Bolt Shear

**LukeMacGillie** · 08-12-06, 09:14

Ive been dealing with a whole bunch of M4's with sheared locking lugs on the bolt.

Every one of them the locking lug to the left of the extractor (looking at the bolt from the back side) sheared off. Round count was unknown, "Alot", "2 Ass loads" ect were the best guess. Most of the shooters had been visiting a guys range in TN, who likes TO TYPE IN ALL CAPS

My question is prompted since it was all the same lug that broke. Should I be worried that I have a batch of bad bolts?

the weapons in question are all M4A1's with stock FA BCG's without the Crane Extraction enhancement kit installed.

**Robb Jensen** · 08-12-06, 09:54

Originally Posted by LukeMacGillie

Ive been dealing with a whole bunch of M4's with sheared locking lugs on the bolt.

Every one of them the locking lug to the left of the extractor (looking at the bolt from the back side) sheared off. Round count was unknown, "Alot", "2 Ass loads" ect were the best guess. Most of the shooters had been visiting a guys range in TN, who likes TO TYPE IN ALL CAPS

My question is prompted since it was all the same lug that broke. Should I be worried that I have a batch of bad bolts?

the weapons in question are all M4A1's with stock FA BCG's without the Crane Extraction enhancement kit installed.

In my experience MP tested bolts seem to break the lugs, while non MP break usually in half at the cam pin hole. M4s and carbines in generally go through bolts much more often than full length (20") rifles. I've had some bolts last 3K rounds and some last nearly 20K rounds. I don't think you have a bad batch.

The Crane enhancement kits will help a little. The biggest things stressing the bolts are heat and pressure. Slowing down the cyclic rate (heavier buffer) will extend bolt life some.

**QuietShootr** · 08-12-06, 10:00

H3 or 9mm buffer, bro.

**LukeMacGillie** · 08-12-06, 10:10

Originally Posted by generic

H3 or 9mm buffer, bro.

Aint gonna happen. Its not Stock..........

**QuietShootr** · 08-12-06, 10:23

Oh. Well, shit the bed.

**Ned Christiansen** · 08-12-06, 10:30

I think bolts are only rated for 1.5 assloads. That's the problem!

**Robb Jensen** · 08-12-06, 10:39

Originally Posted by Ned Christiansen

I think bolts are only rated for 1.5 assloads. That's the problem!

So that means your working on making a new bolt rated for 1.5+, 1.5+P and 1.5+P+ assloads right Ned?

**Submariner** · 08-12-06, 10:42

Originally Posted by LukeMacGillie

Ive been dealing with a whole bunch of M4's with sheared locking lugs on the bolt.

Every one of them the locking lug to the left of the extractor (looking at the bolt from the back side) sheared off. Round count was unknown, "Alot", "2 Ass loads" ect were the best guess. Most of the shooters had been visiting a guys range in TN, who likes TO TYPE IN ALL CAPS

Did the bolts come from the gentleman who "likes TO TYPE IN ALL CAPS"?

Is he welcome to post here?

**M4arc** · 08-12-06, 11:10

Originally Posted by Submariner

Did the bolts come from the gentleman who "likes TO TYPE IN ALL CAPS"?

Is he welcome to post here?

I don't see why not.

No matter where the bolts came from they are a high wear items and they break. Replace them with Colt, LMT or CMT MP'd bolts and have plenty of spares on hand.