How inaccurate a double rifle when?

[Doubleplay]

What happens when you use a different ammo in a double rifle than the the type it's regulated with?
How much difference it makes under 60-70 yards where a typical DG hunt happens?

 

[Hillcountry63]

In my Sabatti it’s all over the place. Federal Swift A frames almost identical but everything else I’ve tried I get varied results of anywhere from 2 to 10 inches difference at 50 yards

 

[Tanks]

The biggest problem is the second barrel regulation. First shot, especially if one uses a red dot can be on the money, but the second shot can be quite a bit off.

When you have a left/right group like below (570 grain Cutting edge solids) at 50 meters, you do not change.

 

[IvW]

A lot....wil also vary from rifle to rifle.....but it is one of the issues with a double.....

 

[Rare Breed]

What happens when you use a different ammo in a double rifle than the the type it's regulated with?
How much difference it makes under 60-70 yards where a typical DG hunt happens?

Given I am now on my seventh DR and hand load for them all, I have found the following:
1. Regardless of powder and bullet type, match the bullet weight and FPS that the rifle was regulated with…you will be 95% there with good regulation.
2. DRs are finicky beauties…there are always exceptions but if you start at the above find out what your shots are doing…crossing at 50 yards?…slow down your FPS, too wide apart yet not crossing increase your FPS.
In all my rifles with my most recent 470 that I now have shooting under an inch at 50 yards with same bullet weight but different type bullet and powder used for regulation

 

[Velo Dog]

Double rifles are unique if not strange behaving contraptions.
I love them.
However, the only way to know how much changing ammunition specs will matter to accuracy / regulation, is to actually fire the rifle.

Without that, trying to predict how it will throw bullets from any ammunition, that is very much different than what one’s individual rifle is regulated for, is like trying to guess what the weather will be doing on one particular day, 10 years from now.

I once owned an Army & Navy double in .450 No2 Nitro.
It shot 480 gr Hornady DGX and DGS into very satisfying little groups, barrel to barrel.
Same powder charges, same primers, same brass but 480 gr Woodleighs and the groups would spread out a bit.
500 gr Hornady and Woodleigh either or both and the groups would likewise spread out more than I wanted.

I once owned a Merkel SxS in .375 H&H that didn’t regulate with the ammunition it supposedly was regulated for (Federal regular old formerly cheap 300 gr RNSP), and the right side barrel showed dangerous pressure signs, adding insult to injury.
So, I had it re-regulated to 300 gr round nose Hornady softs and solids @ 2400 fps and it was super accurate as doubles go.

However, it also regulated perfectly with Federal factory “Premium” ammunition they used to offer with 300 gr Nosler Partitions.
This, in spite of said NP ammo also showing dangerous pressure signs in my right side barrel, just like the ammunition it was supposed to be regulated with.
Except that the NP load was super accurate.
Go figure that one out, sheesh.

 

[Wyatt Smith]

The biggest problem is the second barrel regulation. First shot, especially if one uses a red dot can be on the money, but the second shot can be quite a bit off.

When you have a left/right group like below (570 grain Cutting edge solids) at 50 meters, you do not change.

View attachment 588660

Is that the Heym?

 

[Tanks]

Is that the Heym?

Yes.

 

[HankBuck]

What happens when you use a different ammo in a double rifle than the the type it's regulated with?
How much difference it makes under 60-70 yards where a typical DG hunt happens?

DOUBLEPLAY, thats a good question and I want to hear from those that know more about DRs then my limited experience. My Chapuis .470NE was regulated with Federal 500 gr but also shoots custom 500 gr TSX, solids and Hornedy DG with excellent accuracy — all were 500 gr…might be luck. I would think changing bullet weights could make a big difference or change of powder.?? I never really cared to experiment because I had 2-3 loads that worked well.

 

[zephyr]

Velo Dog Says"Double rifles are unique if not strange behaving contraptions."
Doing anything different with a Double can change POA POI...
I have shot dozens of Doubles for a good friend and gunsmith who sadly is no longer with us
Things that I have seen change a Double besides different loads..
New Recoil Pad, Shorten the LOP, Lengthen the LOP, Bending the Stock on a double, Anything new attached to the Barrels, Red Dots, Scopes, New Rear Sights,, Different People Shooting a Double
I was told many years ago If your Double shot inside a GrapeFruit you had a good gun If it shot inside an Orange your had a Great gun.
Velo Dog offers sage advise

 

[318AE]

Given I am now on my seventh DR and hand load for them all, I have found the following:
1. Regardless of powder and bullet type, match the bullet weight and FPS that the rifle was regulated with…you will be 95% there with good regulation.
2. DRs are finicky beauties…there are always exceptions but if you start at the above find out what your shots are doing…crossing at 50 yards?…slow down your FPS, too wide apart yet not crossing increase your FPS.
In all my rifles with my most recent 470 that I now have shooting under an inch at 50 yards with same bullet weight but different type bullet and powder used for regulation

Rare Breed’s experience matches my own, tinkering with loads for about five different doubles. Bullet weight and velocity go a long way in matching the recoil the rifle was regulated for, or the position the end of the barrels are in, when the bullet exits. I’ve read a lot about powders and pressure curves and bullet profiles that I just haven’t found as impactful.

No real way to tell what a new load will do until you try it, but start with the same bullet weight.

 

[uplander01]

A LOT. Lots of variables with a double, including ambient temperature depending on powder you ar eusing.

 

[Rubberhead]

Recoil starts happening the instant the powder is ignited yet it takes about 2/2500 ÷ 2, or 0.0004 seconds before the bullet leaves the barrel. (Obviously that's for a 2,500fps load and a 24" barrel and the second ÷ 2 is to average the velocity from ignition to leaving the barrel).

That recoil causes barrel rise (and cantilever in SxS guns) that affects downrange points of impact. Changing loads changes the time in the barrel and the amount of recoil in the barrels which in turn add component trajectories that change the points of impact.

 

[Rubberhead]

What I'm trying to get at is that a great, big strong man that leans into a gun will change the point of impact (even for a single barrelled gun) over a smaller person that purposefully lets the barrels jump to reduce their felt recoil. Like someone said, there are a lot of variables.

 

[KJE81]

When I changed the scope on mine I had to try like ten different powders until I found a load which regulated...some 200 shots later. It started to spread real bad due to the new scope (z8i 1-8x24) compared to the old Leupold (1,5-4x20), probably since the new one was 40 percent heavier.

Also I discovered that some double rifles, some will change their convergence if the time between the shots are more then 10 seconds. This fall I shot a moose with the first barrel and less then a minute later it got up again so I fired again with the second barrel but the point of impact was ten inches to the left. If shot within 10 seconds point of impact was 1-3 inches between when I checked at the shooting range afterwards between but as soon as it was longer then that between then it started to spread.

A swedish hunting magazine made a test on the matter and it would seem that it is quite common, at least with calibres around 8x57 JRS and 9,3x74R which was those in the test if memory serves.

 

[uplander01]

I honestly feel like there are probably really accurate doubles out there, particularly modern manufacture from names like Heym, WR, etc. That being said most vintage guns were concerned about 1 thing, being able to shoot twice and put them in a small pie plate kill zone at close range so you didn't die.

 

[zephyr]

uplander01 .... Perhaps the metallurgy has changed some .. Accuracy and the Regulation of Doubles whether New or Old are still regulated the same way

 

[uplander01]

Hmm ya I don’t know, I’m guessing barrel steel is better now than it was a 100 years ago, as well as rifling quality. I have a Manton 470 circa 1920’s, was refurbed by hh in 2008. Takes 3 shots from each barrel to fowl from a clean bore, then I can stack the next 20 rounds visibly separated l and r into group the size of a tennis ball at 50 yards, then they start to separate further apart——leads me to believe that bore quality and fowling affect a double as much or possibly even more than a single barrel.

 

[zephyr]

Gotta Gibbs 450NE made 1903 shoots better than I do

 

[HankBuck]

Gotta Gibbs 450NE made 1903 shoots better than I do

Don’t most rifles shoot better then we all do?