If you have reloaded for quite a while you have seen some strange things at the range. For the newbies and those without a chrony be prepared for some head scratching data that will defy logic at times when you do get a chrony.
Today I was working some new loads with Barnes 168 TSX's in a 300 SAUM.
56.5 gr Varget got a 3/4" group that was 3/8 rt and 1/2 high from point of aim. 2988 av FPS

64.0 gr H 4350 got a 3/4" group and 1/2" above pt of aim. 3029 Av FPS

63.5 gr 760 got a 1/2" group and 3/4 rt of aim point and on elevation. 3135 Av FPS I thought the extra speed on this one would have a higher trajectory but not so.

64.0 gr 760 got 1 1/4" group, 1 1/4" rt and 1/2" higher than pt of aim. 3144 av fps This one is no good for sure.

All was pretty well til the next group. I had some 180 TSX's that I had loaded a few months back and was curious to see how much lower they would shoot since I knew they were slower.

62.5 gr H4350 got .340 group, 3/8" rt and 1/2" high to pt of impact and 2893 AV fps.
First thought is to stop playing with the 168's but the darned confusing thing is the heavier bullet at over 200 fps slower and with a higher trajectory than a lighter faster bullet of the same brand.

It has to be exiting at the perfect time for harmonics I guess.

So for speed freaks, speed aint everything boys.
NO scope adjustments were made during the round. I am going to try a couple lighter loads on the 760 to see if I find a speed that laughes the bullet at a higher trajectory.

Sometimes life is simpler when you are just fat dumb and happy without so much data to screw with your brain.

Longer bullet, rides in the air better

My take on that would be that the rifle is in recoil by the time the bullet leaves the muzzle...hence the muzzle is higher with the greater recoil of the heavier bullet. The actual differences in trajectory of the different loads would be very slight indeed, if they were fired from a 'welded in place' test barrel.

It's even more noticeable with handguns.

quote:

Originally posted by Tumbleweed:
My take on that would be that the rifle is in recoil by the time the bullet leaves the muzzle...hence the muzzle is higher with the greater recoil of the heavier bullet. The actual differences in trajectory of the different loads would be very slight indeed, if they were fired from a 'welded in place' test barrel.

It's even more noticeable with handguns.

Now that is an interesting thought about the recoil and muzzle rise as the bullet leaves. If that were truly the case I would wonder how that group could have been so tight.

Just looking at the results of the 4 loads with the 168's is still puzzling. I am going to load up some more tonight and run the test again tomorrow and see what happens. I am assuming harmonics is sending the faster loads of the 760 off to the right. I will load those down a little cooler to about the same speed as the 4350 load and see if they center up better. The 4350 in both bullet wieghts is close to the center of the target.

My 7mm08 has very little recoil and there is always a noticable difference in elevation when speed changes.
It is a head scratcher for sure.

It is exaggerated in a handgun, but is almost a law that a slower heavier bullet will strike higher on the target. This is due to muzzle flip, read that increased recoil from the heavier bullet. It has nothing to do with accuracy. It has been said that a rifle barrel vibrates like a guitar string when it's fired, so some of the change in impact is due to the bullet's exit point rather than velocity. Some will shoot higher when faster, some rifles will not. There is just no set rule. I have a .375 that needs 2 grains more RL15 to get a Hornady 270 grain bullet to the same speed as a 270 North Fork. I can load them both to 2770 fps and the impact is 3.5 inches apart at 100 yards. This is with the same powder same weight bullet at the same velocity. Yours are actually quite close to the same point of aim.

guys, it's not recoil directly, it's the time the bullet spends inside the barrel. The slower it is the longer the time in the barrel, thus the muzzle is higher so the bullet prints higher on the target. All loads with light or heavy bullets have recoil starting just about as soon as you pull the trigger. A faster bullet is going to get out of the barrel sooner before it has time to rise as much as a slower heavier bullet.

Mr Payne has this correct.

A longer, higher sectional density bullet will retain energy longer and not drop as much as a lighter shorter bullet even if the light shorter starts at higher velosity

The longer and heavier bullet does not always give the flattest trajectory. If the lighter bullet has the same BC as the longer bullet and both are zeroed at 200 or more, it will shoot flatter by virtue of higher speed. Given that there is no change in scope settings between firing the two bullets, the longer heavier bullet will strike higher than the other at 100m, for the reasons that Tumbleweed, MaxPayne and Pointblank correctly state.

maxpayne

You are correct is is barrel time, the recoil is an indirect force. If there were no recoil of course barrel time would mean nothing. In practice, you just have to settle on a particular load that works and hunt with it. I very seldom have any rifle that I hunt with more than two loads, actually most only one. The .375 is an exception, as I shoot 270's and 300's both.

Once I settle on my hunting load that never changes and the scope doesn't either. I like shooting lighter bullets and light loads for trigger time and keeping the zero near my hunting zero.
Barrel harmonics is the real issue and I was just playing around with different components and got amazed at what I saw in speed difference on 760 and not much POI change.
I will not use it again and I tried the test again today with a lighter load of 760 and they go off to the right as yesterday. The loads with H 4350 were holding center very well so that is the powder of choice for this one. This fluted barrel on the Sendero sures acts different from my non fluted varmint barrel on the 7mm08. On the non fluted barrel nothing goes off to the left or right and faster bullets always shoot higher than slower ones and on line. Makes no diff whether it is 100 gr or 160, it shoots them all perfect with 4895, Varget and 4350. I just hope I can get someone to dublicate the barrel someday if I ever wear it out. That one also goes 3 gr over max before showing any kind of pressure sign. I don't shoot it that hot anymore just to try and make it last longer.
On the 300SAUM that I started the discussion I got 1/2" groups on all the H4350 loads today. The 168 and 180's shot the same elevation.
I will have to try it 200 yds next to see what happens there.
Thanks to those that commented.