made an adjustable piston for the 880

[Rob M]

and now that you did this experiment, you see what I mean about no one understanding pumpers. Ask anyone about a 1 inch pumper and they will automatically say " the effort to pump it would make it useless".. OR , " a pumper could never push 25 cal at pcp speeds"/// All bs misconceptions and wives tales that have been proven wrong by the best of builders like Bob sterne, James perotti, LD, Phil Riggs, and very few others.

[bhh]

I think part of the problem is that there is more money in selling many cheap guns than there would be in selling a few quality guns with a heavy-duty parts.

[Rob M]

yep.. theyre making the springers and walmart pumpers for pennies on the dollar.. theyd need to sell a lot of 25 cal pumpers to be worth it..

[avator]

Nothing like having a "one off" like you have there. Something you did. And I'm sure you gained a ton of knowledge along the way. I bet it answered a lot of questions for other tinkerers too. Thanks for sharing it. 700 fps at 6 pumps ? Yeah, I'm in for that.. another 6 pumps for another 200 fps?  I'll probably go in the house and grab another gun.

[cobalt327]

I think part of the problem is that there is more money in selling many cheap guns than there would be in selling a few quality guns with a heavy-duty parts.

I agree it's probably not a viable option for the big manufacturers, but this is how guys have made a cottage industry of reworking lesser airguns into improved versions. I don't know if enough folks would buy the parts to modify this gun or not, but it's a cool exercise! This is reminiscent of my having modified Daisy spring air lever guns (details over at THR in the Air Guns forum under "Putting a little more power in a cheap Daisy" or something like that). In my case, the plunger tube was (is) the weak link. Making a stiffer one is, at least for now, beyond my capabilities so I stalled at 350 fps on a ~250 fps baseline. I decided there was not enough interest in hotrodding a Red Ryder to warrant pursuing better parts, but in this case who knows?

[bhh]

Nothing like having a "one off" like you have there. Something you did. And I'm sure you gained a ton of knowledge along the way. I bet it answered a lot of questions for other tinkerers too. Thanks for sharing it. 700 fps at 6 pumps ? Yeah, I'm in for that.. another 6 pumps for another 200 fps?  I'll probably go in the house and grab another gun.

Thanks, it's more about learning and tinkering than actually having a nice powerful gun. I agree that past 6 or 7 pumps it's not really worth the extra effort, but, the goal of this large tube project was reducing pumps rather than searching for absolute power. Still, I may enlarge the valve a little and see what happens. It sure is hard to resist those "Whatifs" when they crawl inside my head. 

Anyway, just to put this in perspective, here are the stock numbers vs the modified:

Stock                   Modified
10 = 650 fps         5 = 660
15 = 700 fps         6 = 698
20 = 750 fps         8 = 750

I didn't make it to 12 fpe, but I cut the number of pumps in half. With a metal pump arm I think it could reliably handle 8 pumps over the long haul.

[Rob M]

very nice.. once u stiffen all the moving parts and such, i dont see why you cannot get 900 fps on pump 12

[avator]

Nothing like having a "one off" like you have there. Something you did. And I'm sure you gained a ton of knowledge along the way. I bet it answered a lot of questions for other tinkerers too. Thanks for sharing it. 700 fps at 6 pumps ? Yeah, I'm in for that.. another 6 pumps for another 200 fps?  I'll probably go in the house and grab another gun.

Thanks, it's more about learning and tinkering than actually having a nice powerful gun. I agree that past 6 or 7 pumps it's not really worth the extra effort, but, the goal of this large tube project was reducing pumps rather than searching for absolute power. Still, I may enlarge the valve a little and see what happens. It sure is hard to resist those "Whatifs" when they crawl inside my head. 

Anyway, just to put this in perspective, here are the stock numbers vs the modified:

Stock                   Modified
10 = 650 fps         5 = 660
15 = 700 fps         6 = 698
20 = 750 fps         8 = 750

I didn't make it to 12 fpe, but I cut the number of pumps in half. With a metal pump arm I think it could reliably handle 8 pumps over the long haul.

Oh yes, I am absolutely all for more power with less pumps. betty Lou and I have a matching set of Metal/Metal 880s now. We shoot paper flys at 10 meters with 4 pumps and paintballs and beer cans at 5 - 6 pumps. Between us it is not uncommon to burn a tin of 500 winnies in an evening. Even at 1 pump less per shot, that is huge.

[bhh]

A mod like this would be perfect for that type of shooting, but I'm not sure the tube would fit under the metal clamshells. I'm going to have to get the heat gun out and make a bulge in the plastic ones I'm using.

Tonight I used washers and made the piston rigid. Nothing changed. I adjusted it so the head space was as close to nothing as I could get without a hard snap shut. I erred on the side of longevity and lost less than 10 fps.

Then I tried the 9.7 gr Winnie domes:

1 = 292
2 = 417
3 = 497
4 = 551
5 = 602
6 = 634
7 = 658
8 = 691
9 = 708
10 = 724
11 = 733

10.3 fpe in 8 pumps.
11.3 fpe in 10 pumps. Not bad.

[avator]

I meant to say we shoot the paint balls and beer cans off of 3" drywall screws with 5 - 6 pumps at 25 - 30 meters.

[Rob M]

if you dont want the slapping noise, you may want to add a rubber piece of inner tube or something similar to the piston face.. This will also aid in headspace.

[bhh]

if you dont want the slapping noise, you may want to add a rubber piece of inner tube or something similar to the piston face.. This will also aid in headspace.

It wasn't the noise, it was stress caused by an interference fit between the piston and valve. I have them very lightly touching when the pump handle closes. In the past when I had the hard fit it caused things to wear and break.

[dv8eod]

I meant to say we shoot the paint balls and beer cans off of 3" drywall screws with 5 - 6 pumps at 25 - 30 meters.

Are you sure you're not just looking for an excuse to brag? Seriously though, going with the posted stock numbers, that is alot of pumping.
 I just read this whole thread today and am trying to figure how all this information can be applied to my 1377. Not being the sharpest tool in the shed, all I've managed is to get an oring around the pump cup. I haven't figured out where I'm supposed to shim or what to pin. I hit the mark I wanted with Davio's help and parts, but now I kinda want to go a little further.

[avator]

  If it were my intent to brag I would have to brag on Betty Lou. She still out shoots me 2 to 1. 

[dv8eod]

If it were my intent to brag I would have to brag on Betty Lou. She still out shoots me 2 to 1. 

  I understand, Sir.

[Rob M]

if you dont want the slapping noise, you may want to add a rubber piece of inner tube or something similar to the piston face.. This will also aid in headspace.

It wasn't the noise, it was stress caused by an interference fit between the piston and valve. I have them very lightly touching when the pump handle closes. In the past when I had the hard fit it caused things to wear and break.

well it really goes to show when your pushing that much power how everything needs to be rigid and with a certain tolerance.. Just like we discussed in regard to my 1 inch pumper.. I quickly realized i could never push the platform with the stuff I had.. But , at 6 pumps and 700 fps , i guess you dont need to push this platform to the max ( but ID prefer if ya did lol, just to hit 911 fps

[Rob M]

ALSo, it looks like with 10.3s or heavier you will hit 12 fpe at 12 pumps..

[bhh]

I quickly realized i could never push the platform with the stuff I had..

Exactly. That's why I backed off a touch.

But , at 6 pumps and 700 fps , i guess you dont need to push this platform to the max ( but ID prefer if ya did lol, just to hit 911 fps

Yea, I'm going to open up the valve a little this weekend. I seem to remember some threads around here about taking a dremel to the valve.

So, I just tried 12 pumps:

9.7 Win Dome = 744 and 11.93 fpe.
10.66 H&N Barracuda = 722 and 12.34 fpe 

[Rob M]

PULLING my chain man

[Rob M]

howd u get the extra 150 fps from the last post??