12-15-2017, 05:13 PM
Before I even allow a barrel to go near an upper receiver, I make sure the chamber and bore are clean and clear.
I then take several factory loads and dummy cartridges that I have to see that they will fully chamber and fall free from the chamber.
I use a stripped bolt to test that they fully chamber and that the bolt will rotate.
I remove the bolt, then see if the cartridge will fall free.
If the cartridges get stuck, I take one of the dummies with a black-colored ogive, and see if the lands are being jammed.
For the few barrels I've had come through that were like that, I have always been able to see the rifling marks on the ogive, indicating a short throat. I can think of 3 barrels off the top of my head that were like that. The rest have been fine.
Some chambers on economy-grade barrels have tooling marks and imperfections all inside the chamber, so when the case obturates to the chamber wall, it has more purchase strength to the wall than the BCG and extractor can overcome, so the extractor slips off the rim and you get a FTExtract stuck case malfunction.
These chambers either need to be finish-reamed and polished or just polished, depending on how they do with the chamber check with cartridges.
Was this happening with factory ammo or hand loads, and what type of ammo?
I then take several factory loads and dummy cartridges that I have to see that they will fully chamber and fall free from the chamber.
I use a stripped bolt to test that they fully chamber and that the bolt will rotate.
I remove the bolt, then see if the cartridge will fall free.
If the cartridges get stuck, I take one of the dummies with a black-colored ogive, and see if the lands are being jammed.
For the few barrels I've had come through that were like that, I have always been able to see the rifling marks on the ogive, indicating a short throat. I can think of 3 barrels off the top of my head that were like that. The rest have been fine.
Some chambers on economy-grade barrels have tooling marks and imperfections all inside the chamber, so when the case obturates to the chamber wall, it has more purchase strength to the wall than the BCG and extractor can overcome, so the extractor slips off the rim and you get a FTExtract stuck case malfunction.
These chambers either need to be finish-reamed and polished or just polished, depending on how they do with the chamber check with cartridges.
Was this happening with factory ammo or hand loads, and what type of ammo?
NRA Basic, Pistol, Rifle, Shotgun, RSO
CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
www.AR15buildbox.com
CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
www.AR15buildbox.com