Frustrated with my .22 cal Marauder

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Killzone

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Apr 1, 2015
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I've enjoyed messin with my Marauder since I received it - I really like the platform and I'm looking forward to getting it to shoot straight. I found the pellets it likes and started characterizing the groups as the un-regulated cylinder drops in pressure - shooting over a crono, and making the different adjustments available. It would group well and then the groups would shift and then open up and then shift again. I'd put the gun away and try another day and another group shift - there was NO consistency. I've spent a lot of time on the other forum. Taped and checked the baffles and air stripper for clipping - I made a barrel band and that got my groups in quite a bit. Now I can get groups around 3/8 at 20 yards put they are not coincident. One thing they are consistent about is they move from upper left to lower right about 1.25 inches as the pressure falls from 2900 - 1900 psi - that's about 45-50 shoots - checkout the target below.

I just checked the barrel for straightness using a lathe and I pushed some pellets thru the barrel. I like to know if any one knows how the pellet should push thru. The pellet drops in about a 1/2 into the breach, past the o-ring grove and inlet hole, the there's some resistance when the pellet make contact with the rifling and for about 3-3/4 inches down the barrel. From there you can feel the pellet drag a bit until it is about 8-3/4" down the barrel and from there you can feel no drag until about 1-1/4 inches from the muzzle where it tighten up before leaving the barrel. Using a black marker around the pellet skirt and head, the pellet appears to have rifling marks all around the edges and appears to be making contact with the major diameter of the bore. I don't know if the pellet drag should disappear in the middle of the barrel and I don't see how that would cause the groups to move.

Has anyone else experienced this with their Marauder? I like the rifle but it is almost useless to me if I can't predict where it's going to group.

Any help is appreciated - Jay






 
I know what you mean. The Synrod has a few things to recommend it. Its quiet, durable, adjustable, relatively inexpensive until you start to expect top tier accuracy from it. Once you start spending money on mods to correct things like accuracy, increased FPE, etc. you will have spent as much as a nice AA S510, or at very least an AA S500. Im resigned to the fact that my Synrod is a good rifle, fairly accurate up to 50 yards. But it just isn't ever going to be a great rifle. Ive done a couple of mods to it, and they helped a little, but the money could have been better spent on something else. I have shot the Sumatra 2500 and I like it a lot. Much more predictable shot placement, smooth action, adjustable power level, and low priced for all that. I'd be all over it if it wasn't so loud.
 
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How long have you had the gun. Is it a Gen II? You could try recrowning the bbl. as snakedoctor9 suggested. I recall Ted saying he went through hell with a Gen 1 Mrod in 22. This was in one of his reviews of the 25 Mrod. and a big part of why I got a .25 

I assume you checked the scope mounts to be sure they are tight. Have you tried a different scope? The problem might be the scope and not the gun. Do you have an adjustable objective scope? If not parallax can account for issues using high power at close range. When you put the gun up do you lean the bbl against anything? I am always careful to not put any pressure on the floating bbl. out of fear of shifting the point of impact. I remember Ted saying the bolt probe on the 177 and 22 being the same on the Gen 1 and suspecting the probe did a poor job of seating the larger pellet. You might check to see if they changed it for Gen 2 Mrod in 22. Have you cleaned the bbl lately? Have you tried different pellets? I like JSB Kings. 

Lastly I looked at you graph and you note best groups in the middle of the fill pressure range. You might try the bstaley oring mod. It tends to flatten the velocity in a given shot string. By doing that mod and some tuning you might be able to get the gun regulated to delivering an extended shot string in your sweet spot of the pressure range. Get your orings at a industrial supply house and not from one of the air gun vendors who will greatly over charge you. If you elect to remove the valve you may have to get some 220 grit sandpaper and spend some time smoothing the openings in the air tube to keep from clipping orings.
 
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I have a Gen2 .22 Marauder which I won at the Pyramyd Cup last fall. At first I was very excited to get this new rifle home and give it a try, but that enthusiasm quickly turned into frustration, followed by serious FRUSTRATION!!! After the holidays I ordered a new barrel from Crosman and a barrel band from Wicked Air Rifles. The barrel band made a noticeable difference, but the new barrel really did the trick. The rifle now shot like I expected it to - meaning I could empty a magazine into nearly the same hole when bench rest shooting the 15 yard range in my basement. Every 1 to 2 tins of JSB 18.1's, I would clean the barrel and air baffles and it was good to go for another 1 to 2 tins. But then at about the 4,000 pellet shot-count, the rifle started throwing the POI again and I could not get it back, no matter what I did. Today out of frustration I lightly lubed a handful of JSB's with Balistol and shot them at 15 yards. Wonder of wonders, the accuracy was back. I shot over 100 more just to make sure it wasn't a fluke and it was not. It had worked. I then went on to try the same on my 25 caliber Marauder and it did NOT like the lube. It scattered the lubed pellets around like a shotgun. So for the OP, try a little Balistol on the .22 pellets and see if it helps your Marauder accuracy issues.
 
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"The pellet drops in about a 1/2 into the breach, past the o-ring grove and inlet hole, the there’s some resistance when the pellet make contact with the rifling and for about 3-3/4 inches down the barrel. From there you can feel the pellet drag a bit until it is about 8-3/4″ down the barrel and from there you can feel no drag until about 1-1/4 inches from the muzzle where it tighten up before leaving the barrel"

Drag, no drag, drag (the final drag being perhaps 1,1-1/2" is the choke) is not what you want ! You may get by with polishing the first restriction out, maybe not. You would like totally even pressure/resistance the entire length until you hit the choke.

Upper left to lower right while using 1,000psi is a stretch/expansion/contraction thing, go back to a truly floated barrel and see if it stays the same.

It would read like you are having at least those 2 issues ( just one issue is never enough fun to figure out eh?).

If you stay in a "sweet spot" of 20fpe ES how does it group?

John

 
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Wow - thanks for all the responses - a lot of good info. Let see if I can address all this.
The rifle is a Gen1, Model PB2263. I have checked the straightness of the barrel and the crown and were within a few thou of the barrel O.D and the crown angle. Dan - The scope is good - it was used for awhile on my HW97. I have tried soooo many pellets through this rifle and came to the conclusion that JSB heavy's 18.1gr and AOA 16.2 gr and Crow Mag 18.2 gr pellets are the most accurate. I'll consider the Bstaley O-Ring mod.

John - thanks for the pellet push test conformation - I agree that the barrel may be giving me the inconsistence groups and I'm thinking the shroud is moving the groups. After machining the barrel bracket ring that died the barrel to the reservoir the groups got a lot tighter but I suspected the reservoir was changing with pressure and moving the shroud

I'm looking to order an other .22 barrel or perhaps changing it to shoot .177. I machined the end of the shroud to make certain the end is perpendicular to the barrel block and I'm going to replace the o-ring at the muzzle with a spring between the stripper and the 1st baffle. I'll shoot some groups to see what these changes have made.

Thanks for the help - Jay
 
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Even though lubing the pellets with Balistol spray seriously helped the accuracy of my Marauder, I thought I could still do better and not be dependent upon lubed pellets from here on out. So I got to thinking - my FX .22 Independence has a full length shroud much like the Marauder, but unlike the Marauder the Independence does not have any baffles. The Independence only has an air striper on the barrel end and a small hole in the shroud about 1-3/4" from the receiver. 

So I thought, why not. I removed the shroud on the Marauder and drilled a 1/8" hole about 1-3/4" from the end nearest the receiver. I cleaned everything up, including the baffles and put it back together with the shroud 1/2 turn from full tight and the newly drilled hole facing downward. First impressions are; I think drilling the small hole in the shroud made the Marauder slightly quieter. I do not have any sound level equipment, or before and after dB readings and I was not looking for or expecting any noise level changes; but I swear there is a difference. After I put a few rounds though the rifle (at least to make sure the POI is staying consistent) I will report back on any accuracy changes.
 
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I have thought about doing that many times, but I never had the guts. I would really appreciate an update on improvements in accuracy, changes in FPS if any. My Synrod is pretty quiet as it is, a little less noise is always welcome. Now that I'm thinking about it I remember someone asking in the other forum where the "stripped air" goes if the shroud isn't vented somehow. I also wonder if a little 1/8th" vent is good why not match up the diameter in the stripper, mine now being 3/8" and see if that is more efficient. It all means nothing if your tests don't show any measurable improvement in accuracy. Very interesting.
 
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So far, 100 pellets and the results are very promising. Using a single shot tray I am getting very tight groups at 15 yards indoors and this after 100+ rounds since the mod. My brother will be here later today with the chrono and I will check velocities then. I have this nagging thought in the back of my brain wherein I am really starting to question the Benjamin magazines and their effect on the accuracy of this rifle. :<((
 
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Brother forgot the chrono so no velocity readings today. Hopefully tomorrow.

Another interesting find though. First of all from an accuracy point of view, drilling the shroud was a huge success. When loading pellets one at a time with crimped fingers and shooting at 15 yards, the rifle literally shot hole for hole, shot after shot; to the point where it became almost boring to do so. Next I tried the single shot tray and it repeated the same as long as I made sure each pellet loaded straight and true. Next was magazine loading and the accuracy went quickly downhill. I noticed however the gun threw pellets whenever the magazine moved excessively during a pellet loading process. Finally I started holding the magazine firmly in place with my free hand while pushing the pellet home. Each time I did so the POI and grouping was near perfect.

All four magazines I own have noticeable front-to-back play while installed in the rifle. It appears this front-to-back play has a role in consistent pellet loading, which in turn affects overall accuracy. My brother came up with a simple solution to remove the magazine front-to-back play and I am going to give his idea a try.
 
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SCP - My HW100 has a few holes, maybe .06 - .09 around the shroud - I thought about doing the same with the M-Rod.
I think you can minimize the clearance between the mags by loosening the 2 set screws that hole the barrel in place on the receiver and with a mag in place push the barrel back until you can just remove the mag from the receiver.

I had some success with my tinkering. I removed the barrel and checked the it for straightness by checking it in a lathe and turning it. Using a dial indicator to see where it needed straitening. The barrel was not badly out but it needed a little work. I checked the rifling and crown and they were not out by much - a few thousands. Then I machined the back of the shroud to be perpendicular to the barrel. When I reassembled I removed the o-ring and put a soft spring between the stripper and the first baffle and put a coat of silicone oil to the inside of the shroud and the stripper o-ring. Left the barrel bracket off and shot the groups below. 



I think I'm heading in right direction. I'll order another barrel and try a few other ideas that you have suggested like the Prolix ect ... but the group on this target are looking better . I was in a bit of a hurry to see the results and the I was losing the sun. I'll post more targets later and it will be interesting to see if the groups shift the next time I try.

Shoot Straight - Jay
 
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I had similar problems with my own marauder, every time I picked it up the POI was all over the place, many of my customers have experienced similar problems. One of the problems with the Marauder is that the barrel and shroud sit on rubber o-rings, this allows movement of the barrel and shroud and can cause alignment problems. Customers lean their guns against walls which can cause a flat on the O-rings. I hard mounted my barrel and shroud so there is zero movement in them and now I have no change in POI no matter when I pick the gun up. I made a few kits for customers and they said it cured they POI shift too. I do NOT make kits any more because of the bad tolerances on the Marauders, seems every single part is a different size which required me to have the shroud and barrel bands to make the parts and became too much of a hassle. You could try using a larger o-ring in the barrel band to hold it tightly, or use some tape around the shroud to restrict the movement. I have read so many different articles about the Marauder accuracy problems but as long as there is free movement in the barrel and shroud and they are sitting on compressible o-rings there are going to be problems. I had a friend who wrapped his thumb over the shroud when he shot his Mrod, his POI was all over the place, this just demonstrates how the shroud can move and when the shroud moves so does the barrel, Good luck with your problems, I hope you are able to fix it fairly simply, Neil.
 
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Thanks Neil, I am familiar with the barrel band fix. I machined a delrin band that just slipped over the shroud and had a groove for the o-ring in the shroud bracket to snap into. It allowed the shroud to slip though to allow for thermal expansion but held it firmly. It did help my groups although the groups would move as the pressure in the reservoir dropped and I think the reservoir was moving the bracket.

I also would unscrew the shroud 1/4 or a 1/2 turn and seemed to help some. I think that was telling me the end of the tube was not matting up with the receiver properly and I think I solved that problem by machining the end of the shroud. I noticed in the Gen II parts list and exploded view that they added more baffles and a spring and on the other blog someone was telling how they oiled up the o-ring at the muzzle so after machining off about .040 from the end of the shroud the o-ring was going to be too tight and by putting in the spring and having previously rapping tape around the baffle to remove most of the clearance between them and the shroud that keeps the baffles from rattling around and possibly clipping pellets - it seem to have worked - time will tell.

Stay tuned - Jay
 
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Jay I am not sure why you think the barrel band moves with expansion of the tank, the barrel band goes around a solid piece of aluminum at the front of the air tube and it does not expand with the pressure of the air tube. I have seen a few people post this, the band does not go around the air vessel itself it goes around a solid piece of aluminum in front of the air tube. I have my Marauder shroud solidly mounted, internally and inside the barrel band and I get zero movement in my POI with pressure changes of the air tube, The only time my POI changes is when I let the pressure get too low and also when I first fill it, that settles down after a couple of shots. I have noticed this with a few of my guns and have no idea what causes it, but 2 shots and it is right on the money again. You will also find that mounting the rear of the shroud will make it better, rather than having it screw onto the spacer. All told the Mrod is a good gun for the money but it does have a few design flaws that are easy to correct with a small lathe, Neil.

By the way, I added an LDC to mine and removed the factory baffles from the shroud,with the LDC on the gun it was extremely quiet and removal of the baffles made little if any difference, this might help rid you of the problem of clipping the baffles. 
 
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“
Jay I am not sure why you think the barrel band moves with expansion of the tank”

Hi Neil and thanks for replying to the thread. Let me see if I am able to explain why I believe the barrel bracket is moving. I understand the bracket is attached to the air reservoir and appears to be rigidly attached – but let’s take another look at it. Let me start by admitting that I have not done any actual measuring and I’ll be going off of approximations.
The barrel bracket is attached to the end of the air reservoir tube approx. 16” from where the barrel attaches to the receiver. And if you have a barrel band installed between the shroud and the bracket we can say for all practical purposes that the shroud is part of the barrel bracket and will move with it.

Let’s say the inside of the air reservoir is between 1.00” and 1.125” in diameter and it gives us an area of between .785 and 1.227 square inches – let’s say 1.00 sq-in. So when you fill up the air reservoir the pressure pushes against the reservoir end plug with equal force – let’s say 3000psi = 3000 pounds of force. That’s about the weight of a Mini Cooper. So shoot it down to say 1800 and you have a change of 1200psi and a change of force against the end plug of 1200 lbs of force. It is not difficult to believe that this force would not have an influence on the end plug or reservoir cylinder – and question if this influence is repeatable.

The air cylinder is getting longer as you fill it and shorter as you shoot and lower the pressure. If the cylinder is not perfectly straight or twisted as you increase the pressure the cylinder attempts to straighten itself out. If the end fitting moves even a hair, it’s going to affect the Point of Impact – let’s see.

If the cylinder is, let’s say 16” long and the bracket moves a hair – the average human hair is .003 to .005 of an inch in diameter - let’s say .005 then the angle of change is .0179 degrees and at 20 yards that would place your shot .225 inches off. Is it possible that the cylinder is moving more than a hair – I think so and I think that is one of the reasons most PCP barrels are floated. If it is 2 hairs off then your shoot is almost a ½ inch off. If that’s OK with you then no need to be concerned. But that’s not accounting for differences in, velocity, pellet weight, wind and the shooter. My investigating led me to believe the bracket was moving and is just one of the issues with this rifle.

Shoot Straight Neil - Jay
 
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