Whos bolt is this?

[supercorndogs]

I was assuming I cracked this bolt a couple years ago looking for velocity with my grendel with 8208 and 123s. I also bought it used with a grendel barrel. I put it in my 6 arc while i was waiting for a bolt and it broke it.

When I started looking closer I wondered about the structure of the steel. It looks diffrent to me in the rusted areas where it's been cracked for a while, presumably. Does this diffrent look of the metal (appearance of larger grain structure) represent a soft spot?

 

[oldrifleman]

Interesting grain structure! The discoloration may be lubricant that Infiltrated a crack or attached after the fracture occurred. What interesting is I don’t see the tell tale smooth area I associate with a stress crack growing.

 

[supercorndogs]

Some of the discoloration is lube some i am pretty sure is rust. You can see the distinct diffrence in color. They look quite diffrent under the microscope. You can see the powdery crystals growing on the rust. It looks alot better to the eye than my picture throught the microscope. Lol.

The wife was bugging me that I should have gotten microscope I could plug into a computer screen. Lol

 

[oldrifleman]

Some how I missed the last two pictures . Yeah there were some cracks that let go. Don’t know whose bolt it was, but I wish I did.

 

[supercorndogs]

I forgot i have a broken 7.62x39 bolt I could look at too.

 

[Ledzep]

I believe Maxim does the rings on the body like that.

 

[Rocketvapor]

Could you estimate the depth of heat treat?

 

[Im2bent]

The wife was bugging me that I should have gotten microscope I could plug into a computer screen. Lol

I bought one of these from Amazon 180 bucks it's insane for the money

 

[supercorndogs]

I bought one of these from Amazon 180 bucks it's insane for the money

Pretty cool. More like a magnifying glass or jewlers loop than a microscope. The pictures in the first post represent the lowest magnification on my microscope. These are just zoomed in with a phone. Found my broken 7.62x39 bolt. I don't have the broken lug to set up on a slide. Grain looks way diffrent.

 

[supercorndogs]

I believe Maxim does the rings on the body like that.

I am.pretty sure that was it. All I could think of was mega and I knew it wasn't it but started with an M.

 

[bobke]

Not positive, but think Lilja used Maxim bolts when buying a new barrel and getting a headspaced bolt.

 

[supercorndogs]

I bought it used on here with Saturn 18" barrel a long time ago. I sold the barrel because it was tough on brass with its mid gas system. Who knows. It's not like it's a rare occasion for one these to break. I just thought the look of the metal and break was interesting.

 

[bfoosh006]

Sure looks like a Maxim bolt.
https://www.maximfirearms.com/online-store/complete-6mm-arc-advanced-rifle-cartridge-bolt/

 

[supercorndogs]

"Shot peened" Would that explain the different grain structure I see with my microscope on the outside layer?

 

[LRRPF52]

I believe Maxim does the rings on the body like that.

Yup. It’s a Maxim. I have at least 2 of those, including the one in my 17.6” Lilja barrel Grendel.

I’ve been shooting the 17.6” Grendel with that bolt for the past 10 years quite regularly. The load development I have done with that carbine exceeds most people’s normal shoot schedules, though I don’t do high volume CQM burn-downs with it.

I feel like I’ve been trying to break Grendel bolts all these years (since 2009).

If anything, the 12” CLGS suppressed should have done it already, as I’ve been shooting it for 7 years.

I have broken 5.56 bolts before running compressed high volume CQM schedules.

 

[M_R_Woodard]

It is a Maxim. I'm the one that sold it to you. It came with the barrel from Satern and I put less than 100 rounds on it.

 

[supercorndogs]

That is kind of disappointing. Probably less than 1500 rounds on this bolt then. Not as disappointing as the lifetime guaranteed 7.62x39 bolt pictured. It lasted about 50 rounds and the company guaranteeing it went out of business faster than I could ask them to replace it. LOL

I guess I will se how long my faxon bolts last. One has already destroyed two soft rainer UM barrel extentions. I was going to retire it but after putting it under the microscope I didn't see any reason not to use it. Hell those Velveeta cheese barrel extentions didn't even take the finish off the lugs.

 

[Cascade Hemi]

I bought it used on here with Saturn 18" barrel a long time ago. I sold the barrel because it was tough on brass with its mid gas system. Who knows. It's not like it's a rare occasion for one these to break. I just thought the look of the metal and break was interesting.

If it's hard on the brass it is hard on the bolt. AA undercuts the opposing center lug to mitigate stress on the extractor adjacent lugs.

The rush of new ARC buyers has me chuckling. It won't be long before the flood of "why is my bolt broken?" threads. It's probably a good time to be a Grendel bolt manufacturer.