So far I've shot nothing but the 17gr A17 ammo through my Marlin XT17 w/ BSA Steet 17 scope. I've put 300 rounds of A17 through it and it's been spot on and more accurate than I am. Gun porn since everyone loves gun porn.
I've been very happy with the performance of the A17. Several months ago I picked up some CCI TNT Green 16 grain at $9/50 so I loaded up with about 500 rounds figuring I could use it for plinking. Hollow point not ballistic tip like the A17. I figured there might be a little PoI shift but not as drastic as I've been seeing. The day I went out to first try the TNT Green it I propped my rifle beside my gun safe and it fell over and hit pretty hard. At the range my scope way WAY off at 50 yards, by almost 2" left and high. I wasn't sure if I had bumped the scope good enough to throw it off. I spent about 20 rounds chasing the zero. With 1/4 MOA adjustments I figured I was over 2" at 50 yards off so 16 clicks to get me back to the middle and took another shot and I would be 2" way on the other side and even lower. I'm thinking the bump screwed up my scope so I packed it away.
Took it out last week to give it another shot. I was practicing the AQT for Appleseed so my target was set at 25m (~28 yards). I was barely on the paper with my first shot of TNT Green. About 10 shots got me close at the 25m about 1/4" low and left of my point of aim. I only had 5 more TNT Green left so I made a quick 5 shot group and it seemed to be grouping well. Took out some 17gr A17 and shot a 5 shot group. At 25M it's a good 1" off while the TNT Green was only 1/4" off so a difference of about 3/4"
Not just in elevation but in windage as well. That seems like a pretty drastic PoI shift at only 25M. 3/4" at 100 yards with different ammo? That I could have expected. But 25M? Matches up to what I saw the previous range session of ~2" off at 50 yards
Bottom group was the 16gr TNT Green. Dot directly above that was the point of aim for the 17gr CCI A17. With the bull barrel and the relativly light 17hrm load I wouldn't have expected that big of a PoI shift. Anyone ever seen this type of behavior?