Breech o-rings

[Mod90]

Hello all, I'm looking for some insight regarding breech orings.
I was wondering recently, how often do you change breech orings? I know a worn oring can cause a small or large drop in velocity as well as accuracy issues. Reason for asking is that I recently had to change a few breech orings recently, due to the guns owners saying their guns lost accuracy for no reason they could figure out. Changes oringss, all guns accuracy returned to their usual standards.

I'm also wondering if filling in the oring groove inside the breech & installing an oring on the probe would eliminate this issue, or at least reduce recurrences of the problem. Anyone ever did anything like that?

Thanks in advance

[triggertreat]

I don't have a set schedule for replacing my breech O-ring.  I usually change it out if the gun sounds louder than I remember.  Also, before hunting season, competition or after a barrel scrub.  They last a long time if lubed with silicon occasionally.  If you go with a polyurethane O-ring, they last a really long time.


With my guns (Marauders), I would not be able to do an O-ring on the bolt due to the magazine.  I don't know about Big sexy.

[FuzzyGrub]

I'm also wondering if filling in the oring groove inside the breech & installing an oring on the probe would eliminate this issue, or at least reduce recurrences of the problem.

If you are talking mrod/prods, the indexing mags would cause an o-ring on the bolt probe to get snagged.    It would work if you wanted to go to only using a single shot tray.

[Mod90]

Thanks for the replies. Mostly seeing this issue on Hatsans so far and on one HW100. Since the Hatsans use a metal magazine, I think it should be possible put a groove in the probe & to use an oring on it.

[nervoustrigger]

If you decide to try grooving the bolt for an O-ring, please report back on how it holds up.  I suspect that wear would still be a significant factor even with the Hatsan magazine.  The mag is a snug fit to the pellets which says to me a suitably sized O-ring will drag as it passes through.
 
Personally I would focus on these items to improve longevity of the breech O-ring:
    1.  Soften (radius or bevel) the area where the bolt steps up to full diameter
    2.  Polish the bolt
    3.  Use a 70D or 90D polyurethane O-ring
    4.  Check that the bolt is not misaligned to the barrel.  I remember one person posting pictures of his Hatsan where the bolt would lift as it was closed.  That indicated a misalignment...the barrel was forcing it into position.  Usually you can feel a subtle misalignment with a conventional bolt but it can be hard to detect with a sidelever.

[Mod90]

Good ideas Jason.
All probes I inspected had no wiggle to them, and all were tapered and smooth. I also checked them for movement while cocking and loading. I do think that the orings people are using might just be too soft though, I don't know what they might have used before. I replaced them with 90D orings but  all I have are BN not polyurethane, so I guess I'll just wait and see if the problem returns.

Thanks for the insight guys.

[pecor]

I'm with Jason on the  70D or 90D polyurethane O-ring, There Tough as nails!   Jaa

[Ribbonstone]

MAybe on the Hatsan's mechanical operated mag....o-ring on the bolt probe not such a great idea on spring-loaded mags.

Yet Hatsan changed to an internal o-ring on their repeaters (they used a bolt probe o-ring on their single shot versions).

For spring loaded mags (like the P-rod/M-rod/ and many others), where loading a magazine winds a spring that powers the rotation, the problem is NOT in the insertion of a pellet...that works out fine...it's in the BACK STROKE of the bolt probe exiting the barrel for cocking.

The spring loaded mag rotates up against the bolt probe as you chamber a pellet..so as the bolt moves backwards to cycle another shot, the edge of that chamber scrapes along the  side of the bolt...and can catch an o-ring that's on the bolt probe.

With a bevel on the front edge of the magazine "spool", so there is no abrupt edge to catch the o-ring, can get away with it.  Not sure it's a great idea, as the o-riong/bolt doesn't rotate at that point, so the wear is consentrated on one little section of bolt probe o-ring....but have made it work.

[kbstingwing]

maybe just hit the pellets with a little silicone lube, make sure the pellets have smooth edges, keep the O-ring lubed too, if it's dry it will have more friction and wear quicker...