doublegunshop.com - home Forums General Discussion Double Rifles, Paradox Guns & Gauge Rifles @ doublegunshop.com Bullet weight/ point of impact with sxs ?

Is there any generality that can be applied to bullet weight and regulation with a sxs double rifle? For example, does a lighter bullet generally change your point of impact higher or lower, or is just a case by case thing?
Thanks
Rick

Bullet weight can have a profound effect on regulation as does velocity. In addition to elevation, bullet weight will effect grouping on the horizontal plane. A lighter than regulated bullet will cause the barrels to cross, while a heavier than regulated bullet will cause the barrels to shoot appart. Understanding this dynamic can help you as you develop a load for a rifle. If you don't know what bullet weight a rifle was regulated for, mark your target for each bullet, R1, L1, R2, L2, etc. A side by side rifle recoils to either side of its center line or to the right and to the left as well as up. If your rifle cross shoots, you can increase bullet weight. What's at work is the length of time the bullet is in the barrel (velocity) to be effected by recoil, and weight of the combined bullet and charge which effects the amount of recoil and thus the relative position of the barrels at the time the bullet leaves the barrel. Seyfried has written a lot about this effect including how it is possible to load a lower velocity, lighter bullet weight load that will theoretically regulate the same as the full power and weight loads.

I would suggest that while heavier bullets generally tend to cause the barrels to shoot further apart than lighter bullets, there are exceptions. For reasons I cannot explain, my German .250-3000 double rifle shoots the 87 grain bullets further apart than the 100 grain bullets and regulates at about a 1-1/2 inch spread at 100 yards with 115 grain bullets. No, the lighter bullets are not cross firing. I checked that.

As I said, I can't explain it, but that's the way this particular double rifle performs.