Understanding the regulation of double barrel rifles

[Sideshow]

View attachment 318890


How is that for brevity

Love this picture says it in 500 words would be in a thousand words if you gave us the side view pic as well to show yaw

 

[Tintin]

(or, just move the red dot to split the shots and enjoy shooting the rifle!)

When zeroing a dot (or a traditional optic) on a double, I'm interested to hear which approach folks here are taking.

A. Zeroing to the Mean Point of Impact (MPI) of the right barrel (typically fired first); or
B. Zeroing to the MPI of the left barrel (typically fired second); or
C. Zeroing to the MPI between the respective MPIs of each barrel - as @AimSmall suggests above.

Hope that all makes sense.

For lack of any information to the contrary, I have my dot zeroed to the right (first) barrel MPI.

Thoughts?

 

[tristan didge hunter]

When you buy a DR it is almost paramount to reload if you want good regulation or you are just lucky

yeh ill defo be reloading it, just got given this box of ammo to try out. the dies are in the post. hopefully i can get it going well.

 

[tristan didge hunter]

I think you should shoot it at 100m.
I have a Merkel 961L double rifle drilling in 9.3x74R. It took me a long time and a lot of testing, years. I really didn’t know what I was doing. However reading Graemes book and talking to a Merkel trained gunsmith got me over the line.
When testing I always shoot the second shot within 8 seconds of the first shot. I was told this is how Merkel regulate them. When I started doing this it made a significant difference on the target.
Also a lot of European 9.3x74 doubles are regulated at 100m. Mine was and I have the factory test target.
Those two things and Graeme Wrights book solved my issue.

Now it shoots Woodleigh 320 grain RNSP at 2100fps at about an inch apart at 50m or even slightly less. And at 100m just kissing, “IF” I fire both shoots within 8 seconds.
Have a look at the below 50m target. The two shots on the top right were fired at leasure, minutes apart. They were 4 inches apart no crossing. Similar to yours.
The two shots on the top left are fired about 8 seconds apart.
Second photo is at 100m.
I hope this helps you a bit.

jeez are you shooting with iron sights?? thats a bloody good grouping at 100mtrs with iron sights! ahha im pretty sure even if my gun was regulating perfectly i couldnt shoot a group like that with iron sights at 100mtrs with that caliber ahha not bad

thanks for the advice tho, i was doing exactly what you said... shot one walked down looked at target then shot the second within a couple mins or so. ill try doing the regulating with 8 sec gaps between shots on each barrel and see the difference.

i didnt know i could use bullets as heavy as 320gn in the 9.3x74. thats good to know. i might try something heavier if i have no luck with the 286gn pills i bought.

defo not shooting well at all with the box of ammo i got given.

 

[Tintin]

When zeroing a dot (or a traditional optic) on a double, I'm interested to hear which approach folks here are taking.

A. Zeroing to the Mean Point of Impact (MPI) of the right barrel (typically fired first); or
B. Zeroing to the MPI of the left barrel (typically fired second); or
C. Zeroing to the MPI between the respective MPIs of each barrel - as @AimSmall suggests above.

Hope that all makes sense.

For lack of any information to the contrary, I have my dot zeroed to the right (first) barrel MPI.

Thoughts?

^ Obviously this point is somewhat academic with the tight regulation that some rifles deliver.

 

[Huvius]

even if my gun was regulating perfectly i couldnt shoot a group like that with iron sights at 100mtrs with that caliber

This is an excellent point.
Seems like everyone wants a DG double regulated to shoot MOA at 100yds but the truth is, 95% of hunters aren’t able to shoot MOA at any distance with an open sighted DG bolt rifle offhand or off sticks.
The notion that one would require it from a DG double is completely silly.
I suggest, as some here have, that most folks’ individual barrel grouping wouldn’t be as good as some say they demand a composite group from both barrels.

 

[degoins]

This is an excellent point.
Seems like everyone wants a DG double regulated to shoot MOA at 100yds but the truth is, 95% of hunters aren’t able to shoot MOA at any distance with an open sighted DG bolt rifle offhand or off sticks.
The notion that one would require it from a DG double is completely silly.
I suggest, as some here have, that most folks’ individual barrel grouping wouldn’t be as good as some say they demand a composite group from both barrels.

I think this is where some people blame their doubles for problems, they themselves created by trying to treat their double like a bolt rifle.

 

[Schroeder]

jeez are you shooting with iron sights?? thats a bloody good grouping at 100mtrs with iron sights! ahha im pretty sure even if my gun was regulating perfectly i couldnt shoot a group like that with iron sights at 100mtrs with that caliber ahha not bad

thanks for the advice tho, i was doing exactly what you said... shot one walked down looked at target then shot the second within a couple mins or so. ill try doing the regulating with 8 sec gaps between shots on each barrel and see the difference.

i didnt know i could use bullets as heavy as 320gn in the 9.3x74. thats good to know. i might try something heavier if i have no luck with the 286gn pills i bought.

defo not shooting well at all with the box of ammo i got given.

No sorry mate, not open sights. That is with a Zeiss V6 1.1-6 scope.
Last time I did anything with open sights, I counted eleven toes…

 

[tristan didge hunter]

i got an email back from merkal. they regulated the rifle in 2013 from factory with "Norma Vulcan 15.0g bullets with 232gn projectile. the norma website says they are going 2560 fps. i was using a 286gn bullet from seller & bellot. so very different and slower bullet id imagine so this makes sense why its shooting how it is. now i just need to figure out if i can get the heavier barnes TSX in 250gn or 286gn bullets going at a velocity fast enough to regulate the rifle well. or ill have to go back to a lighter pill n try settle with that, but i cant find a projectile available in 232gn weight. 250gn is th elightest i can find and closest to how it wa sregulated, but the fatsest i can get that bullet going (acchording to ADI safe loading data.) is 2330fps which is quite a bit slower. any advice on how to get it shooting better with a heavier bullet? am i left with just trying to push the velocity as fast as i can without pressure signs? and settle for the best i can get it at 50mtrs?

 

[Schroeder]

Woodleigh make a 232 grain 9.3mm bullet.
It’s a Protected point bullet and would be a useful bullet for a variety of game like deer pigs etc. I would try 2209/H4350 as per the Woodleigh manual and see how it shoots.

 

[tristan didge hunter]

Woodleigh make a 232 grain 9.3mm bullet.
It’s a Protected point bullet and would be a useful bullet for a variety of game like deer pigs etc. I would try 2209/H4350 as per the Woodleigh manual and see how it shoots.

yeh i saw them ones, cant find them in stock anywhere in Aus yet? any ideas on where i may find some?!

 

[Tintin]

yeh i saw them ones, cant find them in stock anywhere in Aus yet? any ideas on where i may find some?!

Grant at SamHuntVic has them listed as in stock.

https://samhuntvic.com.au/product/woodleigh-products/

 

[Schroeder]

yeh i saw them ones, cant find them in stock anywhere in Aus yet? any ideas on where i may find some?!

10 boxes in stock. Victoria. Cheap postage.
You might not see them for a while, so think carefully about how many to purchase.

Woodleigh Bullets & Products - :SAMHUNTVIC:

NEW STOCK *27/07/2025. CAT 68 .303 British 215gr RNSN CAT 65C .308 220gr RNSN. We will list here, any new production in the last couple of weeks. * Please check the date above. All products which are available are in the bullets list. We are keeping a list of customers who would like to be

samhuntvic.com.au

 

[Altitude sickness]

This is an excellent point.
Seems like everyone wants a DG double regulated to shoot MOA at 100yds but the truth is, 95% of hunters aren’t able to shoot MOA at any distance with an open sighted DG bolt rifle offhand or off sticks.
The notion that one would require it from a DG double is completely silly.
I suggest, as some here have, that most folks’ individual barrel grouping wouldn’t be as good as some say they demand a composite group from both barrels.

I can not shoot MOA accuracy with buckhorn iron sights. But that doesn’t mean the rifle doesn’t need to have that capability.

If the rifle produces 6” groups. The human now has to shoot MOA to get 7” groups at 100 yards.

Add nerves, wind, unstable rest and your real world group is now 9-10”

I want the rifle at MOA so when you add in my lousy shooting I now have 2-3”

 

[tristan didge hunter]

I can not shoot MOA accuracy with buckhorn iron sights. But that doesn’t mean the rifle doesn’t need to have that capability.

If the rifle produces 6” groups. The human now has to shoot MOA to get 7” groups at 100 yards.

Add nerves, wind, unstable rest and your real world group is now 9-10”

I want the rifle at MOA so when you add in my lousy shooting I now have 2-3”

yes 6inch groups at 50mtr is not ok ahah thus my post here to ask for help to regulate the rifle. i think your right, if its 6insh at 50 it would be 10inch at 100 ahah not ok , ill get there tho n get it better. members have been very helpful with advice thankfully

 

[Altitude sickness]

If you don’t load your own ammo. Send it to JJ to work up a load for it. Or sell it and buy a MOA magazine rifle for one third the price.

 

[tristan didge hunter]

If you don’t load your own ammo. Send it to JJ to work up a load for it. Or sell it and buy a MOA magazine rifle for one third the price.

nah that wouldnt be any fun would it sounds way to easy hahah

 

[tristan didge hunter]

i suppose no one here is in Australia and has some 9.3x74r brass to sell?

 

[deewayne2003]

If you don’t load your own ammo. Send it to JJ to work up a load for it. Or sell it and buy a MOA magazine rifle for one third the price.

LOL.... He lives in Australia so I doubt it would be cost effective to ship the rifle to Oklahoma for load development.

Grant at SamHuntVic has them listed as in stock.

https://samhuntvic.com.au/product/woodleigh-products/

Grant is a good man, retired Australian army and used to ship direct to me in the states with my ATF permit until the AFP said that he had to have an export permit for each order.

If your in OZ I would highly suggest SamHuntVic

 

[Rubberhead]

@One Day... if you're still around, that's exactly the way I understand it. I don't have personal experience with regulation on a SxS rifle but an O/U definitely has a different trajectory from the under barrel than it does from the over barrel. It's not a yawing effect, though because both barrels are in line with the receiver but the Over barrel does have a much greater muzzle jump from recoil so even when the barrels are perfect at 100 yards, the over barrel will shoot noticeably higher at 200 yards, in my gun anyways.

I think the muzzle jump of a bolt gun gives that action type "built in" extra line-of-sight range that we've just come to take for granted.

I might change my mind on this later because I'm learning more every day. The addition of a second barrel to a rifle is far, far from trivial when it comes to trajectories.