A Question for the Ballistics Gurus

[Werewolf]

To the MODS...
If this is in the wrong place feel free to move it. Kinda didn't fit in handloading or rifle country so...

I reload 45 LC. For the longest time my chosen load has been 200gr lead bullet out of a Win 94AE with 20" barrel. Muzzle velocity for the load is around 1200 FPS plus or minus 50 FPS.

I switched over to a more historically accurate 255 gr lead bullet. The load I'm using pops out the end of the barrel at 1050 FPS plus or minus 50 FPS.

I zero my Winchester at 50 yards and had a good zero with the 200gr bullets.

Now here's the question.
When I went to the heavier bullet and less velocity I fully expected to have to rezero my Winchester and I did. I expected that with a heavier, slower bullet I'd have to raise the rear sight to raise the point of impact.

Man was I wrong. The slower heavier bullets point of impact was a full 9" higher than the faster lighter bullet.

HUH?

What the heck is going on here?

 

[critter]

Happens a lot with handguns, heavy bullets and short ranges too. The heavier bullets recoil more, are slower to exit the barrel and therefore are launched at a greater angle above the original bore line (bore line before the hammer fell). In other words, there is more recoil before the bullet is able to exit the bore.

Hope that makes some sense. Have fun with those big ole bullets. They are surprisingly effective.

 

[Matt G]

Werewolf, I've found that to be the case with lighter rifles and handguns-- it's NOT the ballistics that are changing; it's that the muzzle is higher when the bullet leaves the barrel. You especially find this to be the case with light rifles (as your 20" 1894AE is) firing heavy bullets. It will begin to drop faster, of course, because its muzzle velocity is slower.

Every once in awhile, I come across a pair of different-weight bullet loads that strike to the same place at 100 yards without moving the sights. Cooper ruminated on this one time about an '06 that he was, I believe, comparing 150g loads and 180g loads in, and found them to strike the same place at 100. Obviously, things would have diverged pretty widely at 200 and so on, but what of it?

My "new" .243 gives me almost the same strike at 100 yards with a 100g at 3000+ as it does with 70g loads at 3400fps. It's a Featherweight M70, and that muzzle really rises with the heavier loads. How nice, though, to get to use the same sight setting for deer (100g) and varmints (70g)!!