Gun: FN PS90 converted to SBR by TROS (incredible job), using Octane 45 silencer
Issue: Sevenish rounds out of 150 would not chamber fully, causing a stoppage mid-magazine
I've been shooting my PS90 carbine since I bought it in August of 2015 with probably 1500 or so rounds through it now (99% SS197). My SBR stamp came back in October 2016 and TROS did the conversion. The OEM barrel, both pre and post SBR conversion shoots unbelievably well. I was even hesitant to have it cut and threaded because it shoots such nice groups. Luckily, the conversion and subsequent silencer use have had absolutely zero impact on group size. Up until yesterday, the only jams I have had with it have been when I had it on the bench and shot enough to where the casings filled up the ejection port (obviously my fault on that one). Yesterday I probably had seven jams in the 150ish rounds I put through it which was a little disappointing considering this is my absolute favorite gun currently. All of them were the same, squeeze the trigger after having just fired another round and CLICK. I remove the mag and find the bolt forward on a live round that is not all the way in the chamber. Keeping the gun pointed down range I rack the charging handle all the way and about half the times I had to do this the round would still not fully chamber nor would it extract so I had to use a rod to poke it out. Upon inspecting a couple of the rounds that did this, I could not for the life of me see any visible difference between the problem round and the other presumably normal rounds. The ones that did chamber after racking the charging handle a couple times then fired and extracted fine.
One other thing I had happen was a round that I fired didn't even cycle the action... but it still grouped with the others!? It was not one of the ones that had chambering issues.
Now, I have read a LOT about people not trusting SS197 due to consistency issues but up until yesterday I hadn't experienced any of them first hand. I'd hate to just write it off as an ammo issue if there really is something underlying with the gun itself. I have accumulated a lot of SS197 so if it is the ammo I would really hope the whole lot doesn't have this trouble.
Things I have tried/looked at:
*Gun was lubricated with a light coat of 10w30, not running bone dry
*Barrel still rotates perfectly freely
*Tried the only ten rounds of SS198 I had with me at the time, no stoppages (but, again, it was only ten rounds)
*Manually manipulated the extractor, operated fine
*Pulled and cleaned the moving parts group including bolt face, pretty uneventful just a little carbon
Edit: *Inspected and cleaned chamber, nothing I could see and it didn't even seem that dirty
Any ideas please fire away, I'd love to hear what you guys have to say. Thanks!
On a completely unrelated note, yesterday was the first day I was able to shoot it with the new Holosun HS503GU sight with 2 MOA dot and 65 MOA circle. All I can say is wow, complete perfection for this gun IMHO. The height over bore (I'm using the standard peep sight rail) was a bit of a challenge when it came to trying to make reliable hits on small targets at close range using a standard micro dot because I had to sort of guess how high to aim. The bottom of the 65 MOA circle correlates EXACTLY to the POI at 10 yd. I was shooting quickly at multiple small 1" targets at ten yards and did not miss a single one, it was boringly easy As long as the sight winds up holding zero and such, I will be adding one to the Tavors as well.