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8/18/2017 1:54:51 PM EDT
I have a 9mm AR carbine that I built using mostly PSA parts.  Build specifics:
SBR'd PSA lower
PSA mag block for Colt pattern magazines
PSA Bolt
PSA 9mm buffer
4.5 inch barrel plus Octane 9 silencer
I don't recall the specifics of the recoil spring, but I do have a spacer in the receiver extension.

The gun is erratic, sometimes functioning fine for a few shots, then it will either stovepipe a round (failing to eject) while trying to feed another, and has sometimes had a double feed.  Ammunition used has been factory Speer Lawman 147 grain TMJ.  I tried to use some 115 grain Winchester just for comparison, but it seemed worse.  My guess is the gun is too fast but I'm no expert.  Any suggestions?  I'm thinking a heavier buffer, but thought I'd seek input before shelling out more money.
8/18/2017 4:02:37 PM EDT
[#1]
Quoted:
I have a 9mm AR carbine that I built using mostly PSA parts.  Build specifics:
SBR'd PSA lower
PSA mag block for Colt pattern magazines
PSA Bolt
PSA 9mm buffer
4.5 inch barrel plus Octane 9 silencer
I don't recall the specifics of the recoil spring, but I do have a spacer in the receiver extension.

The gun is erratic, sometimes functioning fine for a few shots, then it will either stovepipe a round (failing to eject) while trying to feed another, and has sometimes had a double feed.  Ammunition used has been factory Speer Lawman 147 grain TMJ.  I tried to use some 115 grain Winchester just for comparison, but it seemed worse.  My guess is the gun is too fast but I'm no expert.  Any suggestions?  I'm thinking a heavier buffer, but thought I'd seek input before shelling out more money.
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Need details on the buffer mass.

With blowback 9mm, and especially with the added pressure of the suppressor, you must be using a heavy buffer to retard bolt speed.
8/19/2017 10:22:42 PM EDT
[#2]
Fail to feed I can fix with a small mod to the feed cone......the stove pipe can be solved with a simple mod to the ejector nose that you can do.
You need a standard carbine spring and an extended buffer....I suggest the one I make for 9mm with an  adjustable weight between 5.5 and 7.5 ounces. On;y thing a spacer accomplishes is increasing bolt velocity on the loading stroke.....not necessarily a good thing.

Macon Armory 9mm buffer


I see you are in South Carolina......if you want to road trip over to Macon GA and come to the shop on a Saturday I'll mod the barrel fix the ejector and sell you a buffer and have you going home with a 100% gun....
8/20/2017 3:25:25 PM EDT
[#3]
Quote History
Quoted:
Fail to feed I can fix with a small mod to the feed cone......the stove pipe can be solved with a simple mod to the ejector nose that you can do.
You need a standard carbine spring and an extended buffer....I suggest the one I make for 9mm with an  adjustable weight between 5.5 and 7.5 ounces. On;y thing a spacer accomplishes is increasing bolt velocity on the loading stroke.....not necessarily a good thing.

Macon Armory 9mm buffer


I see you are in South Carolina......if you want to road trip over to Macon GA and come to the shop on a Saturday I'll mod the barrel fix the ejector and sell you a buffer and have you going home with a 100% gun....
View Quote
Thanks.  I may take you up on that offer.
8/20/2017 3:43:24 PM EDT
[#4]
Just let me know in advance....we'll be at Knob Creek from the  11th till the 16th of October.... currently no other plans to be out of the shop except for a hometown forum shoot I believe the weekend before
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