Gunsmithing should barrel threads start at the same exact point?

[Long Range]

I bought this linear compensator, which has the logo on the right side.

I then installed this on a barrel from the same manufacturer and it did not line up like that. I figured they must have timed it somehow to get it to line up.

Then I purchased 2 faxon barrels. To my surprised I screwed the compensator on the two barrels and it lined up perfectly on the right side.

I am confused now, if the compensator lined up correctly with the faxon barrels, this tells me that a barrel threading should start at the same point on the barrel. However, this was not the case on the barrel manufacturer who made the compensator.

would anyone know if the threads should all the the same so screwing things on line up exactly the same between all barrels?

 

[Steel head]

The faxon manufacturing process might promote something like that, you can’t expect another manufacturer to be the same.

 

[Clark]

I have screwed in enough rem 700 take off barrels to think that the threads are clocked. The sights are either on top or on the bottom.

I do not have that ability in my shop when I single point cut threads on a manual lathe.

 

[Long Range]

The faxon manufacturing process might promote something like that, you can’t expect another manufacturer to be the same.

I actually made a mistake.

I tried it on a ballistic advantage 300 blackout barrel and a faxon 308 barrel. Both had the compensator stop at exactly the same point with the logo on the right side.

 

[Mordamer]

There is no standard for clocking muzzle threads. It isn't easy to do on a manual lathe and so you'll likely find that they are randomly clocked. I suspect that faxon and BA probably use a jig that references off the barrel extension and they thread mill instead of single point cut. This would explain why they happen to clock the same, but it still might just be random luck that you got 2 that are the same.

 

[LRI]

An example of why this isn't the easiest thing to do:

Lets take a 16 pitch thread and break it down. If you have 360* in a circle and you divide it up into segments you get what?

1-360*=.0625"
2-180*=.03125"
4-90*=.015625"
8-45*=.0078125"
16-22.5*=.00390625"
32-11.25*=.001953125"
64-5.625*=.0009765625"
128-2.8125*=.00048828125"
and so on... the numbers get small very quickly.

What this all means: suppose you have two barrels fitted with a fixed front side blade and you want to time them up so that they are exactly 12 o clock at the installed torque value.

To be within a measly 2.8125 degrees (which you can see with the naked eye all day) you have to machine your barrel tennon to less than 50 millionths of an inch (less than half a "tenth") from where the thread start point is to the shoulder where it marries up with the lug/receiver face. You also must use the exact same thread lubricant applied in exactly the same way and have your barrels at exactly the same ambient temperature when installed. The hardness of the steel must be the same and the surface finish on the flanks of the barrel threads must also be identical. EDIT: In addition, you also will need to have your pitch diameter exactly the same as well.

For any shop, this is a challenge and challenges get solved with a big pile of money. To truly do this correctly, barrels would literally have to be ground on the kinds of machines that make tooling for cnc mills. The heat treatment would have to be very, very consistent which is not easy to do with barrel grade (typically 416) stainless because the chemistry is very complicated. Factor in also that when heat treating a batch of steel you can have big swings in the outcome just by where/how the material is stacked in the oven. When things have be "Jonny on the spot" for a particular application, (aerospace/defense/medical/nuclear) the print will designate it and this always drives the costs up by a considerable margin.

The fact that your compensator lined up is likely coincidence or that it has symmetrical ports and one just happened to catch it right when you snugged it up. Treat it as an exception, not the norm.

Hope this helps.

C.

 

[Clark]

Chad, you may be right, but ... the thread crush allows ~~ x degrees or discretion if the torque can vary from 25 foot pounds to 250 foot pounds. ............and I have shot some great groups with finger tight barrels in a Mauser with inner lock ring.

 

[Qtip]

An example of why this isn't the easiest thing to do:

Lets take a 16 pitch thread and break it down. If you have 360* in a circle and you divide it up into segments you get what?

1-360*=.0625"
2-180*=.03125"
4-90*=.015625"
8-45*=.0078125"
16-22.5*=.00390625"
32-11.25*=.001953125"
64-5.625*=.0009765625"
128-2.8125*=.00048828125"
and so on... the numbers get small very quickly.

What this all means: suppose you have two barrels fitted with a fixed front side blade and you want to time them up so that they are exactly 12 o clock at the installed torque value.

To be within a measly 2.8125 degrees (which you can see with the naked eye all day) you have to machine your barrel tennon to less than 50 millionths of an inch (less than half a "tenth") from where the thread start point is to the shoulder where it marries up with the lug/receiver face. You also must use the exact same thread lubricant applied in exactly the same way and have your barrels at exactly the same ambient temperature when installed. The hardness of the steel must be the same and the surface finish on the flanks of the barrel threads must also be identical. EDIT: In addition, you also will need to have your pitch diameter exactly the same as well.

For any shop, this is a challenge and challenges get solved with a big pile of money. To truly do this correctly, barrels would literally have to be ground on the kinds of machines that make tooling for cnc mills. The heat treatment would have to be very, very consistent which is not easy to do with barrel grade (typically 416) stainless because the chemistry is very complicated. Factor in also that when heat treating a batch of steel you can have big swings in the outcome just by where/how the material is stacked in the oven. When things have be "Jonny on the spot" for a particular application, (aerospace/defense/medical/nuclear) the print will designate it and this always drives the costs up by a considerable margin.

The fact that your compensator lined up is likely coincidence or that it has symmetrical ports and one just happened to catch it right when you snugged it up. Treat it as an exception, not the norm.

Hope this helps.

C.

Perhaps I am misunderstanding the question, but I think that your math is off. The 360 degrees should be dividing the circumference of the barrel not the thread pitch.
3.1416 x diameter of barrel /360 degrees will give the distance of travel

ex 3.1416 x 1.25 / 360 = 0.010” of movement per degree of rotation of the barrel.

doesnt change the level of difficulty to index the thread.

 

[Mordamer]

Perhaps I am misunderstanding the question, but I think that your math is off. The 360 degrees should be dividing the circumference of the barrel not the thread pitch.
3.1416 x diameter of barrel /360 degrees will give the distance of travel

ex 3.1416 x 1.25 / 360 = 0.010” of movement per degree of rotation of the barrel.

doesnt change the level of difficulty to index the thread.

The part where you said you misunderstood was correct.