All Springer/NP/PCP Air Gun Discussion General > Machine Shop Talk & AG Parts Machining

Sort of copy of Daisy 747

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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.

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

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.

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.


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