Thank You Sir!
Thanks,
That has given me lots to consider, and some excellent info! Most likely the Alexander Arms bolt will be the way I'll go.
And I'll get on the tutorial on lapping the lugs. I've done several bolt actions, but never an AR.
Again, guys you've been a great help!
Wayne
QUOTE=LRRPF52;2985031]Alexander Arms
6.5 Grendel Hard-Use Bolt Assembly - Bolts and Extractors by Alexander Arms
Maxim Firearms
Complete 6.5 Grendel Bolt and Carrier Group AR15 ? M16 | Maxim Firearms
Underground Tactical
6.5 Grendel Bolt - Assembled - Underground Tactical Arms
These other two have just come online with excellent 9310 Grendel bolts. Alexander Arms has been offering 9000-series Grendel bolts subjected to stringent quality control for years now, and their standard bolt takes abuse very well too. I've been doing pressure ladders on mine since 2009, and my mass-produced loads are right around the SAAMI MAP.
At least 2 of the sources I listed above, if not all 3, are using the best available 9310 steel, not the generic type. Think of what industry requires the highest standards in materials science, and you will come to the right conclusion. I have and would recommend buying from any of the three I listed above.
Some of the 8620 bolts from one of the makers mentioned in this thread have been breaking, and I personally avoid 8620 even in 5.56 NATO or my .223 Wylde AR15's.
The deeper .136" (-.003" max, no + allowed) bolt face depth goes back to Colt's RDT&E of the 7.62x39 cartridge, which they produced a Sporter II model of in the late 1980's. Their engineering team determined that a deeper bolt face recess was the better route to go in order to create enough extractor mass on the lip for the much thicker 7.62x39 case head rim, when compared to the very thin .223 Remington and 5.56 rims. Since the 7.62x39 SAAMI MAP is 45,000 psi, and Colt had forgotten more about materials sciences than 99% of the AR15 copycats would ever know, they looked at the metallurgy of the reduced mass bolt, and determined that with their stringent QC, shot-peening, MPI, etc., that they had a viable solution, and the guns worked out well.
When other companies started cranking out "7.62x39" bolts, they just figured, "Hey, we just machine the bolt face wider when making these bolts, and we're good to go." Combine that with shooters using Warsaw Pact .311 ammunition in .30 caliber bores, and the pressures went up. A lot of guys with registered lowers wanted a cheap blaster ammo bullet funnel, and broken bolts become synonymous with 7.62x39 AR15's.
Alexander Arms has worked very hard to find a viable balancing point with the 6.5 Grendel, and the metallurgy plus dimensional tolerances of the bolts and extensions are critical to that. Since the bolt face is recessed, you have to adjust the bolt tail so that your firing pin protrusion is consistent, so a properly-built Grendel bolt will be 2.810" vs. 2.800" like standard AR15 bolts. This allows use of common AR15 firing pins, and nice dimpling of primers.
When building an alternate caliber in the AR15, it becomes even more crucial that you start with a square receiver face, and balanced lugs to the extension (lapping the lugs). There are excellent tutorials here on the Hide to guide you through these procedures if you are unfamiliar with them.[/QUOTE]
