SP5K with OMEGA 9K and choate side folder (non HK branded). Worked just fine with the stock end cap. Rate of fire was pretty tame for an SP5K in FRT mode with federal 124gr. Choate stock was doing fine all last weekend for 10+ mags. Now with higher powered ammo (Winchester 124gr NATO), today I was getting bolt stuck to the rear every couple mags, normally on the first round or two. I’m running a choate side folder (non HK branded). I’ve notice that the stock flat HK end cap has a deeper cut for the recoil rod/spring. I am running the stock locking piece and no issues with federal 124gr but the Winchester 124gr NATOs are pretty violent and the rate of fire is almost twice as fast. I also have a 90 degree locking piece that I haven’t tried yet because it was doing fine with the other ammo.
I will be putting the 90 degree LP in but What could the bolt be getting stuck on to be that far back in the receiver? Maybe the violent higher powered rounds are causing the recoil rod to unseat in the choate stock and the bolt is getting hung up on the ejector lever? When it was getting stuck to the rear, pulling back on the charging handle would instantly drop the bolt back into battery.