drill then gently pushed the case over the spinning reamer you may be able to get it done.

I'd wear tacky gloves and go very light at the beginning, since the reamer edge may want to grab the primer pocket edge and that could be "interesting".

With a fixed reamer the case and the reamer are held in alignment so that wouldn't be a problem.

If you have a drill press I suppose you could drill a hole in a thin piece of hardwood the size of the case. Clamp that to the drill press table to hold the case centered under the chuck and use the press quill to push the reamer down into the pocket. The only challenge is holding the case so that it doesn't spin as the reamer cuts the new pocket.

Will it work ...