Testing Coned Breech Barrels for Proper Clearance
Recently we've had a number of customers wanting us to rework prefits for Coup de Grace actions due to the extractor dragging on the bolt face. In May 2024 alone it was 5 barrels, 3 of which came from the same Sniper's Hide member. Exactly 0 of them really had a problem, but all 5 were tested incorrectly and showed false positives.
Fortunately, shooters are looking out for other shooters and telling them that it's something to check. Not everyone is cutting these particular prefits properly. Unfortunately, the way that people are being told to check them is erroneous and leading to a bunch of false positive alerts.
- Anyone who got a barrel from PVA after the first 20 in March 2023 or so that we made doesn't have this issue and it's a false positive. If the serial number on your barrel starts with "2309xxx" or higher you don't have an issue, I'm sure of it.
- Without following the instructions below you can make a barrel look like it has a problem 100 out of 100 times.
- Below is the proper method for testing to see if the extractor is dragging.
Background:
The geometry of the ARC Coup chamber cone was updated early on in the production actions due to an extractor geometry change and that was causing actions to drag the extractor across the bolt face when the bolt was being closed. It leaves a characteristic mark as seen in the photo attached.
Discussion:
Barrels must be tested under one of two conditions: With a GO gauge in the chamber OR with a trigger installed and set to SAFE. These two conditions are critical because otherwise the clearance in the actions will allow the bolt nose to come forward approximately 1/32" and it will ALWAYS touch the breech face. This is not unique to the Coup. It will do it on a TL3, Origin, Defiance, Impact, Lone Peak, etc. If you take off a barrel from a TL3 that's been on there for a few hundred dry fires you can see a shadow of the bolt face on the breech face. It doesn't mean anything is wrong, that's just how these machines work.
Proper Test Procedure:
1) Sharpie the chamber cone and Install barrel
2) Put in a dummy or GO gauge
3) Close the bolt several times on a chamber that "loaded"
4) Remove barrel and look for the mark that is shown in the first photo.
Alternate if you don't own a GO or can't make a dummy round for some reason:
1) Same as above
2) Install trigger and put the trigger on SAFE
3) Same as above
4) Same as above
Important Detail: If you test on an empty chamber without a trigger on SAFE you will be able to create a swipe mark every single time you attempt it on a Coup. It's a false positive.