I'd like to introduce to you all to my latest project. It is the world's first gas operated (direct impingement) 357 sig AR15.



I took her out to the range yesterday and finalized the gas port, buffer weight, and recoil spring/length. Function, feed, ejection all work just like a standard AR15.

Currently, I have the magazine system based upon sten magazines. I am not happy with the sten magazines for a few reasons. First, sten magazines do not have a bolt hold open feature after the last round is fired. Secondly, sten mags are old as dirt. Most of the mags I have are WWII surplus and they look every bit of it.

My next project with this gun is to retrofit a Hahn mag block to accept colt magazines so that the bolt hold open feature will work.

When I took her to the range yesterday, I brought with me a box of Winchester, speer gold dots, and two varieties of my handloads using VV3N37 (one set with light powder charge and the other with a more nominal charge). After opening the gas port little by little, I was able to get the Winchester, speer, and the VV handloads (with the heavier charge) to work 100%. However the VV light load would not bring the bolt back enough to engage the bolt catch. Not a big deal, because this gun will work with standard handloads and commercial ammo.

I have always wanted an AR chambered in 357 sig. What has stopped me from building such a beast in the past is that all previous systems were based upon the blowback design. Why is this a big deal you ask? Blowback in an AR with a hefty cartridge like the 357 sig would produce a LOT of recoil. In addition the chamber pressure of this round is approximately 40,000 PSI. As soon as the cartridge is ignited, the bolt begins to move back immediately, prematurely ejecting the case before the pressure has subsided. All blowback 357 sig guns leave the cases looking like .40S&W after ejection. This leaves the brass all torn up and in a non-reloadable condition.

With the DI gas operated 357 sig, the case is ejected from the chamber at the proper time, approximately when the bullet leaves the barrel. Because of this, the pressure has subsided enough to leave the case in the proper size and in a reloadable condition.

I was inspired by a person over at AR15.com who goes by the name of MartyW. He has pioneered the worlds first 7.62x25 Tok gas operated AR15. His work showed me that a project like this was possible. Anyway, enough of the credits.

I plan to send the barrel out to get it parked early next week. I left it unfinished because of the gas port work that was required.

After that is complete, I will take on the Colt magazine/bolt hold open project as time permits.

I will keep you all updated as to the Colt magazine project as it develops.

Anyway, thanks for the forum and I'm glad to share this with you guys here first, because I know there are quite a few 357sig nuts (like me) hanging around.

This message has been edited. Last edited by: Tomster,

That is amazing!

So many questions, what type of bolt? Standard AR? Pistols levgth gas system correct? Did you think about a carbine length system? You said standard buffer weight, no need for H2 or H3?

That is very, very cool. More details please, pics, everything is interesting. Where is the barrel from? What does the gas key look like? How did you do the bolt?

VERY cool project. I didn't know that it existed, now I am wondering how to live without one.

Ever thought of a 10MM Auto project?

That is just too cool. How's the accuracy? How does the recoil compare to 5.56?

That is awesome.
Please keep us informed and updated.
There has to be more of us who are interested.
Thanks again.

quote:

Originally posted by JSB 147:
I didn't know that it existed

It never did, until now

quote:

Originally posted by JSB 147:
now I am wondering how to live without one.

I may decide to produce/sell these down the road. Before I do, I have to work the bolt hold open/colt magazine issue and then look into making some non NFA lengths for the non NFA market.

Thanks for the interest.

Super freakin' hawt!

Very nicely done.

Oat

Wow! Very cool!

Frickin' awesome project.

And here I was tellin' people just last evening that pistol cartridges do not provide enough gas volume / pressure to operate a DI/piston AR.

Thanks for proving me wrong . I'd love to see a 10mm Auto version (Lower pressure, higher volume, might work?).

Now THAT is cool.

Cool!!

Outstanding project! +1 on the kudos and requests to keep us updated.

What a fantastic project and a beautiful firearm.

can you post pictures of the gas system?

This message has been edited. Last edited by: dont_tread_on_me,

Does anyone know when the next FL sig shoot is? It would be a great opportunity for folks to get a hands on and provide feedback on their impressions!

I've invited my friend TooVira to shoot it next time we shoot together. However, the barrel is going out to be parked early this week and will take some time to get it back.

Great work Tomster!!!

Freaking awesome. My agency issues the .357 Sig as a duty cartridge. I have got to get me one of these.

edited because I was too entranced by the pictures to read the whole post.

My favorite round, looks very nice.

[QUOTE]Originally posted by Tomster:
Does anyone know when the next FL sig shoot is? It would be a great opportunity for folks to get a hands on and provide feedback on their impressions!

QUOTE]

When and where for the shoot? I'm north of Orlando.

Interesting idea. However, I dont see the advantage of the .357 SIG over 9mm in a carbine.

The only reason I say this is that the overall cost of 9mm vs. .357 SIG and the fact that the muzzle velocity of the 9mm is enhanced when utilizing a carbine platform. Add to this the availability of existing 9mm AR parts and mags without the need to modify, for my $ Ill stick with the 9mm.

Good follow through though.