A few days back a shooter here contacted me about doing a couple AR pistol cartridge conversions for him….I built a couple rifle uppers for him that worked out pretty well …. I had to turn him down as I hadn’t done any AR pistol cartridge conversions, just focused more on the rifle stuff… I knew there were a few guys here that had made great advances in the DI pistol cartridge world and DI looked to be the direction to go….

I think the pistol cartridge conversions have a really neat utility component to them when matching to a sidearm….. So that got me to thinking and looking around the shop for parts to pull together into a DI pistol conversion build……I had recently built a P14 in 9/.45 and had all the tooling here to do another barrel…. thought it would be a really neat cartridge if I could get it to run in the DI AR…

The 9/.45 is basically a .45 ACP case necked down to 9mm….It has gone by several different names and dimensional changes over the last fifty years…..AKA the .38/.45 Clerke, .38 Casull, .45/.38 Auto Pistol, etc…..performance is pretty stellar, a 124gr fmj at 1,400 to 1,500 fps is pretty common out of a 5” 1911….the effective barrel on the AR pistol/carbine would work out to around 11” with an overall length of 16.5” with mid-length handguards and a permanently attached flashhider…so similar if not better performance should be pretty easy to replicate….

Parts used (not saying it’s the best, just what I had around the shop for the conversion)
- Olympic .45ACP magazine (modified for DI bolt and carrier)
- Armalite 7.62x39mm bolt and extractor (modified for .473” rim)
- Noveske Switchblock (modified drum and gas tube for short gas system)
- 400 Corbon brass (small primer and pretty stiff brass)
- M4 extension (ramped a little for the center feed)

The pre-assembled parts.




Modifying the Olympic magazine for DI bolt and carrier clearance.



9/.45 in modified Olympic magazine.



Dressing the gas block journal.



Modified mid-length handguard.



Rough assembled rig.



Everything fit great and the bottleneck 9/.45 feeds like a champ….velocity has been great!, loads are easily worked up in the 1,600fps range with the 124gr FMJ…….the case capacity and smaller bore of the 9mm made it a little easier to tune the port size, and the bolt hold-open is a nice feature also….I guess next will be a straight up .45 ACP…..

Standard carbine buffer and spring? What size gas hole?

I'm looking for a 45ACP DI upper that will work with a DDLES 45 Glock lower.  This maybe another option.

I have them on the shelf...........
Very nice work OP....how does the chamber pressure of the round you used compare to the 7.62 Tokarev? Gas system looks pretty similiar.

short answer:  yes,  .105"


expanded answer: 3oz buffer, standard spring....the gas system length from the extension shoulder to the gas block shoulder is 1.8"....I worked up the 11" velocity/impulse with the 124gr bullets before drilling the gas port....the decided velocity/impulse node is between 1,550 and 1,650fps and achieve as complete of a burn in 11 inches of barrel....

where it ended up:
124gr @ 1,625fps = cycles 100% and full lock-back on empty mag
124gr @ 1,550fps = cycles 100% and full lock-back on empty mag
124gr @ 1,5000fps = cycles 100% and no lock-back
124gr @ 1,400fps = cycles 100% and no lock-back

hope this helps...

thank you....I'm guessing they're pretty close, both in pressure and gas system length....the Tok may be able to get away with a slightly longer system due to the smaller bore.....the 9/.45 ended up at 1.8" @ 30K ish pressure?....I'm gonna start on a 45 ACP upper next, in pretty much the same layout except with a gas system length around .600" length??

Great idea and beautiful job.

I once built up a M1 carbine in 357 Auto Mag.   Mags worked with no mods.   Had to drop the pistol loads by 10%.   Managed to get 2000 fps from a 158 gr JSP.

I always thought the carbine conversions were really neat.....never looked into it very hard but I always thought one in 357 auto mag, or good ole 45 win mag would be pretty cool....congrats on the auto mag, probably a hell of a stalking carbine...

Darn! I wish I hadn't seen that!

Now it is officially under my skin! The biggest problem with my CA address is how hard it makes the magazine issues.

Now I gotta have one of these and for that to happen I have to first work out the 10 round magazine problem. Darn it....  

Makes me wonder about 357 Sig too? But if I can work the magazines, then your idea looks great! Congrats on a beautiful rig!

Merry Christmas!

HK USC mag well adapter I make should work well with it.......and I have a CA legal version with 10 round mags......

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