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A good idea ? - barrel threads

 
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  #1  
Old 09-22-2005, 09:59 AM
ds ds is offline
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A good idea ? - barrel threads

If I have ever had a good idea the chances are someone else already thought of it, or it was not so hot. Now with that in mind as anyone else considered barrel threads, as in on the end on the barrel that you attach a tuner, muzzle break or moderator to.

With hammer forged factory barrels I can see how it is easier for it to be threaded like that, as the barrel starts out as a short fat tube and is hammer profiled and rifled. However on cut rifled or button rifled barrels you start off with a blank, about 33mm in diameter.

So here is the idea when you profile, any contour LV, HV etc why not leave an inch or two of barrel blank at the end of the barrel, counter bore it over bore diameter and thread the outside. It need not be the whole 33mm dia. unless you wanted a heavy integral tuner, it could be the same profile as the rest of the barrel, to that you could attach a moderator, tuner or muzzle break.

As to why do it that way, well with a conventional thread you may open up the bore right where you want the tightest part at the crown, lapping after threading goes a long way to solving this I guess but you still end up thinner metal at the crown which may or may not heat up more. In effect what is done now is to join two pieces of metal at a critical part of the barrel.

The question is why not counter bore the barrel and put the threads where they are not affecting the crown or any rifled part of the barrel.

So what am I missing?

David.
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Old 09-22-2005, 10:47 AM
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Re: A good idea ? - barrel threads

i think you are missing the <font color="red"> crown </font> when you counter bore the barrel for internal threads. Some of the "smiths" here might know how to put the crown back in the counter bored end, i dont think it would be feasable. jm2c worth though.
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Old 09-22-2005, 11:23 AM
ds ds is offline
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Re: A good idea ? - barrel threads

d-a,

Not sure a crown is needed, as one of the trends with BR rifles now is to have the end of the barrel cut off straight, no crown. Provided the barrel could counter bored with a 90 degree reamer then I think it would in effect be the same thing.

David
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Old 09-22-2005, 07:28 PM
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Re: A good idea ? - barrel threads

sounds like some potential accuracy loss.the moment the bullet is released, the gases would blow by and in front of the bullet making very terbulant air for the bullet to go through.might actually make it kick a little harder too!
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Old 09-22-2005, 09:11 PM
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Re: A good idea ? - barrel threads

Ive been shooting through what smallbore shooters call a bloop tube (essentially a mechanical sight radius extention) that extends between 9 and 16inches forward of the muzzle... just like what we are talking about here. Accuracy is improved even when using a scope, so even with subsonic loads, gas over running the bullet is no problem.
Just about every olympic smallbore medal won in the last dozen years was won firing through some type of extention. Ditto for precision air rifle.
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Old 09-23-2005, 06:50 AM
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Re: A good idea ? - barrel threads

ds,
I understrand your principle of an integral shrouded muzzle and it sounds feasible, but i dont think it would be very practical.

Yes, a counterbore and a crown could be machined by any skilled smith and the out side diameter threaded for some kind of device but i think it would be somewhat "flimsey" and easily damaged, also the barrel harmonics may be compromised regardless of a barrel tuning device, posibly renderring the barrel untunable.

I think the term crown is not being used broadly enough here as crowning is the operation of finishing off the muzzle of the barrel.
Let me assure you, barrels are not just "cut off", they are faced perpendicular to the bore effectivly creating a 90 degree crown.

The crown only needs to be a small accurately machined surface emulating from the bore creating a true and even juncture between the bore and the muzzle
This also applies to recessed and 11 degree crowns, which must also be machined accurately to the bore. If this facing is not perfectly perpendicular, gas will escape unevenly past the bullet on exit from the bore, causing an imbalance and bullet upset.

Deep threads will not effect a crown, although they would weaken the muzzle of the barrel if they to encroach to near to the bore, similar to what i said earlier regarding your extension.

But Hey! dont let these comments stop you from trying this principle, after all, without experimentation where would we as shooters be today.
If it works, i will be the first to stand up and cheer.

Ian.

"I meant to shoot the pike but the duck got in the way"
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Old 09-23-2005, 02:47 PM
ds ds is offline
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Re: A good idea ? - barrel threads

Thank you for the replies,

I need to give it more thought. I also spoke with a couple of people who have forgotten more than I will ever know about this. Seems like I am worrying about nothing with regard to threading the end of the barrel in the usual way, so all my idea would do is to make the job more difficult - never a good thing.

The next rifle build will not be until next year anyway so I have time to think it through.

David
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