[LeoCal]

Yesterday I took my #1 45-70 to the range to see how a 310 WFNGC @ 1500 fps would impact at 100 yards compared to a 405 WFNGC @ 1750 FPS (my "standard" load).
I was expecting the lighter, slower bullet to strike lower, but much to my surprise it struck 10-12" higher!
Could this be some kind of recoil effect?

Puzzled.

 

[IDShooter]

LeoCal,
    My guess would be that the lower velocity of the load is the culprit; the bullet is in the barrel longer as recoil causes the muzzle to rise.
      Having said that, I find that lighter bullets at higher velocity often strike higher too, but here I'm talking about spitzer bullets in fairly smallbore centerfires. In this case I believe the high point of impact is simply due to reduced drop of the projectile.
     Barrel mechanics as the shot is fired and the physical affect of gravity and air resistance once a projectile is airborn make predicting the point of impact of different loads a pretty risky business!
     This all reminds me, MikeG asked about the impact points of different .257 loads. I'll have to put that in a new thread!           IDShooter

 

[MikeG]

Yeah I was just thinking of my .257 and points of impact!

Most of my guns put heavier, slower bullets at a higher point of impact.  One exception is with my .30-06, it reverses the trend when bullets are lighter than 150 grains and starts sending the light ones on a higher trajectory again.

My .257 is an odd duck.  It will shoot two different brands of 100 grain bullets to the same elevation... and about 4 inches apart with respect to windage!  Same charge of the same powder, same seating depth, etc.  With that gun, I have to keep track of which load I'm sighted in for.  The .30-06 throws most bullets in a straight line for windage, just the elevation differs.

My .22-250 has a heavy barrel and nearly everything has about the same point of impact at 100 yards.

Guess the moral is... you never know till you shoot 'em.

 

[RugerNo3]

LeoCal, fwiw, I have a 1975 series #3 Ruger 45-70 and use a 300gr 459pb at 1550, a 300gr Rem HP running 2050, and a 300gr Rem HP running 2450 that will mix and  into a 1-1.25in group all day. The Rem HP loads will group less the .5" anytime I wish. A Winchester 300gr factory load will also run to the same point of impact. It still has the barrel band and a .030" shim between the barrel and forearm. It makes a whale of a varmint rifle with appropriate backstops. Whitetails are also easily dropped.
I believe your results are related to position on bench with the forearm. I rest mine close to the action and sling tightened.