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Tuning Need help tuning the Benjamin Marauder F and T 22 with Lothar Walther barrel

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JR10CHD

JR10CHD

Member
Mar 2, 2021
8
0
Ohio, United States
Hi, I am new to the pcp world and I just got a Benjamin Marauder Field and Target 22 with the Lothar Walther barrel. I am using the JSB Exact Jumbo 15.89 pellets. At first I was having a hard time getting it to group well at all, so what I did is I read some blog where they took the front muzzle cap and unscrewed it a quarter turn and then I unscrewed the barrel shroud off a half turn, seen a little help but then I put a o ring in between the barrel band and the barrel shroud that helped out a lot . Now what I am having trouble with is I am getting a vertical string up and down. I am running a chronograph and noticed if I fill the air tank up to 3000 psi it starts out at 750 fps when it gets to 2700 it climbs to 770 and when It gets to 2000psi it goes up to 790 to 800 and that will last up and down to about 1500 psi then it really drops off. I don't know if this was the right thing to do but I only filled it to 2700 one time and it seemed to of held in the 770 fps to 790 fps. would any one have any ideas or am I on the rite track. 

The ranges I am shooting at is 25 yards and 50 yards. 25 yards is now just one little hole 50 is where I see the vertical string. I did weigh the pellets and held 1/10 th. grain tolerance, and cleaned them, don't now if that really helps, still have mix feelings on that. Any ideas would be greatly appreciated. 
 
JR,

If accurate (gauges) it seems your coming off the reg at 2,000psi. ? That number seems to high to me. You can perhaps "tune for the knee" for less variation on/off the reg.

What does crosman et al. say the reg comes set for? A reg should hold 10fps (20 would be some crazy absolute mas ES) for full until off the reg.

Folks will chime in I'm sure and I've only used the 1st gen DIY reg. . Try a bit of "tuning" (turn adjustments) and if your reg is set too high have crosman warranty it.

And keep us posted.



John
 
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So today I talked to the people at Crosman and they had me do some test where I set every thing to factory spec and shoot it threw the crony. I had a lot slower feet per second starting out at 703 fps at 3000 psi. to 713 at 2500 psi and 735 psi at 2000psi and then 764 at 1500 psi and lastly 719 at 1000 psi. This is a total of 134 shots in one fill. Crosman said to send them my shipping address and they will send me a return label, so tomorrow it will be sent out as soon as I get the return label. 
 
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So today I talked to the people at Crosman and they had me do some test where I set every thing to factory spec and shoot it threw the crony. I had a lot slower feet per second starting out at 703 fps at 3000 psi. to 713 at 2500 psi and 735 psi at 2000psi and then 764 at 1500 psi and lastly 719 at 1000 psi. This is a total of 134 shots in one fill. Crosman said to send them my shipping address and they will send me a return label, so tomorrow it will be sent out as soon as I get the return label.
Click to expand...

That curve just sounds like you didn't have enough hammer preload. When it came off reg at 2K, it now had enough energy to open the poppet further. But you reported same, just higher velocity in first post, where I assume you had more preload. More hammer energy should have leveled it out. So, trip to crosman is warranted. ;)

If the vertical stringing was in one of the peak areas, make sense. 


 
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Yes they did a repair and return, there warranty is great and they did it in a timely fashion. I started over again sighting in, and had some black birds get in my way witch with my farthest kill was 65 yards. I did shoot at one 102 yards out, I saw the pellet fly just to the right of it so I shot again just took off a couple feathers. I am having so much fun with this gun. I just wish pellets would be easier to get ahold of.
 
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