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Tuning PP750 Power Tune with guage block

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Hawkeye51

Hawkeye51

Member
Mar 3, 2018
160
26
Missouri, United States
Has anyone installed an extended guage block with larger plume? I bought one from Wes @ Airgunarcheryfun in Canada, but haven't put it on yet. I have 2 direct fit moderators from Geo that are outstanding, (3" & 6.5") but must sit infront of the air reservoir due to their diameter. This means that I will need to lengthen the shroud about an inch. The best (cheap) option I can come up with is to cut the shroud in half, pull it apart an inch, and wrap it with a carbon fiber tube. This would keep the threads intact. Any other ideas out there that I'm missing? What's the best way to cut carbon fiber? Can I sand the ends to clean them up? Best glue, etc.... 

What's the consensus on turning the transfer port into a larger single hole & filling in the groove and second hole? Will I gain any efficiency or other benefits, sound etc? Looking for 800 fps with Crosman domes for a flat trajectory.

Last question. Has anyone else experienced cracking of the clear plates on their magazines? I bought 2 initially and 2 more months later and all 4 have cracks. Appreciate any input, I really love this little gun and it has quickly become my favorite.

I'll keep you posted as this project progresses, with some pics. 
 
Not sure of the design at the transfer port on THAT SPECIFIC GUN, but a single larger transfer port has been a problem on SOME SPA rifles. I have a (now) great shooting M10 SPA in .22 that would originally shave lead off the pellets due to the head dropping just enough into the large transfer port to catch on the opposite side. Accuracy in that as new state was poor. I had to remove the fitting and reshape the breech side of the transfer port to eliminate that particular problem. Worked out great but it was pretty hard to do in the small space available. My general recommendation would be to tread lightly and evaluate thoroughly to avoid possibly creating a problem.
 
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Thanks Mike

I ordered a 22mmx24mm carbon fiber tube through Ama$on, and a month later I'm still waiting on it. Looking to buy a pp750 in 177 cal. If I can get one, I will use the CARM 14 shot mags and try to tune it to 880 with 10gr. ammo. I'll use the guage block for that build if I find a gun. Right now my 22 cal is running @ 680 with Crosman domes without an extended plenum. If I can't find a 177, I'll throw it on my 22 cal. 

Keep me posted on your tune, I'm very interested. 
 
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I finally installed the guage block with extended plenum. I thought the regulator was set to about 120 bar pre installation, by watching the velocity drop when the air reservoir guage got down to 120 bar. Without changing anything else the guage block was reading 150 bar after installation. Using Daisy 15.4 gr H.P. my speed went up about 40 fps without changing my hammer spring setting. I did install a lighter valve spring, but I'm uncertain how the regulator got bumped up.

Now getting around 750 fps with the Daisy 15.4 gr. Shot count is about 26. I've changed my mind on using a longer barrel even though it would increase my speed and probably utilize the plenum to a fuller extent. Any ideas on why the guage block reads 150 bar without changing the regulator? When the gun drops off the reg. the two guages read the same. 
 
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