BLR w/Muzzle Brake Wall Thickness

M

mhotz

Inactive
Hello

I have a question about the minimum safe wall thickness for a Browning BLR with a muizzle brake installed.

I purchased a used Browning BLR in 300 WSM.The rifle has a pencil barrel (OD approx = .6" at muzzle). It came with a KDF muzzle brake (.6" OD, 1/2-28 Threads) already attached.

My undedrstanding is that a common rule-of-thumb states that to be safe a barrel should have a minimum of .140" wall thickness remaining after threading the barrel for the brake.

Therefore, this rifle's .05" wall thickness [ (.6 - .5)/2 = .05 ] after threading for the KDF is 64% less then the rule-of-thumb of .140".

What are your thoughts? Is the rule-of-thumb bogus? Has anyone seen first hard or heard about a BLR in .308 caliber with a muzzle brake having a problem because of wall thickness?

Thanks

(This question also posted on CalGUNS forum)
 
1/2" is the major diameter. The minor diameter, according to a chart I found online, is something like .456. I'm not sure if that makes it safe or not, just thought that information might be helpful to you.
 
Many brakes come with instructions stating a minimum wall thickness of .125". I would have a few questions about the brake installation other than the thread shank thickness, such as what caliber is the rifle (if it is a 308, your barrel wall thickness is already very thin in the threaded area: .308" + .030" bullet clearance = .338", .458"-.338"= .120"/2= .060 barrel wall thickness in the threaded area) The wall thickness is critical in the brake area itself, so check if the brake has an expansion chamber and determine the wall thickness in that area. If you have questions about the safety and integrity of your brake, have it removed, remove the threaded area, rethread to 9/16-24, and get a new brake installed.
 
If it's factory threaded, it would be interesting to call Browning and discuss this with tech support. Safe to say, their engineers have done their research, and I'm confident that an injured shooter owning part of Browning is a real consideration for them.

I recently posted on another forum about this very issue, specifically about whether it's "safe" to go to even 9/16" with .30 cal. Industry standard seems to be 5/8".

I noted the ubiquitous AK is threaded 14mm, which translates to a wall thickness of about .093. The FAL is threaded 9/16".

.457 minor less the .308 groove diameter of your barrel leaves .149/2 or about .0745. Less than I'm comfortable with, anyway.

Point is, there does not seem to be a standard. I have seen CIP specs for wall thicknesses at various distances from the chamber, but they're metric and confusing.

It's important to realize that the accuracy of the thread depth is also critical if "cutting it close". I've begun to use 9/16" where I need the extra meat for the shoulder on the thin Mosin-Nagant barrels I work on.

Should you discuss this with Browning, please post back and let us know what they have to say.
 
Last edited:
g.willikers,

Yes, all of them have done pressure studies on their barrels. They manufacture a new barrel design, and practically drill it full of holes, tap them, add fittings and tubing, and connect those to pressure recording graphs for each inch of the barrel, from the start of the rifling, to the end. The chamber area is checked with strain gauges. Winchester and Remington used to have a picture of an engineer checking them. I think it is on that Remington tour video on YouTube, too.

Browning's design philosophy used to be, design it until it is strong enough, then double it.
 
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