I started building a new upper and am having an issue with the gas tube. It is protruding too far into the upper, preventing the BCG from going all the way forward. I tried 2 separate BCG's from known working rifles to check.
I double-checked the roll pin is in the correct position (not in front of the tube). I took a few measurements and was hoping someone could measure some of their parts to confirm if something is obviously out of spec.
This is a carbine length gas system.
Gas tube is 248.5mm long and 243.5mm from center of roll pin hole to BCG end.
Rear of barrel extension to rear of gas block is 199mm.
Rear of gas block to center of gas block's roll pin hole is 17mm.
Gas block OD at rear is 4.59mm.
Other notes:
Barrel was pre-drilled for a gas block roll pin. The gas block is seated against the barrel's shoulder and pinned in the pre-drilled spot. This appears to be in the correct position.
I removed the roll pin and put the BCG in the rifle. I pushed the gas tube as far back as it would go, and the tube's roll pin hole is still forward of the gas block's roll pin hole.
I don't have another carbine length rifle to measure against, my others are pistol and midlength. If someone with a carbine system could measure, that would be great!
If I'm missing something obvious, please let me know as well.
*EDIT* I have spoken to both the retailer and the manufacturer. The retailer was great and took some measurements of his stock of the same parts. His and mine matched. I am still awaiting resolution from the manufacturer.
*UPDATE* The manufacturer requested the upper to look at and I sent it to them. They dropped a BCG in and it test fired fine. They sent it back to me. While they had the upper, I bought a new BCG. When I received the upper back, the new BCG dropped right in. The other 2 BCGs from the other rifles still don't work. I'm not sure why those don't work, but I now have a working rifle with the new BCG, so I guess I'm good now.
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