So I want to thread my Sako 75 finnlight in 300 win mag. Obviously, I don't need a can on a mountain rifle but since it holds 3/4 MOA, I figured a can might make it even better when I was shooting long distance off a ridge against elk in meadows or clear cuts. Yes I know it's not what the rifle was intended to be used originally for, but I ain't humping my sendero with a nightforce scope up these hills either. I suspect the change in point of impact should not be too extreme with the 7.62 omega hanging off the end of a 24 & 3/8 fluted barrel.

It would appear that 5/8 x 24 (.625), nor 1/2 x 28 threads are not good options as the barrel is a 0.63 diameter contour at the muzzle.

I assume 5/8 thread won't leave enough thread in the first case to grip nor leave enough shoulder to index off of.

1/2 thread wont leave enough barrel meat around the bore (.5 - .308 = 0.192) as most suppressor makers recommend at least .200 of remaining meat - especially on magnums from what I gather.

Now 9/16 (.5625) gives at least a 0.0625 shoulder, especially as the barrel shortens toward the chamber. Also leaves about 0.2545 (+) of remaining meat outside the bore.

My thought is to do 9/16 LH thread pitch and put an 7.62 ASR flash hider on there (which they indeed make), which would serve as a quick detach for my SilencerCo Omega can. Then I can easily attach the can and the can shoulders and indexes off the ASR mount. Not looking to put the muzzle brake as the blast would be obnoxious without the can.

I assume that the .0625 shoulder allows enough meat for the ASR flash hider to hook up firmly or does it (tge ASR FH) even need a shoulder like you would with a can??? This would seem to be a better option than trying to do a direct thread on this barrel contour.

Thoughts? Appreciate your input.

I thread 30cal sporter barrels 9/16x24 threads usually. unless its smaller than .600 ill go 1/2x24. I haven't had any problems with the ones ive threaded.

Here is what SilencerCo said (cobbled together over a few emails) regarding using a device to attach my Omega can on my .63 diameter barrel:

We would recommend the 9/16x24 thread pitch. However, we would recommend going with the RH thread and using the muzzle brake. All of our tests have shown that the muzzle brake has better accuracy than the flash hider. If you are worried about the side concussion then you can use the ASR Blast shield to direct the blast forward. The 9/16x24 will give you enough shoulder for proper shouldering of a flash hider or muzzle brake.

Yes, 9/16"-24 is the standard thread for a 30 cal barrel of that size.

Choosing an oddball LH thread would be a lot like peeing on your own foot though. Stick with the standard RH threads.

I need an ASR mount of some kind to screw into the omega can. For some odd reason, the silencerCo OEM ASR flashhider comes in a 9/16 left hand thread, while the ASR muzzle brake comes in a right hand thread.

My intent was to get the FH verses the brake, b/c I'm not going to have the can on while sitting in a tree stand or while moving.

I still wonder why they found that the brake would give better accuracy when attached to the can, verses a flash hider or direct thread.

That is weird. Are you certain the flash hider isn't offered in both LH and RH threads? It would make more sense if the LH thread version was made specifically for some European rifle. 9/16"-24 LH threads are definitely not any sort of standard in the US, and you'd have a lot of trouble finding other muzzle devices to fit that later down the road.

That's what their site says. Now it could just be a typo on their part.

From SilencerCo:

The 9/16x24 LH Flash hider is for FALs and indexes on the muzzle of the barrel instead of the shoulder of the barrel.

The 9/16x24 RH muzzle brake is for standard barrels.

The reason we have the two different thread muzzle devices is to avoid any mixups.

That makes more sense, the LH threads are just for the FAL.

Still seems weird that they don't have a flash hider option for RH threads; lots of people don't like brakes on their rifles.

As a side note - IF you're going to use a muzzle device like that FAL flash hider that indexes on the muzzle, then you could stick with a 5/8"-24 thread on that .630" barrel.

The larger thread is a little better; keeping more of the original steel around the muzzle is a good thing. You may or may not see a difference in accuracy, but it won't make it worse.

A buddy who owns an ammunition manufacturing company and use to be a Gov't hunter told me that he has had an accuracy improvement when installing cans 100% of the time. Must be something to it. Certainly will change point of aim but gives better accuracy too.