Leaky seals? Need some expert advice.

[djmyers]

Got new pellets today and was testing them when I noticed my Gamo Hunter was not burying them into the wood very deep. I shot a few gropus and they are right on hole in hole at 35 ft. Break out the chrono and am averaging 761 with JSB 7.33 gr. I was shooting 920's 2 weeks ago. I got the big cat and its shooting good same as last time. I shot H&N 10.65 gr that were close to 800 fps and now are 653! I got some lube out and put a drop in, loaded JSB 7.33 and it was in the 650's then next one was 1194! My ears were ringing from the crack of it. So then I did that cycle about 7 more times.

Shoot, its in the 760's then oil its in the 650's for the first shot after oil  then the next shot was averaging 1163!   Then back in the 760's for the next shots until I oild it then 650's for the first shot after oil 1100's for the 2nd.  The weird part is its still pin point accurate when shooting in the 760's and the high to low spread was 747-768. thats not a big spread but the muzzle velocity is definatly fallen off.

I think leaky seals, what do yall think?

And how hard is the seal to change?

Thanks in advance for the help.

Dj.

[longislandhunter]

Take the rifle apart and examine the seal.  If it is indeed the seal then order an Apex small seal from JM and you're good to go

I had the same problem last month with one of my GAMO S1K's.   Instead of shooting in it's normal  900's the chrony indicated it was shooting low 700's.  Opened it up and found that the seal had a chunk missing.  Popped on the new Apex small seal, slapped her back together and ran her through the chrony and she was right back up in the 900's again.  

While you have it apart take the time to clean out all the old grease, deburr it and apply the proper lubes.... she'll be better than she ever was.

Also,, stop putting oil in it to pump up the fps.... definitely not a good thing to be doing  !!!!

Jeff

[Mark 611]

I agree with LI stop putting chamber lube in your your transfer port this will destroy your rifles guts!

[djmyers]

Will stop lubiing the chamber hole. Thanks for the advice on that one.

Couple questions on the seal replacement.

Will I need a spring compressor to ge the gas piston out? or will I be able to slide it out like a shock on a car?

Can I just google search the procedures and places to get the seal or can you give me a link?

I got a chinese flee market special that has blown seals in it figure I will crack it open first. I figure the principle should be the same.  

Last but not least are there any trick pins or hidden springs that are going to fly away when I open this thing up, and any tricks of the trade that yall know of to help me out on this.

Thanks for the help.

[Mark 611]

I would  probly say yes I don't own a gamo but thier just about like anyother springer I'd think!

[airiscool]

".........Will I need a spring compressor to ge the gas piston out? or will I be able to slide it out like a shock on a car?  ..."

There will be some amount of preload on the gas ram and any at all is way more than you can push against by hand, so yes, you'll need a spring compresser.

And with a few "oiled" shots (ouch !!!) through the gun,  I'd plan on changing that seal. If it's not already toast, it probably will be soon.

J Maccari's website for new seals and springs.
http://www.airrifleheadquarters.com/page/page/251327.htm

Paul.

[djmyers]

Thanks for the info. Looks like I will be ordering the rebuild kit. From the sounds of what you guys are sayin on the oil in the hole, I hope I didnt kill my gun. Man I feel almost sick.

On a good note its another excuse to buy more tools and learn something new that I am sure I will use again.

[djmyers]

http://www.airrifleheadquarters.com/catalog/item/251488/7718385.htm

Is that the right one?

Now for a manual and spring compressor! I figure I have about 7 days to read the directions at least 5 times and play with the chinese one before the seal kit will get here.

[shadow]

That kit will work and they give you two seal's since once is slightly larger then the other. Test fit the seal after it's installed on the piston in the compression chamber and if one seems to snug with much resistance then switch to the other seal. Ed

[djmyers]

http://www.kermitairgunclub.com/airguntips/compressor/page2.htm

Home made spring compressor! I am in business, this dont look so hard.

[Mark 611]

Ya see, its not so hard!

[longislandhunter]

That was the very first spring compressor I ever made and it worked well.  I've since constructed a new one that is more adjustable to fit different rifles, but that one on the Kermit website will do the trick....

Let us know how you make out....

Jeff

[djmyers]

Just got done breaking down the Chinese rifle with the home made spring compressor and da$& was that easy! I can't wait to get my parts n for my other rifle. You guys are awesome! Thanks for the guidence. I will get pics of it on here later tonight. Thanks for all the help.