Threading the muzzle on a 111 in 300 Win Mag?

[greatpennstater]

I'm looking into getting my Trophy 111 in 300 Win Mag (24 inch barrel) threaded to add a suppressor from Thunderbeast (The Ultra 7). My concern is this - I cannot do 5/8x24 for obvious reasons...the diameter at the muzzle is only .590. I called Thunderbeast directly, and they said they are able to do a 9/16x24 thread and add the muzzle break onto which the can would be mounted. They would use loctite so basically not removable, which I don't see as an issue. I thought, great! This is directly from the manufacturer, so it should be fine. I am only a few hours from Cheyenne, where they are located, and would drive it there and back.

However, after talking to another local gunsmith, who also sells the Thunderbeast, he would still NOT do the threading to those specs, and even said he wouldn't do it on his own rifle, due to the lack of barrel wall left.

My hesitation is this - is the amount of barrel wall left after the threading a safe amount? Has anyone done the threading on this thin of a barrel for a can? Any issues?

Last question - if not safe, what are my options for an aftermarket barrel that can be threaded, and can be added to my existing platform?

TIA!

[clm2112]

I'll offer a suggestion, but it will take a reasonably skilled machinist to accomplish (meaning it might be cheaper to start with a barrel with a thicker muzzle).

First, have the barrel muzzle turned down just enough to make it concentric to the bore and cylindrical for about a half inch. Then, using a chunk of scrap barrel of the same steel type, make an adapter sleeve that slides over the freshly machined muzzle. Braze that sleeve in place and thread it 5/8th-24. You end up with a dumb-bell contoured barrel that looks like what AAC sells for their lightweight suppressor barrels. This was the old way Cutts compensators were installed on barrels. And since it doesn't require reducing the muzzle diameter to a thread size, you don't have to worry about the wall thickness.

Here's what it would look like when done...

https://image.ibb.co/fC6Acb/300_AAC_Model_7_Muzzle.jpg

[clm2112]

One additional thought...

While the gunsmith you spoke to would not machine a 30 caliber barrel down to a 9/16th - 24tpi thread, I do know there are factory 30 caliber barrels with muzzles threaded that way. Browning uses 9/16th-24tpi threaded muzzles for the B.O.S.S. barrel tuning system. I doubt their barrel steel is somehow better than Savage's barrel steel, so the wall thickness that results must be sufficient.

Funny thing about this topic... while wall thickness is often discussed when dealing with shotgun barrels, and has pretty well established minimum wall thickness guidelines (done a lot of screw-in choke installations on fixed choke barrels), I've never read any such guidelines for high pressure rifle barrels.

[stomp442]

I have threaded numerous barrels 9/16-24 and haven't had a problem. They shot great before and after.

[greatpennstater]

Thanks for all of the info, great suggestions. I'm going to talk to another machinist, including Class 3 which I have heard does really great work, and will be sure to ask about the sleeve.

Thanks!

[tobnpr]

It's not an issue of barrel wall thickness, I've threaded dozens of .30 cal rifles in 9/16"..How many millions of AK's and FAL's are there with just that (convert the metric, about the same minor diameter).

Your estimated 15 thou shoulder isn't really enough for a brake, certainly not a can.

. Cans need a substantial shoulder in the neighborhood of 100 thou to ensure perfect concentricity.
Consider the length of some cans- and baffle clearances.

[Robinhood]

I am a class 3 machinist...I think. Who am I kidding. It is possible to thread your barrell to 9/16-24 and bottom on the face of the muzzle. It could even be cut for a counter bore in the muzzle break . You could do a clamp on too. A true machinist can do it all including making the brake, for a price.

[tobnpr]

I am a class 3 machinist...I think. Who am I kidding. It is possible to thread your barrell to 9/16-24 and bottom on the face of the muzzle. It could even be cut for a counter bore in the muzzle break . You could do a clamp on too. A true machinist can do it all including making the brake, for a price.

Perhaps he was referring to Class 3 threads, who knows...

What do you mean when you say "bottom on the face of the muzzle"??

[clm2112]

Perhaps he was referring to Class 3 threads, who knows...

What do you mean when you say "bottom on the face of the muzzle"??

Using the tip of the barrel as the flat surface the tighten against. Usually you want a shoulder cut into the exterior of the barrel to tighten against. But when the barrel diameter is just about the same diameter as the thread, there isn't enough material to make a shoulder on the barrel. So, the alternative is to pick another place to tighten against, like the muzzle. (The actual "shoulder" ends up being inside the suppressor instead of being on the outside of the barrel.)

I'm not sure if this approach would work for the OP... who wants to run a commercially made suppressor on the barrel. You are pretty much stuck with how the suppressor is threaded and how they expected it to tighten on the barrel.

Now, some suppressor makers use a proprietary thread to allow a quick connection of the suppressor to the barrel, then use an adapter that is supposed to be permanently installed on the barrel. In this style, you may be able to use no shoulder at all (brazing the adapter on or staking it with distorted threads to keep it on the barrel.)

Edit: I went and took a look at Thunderbeasts' web page for the Ultra 7 suppressor. They have what they call a "CB" mount, which is a custom muzzle brake that stays on the barrel when you remove the actual suppressor. So, you could have the barrel muzzle threaded 9/16th-24, install the CB mount/muzzle brake, and braze it in place to make it permanent. They are a little pricey, at $125 per mount, but compared to the price of the suppressor itself, it might be a good option. You could also add adapters to additional barrels and share the expensive can on multiple rifles.

To the OP: I should have read your post a little closer... you already know about the CB mount. That is really your best option, since the CB mount is the same thing as adding a sleeve to the barrel. The CB mount is the sleeve and it provides everything the suppressor needs to tighten onto the barrel. Considering the suppressor make is offering to thread & install the adapter for you, I'd take them up on the offer.

[greatpennstater]

Using the tip of the barrel as the flat surface the tighten against. Usually you want a shoulder cut into the exterior of the barrel to tighten against. But when the barrel diameter is just about the same diameter as the thread, there isn't enough material to make a shoulder on the barrel. So, the alternative is to pick another place to tighten against, like the muzzle. (The actual "shoulder" ends up being inside the suppressor instead of being on the outside of the barrel.)

I'm not sure if this approach would work for the OP... who wants to run a commercially made suppressor on the barrel. You are pretty much stuck with how the suppressor is threaded and how they expected it to tighten on the barrel.

Now, some suppressor makers use a proprietary thread to allow a quick connection of the suppressor to the barrel, then use an adapter that is supposed to be permanently installed on the barrel. In this style, you may be able to use no shoulder at all (brazing the adapter on or staking it with distorted threads to keep it on the barrel.)

Edit: I went and took a look at Thunderbeasts' web page for the Ultra 7 suppressor. They have what they call a "CB" mount, which is a custom muzzle brake that stays on the barrel when you remove the actual suppressor. So, you could have the barrel muzzle threaded 9/16th-24, install the CB mount/muzzle brake, and braze it in place to make it permanent. They are a little pricey, at $125 per mount, but compared to the price of the suppressor itself, it might be a good option. You could also add adapters to additional barrels and share the expensive can on multiple rifles.

To the OP: I should have read your post a little closer... you already know about the CB mount. That is really your best option, since the CB mount is the same thing as adding a sleeve to the barrel. The CB mount is the sleeve and it provides everything the suppressor needs to tighten onto the barrel. Considering the suppressor make is offering to thread & install the adapter for you, I'd take them up on the offer.

Thanks, I intend to do just that. I will be making the trip to Cheyenne and having TB do the work. It is only a little bit over an hour for me, and I'll have peace of mind. Thanks all!