12-31-2016, 07:18 PM
Grendel bolt length is 2.810"
Face depth is .136" (-.003" allowable)
Metallurgy is guarded by different vendors, but generally a certain type of 9310 alloy with certain heat treatments, shot peening, MPI, destructive testing of a certain % per batch.
There is nothing the consumer can really do other than check 2 of these dims, so it's best to source parts from reputable manufacturers and brands.
Nobody has done more testing than AA, and AA tests things that most 5.56 manufacturers aren't even aware of, since 5.56 is so well-vetted over the last 6 decades.
We've had some vendors that entered the market with really good bolts, then on subsequent production batches, something dropped in QC or specs and they no longer were holding up, especially looking at bolts and extractors.
I know AA works hard to maintain their standards with bolts and extractors, which is an endless battle with machine shops, kilns, and finishers.
The AA Hard Use bolt has a totally different surface treatment than most bolts on the market, as well as some external features that distinguish it from the rest.
I've had zero problems with standard AA bolts over the years, running thousands of rounds on them.
I'm also having no problems with the first batch of Underground Tactical bolts that PF used, with their own sources extractors that were nitrided, but it appears that something changed for the worse with Underground. Don't know what happened, but such is life.
Face depth is .136" (-.003" allowable)
Metallurgy is guarded by different vendors, but generally a certain type of 9310 alloy with certain heat treatments, shot peening, MPI, destructive testing of a certain % per batch.
There is nothing the consumer can really do other than check 2 of these dims, so it's best to source parts from reputable manufacturers and brands.
Nobody has done more testing than AA, and AA tests things that most 5.56 manufacturers aren't even aware of, since 5.56 is so well-vetted over the last 6 decades.
We've had some vendors that entered the market with really good bolts, then on subsequent production batches, something dropped in QC or specs and they no longer were holding up, especially looking at bolts and extractors.
I know AA works hard to maintain their standards with bolts and extractors, which is an endless battle with machine shops, kilns, and finishers.
The AA Hard Use bolt has a totally different surface treatment than most bolts on the market, as well as some external features that distinguish it from the rest.
I've had zero problems with standard AA bolts over the years, running thousands of rounds on them.
I'm also having no problems with the first batch of Underground Tactical bolts that PF used, with their own sources extractors that were nitrided, but it appears that something changed for the worse with Underground. Don't know what happened, but such is life.
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