I finally got around to tuning my Crosman G1. I ordered the E3650 spring and small Apex piston seal. When I tore it apart I was surprised to see that after approx. 1000 shots the original spring was still in great shape. Nice and straight with no kinks. The piston had some wear/rubbing marks on the tail opposite the cocking slot and on the right side of the slot. The piston seal had a couple very small nicks. The edge of the seal where it contacts the compression tube walls felt like it was ridged, like the side of a quarter. Is this normal for Crosman Seals?
I debured and polished all the slots, the inside/outside of the piston, the tophat and spring guide, and the inside of the receiver tube. The compression area appeared highly polished, so I crosshatched it some with 400 grit paper. I smoothed the E3650 spring ends some with a dremel, being careful not to nick the end coils.
The air transfer port in the end of the compression tube had a sliver of metal extending over part of it. I inserted the tapered round handle of my file into the port from the outside and pushed the metal up out of the way of the port. Then I glued some 320 grit sandpaper to the end of a dowel and sanded the face of the compression tube. I had to repeat this process until all of the metal sliver was gone and the port was unobstructed. It looked like a small shaving of metal must have been in the compression area and then pounded into the metal at the end of the tube through repeating firings.
I molyed everything as suggested by the pros here and tarred the spring sparingly. I then started the assembly. The new seal seemed really tight. I went slow, pushing the seal down to pass under the openings. It took quite a bit of effort getting the piston in.
I buttoned everything up and went to do some shooting. Cocking was pretty smooth. The shot cycle was smooth and very quiet, just a thud! But my G1 didn’t seem nearly as powerful as it was before the tear down. I shot maybe 50 rounds before I decided it needed another teardown.
This time when I got it opened up, the piston was extremely difficult to get out. I had to carefully use a dowel in the piston cocking slot and tap the dowel with a hammer to get it out. No wonder it didn’t have any power. I wonder why it wasn’t harder to cock?
It was obvious the seal was too large, and I found a small nick. Not sure if it happened on the assembly or dis-assembly. I wedged the seal onto a dremel bit and carefully removed material with a small file and various grits of sandpaper until it fit tight but not too tight. The bonus was that the nick was gone after removing the excess material to make it fit.
This time after looking again at the wear marks on the piston I decided to button the piston. I used a method I found on another forum involving super glue and soda bottle material. I placed one button opposite the cocking slot at the end of the piston, and two more on either side of the cocking slot (2,6,9 o’clock positions). Then after it dried for several hours I sanded them smooth for an almost tight fit.
I also found out why the cocking was still a little stiff. The articulated linkage was stiff at the joint where two outer arm pieces were pressing against the pin and two inner arm pieces. I pried the outer arms apart a little and inserted a thin strip of soda bottle material. It made all the difference, now the linkage moves very easily at the joint.
I buttoned everything up again. The next day when I went shooting I was very happy with the results. The G1 now cocks smooth, shoots smooth and quietly, and seems to be much more powerful than it was before I started the tune (sorry, no access to a chrony). No dieseling at all either. I have 400 shots through it now, and if anything its getting even smoother.
The target pictures are the best groups of 5 shots of Crosman HP's during my shooting of shots 350 to 400. The targets are 2.5 inch circles with a 1/2 inch bull. All shots are at 20yrds. They aren’t the best groups but I was shooting with a 10-15mph wind that kept changing directions. Of course that’s pretty normal here in North Dakota, the wind seems to always be blowing.
