.380 auto rim?

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LiENUS

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A little bit of a crazy idea here but lets start with the beginning.

Background: My mom has a .380 auto revolver from Taurus and my brother in law has a .380 LCP. It's nice to be able to use the same ammunition for both but the problem is my mom hate's the moon clips.

Possible solution?: She wants to get a .38 special revolver which is quite the possibility. I Suggested she try one of the many moon clip tools out first to see how she does. However a third possibility arises. Would it be possible to take .38 special brass (I have a virtually endless supply) and trim it down to .380 acp length then load to .380 acp specifications and use .380 acp dies with the .38 special shell holder? I have a few concerns with that though, headspacing (Not sure how to check this on a revolver when making a custom cartridge like that), Case capacity I suppose just measuring the hydraulic capacity of the case and making sure they are close enough to each other would be sufficient and finally case strength/ I understand the cylinder contains most of the pressure but is there a difference in the webbing around the case head between the .38 special and .380 acp? I would expect the .38 special to be stronger than the .380 acp but I really don't know. The idea behind trimming the .38 special brass is to make a sort of .380 auto rim like the .45 auto rim for .45 acp revolvers. That way she can have brass that operates properly with the extractor so she doesn't need moon clips.
 
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I think the base diameter is larger on the .38 brass than it is on the .380..

I've never reamed a chamber, so I don't know if it's possible or not to put a .38 reamer down the cylinder to rechamber it..

-edit
I looked, and yes, the .38 is a straight .379 SAMMI diameter
and the .380 is .374 at the base, .373 at the mouth

someone more familiar may be able to tell you more..
pressures look basically the same, high end loads running 15,000-16,000 CUP..
 
I'm not looking to modify the revolver at all so if the chamber would need to be reamed that would be a no go. But would running the .38 special brass through a .380 acp sizing die then loading with a .380 acp bullet through it be enough to safely change the base diameter or is the difference in size (.38 special looks to be a larger base diameter) too great and I may end up risking a stuck case or worse weakening the case somehow?
 
Hmm I dropped a fired 38 special case in the cylinder and it goes in fine... might it be safe to do my resizing on these trimmed cases with the .38 special dies and then flare seat and crimp on the .380 acp dies assuming all else checks out...
 
humph.

Must be the chambers are a little worn..

Dude, I honestly can't tell you a reason to not, based on that..

Maybe make up some dummy rounds and make sure they don't tie up the cylinder?

Other'n that, keep the loads below maximum and it just might work.

What I think I'd do, is use the expander ball out of a .380 die to make sure you don't oversize the mouth...

as far as your headspacing goes, a rimmed cartridge headspaces off the rim, a rimless off the case mouth. Use of a full moon or half moon clip would in essence headspace it off the "rim" anyway, so party on..

Maybe run them though a Factory Crimp Die as a final operation?
 
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What is the head spacing going to be like? I'm not familiar with the 380 revolvers, but if you look at 45 Auto Rim, it has a very thick rim compared to normal revolver rounds. Otherwise I would say go ahead and run one through the 380 sizer. There is only 0.005" difference so it might just work.
 
I suppose trying some dummy rounds may be in order. There isnt an expander ball on sizing dies for straight wall cases afaik (using lee at least), admittedly I've never taken apart any of my straight walled dies but I believe it's just a decapping pin. The expander is on a separate die and would be be far too long on the .38 special die to even touch the .380 acp case so I believe I would need to use a .380 die on the shortened .38 special brass. All I would do on the .38 special die would be sizing and decapping.

Is the best way to measure case capacity to use sized and decapped brass with something plugging the flash hole like a little rtv? or should I use fired brass and just let the primer plug the flash hole?
 
56hawk I have no idea what the headspacing will be like. The revolver does headspace on the case mouth as you can fire .380 acp rounds without the moon clips, you just can't extract them that way unless you use a dowel rod. My understanding is the moon clips are .020" thick while the rim on .380 brass is .045" so it looks like the cartridges end up sticking out at least .065" from the cylinder when properly headspaced. while .38 special should stick out about .058" from the cylinder... The difference will be about .007" seems like that wouldnt be too extreme to me...
 
Good point, if you are headspacing on the case mouth the rim thickness doesn't matter.
 
I suppose using .38 special dies to do the sizing may leave me with neck tension issues so checking the tension on my dummy rounds is another issue i need to worry about...
 
if you're using a moon clip, you're headspacing on the clip anyway.. so as long as the cases don't exceed the depth of the chamber, it's a moot point.
 
John, the idea is to avoid the use of moonclips with the .38 special brass trimmed down. But the gun operates with or without moonclips on .380 acp brass so it'll headspace on the case mouth just fine.
 
Might be worth locating some .38 S&W brass and see where that leads you.

http://www.hipowersandhandguns.com/38 S&W-the other 38.htm

It is bigger around then .38 Spl, but a much shorter case, and would only need to be trimmed .095".

If you can resize it enough to fit the .380 chambers, you will not run into internal case web taper problems & bullets bulging the case like you might with shortened .38 Spl brass.

rc
 
Your dia. at the web on a 38 SPL is .379 and on a 38S&W is .386. The brass length is .775 and the bullet dia. is .361. and the rim dia. is .440, rim thickness .055. That is on a factory round.
Hope this helps
Rick
 
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Hmm, Would it be reasonable to get a case neck turner and turn the cases a little bit to thin the material around the mouth? 38 short colt brass isn't that expensive but I am absolutely swimming in both 38 special and 357 magnum brass and I don't even own a 38 special or 357 magnum gun.
 
A neck turner won't work.

The tapered case web wall is on the inside.
So they would have to be inside neck reamed if bulging bullet bases became a problem.

Why don't you trim some and try them in the gun first and see it it will set off primers with the headspace you would get.

rc
 
rcmodel said:
Why don't you trim some and try them in the gun first and see it it will set off primers with the headspace you would get.

rc
Click to expand...

It will.


Taurus Rimless revolvers are unique in that the stellar clip is based on achieving 38 rim thickness on a Rimless extractor groove. This way a 905 ends up being nothing more than a 85 with 9mm chambers. No extra machining on the rear of the cylinder required. The 380 carries over the same principal.

As my link shows with the thinnest cases (read Remington) the concept of 380 rimmed is sound.

Adversely supposedly using the 380 stellar clips you can use 380 acp in a 38 m85 as again the guns are the same from the rear of the cylinder rearward






posted via that mobile app with the sig lines everyone complaints about
 
LiENUS said:
John, the idea is to avoid the use of moonclips with the .38 special brass trimmed down. But the gun operates with or without moonclips on .380 acp brass so it'll headspace on the case mouth just fine.
Click to expand...
yah, I know dat very much, eh?

My point was, using moon clips on .380 brass and a rim on the .38 brass renders headspacing a moot point.
 
R.W. Dale: I have plenty of Remington cases I did my test trims with speer as those are the ones I have the most of. We'll see if they bulge or not

zxcvbob: I will probably pick up some .38 short colts, I'm just swimming in 38 special cases and I have nothing that shoots them (my dad has tons of 357 magnum guns and he dumps all of his brass on me)
 
So swap your 38 SPL and 357 brass for what you are looking for.:D Or sell it in the trading post here and just order the brass with those funds. Sounds like that's what I would do if in your shoes. I know, it is a bit more work---but not really if you do not have to work the brass.:cool:

On the other hand you could get the cylinder reamed out to 38 S&W but that would still find you buying brass and dies.:(
 
LiENUS said:
I'm just swimming in 38 special cases and I have nothing that shoots them (my dad has tons of 357 magnum guns and he dumps all of his brass on me)
Click to expand...

Don'tcha just hate that? .38/.357 and 9mm brass are about worthless if you go to turn it in.. might as well save up a ton and get a couple hundred bucks for it that way...
 
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