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PostPosted: Fri Feb 13, 2015 6:38 pm 
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Location: Coalmont BC
I said it was possible (bent?), not likely.... Most likely is hammer drag, either on a burr or sticky lube....

Bob

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PostPosted: Sat Feb 14, 2015 8:12 am 
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I did a partial tear down of the breech and hammer/striker. I did notice wear marks on the lower part of the hammer that is facing towards the trigger/sear. I polished the hammer with 600/1000grit wet dry paper. I also did the slots and the tube area were the hammer sits and the screw head that guides the hammer. Going to run a shot string tonight and report back.

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PostPosted: Sat Feb 14, 2015 10:00 am 
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I've never had an MRod, and you said you adjusted to lower the velocity, but you didn't say what you did.... I know that it has 3 adjustments, a velocity screw (transfer port), hammer travel, and hammer preload.... If polishing your hammer and removing any burrs doesn't get rid of the wild velocity swings, you could try extremes of tuning on the hammers.... By that, I mean instead of reducing the hammer preload and travel both, try leaving the spring preload fairly high (to overcome the friction) while reducing the stroke drastically (to reduce the pressure range and hence the velocity).... Once you have the pressure range you want THEN play with the velocity screw as your primary way of setting the power....

Hammer strike = pressure range....
Transfer port size = power....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sat Feb 14, 2015 11:05 am 
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Bob, the mrod looks almost identical to the bam b50/51 minus the size of the hammer and stock spring and the addition of the velocity adjuster.

let me see if I understand. if I want to keep the fill pressure low increasing the hammer spring but increasing the striker would keep things the same? then using the velocity adjust to get it back to the fps I want?

edit. by increasing striker I meant shorten the travel.

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PostPosted: Sat Feb 14, 2015 12:03 pm 
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Correct, preload and travel are interchangeable, more of one and less of the other (in the right amounts) ends up being the same effect (ie pressure range)....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sun Feb 15, 2015 3:56 pm 
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looks to be more stable after I polished the hammer and adjusted the hammer spring about quarter turn in (CW) and increased the striker stroke the same amount (CCW), small 1/8th turn (CW) on the velocity adjuster. Here is the new string. If i drop off the the last 10 shots my ES is looking pretty good. Any idea's to get back a good 30 shots? Higher fill pressure?

870 2K Fill
873
874
876
887
878
879
892
905 HIGH
893
877 1800 PSI
886
894
880
876
874
900
899
899
895
898 1600 PSI
890
876
868
856
845
839 LOW
842
840
848 1400 psi end

Edit, i actually increased both the hammer and striker, i forgot that i should have probably shorten the striker instead.

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PostPosted: Sun Feb 15, 2015 4:58 pm 
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just shortened the striker about 1/4 turn CW. still getting higher FPS average 880fps on 10.3g JSB. I'm liking this Marauder and can't wait to see how she groups with the JSB's.

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PostPosted: Sun Feb 15, 2015 5:54 pm 
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Nice! Looks like you've sorted out the shot to shot variation. I've got to get my PAL so I can play with those sort of velocities :)


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PostPosted: Sun Feb 15, 2015 8:33 pm 
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it's almost were I want it. yes get your pal asap!

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