Upgrading an older Marauder to work like the Field and Target gun

[Saltlake58]

still working on the tune. Tried 1800 PSI and 2000 PSI on the regulator. Goal is 830fps with JSB 18 grain pellets. However, the 2000 PSI wastes much more air, with shot count dropping from 50 to 35. will return to 1800 psi and recheck. Looks like the sweet spot will be a touch over 1800 psi, 

I think I'll bite the bullet and pick up the Hill 20 gram hammer. It looks like the precision of hit requires a lighter hammer, and matched spring.

It's been interesting. My Impact is ready to shoot, but lately, I've been tinkering with the Marauder so much that the Impact just sits. I'll get back to it, but for now, tinkering and learning about the relationship between air pressure behind the valve, regulators, transfer port sizes, and more. It's all a balancing act that takes time to get working. I don't think there's a single right way, just a million ways to balance it all to get something close to what you want.

 

[Saltlake58]

I think I've finally hit the sweet spot. Here's the setup.

Regulator set at about 2000 PSI, Hill HF Transfer Port, Hill Valve Spring, Hill 262 hammer spring, Hill 20 Gram Hammer with Hill striker. Transfer Port set at 5 or 6 for full flow.

With this setup, and the Hammer Spring adjustment at Zero, the Crosman 14.3 Dome's hit 840 to 850. With about 1/8 turn, the JSB 15.89's run right at 830 fps. With hammer spring at 1 rotation, the JSB 18.13 grain hit about 830.

Went to the range today on my lunch hour. Windy, gusting up to 30 mph, but the range is fairly well protected with berms. Still, I could tell when the wind gusted. Airport was under high wind aviation warning, and it's only a couple miles away. Not best for shooting groups. Here are a few 50 yard groups with the JSB 18.13's:

First group, 9 shots through one hole with one outlier. I think the wind died, so far pretty good. With the flier, about 9/10 of an inch. Without the flier, a touch under 1/2 inch.

This group wasn't quite as good but the next best for the day:

I think it 6 in the left hole and 4 in the right hole. Wind was very bad and inconsistent. And to be honest, I may have pulled a couple of them.

All in all, very happy with this setup!

Oh, best part, gun is quieter than ever before and a touch over 60 shots per fill.

Mr. Holland, I thank you for the help and support through this. Your advice was spot on!

I may be posting more groups later, but that's after the wind and rain dies down a bit.

 

[Xbowsniper]

Saltlake,

Really glad it worked out the way you needed it to. Glad to help!!!

Now I'm ripping mine apart, as I THOUGHT I had a Lane regulator in it, I had one of those "other" brands. Swapped it out, started at 1100 psi, and deemed it too low. Tomorrow, I'm going to Jack it up to around 1300 or so, and see where the velocity is. I'm getting 760 fps, which is just a touch short of my goal. If, by upping the reg pressure, I still get the same velocity, I'll have to install a heavier hammer spring. My valve is fixed, no transfer port adjustment, and my transfer bushing is as large as it can be. So, the only thing that I can adjust, is the spring, and the regulator. This takes all the guesswork out of the equation, plus, fewer adjustments to back off and come loose. I'll keep ya posted. 

Glad it worked out, those groups looked healthy, particularly in that heavy of a wind at 50 yards.

Thanks again 

Tom Holland 

Field Target Tech 

 

[Saltlake58]

Oh, and I have a correction. The last two groups of the day were 5 shot groups, not 10 shot groups. The first group with 1/2 inch is only 4 shots. Still, I'll take it!

Good luck in the next tourney, shoot straight!

 

[Saltlake58]

Oh, and another question. What did you drill your transfer port out to?

 

[Xbowsniper]

Saltlake,

I don't remember offhand, but I drilled it out as big as it could get, and still have a tiny bit of the wall left on the ends.....I think I used a 5/32" drill chucked in my tail stock on the lathe, and put the transfer port in the lathe chuck itself.

Tom Holland 

Field Target Tech 

 

[Saltlake58]

maybe after shooting for a while, I'll drill out a port, but for now, I'll just shoot!

many thanks

 

[Xbowsniper]

Saltlake,

Another accuracy enhancer, in my eyes, is removing the shroud. I don't remember if I mentioned that previously. If you are not hunting with the gun, and noise is not a factor, and want no shift due to temperature, get rid of the shroud. Here's a test to determine if you'll get a temperature shift.

Shoot a 5-10 shot group at 30 yards. Remove the shroud. Shoot another 5-10 shot group, aiming at the same spot. If the group moves substantially, (more than 1 inch), if you have a temperature change, or you are in the sun for an extended period of time, your groups with the shroud installed will "wander". I remove my shroud completely to eliminate any shift. If, you take the shroud off, and the group moves, the barrel is being torqued by the shroud. I've taken the shroud off, and installed a piece of HDPE plastic weight, and now I now can tune the barrel for the best group by adjusting the harmonics of the barrel.

Good luck, happy shooting, tomorrow is another testing day......

Tom Holland 

Field Target Tech 

 

[Drumsnguns]

Xbowsniper, (Tom), Would you mind if I messaged you and ask about my .25 cal Marauder? I don't want to hijack this thread with larger calibers. 

Thanks,

KP

 

[Xbowsniper]

KP,

Of course, sure no problem. I don't have a lot of experience with the .25 Marauder (I even have a stock untouched one) , but I can steer you in the right direction.

Tom Holland 

Field Target Tech