Skip The Suppressor and Break

Thought this may save someone a headache and some money.

I acquired a custom pre 64 Model 70 in 7mm Weatherby. I was drawn to the gun because it had a McWoody McMillan stock and 7mm Wby is literally my favorite caliber. Gun has a thin contour fluted barrel. All of my pre 64s wear wood stocks, so a faux wood grain McMillan seemed like a great idea for hunting.

I had very recently acquired my first 2 supressors, so I figured might as well get the barrel threaded too. Had to get a little creative given the contour. Not a lot of meat at the end, so went with a 9/16"x24 threading.

So took gun out to range today. By the time I was dialed in, shooting 1/2" groups at 100 yds with my Thunderbeast suppressor, shooting 150 gr ttsx bt.

Go out 200 yds and things got weird. Literally spraying every direction. 5 inches high, then 4 inches low and right. Couldn't do the same thing twice.

First thought was that I measured twist wrong and it was slower than the 1:10 I thought I was working with. So I was thinking maybe my 150 gr copper bullet was tumbling at 200 yds, but not noticeable at 100 yds. So I tried 140 gr ttsx, and the problem maybe improved slightly but still very inconsistent.

So then I took off suppressor and it all of a sudden became a laser at 200 yds. 1/4" group. I tried a muzzle brake for a test, but that too led to very inconsistent groupings.

Ditched the brake and bumped out to 300 yds. 1" grouping at 300 yds consistently when I took off brake and suppressor.

I'm new to suppressors so maybe this is not surprising to anyone, but after some reading I learned that thin barrels can be very sensitive to the extra weight, and the harmonics were getting thrown off with the suppressor and brake put on.

Just thought I'd share in case it helps anyone. I have a lot of thin barrels in the safe and won't be threading anymore of them. Ill save the the threading for the bull barrels.

I purchased a suppressor for my "heavier recoiling" rifles. Before it arrived, I found that my heavier weight rifles really didn't kick anywhere as hard as I'd thought. As I haven't shot my Dead Air Primal yet, I will reserve judgement and report back from the range. Good post!

If you have a super thin barrel supressors can make things wierd. We had some for a weatherby vanguard 300wm on a pencil barrel was functionally useless at 400m due to POI shift. But generslly on a med profile barrel should not be much of an issue with a quality supressor

bobdahunter84 said:

Thought this may save someone a headache and some money.

I acquired a custom pre 64 Model 70 in 7mm Weatherby. I was drawn to the gun because it had a McWoody McMillan stock and 7mm Wby is literally my favorite caliber. Gun has a thin contour fluted barrel. All of my pre 64s wear wood stocks, so a faux wood grain McMillan seemed like a great idea for hunting.

I had very recently acquired my first 2 supressors, so I figured might as well get the barrel threaded too. Had to get a little creative given the contour. Not a lot of meat at the end, so went with a 9/16"x24 threading.

So took gun out to range today. By the time I was dialed in, shooting 1/2" groups at 100 yds with my Thunderbeast suppressor, shooting 150 gr ttsx bt.

Go out 200 yds and things got weird. Literally spraying every direction. 5 inches high, then 4 inches low and right. Couldn't do the same thing twice.

First thought was that I measured twist wrong and it was slower than the 1:10 I thought I was working with. So I was thinking maybe my 150 gr copper bullet was tumbling at 200 yds, but not noticeable at 100 yds. So I tried 140 gr ttsx, and the problem maybe improved slightly but still very inconsistent.

So then I took off suppressor and it all of a sudden became a laser at 200 yds. 1/4" group. I tried a muzzle brake for a test, but that too led to very inconsistent groupings.

Ditched the brake and bumped out to 300 yds. 1" grouping at 300 yds consistently when I took off brake and suppressor.

I'm new to suppressors so maybe this is not surprising to anyone, but after some reading I learned that thin barrels can be very sensitive to the extra weight, and the harmonics were getting thrown off with the suppressor and brake put on.

Just thought I'd share in case it helps anyone. I have a lot of thin barrels in the safe and won't be threading anymore of them. Ill save the the threading for the bull barrels.

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Fascinating timing! I am considering a Thunderbeast Magnus for my .300 Wby and .257 Wby Blaser R8 barrels and have been in full search mode for the last few days for feedback.

The R8 standard barrels (17mm) too are considered too thin for the classic 5/8-24 thread and would require the same 9/16-24 thread you used...

Two questions: what Thunderbeast can do you use? and who cut the thread on your barrel?

And, if OK with you, I would like to use your post to create a new thread asking for folks' experience with silencers on R8 barrels

The one I was using yesterday was the Ultra 7 for a 30 caliber. I also have the Magnus with the built-in break but that one is for a 375.

To be clear, I bought those supressors for 3 guns I'm building. Those are going to have Proof carbon fiber barrels with sendaro contours. I just figured, why not thread the 7mm Wby and use the new toys together?

The gunsmith I used was Brett Buisse (Southeastern Wisconsin). He did a great job as he always does. He threaded 2 others for me at the same time that shoot great with the Ultra 7.

One was a Model 70 223 Winchester with a bull barrel. The second was a Weatherby Mark V In 223 Win. That gun also has a thin barrel, but I'm assuming it's the harmonics of the bigger 7mm Wby that causes the issue opposed to the little pea shooter 223.

I'm assuming you let the barrel cool down before shooting at distance? Thin barrels with overbore cartridges will start getting superhot after 3 shots and no longer hold any accuracy expectations.

Yeah that was definitely not the issue. I have a barrel fan for that reason. This was not a rapid fire situation. Like I said the issue was immediately resolved once the suppressor and brake were removed.

Thats wild, never experienced that with a suppressor. I dont have any on thin barrels though, almost all my suppressed rifles have Proof Carbons.

I have also seen problems with blowback in suppressors cause increased pressure in the chamber.


Definitely some nuances to work out with suppressors but over all when they work it is awesome. Especially for the young ones who still have good hearing! Goes a long way to protect that and also the less sound reduces flinching as well. The loud bang imo causes as much or more recoil flinching issues especially in younger and newer (non-hearing impaired old guys) shooters

Whenever I get erratic groups when shooting a direct thread can, it is loose. A loose can will cause all sorts of issues with accuracy. If it was fine at 100 yards, I suspect it should be fine at 200 yards.

Does not surprise me. Even letting my fingers touch the free floating barrel when shooting my old WWII Springfield on the bench will screw things up. And massively. "What the hell happened with that shot? Oh, right. Gripped the fore end wrong." As you can see it doesn't have a super thin profile barrel (but it is military).

Ontario Hunter said:

Does not surprise me. Even letting my fingers touch the free floating barrel when shooting my old WWII Springfield on the bench will screw things up. And massively. "What the hell happened with that shot? Oh, right. Gripped the fore end wrong." As you can see it doesn't have a super thin profile barrel (but it is military).
View attachment 795658

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That would be fine with a can

bobdahunter84 said:

The one I was using yesterday was the Ultra 7 for a 30 caliber. I also have the Magnus with the built-in break but that one is for a 375.

To be clear, I bought those supressors for 3 guns I'm building. Those are going to have Proof carbon fiber barrels with sendaro contours. I just figured, why not thread the 7mm Wby and use the new toys together?

The gunsmith I used was Brett Buisse (Southeastern Wisconsin). He did a great job as he always does. He threaded 2 others for me at the same time that shoot great with the Ultra 7.

One was a Model 70 223 Winchester with a bull barrel. The second was a Weatherby Mark V In 223 Win. That gun also has a thin barrel, but I'm assuming it's the harmonics of the bigger 7mm Wby that causes the issue opposed to the little pea shooter 223.

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That at least answers one of my concerns: the Ultra 7 is light: 8 oz. for the Gen 2 model and ~10 oz. for the Gen 1, so weight was not your issue.

I am wondering if a Magnus introduces a new variable with its ~18 oz...

One Day... said:

That at least answers one of my concerns: the Ultra 7 is light: 8 oz. for the Gen 2 model and ~10 oz. for the Gen 1, so weight should not be the issue. I am wondering is a Magnus introduces a new variable with its ~15 oz...

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If you're going to have it on a hunting rifle that you plan on carrying, you want the Ultra5 or 7 or even the Magnus S or K. The standard Magnus is super quiet but its the size of your forearm... it will change your rifles feel and balence where the others you'll hardly notice.

Wyfox said:

That's wild, never experienced that with a suppressor. I don't have any on thin barrels though, almost all my suppressed rifles have Proof Carbons.

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If bobdahunter84 could have his barrel threaded to 9/16-24, it is not an especially thin barrel.

The R8 'standard' barrel is 17 mm (0.67"). This is significantly thicker than my Win 70 barrel in .300 Wby (0.58") or even my Weatherby MkV in .340 Wby (0.60")...

Wyfox said:

If you're going to have it on a hunting rifle that you plan on carrying, you want the Ultra5 or 7 or even the Magnus S or K. The standard Magnus is super quiet but its the size of your forearm... it will change your rifles feel and balence where the others you'll hardly notice.

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Yep, this is my entire dilemma right now Magnus for maximum sound reduction or shorter Magnus or Ultra 9 for smaller footprint...

This is a well known issue with pencil barrels and the change gets far worse as they heat up. It has been a large factor in the carbon barrel craze. There is something to be said about the rigidity of a sendaro barrel with the sporter weight. I had a model 70 featherweight for a time and it was ridiculous how finicky that little barrel was! When it was allowed to cool between every shot it was by far the most accurate gun I've owned, shot more than twice and the 3rd was guaranteed to be off by 2" in a random direction with nothing on the barrel.

Continued from above reply. I took too long to edit...

Wyfox said:

If you're going to have it on a hunting rifle that you plan on carrying, you want the Ultra5 or 7 or even the Magnus S or K. The standard Magnus is super quiet but its the size of your forearm... it will change your rifles feel and balence where the others you'll hardly notice.

Click to expand...

Yep, this is my entire dilemma right now Magnus for maximum sound reduction or smaller footprint...
But the Ultra 9 for example is also 9" long and the Magnus is 1.8" in diameter instead of 1.5" for the Ultra 9, so the footprint difference is not really meaningful... Same for the OCL Hydrogen L (9.5" long, 1.6" diam.), the Banish 30 (8.5" long, 1.5" diam.) or the Dead Air Sandman (~7" long, 1.65" diam.).

I like the K or S concept, or Ultra 7 or 5, but they give up quite a bit in suppression from a 300 (Win) mag: 156 db. for the K, and 148 db. for the S (same as the Ultra 9), compared to 143 for the full size Magnus.

If you keep in mind the 3 db. rule (every 3 dB increase represents a doubling of sound), the S (or Ultra 9) is +5 db., or more than twice as loud as the full size, and the K (+13 db. over full size and +8 db. over S) is not even in the same league.

Since I virtually always shoot from the quad sticks, I do not think that the Magnus (18 oz.) additional 5 oz. over the 13 oz. of the S or additional 7 oz. over the 11 oz. of the K will matter all that much....

Wyit76 said:

This is a well known issue with pencil barrels and the change gets far worse as they heat up. It has been a large factor in the carbon barrel craze. There is something to be said about the rigidity of a sendaro barrel with the sporter weight. I had a model 70 featherweight for a time and it was ridiculous how finicky that little barrel was! When it was allowed to cool between every shot it was by far the most accurate gun I've owned, shot more than twice and the 3rd was guaranteed to be off by 2" in a random direction with nothing on the barrel.

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Agreed, but, again, a barrel that takes a 9/16-24 (0.5625") thread with a correct shoulder is NOT a pencil barrel...

My Win 70 in .300 Wby (barrel end 0.58") or my Weatherby Mk V in .340 Wby (barrel end 0.60"), both of them regular Win 70 and Mk V, have no issue printing tight 5 shot groups at about 1 shot per minute I would guess, and my numerous R8 barrels (0.67") all print 5 shot groups under 1 MOA...

Which makes bobdahunter84 experience even more puzzling for me.............................

@One Day... I'd have to go remeasure, but I believe to have an adequate shoulder I had to cut an inch off, to get to about 0.66 inches on the diameter and thread it. I believe it was a 26" barrel to begin with, so taking an inch off was actually not a bad thing in my opinion. I suppose "thin" is a bit subjective, but I think relative to the more modern trends for barrels that are threaded, mine was thin.

I don't claim to be an expert but I do believe that the caliber matters as well. As I mentioned previously, I have a thinner contoured Mark V chambered in 223 Winchester, that I had threaded to 1/2"x28, with an adapter to shoot the same Ultra 7, and had zero issue with the suppressor/accuracy. But the pressure is very different on a 223 Win than a 7mm Wby. I believe a 7MM Wby probably has about 70% more muzzle pressure than a 223 Win (I'd guesstimate 7,000 PSI to 12,000 PSI).

Again, my 7MM Wby is fluted too. I'm no engineer, but I'd assume removing that material from the barrel impacts its rigidity and thus the harmonics as well when adding a suppressor.

Certainly not saying my experience will be indicative of anyone else's. I realize there are a lot of variables that impact things. I just wanted to share mine in case anyone was on the fence to thread an existing gun and had similar rifle attributes.

Regarding the Magnus, I bought the Magnus-S RR. The RR version is just a brake that's added to the can, which obviously reduces the noise suppression. My research indicated that the K in RR is kind of a waste of money, too short with the brake to really make a meaningful noise difference. I read that you should technically still be wearing hearing protection if shooting the K-RR, which seemed to defeat the purpose!

So the S was kind of a sweet-spot from my research. You get the recoil reduction and noise suppression you're looking for without carrying the equivalent of a small infant on the end of your rifle in the "standard" version.

My personal recommendation is GO BIGGER on the the caliber choice when buying a can. Using my 375 Magnus on a 30-caliber gun is only a noise suppression loss of 1 - 4 dB compared to using a dedicated 30 caliber Magnus suppressor. Also less back pressure when the can is a little oversized. I very much like the idea of having one can that can work for a wider array of calibers, if the suppression loss isn't even distinguishable to human ear. My Ultra 7 is for a 30 caliber and it's very quiet on my 223's....Certainly not loud enough to justify spending another $1,000+ on a can dedicated for a 223.