Tuesday, June 25, 2013

Crosman 707 disassembled

I fully intended to shoot the 707 for a while before I tore it apart. That didn't happen.....

I shot the rest of the CO2 in the cartridge that was in it, then reduced the 707 to its greatest number of parts. One of the reasons for the tear down was that I wanted to clean the barrel. It is hard to clean the barrel on a tap loader. Before I tore it down I tried to run a patch through the barrel with a cleaning rod. I thought the patch would stay on the jag and I could pull it out. That wasn't the case, the patch came off the jag and stayed in the tap. Luckily I was able to fire the gun and shoot the patch out. 
I'm glad I tore it down, it was pretty dirty inside.

The end of the valve had a heavy coat of rust on it.

The inside of the tube was dirty and rusty also, a couple passes with a shop towel soaked with Marvel Mystery oil and the tube is looking much better.

I was curious about how the valve worked. To cock the rifle you push the bolt forward, when fired the bolt moves to the rear.... The opposite of the way all my pumpers and CO2 rifles work.
The mystery was solved once I opened it up. The valve sits behind and in line with the barrel. The transfer port is also the hammer to open the valve. When you cock the gun the hammer spring is compressed, when the sear releases the hammer it slides rearward into the valve, opening the valve and allowing a charge of CO2 to travel through the transfer port/ hammer into the tap and push the pellet down the barrel. Pretty cool! I have been trying to figure out how to make an inline valve for my next build, now I have some ideas.



In case it isn't clear in the pictures above, the transfer port/ hammer is hollow. The end that goes into the valve is pointed and has three holes drilled in it to allow the gas to travel through it.

The valve is pretty simple inside, a screen and washers, with a spring to hold the valve against its seat, all held in with a snap ring.


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