Double Rifle Divergence/ Convergence

[Schroeder]

Hi,
As I understand it, when developing a load that regulates well in a double rifle, as you increase velocity the divergence is reduced. In other words the point of impact of each barrel is brought together.
And conversely as velocity is reduced, divergence is increased.
Is this set in stone?

Has anyone ever experienced the opposite to this rule?
Can a velocity increase cause more divergence, or make the bullet impact from each barrel spread apart?
Curious as to other people’s experience…
Allan

 

[uplander01]

It can go both ways in the extremes, which you never want to be at the extremes with double, start low and work up. Not sure the double your working with but if traditional style there are many of us on here that can help through the process. More details to start would help.

 

[Schroeder]

Thanks uplander01, I am pleased to hear that it can go both ways.
I only ask the question because I noticed something yesterday that I had not seen before in either of my doubles previously.
I was shooting my Merkel 961L in 9.3x74R.
I have developed a load with Woodleigh 320 grain RNSP that shoots very well, and consistently. Around 3/4” of an inch at 100m without crossing.
However yesterday I started shooting a lighter 286 grain bullet, not for any other reason than I just enjoy load development for doubles. It’s a fascinating process that I get a lot of pleasure from.
Anyway, I fired two groups (4 shots) that crossed by six inches. I then increased the charge by one grain and to my surprise the spread reduced by half, to three inch’s. I then fired two more groups and exactly the same thing happened.
I will test more in the future with more powder again, and see if I can get them not to cross.

I was just curious to others experiences with this happening?

 

[Rare Breed]

Hi,
As I understand it, when developing a load that regulates well in a double rifle, as you increase velocity the divergence is reduced. In other words the point of impact of each barrel is brought together.
And conversely as velocity is reduced, divergence is increased.
Is this set in stone?

Has anyone ever experienced the opposite to this rule?
Can a velocity increase cause more divergence, or make the bullet impact from each barrel spread apart?
Curious as to other people’s experience…
Allan

While you are generally correct in your statement be careful with the barrels “crossing “ meaning the right barrel point of impact being left of the barrel and vice a versa. Having owned many DRs all hand loaded the best thing to do is start with a load you think will regulate well and load one grain more up to three grains more and one grain less up to three grains less all from your starting load. I load four shells for each one. Now at 50 yards shoot each barrel always stopping to mark on your target R1, L1 etc for each shot. With the above I found my favorite DR was crossing at the start at 86 grains of my powder. At 84 grains no more crossing and now I get 0.6 inch point of impact for both barrels. Nothing beats the above method to know exactly what your gun does. My elephant I took this year showed my first two shots within one inch at 50 yards which was gratifying to have my DR perform in the field. hope this helps