Sort of copy of Daisy 747

[JPSAXNC]

There seemed to be a disconnect between the pump effort and performance of my Daisy 747 even when it was shooting at factory spec. So I'm building a sort of copy from various parts from other projects. I had a 2240 grip frame, a barrel and steel breech from a 1317 a set of burled cherry grip panels, and one of the unused valves from my SSP rifle project. All these parts had to be modified for this project. I used a 1" tube with a.049 wall .902 id. I had to make a pump arm, link arm, link, piston rod, piston, end caps, and bushings for the pump arm. The grip frame was modified to fit the grip panels that were made for a smaller version of the frame, plus I had to modify the frame for an extended sear because instead of aligning the back of the grip frame with the end of the tube like on a stock gun, I shifted the grip frame forward by .650 to get a better balance. The valve had to be turned down from 1.031 to fit the .902 id. of the new tube. The barrel had to be shortened, I had a bolt that fit the steel breech but I wanted to make a flow through bolt to keep the lost volume as small as possible. I should be able to test it in a day or so, there's a few things left to finish up.

[AmBraCol]

Sounds interesting indeed.  I'm a sucker for single stroke pneumatic pistols.

[Rob M]

Hi James , sounds interesting . send me pics if you have trouble posting them.. the email starts with rm

[JPSAXNC]

Thanks Rob, Maybe I can take some pic's tomorrow. I'm still working the bugs out almost done. I didn't have any drawings to go buy just some measurements from the stock gun. Right now the swept volume is 2.393, I can get a little more by extending the slot in the pump arm slightly. My valve leaks a little it's been knocking around in my tool box for years, I think it needs the seal face cleaned up. The firing chamber volume is a little less than the .028 cu. in. of the original valve. I did pump the gun the closing force on the lever I guess to be 35-40 lbs.

[JPSAXNC]

I'm still working out issues fitting the parts together, since they were all made in different setups . I have to make a new valve it has several leaks, I had to solder in plugs for the passages and then recut them but it didn't work. I will make the new valve out of 7075 aluminum so it's lighter and the seal seat should be hard enough since there's repeat hammering of the poppet.

[Rob M]

Are you using the hammer bleed method to grab more air? That worked best on my sidelever build

[JPSAXNC]

Hi Rob, I don't know what the hammer bleed method is could you explain it?  I just started making the new valve, this should be the last part, to firing.

[Rob M]

what you told me to do with my sidelever ssp , let the hammer rest on the valve stem so the piston can pick up new air after the shot. ( as opposed to cocking the gun to where the piston oring reaches the slot or bleed hole )

[JPSAXNC]

Yes, the hammer holds the valve open slightly. I made the pump arm slot shorter so I could gain a little stroke length, to do that I had to machine the link arm so the side near the slot had a very shallow V shape to clear the slot.

[JPSAXNC]

Well it works, not what I had hope for though. Pump effort measured 28 lbs. on a bathroom scale. 7.9 grain cpl's shoot 445-447 fps.

[Rob M]

Well it works, not what I had hope for though. Pump effort measured 28 lbs. on a bathroom scale. 7.9 grain cpl's shoot 445-447 fps.

thats pretty good , similar specs to the izh46, and those are quite efficient ,, send pics when you can

[JPSAXNC]

Hi Rob, I was able to get steve in nc 46m shooting the 7.9 grain cpl's at 490 fps. That's what I was hoping for. It might still be doable, the valve porting I was using was for my ssp rifle with 7 cu. in. of swept volume, the porting worked great for that volume of air. But the swept volume of the pistol is only 1/3 of that so I'm making another valve with smaller porting hoping that will keep the pressure higher longer, kind of like the difference between huffing into a blow gun or forming your lips into a transfer port, same volume of air expended with the same force but a big difference in performance. Keeping my fingers crossed. I will get pic's at some point I just want to try one more thing.

[ray1377]

Mr. James
I hope you get some pictures up soon. I'm a sucker for SSP airguns

Ray

[Rob M]

PICS FROM JAMES
DSCF0733 by murphyrobert9, on Flickr

DSCF0732 by murphyrobert9, on Flickr

DSCF0730 by murphyrobert9, on Flickr

DSCF0731 by murphyrobert9, on Flickr

DSCF0728 by murphyrobert9, on Flickr

more to come SOON

[Rob M]

DSCF0736 by murphyrobert9, on Flickr

DSCF0734 by murphyrobert9, on Flickr

[Rob M]

DSCF0741 by murphyrobert9, on Flickr

DSCF0737 by murphyrobert9, on Flickr

DSCF0738 by murphyrobert9, on Flickr

DSCF0742 by murphyrobert9, on Flickr

DSCF0740 by murphyrobert9, on Flickr

[Rob M]

DSCF0743 by murphyrobert9, on Flickr


DSCF0739 by murphyrobert9, on Flickr

[Rob M]

James , very nice result.  Love the sidelever , very slick looking . cant tell if the breech was taken from something else or if you made it . cool either way, I like the fact it came out smaller than the 717.

[JPSAXNC]

Thanks for posting the pic's. Yes, it's a little shorter than the 747 and about 7/10 of a pound lighter. The barrel length is the same 9 3/8" from the transfer port to muzzle. So I made a valve with a smaller valve throat and smaller transfer port but it's to restrictive and the power was down, I'll open it back up a little and see what happens.

[JPSAXNC]

I had made the cocking slot a little shorter than stock so I could gain a little more stroke length but I couldn't get more because the slot in the pump arm wasn't long enough. So I lengthened the slot and can get 450 fps. with the cpl's with 23 lbs. of closing force on the pump lever. I'll shoot it like this for a while, and latter on increase the preload on the pump arm. I'm going to make a front sight for it, I have one for the rear.