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Discussion Starter #1 (Edited)
In preparation for a suppressor I started looking for a German #28 LP. I suppose I was put off by the crazy price of that part and decided to try the RCM part.

Here are pics of the 4 LPs I own.

Top is the Zenith MKE 110 degree LP that came with a Z-5P. Next one down is used German 100 degree LP. Then the HK Parts marked as PDW, then the RCM.



Measured Bolt Gap:
MKE 0.33mm
HK 0.35mm
RCM 0.60mm
HKParts 0.30mm

Left is RCM, right is HK Parts.



I had to buy -2 rollers for the RCM LP (which got me a 0.50mm Gap). I shot with both 147gr and 124gr, unsuppressed. I did have 2 malfunctions with 147gr but overall it functioned ok. 124gr was good.

Too much time on my hands and really hoping to stick with standard rollers, I decided to spend $35 and try the new HK Parts #28 LP when I noticed it on their website. Have not shot with it yet.

QUESTION:
Should I stick with the RCM LP and -2 roller at maximum gap?
Shoot the HK Parts at 0.30mm gap with standard rollers?
Or buy +2 rollers and the HK Parts for ~0.40mm Gap?

Pros or cons for each of the above setups appreciated! Hopefully the suppressor gets out of jail in the next few weeks.
 

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Rcm. With optimum gap. Happy with mine
 

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I have both h&k and rcm both in spec with std rollers. Both work fine for me.
 

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Discussion Starter #6
Let me update, forgot about this thread.

To re-iterate, I should have been happy with the RCM #28 and the -2 rollers @ 0.50mm gap, but I am glutton for punishment.

After some deliberation, I decided to give the HKP #28 the nod and bought +2 rollers to try and increase the gap from ~0.28-30mm. Gap went up to ~0.33-0.34mm, which is only an increase of about 0.05mm and not the 0.10mm I was expecting. But whatever, I have shot about 100 rounds suppressed and it is working well.

I have since bought and installed a spare bolt (F Bolt) and the bolt gap stayed exactly the same as the MKE bolt. Surprisingly, the MKE bolt "looks" just like an F bolt.

If anyone has a German #28 laying around, lemme know. That would make most of my moving parts German, although I can't really complain about the MKE parts. I will say the SP89 carrier did make charging easier and smoother.

I think this was the first time I shot the Obisidian in long config. Shooting both the backstop and steel. I will say that in real life its much louder than this cellphone video portrays, but not enough to bother the neighbors.


Gonna keep the +2s rollers, HKParts #28, and F bolt in there and will check the gap every 500 rounds to see what happens. This is my first roller gun so I am enjoying tweaking on it!
 

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Discussion Starter #7
Ok smart people, why is it that 99% of the threads I have read say that a bolt gap of 0.25mm means less recoil/less carrier speed/quieter versus 0.50mm gap?

And then there was 1 post by a builder who stated the exact opposite...

http://www.hkpro.com/forum/hk-refer...does-bolt-gap-effect-way-gun-functions-2.html

And it seems like people shoot for higher gap vice lower gap. I get that gap shrinks, but we are talking thousands of rounds and rollers are cheap.

I am bored, so I may try to setup at the ~0.50mm gap and see how it feels. I have shot for the last month suppressed with Lawman 147s at a gap around 0.33mm. Hopefully I can tell the difference in recoil @ 0.50mm and report back. I will also look at where the brass goes, but it has been eratic so I doubt it will show anything.
 
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