FX FX Impact M4: What o-ring material???

[Dunk1302]

Hi All...... after much reading here, it's become obvious that my .25 M4 is suffering from the classic "warm up" problem: first shot of the day is ~100fps low and it takes about a dozen shots to get up to the tuned 950fps.

So, I plan to strip the gun down and polish the valve rod, and replace the offending o-ring, but what material should I replace it with? I have FPM90 (Viton) and PU90 on their way in the post. The current exploded diagram on the FX site specifies FPM90, but is that the old spec or the new one that is supposed to prevent the warm-up problem?

Thanks in advance

Dunk

 

[dasenahk]

Hi All...... after much reading here, it's become obvious that my .25 M4 is suffering from the classic "warm up" problem: first shot of the day is ~100fps low and it takes about a dozen shots to get up to the tuned 950fps.

So, I plan to strip the gun down and polish the valve rod, and replace the offending o-ring, but what material should I replace it with? I have FPM90 (Viton) and PU90 on their way in the post. The current exploded diagram on the FX site specifies FPM90, but is that the old spec or the new one that is supposed to prevent the warm-up problem?

Thanks in advance

Dunk

I suggest reaching out to your retailer as well. Apparently they've been sent the needed parts, but I don't know for sure myself.

 

[Dunk1302]

I suggest reaching out to your retailer as well. Apparently they've been sent the needed parts, but I don't know for sure myself.

Thanks - I've contacted Sportsman Gun Centre (the UK importer for FX), but as yet no reply.....

Dunk

 

[jps2486]

Go on the FX website and click on support. Then check out the parts breakdown for your rifle. It will tell you the O ring size and hardness.

 

[HogKiller]

Hi All...... after much reading here, it's become obvious that my .25 M4 is suffering from the classic "warm up" problem: first shot of the day is ~100fps low and it takes about a dozen shots to get up to the tuned 950fps.

So, I plan to strip the gun down and polish the valve rod, and replace the offending o-ring, but what material should I replace it with? I have FPM90 (Viton) and PU90 on their way in the post. The current exploded diagram on the FX site specifies FPM90, but is that the old spec or the new one that is supposed to prevent the warm-up problem?

Thanks in advance

Dunk

The spec on the website is correct, you don't specify which of the 0-rings you are referring to but the numbers appear to be for the smaller ones on the adjuster. The others are 70's My thing is LUBE them, you want them to slide, a light polish on the Bellevilles IF there are any, I have Mavericks, and LUBE them. I highly recommend a good synthetic oil, I use a light Mobile 1, and NO it will not blow up. My thing with airguns is...if it moves, it gets a very light coat of oil. On those little suckers, get a bunch of extras, they break easily, I dunk them in boiling water, lube, and get them on quickly. I haven't had my regs apart in more months than I can remember and they work fine from cold or hot, the first shot may be a touch low but meh.

 

[Swish]

I just replaced those o'rings yesterday in my M4 that had the same warm up issues.
Tuned for 980fps with 34grn slugs and sitting over night , I just shot 957, 972, and 980fps. I used these specially formulated ones from ebay.

Not perfect but way better.

 

[R0B]

Hi Dunk,

I'd let the Sportsman fix it under warranty. You have 3 years and once you go into it your warranty will be invalidated. It shouldn't cost you a penny.