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DIY The importance of seals in airguns

The importance of seals in airguns

by Tom Gaylord
Writing as B.B. Pelletier

This report covers:

  • What is so important?
  • NRA Show sample gun
  • Thinking
  • Breakbarrel breech seals
  • Pneumatics and CO2 guns
  • Summary

Today’s report was supposed to be about the accuracy of the Umarex Synergis rifle from 25 yards. Sorry, folks, but this other topic came up and I HAD to do it today. Brother-in-law, Bob, don’t fret. Tomorrow! And, Jungle Shooter, Friday was supposed to be about the accuracy of the Artemis pistol at 25 yards. Monday, for sure.

What is so important?

Let me tell you a little story. A couple days ago I purchased a nearly new-in-the-box IZH 46M target pistol. I know! Stop salivating! I will sell it when I’m finished with it. I had planned to do a comparison review for you between the regular 46 and the 46M that is the later more powerful magnum version of the same gun. But when I chronographed this new gun it was only shooting 250-300 f.p.s. It’s supposed to be up around 500 f.p.s. with light lead pellets, while the regular 46 goes about 425 f.p.s. with the same lightweight pellets.

NRA Show sample gun

The new gun had been a sample at one of the NRA shows held annually around the nation. It is complete and looks like it has not been shot or even handled much. Then I looked at the breech that raises up when the gun is cocked. It moves up and back to give room to load the pellet into the back of the barrel. There are supposed to be two seals on this part and one of them was missing. Fortunately the Russians supply the guns with the seals for a rebuild, so I installed a new breech seal. Next shot with the same 7-grain pellet went out at 475 f.p.s. Not bad for an airgun that has probably been sitting around untouched for 18-20 years! That’s a gain of 175 f.p.s. for the installation of one breech seal.

I even have a “secret” method of bumping up the velocity of these SSP airguns and I will do that with both pistols when I test them for you. And yes, of course I will show you how it’s done. I did it on year one (2010) of “American Airgunner” but they don’t rerun those older episodes, do they?


That got me thinking. What other things do airgun seals do when they go bad? And that caused my imagination to explode! That’s why I’m writing this short report today — as an introduction to an equally short video on the importance of seals for airguns.

Breakbarrel breech seals

I thought of the breech seals in many breakbarrel rifles and pistols. A lot of them are just o-rings that to the uninitiated may look fine, and yet they can rob the gun of significant power.

An o-ring can look fine and still be bad. Many o-ring materials dry out over time and become hard. In the breech of the breakbarrel they may flatten a bit and allow air to rush past them instead of going up the barrel behind the pellet. I have seen instances where as much as 20 percent of the gun’s velocity is lost through a faulty breech seal. The best solution is to replace the seal. You can also shim an older one and get by for a little while.

Pneumatics and CO2 guns

Here is the most dramatic case of all — old seals in a pneumatic or a CO2 gun. In the past 4 years I have FIXED about 90 percent of the airguns I have treated with Automatic Transmission Stop Leak. Not just made better — FIXED!

I had to share this with you today, and to do that I made a short video. You may want to expand the video to full screen to see the details.



If you buy or acquire older airguns, and even guns that are new and have never been used but are still older, you need to consider the condition of their seals. The mechanical parts of the gun may function as they were designed, but if the seals have dried out, taken a set or are even missing, the airgun may not function well.

46 thoughts on “The importance of seals in airguns”

  1. B.B.,

    You might want to try uploading the video again as that I can’t find it nor does it play when I click on the link, which if I try to copy shows itself as b:356.


    • Yogi,

      On those very rare occasions that you lubricate the piston seal, it is advisable to use a good quality clear silicone oil. Here is one of the many that PA carries.


      I add a couple drops of silicone oil to the female foster fitting every few times that I fill a PCP airgun. This will blow into the reservoir and will migrate through out this and eventually the rest of the airgun, lubricating seals, thereby extending their life and also sealing off minor leaks. It also lubricates the female foster fitting, helping it to operate better.

      As for the breech seals use diver’s grease. This is a clear silicone grease. It is used on HPA equipment. I picked some up at a local dive shop, cheap. Here is one that PA has.


      This will help to keep O-rings and such from drying out and does not easily migrate. This tube is probably a lifetime supply for your needs.

      I am not aware of a silicone grease that could be used to replace TIAT red grease. A silicone grease with that kind of tackiness would be great for sproingers. I will have to explore the food grade open gear grease. Perhaps this is a silicone grease. Do any of you folks have a clue?

      • RR,

        I used to work at a place that made “freeze-dried” coffee,.. as a maintenance tech.. The (cold room) was -80 F at the coldest point. I could go “in” 20 minutes max. with TOP end gear. Things moved relatively slow. The main case for the lube was lubrication at (very) low temps.. And,… food safe in case of accidental introduction into the process stream.

        I would stick with TIAT,… tune in a tube,… as has been discussed here. Well,.. unless you are hunting Polar Bears in the Arctic,…. with a,.. springer air gun??? 😉


  2. Hello BB, may I suggest you to extend this post by explaining the difference between the rubber types used for o-ring seals and which suits best what type of application?
    RidgeRunner, did I get your comment right, you’re looking for a tacky silicone grease to use for sprionger mainspring dampening ? I think I heard that silicone grease is not suitable to lubricate metal to metal contact areas, just to help seal and keep rubber seals smooth. Could it be that the information I have is erroneous?

  3. BB

    A little seal 101 for everyone.

    There are basically 2 types of seals to keep it simple

    1) O-rings that are US sized # system or Metric

    2) Proprietary seals such as the IZH 46 Breech or say FWB 124 piston seal as examples , these are made by the Airgun manufacturer for a specific application

    On o-ring sizes The AS568 is a # system as example #009 is a common 22 caliber breech seal and probe o-ring . There is a chart to match these up
    The Metric system is simplest with the ID in Millimeters and Diameter in Millimeters being the size. Example FWB 124 breech seal is a 10 x 3 mm ( 10mm ID and 3mm diameter )

    Hopefully this helps people understand most airguns have a combination of proprietary seals and standard o-rings . This is in Springers , Pneumatics and PCPs


    • Gene
      With you on the metric o-rings. Luckily that’s what our machines use at work.

      And by chance can you post a picture of the chart for the AS568 # system. I think that would be good to have if needed. Like if I was trying to get a little different fit for whatever reason.

    • I recently replaced the piston seal o-ring on a FAS 6004 overlever SSP with a quad seal – of the various benefits claimed for these, and supposedly just a straight swap for o-rings, the ability to hold a small amount of lubricant in the seal itself seemed worthwhile. The piston head does already have a felt ring that acts as a wiper on the inside of the cylinder.

      It certainly works in this application, but I haven’t used it enough, or for long enough, to see if there’s any long term benefit in reliability or consistency.

      The manual rather helpfully includes an exploded diagram and gives the metric sizes of all the various o-rings in the gun.


      p.s. BB – my experience of Baikals is that the first two digits of the S/N are the year of production – 05 on yours – and the original factory documentation is handwritten with the S/N and production date.

  4. Fret. Fret. Fret. Not because of your review of the Umarex Synergis but because the “available date” keeps being moved forwards. Out of stock is a very unpleasant message, especially since it has never been “in stock”.
    This is a revolutionary repeater, and I WANT ONE. Several months ago, I saw it reviewed on the Guns & Ammo TV show. Any news on what is the holdup? Hopefully not design problems. Patiently (not really) waiting.


  5. Well I haven’t posted for awhile.

    I ended up getting food poisoning or something last Tuesday and I don’t mean this week Tuesday. Ended up going to the hospital Sunday over the weekend and didn’t get out of the hospital till Tuesday this week. Been getting things caught up around the house. Finally going to shoot some here in a minute after zero shooting since last Tuesday. I’m ready.

    • GF1,

      Glad you are on the mend. That is a long time for food poisoning.

      I have not had time to do any shooting this fall. Too much work getting ready for winter and repairing equipment. I hope to get some shooting in this weekend.


      • Don
        Not 100% sure it was food poisoning. All I know is I never been that sick before. What was a bummer is I never got to eat anything until Monday night all those days. Was starving hungry by then. They gave me chicken broth and it was so good. It was like eating a steak. But yep don’t want no more part of that again. Was terrible.

        Just did some shoot’n. Still hit’n good so I’m happy. Hope you get some shoot’n time happening.

    • GF1,

      Sounds like NO fun. Glad you are doing better. Last week,… a young fellow who is a temp. went out for breakfast Sun. AM. He left some of it in the car all day Sun. (mid-high 80’s) and had some for “breakfast” Mon. AM before work. He mentioned he was not feeling so well in the AM. He finished it off for “lunch” Again,…. mid-ish 80’s Mon. He did not have a pleasant afternoon at all.

      He asked if leaving the food in the car that long might be the cause of his ill feelings. ??? I explained that food should not be left out for more than 2 hours and then refrigerated at about 40 F or tossed. (He had never heard of that,… at 21 years old) This must not be a topic that is on Facebook, Twitter, the internet or taught in schools. Go figure? I went easy on him as he was in enough distress already. The next 24 hrs. were not good,… but he avoided the hospital and missed the next day,.. but was back the next feeling much better.

      At any rate,… glad you are doing better. Questionable food choices/situations aside,… it could have just been some kind of super bug?


    • GF1
      Wow! That had to be a horrible experience. Sounds more like a stomach virus. Food poisoning doesn’t usually last that long, or require a hospital stay. That’s a hard way to lose weight! Glad you are feeling better now in any case. Take care.

      • Geo
        Thank you. And I really never have been so sick.

        I went back to work last night for the first time this week. My supervisor went home early last night. He’s getting the exact same things I had going on. I told him I hope and pray he wasn’t getting what I had. It was no joke. Just thankful I’m feeling good now.

  6. Don425 ,

    Buna 70 durometer is the best all around type. In CO2 You could use Polyurethane seals . Some times in a regulator Viton or other materials are used . 90 plus % of applications use Buna 70 durometer . Resist the temptation to go to a harder seal, sometimes the harder material can not give enough to seal well , especially in vintage and poorly made guns. The seals have to give to take up tolerances just like a gasket on a engine .

  7. B.B.,

    Fine job on the video. I think they will be a hit and enable you to convey more information to the “masses”,… (us). 😉

    Good Evening to you and to all,…….. Chris

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