Share your results with various POI shift solutions

[Crusher75060]

has anyone tried locktite on the threads of the shroud cap, and the shroud mount?

if I tighten the shroud cap too tight I think it compresses the baffles, and creates some tension that negatively impacts poi consistency. too loose and I think it slowly loosens up. locktite will maybe allow for a sweet spot in tightness.

I'm sure most of you notice when you turn that cap in either direction you instantly see a poi shift.

A little bit of the vibra-tite might work well for that application.
I have to say I have fought the POI shift several times while I've owned my 25 and I've solved it several times and went weeks without the shift. Then I'd pull the shroud for some reason and the POI is back. Recently I pulled the barrel to clean it and after assembly the POI is very pronounced. Like on minute I'm stacking the pellets, then suddenly I'm stacking them 3" to the left. I have been fighting that for a week now. None of my old tricks have been working. The thing I did differently is pull the barrel.

I just did the barrel alignment trick mentioned above and it made a huge difference. I still have the POI, but it is only 1/2" now. So I think tomorrow when it is bright and sunny, I'll do this again and see if I can get back to shooting the dimes at 50 yards again. I did notice that when I pulled the o-ring and looked inside the shroud, the stripper was NOT in the center of the barrel. After this new method of loosening and tightening the barrel screws, now the stripper looks to be pretty close to the middle without the o-ring.

As for the initial post for solving POI, for my gun I have found the two things that have helped the most in the past has been the gap at the breech and shroud and the other is tightening the breech block screws down a little at a time sort of like the bolts on the engine block heads. It seems if I tighten the back one, then the front two, I have issues. Or vise versa.
I'm wondering if we aren't hearing about the poi shift from the synthetic because it actually had 4 screws and it helps things line up a little better.

Just sayin' I was considering selling this woody and ordering a synthetic until I read this thread. I must admit I have been pretty frustrated by this particular problem.

Crusher

[bubba g]

has anyone tried locktite on the threads of the shroud cap, and the shroud mount?

if I tighten the shroud cap too tight I think it compresses the baffles, and creates some tension that negatively impacts poi consistency. too loose and I think it slowly loosens up. locktite will maybe allow for a sweet spot in tightness.

I'm sure most of you notice when you turn that cap in either direction you instantly see a poi shift.

A little bit of the vibra-tite might work well for that application.
I have to say I have fought the POI shift several times while I've owned my 25 and I've solved it several times and went weeks without the shift. Then I'd pull the shroud for some reason and the POI is back. Recently I pulled the barrel to clean it and after assembly the POI is very pronounced. Like on minute I'm stacking the pellets, then suddenly I'm stacking them 3" to the left. I have been fighting that for a week now. None of my old tricks have been working. The thing I did differently is pull the barrel.

I just did the barrel alignment trick mentioned above and it made a huge difference. I still have the POI, but it is only 1/2" now. So I think tomorrow when it is bright and sunny, I'll do this again and see if I can get back to shooting the dimes at 50 yards again. I did notice that when I pulled the o-ring and looked inside the shroud, the stripper was NOT in the center of the barrel. After this new method of loosening and tightening the barrel screws, now the stripper looks to be pretty close to the middle without the o-ring.

As for the initial post for solving POI, for my gun I have found the two things that have helped the most in the past has been the gap at the breech and shroud and the other is tightening the breech block screws down a little at a time sort of like the bolts on the engine block heads. It seems if I tighten the back one, then the front two, I have issues. Or vise versa.
I'm wondering if we aren't hearing about the poi shift from the synthetic because it actually had 4 screws and it helps things line up a little better.

Just sayin' I was considering selling this woody and ordering a synthetic until I read this thread. I must admit I have been pretty frustrated by this particular problem.

Crusher

could also be due to there being a spring holding the baffles in place in the new one making the tightness of the shroud cap less less critical...

I don't imagine the 4 receiver bolts making a difference. only because the barrel is connected to the receiver, so is the scope so everything would move togethe and the gun should still hit where you are aiming.

I notice that many of the higher end guns don't have floated barrels. they have barrel bands that hold the barrel in place. maybe the best way to get rid of the problem would be to have one made for the marauder. the only setback would be that you'd have to shorten the shroud which is going to increase the sound level of the gun...

[Crusher75060]

well..... adjusting things and trying to get the barrel more centered in the shroud, I forgot to tighten the screw that holds the rear shroud spacer against the breech block. First shot the shroud slid down the barrel (I didn't see it because I didn't take my eye away from the scope), second shot hits one of the baffles and explodes it. Cool.... arg.... I have a nick in the end cap too.... I'll be on the phone to crosman. Bummer.
I hate it when I make a bone head mistake like that.

So again, relating to the original post, this is what NOT to do while trying to solve the POI shift..

Crusher

[bubba g]

well..... adjusting things and trying to get the barrel more centered in the shroud, I forgot to tighten the screw that holds the rear shroud spacer against the breech block. First shot the shroud slid down the barrel (I didn't see it because I didn't take my eye away from the scope), second shot hits one of the baffles and explodes it. Cool.... arg.... I have a nick in the end cap too.... I'll be on the phone to crosman. Bummer.
I hate it when I make a bone head mistake like that.

So again, relating to the original post, this is what NOT to do while trying to solve the POI shift..

Crusher

that sucks.. I would have never thought of that happening... luckily crosman has been pretty quick about getting parts shipped out lately. I ordered 3 barrels, and some barrel o rings, and a derlin spacer to replace where the layer spring was. the o rings, and spacers were here 3 days later. the barrels arrived a couple weeks later...

[Crusher75060]

Can't order parts until Monday. This does apply to the POI shift solution.

Even though I clipped the end cap with my mishap, I think I fix my problem. Keep in mind I have one baffle which is now just a hollow tube (from the explosion) and a nick in the end cap.

I took a piece of plastic that according to my caliper is .04" or 1.05mm and cut 6 match-size slivers. I slipped them into the space between the barrel band and the shroud at evenly spaced positions around the barrel. That pretty much locked the barrel in the center of the band.

I aired up to 3000 and set up to shoot. The first clip, dead on. Second clip (where I usually get the drift) dead on. Third clip, at 30 yards I put them all inside a dime. Most of them were stacked with a couple of slight fliers that opened the pattern up to dime size. The first 6 were one ragged hole.

So... for MY gun, making a solid connect from shroud to barrel band works. Now all I have to do is replace the broken parts and find someone to make a spacer for me.


Crusher

[RayK]

There is a good thread over on GTA related to barrel harmonics causing POI shifts and/or scatter groups.

http://www.gatewaytoairguns.org/GTA/ind ... c=55801.20

I think these barrel weights rdsail is using may be of use on the stock 22 and 177 barrels.

It would be interesting to see if well-placed barrel weights could cure his issues with his original (stock) barrel.

Ray

[FuzzyGrub]

There is a good thread over on GTA related to barrel harmonics causing POI shifts and/or scatter groups.

http://www.gatewaytoairguns.org/GTA/ind ... c=55801.20

I think these barrel weights rdsail is using may be of use on the stock 22 and 177 barrels.

It would be interesting to see if well-placed barrel weights could cure his issues with his original (stock) barrel.

Ray

I saw that, and is interesting. I think I have some thin sheet lead from jig making, left. Was thinking you could do a test by wrapping that around the barrel at a couple of locations. or maybe find some shaft collars with 7/16" ID and small enough OD to fit in shroud. The standard OD for that ID, is 7/8", which is too large, but could test before having one custom machined.

[RayK]

I think I have some thin sheet lead from jig making, left. Was thinking you could do a test by wrapping that around the barrel at a couple of locations. or maybe find some shaft collars with 7/16" ID and small enough OD to fit in shroud. The standard OD for that ID, is 7/8", which is too large, but could test before having one custom machined.

Great idea, but it sounds like you need to keep it in place. His was shooting single hole, then it moved an inch or so and accuracy went bad. There is always duct tape

I don't want to block off the shroud. I like his front spacer that has breather holes, but is movable on the barrel. Something like that with a set screw might work well. But it sounds like lots of trial and error is necessary to decide where to place the weights for best accuracy.

Ray

[rupert3]

OK, here are two new ones that have worked for me after trying many of the other tricks with limited or temporary success:
1- On my 22 Marauder, I bought this, and slid it over my barrel. It worked so-so. I loctited it on my barrel an brought my groups way tighter.

http://www.ebay.com/itm/Carbon-Fiber-Tu ... v4exp=true

2- Center the barrel in the shroud! If you take off the oring on the shoud spacer, put the shroud back on and look down inside the shoud. You will probably see that the barrel is NOT centered in the shroud. This means that there is always side loading on the barrel. Thats why whenever you do ANYTHING with the shroud, you get a shift. So, this is what I did:
Remove the shroud.
Loosen the allen that holds the rear shroud spacer in place and push the spacer back square against the breech. Tighten the allen screw.This step is optional I think.
Install the shroud tight against the breach. Don't forget to put the oring back on the front barrel spacer if you removed it earlier.
Put the baffels, springs if you have a new version, and shroud cap.
Now, lossen the two allen screws that hold the barrel in place. The barrel should align itself inside the shroud. You might want to jiggle the shroud a little bit to help it settle.
Tighten the allen screws.
Put your scope back on.

My 22 now stacks polymags on top of each other at 25 yds and hasn't changed for a month.
My 25 now shoots sub dime sized groups with barracudas at 25 yds and hasn't changed in two weeks.

Just tossing my experiences into mix. I hope other have the same success with these.

Sundance Kid

For some reason I must be doing something wrong the measurements on the link provided does not match my measurements. Those shown on the link are less than 1/2 inch and I measure almost 1 " what am I doing or is it the wrong link.. Don't take this the wrong way now I may be doing something wring.
Bob

[SundanceKid]

It slips over the barrel of the .22. Makes the barrel more ridged and possibly reduces some of the harmonics of the barrel. It worked really good after I loctited it in place.

Using carbon fiber tubing is also talked about in the link above about using barrel weights.

SundanceKid