Finished with the G1 tune/.22 cal conversion/ chrony numbers...

[Springer25]

First off I would like to thank everyone on the forum who gave me advice or helped me.  I would also like to thank pete for all of his advice an his spring guides which worked great!  Also Jm for his spring/seal/ and lubes.  I couldn't have done this tune without u guys.  It's been a great learning experience.

So I recieved my parts last night from crosman to convert the gun to .22cal, assembled the rest of the gun and shot a few rounds last night to make sure everything was sound.

To give you guys an up to date on mods:  I installed a JM seal, with a tarantula spring, along with Pete's custom guides.  I also custom fit brass thrust washers at the pivot point.

The gun cocks smooth no crunching nothing very smooth.  It shoots just as smooth.  Seems like there may be more recoil, but it makes no noise at all very quiet.  There was virtually no dieseling at all.  I saw a little bit of smoke one time that was it.  

Now for chrony numbers in Feet per second.

With the numbers from the later group I'm looking at about 13.5 ft-lb's of energy which isn't bad but I was expecting more power.
   Should I go with heavier pellets due to the stronger spring??
    I know that I damaged the seal but could that cause that much power to be lost?

Here is my main concern the accuracy...



Those are 3" diameter circles and that is the best group I could get at the bottom.  10 shots.  The top group is about 25 or 30 shots.  I was shooting at 30 yards off of a bench rest I would expect at least 1" groups at 30 yards.  These arent even 3" groups maybe 3 1/2" groups.  

 Do you guys think that maybe I should be more patient I shot 250 or more rounds.  The barrel is new, and I cleaned all the gunk outta the barrel before I shot it.
  I have a new leapers scope with a one piece mount on the gun. It  isn't my shooting technique.  The gun locks up nice and tight no play whatsoever.  I used loctite on the  pivot screw.  could the slight damage to the seal be causeing this?

I wonder if switching to the .177 barrel would have more energy?

Any advice would help.

[Rocker1]

i kinda figue it should be shooting 750s i may be wrong i would check the seal for sure. thanks david

[JonnyReb]

 And try some different pellets!!  Jsb's and rws comes to mind. Congrats on the rebuild!  J

[Springer25]

yea I thought it would be shooting at least low 700's  Is it possible that the piston is slamming against the front of the compression chamber before it has a chance to compress all the air in front, due to the seal being damaged? 
What pellet weight should I be using with this spring in .22 cal?

[Rocker1]

the deviation is good,   maybe  just shoot it a while see if those numbers come up some, i would have thought it would be shooting a little faster than  that . i got a remington summit in 22  same power plant i will shoot it across the chrony tomorrow  give you something to compare to. i am suprised no one else has had a say so  maybe pm gene see what he has to say i would bet he knows. thanks david

[Pete]

I would have thought 630 to 650 was Ok for a .22
Remember the internals are basicly the same as a Gamo
in dimentions..& a standard .22 gamo is rated at 722...
and shoot around 630/650 in the real world....

In fact it was prob putting out more fpe as a .177
as it would have been shooting around 940fps
940 , 7.5g = 14.8fpe

[bwana]

I think the accuracy problem is probably the seal. What kind of groups are you getting at 10 yards?  I should get my parts from Crosman today to convert my Quest 1000 and G1 to .22. Try some different pellets at different distances and let us know the results. Good luck and congrats on the tune. Even if it's not perfect at least you learned a lot and that's part of the fun of the sport.

[MichaelM]

with a standerd deviation of less then 5 it MAY be the seal but I wouldnt think so.... at 30 yards pellet choice would be my first pick....then muzzlecrown and technique.....

how much damage did you do to the seal??

[Springer25]

I took off a sliver large enough to see pushing the piston/seal past the cocking slot.  I bought a new one when it gets here I am going to install it.

I just measured the distance I was shooting at yesterday it was 35 yards exactly. 

I don't have work today so I went down and shot some groups at 30 ft/  10 yards. 



There are 3 groups there.  the bottom group below the quarter is what really gets me  it started off shooting right on the mark then POI moved to the right and started shooting a nice group there...
That has to be a tell tale sign of something when the group is good and tight then just moves like that and stays tight..

The other groups are just all over for being 10 yards.  I am thinking about tearing the gun open and checkin out the seal now.  Deburring all the areas and also I am going to hone the compression chamber. prepping it for the new seal when it gets here.

[Springer25]

Does anyone know what would cause the groups to shift like that?  And the gun should be shooting ragged one holer's at 10 yds right?

[Rocker1]

my summit is a 22 and its shooting 730s it should be the same power plant i know it took forever to break it in i shot better than a tin of pellets through it before it got right, all i have done to it is lube and deburr  and i did put a polished washer in it and i filled the guide with silicon and let it dry. thanks david

[Springer25]

hmmm.  Well I ordered a new jm seal which should be here by the end of the week I am going to be gone all weekend But I'll prob reassemble the gun monday, with the new seal see if the velocity is higher.

[bwana]

You said you have a new Leapers scope on it. Is it AO? If not, what is the parallax set at? From the groups you are getting it seems to be shooting better before the gun is warmed up. Since you know the seal is bad it may be that the bad seal starts to affect the accuracy after it is warmed up and maybe a little softer. I would stop worrying about it and just put some pellets through it until you get the new seal. You could put the .177 barrel back on and see what your groups look like. I bought a used Ruger AirHawk that shot poorly and it took me a couple of weeks to figure what was wrong. Hang in there, as Red Green always says "We're all in this together"

[Springer25]

yea, I also ordered the round piece that holds the detent on the barrel from crosman, when I put the brass washers in I guess they are so tight in there.  I can't get that piece out.  so I'll have to wait on that one...  from looking at the bottom group I know this gun will be a solid shooter when it's all said and done.

thanx

[Alan]

Congrats on the conversion, should be a nice shooter.
I'm still foggy on this.....is it true....In general, JM (apex small) seals perform better in a HONED cylinder .vs. OEM unhoned. 

OEM seals are harder duro and like the shiny OEM cylinder walls?

Thanks.

[Springer25]

Ok guys so I have been tuning air guns all day today!  I deburred My g1 with a deburring tool.  which worked great! Installed the new apex seal and lubed the gun up.  I realized that the spring wasn't sticking out near as far past the tube from when I originally installed it.

I could almost compress it by hand!!!  So I assembled and went out shot some groups through the chronograph.  It is now shooting at 500 fps can barely get over 520 fps.
  
So i stick a factory spring in with factory guides it shot 490 to 505 fps.

Both were shot with .22 cal 14.3 grain CPHP's

I have a picture of the seal I took out.  But is it possible I damaged the spring with that seal?  Or did I just get a bad spring?

I dunno, it's confusing because It was just shooting 680 the other day,  but after 250 shots the velocity went down 40 fps,  maybe this spring isn't rated for .22 cal?  but really the .22 pellet has more surface area to be pushed on so using the 14.3 grain in .22 is prob the same pressure as the .177 with 7.9

[Rocker1]

 you might stack a  polished washer or 2 on the top hat thanks david

[Springer25]

I could do that.  how many should I put in there?  And your saying to add them to the top hat side.

edit:: only had 3/4" at rear.. realized... you can't add any shims to the rear guide or it wont latch.

[MichaelM]

1 inch of shims??? wow.... I dunno seems like an awfull lot of shim to me.... suprised the spring compressed that much more!!! without it being fully bound

[Rocker1]

Schmidt lol!!!! i don't think i would put that many i just meant 1 or 2 maybe, you could get into cocking issures. i would add them to the top hat, thanks david