How Often Do You Replace Your Breech O-Ring?

[MikeAllen]

I know this has been discussed before but here's my issue - my stock .25 cal FX Impact will occasionally become inconsistent in poi and extreme spread. Replacing the breech o-ring resolves the issue. This seems to happen after only 2-3 tins of pellets - so about 600-900 shots. This seems excessive to me. I'm shooting 34 grain JSB and FX diabolo pellets. 2nd reg is at 120. Pellet probe has never been removed. This has only begun within the last few months - did not happen when I bought the gun a little over a year ago. The last two o-rings I used were from Captain O-Ring. Any Suggestions?

 

[nervoustrig]

Check that the probe doesn’t have a burr or sharp transition, and install a polyurethane O-ring for better abrasion resistance. Try 90 durometer first but if chambering is too tight then step back to a 70.

Unfortunately I don’t know a source for cast polyurethane in metric sizes or that would be better still than injection-molded polyurethane.

 

[MikeAllen]

Check that the probe doesn’t have a burr or sharp transition, and install a polyurethane O-ring for better abrasion resistance. Try 90 durometer first but if chambering is too tight then step back to a 70.

Unfortunately I don’t know a source for cast polyurethane in metric sizes or that would be better still than injection-molded polyurethane.

Thanks nervoustrig - I had a feeling it might be the o-ring quality I was using - I'll try to track down o-rings you suggested.

 

[MikeVV]

A touch of silicon lube doesn't hurt either.
I've mixed up a semi-thick oil and put a drop on the probe of all of my guns, no matter if the o-ring is on, the probe, or in the breach.

Mike

 

[MikeAllen]

A touch of silicon lube doesn't hurt either.
I've mixed up a semi-thick oil and put a drop on the probe of all of my guns, no matter if the o-ring is on, the probe, or in the breach.

Mike

Thanks - I've been using a VERY light coat of silicone oil each time. Maybe silicone grease would be better...

 

[iAMzehTOASTY1]

Thanks - I've been using a VERY light coat of silicone oil each time. Maybe silicone grease would be better...

what makes one better than the other? *honest question*
Or does one work better for certain things?

 

[nervoustrig]

Mainly just viscosity. In an application like a breech O-ring where pellets pass through the O-ring, neither one will be present for long but every little bit helps.

 

[jarmstrong]

if the groove for the o-ring has a sharp edge, it can make a circumferential cut on the face of the o-ring, leading to an early failure
I had one gun(non-FX) with this problem, used these with a hand held pin vise

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not saying this is the problem, just food for thought, but on mine , I could see the cut on the o-ring face

 

[TDK]

Like others have said, check for sharp edges on all parts. I don't think i've had one go bad in practice (stock NBR70). I've shot 2k+ without issue. Usually gets swapped because I have the barrel out for some reason, or because I run into a problem and swapping the breech oring ends up having no effect on it. Your shot count sounds really low.

 

[Firewalker]

I change mine if I get a puff of air on my face or the fps changes.

 

[bigHUN]

600 to 900 shots and you complain you need to replace the 1c oring?
I don't want to think about that oring if leaks or not, I am replacing it after every 2-3 liner cleaning. $3 for a bag of 25 ??? but that is just me...

 

[MikeAllen]

600 to 900 shots and you complain you need to replace the 1c oring?
I don't want to think about that oring if leaks or not, I am replacing it after every 2-3 liner cleaning. $3 for a bag of 25 ??? but that is just me...

I don’t think I recall complaining. My post was to determine if this was normal and if not, what the cause might be.