Tuning Why when I shoot my Marauder my groups wander

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bearbar

bearbar

Member
Aug 19, 2021
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PA, Lebanon United States
I am using a Marauder 22 cal stock rifle Walther barrel Pic scope rail on top

When I am testing I will shoot 5 shot groups the group size at 25 yards is good ( around 3/8" outside to outside) with the 18 gr JSB pellets

I will shoot 5 groups and then refill

What happens is as I am shooting the groups the groups wander around the aim point 

Example one group might be at 2 o'clock then one at 6 o'clock and another at 10 o'clock they are not far away from the aim point but I can't figure out why they wander

Right now the pellets are 825 FPS with a spread of about 10 FPS 

I am shooting off of a 1 piece rest with a 3" wide block mounted on an Anschutz rail on the forend. Rifle is scoped with a Bushnell Match Pro scope
 
OK, here it is. I'm no expert and did not want to be eviscerated if I'm not correct or mispoke on some terminology.



BearBar



I have this same EXACT problem with the following at 18 yards. Bench rested 

Marauder Gen 2, .177, regulated with LW barrel and SWFA scope

Daystate Huntsman Regal in .177 with Aztec SFP scope

Daystate Redwolf Normal Power in .177 with Aztec FFP scope.

Decent guns and decent scopes…..

I fill up the magazines and shoot 60 shots. Take 5 shot groups at different targets on the same paper. The grouping size remains the same, but the POI varies slightly and this irritated me. No apparent rhyme or reason. The movement necessary to sight in at a target 1cm away did not seem enough to whack off the gun's accuracy.

1st, check your parallax on your scope. Take your time and do this if you have not already. This helped a lot, but did not totally solve. Also deal with the eyepiece focus.

With the parallax adjusted, now do your very best to align your eye, face, cheek to the scope/target. I know this sounds obvious, but if you move your head, the parallax can move. Adjust the eyepiece if necessary so everything is aligned and doesn't float around. Try to keep this same position every time you shoot



I've not totally solved this problem but I have reduced it significantly. So I think it is eye/scope/reticle/target alignment. 

GOOD LUCK and let me know how things work out!
 
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My friend are a expert in not hitting things with the same scope/rifle i just drill holes with.

Okay ! some times i am also a bit too fast on the trigger, this normally happen after a few 100 shots and i get what i call gun fatigue. Meaning it is time to do some of the dreaded physical work my friend / range master always have plenty off, then kickback for a while ( maybe a little single malt on ice ) and then approach the gun again.

It could also just be your setup is not quite at the sweet spot, i know if i shot lighter JSB pellets in my Cyclone, the 2 slower speeds would give me okay groupings but at the higher speed the pellets was erratic up / down / L / R of my point of aim.

So the question is ? do you get the same with any pellets you shoot / have you tried alternatives. some pellets my Cyclone shot really bad with, the best was by far the JSB heavy ones.
 
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As I said I am shooting off of a 1 piece rest with a return to battery once the scope is sighted in on the aim point i do not need to adjust the poi I am also firing the trigger with a camera release button so I am not touching the rifle at all.

I have several bench rest rifles that I fire free recoil and get fantastic results shooting this way. Maybe this does not work with a PCP

I check my parallax and have that adjusted properly 

I noticed that the barrel floats in the barrel band would it help to make a spacer to not let that float
 
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Some scopes are very forgiving regarding eye position. You can move your head around and still see straight down the tube with no change to the sight picture. Others, more often than not - cheaper, are not forgiving at all. The slightest head movement and half the sight picture blacks out.

The latter type of scope really helps reduce POI shift due to shooter position.


 
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I am not unfamiliar with head position, I shoot bench rest and have shot very small groups.

The scope is a fairly good scope it is a Bushnell Match Pro

Scope is properly mounted

I just thought it could be something maybe in the bedding of the rifle 

I am shooting on a 1 piece rest so moving from 1 target to the next should not effect the POI, I am even using a camera release to fire the gun , I am not touching the gun, only time I touch the rifle is to cock the bolt and put in a new pellet and those I am single feeding. I can't figure this out, I even went as far as to weigh the pellets and separate them by the .02 of a grain. 

What gets me is that it shoots nice 5 shot groups until I move the poi to another target and that is only 2 1/2" apart.

The rest is an Ahrens 1 piece rest that I have shot very small groups with with a 6 PPC bench rest rifle with the same method.
 
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As I said I am shooting off of a 1 piece rest with a return to battery once the scope is sighted in on the aim point i do not need to adjust the poi I am also firing the trigger with a camera release button so I am not touching the rifle at all.

I have several bench rest rifles that I fire free recoil and get fantastic results shooting this way. Maybe this does not work with a PCP

I check my parallax and have that adjusted properly 

I noticed that the barrel floats in the barrel band would it help to make a spacer to not let that float
Click to expand...

many of Us Marauder owners put O-rings in between the barrel shroud and the barrel band, using a tooth pick to shove the O-ring in, this works great to keep the barrel from moving.
 
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enigmatic! seems like you have just about every control element nailed.

What happens if you dont move the Marauder for all 25 shots? Will the POI shift from 2, 6 and 10 o'clock if you just stop after 5 shots, then resume (without moving) ? If not, then it has to do with movement of the gun/scope/aim. Perhaps you can come up with a clever way to insert a new target over the old one in the exact same position (so a fresh group on paper) after each 5 shot group without using the scope to align.

Good luck. This is interesting
 
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