Lets just say I suck at math (numbers in general)

[jdanvers]

. . . dinking with an on again / off again m-rod 'project' gun. I had a custom aluminum tube made up for it (jsar) in a 26" length - standard is 24". I figured the extra 2" would give me a little extra air / compensate for the added space that a huma reg occupies in there. As I wrote that <-- back there it just hit me that yeah - I may in fact not be getting any additional air in the tube - the extra length may just be making up for the space that the huma is taking up. (y/n?) (( It's the huma w/the pressure gauge for a gen ii tube. ))

So the question is: if a stock m-rod tube is 215cc in volume, can I assume this one I'm now using is (more or less) roughly the same?

This question segues into this -- efficiency calculation? I just googled a little bit and found this one. Any other good ones that you guys know of / use? I'm real happy with accuracy and performance of the gun @present -- I'm getting solid mid 880's out of it consistently running AA 10.3's. I'm not entirely happy with the efficiency, or lack thereof, with it though - starting with a full 3000psi it drops to near 2000psi after just 30 shots (3 10rd magazines). I haven't run it down beyond that as I've been topping it off with my hand pump - trying to avoid using my tank - lol - not sure how long will be able to keep hitting the scuba shop to get that topped off. Fortunately it's a pretty easy gun to hand pump.

 

[mmahoney]

This is the one I use:

http://www.calc.sikes.us/1/

 

[Yo]

Something just doesn't sound right even when compared to an oem Crosman tube. I would think you should at least be getting 50 good shots with a Huma. Isn't aluminum thicker than steel? Would it be reasonable to assume you have less volume but you got the Huma reg in it was it tighter fitting? Hmmm... may need some tweaking on your tune... What pressure is your reg set at? YO!

 

[Saltlake58]

OK, my experience with adding a regulator to a Marauder - it took a lot of adjusting, tinkering, and playing. before regulator, 32 shots before velocity dropped. It's a .22.

After regulator, 30 shots, a net decrease in shot count. I played with it and played with it. Finally arrived at a compromise of settings to drive a 18 grain JSB pellet at about 830fps, and I get 50 shots per fill.

So, you may indeed have extra air capacity, but the settings are incredibly important. I ended up changing the hammer spring, getting a lighter hammer, and installing a different transfer port. With a Marauder, a regulator alone probably won't change your efficiency, though will give consistent speeds.

 

[jdanvers]

Oh wow ( lol ) I kinda forgot about this post / question. @Saltlake58 - agreed - it's definitely consistent speed. And agreed on continually fiddling with it. I'm pretty sure I need to ( one of these days ) pull the huma back up to the top of the tube again and lower the reg pressure - I'm thinking it's still a little to high which is contributing to less than stellar efficiency in the shot count dept. I just got a new Taipan Veteran .22 and, well, the m-rod has taken a back seat and been sitting idle for a bit . . . lol

@Yo - believe it or not the specs on the aluminum tube are identical to the crosman OEM steel one. Wall thickness, inside diameter, etc . . . . same thing - WAY less weight.

It's been a while since the last time I was in that tube . . . thinking the current reg pressure is around 105 - 110 - somewhere in that neighborhood. If and when I get back into fiddling with it again I may drop it down to 95-100 and have another go at it.