Originally Posted by Formidilosus
The PSA FN barrels are gassed to run worst case- weak 223 with an H2 buffer.

You'll want an H2 (H3 might be worth a try), and ensure you have the SOCOM bolt upgrade kit for the extractor to use 5.56mm pressure Ammo.


Better yet, just put on an adjustable gas block.

I just went through this with a new build that had a very large gas port in the barrel (had a .093" instead of a more normal .078-.080"). But the FN barrel shouldn't be that badly overgassed on the port size.

I'll be somewhat surprised if an H2 or even an H3 will be enough based on where you are at, but I assume you're starting with a carbine buffer, so maybe so.............PSA uses some really cheap ass springs too so you might want to put a slightly enhanced buffer spring in as well. Sprinco Blue is a slightly heavier than standard spring.

In my case, the H3 plus a heavier spring still wasn't enough..........ejection was at 1 o'clock with 5.56 & the lighter stuff barely got ejected & really didn't move going from an H1 to an H3.

And don't underestimate the value Formy's comment on the extractor spring upgrade either. You can get a Colt version here for a reasonable cost.

Colt Parts

As for the Nosler 77 grainer's, they don't do as well for me either as other bullets do, but they are good enough for most purposes but when I use up the current supply, I won't buy any more,

Here are some pics from load testing a while back. Powders & loads are shown if they are of any benefit to you.


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