Frustrated with my .22 cal Marauder

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"I tried loading pellets with and without the magazine by pushing the end of the bolt as you described. If it helped the accuracy issues on my rifle, the difference was very minimal. However, I did try reducing the front-to-back free play of the magazines within the receiver and that "SPC, Thanks for the reply.

I agree that you can get better groups by using the single shot tray. I have also tried loading a pellet by pushing the bolt from the back of the bolt and not from the handle and it seems to give better results.

Jay
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Jay you hit it on the head, if it moves it will move length ways so it will slide inside the barrel band and not move it up or down so it will not effect the POI. The part that the barrel band attaches to is a solid piece it is not hollow like the air tube, so if there is any movement at all it would be length ways and this will not effect the POI. The only way this can be proved is by hard mounting the shroud and barrel like I have and see the end results. All I can say is with my gun there is no POI shift until the air pressure drops way too low and for the first couple of shots after the initial fill, and I have to say this also happens with some of my other PCP guns. If the barrel band went around the tube itself I would agree with you 100% but it does not, so we agree on one thing, the movement would be length ways and not vertically, Neil.
 
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Hi Neil - if I understand you, your suggestion is to put a ring or some tape or shims between the shroud and the barrel band. If this is correct - I mentioned in a previous post that I machined a delrin ring that snapped into the that barrel band and the o-ring kept it from moving and fit with no clearance between the shroud that allowed the shroud to slide axially through it. And I believe this is what was causing the larger shift in the groups.

I think the air reservoir tube is not only stretching axially but moving transversely. It could also be rotating about it's axis. If the tube is not straight it will straighten out as pressure is applied. If the tubes wall thickness varies radially or around the circumference of the tube, one side might stretch more than the other side causing the tube to banana or move transversally. Since the shroud is attached to the barrel band and the shroud attached to the stripper and barrel then 10 or 15 thou (0.010 - .015) is going to effect the POI. You may not have experienced this except at the upper and lower pressures.

I had 1-1/2 dia groups that moved all over the place. I installed the barrel band ring and it tamed the larger groups put I was still getting groups that predictably moved from upper left to lower right. When the barrel band was not installed, I think the larger groups were caused by the end of the shroud not being perpendicular to the center axis that was pulling the barrel slightly off and the stripper and barrel fighting this action, attempting to get barrel back where it wanted to be and the shroud cap, o-ring and baffles compounding the problem by putting unnecessary tension on the system.

Currently, I have removed the barrel band ring and have tightened the shroud against the receiver, replaced the o-ring at the shroud cap with a soft spring. I, pleased with the groups but I would like to see them a bit tighter and I need to find why they are still moving.

That was a bit long winded and you may not agree.


Shoot Straight - Jay

 
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After owning all 3 calibers in both gen 1 and gen 2, I have found that the first thing to do is unfloat the shroud. I use a WAR (wicked air rifles) set screw barrel band on all my mrods. Absolutely zero POI issues with a locked down band.

I also deburr and polish the airtube (where the hammer rides). I use a WAR no bounce hammer to stop hammer bounce and flatten out the shot string. If using the stock hammer I would polish it up to. The striker has a tendency to want to back itself out over time. either tap the hole in the hammer and use a nylon tipped set screw to hold it (WAR hammer has this) or find some other way to make sure the striker doesn't move.

I tune my guns for 4% or less ES over the shot string. That should show little to no poi change at close range (25-30 yards). The further out the less ES needed to hold tight groups.

Barrels tend to be the #1 issue for .22 mrods. I would try a couple other crosman barrels or get ahold of someone like Jim Gaska that has drop in after market barrels.

Have to agree with Neil. The airtube and or fill assembly is not causing your poi issue.

Sent you a PM!!
 
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Like I said AJ a lot of technically minded people tend to over think things and go by theory, I go by practice not theory, I have seen too many things where experts have claimed something and then when put into practice it has not worked. I can only say what happened in my own experience and how my fix worked for some of my customers. In 99% of the cases I have been involved with the shims and solid mount has fixed the problem, in the one case it did not work the customer sent his gun back to Crosman and it came back with a new barrel and was shooting great.
Too many guns use barrel bands without having issues to be able to put the blame on cylinder expansion, I have 3 Pneumas that are dead on accurate and they use 2 barrel bands that go directly around the cylinder, so if air tube expansion is a problem it would for sure show up with them, and I am not the only person who loves how the Pneuma;s shoot. 
One thing I have found with my Mrod that really effects the group is trigger pull, if I do not gently squeeze the trigger the same each time the group will open up, so breathing and trigger pull on my own Mrod can really effect my groups, if I rush a shot or pull the trigger instead of squeezing it then my groups are not very tight, get my breathing down and my trigger squeeze constant and it gets very nice groups, all the best, Neil.
 
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I do not have pictures of the fix, pictures were posted on the Crosman page of the yellow forum about 18 months ago. What you need to do is remove the o-ring from inside the barrel band and make a sleeve to sit inside it and be a snug fit on the shroud. I just used some Loctite to hold the thin sleeve inside the barrel band and it has never moved. I also mounted the barrel with a hard mount on mine, but if the shroud can not move then neither should the barrel, so it might only be necessary to hard mount the shroud, this part I have not tested to prove it, mine are both hard mounted and I have zero issues with POI shift. I would try just the shim on the shroud first and see if that helps your problem, if not then try hard mounting the barrel, if you are unable to make the parts I might be able to help you out when I have caught up with some of my back orders, Neil.
 
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Hi Neil - If it was not obvious, then let me take this opportunity to thank you for your involvement and contributions in this thread. I appreciate very much you sharing your experience and ideas with me and others. For it is this type of involvement and exchange of ideas that promotes growth and progress in our need for more speed, range and accuracy - please keep it coming.

I received my M-Rod on May 15th 2013 along with a P-Rod and I have been tinkering with them on and off ever since. As I remember there was a thread on the Marauder Forum sometime in the latter 2013 or early 2014 where I first read the idea of rapping the shroud with electrical or Teflon tape and later some enterprising person came out with an aftermarket part to address the solution – I suspect that person could have been you. I thought it sounded like a good idea and since I have the ability to fabricate parts and I enjoy tinkering and I fashioned up something of my own. And although it did help in certain ways it caused other issues to surface. And based on what I was dealing with I came to my conclusion of what I thought was causing the issue. So as a sanity check I used some math and theory to check my insanity. And based on my background and knowledge I concluded that there could be some sanity to my thoughts and I have been sharing them here. So although this barrel bracket concept has worked for my others, I am not convinced it is a solution for the issues that I am see on my end.

I am posting here because I am running out of ideas and I’m hoping others have experienced this and are willing to share. I believe I’m open minded and people have shared good ideas here and if something sounds like it may be a solution I’ll try it. 

Respectfully - Jay
 
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Jay electrical tape or teflon tape is no better than a rubber o-ring, they both still compress and allow movement of the shroud. With a solid shim there is zero movement of the shroud and zero movement of the barrel inside the shroud. You can not say something does not work unless you try the exact same thing and using tape is not the same as hard mounting, it might help with accuracy but only locking the parts in place will get rid of any barrel or shroud movement. It only takes 5 minutes to make the shim so why not try it, tape is only an aid for people who do not have a lathe and do not want the expense of having the parts made. Whatever is wrong with your gun I hope you find the answers, Neil.
 
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"Jay electrical tape or teflon tape is no better than a rubber o-ring, they both still compress and allow movement of the shroud. With a solid shim there is zero movement of the shroud and zero movement of the barrel inside the shroud."

Neil - I agree with what you say.

 "You can not say something does not work unless you try the exact same thing"

I have not said that your idea dosen't - I'm not arguing with you. It appers that it has worked for many and what I fab'd did a good job in tightening up my groups.

If you have pictures of your installation I hope you'll share as Dan25 requested. I'd like to see your shim concept.

Cheers - Jay
 
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I am sorry I already answered that question, I do not have any pictures of the parts, but it is not rocket science it is very simple. You just machine a sleeve to fit inside the barrel band and machine the ID so it is a very snug fit on the shroud. If you want to also lock the barrel just copy the factory part but make the OD so it is a tight fit inside the shroud, instead of being smaller and using a rubber o-ring. Once this is done there is no way for either the barrel, or shroud to move, Neil.
 
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Jay - If I slightly overfill my Marauder, it will take several shots for it to settle down during which time it may shot high and right or high an left or where ever. Then a few shots later it is good to go. But once overfilled slightly it seems to take awhile (more shots and time than first expected) for the rifle to settle down and get back into it's groove again. I've tethered the rifle to a regulated tank and tried shooting at numerous different pressures hoping to find a pressure the gun likes. But other than the dislike for slight overfill, I never found anything consistent as long as I stayed between 3000 psig and 1900 psig.
 
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