6.5G bolt

[Collk88]

I was looking at the maxim bolt, but now see that 65outfitters offers an ultrabolt. Any real difference between them? Price seems similar.

[LRRPF52]

I have several samples of Maxim and at least 1 Ultrabolt I think.

I also have several Monster logo bolts sold through the forum.

The Maxim bolts have several bands around them near the front of the bolt just before the lugs, and have a dark, glossy sheen to them that looks like nitriding.

I have used AA, AA Hard Use, PF/Maxim, Monster Logo, and some others I can’t think of right now dating back to 2009. I also have a complete LaRue 18” MLGS Stealth 2.0 rifle with the bolt LaRue uses.

There are some additional radii on the Ultrabolts as part of the design to increase lug root area with the bolt body, both cross-sectionally and when you look at the rear lug roots from the side.

Pretty much every reputable company making Grendel bolts is using AISI 9310 alloy, but there are different processes that can be used to tailor it for the application.

Dimensions can also be different, so you want a bolt with the .136” face depth and a reliable extractor, with a longer bolt tail to accommodate Mil-Std firing pins.

By moving the face depth to .136”, the bolt tail needs to be longer to set firing pin protrusion properly.

One of the most harsh configurations for any chambering in AR-15s is Carbine-Length Gas system, short barrel, suppressed.

I built 2x 12” 6.5 Grendels with CLGS, which have been shot exclusively suppressed since 2017, using Monster logo bolts before the Ultrabolt design.

The first 12” has been fed a steady diet of 107gr SMK on top of 8208XBR, after initial accuracy-testing with 123gr ELD-M factory ammo and 123gr SMK hands loads on 8208XBR.

The 2nd one has been fed 123gr Hornady American Gunner by the 200rd ammo can, 120gr Federal OTM Match, 90gr TNT Federal, and 123gr ELD-M.

Both of the 12” blasters have been choked with the Bootleg Adjustable Gas Carrier to prevent excessive cyclic rate, which helps keep the bolt locked longer and less-prone to torsional (rotational) lug loads while unlocking.

Another harsh barrel length/gas system configuration is 18” MLGS. I have the most round count with that set-up, across several different Grendels, but mainly my 17.6” Lilja Wasp profile build. I have a Maxim bolt in that.

I’m getting close to surpassing its round count with the 12” though.

I personally have not experienced any bolt or extractor failures shooting 6.5 Grendel since 2009. Others have on occasion.

I have only broken 5.56 bolts after abusively-high round counts compressed into short periods of time, and only after 10,000 rounds.

Based on what I see with the Ultrabolts, I’m leaning on buying them for any future needs. It’s what I’m using for my 10.5” Grendel pistol project.

[Collk88]

Thanks for all that info! What makes those gt/bbl lengths so harsh? The dwell time? I was considering an 18” rlgs, but now looking at the monster logo 16” mlgs. Is that length setup to be fairly smooth?

[LRRPF52]

Port pressure and/or dwell time.

Port pressure on CLGS is high.

Dwell time on 18” MLGS is pretty high.

16” MLGS with .076” port runs very nicely with an efficient carrier and sealed gas block.

18” Intermediate Gas System is really good as well.

18” RLGS is smooth, usually needs a larger port since dwell time is low, unless it’s suppressed.

I’ve had excellent results with 16” AA and 16” Lilja barrels, MLGS .076” ports.

The Monster logo barrels are cut with the same ports I think.

[Collk88]

Awesome. Really appreciate the info! Since i have your attention, do you have any experience with wilson combat barrels?