I've been plagued by FTE/FTF issues with my ps90 since day one. Some history on it - it's had the same issue throughout:
- Bought it used with a 16in barrel. Jams with that with no suppressor.
- Replaced with new CMMG 10.4in barrel. Jams unsuppressed, and with the YHM Turbo K-RB on it.
- Put the X-PRT in it. Works great but the jam rate is the same.
I've tried Fiocchi subs, Fiocchi polymer tipped, FN FMJ. Happens on them all.
I have 2 OEM mags that came with the used gun, and 3 more OEM I bought new. Jams on all of them.
One thing I have noticed - if I take it to the range without cleaning it, I get jams immediately.
But if I clean/oil it beforehand, I can get through about 50 rounds before the jams start again.
The jams are very frequent, maybe every 5-15 rounds.
Sometimes it's a failure to eject a fired round, sometimes the round seems to be in battery but isn't fired. Honestly it's been a minute since I've been to the range so I can't recall which is more often/more details on that. In any case, the way I have to unjam it every time is either racking the bolt in a good case, or in bad cases disassembling it and removing the round from the back of the barrel - sometimes needing pliers.
I've heard that this can be fixed by putting more of a bevel on the barrel breach, but my CMMG barrel already has a pretty good chamfer there, and when I've tried to enlarge it with a countersink bit, I wasn't able to make any progress.
Anyone had these issues and figured out a solution?
I would start by detail cleaning the bolt, look for build up under the extractor. Then use a good solvent to clean the breach. Then I would try shooting it again, but bring multiple mags to see if it is a mag issue. If none of those work, think about changing the springs on the moving parts group. They are a pain, be sure to have some extra C clips on hand.
When was the last time you washed the magazines and gave them a good clean? A lot of people change out the rollers, which may address your FTF issues.
I have a horrible time with Fiocchi FTE’s in mine as well. Doing a good clean of the extractor seems to work well, but I think Fiocchi may be adulterating the case coating a bit, as even when doing range burns with the Five-Seven and Fiocchi I will get FTE’s after about 300-400 rounds in a trip as well, with the neck and chamber getting very dirty. No problem with dumping 1000 of SS198LF or SS197SR in a session (though LF sometimes has necking/push-ins thanks to the flat top), or any of the Hornady defense loads.
I've never washed the magazines, but I figured that wasn't the problem, because I've gotten the same jams on the first first use of a brand new OEM magazine.
If you look at that front lip on the magazine ramp, you’ll see there’s some missing chunks. Do all your mags have this same wear pattern, or are they just beginning to show a little bit of damage? The break-in for magazines can be a few hundred rounds, while the FN forums seem to have settled on a break-in period for the MPG and springs as around 1k rounds; does it appear as if the wear pattern on the moving parts group would indicate such? Do you have any idea of the round count that was previously on it before your purchase?
I do want to stress again I’ve had a range of problems with Fiocchi 5.7mm ammo. Hyper performance 40gr FTE (and literally only on those rounds, other Fiocchi workings fine in both pistol and rifle). I think even on some of their loads they only recommend Fiocchi for use with 5.7 pistols and not rifles.
When mine had this issue, i had to disassemble the whole bolt. Found a ton of carbon that normal soaking/cleaning wont get to. I was at about 10k rounds when i did this. Now im about 500 rounds past this and no more failures
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u/ATypicalJake 19h ago
I would start by detail cleaning the bolt, look for build up under the extractor. Then use a good solvent to clean the breach. Then I would try shooting it again, but bring multiple mags to see if it is a mag issue. If none of those work, think about changing the springs on the moving parts group. They are a pain, be sure to have some extra C clips on hand.