What could be the reason of my air rifle's POI vertical drift?

[ShootAndHunt]

Several days ago I went to the range with my new scoped air rifle Crosman RM622 (of course I brought other rifles, but I want to sight in this one). In the indoor 25 yds. range, this rifle nearly drove me crazy. It sprayed the pellet all over the target (within approximately a 6 inch circle @ 25 yds.). Then I remembered that some guys said you could not hold the air rifle as tight against your shoulder as a firearm. I followed the suggestion and the group is shrinked, but I found a very fun thing. The point of impact (POI) is shifting almost vertically downward shot by shot (they are almost on the same vertical reference line of my sight-in target). Then, when I think this trend will continue, it jumped to some place upward and sideward. and then back to almost the original point and the same downward drift sequence again.

I am not sure what could cause this problem, I never have the same experience with my firearms. I don't think it is caused by the rifle (but not so sure, I said this because occasionlly it will shoot two pellet into almost the same hole). The scope and ring on this air rifle came as the standard equipment with it, and they might not be very high quality (I am talking about Crosman), but I don't know whether it is caused by the scope or the ring. Anyone has some suggestion of the reason of this problem?

 

[SDC]

My first thought is that either your mounts arent mounted securely to the rifle, or your scope is slipping in the mounts; if it's not that, then I'd suspect that something inside the scope is shifting around. Spring-piston air rifles are notorious for beating the hell out of scopes because they have a "whiplash" recoil, unlike other firearms (you get a rear-ward recoil when the piston jumps forward, but that motion is reversed when the piston comes to the end of its travel). HTH.

 

[DougCxx]

--If the airgun is new, then it may take two or three hundred shots to settle in and start shooting consistently. You are correct in that spring-piston guns should be held loosely.
--Also the stock screws may be coming loose, they should be checked every few hundred shots until you can be pretty sure that they aren't backing out on their own.
--Other than that, try checking all the scope screws, using the iron sights, or another scope....
~

 

[P95Carry]

I'd lay odds you have sight problems. Something is changing incremenatlly, shot buy shot ... each time the jarring has its effect.

It is hard IMO to keep scopes per se really set on an air weapon, tho the supposedly ''purpose'' made slim BSA types do seem to survive.

I have just put a cheapie red dot on my air rifle .. and am hoping its low mass will allow it to hold settings but the rifle has quite a ''kick'' .... in spring terms! We shall see.

 

[redneck]

Is that one of the rifles manufactured for crosman by that spanish company (Mendoza?) I went through two of them before I got my Gamo.
The triggers on both I tried were probably about 15lbs, literally made my finger sore after about 100 rounds. They also dieseled on every shot which is the main reason I exchanged the first for the second and the second for a Gamo 220
If thats it, I'd say that the trigger isn't doing you any accuracy favors, but I don't know how to fix it.
If the trigger feels good to you, then I'd check the scope mount to see if its walking. Those rifles had a pretty short stiff kick to them. With a dovetail mount it would be pretty easy for the scope to walk backwards, my gamo uses a dovetail mount but has a steel stop block that mounts behind the rear scope mount and has an extra set screw agains the top of the receiver to keep it from walking backwards.

Also, next time you shoot, fold the barrel down and blow through it. If you get a puff of white smoke or smell something hot, thats probably the culprit. The rifles I had both did it very consistently. The oil in the piston ignites. Some say that the Mendoze guns do that and its not a problem, but I didn't like it. Too many other folks said the gun would eventually destroy itself (I guess its hard on the seal, and causes the spring to kink). Bottom line, the times it diesels the pellet comes out alot faster. So if your gun is doing it intermittently it will make your POI change, and most likely just vertical stringing. I'd check every round for smoke for awhile and see what happens.

Hope you get it worked out. Those rifles are nice. I really liked the sites and stocks on the ones I had. Just couldn't get one that worked right and got tired of returning to the store.

 

[JohnKSa]

Typical hold sensitivity problem with a springer airgun.

Put a small piece of tape on the forearm so you can put your hand in exactly the same spot for each shot.

Don't grip the forearm, just let it rest on the palm of your hand.

Try to be consistent with your trigger hand position, and be careful about trying to squeeze the stock or point the gun using the trigger hand.

Don't press your cheek down hard onto the stock, let your cheek rest lightly on the stock.

 

[ShootAndHunt]

Thanks guys. I will try your suggestions and report the result after my next trip to range. (It is still somewhat cold and chilly here, especially at the outdoor range.)

 

[Watch-Six]

In my experience spring cocked air rifles are very rough on scopes and mounts. I had a tough time keeping them on two different air rifles. The mounts tend to walk off the BACK of the grooved receiver. Also, parallax is a big deal at the close ranges you will use an air rifle at. The scope pretty much has to have an AO or you will have trouble. Just my experience. Watch-Six

 

[JohnKSa]

Could be the scope, but I'd be surprised with that kind of problem as the symptom. Usually when a springer kills a scope, the shots go all over the place.