For Switch-Barrel Guns, How Do You Maintain Accurate Scope Zero?

[kai]

I will be getting my first custom switch-barrel (like Savage) rifle with various barrels for hunting and practicing and have been wondering the best way to maintain the scope zero when changing barrels.

The receiver will have a rail for the scope(s).

Do you re-zero the scope each time you change the barrel, or do you have a dedicated scope that is zeroed for each barrel?

 

[Barrelnut]

Every good rifle should have a good log book. I do not switch barrels with different calibers often, but I do use different weight bullets and loads in the same rifle. To keep track, I count the clicks from top down for vertical and from the left for windage for each load. Then adjust the turrets and their zero reference points accordingly.

 

[yorke-1]

I've done it both ways, where I have a separate scope for each barrel and where I make adjustments to the zero for each barrel.

If the barrels are in similar chamberings it worked well to just make adjustments to the scope. The adjustments were typically pretty minor. This method worked best for me on a 3 barrel gun built by Jim Borden with 270 RUM, 7mm RUM and 338 Edge barrels. The adjustment from one barrel to the next was less than 1 MIL and it was consistent every time.

On something with a more dramatic change in caliber it worked better to have separate scopes. I had a Savage which I'd change between 22-250, 260 Rem and 358 Win barrels. That one used two different scopes because the POI shift was more than 6 MOA between the 22-250 and 260 and a 20x scope was pointless on a 358 Win. It was the same when going from a 6.5-06 to a 338 Win Mag on the long action Savage.

 

[MagnumManiac]

Unfortunately it is very rare to have a switch barrel rifle that maintains zero between barrels.
Mine are very close, but still different if using the same scope.
Another option, more expensive obviously, is to have seperate scopes zeroed in QD mounts for each barrel.

If using the same scope.
You need to sight in your most used barrel, zero your turrets, switch barrels and shoot without adjusting the scope and measure how far off you are, take notes once you have re-sighted THAT barrel.
Because you zeroed your turrets, you can then adjust back to zero when you switch back to the first barrel.
I have 2 rifles, Win Model 70's, with 3 barrels each, each barrel requires a different zero when using the same scope. I try to tune my loads for similar impact, but it doesn't always work. My 264WM barrel shoots 4" high and 3" right compared to my 270 Weatherby barrel, and my 300WM barrel is the one my turrets are zeroed with and the 270 Weatherby barrel shoots to same elevation but 2" right of the 300WM barrel.
My other rifle is similar, it has barrels in 22-250AI, 6.5x47 Lapua and 260AI.
I have 2 F-Class rifles that use different barrels depending on range based on Rem 700 actions, they both require very little adjustment for zero, as the barrel shoulders and the action mating services are precisely fitted to one another. I can spin on one, shoot a group, then spin on another and shoot a group with less than 1/2" difference in POI.

Cheers.

 

[tbrice23]

I switch barrels fairly often on Savage rifles. All are hunting weight barrels ( magnum sporter, #5, #3b) I'm under the impression the barrel wall thickness matters.
Sooo,
new barrel= all bets are off on scope zero.

The log book idea is a good idea.

 

[kai]

Thanks for all the comments so far...

This will be my first switch barrel gun so it's good to hear your comments. My build will have an ARC Nucleus action and it will use their new Barloc barrel torquing device. I'm hoping that each individual barrel will maintain its own zero relative to the scope when removing it and reinstalling it to the action.
Changing to a different barrel will most likely not match the scope's zero and will need a solution to re-zero the scope to the different barrels.

My thoughts so far...

• Having multiple high end scopes for each barrel would be expensive and inconvenient.... not ideal.
• Keeping a log (or label taped to the scope) can provide the adjustment data needed for each barrel, provided that the barrels go back to the same point of impact when they are reinstalled in the action. But there's always the chance that a mistake could be made when resetting the turrets' zero settings, and that could necessitate a re-zeroing of the scope by shooting the gun.... not ideal.
• I'd like a better solution that allows the scope to be zeroed for each different barrel/cartridge without loosing the original zero setting.... I have an idea....

 

[yorke-1]

I'm waiting on one of the Nucleus actions as well, they look like a pretty nice action for the money. Now to wait for it to show up!

Another approach to zeroing each barrel would be to simply enter in a non-standard zero in whatever ballistic app you use. For example, I use the Shooter App most of the time and it allows me to set up an off set zero for each load. You could screw the most used barrel on, get your load all dialed in, then zero your turrets (and set a zero stop if you have one). For the next barrel you throw on there, try shooting it and see how close the impact is to the zero from the first barrel. If it's not that far off, just set an off set zero for that load. Instead of saying it's zeroed at 100 yards it would be zeroed 1.3" low and 2.7" right at 100 yards. Then all of your corrections given by the app would account for your non standard zero.

I've used this method before with good results. It gets a little tough if you don't have a zero stop though and dial multiple revolutions. I was off by more than one full revolution on more occasions than I'd like to admit to! LOL

 

[kai]

Yorkie-1, Thanks for your comments, I didn't think of that system. I think that my aging mind would end up forgetting the adjustments made and I would either loose track of the necessary adjustments for each barrel or load, or that in a rush, I'd get confused or wouldn't have time to look at my app for the adjustment to be made.
I too have been off by a revolution on my turrets. It seams to happen at the worst time.

I'm looking for an "idiot-proof" solution where I won't loose track of my original zero or any adjustments made, or needed to be made, and still be able to set a multitude of alternative zeros for my various loads, cartridges and barrels.

The ideal system would allow the shooter to reset the scope's zero when changing the barrel (or the load), then be able to go off hunting without needing any additional adjustments other than the normal ranging and ballistics for that load.

 

[MagnumManiac]

Unfortunately, your idiot proof solution is most likely not attainable.
Having had several switch barrel rifles over the years, none being a Savage with a nut, most being Rem 700's, Win Model 70's & a couple of BAT actions, all with precision machining would change POI between barrels due to barrel harmonics, not all loads or barrels are pointing in the same direction at bullet release.
As I stated, zeroing one barrel then tracking the other one(s) and noting how far off they are and recording that info, either by log book or noting it on your drop card, is the most accurate method.
I have played with Sauer switch barrels and even those shot differently between cals, it's just a fact of switch barrel life.

All I can advise it to have ALL mating services precisely machined, which essentially is to have the action blue printed and trued.
My rifles are so precise that I can 'spin on' a barrel and the witness marks align perfectly when the barrel nips up under it's own torque. I have no need to use a barrel vise and wrench, they never get loose throughout a match or when hunting. Holding the action between the knees and tightening by hand is sufficient for my use.

Cheers.

 

[kai]

MagnumManiac... thanks for sharing your comments.
The custom Nucleus action that I will be using will be built on new and expensive machinery that should be very precise.

It sounds like you have a system well sorted out for your switch barrel guns. Since this will be my first switch barrel gun I'd like to ask, how repeatable is the zero when removing and reinstalling the same barrel?

I like your idea of simply spinning on a barrel by hand without needing tools. I'm planning on using the Barloc device by the maker of the Nucleus action to allow the user to screw the barrel in by hand to the witness mark, then use the Barloc "clamp" to torque the barrel's threads to the receiver's threads.

I understand that an idiot proof system with multiple, repeatable zeros on a single scope may not be attainable using conventional methods.

I'm developing an unconventional method that would enable the user to establish and use a multitude of zeros on a single scope and not loose the original (primary) zero.
This would be useful for people who would like to shoot different loads in the same barrel or even different barrels in the same gun. My solution would cost some money to develop and I'm currently trying to figure out if would have enough value to other shooters to justify the investment.

 

[Tidus56]

Maybe West Texas ordinance switchlug would have filled your needs. Check it out on their site.

 

[kai]

The ARC Barloc is similar to the West Texas Ordinance Switchlug.
I prefer the Barloc for use with the Nucleus action. It has some unique features that make it a better fit for use with the Nucleus action. The Nucleus action doesn't require that the recoil lug be pinned to the receiver. It is indexed with at tab on the lug at the 12 o'clock position that fits into a slot in the bottom of the scope rail.

 

[dok7mm]

I have 3 barrels on my 6.5 Sherman set-up by WTO. So far, the max POI change with my #1 barrel has been right at 1/2 moa. This is shooting a 3-shot group, removing barrel then replacing, firing 3 more. I did this a total of 4 times, just to check. The last two groups nearly touched.

I may be missing the OP's point, but any barrel I have on for shooting or hunting will be zeroed. I could care less on the FF barrel. I don't really see myself changing barrels that often.

On my 7STW, I have a 9 and a 8 twist SwitchLug refit being done @WTO. I'm planning to also add a 264wm, as soon as I get a reamer speced.

 

[kai]

I'm looking for an effective and practical way to have repeatable zeros on a single scope to facilitate using multiple loads and barrels on a rifle.

I realize that each load and/or barrel will need to be zeroed initially to establish the proper scope settings.

I travel long distances to shoot and hunt and would like to reduce the number of complete rifles and scopes that I'd need to travel with. I'd also like the benefit of being able to change barrels without having to sight in the scope each time to be confident that the scope is properly zeroed for each barrel or different load.