POI of heavy and light pellets

[raterminator]

Finally I finished my new pellet trap and did some tests at 15 yards with pellets I got at hand. Here are shot results from Barracuda Match 10.6gr, Beeman Kodiak 10.6gr, Crosman Premier 10.5gr and lighter pellets (7.9gr) from Crosman (Copperhead Wadcutter, Pointed, Super Match) and Gamo Magnum 8.5gr.
Now, there is something I don’t understand and hope that somebody can enlighten me.
My understanding is that if the POI of heavy pellets is correct, then lighter pellets should land higher (because of their weight). As you can see on the targets, the exact opposite happened. First, I thought that scope’s zero changed, so I did a quick test with heavy pellets again. Everything was right. Any ideas?

my guess is that the distance to the target was small enough that the heavier rounds had plenty of power to match the trajectory of the lighter ones and they're simply more accurate pellets than the lighter ones.

You're not just missing low on your lower gr rounds, you're also missing left and a good number of them are not low at all, but only missing left.

Try shooting at 35 yards and see what happens.

My hunch is that if you dial in on the heavier pellets then switch, you will then see some of the POI discrepancy but you'll probably still be missing left as well, which means that the heavier rounds are simply more accurate.

The precision on the lower weights is actually very good, it's just not where you were aiming. If I hadn't seen the first shots I would have suggested adjusting your scope...and you might want to check to make sure that nothing came loose after those heavier rounds were shot.

Raterminator:

Did you shoot these with a spring-piston rifle?

-JP

[raterminator]

Yes. Indoor, with Gamo Hunter 440, .177 cal.

[raterminator]

The distance was my first thought too, Larry. Sure, at 35 yards, picture will be dramatically changed and I have to play with dials again. But I’m the city guy, and mostly I can afford only ~20 yard basement shooting and sometime rat shooting in our backyard. To see full capability of the gun, I need to find a place to put it to the test. I’ll see what I can do about that. Thanks

[Bill inTX]

Check out "Demo 15" of this link. It's an animation of the "heavy pellet hits higher" phenomena. Has something to do with "recoil dynamics".

http://www.arld1.com/

[waunderin]

barrel harmonics, time pellet is in the barrel, barrel ossilation, lots of little things that add up. waunderin

what doesn't seem to makes sense is that roughly half of those lower gr pellet shots would have been in the bullseye
if they weren't left of target.

In other words, roughly 50% of the time the drop wasn't the reason the pellet wasn't hitting the target.

Unless barrel harmonics provides (I don't think it does, but perhaps I missed that part)  a left-directed force on the lower weight pellets but not the heavier, there is something else going on.

I agree that you may have to try some long range shooting to see the effect.  I just ran a sampler of 36 different pellets through a new R9 that was zeroed  with mid weight pellets.  All the light pellets shot high and the heavyweights shop low.  As much as 4 inches either way.