Switch Barrel Rigs & Headspace

[MoneyWaster]

I have a Defiance Deviant action with both a .308 bolt and a .223 bolt, and I'd like to build a switch barrel rig with it. I plan on doing a 20 Practical for Nevada squirrel shooting, and a 6.5X47 Lapua for banging steel. What I don't know is; if I have barrels threaded and chambered by a smith, would I retain the same headspace each time that I switched barrels?

Thanks in advance?

MW

 

[spife7980]

Yes. Since each barrel should be cut according to its respective bolt the unscrewing and reinstalling would be a repeatable operation.

Edit: provided hes cutting you shouldered barrels and not a barrel nut set up.

 

[Toby Bradshaw]

... if I have barrels threaded and chambered by a smith, would I retain the same headspace each time that I switched barrels?

Yes.

 

[BoydAllen]

I don't really understand your question. Each of those barrels would be fitted individually to your action, with the appropriate bolt in place. What exactly are you concerned about from a functional point of view? Certainly a smith could measure the action with each bolt in place and then produce barrels that fit it without having to have the action in hand, but that would not require that the distance from the front of the action to the bolt face be the same for both bolts.

 

[MoneyWaster]

Yes. Since each barrel should be cut according to its respective bolt the unscrewing and reinstalling would be a repeatable operation.

Edit: provided hes cutting you shouldered barrels and not a barrel nut set up.

They would be shouldered barrels. I'm not interested in doing a barrel nut.

That's exactly what I was hoping to hear. Thanks!

MW

 

[MoneyWaster]

I don't really understand your question. Each of those barrels would be fitted individually to your action, with the appropriate bolt in place. What exactly are you concerned about from a functional point of view? Certainly a smith could measure the action with each bolt in place and then produce barrels that fit it without having to have the action in hand, but that would not require that the distance from the front of the action to the bolt face be the same for both bolts.

I agree with your statements. I just wasn't sure if there were any issues created by removing and replacing barrels. Perhaps torque values could result in some headspace change? I don't know, but I would think so. That's why I'm asking.

MW

 

[smoooth]

I recently watched a video of a guy who had flats milled at the end of the barrel (behind the threaded muzzle in this case) and would chance barrels without removing the action from the stock. He had done a lot of testing and with a properly bedded action, 30-40ft.lbs. torque was perfect and repeatable.

This was for a PRS rifle, not a BR / FTR rifle.

 

[Willie]

I just dropped off a 6.5 wildcat at my smith to have it set up with a SwitchLug for quick change of barrels by hand. Barrels are changed by loosening the lug, screwing out the barrel by hand, switching barrels, tightening lug with torque wrench.

I was very concerned about headspace, as one barrel is a fire forming barrel. He assured me the headspace would be the same. Now I just worry that my 1/4 moa barrel will become a 1/2 moa barrel. Guess I'll find out in 3 months. Same reamer, but stuff happens.

 

[dmoran]

@MoneyWaster + @Willie

Don't sweat barrel swaps. When using shouldered barrels, you have a solid joint that is highly repeatable.
As do others, myself have been swapping barrels in and out with regularity for +15 years, without any accuracy indifference or headspace issues.

It's not uncommon for me to take 2 or 3 barrels with me to my range. Typically I will have 3 barrels in cycle for each rifle: a current in use match barrel, a test barrel, and a fresh barrel getting up and going. Plus old barrels that I use for fire-forming and practice.

Log the scope zero's for each barrel, and your good to go. Example:
Bartlein#2 - 100yd Zero <> 18.4-MOA Left / 6.1-MOA Up
Bartlein#2 - 1000yd Zero <> 19.1-MOA Left / 30.6-MOA Up
(based from the bottom of the elevation turret, and right end of windage turret)

Good Luck
Donovan

 

[watercam]

They would be shouldered barrels. I'm not interested in doing a barrel nut.

That's exactly what I was hoping to hear. Thanks!

MW

The sure fire way to maintain precise headspace is to make sure the barrels have an index mark on them to line up with an index mark on the action. Simply line up the marks. To be overly sure have go/no-go gauges and reassure yourself that they are correct.

 

[ridgeway]

The HS is set off the go gauge and is a dimension that can be measured. The zero HS dimension is measured from action face to bolt face. Chambering, simply measure from tenon shoulder to end of go gauge and account for any "crush" preferred. Both barrels regardless of chamber should share this same dimension. If not, they aren't the same. Whoever doesn the work should know that and chamber accordingly. No indexing involved.

 

[Toby Bradshaw]

I recently watched a video of a guy who had flats milled at the end of the barrel (behind the threaded muzzle in this case) and would chance barrels without removing the action from the stock. He had done a lot of testing and with a properly bedded action, 30-40ft.lbs. torque was perfect and repeatable.

This was for a PRS rifle, not a BR / FTR rifle.

Barrel changes with the action in the stock are nothing new and don't require any flats on the barrel.

 

[smoooth]

Thanks Toby, but the whole point of what I stated was that an action wrench and barrel vise were not needed. My apologies if I did not explain that clearly, it made sense to me at 3am......

 

[smoooth]

https://drive.google.com/file/d/0BwA82uxKXVSSX05icnlpVWk4d28/view?usp=sharing

 

[dmoran]

https://drive.google.com/file/d/0BwA82uxKXVSSX05icnlpVWk4d28/view?usp=sharing

If that is all the torque one wants to use, all that would be needed is a strap wrench (on the barrel), and save the cost, work, and look of machined flats.
Personally I would not want my barrels torqued on that lightly (been down that road), nor do I want to torque against the actions bedding and screws.
Donovan