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10/15/2014 12:15:32 PM EDT
I have been having a lot of failures to feed with my AR build. It is a Spikes Tactical mid-length upper on a Seekins Precision lower with a Palmetto State Armory lower parts kit. I also have a blue Springco buffer spring and a H2 buffer in it as well. The rifle functions fine with brass cased ammo and pmags, but when I use USGI steel mags and/or steel cased ammo, I constantly get failures to feed. I have tried using multiple steel mags, but keep getting the same issue. I tried switching the upper onto my Stag arms lower, and it functioned just fine. But when I put the stag arms upper onto the Seekins lower I built, it was having the same issue. So I have concluded it is not a problem with the upper short stroking, but a problem with the lower. Any suggestions or thoughts? I know I can run just pmags and be fine, but I like the option of using USGI steel mags like all my other ARs.

10/29/2014 10:26:04 PM EDT
[#1]
I had a similar issue. A buddy has a slow mo camera and shot some video. I denied short stroking too and learned quickly that it was short stroking. I've personally never had an issue with a lower, but BCG's, gas keys, bolts and anything gas related. If that's how you are shooting it, it doesn't have near enough oil to suit my rifles...
10/29/2014 11:05:36 PM EDT
[#2]
Make sure the mag catch is installed properly with the end of the threads flush with the outside of the mag button.  New uppers typically don't like steel ammo. Try them again after a few hundred brass rounds.

 
10/30/2014 12:32:49 AM EDT
[#3]
Are you sure that you have the correct length buffer and correct length spring for the receiver extension in play?
Forget all about upper receiver,  The void depth of the receiver extension dictates what length buffer and spring are to be used in that lower.
Telescoping butt stock uses a carbine buffer, and carbine spring (10.5'), while a fixed stock will use a standard full length buffer and 11.75" spring instead.

As for H buffer in a telescoping stock lower, only if you are shooting 69gr plus ammo, and if just 55/62gr ammo, then should be running the 2.90z buffer.


Short of this, they maybe hammer wedging or FCG springs not installed correctly, and if this is happening, the back top tail of the trigger/disco is going to have nasty impact marks from the hammer tail.
10/30/2014 12:33:48 AM EDT
[#4]
As already mentioned, check the magazine catch to see if it is installed so the threaded portion of the catch is flush with the magazine release button.  Next do a thorough cleaning, followed by lubricating to make sure everywhere that metal rubs metal is lubricated well to reduce any possible friction issues. making sue you hit areas like the 7 bolt lugs, around the entire bolt carrier.  Use a quality lubricant like Slip2000 "EWL" Extreme Weapons Lube, applying so everything is good and wet.  You may also have a power factor issue, as you are running a mid-length gas system with H2 buffer and Springco spring, then combining it with steel cased ammo that might be softer that the brass ammo you state the rifle works on.  So maybe try running a lighter buffer, softer action spring (buffer spring), and see what happens.    

CY6
Greg Sullivan "Sully"
SLR15 Rifles
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