Hi all. After 10 years of use, the spring in my R9 finally broke and needed to be replaced. Since I had good luck installing a Vortek kit in my TX200HC last year, I decided to go that route again. On disassembly, I found that not only had the spring broken about 2 inches from the back end, but the front end of the spring had caught one of the fingers at the front end of the thin inner piston sleeve and pushed it through the cocking slot. Not a great design in my opinion. There was also lots of lube everywhere, including forward of the piston seal. That probably explains why I could still catch a whiff of burnt oil with every shot, even after 10 years of shooting. This gun really needed to be serviced.
After cleaning up all the lube, I noticed that the cocking slot in the piston was very rough and irregular. I smoothed off the major bumps and inner edges with a couple diamond files, then polished the same areas with a little emery paper. After fitting the new seal to the piston, I applied the supplied synthetic grease to the spring and guides, and coated the OD of the piston and seal with moly paste, also obtained from Vortek. Everything went smoothly until it came time to install the piston assembly in the compression tube. The R9 has multiple openings at the rear of the compression tube, and the Vortek seal caught on the forward edge of each one of these as I tried to slide the piston into place. The square openings for the little retention plugs gave me the biggest problem. I tried to reach through the openings and ease the seal past the openings, but was only partially successful at this. There must be a better way. If I do this again, I will try to smooth those forward edges in the various openings to make piston installation easier. In the end, only minor damage was done to the leading edge of the seal, and performance didn't seem to suffer much, if at all.
Reassembly went fairly smoothly, except for the usual problems maneuvering the pivot washers and bolt into position. This took a couple tries. I also had to install a new style cocking shoe since the metal inner piston sleeve is removed and replaced by the Vortek delrin equivalent.
Chronograph testing gave an average velocity of 807 fps with JSB Express pellets, for a muzzle energy of 11.4 fpe. This is right where I hoped to be. Then it was time for accuracy testing.
Here is my outdoor range:
Here is my setup:
And here are the groups:
As you can see, groups at 25 yards are running about 0.5 inches. I was probably able to get groups about the same size before the tune, but not with the same consistency of size and placement. The gun was easy to sight in, with very predicable tracking of scope adjustments. And once sighted in, the groups didn't move around at all. This is a big improvement over what I was getting with the stock spring and guides. After a little practice, I was getting similar groups from sitting position with sticks, with only a small shift down in POI. Sitting accuracy was good enough to allow me to hit my 3/4" spinner every time at 25 yards. All in all very successful, and definitely worth the money and effort.
You may notice that my rifle has a shortened barrel. This is because I decided to lop 4' off the front in an attempt to shorten shot time and improve my accuracy when shooting offhand. I think it did help a bit, but didn't turn me into an Olympic class shooter. Of course this also removed the choked portion of the barrel. If anything, accuracy improved after removing the choke. It certainly didn't get any worse. Your results may vary.
Chuck
After cleaning up all the lube, I noticed that the cocking slot in the piston was very rough and irregular. I smoothed off the major bumps and inner edges with a couple diamond files, then polished the same areas with a little emery paper. After fitting the new seal to the piston, I applied the supplied synthetic grease to the spring and guides, and coated the OD of the piston and seal with moly paste, also obtained from Vortek. Everything went smoothly until it came time to install the piston assembly in the compression tube. The R9 has multiple openings at the rear of the compression tube, and the Vortek seal caught on the forward edge of each one of these as I tried to slide the piston into place. The square openings for the little retention plugs gave me the biggest problem. I tried to reach through the openings and ease the seal past the openings, but was only partially successful at this. There must be a better way. If I do this again, I will try to smooth those forward edges in the various openings to make piston installation easier. In the end, only minor damage was done to the leading edge of the seal, and performance didn't seem to suffer much, if at all.
Reassembly went fairly smoothly, except for the usual problems maneuvering the pivot washers and bolt into position. This took a couple tries. I also had to install a new style cocking shoe since the metal inner piston sleeve is removed and replaced by the Vortek delrin equivalent.
Chronograph testing gave an average velocity of 807 fps with JSB Express pellets, for a muzzle energy of 11.4 fpe. This is right where I hoped to be. Then it was time for accuracy testing.
Here is my outdoor range:
Here is my setup:
And here are the groups:
As you can see, groups at 25 yards are running about 0.5 inches. I was probably able to get groups about the same size before the tune, but not with the same consistency of size and placement. The gun was easy to sight in, with very predicable tracking of scope adjustments. And once sighted in, the groups didn't move around at all. This is a big improvement over what I was getting with the stock spring and guides. After a little practice, I was getting similar groups from sitting position with sticks, with only a small shift down in POI. Sitting accuracy was good enough to allow me to hit my 3/4" spinner every time at 25 yards. All in all very successful, and definitely worth the money and effort.
You may notice that my rifle has a shortened barrel. This is because I decided to lop 4' off the front in an attempt to shorten shot time and improve my accuracy when shooting offhand. I think it did help a bit, but didn't turn me into an Olympic class shooter. Of course this also removed the choked portion of the barrel. If anything, accuracy improved after removing the choke. It certainly didn't get any worse. Your results may vary.
Chuck
