22wmr cci question

[dazed]

Last month I decided to put a new scope on my Marlin XT-22M (22 mag bolt action) rifle. Just a inexpensive Simmons 3x9-30 scope, so the 22 mag can reach out and tag some prairie dogs at 100 yards. This past Friday I fanally had a chance to go sight it in.

After the initial sight in I decided to test a few different ammo types and see what the gun liked.

First was CCI Maxi Mag TMJ 40gr @ 1875 fps.
These shot great and fine tuned the scope for them, shot nice tight groups on bullseye.

Sencond was CCI Maxi Mag CPHP 40gr @ 1875 fps.
These shot great also, 1 click to the left and 1 click up, shot nice tight groups on bullseye. ( 1 click is 1/4" at 100 yards )

Third was CCI Maxi Mag +P CPHP 30gr @ 2200 fps. Here is the the issue, shot nice tight groups 2 inches bellow bullseye.

Question isn't exactly A CCI specific one but. Why would a lighter faster bullet shoot 2" below where the gun was sighted in?


Thanks for any information or where to look. I did look up the ballistics on CCI website, not what i was looking for exactly.


Dazed

 

[rcmodel]

Because they don't recoil as much as heavier bullets.
And they are a lot faster getting out of the barrel.

So the gun doesn't recoil upward as much while the bullet is still in the barrel.


It can also just be a barrel harmonics thing as the barrel vibrates differently with different loads.

rc

 

[ATCDoktor]

A combination of flatter trajectory and recoil is what is causing your POI differences between your 40 grain bullet and your 30 grain. (believe it or not that slower 40 grain bullet stays in the barrel longer and giving recoil more time to act on its flight characteristics).

ETA rcmodel beat me to it.

 

[dazed]

Thanks for the responses. Not my first guess that is for sure. No clue why I just assumed a lighter faster bullet would have shot 2" high and not 2" low.

Learn something new everyday.

Guess this just means I need to go back to the range with more ammo. Could be worse I guess.

 

[PapaG]

The 45 or 50 grain WW defense rounds shot three inches higher for me out of my 77-22mag. 32s were low, maybe three inches.
Handguns show even more of a dramatic difference on elevation due to bullet weight.

 

[MedWheeler]

Yep. Should have seen how surprised I was in LE training when I shot thousands of rounds of 158-grain standard-vel .38 stuff, then switched to agency-issued 95-grain +P stuff for the first practice qualifier. If I had waited until the "real money" qualifier like we were supposed to, I barely would have passed. All my clusters were generally centered 8-10 inches lower after the switch. At least I knew to compensate in aim the next courses of fire (didn't have time to adjust sights.)