After 123 rounds???!!!

[Nukes]

Has anyone had a 6.5 Grendel bolt shear a lug after only 123 rounds?

I am flabbergasted.

The original LBC bolt sheared after shooting Wolf 120 gn MPT with a suppressor. The bolt was replaced with a second LBC bolt and a variety of loads followed, no suppressor, no pressure signs: 139gn Scenars with N540 to 28.0 gn (MAX 28.1), 123 gn SMKs with 28.3 gn 8202XBR (28.5 gn is MAX), then 24 rounds of the Wolf and a lug sheared.

Having seen other people's expensive guns explode with cheapo ammo, we never use cheapo ammo in our expensive guns. I didn't consider the Wolf ammo "premium," but neither did I think it was "cheapo."

Since the rifle has been properly and professionally headspaced, gassed, and reinspected, and the LBC bolt dimensions are correct, here's my differential diagnosis:

inherently weak design of the 6.5 Grendel bolt
poor metallurgy of the LBC bolts
bad lot of Wolf (?lot # 485.E30-1400693)

Other possibilities?

After the first bolt sheared, I ordered 2 LBC bolts and finally a regular AA and 2 hard use AA bolts arrived, so I am in a position to try the AA bolts.

[Drifter]

Was the receiver face squared? If the bolt isn't in correct alignment with the barrel, I believe some bolt lugs can be stressed more than others, as they are all not sharing the load equally.

[NugginFutz]

IIRC, didn't you send the entire upper to LBC, Nukes? I thought they'd given it a clean bill of health...

If you have any left, I'd change nothing but the bolt. Shoot the same ammo. Lord help ya, if you break the Hard Use bolt, though.

[Drifter]

Also, were your listed max loads determined by you (starting low then working up, looking for pressure signs, using a chronograph, etc), or simply referenced from a manual?

28.5gr of 8208 under a 123gr bullet is often exceeding max in my experience with numerous barrels. Using 8208, I usually stay below 28.0gr.

[bwaites]

I know of one that failed after less than 100 rounds of factory LBC ammo, but that was probably a manufacturing defect. 6 years or so ago, I tracked down info on every broken bolt posted here or on ARF.com, and all but the one above had broken with handloads.

Almost always in these cases, its because there is a bad extension/bolt match, where the extension and bolt aren't square to each other,most often exacerbated by near max handloads.

There is no doubt that the bolt is weaker than the 5.56 bolt, it simply doesn't have as much metal in it.

Although your posted max loads are correct, that doesn't mean those are YOUR barrels max loads. Your barrel may not tolerate anything close to max, especially if there is a bad extension, which has been noted to be an issue in many situations.

Its been a while since we had a batch of broken bolts, and it would be interesting to know if both were from the same batch, which might indicate a heat treat issue.

[Joseph5]

That sucks, my take home from this is to skip the Wolf ammo. If it is the metallurgy of the bolts nothing will help that except a correctly made bolt. It is good that you have spares. That was another take home lesson for me from this site. When I contacted Maxim firearms I ordered a complete BCG and a spare bolt. Now I am just waiting on the Lilja barrel. With the happenings in the last year and a half in the firearms industry due to unprecedented demand I have heard of more poor QC on many different firearms than I can remember any time previously. Or, maybe there aren't anymore issues than previously and the internet has just brought them to light. I once paid $1100.00 for a Kimber 1911 and the rear sight fell out of the slide on the first box of ammo. They couldn't understand why I was upset. Joseph

[cory]

...Its been a while since we had a batch of broken bolts, and it would be interesting to know if both were from the same batch, which might indicate a heat treat issue.

I don't think this is accurate.

Not long ago there was a thread here where a guy was having similar problems with an LBC bolt. I want to say he tried 2 more with the same sheered lug results. I believe he recently posted that he got an AA hard use bolt and the weapon is operating fine suppressed.

It was hypothesized in that thread that LBC was using 8620 for their bolts. I suspect that's what happened here.

[Nukes]

Was the receiver face squared? If the bolt isn't in correct alignment with the barrel, I believe some bolt lugs can be stressed more than others, as they are all not sharing the load equally.

I did not specifically ask that, but I assumed (yes, I know) that was done. Seekins receiver set and Krieger barrel built by Mark Gordon at SAC, that didn't seem like a question I needed to ask, but I will ask him tomorrow.

IIRC, didn't you send the entire upper to LBC, Nukes? I thought they'd given it a clean bill of health...

If you have any left, I'd change nothing but the bolt. Shoot the same ammo. Lord help ya, if you break the Hard Use bolt, though.

Only the bolt is LBC so I did not send the upper to them. I sent the rifle back to Mark only after the second LBC bolt failed.

Also, were your listed max loads determined by you (starting low then working up, looking for pressure signs, using a chronograph, etc), or simply referenced from a manual?

28.5gr of 8208 under a 123gr bullet is often exceeding max in my experience with numerous barrels. Using 8208, I usually stay below 28.0gr.

For this rifle I started 10% below the published MAX and used 0.1 grain steps up to MAX and not beyond. Obviously the lighter charges showed cute little primer dimples and the near MAX loads showed a real primer impression, but no cratering, piercing, or even wide flat primers. Reviewing our chrono data showed no worrisome plateau for the reloads and all of the 8208XBR loads (whether 123 Scenars, AMAX, or SMK) were 100-150 fps below the AA factory 123 gn Scenars.

...Its been a while since we had a batch of broken bolts, and it would be interesting to know if both were from the same batch, which might indicate a heat treat issue.

The replacement bolt packaging for the LBC bolt is with the rifle at SAC, but I do not recall seeing a lot# listed on the packaging or invoice.

That sucks, my take home from this is to skip the Wolf ammo. If it is the metallurgy of the bolts nothing will help that except a correctly made bolt. It is good that you have spares. That was another take home lesson for me from this site. ...

Before this happened I ordered another hard use bolt :-) Some of our long range matches have had shorter range (400-600yd) run-and-gun stages. Because the Wolf shoots about 1.5 moa (double the AA factory ammo) and the brass is lousy, I figured I'd shoot the Wolf and let the brass lay. Yeah, I know—I actually decided to shoot less accurate ammo for a match. Even though I am in the bottom tier of our group's precision tactical shooters (and there are also 5 nationally ranked people who are in our matches), I had perhaps unjustified confidence in overcoming the Wolf ammo :-)

Well, since I have 3 AA bolts available, I might try the Wolf ammo paired to an AA bolt.

I don't think this is accurate.

Not long ago there was a thread here where a guy was having similar problems with an LBC bolt. I want to say he tried 2 more with the same sheered lug results. I believe he recently posted that he got an AA hard use bolt and the weapon is operating fine suppressed.

It was hypothesized in that thread that LBC was using 8620 for their bolts. I suspect that's what happened here.

Given the quality of the parts and Mark's excellent reputation (and the sister rifle he built in 5.56 NATO runs like a sewing machine and shoots ragged 100 yd holes with Lapua factory 69 grain Scenars), I am inclined to suspect the LBC metallurgy (and the known weakness of the Grendel bolt design).

That said, I will ask Mark about receiver squaring and the barrel extension.

[bwaites]

I don't think this is accurate.

Not long ago there was a thread here where a guy was having similar problems with an LBC bolt. I want to say he tried 2 more with the same sheered lug results. I believe he recently posted that he got an AA hard use bolt and the weapon is operating fine suppressed.

It was hypothesized in that thread that LBC was using 8620 for their bolts. I suspect that's what happened here.

I guess I missed that thread. I would be surprised that LBC was using 8620. I guess i shouldn't be, nothing surprises me much anymore!

[Nukes]

I guess I missed that thread. I would be surprised that LBC was using 8620. I guess i shouldn't be, nothing surprises me much anymore!

And I was soooo happy to be up and running so soon after the first bolt sheared—4 days including the day it sheared.

[LRRPF52]

8620 steel heat-treated outside the margins of error will produce very weak bolts, even in 5.56 NATO, and there have been some cases of 5.56 bolts breaking early, but it isn't that often.

I know the AA bolt I have has been trucking along like a champ since 2009 now, and I haven't been exactly nice to it since all my shooting is either pressure ladders, or warmer loads mass-produced with the 123gr A-MAX, with Hornady 123gr A-MAX boxed ammo matching what I load in terms of volume. I'm not the kind of guy that just shoots a box of 20 and heads home either, and I'm one of the few that has done hose-session testing with mine to determine muzzle climb with higher load weight loads with the 100gr NBT:

[video]http://youtu.be/qApXp7sH9QQ[/video]

[cory]

I guess I missed that thread. I would be surprised that LBC was using 8620. I guess i shouldn't be, nothing surprises me much anymore!

I want to say it was dammitman who I'm talking about, but I may be wrong.

[Nukes]

8620 steel heat-treated outside the margins of error will produce very weak bolts, even in 5.56 NATO, and there have been some cases of 5.56 bolts breaking early, but it isn't that often.

I know the AA bolt I have has been trucking along like a champ since 2009 now, and I haven't been exactly nice to it since all my shooting is either pressure ladders, or warmer loads mass-produced with the 123gr A-MAX, with Hornady 123gr A-MAX boxed ammo matching what I load in terms of volume. I'm not the kind of guy that just shoots a box of 20 and heads home either, and I'm one of the few that has done hose-session testing with mine to determine muzzle climb with higher load weight loads with the 100gr NBT:

[video]http://youtu.be/qApXp7sH9QQ[/video]

Until the shortages I was of a similar style, but no longer and not again until I see pallets and ammo forts everywhere. Only when the Krieger barrel starts to open up will I flip the selector to "pew, pew, pew."

[ATTACH=CONFIG]4679[/ATTACH]

[Drifter]

Didn't realize that Mark at SAC built your upper. Forgive me for questioning the build. Mark knows his stuff.

Mark chambered a Krieger barrel in 264 LBC for me a few years ago. The bolt broke. He told me to check with LBC on a replacement, as that was where the original came from.

According to this link, LBC's 223 BCGs are 8620:

http://www.brownells.com/rifle-parts/bol...R%20CUSTOM

[bigbear_98]

I guess I missed that thread. I would be surprised that LBC was using 8620. I guess i shouldn't be, nothing surprises me much anymore!

Here is the thread http://www.65grendel.com/forum/showthrea...bolt-break

I broke an LBC after 45 suppressed factory hornady rounds. When I called them they told me it was my fault for running a suppressor. I did a ton of research and came up with softer or inferior heat treating but because I couldn't say "Jo blow at xyz firearms" told me so I was dismissed. I have 342 suppressed on the new maxim bolt.

[bigbear_98]

Didn't realize that Mark at SAC built your upper. Forgive me for questioning the build. Mark knows his stuff.

Mark chambered a Krieger barrel in 264 LBC for me a few years ago. The bolt broke. He told me to check with LBC on a replacement, as that was where the original came from.

According to this link, LBC's 223 BCGs are 8620:

http://www.brownells.com/rifle-parts/bol...R%20CUSTOM

Huh. Info from xyz....

[cst]

all these negatives about bolts and barrels are making it real hard for a newbie like me to not cancel my order and get out of the grendel....

[bwaites]

all these negatives about bolts and barrels are making it real hard for a newbie like me to not cancel my order and get out of the grendel....

Bolts break in 5.56, 6.8, 300 BLK, etc. Its a moving, reciprocating part, thus subject to wear and tear. Nukes issues are a bit unique, and either there is a manufacturing issue with the bolts, or there is an alignment issue with the bolt/barrel extension.

AR's are not bolt guns, bolts are a consumable regardless of caliber. If you stick to known safe loads, bolts last a long time, as LRRPF52 points out.

[bigbear_98]

all these negatives about bolts and barrels are making it real hard for a newbie like me to not cancel my order and get out of the grendel....

I was on the verge of doing the same when lbc told me no suppressors. I had bought a krieger barrel and couldn't get a good bolt...? I posted here and talked to a lot of good knowledgable people around here and was talked off the ledge. I sent my second and third lbc bolt back and bought a maxim. I have learned the cartridge is a neat round. I have hit 12" steel all the way to 1175 with ease, golf balls at 500, clay pigeons at 750. All with similar recoil to my SBR 556. I am extremely pleased.

[cst]

can someone explain to me...when a bolt is sent to say lilja for it to be chambered off of...say a typeII bolt from LBC or AA etc...what if that bolt breaks...you can simply just buy another brand typeII, drop it in, and wont loose any accuracy?
In other words..then whats the point in sending in a bolt to have it made to chamber that? As long as you have a consistent typeII or I bolt to the chamber you should be able to interchange bolt brands ... correct? and not loose accuracy..? Liljas site says that they dont guarantee if another bolt is used with their barrel since its headspaced with a maxim...