Benjamin Benjamin M-Rod Reset

[vazsev]

Hi All. I am new here and new to PCPs since I have always shot break barrels. A few weeks back I bought a used .25 cal M-Rod off a buddy who tried to tune it but gave up halfway. My idea is to pick up where he left off and try to get this thing shooting again. I currently have a hand pump he gave me but have a cheap Vevor compressor and chronograph on the way. Should I try to tune this rifle or try to get it back to the factory setting? Are all M-rods set the same at the factory? If so does anyone have the specs so I can reset it or how would you all recommend I go about this since he said he doesn't have that info anymore?

 

[3Crows]

I'll have to try stock spring. Since instructions said to use heavier spring for 25 I went ahead did out the get go. TP I am assuming is transfer port and I have it all the way open right now. As far as dimensions for it I have no idea I think it's a gen 1 marauder since buddy said he bought it 10-15 years ago.

I did back off the 1/8 turn as directed as well so I might try to back off a bit more as well see if that helps. I'll try to get some shots in this weekend see what works.

By TP I mean the transfer port itself. The stock TP for the M-Rod .25 is around .14 ID. The valve port restrictor is inside the valve and reached with an Allen key through the side of the valve.

The reason your shot string is declining is probably because you went to the higher power spring and you do not have enough restriction in the flow path (by whatever means you have to vary the restriction). The 914 fps for your initial shot is just too fast to get a curve (or more than 16 shots) IMO. I also imagine you are wasting a lot of air out the barrel after the pellet has long gone.

Every rifle is a little different, you will just need to play with it to see what does what.

 

[vazsev]

By TP I mean the transfer port itself. The stock TP for the M-Rod .25 is around .14 ID. The valve port restrictor is inside the valve and reached with an Allen key through the side of the valve.

The reason your shot string is declining is probably because you went to the higher power spring and you do not have enough restriction in the flow path (by whatever means you have to vary the restriction). The 914 fps for your initial shot is just too fast to get a curve (or more than 16 shots) IMO. I also imagine you are wasting a lot of air out the barrel after the pellet has long gone.

Every rifle is a little different, you will just need to play with it to see what does what.

I'll try switching out the springs this weekend and run past the chrony to see what come up. Hopefully that's the issue.