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Posted: 5/9/2009 3:30:25 PM EDT
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I would like to build a .357 Sig Upper to fit an LRB Lower Reciever. I will buy the major components and have my local, highly skilled gunsmith do the tough jobs (fit Bbl, ream a 9mm barrel to chamber 357, headspace/timing check, fit gas system). However, I need to learn as much as I can about it straight away.
I do have my lingering doubts as to if pistol cal carbines can be made to run as well as a rifle cal, but that is for another post... Any advice on where to get the following components, or what trusted manufacturers to use (without breaking the bank)? I imagine I would buy a 9mm bbl (pref. 16") have it reamed Get a 40 SW Bolt/Carrier group and that should fit easily once fitted by a good smith I would like a flat top receiver (any suggestions that work well for pistol cals?) Flat top gas block 16" std bbl Prefer mid length gas system with a good free float handguard system LRB Lower reciver (already have so not a negotiable part), with a Std RRA LPK Hahn magazine block Who makes a Mag Well to fit this for fast reloads? I see that most pistol cal carbines have probs vs. 5.56 ARs in the reloading times (competition biased which this rifle will be used out to 150/200 yds max) Colt or Metalform mags only Optic as yet to be determined Priorities are 1)maximum reliability (mags MUST lock back every time and chamber/fit every time) 2) everything else comes a distant second to feed function with std 357 loads thanks for any help you might have. I know there is a company who advertises they make this already online- but they are so far behind and don't even answer my emails, so please don't send me that link.... Thanks for any help you guys might have..... |
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ETA: Do you realize that pistol cal ARs are blowback? If you want a blowback 357sig. Oly is the only mfg. of 357sig and 40S&W ARs that I know of.
Gas powered is gonna cost ya custom $$ hmmm..... Colt style pistol cal, gas operated, in .357sig. You might be making the first one. ever Another member, RonWilliams, is making DI 45 uppers. I saw a 40 upper he made for an MGI gun on this sight. The most cost effective way I can see to do it is to buy an existing 9mm setup and alter it to run 357sig. |
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search is your friend
Kurts Kustom Firearms makes a 357Sig upper that uses Sten mags and a 9mm magwell block. Unfortunately, he has past away. Unknown if anyone is picking up @ KKF quote from Marty 357 Sig has been tried by several folks, Kurt's Kustom had a nice article published on it, but I am not sure how many folks bought one. Magazines can be a bit tricky and shooting a high pressure bottle neck case in straight blow back can be murder on your cases ... forget reloading i am sure will be along w/ more specific info talk to your smith, if he is in the know, he should have some thoughts on it. |
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I think others have already built a gas operated 357 sig. I think a guy with the handle of Tomster on here has done it.
Search the archives for 357 sig and tomster http://www.ar15.com/archive/topic.html?b=3&f=15&t=380476 |
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A DI/gas operated 357sig would not be a problem. Parts are available. Ive doen 9mm, 40S&W, 9x25 on gas. The pressures of the sig along with the bottleneck make it an easy conversion. Wow, that's awesome - how well does the 9mm run? I cant get it to run on factory fodder but most reloads work fine. |
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Would the gas port in the barrel have to be in a different location compared to a 5.56, and would the barrel have a barrel extension like the 5.56 ? Would a regular AR carrier be used as well, with a different bolt? Scott. Super short gas. 6.8 bolt is all that is needed. The rest is standard AR15 parts 
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A DI/gas operated 357sig would not be a problem. Parts are available. Ive doen 9mm, 40S&W, 9x25 on gas. The pressures of the sig along with the bottleneck make it an easy conversion. Wow, that's awesome - how well does the 9mm run? I cant get it to run on factory fodder but most reloads work fine. That's not too bad, I started reloading not too long ago. What sort of mags & magwell adapter did you end up using, and how short of a gas tube? Thank you, Greg |
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I think others have already built a gas operated 357 sig. I think a guy with the handle of Tomster on here has done it. Search the archives for 357 sig and tomster http://www.ar15.com/archive/topic.html?b=3&f=15&t=380476 Yep, I built a DI 357Sig AR a while back. It was built as a SBR with a 7.5" barrel and it has bolt hold open. I looked into a production model to sell, but the overall demand was very low, so it never went to market. Anyway, It was first built using sten mags. I didn't like the sten mag system because of the size/length and overall quality of the magazines. In addition, the sten system didn't have bolt hold open. So I adapted a colt style bolt hold open with colt style magazines. Building the gun was easy, getting it to work with a colt magazine system for bolt hold open brought about the majority of the challenges. Today, there are other options such as the pps43 mags that were developed by Marty. While I'm on a roll, Kudos to Marty for his work which led to my gun and then Ron's spin offs. If it wasn't for Marty, I probably wouldn't have built my gun in DI and we probably wouldn't have the DI 45 as we know it today. Anyway, enough of that..... I introduced the 357Sig DI over at the sigforum. It was so long ago that the thread doesn't exist anymore. I did a google to find that someone copied it over onto another forum so I will paste a link if you care to read it. 357 Sig DI rifle It was a lot of fun to build and experiment with, but it was a lot of work. Tweak, tweak again, and tweak again until it was perfect. If you just want to use an off the shelf mag/block system, it wouldn't be that hard to build. However, before you do, make sure that you have the skills to see the job through. So in a nutshell, yes it can be done because it already has been built. 
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[ we probably wouldn't have the DI 45 as we know it today. /quote]
I do not want to start a fight, and am in no way shape or form bad mouthing Marty; but Marty was one of the people that said it could not be done....Because the 45 ACP has not got enough gas to run the AR in DI mode. As we now see, it can be done and it runs great also. Ron and his thinking out of the box has made it a reality and not vaporware . |
| Let's not hijack this thread about a fellow ARFCOMer's 357sig project. Marty and Ron are doing great work and each has his own claim to fame here. The fellow "bls72bmw", that started this thread, only wants help with his project, not a discussion on who did this and who did that. Marty has been unavailable due to hurricane damage to his home and shop. Ron, luckily, has been able handle the gunsmithing load just in the nick of time. This may get tighter since Kurt of KKF is no longer with us. Since Ron seems to feel there would be no problem for him to do the 357sig project, maybe "bls72bmw" should contact him about doing the work. |
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......Marty was one of the people that said it could not be done....Because the 45 ACP has not got enough gas to run the AR in DI mode. Ron and his thinking out of the box has made it a reality and not vaporware . Amen. Oddly enough, the (what four year?) 7.62x25 "project" didn't run on surplus either until Ron decided it was time to make it work one afternoon. |
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I would like to build a .357 Sig Upper to fit an LRB Lower Reciever. I will buy the major components and have my local, highly skilled gunsmith do the tough jobs (fit Bbl, ream a 9mm barrel to chamber 357, headspace/timing check, fit gas system). However, I need to learn as much as I can about it straight away. I do have my lingering doubts as to if pistol cal carbines can be made to run as well as a rifle cal, but that is for another post... Any advice on where to get the following components, or what trusted manufacturers to use (without breaking the bank)? I imagine I would buy a 9mm bbl (pref. 16") have it reamed Get a 40 SW Bolt/Carrier group and that should fit easily once fitted by a good smith I would like a flat top receiver (any suggestions that work well for pistol cals?) Flat top gas block 16" std bbl Prefer mid length gas system with a good free float handguard system LRB Lower reciver (already have so not a negotiable part), with a Std RRA LPK Hahn magazine block Who makes a Mag Well to fit this for fast reloads? I see that most pistol cal carbines have probs vs. 5.56 ARs in the reloading times (competition biased which this rifle will be used out to 150/200 yds max) Colt or Metalform mags only Optic as yet to be determined Priorities are 1)maximum reliability (mags MUST lock back every time and chamber/fit every time) 2) everything else comes a distant second to feed function with std 357 loads thanks for any help you might have. I know there is a company who advertises they make this already online- but they are so far behind and don't even answer my emails, so please don't send me that link.... Thanks for any help you guys might have..... I would suggest you contact Ron here on the boards and send him your stuff and he will build it the way you want and also test it to verify all works.
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