Surefire 3 prong muzzle device help

[Krp7894]

Hi all,
I was having a tough time timing the Surefire 3 prong muzzle device right on my 300 BLK LMT barrel. This will go with my socom 762 mini 2. Anyways, I took it to my local shop and the gunsmith did it for me in about 15 minutes and gave it back free of charge. Timed perfectly however I noticed he didn’t use the supplied chamfered spacer. Is it necessary? I put the suppressor on and put a rod down the bore and it is dead center. I don’t want to shoot this in a few days and have some big issues. Does the spacer matter ?

[hi-wayman]

The chamfered spacer, also called a crush washer, shouldn't be used on a suppressed gun.
Is your gunsmith reputable and knowledgeable about suppressors? Do you trust him?

I use a single shim of the appropriate thickness to where the device is timed at the proper torque.
https://precisionarmament.com/accu-w...gnment-system/

He may also have just torqued it until it was timed with no shim. Only ok if he got lucky and didn't over-torque it distorting the barrel.

Either way, he should have cleaned the threads and applied Rockset. It expands with heat. Regular automotive thread locker (red, blue, etc.) breaks down with heat and is how it is removed. And suppressors get HOT.

If you can see a shim between the barrel and MD, you're probably ok. Just check the clocking of the device when you shoot it and check often. If it starts moving, stop and have it remounted.

The rod check should be done with the suppressor mounted.

[Krp7894]

Yes these guys build their own rifles in house. And he used shims just not the chamfered spacer. Here’s a pic. It’s lined up perfectly and i did put the rod down the bore with the suppressor. It looks perfect.

https://ibb.co/ZTGpDGr

This second pic shows the alignment rod
https://ibb.co/FKVqHLc

[hi-wayman]

You should be good! Just verify it doesn't loosen when you shoot it, just because things happen.

[Krp7894]

Ok perfect thank you! I’m trying to get out and shoot this week, I’ll probably shoot first unsuppressed and then suppressed. I’ve had baffle strikes before and it’s not fun.

[Wake27]

You’re talking about the chamfered shim that comes with the shim kit from SF right?


Sent from my iPhone using Tapatalk Pro

[Krp7894]

You’re talking about the chamfered shim that comes with the shim kit from SF right?


Sent from my iPhone using Tapatalk Pro

Yes, I believe they refer to it as a chamfered spacer if I’m not mistaken.

[IZinterrogator]

The manual says the spacer should be used on a barrel with a shoulder, but not on a barrel without. That seems backward to me, because the chamfer towards the chamber on an shoulder-less barrel should create a flat surface for the shims to time against, while the shoulder should be sufficient as a load bearing surface for the shims to time against without the spacer.

[LoboTBL]

Someone correct me if I happen to be wrong but... the guidance regarding using the shim on a barrel with a shoulder vs one without should be adhered to. Probably because the shoulder will support the shim simply for the purpose of timing of the MD. The shim alone probably isn't really strong enough to act as a bearing surface for the MD and could deform.

[gaijin]

I’ve rarely seen an AR Barrel without a shoulder for muzzle device.
Think I’d seen Clinton Ban era guns sans shoulder.

But yes, you need a barrel with shoulder to use shim.