Can someone explain this?

[Cal]

So I'm doing a pellet test to find the optimal hunting pellet for my marauder pistol. The strings are pellet by pellet, one mag ( 8 shots) per aimpoint vertically. Here you see RWS Super Hollowpoints to the left (disregard first group at top) and Air Arms Field Diabolo to the right. The RWS are grouping beautifully and I'd really like to make them my go to, but as you can see, the groups, even though they are tight, drift gradually to the left of my aim point. Of the seven pellets I tested, these are the only ones that do this. Shouldn't be scope-related as pellets tested just after this didn't exhibit any drift. Each pellet is tested from a fill of 2700 psi ending after 4 mags. Would love to get this figured out as no other pellet is this accurate in my gun. On a side note for those of you who have P rods.. I'm finding mine not to be as pellet fussy as is often pointed out. It shoots several pellets well including polymags, crow magnum, JSB RS among others. Doesn't, however like Crosman premier Hollowpoints or Crosman Accupels.. Strange. Thanks so much for any help you can offer!

 

[MattChastain]

I don't really see a problem as long as they are grouping. Just adjust your zero and call it good. That is some nice accuracy from a pistol. 

 

[Gritz]

Is this a brand new gun? Maybe the barrel needs a break in? If the barrel is tight and still getting pores of the rifling filled maybe the rounds are gripping tighter and tighter. I don't know if this is the case but after you double check all your screws and shoot a few tins of pellets through with regular cleanings maybe it will settle in a bit. Otherwise you might want to go back to different pellets to make sure that your scope cross hairs aren't drifting on you. Please keep posting if you find something out. I have had issues in the past that I never figured out but seemed to just go away after a while.

 

[Cal]

Thanks guys.. Will check mounts and clean barrel and see where it leads. Otherwise maybe zero a little left and keep track of mag count for small compensation. 

 

[fr8rbum747]

I believe that your slight drift may be due to you canting the Pistol slightly as the shot string progresses. I have seen this before and it takes very little cant of the rifle / pistol to throw off your nice grouping of the RWS pellets. I had this happen quite a bit when I was shooting my modified Crosman 2240 with HPA. The little pistol became a really short carbine with a BNM breach, 18 inch barrel and moderator. The scope rings were a bit high to clear the magazine and therefore it was easy to slightly lay the gun over when trying to make the cheek weld on the stock. Just a thought since the Marauder pistol is very similar to the set up I just described.

 

[Prouzy]

I agree with canting. Its possible when ammo does not group well, this effect is less proounced/detectable. You may notice when you shoot a rifle, your entire torso moves with the rifle as a single unit, however most will move arms in pistol shooting to accomodate for position change in target. If youve ruled out equipment error, using scope level can help with this. Over time, your body position and horizontal gaze can establish position memory. Another option to accerelate could be using tagets with crosshairs bulls, being sure the are set level to match up with scope crosshairs. This can also help to determine error between shooter and equipment. 

 

[Cal]

Thank you fr8bum747 and Prouzy!.. I think canting is a definite possibility ! I'm going to look into it.. Check with a level and the crosshaired bulls are a good idea!