Marauder Cocking Crisis after FT rebuild

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FlexWagtail

FlexWagtail

Member
Aug 11, 2016
130
24
MD, United States
Hundreds, if not more than1k smooth, satisfying, accurate shots after a regulated Marauder .22 rebuild and then the cocking just mysteriously started stiffening up and then flat out became impossible over about 30 shots

Oh, yeah -- I've dissassembled and reassembled twice -- and it all works great until you put it back together and shoot 5 or ten times. Then it stiffens up and becomes impossible again.

This occurs regardless of hammer spring tension. I've tried full slack counterclockwise and snug clockwise. At full CCW there's plenty of play before engaging spring. Maybe 1/4 to 1/2 inch

I come to 'ye forum gurus for advice.

The gun is set up as follows to get me 20 ft/lbs regulated:

  • Stock valve with lighter spring
  • Lightweight hill hammer with stock spring
    • On diagnosis, the hammer runs smooth in the tube and engages/releases the sear just fine -- until you put the thing back together !#@%*
    • Hammer has light wear marks where it engages, but like I said, It locks up on sear just fine when tested in dissassembled state.
  • Lawyer spring in trigger is out. But sear seems to engage the hammer just fine. I don't think we have a trigger problem

  • Bolt is in good shape, best I can tell. Removed, inspected, reinstalled. Smooth. Hex nuts engaging each other fine.

I'm out of ideas, except to return it to full stock, which defeats the purpose

This gun is regulated with a Marmot Militia barrel and was shooting super smooth tuned down to 20 ft lbs --- then this?

What do you all think?




 
Check the bolt tension screw that is on the top of the airgun. Not exactly sure what it is called but that could very well be causing binding on the bolt if it is to tight. Its got a spring in that pushes a small bearing against the bolt. Make sure that it is lubed. I know some will frown against using motor oil with a PcP but it is only on the bolt and not anywhere where it can cause issues. Just a small amount should work just fine. Thats all I have ever used on my bolt to keep it nice and smooth. Just check that tension screw because that sounds like it could be the issue. If for some reason it is just getting tighter as you cycle the bolt several times put a small amount of locktite on the threads. This should keep it from doing this. Also check the little bearing to see if it has a flat spot. Other then that just make sure you adjust it a bit on the loose side. You want that bolt working smoothly. 
 
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Check the bolt tension screw that is on the top of the airgun. Not exactly sure what it is called but that could very well be causing binding on the bolt if it is to tight. Its got a spring in that pushes a small bearing against the bolt. Make sure that it is lubed. I know some will frown against using motor oil with a PcP but it is only on the bolt and not anywhere where it can cause issues. Just a small amount should work just fine. Thats all I have ever used on my bolt to keep it nice and smooth. Just check that tension screw because that sounds like it could be the issue. If for some reason it is just getting tighter as you cycle the bolt several times put a small amount of locktite on the threads. This should keep it from doing this. Also check the little bearing to see if it has a flat spot. Other then that just make sure you adjust it a bit on the loose side. You want that bolt working smoothly.
Click to expand...

Awwww, You got my hopes up -- but no dice. Same jammed up situation regardless of tension -- including 0 tension with tension screw removed. For a gun with such simple guts inside this sure is a head scratcher.
 
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Your setup is surprisingly similar to mine (.22cal FT marauders aren't that common). The last time I took mine apart to clean the internals, I tightened the cocking bolt too much into the hammer. Since it is MDS hammer, it deformed very slightly causing it to drag just a little but it would drag from the first shot on so I guess that might not be it.

Did you happen to wet lube your hammer or tube? Meaning silicone, oil, etc... If so, I guess its possible that the hammer is causing vapor lock behind the hammer. That would explain the gradual increase in cocking effort. 

Not a guru just a tinkerer.... Good luck!!
 
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And the answer is: LUBE

The word “bind” by BigTin and the obvious oveooked suggestion of “lube” by dleadslinger caused me to review

I had been using a dry moly lube supplied by hill with the hammer and felt like the tube was in good shape. But I was feeling a “binding” sensation as BigTin described.

Very close inspection of the hammer showed wear on the edge where torsional binding might occur and where the hammer slides over the sear. Didnt look like much, (less than 1/1000) but maybe enough to provide just enough wiggle for binding up (Aluminum vs Steel)

So I switched to some liquid molecular gun oil and Voila! Cocking now smooth snd gained some FPS with the more frictionless hammer

That oil is bound to get goopy over time, So ill have to do more frequent tear downs to clean tube

Chime in with your favorite lube suggestions in circumstances like this
1540833584_16884320345bd741307101e0.55283362_32339AB4-803A-4A6C-9D03-F478C9F23D96.jpeg





 
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I had a similar event when tuning a friends 25cal Marauder (2nd v). This was my second attempt at tuning and since it was for a friend I wanted it to be a good one. My plan was to open the air flow a little and use some powdered lube then see what I could do to get decent power and longer shot count out of the adjustments. 

When I opened it up, I found the tube had several gouges where the hammer traveled so that was addressed and the hammer was polished. I also polished the ends of the hammer spring. The powder lube I used was Motor-Mica that I used when prepping cases for reloading powder. It cocked smoothly but after several magazines the cocking started getting progressively harder then acted as though it was in coil bind.

I opened the gun again and noted some rubbing marks on the tube but no real scratches. Thinking it was a lube problem I again worked the powered lube into the tube/hammer and tried again. Like last time, it cocked smoothly for a couple magazines then got to the point it would not cock at all.

I 'assumed' the dry lube was the culprit so I cleaned the tube and hammer then lubed them with Ultimox 226. I also wanted to check the hammer spring guide (adjustment) to verify my initial data regarding adjustment limits and was surprised to see it only took a half turn to come loose from the threaded end plug. Thinking that it might be working itself out of my set point I used some thread locker on it.

I can't say if it was the lube change or the thread locker on the guide that seems to have cured the cocking issue since both were done at the same time but it's had hundreds of shots since and is still cocking smoothly. If I ever have another issue like this again, my first check will be the hammer adjustment.




 
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I also keep my hammer lubed up. I know I have read here and there not to lube up that area of the mrod because it will attract dirt and whatnot. Personally I have never had any issue with dirt but then again I dont treat it like an ak47. Again I use good ol motor oil. Again I know people frown on this but the hammer location is not an area that need to be worried about any ill effects. I have tried silicone there before but motor oil just works much better. Silicone lube is not really made for metal on metal contact anyway. 
 
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My favorite. I pout a coat on the hammer and also inside of tube letting it dry overnight before assembly.

1540838093_2909545865bd752cd3d3f13.37108729_20181029_143235.jpg


The way to "solve" the Crosman hammer issues (without an MDS hammer which can change size with temperature) is to drill the hammer and insert delrin "pegs" for the hammer to slide on. Some hammers I have done rear bottom, and other rear bottom and front top.


 
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One of the easiest things I do to ALL moving parts, even if anodized, is polish them to a mirror finish. Inside of the hammer, where the spring sits, the entire outside of the spring, the adjuster on the rear of the spring in the cap. Outside of the hammer. Face of the striker. Top of the sear.The slot that the hammer screw rides, along with the screw itself. Every part that moves in there, and bearing surface, polish.

I also took a 10 gauge shotgun swab, chucked it in a drill with a small extension, and polished the tube to a mirror finish.

With all these parts highly polished, you need very little, or no lube, as everything is as smooth as a baby's bottom. This will also add more consistency in the shot cycle, and you will see your velocity in general tighten up.



Tom Holland 
 
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