Hello Everyone,
I obtained a Precision Armament M4-72 muzzle break for my birthday back in May. I currently have the firearm out being threaded and when it comes back I plan to have a gunsmith attach the break for NJ compliance. I am currently running into an issues where the maker of the break says not to install the device using crush washers. However, my gunsmith feels that it would be fine to use crush washers and that the company is trying to sell me their washer kits. This is the first time having the gun threaded so I want it to be installed correctly. I trust my smith since he is very experienced with installs but I am concerned about using crush washers since they say not to use them to install their breaks. I could use spacers to install the break instead but my smith said he gets best results with crush washers. I really need feedback on now to proceed. Any advice would be greatly appreciated!
 
Here is what the manufacture claims
"Crush washers are perfectly acceptable to use on any open aperture muzzle device, such as the standard A2 birdcage flash hider. However, our opinion is they should never be used on any baffle style muzzle device where the clearance hole is only slightly larger than the bullet. Firstly, crush washers come to a knife edge on both mating surfaces - it is likely for this reason that a muzzle device is already misaligned just sitting on the crush washer before it is even torqued down. More importantly, it relies on the principle that the washer will deform uniformly while it is being crushed. This requires that the material is uniform and that you apply a perfectly pure torque load normal to the bore. This is very unlikely (for anyone who has installed one) when you're putting all your might into the 30-60 ft-lbs of torque they often require. The consequence of this misalignment is a baffle strike at worse and impaired accuracy at best.

We recommend our Accu-Washer Shim System for installation as they alleviate both of these issues providing the highest safety and performance from your device. Also, a peel washer or any precision multi-shim system are also perfectly acceptable methods for aligning your muzzle device.

Also consider that crush washers have the capacity to deform further beyond your install. So, if you happen to hit the muzzle on something with enough force you may permanently angle your device to the side killing your accuracy or worse: rendering the rifle useless."

I would agree with the manufacturer. AAC suppressor mounts expressly forbid the use of crush washers because the washer doesn't deform uniformly and can cause baffle strikes when used with a suppressor. If the bore in the brake you purchased is relatively tight compared to the bullet diameter, it's possible that you could run into the same issue. Shims and peel washers would be a much better solution.

MidwestPX covered it.

 

If you end up using a crush washer don't be surprised if you get the equivalent of a baffle strike on the muzzle device.

Shims and peel washers are also a LOT easier to use to get an offset index if you prefer your comp angle customized for your taste.

I would agree with the manufacturer. AAC suppressor mounts expressly forbid the use of crush washers because the washer doesn't deform uniformly and can cause baffle strikes when used with a suppressor. If the bore in the brake you purchased is relatively tight compared to the bullet diameter, it's possible that you could run into the same issue. Shims and peel washers would be a much better solution.

So does Gemtech. I think they all do.

Why use a washer/shim if you are pinning/welding it on? In most cases, alignment can be achieved by taking material off the back end of the muzzle device.

Why use a washer/shim if you are pinning/welding it on? In most cases, alignment can be achieved by taking material off the back end of the muzzle device.

That's what you did with the two FSC556 brakes you pinned for me - and it worked well.

 

I just don't think I would trust myself, or someone that doesn't do that regularly, to get it done correctly.

I opened up the brake on an FSC556 anyway. I just burned it right out with FA from an 11.5" over about a couple thousand rounds. I mounted it with washers because I used it with a HALO and there were never any strikes. Just eroded.

Thank you everyone for the advice! I asked my gunsmith to use shims. Thank you everyone for the help!