Negative effects of threading the muzzle

[jackieschmidt]

I think that the "slipping a gauge pin into the muzzle" test should be repeated after the muzzle device is torqued up. It would more than likely reverse the flaring effect, and introduce a restriction at the muzzle.
Just a side effect of using a V thread.


Time to start using buttress or square cut threads for all muzzle device thingys!

You might have a point.
A century ago the designers of the original 1903 Springfield decided to use a square, or box thread on the barrel tenon to eliminate the closure of the chamber when tightened to the specified level that the department of defense deemed sufficient to insure a permanent joint. The problem really was not with the barrel, but rather the thin cross section of the receiver ring.

In theory, a Square Tread does place a joint only in linear tension, not linear and compression tension.

 

[Jonnyofalltrades]

You might have a point.
A century ago the designers of the original 1903 Springfield decided to use a square, or box thread on the barrel tenon to eliminate the closure of the chamber when tightened to the specified level that the department of defense deemed sufficient to insure a permanent joint. The problem really was not with the barrel, but rather the thin cross section of the receiver ring.

In theory, a Square Tread does place a joint only in linear tension, not linear and compression rension.

Hatcher's Notebook has lots of these stories, correct?
I've always meant to get a copy and read it.
So many things have been tried before.

I'm not sure, but I think that we would see things coming loose a lot more with a buttress or square thread.
Radial forces from tightening a V thread are a big part of why the stay put after tightening.
I've heard stories that a Whitworth thread(55°) is more likely to work loose than a 60°, and that's only a 2.5° difference in flank contact angle.

 

[Alex Wheeler]

I had a barrel in the shop from a new manufacturer at the time. It was a button. Since they were newer I slugged the barrel just to get an idea. The inside matched the outside. As the barrel tapered the bore got looser. Obviously they had not figured out their process yet. It was for a guy I knew and I told him and he said chamber it. It was a 1/2 moa barrel which surprised me. It was far from winning a match but it was a decent hunting barrel. I do see a lot more variation from one barrel to the next on buttons than I do on cut barrels. That doesnt mean ones more accurate, but the loads just vary more. I like the consistency because the load data is easier to give out.

 

[SKWERLZ]

This phenomenon is not exclusive to barrels, and can be seen when machining any round , tubular stock.

Cold roll is famous for moving when cut.

 

[Bill K]

Interesting thread. However with some saying it has not effect and others saying it does, with certain types of barrel/bore, I would say the only real effect threading a barrel for a brake or suppresser would be having to maybe work up another accurate load when making or adding this to the barrel. Just my opinion.
How many thousands of barrel now come with threads or have be threaded ? It must work pretty well.

 

[jackieschmidt]

Interesting thread. However with some saying it has not effect and others saying it does, with certain types of barrel/bore, I would say the only real effect threading a barrel for a brake or suppresser would be having to maybe work up another accurate load when making or adding this to the barrel. Just my opinion.
How many thousands of barrel now come with threads or have be threaded ? It must work pretty well.

Keep in mind. All we can do is measure things, and see if any of that correlates with what we see on the target.
That is not conjecture.

 

[Carl S]

I probably thread nearly every barrel muzzle that goes into the lathe.mostly for suppressors.factory barrels come in for shortening and re threading.some target shooters have muzzle brakes,some none.i haven't seen any difference on paper at all when a barrel has had the muzzle threaded.

 

[AlNyhus]

This is a buttoned barrel chambered in 30BR that won a lot of wood for me years ago. After threading the muzzle for an early tuner effort, it became a 3/8" barrel. The bore at the muzzle after threading was a full .0008 bigger. Great f-form barrel, now.

 

[rijndael]

However with some saying it has not effect and others saying it does, with certain types of barrel/bore,

How many of those commenting shooters would notice if their gun opened up an extra 1/10th MOA? Did they go out one time, shoot a group or two, and it was good enough, so they didn't worry about it?

To me, not all opinions are equal.

 

[jackieschmidt]

How many of those commenting shooters would notice if their gun opened up an extra 1/10th MOA? Did they go out one time, shoot a group or two, and it was good enough, so they didn't worry about it?

To me, not all opinions are equal.

Of course they aren’t. Mostly because of the accuracy requirements of the Rifle.

I agree. 1/10 MOA means nothing to the vast majority of shooters, including some very competitive Disciplines.

In a Short Range Benchrest Rifle, whether Group or Score, that would be taking a Rifle with a .200 agging capability and ending up with a Rifle with a .300 agging capability.

That’s a lot.

 

[cdngary]

This is a buttoned barrel chambered in 30BR that won a lot of wood for me years ago. After threading the muzzle for an early tuner effort, it became a 3/8" barrel. The bore at the muzzle after threading was a full .0008 bigger. Great f-form barrel, now.

why didn't you cut off the thread and recrown? Wouldn't it return to your target standards?

 

[snert]

As posted, some will open up a skosh, around .0001. In effect this gives the bullet less resistance and a little extra push at the muzzle. In other words, a threaded barrel will have a higher velocity with the same load than an unthreaded one. I saw this on the internet, so it must be true.

The bullet will then ACCELLERATE as it leaves the barrel. My cousin said so and it's certainly true

 

[DShortt]

I had a barrel in the shop from a new manufacturer at the time. It was a button. Since they were newer I slugged the barrel just to get an idea. The inside matched the outside. As the barrel tapered the bore got looser. Obviously they had not figured out their process yet. It was for a guy I knew and I told him and he said chamber it. It was a 1/2 moa barrel which surprised me. It was far from winning a match but it was a decent hunting barrel. I do see a lot more variation from one barrel to the next on buttons than I do on cut barrels. That doesnt mean ones more accurate, but the loads just vary more. I like the consistency because the load data is easier to give out.

I've seen several that when slugged from the chamber, the slug was loose at 1/3 the length and literally slid out of the last 1/3 and fell out with gravity. Threw random fliers. .002" to .0025" larger at the muzzle. And those weren't even threaded.

I'll not mention the maker. It'll start another argument. They were factory barrels.

 

[AlNyhus]

why didn't you cut off the thread and recrown? Wouldn't it return to your target standards?

The barrel had already been shortened 1" prior to the threading. Given how loose it felt, another 2" would have likely had to come off. And then it would be another roll of the dice when it was threaded again....which was the whole point of this experiment. At some point, it's best to just cut your losses and move forward, even if that's a different direction.

Good shootin' -Al

 

[hogpatrol]

I have a smokeless muzzleloader barrel that I shoot sized land riders (no sabot). When I push a bullet down a clean barrel I can feel a spot where it gets easier for an inch or two then tighter. 278 grain at 2700, ES is less than 10. Sat in the safe for a year so needed to do a check, set the target at 500 meters. If it shoots good there, my old dope is good. Fouled the first shot, a little wind, hit right, then held the second a minute left. Tight, loose, threaded, unthreaded, fluted, unfluted, my 2¢, if it shoots, fuggeddaboutit. YMMV.

 

[natdscott]

The best shooting gun I have, is a cut rifled barrel with a 1/2 inch thread. I can insert a gauge pin in the end of the barrel... to the shoulder of the thread.

Do with that what you will.

Sounds like you need some better rifles.

 

[DShortt]

The best shooting gun I have, is a cut rifled barrel with a 1/2 inch thread. I can insert a gauge pin in the end of the barrel... to the shoulder of the thread.

Do with that what you will.

What is the bore diameter and what size of pin gage fits in the threaded portion to the end of the threads?
Very curious about this. PM me if you like. Not looking to stir discontent. I am interested in your observations.

 

[LVLAaron]

These are 5 shot groups from it. It's an AR with a White Oak Precision Krieger 1:7.7"

I don't recall the pin size.

 

[L.Sherm]

I wouldnt care shooting like that.
Hell theres plenty of guns that aren't threaded that aren't that capable or shooters.

 

[DShortt]

View attachment 1615091View attachment 1615092View attachment 1615093

These are 5 shot groups from it. It's an AR with a White Oak Precision Krieger 1:7.7"

I don't recall the pin size.

That's unfortunate. I'd really love to know what you saw.

As I said earlier, I've measured some unthreaded factory barrels that were out .002" to .0025". Those were unpredictable, but still definitely good enough for most hunters to be confident with. But they sure didn't show anything like what you posted.