338 barrel chop for TBAC ultra

[Kspence49]

A while back (obviously) I picked up a 338 ultra from TBAC. I asked the rifle builder of my 338 lapua what threads they used and they told me they should be 5/8x24. It made sense to me at the time so I didn’t bother checking (that’s obvi on me). Well, my can got approved and it turns out it is not 5/8x24, but rather 9/16x32, which is a size TBAC doesn’t support. I asked if they could make me a custom muzzle device and they said they wouldn’t, but they would cut and rethread my barrel. I’m not 100% happy with the solution as the barrel is fluted and I think it’ll look weird being shorter, but it seems that it is what it is at this point if I want to use my new can. It’s my primary hunting rifle and I’m planning on running the suppressor, so my question is if you were gonna have to cut the barrel any way would you take some length off? It’s currently 26” and I was considering going to 20 or 22. I’ve heard that people typically lose about 150fps dropping down to 20, but can’t find a ton of data on it. Or would it be better to keep the 6”? Is it that big of a maneuverability advantage? I’ve only ever hunted with longer barrels up to this point.

 

[Supersubes]

Are you sure its 9/16x32? How much length do you have between the end of the flutes and the shoulder of the muzzle thread?

Only you can decide if you’d like it shorter. You’ll lose 30 fps per inch.

 

[Kspence49]

Positive it’s 32tpi. Probably an inch between the end of the flutes and the muzzle

I understand the velocity loss, was hoping to get some feedback on if 6” of barrel is noticeable for maneuverability or if it’s negligible and people would rather have the velocity

 

[Supersubes]

Positive it’s 32tpi. Probably an inch between the end of the flutes and the muzzle

I understand the velocity loss, was hoping to get some feedback on if 6” of barrel is noticeable for maneuverability or if it’s negligible and people would rather have the velocity

You only need .6” for the new thread, so just have it re-threaded, and the flutes will be untouched.

What's the muzzle diameter at the current thread shoulder?

 

[Kspence49]

You only need .6” for the new thread, so just have it re-threaded, and the flutes will be untouched.

What's the muzzle diameter at the current thread shoulder?

Muzzle diameter at thread shoulder is 0.830”

 

[vh20]

I assume the builder would rethread at no charge since they told you it would be 5/8-24?
Another option would be 9/16-32 x 5/8-24 adapter into a 5/8-24 338BA TBAC brake into your 338 Ultra. I haven’t personally tried this but they are available. You’d want to check concentricity carefully.

 

[JBoomhauer]

Chop it. 9/16-32 class 3 is a .519 min minor diameter. With a .338 groove diameter, you have .090 wall thickness. Less if there is a relief groove.

 

[godofthunder]

If I'm reading thread specs correct, you could have a 1/2-28 mount bored out for .338 and have the threads recut to 9/16-32. I might even have a bare 17-4 mount around that would work well for it.

 

[jetmd]

Do you have other rifles you plan to use this can on?

I run my 338 Ultra across several.

If you do it ‘may’ be possible for ECCO Machine in CO convert your can to HUB mount and you would be set to run TBAC CB, HUB to 5/8 etc.

Personally I would just rethread removing just enough material to accommodate this.

I have used ECCO in the past with 100% satisfaction.

Just wanted to provide choices.