Tuning Non regulated Marauder keeps increasing FPS after tuning

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Aimright

Aimright

Member
Jan 28, 2019
645
229
AZ, United States
I have been tuning my .22 Marauder to about 750 fps and I have been recently experiencing about a 70 fps velocity increase after shooting maybe 200 pellets.. After researching some I am thinking it was either the hammer throw or hammer spring coming out of adjustment so I removed them both yesterday, coated the threads with vibratite, and reinstalled. Hopefully that fixes the problem.


But...does anyone know if the transfer port screw can also back out, and if so is there anything you should do about it? I have noticed if I install the lock grub screw that goes on top of the transfer port screw too tightly it will apparently turn the port screw clockwise a bit and change my desired tune. So I now just screw it down until it barely touches the port screw, but not sure that accomplishes anything as far as keeping the my transfer port setting “locked”.
 
Try a heavier hammer spring or start from a lower fill pressure. Sounds like valve lock. If you set everything back to original factory settings that would be the ideal tune if filling to 3000. Adding a Huma regulator is probably the easiest thing to do to get what you want however the gauge will only read regulator pressure so I would just try a heavier hammer spring first. Very cheap from a local hardware store.
 
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Me-: apologies for my potential ignorance, but what I know valve lock to be is when the valve “locks” closed because of too high of pressure, so I really don’t see that being the problem. So what I think is happening is either the screw that adjusts the hammer spring or the screw that sets the hammer throw is gradually backing out or in after a course of 200 pellets are shot. I think my fps is gradually increasing from 750 to about 820 fps as I shoot those 200 pellets, I notice this by the increased sound, air use, and change in point of impact. I fill my gun to 2400 and end at 1900 which gives me a sweet spot of about 25 shots within + or - 1% fps. I guess I can see a stronger hammer spring perhaps keeping the hammer spring screw from backing out.
 
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Now that you provided the proper amount of information, it’s easier to understand the direction you went. I think the steps you took to correct the problem are a good starting point.
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You know sometimes I go back and read one of my previous posts and come to the embarrassing realization that I left out a few key words or sentences that would make things comprehensible! Yes, I hope the Vibra-tite on the hammer spring screw and the hammer throw screw will do the trick and keep them from backing out, should know in about 200 pellets....
 
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Me-: apologies for my potential ignorance, but what I know valve lock to be is when the valve “locks” closed because of too high of pressure, so I really don’t see that being the problem. So what I think is happening is either the screw that adjusts the hammer spring or the screw that sets the hammer throw is gradually backing out or in after a course of 200 pellets are shot. I think my fps is gradually increasing from 750 to about 820 fps as I shoot those 200 pellets, I notice this by the increased sound, air use, and change in point of impact. I fill my gun to 2400 and end at 1900 which gives me a sweet spot of about 25 shots within + or - 1% fps. I guess I can see a stronger hammer spring perhaps keeping the hammer spring screw from backing out.
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Aimright, so this 70 FPS increase that your saying, your judging by the sound of the gun, and not verified by a chronograph? If not, I suggest before you make further adjustments you should check it thru a chronograph and keep a notebook dedicated to the Marauder to jot down your findings. 

If it truly is the hammer spring adjustment, on the gen 2 marauders, I believe at the rear, and on top of the tube, is a screw that normally doesn’t get removed at disassembly. Forgive me, but I’m going off of memory. Remove that screw and drop in like a 3-5mm length(can’t remember the actual length, but easy to see what’s needed)of weed eater line. When you re install that screw it will mash against the hammer spring adjustment bolt threads, and act like a nylock nut at the hardware store, keeping that bolt from moving. Of course, do this after you get your gun shooting to your liking.
 
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Sounds like valve lock to me (AS-IS) and I would put a heavier hammer spring to ALSO act as a HDD - TSS - SSG device and B-Staley O-Ring mod..



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Odoyle, could you explain what your definition of valve lock is, and how that effects my problem of increasing velocity creep? I have read about the HDD-TSS-SSG mods and have thought about them a time or two as something that will reduce hammer bounce and air usage. Maybe that is a something I will consider if my current fix attempt does not resolve my velocity creep.





Aimright, so this 70 FPS increase that your saying, your judging by the sound of the gun, and not verified by a chronograph? If not, I suggest before you make further adjustments you should check it thru a chronograph and keep a notebook dedicated to the Marauder to jot down your findings. 

If it truly is the hammer spring adjustment, on the gen 2 marauders, I believe at the rear, and on top of the tube, is a screw that normally doesn’t get removed at disassembly. Forgive me, but I’m going off of memory. Remove that screw and drop in like a 3-5mm length(can’t remember the actual length, but easy to see what’s needed)of weed eater line. When you re install that screw it will mash against the hammer spring adjustment bolt threads, and act like a nylock nut at the hardware store, keeping that bolt from moving. Of course, do this after you get your gun shooting to your liking.
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Big Ragu: You probably don’t remember this but two years ago when I first bought this Mrod, you recommended some pellets for me to try and also that I get a chrono, and even recommended a Pro Chrono! So I did heed your advice back two years ago (thanks!), got the Pro Chrono DLX, and yes my 70fps velocity creep was verified by chronograph. My symptoms of more air usage, sound change, and POI change are what drove me to pull my chrony out and verify.

So I will have to check your fix out if mine fails, but I think what I did by putting vibratite on the hammer screw threads hopefully accomplished the same thing. Referencing the parts diagram I added vibratite to the hammer spring adjustment screw threads #43 and also the hammer throw adjustment screw threads #40. Your suggested fix I think is the screw that comes up from the trigger area into the hammer spring nut #39 on the diagram?

EDC26970-C62C-4DFA-B230-EA182AA07316.1617282920.png







 
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FWIW: The hammer spring adjustment tend to loosen, not tighten, so the culprit is probably the throw adjustment. It must be backing out to increase power. That would be allot of movement on the throw. What is your throw adjusted to from full CCW? and where did you find it after the increase?

Vibratite will help, but can peel off the throw after adjusting a few times. Replacing the worn out acetal pin with the weed trimmer line (blind hole) may be needed.
 
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FWIW: The hammer spring adjustment tend to loosen, not tighten, so the culprit is probably the throw adjustment. It must be backing out to increase power. That would be allot of movement on the throw. What is your throw adjusted to from full CCW? and where did you find it after the increase?

Vibratite will help, but can peel off the throw after adjusting a few times. Replacing the worn out acetal pin with the weed trimmer line (blind hole) may be needed.
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Thanks Fuzzy, I know yesterday I should have turned everything back ccw to stop so I could compare to my tune settings to see if they actually moved, but sadly I did not. I did notice the throw adjustment screw was very easy to turn when I took it out of the gun yesterday, really no resistance at all. So I did not look at the acetal pin yesterday while I had the throw out, is that a grub screw and where I would put the weed line? Also could my transfer port adjustment be backing out? I notice when I adjust that when I am trying to fine tune my velocity that a very small turn equates to a fairly significant velocity change.
 
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There is no grub screw, unless a prior owner added it. The pin is in a blind hole, below the throw adjuster screw. The pin (item #27) will have been "mashed" over and will be hard to see. Use a pick to get it out or a small drill turned by hand. Insert a piece of weed-eater line into hole, and thread back in the throw adjuster screw.

Typically the valve screw does not move. Since you were able to return to your tune without adjusting it, not the problem in your case. I recommend baselining and recording your adjustments, hammer preload, throw, and valve, so you can quickly get it back in the ballpark, in the future.


 
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Yes, now that I see that diagram it is screw #29 that has to be removed and a piece of weed eater line dropped in. Good luck, and enjoy that Marauder. 

Also, if it’s still around, go to the marauderforums.com. Last I was there it was somewhat still active. I think I read every tread posted going back into the years when the Marauder first came out, to school myself. I remember thinking it was nice they had sub forums that separated the Marauder by calibers. It also has a sub forum for the PRods, too.
 
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Try a heavier hammer spring or start from a lower fill pressure. Sounds like valve lock. If you set everything back to original factory settings that would be the ideal tune if filling to 3000. Adding a Huma regulator is probably the easiest thing to do to get what you want however the gauge will only read regulator pressure so I would just try a heavier hammer spring first. Very cheap from a local hardware store.
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Welcome NEWBY.

Thought similar.
 
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I wanted to follow up on this as I wanted to make sure I have the OP the correct advice on the weed eater line. I contacted Tim Hill of hillairguns.com, who pretty much is another master of this platform and makes sweet parts and performance kits to really take your Marauder up to the next level.

He said 3mm long, and this length is important, and weed eater line thickness is to be a .220 or in that area. Drop the 3mm piece in, then replace screw 29, and cinch it down.

He also said vibratite works, but after about 6 sessions of tuning which involves turning that hammer adjustment guide back and forth, the vibratite will need to be reapplied. Make sure the vibratite dries fully before installing the guide.

good luck, man
 
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...Sounds like valve lock. ...
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That would be the first thought, except - the op said "...experiencing about a 70 fps velocity increase after shooting maybe 200 pellets...."

200 means over several fills before the velocity increases, so not likely valve lock, partial or otherwise.

If he had said after 10 or so pellets, then early valve lock would be more likely.

Partial valve lock is easy to verify. Refill the gun. Did the velocity drop back to 750fps?
 
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