MarauderAirRifle.com

[wahoowad]

I have about 700 rounds through my GD tuned Marauder. It has shot Ok although never as consistent as my neighbor's bone stock 25 Marauder. Mine will shoot very tight for 2 or 3 shots (cloverleaf 3/8" at 25 yards) but a 5 shot group usually has one or two fliers that open the group to 3/4" or 1". Again, I was able to shoot cloverleafs with my neighbor's stock gun. Also getting some variations in POI up to 1/2".

I kept shooting my gun to break it in. It was still doing pretty good, I'm mostly plinking targets at 25 yards that I could hit 19 out of 20 shots. Around 500 shots it started to shoot worse...opening up a bit and some slight shifting of the POI. I decided to clean the barrel for the first time using googone and weedwacker cord. It wasn't too bad, took maybe 10 patches or so. Once done I very lightly lubed my o-ring with a silicone lube and put some gun grease on my bolt.

Cleaning didn't really improve things. I'm shooting tethered and my tank has been in the 2400 - 2000 psi range as I have been noticing the worsening trend. Is it possible the gun just starts to open up a bit in the lower pressure range? I have not had my scuba tank refilled yet so have not been able to compare how well it shoots when I get it back to 3000 psi.

The gun reassembled fine after cleaning. Shroud is symmetric inside the barrel band. No signs of clipping seen. I'm shooting JSB Kings and Benji Domes which have been the best in this gun. Other than getting my tank refilled (of which I am skeptical as my neighbor's shoots fine from 2500 - 1800 psi) what else can I check? I'd call GD but have a real hard time getting ahold of him.

[USMCShooter]

These guns absolutely fall off hard in accuracy at lower pressures! If Greg tuned it, I would pretty much guarantee that it's set up to run at 3000-3100psi fill......does it have the air tube extension? If so, that will change it even more. Greg usually provides the tuning specs for each gun he tunes, and you need to run it as close to those figures as humanly possible.

Out of the box (haven't started tuning it yet), on a 3000psi fill, when I get below 2400psi the groups start going downhill quickly....and within 3-4 shots open up to an inch or larger.....my advice is to consult the paperwork Greg provided and air it up to the tune pressures....I'm betting your groups will improve significantly.

s/f

Jamie

[wahoowad]

Yes, this is a GD tuned gun and has the extension. I did not get any tuning specs from him, sort of a sore spot with me right now. I've asked him several times for that.

I wouldn't have thought of 2400 psi as low pressure since I expected it to do well 3000 - 2000 psi. Heck, I shot my neighbor's down to 1800 psi and it kept going great accuracy wise for all 3 magazine fills (no extension either). But I hear what you say about it being a tuned gun so maybe it does behave differently? Kinda would expect it to exceed the stock capabilities though.

I'm getting a fresh tank fill today so will see how it does. Also will check the basics like stock and scope screws. Anything else to check?

[USMCShooter]

That's unusual that Greg wouldn't put the tune sheet in there. Yours must have slipped through the cracks....there were some inconsistencies there for a few weeks. But, I do know that he usually tunes to the 3000-3100psi range. Do you have a chrony? I would air it to 3100 and put it across a chrony to check consistencies etc. Greg tunes the guns, and I know Roald was doing them too. They normally tune to the customers request, ie, shot count, speed etc.....and try to get it as close as possible. A semi-rough tune if you will. But, time spent across a chrony can refine the gun a lot.....some guns require adjusting for several hours of shooting in order to find just where it loves to run and to balance the valve.

The stock guns say they are tuned to run at 3000psi. Mine doesn't hit it's sweet spot until about 2800psi and falls off dramatically at around 2200-2400psi. Giving me only two mags of true, tack-driving accuracy.

The air tube extension, while adding volume, does indeed affect how the gun uses the air....an anomoly that has baffled several of us. My buddy's .22 without the extension ran great when I first tuned it from 3000psi, down to 2000psi...getting 32 shots.....with the extension, I tuned it to 3100 (it liked it better there for some reason...another pressure anomoly), and it would get 57shots down to around 2200psi....then went bonkers and started spraying pellets dramatically.

I would say to put it across a chrony to see what the gun is actually doing across the string. If it's got bouncy spots in it, then the valve isn't balanced properly....not good for groups, and will create up/down POI shifts....this can usually be remedied with the hammer/stroke adjustments...but again, the chrony is the true test.

Not sure what kind of scope you're running? Have you ensured the shroud is good and tight, breach/barrel o-ring is good? Greg uses a much better o-ring in them than factory. Not exactly sure what level of tune you requested either?

s/f

Jamie

[wahoowad]

I have a chrony and will test a string.

I did not request any special tuning other than his 'standard tune.' I was not asked any questions.

I'll double-check the shround and baffles but it all felt pretty good going back together the other day. I have the shroud knob tightened down medium snug and the o-ring is definitely in there. How tight should I tighten that shroud knob? Finger tight? As tight as I can get it by hand?

[jtb56]

For what it is worth my .25 Mrod shoots 3/4'' and smaller groups @ 50yds. I have done no tuning and fill to 3000 psi.
I get 16 consistent shots then accuracy drops considerably. Pressure gauge reads 2200 after 16th shot. My rifle is
partial to JSB Exact King 25.4 grains. I do not weigh pellets but do lube with Krytech. I hunt this rifle with complete
confidence in hitting what I aim at. Jamie's advice is sound, fill to 3000, chrony shots, tune if necessary. Bet you will get
good results immediately if you have the right pellets for the rifle. Good luck.

[USMCShooter]

Mine too is just exceptionally accurate....I'm working on posting with some pics....but I've got 4 dime-sized groups at 100 yds.....without tuning anything....

As for the shroud....as tight as you can get it by hand....I put the end-cap on as tight as I can get it...then I grab the shroud and take it clockwise until the whole assembly is as tight as I can get it.

Mine really likes the JSB Kings as well....it likes the Benji's too...but the Benji's are nowhere near as consistent as the JSB's....Crosman's QC on their pellets sucks....I've head-sized about 2 full tins now and around 1/4 of them fail....I head size with calipers to .249, which is what the JSB's are.....out of a tin of JSB's, I have less than 10 that are not right on .249....again, with the Benji's, at least a quarter of them are out of range.....so I recommend the JSB's.....

Keep us posted on your progress, but I am 99% positive that with a full 3000psi fill (I'd try 3100 also) you're going to see your accuracy improve dramatically.....if not, pull the shroud and shoot it without it....no improvement means it's not the shroud....next, single-load a few and see how that does....I've got one of my mags giving me fits right now...it's a little loose (the inside star) and is about to go back to Crosman....compared to the other mag I have, the pellet cavities are visibly bigger, and cock the pellets into the breach.....kicked my butt for about 2 hours until I figured it out....when I single-loaded them, they were right back into one hole.....

Keep us posted....

s/f

Jamie