Point of Impact

[lightload]

The pertains to point of impact in my 45-70 Handi Rifle. I was shooting 13.5 grs Unique and a 350 grain plated Berry's bullet. At 30 yards the load printed 8 inches higher than factory 405 gr ammo. What the physics that makes this load print so much higher than factory 405 gr ammo.

[Shawlerbrook]

E=mv2

[dtknowles]

Or F=MA

just kidding, really does it seem like it kicks more than the factory ammo. It seems like your reload is very similar to factory power and velocity so it seems like at that short range it would have a similar point of impact. Contrary to common perception a lower velocity can raise the short range point of impact. This is due to barrel time, bullet is in the barrel longer so muzzle rise from recoil raises the point of impact.

[725]

My pure amateur guess would be "dwell time". If that load starts off slow (compared to whatever your other load is) the gun begins to move at the discharge (recoil). The longer it takes for the bullet to clear the muzzle, the higher the gun is pointed due to recoil. The bullet "dwells" in the length of the barrel and trundles out toward the target in the direction of wherever it's pointed at the time. A bullet that clears the gun quickly leaves the muzzle faster while it is still pointed closer to the target. That's my story and I'm sticking to it. :). Of course if the gun is resting on a forward support, the recoil can make the gun jump up, too.

[turtlezx]

725 got it figured out . wondered about this along time. ran into it with 410 slugs would print 15" lower the bird shot. which patterned dead on slugs were 500fps faster

[lightload]

Thank you 725. You nailed it.

[FergusonTO35]

I've never fired a factory round of .45-70 so I wouldn't have a clue!

[Sgt H]

I agree with 725 and will add that rifle weight also has a substantial effect. Lighter the rifle the more effect. I shoot several different loads in my 45-70's, 525 at 1300, 410 at 1350 and 340 at 1100. At 100 yards the 525 and 410 print on top of each other from the 11.5 pound Sharps, the 340's about 4 inches lower. Out of my lighter 1886 the 525 and 410 are a couple of inches apart, the 340's 8 inches. This is shot off cross sticks.