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Posted: 7/2/2014 11:58:19 AM EDT
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I recently bought a new PTR 91. I wanted to buy spare parts for it and this included two HK BCGs. The bolt heads, LP, firing pins and springs were all new in the factory package. The bolt carriers were both used from HKParts. One was a standard auto and the other was refurbished with tungsten inserts. Upon checking the bolt gaps I discovered something I consider strange. One BCG gaps .20mm, the other is less than .15mm and the factory PTR BCG is .40mm
It is my understanding that the carrier itself should not change the gap and all other parts were new factory HK. To check the gap I installed the BCG, locked the bolt open and then let it charge under the power of the spring. I then pulled the trigger to drop the hammer on the empty chamber. Please correct me if that is the wrong method. While the factory PTR BCG is in spec, I want to have the other two in spec also. I haven't yet tried installing larger rollers, but I am wondering if something else might be going on since all the parts besides the carrier itself are brand new and it's my understanding the gap gets smaller with use. Thank you very much and I look forward to reading all the replies. |
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You are at the low end of the "in-spec" spectrum, which is .004-.020" Surprising your HK BCGs are out, but who's to say it's not the PTR receiver that is out? Either way it doesn't really matter. As already said just use proper sized rollers to get your bolt-gap within that range and you'll be fine.
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