Changing POI/Marauder

Changing POI/Marauder

Joined: June 21st, 2012, 7:20 pm

July 13th, 2012, 4:12 pm #1

My .22 Mrod is changing POI despite fantastic accuracy using 18.1 JSB. At 35 yards it will deliver match head accuracy..dead on.. and then suddenly with the next shot move about 1/2 inch right. Always to right of my standard sight in. If I stop at that point and refill it will move back to left again for a number of shots. It must be related to the fill in some way, but is there a way to solve the problem? Would glass bedding the rear most portion of the tube and free floating the forward portion tend to resolve these issues?
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Joined: August 20th, 2008, 3:27 pm

July 13th, 2012, 6:34 pm #2

Sounds like something is loose, I'd check the shroud first then make sure the barrel band isn't touching the shroud anywhere. Also the breech block it could be loose on the receiver tube.
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Joined: June 21st, 2012, 7:20 pm

July 14th, 2012, 10:08 pm #3

Thanks for the reply. Just got back in town. Will check for any loose parts etc. that would be a welcome and hopefully easy fix.
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Joined: June 21st, 2012, 7:20 pm

July 14th, 2012, 10:55 pm #4

Sounds like something is loose, I'd check the shroud first then make sure the barrel band isn't touching the shroud anywhere. Also the breech block it could be loose on the receiver tube.
Did a quick check and could not find loose parts.
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Joined: August 20th, 2008, 3:27 pm

July 15th, 2012, 7:46 pm #5

<p>I can only think of two other reasons, one the tune isn't setup for 18.1s. Put it over the chrony and see what your fps looks like at full charge and then when it starts to move POI. Also check for pellets clipping baffles or end cap. 18.1s tend to like a speed of 880-900.</p>
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Joined: June 21st, 2012, 7:20 pm

July 15th, 2012, 11:17 pm #6

I think your right about 18.1/900fps. My AA500 shoots extremely well at just over 900fps. I've been considering increasing fpe/tune on the Mrod so that I wouldn't have to deal with two different trajectories. It would be nice to see the problem disappear at about 900fps. Thanks for the suggestion. Now I need a tune that will accomplish that.
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Joined: June 21st, 2012, 7:20 pm

July 16th, 2012, 10:36 pm #7

<p>I can only think of two other reasons, one the tune isn't setup for 18.1s. Put it over the chrony and see what your fps looks like at full charge and then when it starts to move POI. Also check for pellets clipping baffles or end cap. 18.1s tend to like a speed of 880-900.</p>
resulted in such poor performance that I was truly thankful to get back to the tune that I started out with- JSB 18.1 at 800 fps.Back to shooting at (and hitting) pellet holes at 35 yards. I am pleased with the accuracy but I fear that at some point the POI will again move to the right...It hasn't been the kind of constant switching back and forth that tends to make accuracy poor as five even ten shot groups are typically covered by an advil. I have only shot about 20 shots after returning to original tune but so far no POI change. During the tune process velocities around 900fps produced poor accuracy even when shot strings had very low SD. Apparently this gun likes the JSB 18.1 at the 800fps level. I am beginning to wonder if the scope, a Swift 6-18x50AO which has been reliable in the past might have a little problem.
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Joined: August 20th, 2008, 3:27 pm

July 18th, 2012, 4:18 pm #8

<p>Your accuracy sound good, maybe it's just a few pellets that are out of size or have dented skirts? Usually the heavier pellets require a minimum fps to group and if your is grouping at 800 that's good but is on the slightly slower side, probably because your shooting at a medium range. Maybe try some 15.9s and or sort your pellets. Also if the optic is wacked you'll be chasing your tail till its replaced with a none good one.</p>
Last edited by REARSPROCKET on July 18th, 2012, 4:21 pm, edited 1 time in total.
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Joined: December 5th, 2010, 1:09 am

July 20th, 2012, 5:48 pm #9

My .22 Mrod is changing POI despite fantastic accuracy using 18.1 JSB. At 35 yards it will deliver match head accuracy..dead on.. and then suddenly with the next shot move about 1/2 inch right. Always to right of my standard sight in. If I stop at that point and refill it will move back to left again for a number of shots. It must be related to the fill in some way, but is there a way to solve the problem? Would glass bedding the rear most portion of the tube and free floating the forward portion tend to resolve these issues?
You may want to check and make sure the shroud is not overly tightened. By allowing a slight gap (about half turn counterclockwise from full clockwise), my poi problem has been solved. Give it a try.
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Joined: June 21st, 2012, 7:20 pm

July 20th, 2012, 9:08 pm #10

is tight, but will it remain in place if backed off? This is a possible solution I'll try it. Thanks
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