GTA
All Springer/NP/PCP Air Gun Discussion General => Machine Shop Talk & AG Parts Machining => Topic started by: Duane38 on October 20, 2022, 07:33:08 PM
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Gang, here are a few pics of the .357.big bore pumper project. Did some testing today and found myself to be pleased with the preliminary numbers so far. I may fiddle with transfer port sizes to see what is best. Right now, the TP is .25". Here are the numbers using 81 grain JSB:
10 pumps, average of 404fps - 29.3 ft/lbs
15 pumps, average of 496fps - 44.2 ft/lbs
20 pumps, average of 606fps - 66 ft/lbs
25 pumps max, average of 695fps - 86.8 ft/lbs
Valve volume final measurement is .65 cu.in. Each stroke is 5.3 cu.in. barrel volume is 1.95cu.in.
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Uploading not worthy here...
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Muzzles...
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Doh...
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Lever....
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Excellent work Phil , this may be the first 9mm pumper ever made, and 86 fpe is nothing to sneeze at. Judging by the sidelever, its probably quite easy to pump
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Thanks, Rob. It IS easy to pump. Pretty decent MA on the lever.
The pump tube is .992" bore. Stroke of the piston is 6.75" on this build. Pretty traditional piston/lever assembly. Like a scaled up Benji.
Wondering if a longer barrel alone will boost velocity. It's at 20" length now. Maybe 22-24 would boost it. Then again, the valve volume at .65cu.in, maybe not. Volume was larger, but did the redesign using an inner chamber for atmosphere for the poppett.
I'll get all the steel parts a bluing job and send off the aluminum for anodizing.
As you can probably see, it sports an M-rod trigger. Had to redesign a new sear to work for this particular application. Other than that, stock. Have a stock, too. Though, it's going to require modification since the M-rod air tube is 1.25" OD. The plan is the glue a 1.125" OD half round down in the inletting and re-route for the 1.125"OD pump tube. Take down some of the girth on the stock too. A bit chunky those M-rods are.
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It looks outstanding and with some decent numbers too!
Excellent work and thanks for taking us along for the ride.
Dave
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Any idea what pressure you are developing at 25 pumps?.... That is very impressive FPE in .35 cal, congratulations....
I spent some time looking back to 2015 to find the results for the .30 cal Millenniium Pumper, and it topped out at 78 FPE with the 44.8 gr. JSB's at 885 fps at about 2500 psi.... I think that was the most power from a pumper at that time....
Bob
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My best guess, theoretically, 25 pumps puts it right at 2,800 psi. The valve is .65cu.in. and each stroke is 5.10cu.in.
Did plan a manometer, but space was a concern. May still try by using a little longer inlet side. Though, stroke will be reduced a little. At least with a gauge, pump efficiency can be seen along with pressure.
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Awesome stuff-and impressive numbers!! :D
Looks great, fantastic work Duane 8)
Jesse
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Any idea what pressure you are developing at 25 pumps?.... That is very impressive FPE in .35 cal, congratulations....
I spent some time looking back to 2015 to find the results for the .30 cal Millenniium Pumper, and it topped out at 78 FPE with the 44.8 gr. JSB's at 885 fps at about 2500 psi.... I think that was the most power from a pumper at that time....
Bob
Bob, is that the Benji conversion that was done up? I seem to remember a Benji job a member posted on the Yellow a few years back. That is one of the builds which inspired this.
What is the valve volume and pump volume of that build?
Do you suspect my build could benefit from all longer barrel? Right now it's 20 inches. 19 inches of actual projectile path, of course, roughly. I know for certain air is still pushing pretty hard at 19 inches.
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The Millennium Pumper was a project I did in 2014.... I gave the design to CarsonRatSniper (Mike), who sold a limited production run of 10 rifles, lost money at it, and I think a few guys got hung out to dry.... I know I never got the gun I was supposed to.... My version had a 28cc reservoir/valve in a Disco tube (3/4" ID) and ran a Mac 1 Steroid Benji pump linkage with a swept volume of just over 50 cc.... It was a Retained Air Pumper (aka Air Conserving Pumper - ACP), designed to give several shots without repumping....
(https://hosting.photobucket.com/albums/oo221/rsterne/Millenium Pumper/.highres/IMG_2889_zpsc0710b62.jpg?width=undefined&height=undefined&fit=bounds) (https://hosting.photobucket.com/albums/oo221/rsterne/Millenium Pumper/.highres/IMG_2889_zpsc0710b62.jpg?width=1920&height=1080&fit=bounds)
Here are the various tunes in my original gun.... You had a choice of 1 shot at 50 FPE, 2 at 45, or 3 shots at 40 FPE (all with a backup), just by adjusting the hammer spring preload....
(https://hosting.photobucket.com/albums/oo221/rsterne/Millenium Pumper/.highres/MilleniumPumper1800Strings.jpg?width=undefined&height=undefined&fit=bounds) (https://hosting.photobucket.com/albums/oo221/rsterne/Millenium Pumper/.highres/MilleniumPumper1800Strings.jpg?width=1920&height=1080&fit=bounds)
Here is the pressure vs pumps data....
(https://hosting.photobucket.com/albums/oo221/rsterne/Millenium Pumper/.highres/MilleniumPumperPressure_zps12009273.jpg?width=undefined&height=undefined&fit=bounds) (https://hosting.photobucket.com/albums/oo221/rsterne/Millenium Pumper/.highres/MilleniumPumperPressure_zps12009273.jpg?width=1920&height=1080&fit=bounds)
Because of the high number of pumps to refill from empty, I fitted a Foster fitting to be used for the original fill if desired.... Mike increased the reservoir to 45 cc to give an extra shot or two, and had them available in .22 cal, .25 cal, or .30 cal.... That 78 FPE was for what amounted to a dump shot, or nearly, in .30 cal.... I think it gave 2 shots at about 65 FPE, but never found the data when I was looking last night....
You will definitely get more power with a longer barrel, particularly with a dump valve....
Bob
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Ah, yes. Now I remember. Of course. I was [mis] remembering or mixing up a creator who brazed up a Benji to shoot 30 cal (IIRC). A regular chap on the forums, but cannot remember his name, who also made several neat projects. Forgive me if you read this!
Looks like I'll be sourcing some more length of barrel, say, 24-26 inch length.
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Ah, yes. Now I remember. Of course. I was [mis] remembering or mixing up a creator who brazed up a Benji to shoot 30 cal (IIRC). A regular chap on the forums, but cannot remember his name, who also made several neat projects. Forgive me if you read this!
Looks like I'll be sourcing some more length of barrel, say, 24-26 inch length.
that was james perotti , hes still around here sometimes.He had a 32 cal benji , all modded, cant recall the numbers, something like 60fpe
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Philip,
If one looks how the power goes up with the number of pump strokes, your pump efficiency is impressive. Yes, the rest of the system is also working well, but the way the power builds per stroke would not be possible if your pump was less efficient.
Do you know what the peak pumping force is per stroke? If you could somehow measure the average force per stroke and the effective stroke length, then that would be a measure of your input energy.
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The pressure certainly builds and can be felt as one pumps it along. The last few pumps aren't difficult at all. Credit, the lever is the length of the tube. I've made a longer inlet side to accommodate a gauge. Just may put a gauge on it so pressure can be observed. The valve and piston are flat top and each component is using very hard o'rings to limit squish headspace. Of course, the pump tube was honed and polished too. Looks like glass in the inside! Unlike the .22 SSP I built, have not measured the effort on the pump handle. Though, it too has incredible efficiency. Right about 85 percent.
The valve porting is 5/16 with a very short, near direct path to the pellet. Rather than the air traveling along a 'C' shape path like conventional poppet designs, this is more like an inverted 'L' shape path. I'm sure flow is benefiting from this.
Just picked up a Bulldog barrel, too! Going to put that on to see what happens with the extra 8+ inches. In fact, the breech is all set up and ready to go in the lathe to take the barrel hole from .565" to .625. Set it up last night and dialed everything in. Project for today to get that barrel in.
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Forgot to add... The piston head is sleeved in Delrin. The piston head was machined down and a section of Delrin tube pressed on. Then, the assembly was final machined. The entire length is concentric to the tube and no metal components contact the walls of the tube. Pumps so, so smoothly. That alone reduces input effort as the lateral friction is nearly gone. Glides right along and quite satisfying.
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Welp. It's official. Had a brain fart! So not happy about that. Anyhow, stated the Bulldog barrel to be 5/8" diameter at the breech. Nope. More like an undersized 11/16"!
Had the breech all set up in the lathe running on a mandrel to keep the center line concentric. Machined a hole under 5/8", then finished the hole with a reamer. Took it all apart and.... That's when I realized that the barrel was NOT that size. Oops. Got it all set up AGAIN and now back at it. Ho hum.
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Mandrel...
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nice , very curious what the extra length will offer./ that bulldog barrel must be quite heavy ( you mentioned the new gauge , any news on actual pressure ?
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Yeah. Me too. There is certainly a significant air blast beyond the current barrel muzzle.
The current barrel is 20" at .68". I do have a scale and will check the weights. Good thought.
I still need to add the gauge. I can feel the efficiency in the pump handle. If one could say that. When pulling the handle back for the next stroke, the back pressure is almost non existent, more a vacuum when pulling the piston away from the valve.
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Bulldog barrel: 28.1 oz
Current barrel: 22.4 oz
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Got the Bulldog barrel on! Shot some strings. There are gains, but nothing super high. Three shots per string, then averaged.
Picked up a UTG 3-9x32 AO and illuminated to slap on when ready. The glass is actually crystal clear.
10 pumps, average of 458fps
15 pumps, average of 511fps
20 pumps, average of 628fps
25 pumps max, average of 709fps
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Philip,
What projectile did you use? A pellet or slug? How tight a fit, if a slug?
What does the chamber look like? It may benefit from a more gradual leade.
The whole bore may benefit from being lapped or polished.
Does the barrel have a choke?
Sorry for the inquisition. The point of the questions is to stimulate your thinking. Consider the questions rhetorical.
Considering the small air volume of compressed air, adding a few inches to the muzzle won't bring dramatic gains because the air pressure near the muzzle is not very high. If you made the valve body volume larger you could get more power, but you would always need more pump strokes to get the pressure up. If you made the body much larger and used this as an air conserving pumper, rather than a dump valve, you could get a lot of efficiency back.
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Philip,
What projectile did you use? A pellet or slug? How tight a fit, if a slug?
What does the chamber look like? It may benefit from a more gradual leade.
The whole bore may benefit from being lapped or polished.
Does the barrel have a choke?
Sorry for the inquisition. The point of the questions is to stimulate your thinking. Consider the questions rhetorical.
Considering the small air volume of compressed air, adding a few inches to the muzzle won't bring dramatic gains because the air pressure near the muzzle is not very high. If you made the valve body volume larger you could get more power, but you would always need more pump strokes to get the pressure up. If you made the body much larger and used this as an air conserving pumper, rather than a dump valve, you could get a lot of efficiency back.
82 grain JSB pellet was used.
The chamber I do believe has a very nice leade. The pellet loads fully into the lands. The hollow probe is long enough to seat all projectiles far enough.
The bore appears to be polished. It has a glassy reflection.
Choke? Probably not. Whatever the Benjamin Bulldog claims to have.
With the valve volume of .65cu.in @ 2500psi, say, the 20 inch barrel has 600+psi at the muzzle.
This project was intended to be an air conserving design with 1.5cu.in chamber and a foster fill nipple to pre-charge with a pump. However, the spring needed to pop the valve was silly stiff. Though, in hindsight, a balanced valve would solve that.
I may play around with valve ideas for this to make an air conserving pumper. As it sits now, I'm okay with it being a 90ft/lb pumper.
Gonna explode some rats with it. Heck, even with just 10 pumps, it's a monster.
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Philip,
It sounds like you could make that barrel even longer, if you have 600 PSI at the muzzle now.
Pellets and a shiny bore with a gentle lead sounds like a recipe for good power.
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Awesome results Phil, not too many 91 fpe pumpers out there ! Whats your current porting ( throat , tp)
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Not bad at all 8)
Excellent work!
Jesse
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Hi Phil,
You may remember me when airgun modders were exploring the limits of msp's on the old green.
I think you've got the record with 91 fpe. Well done.
Your valve volume of .65 vs bore volume of 2.0 suggests that a longer barrel will help (although you're in the sweet spot for the lower pumps), so I think you're on the right track to maximize fpe.
Keep on keeping on... it's nice to discover what is possible -
Wyo
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Hi Phil,
You may remember me when airgun modders were exploring the limits of msp's on the old green.
I think you've got the record with 91 fpe. Well done.
Your valve volume of .65 vs bore volume of 2.0 suggests that a longer barrel will help (although you're in the sweet spot for the lower pumps), so I think you're on the right track to maximize fpe.
Keep on keeping on... it's nice to discover what is possible -
Wyo
Hey, Wyo. Of course I remember! Nice to hear from the old crew.
The original 20 inch barrel is right on 2cu.in. As of last night, it has been fitted with a Bulldog barrel that's 28 inches long: 2.8cu.in
That would suggest if the valve is at 2500 psi, the muzzle pressure is still 500 psi or so! Can't imagine going longer! LOL. So, one could assume that a smaller valve would suffice in use with a shorter barrel. I'm thinking a pumper pistol project too.... Have enough pieces parts and stock in the bins...