Extreme budget 6.5 Grendel build. How cheap can you build one?

[Christopher67]

That is the question of the year for me. Anderson seems to have created a unique chamber bolt combination. SAAMI 6.5 Grendel chamber use .136 bolt face depth and Anderson says their bolt is .135 which has been verified by a forum member. Another member posted a response from Anderson stating their chamber uses a compound throat with .295 neck. The 6.5 Grendel SAAMI chamber uses a compound throat with .300 neck. Unless someone does a cast of Anderson chamber it's anyone's guess what the specific dimensions are used.

The Type I designation is used by Black Hole Weaponry to differentiate between barrels chambered for 7.62X39 bolts (.125 bolt face depth) and Type II for barrels chambered to use 6.5 Grendel (.136 bolt face depth). Up to Anderson being released barrels that shot 6.5 Grendel ammunition used either 6.5 Grendel bolts or 7.62X39 bolts.

The other confusion arouses from Satern/Liberty using a different chamber design called Grendel II. What does Anderson do but create a new named chamber called Grendel 1. This is why so many people suggest staying with the known design submitted by Alexander Arms and Hornady and accepted by SAAMI.

Is .001 difference in the bolt face depth significant, all depends on each individual chamber. The SAAMI certification of the 6.5 Grendel ammunition and chamber specs was supposed to help off set all this confusion. Obviously market forces, manufacturing capacity and ignorance are coming into play with the 6.5 Grendel.

I truly appreciate your info, think I'll stick with AA.

[DeoreDX]

Unless someone does a cast of Anderson chamber it's anyone's guess what the specific dimensions are used.

How much does the brass conform to the chamber one fired? Would measuring my used brass give us a good indication of the throat dimension?

.295 throat matches the 264 LBC-AR

http://www.thefirearmblog.com/blog/2010/03/26/264-lbc-ar-a-grendel-clone/

[diddlyv]

That is a good question. The answer is probably depends. The brass is most elastic at 5he first firing and will shrink back the most. Each successivend resizing and firing will work harden the brass and it will shrink back less. I have no idea how much smaller than the chamber neck dimension the first fired brass will be. As it work hardens the brass neck will come successively closer. Cerrosafe chamber cast is probably the best way to tell.

Ar15precission hawks their extreme duty bolt as being .135 vs the standard .136

[DeoreDX]

This thread from Snipers Hide has some information on brass measurement from a 264 LBC chamber with the .295 throat. Claims the brass measures .292-.293 after it has been fired.

http://forum.snipershide.info/showthread.php?t=79182&p=1132591&viewfull=1#post1132591

I'm measuring just under .300 on my once fired Hornady brass using a micrometer. The battery is dead on my digital Mitoyo's so I went with the micrometer instead of the calipers. Throat is slightly oblong on my 3 spent cartridges where it looks like the case hits the brass deflector. Measurement will go from .298-.300 depending on how I turn the cartridge in the micrometer. I can't imagine it having a .295 chamber neck with the measurements I've taken.