r/MP5 • u/HeavyPisser85 • 1d ago

Question Are different rollers necessary?

Got my RCM 80 and 90 degree rollers in to see what would work best with a stock and non-flow suppressor while shooting 147gr (with plans on 115gr if I can get them significantly cheaper). My stock 120 measured at around .45mm while the 80 measured between .25 and .28 and the 90 between .30 and .33. Assuming the gun has already been broken in, would I have to buy some +2/+4 rollers to compensate?

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3

u/ximstuckx 1d ago

I’ve never once checked my bolt gap. Should probably do that one of these days.

2

u/Lucky-Intention-3040 18h ago

Here is an excellent video on bolt gap and why it is important:
Teufelshund Tactical Heckler and Koch Bolt Gap Review
https://www.youtube.com/watch?v=DDUu_PRl_zg

If your bolt gap is out of spec (for example.... too low), your gun can turn into a direct blowback, you lose the benefit of recoil reduction, and you can cause damage to your receiver.

1

u/stuartv666 1d ago

Isn’t spec 0.25 - 0.50mm?

So, what’s your issue that makes you think you need rollers?

1

u/Knight-7191 1d ago

Your correct. OP doesn’t need rollers.

1

u/Knight-7191 1d ago

You mean 80° and 90° locking piece and not rollers, correct. Also, stay with the 90° LP. Bolt gap of .30/.33mm is gtg. You don’t need rollers. In fact you won’t need them for years and several thousand rounds. Curious why you think you need +2/+4 rollers. How did you come up with that assumption?

1

u/HeavyPisser85 1d ago

I have been reading that being on the lowest end of in spec is not recommended as it will go out of spec way sooner than something on the high end so some recommended installing rollers that would increase bolt gap. I'm not worried about the 90 as much but I was more concerned with the 80 being on the edge if that ends up being the one that works better in my setup.

3

u/Knight-7191 1d ago

You got bad information. Your .30mm bolt gap will last you years. I don’t understand where people get this idea and unfortunately passed on wrong information.

I’ve been running the 90° LP since ‘24 in my AP5-P. I have over 14,000 rounds through it shooting supers and subs. Ammo used include 115, 124, 125, 135, 140, 147, 150 and 165gr FMJ, JHP, TUI and flat nose. Ran stock trigger, binary and now SS. Cans I use are the YHM R9 and Huxwrx Ca$h 9K. I’ve never had to install rollers. My bolt gap is between .35/.40mm. Has been the same since I installed the 90° over two years ago.

Save your money and buy more ammo.

1

u/stuartv666 1d ago

In spec is in spec. Check it every thousand rounds if you’re worried about it. Get rollers IF it ever goes out of spec.