Gunsmithing Barrel threading to an action?

Walsh

Walsh

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Oct 5, 2009
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Tuscaloosa, Alabama
#1
Let me first say that I have am just 16, have NO gunsmithing ability and am still learning (thanks to this site or I would still be a "mall ninja")!!

I understand that some say that you do not want a barrel to be too heavy to prevent the barrel from "bending". Therefore Suregeon built their 591 action with 37% more thread to support a heavier barrel with less strain on the action.

Folowing this logic, would it be possible to machine an action with 10+ inches of thread to support an extremly heavy barrel with almost no if any vibrations throughout the barrel. This would allow an straight blank countour barrel to be threaded 10+ inches for supreme strengh.

The only fault that I am seeing is that the barrel would not be free-floated for at least 10 inches.

I know this sounds really outside of the box, but would it be possible to do this? I know that it would be a very heavy action, but I am just thinking about accuaccy, not how heavy the entire action would be.

Just been thinging about this lately and wanted to ask the experts.

Thanks,
P.B.Walsh
 
#2
Re: Barrel threading to an action?

Possible; yes. Practical; maybe not so much. Necessary; I honestly can't imagine why.

There is a practical limit to the length and diameter of rifle barrels. Most barrel makers won't make a barrel over about 1.5" in diameter, and you pay extra for every inch of length beyond about 28". The limits on length are largely due to what the steel mills can furnish in certified gun barrel-grade steel, and I suspect also due to popularity.

Unless you're looking at something larger than .50, I really can't imagine any practical advantage to doing what you're suggesting. But then, I'm not a gunsmith or firearms engineer, and I don't play one on TV.
wink.gif
 
#3
Re: Barrel threading to an action?

As for the barrel, I am taling about one with a 1.30" blank. I see where your coming from about the availibility of quallity steel needed.

Mabey .50BMG, .408 CheyTAC, or the .375 Chey Tac benchrest, do you think it would make even a .10 MOa of a difference? Mabey for the "Heavy Gun" division?

Thanks,
P.B.Walsh
 
#4
Re: Barrel threading to an action?

I suppose that really the only way to prove or disprove the validity of the concept would be to try it and see. I think you would reach a point of diminishing return with about 3-4 inches of the barrel tenon threaded, and you would have to be shooting to at least 1000 yards to realize any real benefit to begin with.
 
#5
Re: Barrel threading to an action?

Anything is possible. You could take one block of steel 30" long by let's say 5or 6" wide by 5 or 6" tall, machine it properly, drill a hole in it rifle the barrel put a bolt in is and a trigger on it and you'd have a very heavy gun. Wouldn't make any sense though. The bench rest guys back in the day used to use a barrel block and not bolt the receiver to anything at all. They are still used today. There are also guys who will bed the stock for the first few inches of the barrel to aid in barrel support.

Heres a picture and an article about a rifle using a barrel block: http://www.6mmbr.com/gunweek075.html
 
#6
Re: Barrel threading to an action?

There's no practical advantage in a excessively long barrel tenon. If you're trying to support/stiffen more of the barrel then use a short barrel block right in front of the action and bed that into the stock and float the action. If you're trying to strengthen the threaded connection between the barrel and the action even a 1 to 1 ratio between tenon length and diameter is more than is needed. All you need is about a 2 to 3 ratio. Take into consideration that the threaded tenon is nothing more than bolt holding the barrel to the action. Some will disagree with this but the threads in the action can be off some as long as the thread fit between the barrel and the action allows the shoulder on the barrel and the shoulder on the action to square up and get full contact before any misalignment from the threads starts to influene the shoulder lock up. All long tenons aren't bad but the longer the tenon the more alignment issues can creep in. A tight thread fit even on a custom action can influence this shoulder lockup. As hard as we try tolerances can stack up. I believe a little loose is better than a little tight when it comes to threads. I was fortunate to be around several good smith's when I started. Keep asking questions then sort things out for yourself. Keep things simple.Enjoy the journey.
 
#7
Re: Barrel threading to an action?

P.B.,
"Therefore Surgeon built their 591 action with 37% more thread to support a heavier barrel with less strain on the action. Following this logic,"

I'm in the machine trade. This is not logic. It's sales hype.

In engineering terms threads are use to join parts together. The strength of a thread is it's ability to resist stripping when assembled. The practical limit for a thread is when its length is one and a half times its diameter.
Beyond that the increase in the ability to resist stripping is negligible.
From a manufacturing point of view, it is more expensive to make the thread longer than necessary. It's a waste of money.

In your example, you would also have to thread the action 10" deep. It can't be tapped that deep so it would have to be made on a lathe. That's a more expensive process than tapping. You also have the problem of the cutting tool being deep inside the part. You can't see it. You can see if the chips are clogging the tool. You can't get cutting fluid to the tool.

What you will get is called "a very loud noise".

The best way would be to make the receiver and barrel out of one piece.
Nobody's figured out how to do that accurately or within any reasonable cost.

No amount of thread is going to prevent a barrel from bending.
Read up on cantilevers.

A thread engages on only one flank when tightened. (one 60 degree side) If anything, the presents of a thread weakens the joint because there is less metal.

The most accurate way to join a barrel to an action is to machine and then lap mating cone shapes on each. This is essentially a valve seal, making the parts as close to solid as possible, holding them together with a third part. There are some .22LR rifles made this way. I don't know of any center fire rifles. The internal pressures are enormous.

Free floating a barrel is the process of preventing pressure on a barrel from contact with the stock or in using a sling which may bend the barrel.

The thread has no effect on the "free float". It can effect the concentricity of the bore to the action which is why it's reworked on accurizing jobs.


John
 
#10
Re: Barrel threading to an action?

In the book "Rifle Accuracy Facts" Vaughn contends that not only does the thread engage on only one flank but that the first 3 or 4 threads carry 80% of the load. He found this to enable the barrel to move when the rifle was fired which can often times explain a flyer. The barrel actually moves in the receiver. He tried loctite but it would break loose after a couple of shots and then he tried teflon tape and it worked. Yup, freaking plumbers tape in the receiver/barrel junction.

I believe he was also working with a box stock Remington 700 hunting rifle though.
 
#11
Re: Barrel threading to an action?

I have bedded the first few inches of barrel in front of the action. With or without the bedding, really made no difference. It could also be that I can't shoot well enough to tell.
 
#12
Re: Barrel threading to an action?

Take a look at Darrel Holland Rifles he did some work with the bedding blocks in his builds you can go to his site and get a look at them. Bump around the net and see if you can find anything relating to barrel stretchers ortensioned barrels. It seemed like some out of the box thinking to me
 
#14
Re: Barrel threading to an action?

Dan Lilja also builds quite a few LR hunting rifles using bedding blocks. He uses long, big honkin' barrels, and needs the bedding blocks for support. I dunno why I didn't think of that earlier.

There used to be some articles on the Lilja website detailing this stuff; I dunno if it's still there or not.
 
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