Need a Gamo Magnum IGT piston seal

[mikeyb]

Here is the history of shots from my Gamo Swarm Magnum:

2018
Crosman premium hollow point 14.3gr (CPHP)
919fps (915 - 925fps for 5 shots), 26.8fb
JSB Exact 18.13: 800fps 25.8fb

08/25/24 to 9/12/24 in the order of time for each pellet

CPHP: (8/25) 869, 873, 845, 859, 848, 853, 846, 827, 827, 827, 827

H&N FTT 14.66gr: (8/25) 852, 818, 819, 824, 837, 807, 815, 821, 813, 829, 829, 847, 829, 829, 824, (9/11, shimmed breech seal) 856, 829, 822, 820, 818, 823, 816, 819, 820, 822

JSB 15.89gr (8/25) 815, 803, 802, 794, 793 , (9/4, new magazine) 821, 807, 795, 789, 784, 787, 782, (9/11, shimmed breech seal) 795, 790, 785, 785, 785

(1) my gun was never as fast as in the AGD review but not too shabby

(2) from 2018 to 2024, the speed drop is significant, energy dropped from 26fb to 22fb. My Crosman Mayhem has a similar drop (from 22fb to 18fb). In contrast, my springs guns have no drop in speed.

(3) the gun was very accurate back in 2018. It is still accurate but less so, likely because wider spread in speed

(4) I can rule out breech seal or magazine being the problem. Suspected piston seal but hard to imagine they will go bad on both my piston guns but not going bad on my spring guns. Crosman technician said piston had pressure even when not cocked and therefore piston seal more likely to fail than spring guns. I do not know enough to know if that is true.

If the gun can keep consistent speed I am ok with shooting it slower. But if there is a piston seal problem then I worry about it gradually degrade further.

While I have not seen it yet on any of my airguns with a "gas spring", it seem like your gas spring is slowly losing pressure. I have had six leaky Hatsan Vortex "air springs" (more prone to leakage) and they lose Muzzle Energy over time frames anywhere from years to hours.

[Wolverineshooter]

I agree it is losing pressure, not sure what is the cause. Could it be that the piston seal go bad more frequently on "gas spring" as the crosman customer service stated? If so certainly that would change my future purchase decisions to avoid gas springs powered guns.

My $25 Walmart Beeman Kodiak spring guns shoots the same now as before speed wise but getting more accurate (could be me ). It seems easier to maintain than gas spring.

Crosman customer service advised against any service including lubrication of the chamber. RWS said put drops of chamber oil occasionally, every several hundred shots. I have so far not putting any chamber oil into my guns' chambers. Wondering if that could have saved piston seals.

[Wolverineshooter]

Personally I would advise against Moly anywhere around the transfer port or breech seal area.  I reserve it for the piston and the outer piston seal area.  Just my opinion.

AGD reviewed a gen 2 Swarm.
With 14.66 gr H&N FTT he averaged 940FPS.  Go to the Chronograph section of the vid.

He also did what looks to be an earlier generation and he averaged 911 FPS with 14.66 gr.

Agree with moly not around the transfer port. When cocking the gun it will sweep some to the transfer port causing dieseling.

My Gamo Swarm Magnum is the original or first generation, with vertical loading magazine. The reviewed guns are all much/ faster than my gun when new. Would be interesting to know how they are doing now and if they experience the same speed loss

[Thor760]

Greg here is a picture of my Gamo Bone Collector piston seal after about a year and a half of moderate use.  It’s the gen 1 variant.  I built a spring compressor out of some lumber I had laying around and used a c clamp that I cut in half.  You’re guns behavior was similar to mine.

I opted to clean and hone the compression chamber, replace piston seal and I put a replacement gas ram in for good measure.  Ordered the Gas Ram from https://www.customairseals.com/ and the super moly lube and Tesla Seal from https://www.airrifleheadquarters.com/page/page/251484.htm.

I opted to go big and it turned that Gamo into a great shooter.  If you are up to it, getting into these Gamos is not difficult at all.  Lots of write ups on this forum and a lot of videos on YouTube.

You may want to open it up inspect your piston seal first and then take it from there.


The three photos show the orig seal and its questionable condition.  The other shows me cleaning the old factory lube out of the chamber with a wooden dowel and drill.  Very satisfying.  Finally the spring compressor.  I use a few Harbor Freight straps to secure the gun while compressing the gas ram.  Gas Rams don’t take much pressure at all compared to springers.

[Rocker1]

 I have until i could get parts flipped the breach seal and space it with dental floss, it will work until you can do better and with Gamos you always have to wait on parts. David

[Wolverineshooter]

Thanks Ryan for sharing. Maybe the Crosman service is right the piston guns are more prone to have piston seal problems.

I have not disassemble the gun to work on chambers yet. I may try it. Unfortunately Air Gun Headquarters is not doing any tunings I believe or otherwise maybe they can do something for me.

I do like the accuracy and power of Gamo Swarm Magnum. It is a motivating factor for me to get fit so hopefully I can still cock this beast when I am 80 . I have another Gen 1 still sealed. Just hope the gunk in it will not become solids and ruin the gun.

[Wolverineshooter]

I have until i could get parts flipped the breach seal and space it with dental floss, it will work until you can do better and with Gamos you always have to wait on parts. David

I did the dental floss but no improvements whatsoever. Gamo also sent me a new breech seal but I do not think breech seal is a problem.

RWS suggested to put chamber oil in to help the piston movement infrequently. Crosman supports said there should be no maintenance of any kind unless it is broken. If I open the chamber I will put some moly or Krytox in.

[Thor760]

 RWS suggested to put chamber oil in to help the piston movement infrequently. Crosman supports said there should be no maintenance of any kind unless it is broken. If I open the chamber I will put some moly or Krytox in.
[/quote]

Be careful with anything in the chamber. If you do get into your gun to inspect/replace parts and you relube;be sure that no Moly is in front of or on top of the piston.  Moly should be applied to the side of the piston seal and the piston body.  You want to avoid dieseling and detonation which the latter can ruin the internals.

[Wolverineshooter]

RWS suggested to put chamber oil in to help the piston movement infrequently. Crosman supports said there should be no maintenance of any kind unless it is broken. If I open the chamber I will put some moly or Krytox in.

Be careful with anything in the chamber. If you do get into your gun to inspect/replace parts and you relube;be sure that no Moly is in front of or on top of the piston.  Moly should be applied to the side of the piston seal and the piston body.  You want to avoid dieseling and detonation which the latter can ruin the internals.
[/quote]

Great points. Sometimes I wonder if I should use PPTF which will never dry up and no dieseling

[splitbeing]

Krytox or teflon can be dangerous if not done properly. The stuff already in your gun, even little bits of it, do not play nice with krytox.

[Wolverineshooter]

Krytox or teflon can be dangerous if not done properly. The stuff already in your gun, even little bits of it, do not play nice with krytox.

Yeah it needs an extremely thorough cleaning, even then things could migrate.

[splitbeing]

Curious what you'll find opening up the gun. Possibly some rough spots to deburr in addition to a gas ram and piston seal assessment.

I like the smell of ARH lubes after a tuning. I may use more than others [chuckling].

[Wolverineshooter]

Curious what you'll find opening up the gun. Possibly some rough spots to deburr in addition to a gas ram and piston seal assessment.

I like the smell of ARH lubes after a tuning. I may use more than others [chuckling].

You may try to steal from perfume from your wife to mix with it

[splitbeing]

Moly, by Calvin Kline [chuckling]

[Wolverineshooter]

Well I shot more of my Gamo Swarm Magnum and it seems there is a further slight drop in speed:

H&N FTT 14.66gr: 822, 827, 819, 810, 813, 818, 817, 806, 809, 819

JSB 15.89gr: 786, 793, 793, 795, 794, 789, 774, 785, 780, 783

[Jr007]

Vortek making a 33mm piston seal - Scheduled release/date: June 9th possibly before.