Screw it!

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theotherpursuit

theotherpursuit

Member
Jan 24, 2020
338
13
MD, United States
In the past I’ve spoken to the best tuners and builders asking them if they could screw cut a barrel of mine. All of them advised against it stating that they were afraid it would alter the choke. At least that is how I remember it, but it’s been about ten years now.

Many barrels come from the factory screw cut. Recently shrouds became popular, and those barrels may, or may not be cut. But a vast number of brands were releasing barrels which came cut from the factory. Mine at the time was a BSA Superten barrel. 

I am curious why they were reluctant? Was the reasoning valid, or an excuse to not get themselves in the hot pot?

I did find a local gunsmith who was willing to do it if I paid for the tap size. I did, he did, and end of story. That barrel didn’t seem to have changed in accuracy, or pellet choice.

Anyone know what the real issue was/is?



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Anytime you cut material from a steel tube (barrel) the stresses in that barrel may change the dimensions slightly and there is no way to determine if or how much that will be. The method of forming that barrel will determine how much stress it may have. A hammer forged barrel will have lots of stress, a cut rifled barrel made from a stress relieved blank will have little or no stress and a button rifled barrel somewhere in between. The performance of the barrel may or may not change and I guess that is why the smiths you talked to did not want to take a chance.

Also I would never thread a barrel with a die ( I assume you meant die and not tap). Any thread on a barrel needs to be single point cut in a lathe to insure the thread is parallel to the bore. 
 
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Thank you! Your explanation is exactly what I was hoping for. I am no metallurgist, but I recall that stresses can be relieved (eg., heat treating). This reminds me of another similar topic of cryogenics which is also used to “stress relief” metals. Am I out of place to think stress relieving the barrels after cut will avoid problems, or will this only introduce other problems.

A benefit by using cryogenics could be improvement of barrel harmonics, yes? Perhaps the deep freeze will also alter the i.d. Of the barrel...

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p.s. The barrel was cut on a lathe. 
 
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The barrel that came on my Red Wolf wouldn't shoot. After all types of cleaning and polishing, AOA sent me a new barrel. The original barrel was threaded at the muzzle for the air stripper. The replacement barrel was not threaded, and uses a grub screw to hold the collar/stripper in place, and it has shot great from day one. I'm not sure to what extent the threading contributed to the accuracy problem, as a gunsmith later found a machining issue at the transfer port, but I never shot the original barrel again. I was told long ago that any type of machine work on the outside can alter interior barrel dimensions. The muzzle of my Taipan Veteran barrel is threaded, and it shoots great. So, like most things, it can probably be done correctly without much risk, but it does add a variable. 
 
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why not buy a adapter ?? i took my super 10 shroud off and installed a 1/2 x 20 UNF adapter on. mine came from best fittings UK. but Donny fl carry's them now. buy the correct size and it slips on perfict! no clipping from misalignment silencers ! i have one on my raw as well
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Yes, if you are dealing with a barrel that is not threaded, that is a great option. I used one on a Steyr and it worked fine. 
 
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why not buy a adapter ?? i took my super 10 shroud off and installed a 1/2 x 20 UNF adapter on. mine came from best fittings UK. but Donny fl carry's them now. buy the correct size and it slips on perfict! no clipping from misalignment silencers ! i have one on my raw as well
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I agree that this is an option. Part of my inquiry is to preserve aesthetics, this is clearly subjective though.

Roughly half of my rifles came from the factory screw cut, and the other half with the design you refer to above. Before ldcs were sold straight from the counter, there was quite a bit of ingenuity and resourcefulness found out there. The shroud I created for the S10 after it was screw cut was a looker and performer. I was using cf tubes from Rockwest before I became popular today. The internals were transferred from an older Logun end piece with plastic internals similar in design to Edgun’s Bat.

Regardless, the reason for my post was to learn why, not so much for an alternative. But, I really do appreciate the info provided by all.


Some of my posts, including this one, is to spark interest and input for all to learn. 

Thanks,

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Anytime you cut material from a steel tube (barrel) the stresses in that barrel may change the dimensions slightly and there is no way to determine if or how much that will be. The method of forming that barrel will determine how much stress it may have. A hammer forged barrel will have lots of stress, a cut rifled barrel made from a stress relieved blank will have little or no stress and a button rifled barrel somewhere in between. The performance of the barrel may or may not change and I guess that is why the smiths you talked to did not want to take a chance.

Also I would never thread a barrel with a die ( I assume you meant die and not tap). Any thread on a barrel needs to be single point cut in a lathe to insure the thread is parallel to the bore.
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This. I know a guy who built rifles for a multi letter government agency and built a bunch on hammer forged barrels. He would counterbore the barrel about an inch down, cut the threads on the OD @.600" long then go back in and cut the crown in the counterbore as last step. He said this made sure the crown was set were the stress in the barrel had not been relieved from the threading operation. I have personally shot three of his .308s and everyone of them shot like a laser. These were all built in the late '80s / early '90s as well.
 
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