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Discussion Starter · #1 ·
I have a little M1 carbine sporter that was drilled out and rechambered to a .375 - 38/40 Rimless round. This is basically a 30/06 case cut to 1.25" long and necked down to take a .375 bullet (I use the 200gr Sierra flat nose). It was an attempt 50 years ago or so to make a short range deer gun out of the M1 carbine. The rim about maxes out what's possible for an M1 bolt head.

I don't know that anyone will have experience with this round - it's an oddball. My question is a little more generic. I've made cases for it in the past from 30/06, and it forms just fine. But the case necks end up being REALLY thick. Rounds will chamber with them, and most commercial brass will give me a little expansion room to work OK, but I'd like a little more. Really, I'd like to not have to worry about it. I don't have neck reaming equipment, so I've been looking for other possible solutions.

What I'm considering is trying to use .45 Winchester Mag pistol brass from Starline. Both rounds use very similar loads of 2400 powder for the same weight bullet, so I think the cases would be fine in construction. The Starline cases are spec'd out at 1.91-1.96" long, which is about 1/16" shorter than my case. Might be a little less difference when they are necked down, but not much. These cases wouldn't require neck reaming, but would be a little short. I also am very limited on overall cartridge length due to the M1 carbine mag body, and it's a really tight fit with ammo made to the spec's in Donnelly's Cartridge Conversions book. So a little shorter brass might be better for fit purposes.

This is a rimless, bottlenecked cartridge. The shoulder is about 3/16" long and at an 11 degree angle. I would still have plenty of neck to hold the bullet. Does anyone see any potential issues or have experience that says not to try this (using brass .06" short, neck only)? Or other potential solutions other than buying a neck reamer? The brass will be formed and resized with a custom RCBS die set I ordered years ago from a Cerrosafe chamber casting. I want to get some opinions and make sure I'm not missing something before I order some brass.

Opinions?
 

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An interesting concept, I think. I remember when Bishop and Fajen sold stocks and Williams Gun Sight sold parts and information on how to make these more suitable for hunting and less military like. We would be hung from our toes for that now. Isn't the .308 Winchester/7.62 Nato base/rim dimensions nearly the same as the 30-06? Maybe with it's much shorter case the walls would be thinner at the length you require. Just a thought. Neat gun. Tom
 

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Simplest suggestion would be to just neck ream so as to allow you to safely shoot the sierra 200 grain flat nosed bullet. Or if you want you can outside neck turn the neck portion. As far as caliber is concerned that is a new one to me. regarding the brass that you have been using so far. Is it military or commercial brass. usually the commercial stuff is somewhat thinner than the military stuff. You could get away trying 300 savage brass as I've made 300 savage cases from 308 commercial cases. That is about the smallest 30 caliber brass (300 savage) brass readily available. I've no experience regarding the 45 winchester mag brass. Think that starline sells them, good brass. Frank
 

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Years ago (Guns Magazine) there was a Project to convert the M1 Carbine to "30 Kurz" ( ie, a 7,9x33 Kurzpatrone to 30 cal) using the Head size (.470) of the 30/06/308 etc. It was essential to ream the necks of the case formed, as the resulting neck was about Twice the wall thickness of a .30 Carbine case; and if not reamed, the "Neck crowding" in the chamber's neck would cause Pressures to skyrocket.

Seeing that this cartridge is a .375, the Neck reaming is still essential.

For cases to use, the best is to use .30/06 or .308 Mil. Cases (commercial cases are a bit lighter), in order to have case safety in the Head and Body. And it is also the cheapest way to go. A better solution ( for Bolt integrity) would have been the use of Starline 10mm Super Magnum cases ( 10x32), necked down to 375 or 35: that would give a better bolt retaining lip, and a strong case with suitable length for the Magazine. ( 10mm head size is same as .30/30 head ( not rim)diameter, .420".) Still enough case capacity to give a good, zippy Load.
I am currently prototyping a ".357x32mm, to use in a Chambered-out 357 Desert Eagle (Long. barrel)...the resulting cartridge will feed thru a .357DE magazine, and the 10mm rim seats perfectly in a .357 DE bolt face. Soime Power Factor Silhouette Pistol!!

Doc AV
 

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Discussion Starter · #5 ·
Years ago (Guns Magazine) there was a Project to convert the M1 Carbine to "30 Kurz" ( ie, a 7,9x33 Kurzpatrone to 30 cal) using the Head size (.470) of the 30/06/308 etc. It was essential to ream the necks of the case formed, as the resulting neck was about Twice the wall thickness of a .30 Carbine case; and if not reamed, the "Neck crowding" in the chamber's neck would cause Pressures to skyrocket.

Seeing that this cartridge is a .375, the Neck reaming is still essential.

For cases to use, the best is to use .30/06 or .308 Mil. Cases (commercial cases are a bit lighter), in order to have case safety in the Head and Body. And it is also the cheapest way to go. A better solution ( for Bolt integrity) would have been the use of Starline 10mm Super Magnum cases ( 10x32), necked down to 375 or 35: that would give a better bolt retaining lip, and a strong case with suitable length for the Magazine. ( 10mm head size is same as .30/30 head ( not rim)diameter, .420".) Still enough case capacity to give a good, zippy Load.
I am currently prototyping a ".357x32mm, to use in a Chambered-out 357 Desert Eagle (Long. barrel)...the resulting cartridge will feed thru a .357DE magazine, and the 10mm rim seats perfectly in a .357 DE bolt face. Soime Power Factor Silhouette Pistol!!

Doc AV
Doc, you've given me a great idea without knowing it. I can get 7.9x33 Kurtz brass from PPU. I will only have to expand and trim slightly, and everything else should be just fine, no reaming necessary. It will cost more, but come with a lot less futzing on each case. Hadn't thought of this one as I do not use it, and always think 30/06 first when making most of the metric milsurp rounds I use. Does anyone have any of this PPU brass? I'd like to know how thick the rims are. Most of their brass I have seems to be on the thinner side on the rims.

For those interested, I tried to use LC military .308 brass years ago, and found the side wall so thick at the cut off point that I couldn't get it formed easily. Not going that route.

Here are a couple pics for those interested. This rifle came to me through family, and the work was done at Fort Lewis long ago. It's a family piece, so there's a little more reason to get it shooting correctly for me. The checkering is not great, but he was not a professional gunsmith or stock maker.


Something in the 10mm family would have been great, but they weren't around at the time these were being converted to .375/38-40 Rimless and .375 Shannon. The bolt head is absolutely maxed out for the .470" rim, so smaller would have been better. I have found that I need to put a slight bevel on the rims to help the extractor out in chambering - the extractor is already cut back a ton to get this round on the bolt head, so there isn't a whole lot I can do to it otherwise. Might try a little lighter spring, but that's about it.

Doc, please tell me why you think I would be best served by using military brass. Yes, it's thicker and stronger, but also has less capacity. I also will not be pushing limits on this - it is an M1 carbine after all. I can't imagine that commercial brass will not be just fine. But you probably know something I do not. This will be a 44 Rem Mag / 45 Win Mag class cartridge. What gives you reason to be concerned about brass strength?

In any event, my original question is still out there. Would anyone feel concerned about using brass that's .06" or a little less short on the neck? I don't think I need to go that route now, but it would still be good to know what feelings are. A little shorter would be a good thing from the mag and bullet seating in this situation, but????

Thanks guys.
 

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This is a good thread that illustrates why reloading pays off...getting a rifle back up on the firing line
because its important to the owner. If he were not a reloader, that family rifle is a paper weight.

This is a unique caliber situation but I remind all that calibers on the market come and go. For decades many such calibers were a reloading situation or the rifle could not be shot.

Reloading pays off in many ways and its a heck of a great hobby.
 

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If you still have the chamber cast that you made measure the chamber neck of the casting.
If you don't have it make another or measure the neck with gauge pins.

Then make sure your loaded ammo is .002 to .004 smaller than the neck of the chamber.

If you don't have a micrometer buy one. You can sometimes find one like new on Ebay for $7 to $15 for a brand name quality mike.

Probably the thinnest commericial brass is made by Winchester. So you might weigh different brands of brass and make a few test cases from the lightest brand.

Believe it or not but there was a magazine article about this same conversion about 45 years ago in Shooting Times or one of the other gun rags.
I understand your family attachment but I can remember thinking it was more of a fun project for the guy rather than a practical project.

You don't really need a neck reamer - you need a neck turning tool with a pilot. But you apparently are not interested in the extra work and that is all it is - work. Work that is easily wasted with an autoloader since it will try to toss your brass into the weeds.

What you will come up with is not a lot different than the .357 Automag.
 

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Discussion Starter · #9 ·
Believe it or not but there was a magazine article about this same conversion about 45 years ago in Shooting Times or one of the other gun rags. I understand your family attachment but I can remember thinking it was more of a fun project for the guy rather than a practical project.

You don't really need a neck reamer - you need a neck turning tool with a pilot. But you apparently are not interested in the extra work and that is all it is - work. Work that is easily wasted with an autoloader since it will try to toss your brass into the weeds.

You might be the first person to ever call me out as lazy??

With three kids and an older house, I have more than enough things vying for my time. Better put, I have a lot of things that never seem to get done.

I don't own any case neck tools, inside or outside. I've been reloading for 30+ years, load over 40 different rounds, and have not needed any yet (beyond length trimmer). I would like to avoid buying any for just this one round if possible.

My thought process around using the 45 Win Mag brass was that I would save time, because it would only require sizing. It is also relatively cheap, since it is a pistol round that is made by Starline. And it is readily available. The rounds are fairly similar anyway.

Most of my shooting is at my club's ranges, which are covered and have concrete floors. So the grass won't claim too many, based on experience with other autoloaders. But if I can get a case off the shelf to work with less labor, it's just better for replacements. And they'd be more consistent to work with than used range brass. The 7.9 Kurtz will work, I believe, but the 45 Win Mag would be easier to get and is almost half the price.

Sooo.....anyone want to give me an opinion on whether having a neck that is 50-60 thousandths short is a potential problem?
 

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There is / was shortened and thinner walled 308W / 300S based brass for the various Bench Rest and IHMSA rounds.
 

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Sound Guy,
why waste good 6,8 cases to make 8mm Nambu.?.. I simply "Head swage" .40S&W cases (push them into a .30/30 die, with a flat "shell Pusher" then Push them out) to get the right head size, then simply FLS in an 8mm Nambu die...This is our Commercial means of manufacturing 8mm Nambu cases...also, there is some difference in the diameters/thicknesses of .40S&W rims, which may affect the closure of a Nambu Pistol. When Head swaging, run the case in but with the Rim "out"side the die, at full stroke.

BTW, trying to Full-size .40 S&W directly in a 8mm N Dies will give a "belted case"...NO GO in Nambu Chamber.!!!

Doc AV
 

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Why waste good 40 S&W? ;0

1, I don't shoot 40, so have no cases.

2, I Do shoot 6.8, so DO have cases.

3, I have an RCBS case reforming kit ( 5 stages ), that takes 30 remington to 8mm nambu. ( nice kit has the inside neck reamer, and a few different shell holders and extended holders and spacers so you can do the work on different presses in stages

4, 30 rem is almost impossible to find, but I do have that reforming kit. 6.8 is one of the cheapest and easiest AR platform ammo to find other than 556.

1st step is to cut the 30 rem down. Since 6.8 spc is based on the 30 rem cartridge. Once you cut the 30 rem down, and cut down a 6.8, you have the same starting point, thus a cut down 6.8 works in the die forming set in place of a 30 rem.

Since I hav ethe kit, and surplus 6.8, I just use it. Especially since i don't have 40, nor do i plan on owning a 40. ( but I do shoot 6.8 ). When/if my 6.8 starts to get neck splits, or badly damaged necks or shoulders from ejection, they make great candidates to cut down as I am cutting off the damaged portion. So it is kind of like recycling / repurposing otherwise scrap brass IMHO.

Now that you can find correct headstamp nambu brass it isn't much of an issue.. I think I have maybee 100 pcs of real nambu brass now.. so I don't often make nambu from 6.8, but do every now and then.
 

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Discussion Starter · #14 ·
Got in an order of 7.9x33 Kurtz PPU brass. I only need to taper expand this, FL size, trim about .025", and anneal. And put a chamfer on the rim to aid the extractor. Way easier than any other option. Thanks for the idea DocAV!
 

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Wish I'd have read this posting sooner.
I could have sent you 50 30 kurz cases to try.
I have the form, trim ream die set and can't come up with a justification for them. But that's never been a requirement I guess!
As stated earlier, I think this was one of the options to modifying the M1 carbine decades ago as I had purchased a few extra receivers in the 80's.
Boy, did this dredge up some old memory cells!
Did the swagging/reaming of 30 Remington into 8mm Nambu also-but that was for a vet who flew a P51 in China in early 40's and had Nambu his Chinese bodyguard gave him, but no ammunition.
 
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