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Discussion Starter #1
Upon checking my bolt gap on an MP5 (all german clone) that I purchased a while ago but haven't fired yet, I found it to be around 0.10mm (very tight). I installed some +4 size rollers (2 lines on them) that I purchased from RTG, and my bolt gap didn't even rise to 0.2mm. The bolt carriers/bolts/and locking pieces are basically brand new, but I did trade them out to see if it made a difference. I also took the rollers out, and reinstalled them (it was my first time- and I figured I could have messed something up (although it is a very easy process). I did measure the rollers and compare them to the factory rollers, they are 8.04mm (as they should be).

I am out of ideas, does anyone have any tips?


Thanks
 

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Teufelshund Tactical
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Armorer's training shows that you have done the correct procedures. When all those steps have failed, replacing the barrel is the option, but all of this is usually done after a long life and lots of rounds, not a new build.
 

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Discussion Starter #3
Thanks for your help Marine- I should have clarified that the gun was purchased "used"- the seller never told me about the bolt gap (and I didn't know enough to ask). Unfortunately he wasn't truthful about a few things- but still I should have known enough to ask about the bolt-gap.
 

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HK Shooting Team
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you said it is unfired by you.....don't get your panties in too big a wad.....may not even have any issues....if I were you, I'd restore it to original condition and see if you have any issues before you change anything....give it a try and report back
 

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As bystok says it may be very shootable.. try it first
 

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Discussion Starter #6
It may be shootable, but would this cause damage to the gun?
 

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Are you sure you are measuring .10mm or .010 inch??? Standard bolt gap of .010 inch would be on the small side of good. a +4 roller is a +.0015 inch increase, so you will not see a big jump in gap. Not jumping on you, just checking.
 

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very well could

you can get dimples in the rear of the receiver with the rollers hitting with too much impulse from unlocking too early, looks damn ugly too and I don't know how easily it is fixed.

I would send this off to one of the builders and have them repress a barrel into the weapon or check the trunion
 

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Discussion Starter #9
No offense taken Eldos, I was hoping someone would see something I was doing wrong that could be easily remedied- it was mm. I was using the very thin gauges to pass the feeler through. It is looking like I am going to have to send this off.
 

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H&K Certified Armorer
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Skorit, you've been around long enough that most of this you already know, but for the benefit of some of the newer members or those guests just browing the forum...

.1mm is about .003" which is below HK's recommended operational range. While the gun may shoot just fine, initially, wear factor will increase as well as potential for premature parts failure and other damage.

If it is a German kit gun, then it was a pretty worn-out gun as the lowest MP5 kit bolt-gap I have seen is .011".

That said, there are many variables that can cause a premature bolt-gap shrinkage. If the orginal MP5 was properly mainiatained, then a .003" bolt-gap would indicate the potential need for a barrel replacement as the barrel may be shot out. A set of guage pins will help you idetify if the barrel need replacing.

For starters however, try a new locking piece as the shoulders do wear on them. Per HK's recommended proceedures when bolt-gap falls BELOW minumum:

1) Check barrel (chamber and bore) with HK go/no-go guages. You can use guage pins to check the bore. No real alternative for chamber.

Assuming barrel is within operational range:

1) Replace rollers
2) Replace LP
3) Re-press barrel
4) In some circumstances, replace bolt-head
 

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Discussion Starter #12
Sent off to Dakota Tactical for inspection and servicing today! I will let everyone know what he finds.
 

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Discussion Starter #13
Looks like the barrel needed to be repressed, and an oversized pin placed. Special thanks to Joe at Dakota Tactical for his exceptional communication and turnaround on the gun. Everything looks great--Highly recommended!
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