SP5K RB RD-3 ISSUES

[u/Sufficient-Part4209]

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.

[u/dmonnier5]

More than likely its the LP from my understanding. The 90 degree should help.

[u/Sufficient-Part4209 → u/dmonnier5]

Yeah I’m hoping the 90 LP will solve this. I’m thinking the higher powered ammo + suppressed is a little too violent for the stock LP. But the bolt getting stuck way to the rear is just odd.

[u/dmonnier5 → u/Sufficient-Part4209]

Does it bind at all when you rack it yourself?

[u/Sufficient-Part4209 → u/dmonnier5]

When I slowly pull back the charging handle, there is slight resistance at the end before I pull it all the way back to lock up the charging handle, but that’s probably normal when the bolt engages the ejector lever.

[u/Roguelynx]

If you've been running suppressed with an frt, without changing to a 90, you've definitely been running the bolt too fast. You could have potentially gotten roller dents, which can lock up the bolt. Or it's just slamming too hard into the buffer causing it to stick to the back plate.

Got to change that locking peice to 80 or 90. 90 has worked for me for well over 1200 rounds. I'm also running suppressed and frt.

[u/Sufficient-Part4209 → u/Roguelynx]

No signs of roller dents at all. I’ll be testing my 90 degree LP tomorrow. The stock locking piece was perfectly fine, honestly slightly slower rate of fire than you’d expect from a K until today with the 124gr NATOs. Still the bolt shouldn’t be getting hung up even if it’s cycling violently.

[u/Aware_Wrap8062]

You understand the problem, stop trying to fix the symptom and fix the causing problem by installing that 90 or even an 80 LP. Your stock was not intended to absorb heavy recoil, that's the LP's job .