Trying to thread a .270 Winchester but only have .683"

[stre-tch]

Going to probably pick up a new .270 Winchester so I can hunt suppressed this year for big game


Problem is where I want to thread it the barrel is .683" in OD so the question is what can I do.


I will be installing a YHM QD mount for a YHM SS Phantom but I don't know if I have enough meat because 5/8x24 is .625" x 24.

AAC publishes a thred guide calls for .675 minimum on 5/8-24 muzzle devices but is this really enough for a 30oz can to hang off the end of a barrel as well as make it concentric with the bore?


Could I get it cut to 1/2x28 and bore out my 556 QD mount (1/2x28 thread pitch) to .308?


Would a 1/2x28 thread adapter to 5/8 x 24 lend itself to enough strength?


Thanks

[Trevor2011]

I would call the manufacturer and pose the questions to them.

[mbogo]

Are you aware that the .270 Win. has a very loud report?

mbogo

[ATCDoktor]

I have had 223's and 204 Rugers with .550 muzzle diameters threaded 1/2X28.

My barrel guy's have stated that .550 was plenty to give them the "major" diameter needed to perform the job.

That said, what was more of a concern to them reference threading muzzles this small was whether or not there was enough "shoulder" left after threading to support properly indexing the Mount/Can.

I would imagine that there are as many cans fucked up by having barrel shoulders that are not square/sufficient as there are with non concentric threads.

If the AAC specs call for a min of .675 for use with their cans and mounts then your probably good with YHM's as well (but you need to talk to YHM and your barrel threader about what their mins are prior to having any work done).

[Walker Precision]

Index the mount on the muzzle rather than the shoulder. YHM's thread specifications detail how to thread the barrel for muzzle indexing.

http://yhm.net/pdf/762_PHANTOM_625-24.pdf

[stre-tch]

Walker -

Thanks for the PDF -

How does indexing the mount on the muzzle rather than the shoulder differ?


I figure I better understand it so I can ask the gun smith if he understands it.


Thanks

[ATCDoktor]

How does indexing the mount on the muzzle rather than the shoulder differ?

The inside face of the mount will "butt" up against the muzzle face.

Essentially you tighten your mount to the muzzle of the rifle as opposed to a shoulder on the barrel so the muzzle face (Crown) would have to be machined flat (square) so as t0 support proper alignment.

I have had it done on a Remington Model 7 who's muzzle diameter was too small to support sufficient shoulder.

Tornado Tech did the work but threaded the barrel about 1/8" too long but it worked alright.

The only thing that "long threading" the barrel did was leave the last 1/8" of threads exposed behind the mount.

There is a pic here in this thread if you scroll down to my post:

viewtopic.php?f=86&t=69642&p=668484#p668484

[stre-tch]

ahhh thanks!

I will have to look at inside of my 556 qd mount ( I am assuming the 308 qd mount is the same) to see if I can index it on the muzzle. I thought it was tapered inside of the mount after the threads end

[ATCDoktor]

I will share that my experience with this type mounting (indexing on the muzzle) did have an issue.

That issue being, for what ever reason, the POI shift from unsuppressed to suppressed was not repeatable on this specific rifle set up this way (AAC M42K with Blackout flash hider indexing on the muzzle).

I had to re sight in the rifle everytime I removed and replaced the can.

None of my other rifles demonstrated this problem so I attributed it to how the mount was indexing on the barrel.

It was for this reason I didn't speak to indexing on the muzle in my first post as I no longer use it based on my experience on this rifle.

I have since transitioned to a thread on suppressor (GEMTECH Ti TREK) and have no problems with repect to repeatbility of POI shift when removing and replacing the suppressor.

I'm not saying your rifle will demonstrate this same issue, I'm just sharing that mine did.

[Bird]

Had the same issue with my son's 7mm-08. The machinist, who also happens to be a 07/02SOT, suggested to have the barrel threaded to 1/2x28 to provide plenty of shoulder and then get a threaded adapter to 5/8x24. Cheap and easy fix that works great.

[stre-tch]

Bird -


Good to know. Do you worry about the 1/2x28 not being strong enough ( isn't this the reason why 308 suppressors have 5/8 x 24?)?


If I could get it cut to 1/2x28 then get an adapter to 5/8 x 24, I would be set

[jjmoberg]

Same issue for me on a Savage 111 .270. I think my barrel was only .580. A DBMG adapter works great for me. I shot my TBAC 30P-1 for the first time this past weekend. It was incredible how much better the shooting experience is with the can on. For reference, Thunder Beast recommends a minimum of .040 shoulder for proper alignment of their cans.

Jeremy

[Bird]

Bird -


Good to know. Do you worry about the 1/2x28 not being strong enough ( isn't this the reason why 308 suppressors have 5/8 x 24?)?


If I could get it cut to 1/2x28 then get an adapter to 5/8 x 24, I would be set

There's more than enough 'meat' on the barrel to support my AAC Cyclone (which is a pretty heavy can). The weight of the can is really supported by the mating face of the thread adapter to the can, while the threads, simply hold it in place. Regarding heating, its a hunting rifle so we're not doing mag dumps, 3 shots a minute would be a lot at the range. 1 shot in the field at a deer or a pig. On a tactical rifle, that might get real hot, from multiple rapid fire sequences I might be concerned about the heat on the turned down barrel threads. Get in touch with Mark McWillis at TROS USA for a thread adapter.