M3 - friction in the hammer/valve system

[TDK]

On my .22 M3 I have what seems like intermittent friction in the hammer or valve system. What happens is that I can dial in a speed, then when I use it days later, speed may be 70-100fps lower. If I shoot it long enough (LOOONG like 50+ shots) the speed might return to where it was. Maybe on a good day the speed starts out close to where it should be set (normal).

The regulator is rock solid always returning to the set point (digital gauge).

Breech o-ring has been replaced and I don't feel any air puffs in that area (passes toilet tissue test).

Hammer friction seems least likely since that is a pretty simple part of the system.

I'm very familiar with the Impact cold-start behavior, but I don't think I've ever seen it exceed ~10 shots on this gun in it's earlier days. My first thought is that this has to be caused by the same PUR90 valve rod o-ring (E103) that is responsible for Impact cold start behavior, and mine has deteriorated and/or needs relubing.

One more factor with this gun is that over the winter, I experienced what seemed like 'valve leak'. After a shot, I heard air escaping through the transfer port and down the barrel. Dry firing about 5 times got it to stop and it has not happened again since. Is there any valve failure mode that could result in friction/resistance to opening and be contributing to my inconsistency?

At minimum, I'm looking at replacing the E103/104/105 o-rings, but would like to know if I should be considering replacing the valve as well. Also, is there any better lube than SuperLube Silicone Grease for the valve rod and that pesky E103 oring? Anything else I'm missing?

 

[Airgunmann]

Up your hammer strike just a bit you can tune the cold start most of the way out it doesn't sound like a o-ring problem sounds like a hammer problem more to me but I guess you would have to dig into it to find out for sure if the valve sealed back up I wouldn't be overly concerned about the valve leak you will be able to inspect it if your changing out the orings in the plenum

 

[Airgunmann]

You can make a peek spacer to keep the oring out of the pinch point and use a viton oring to eliminate the cold start issue all together as well there was a big long thread about the issue and there are dimensions for the peek spacer viton oring and a spacer oring to keep them in place

 

[TDK]

This isn't a typical cold start issue. Both of my M3s are tuned at the knee. On my 92fpe .30, it is 3 shots max, but even those first shots are pretty usable. On this .22 at 44fpe it started out more like 5-10 shots, but considering my current problem, I wonder if something has been slightly off since the beginning and only gotten worse.

 

[corny]

I have yet to own an FX that doesn’t do this.
But I’d say the 720 plenum was the worse….can be somewhat addressed with tuning. But it’s not really ideal for a hunting platform. Where you often get only one shot….and can’t really fire one into the dirt.

 

[Stubbers]

I have yet to own an FX that doesn’t do this.
But I’d say the 720 plenum was the worse….can be somewhat addressed with tuning. But it’s not really ideal for a hunting platform. Where you often get only one shot….and can’t really fire one into the dirt.

It's because FX uses balanced valves that are susceptible to break out friction on the first shot after set periods. You really can only work around this using buffers and tuning within 98-99% of the guns peak fps.

-Matt

 

[Vetmx]

What Matt said and if your .22 is worse then you have to look a little deeper. What’s the reg setting on the .22 versus the other gun. Where is your micro on the .22 versus the other gun. There are quite a few things different between the two guns that can mess with the first cold shots and how long it takes to get the engine warmed up. All of my Impacts have parts installed to help with the issue but all three of my guns behave a little differently cold. If you can’t find the accuracy with your chosen projectile with a wicked hammer strike for the reg setting, you either have to install some parts to help the gun or become a member of the dry fire community before you start to put in some work with the gun.

 

[corny]

It's because FX uses balanced valves that are susceptible to break out friction on the first shot after set periods. You really can only work around this using buffers and tuning within 98-99% of the guns peak fps.

-Matt

I generally tune around 90-95% of peak.
And even at that…some required 3 shots to get going

 

[Stubbers]

I generally tune around 90-95% of peak.
And even at that…some required 3 shots to get going

That will make a notable difference from 98-99% from peak, j/s. Still not shocked, and the larger your plenum the more this is exacerbated if any reg creep is present to boot.

Break out friction is when a dynamic o-ring sits and its squeeze which allows a seal, over time pushes most of the lube away from itself and the wall it seals against, so the first or even several shots are dry and require more hammer strike until the seal is lubed again. With how little movement our valves take, and even less when tuned away from peak, its no big shock to see it take several shots to 'settle'. A poppet may only lift 2mm or .08" from its seat which translates to o-ring movement being equal when tuned 90% from the peak, where it may be closer to 3mm or .12" when tuned at 98% of peak (these are arbitrary figures given as an example).

-Matt

 

[corny]

That will make a notable difference from 98-99% from peak, j/s. Still not shocked, and the larger your plenum the more this is exacerbated if any reg creep is present to boot.

-Matt

Cycling any gun at 99% will make for a harsh shot cycle…not a good balance.

 

[Stubbers]

Cycling any gun at 99% will make for a harsh shot cycle…not a good balance.

Disagree, its only when you push it over 100% is when its harsh, this entirely depends on the gun and its state of tune (reg pressure ect)...

-Matt

 

[jarmstrong]

tune to the knee or just below delivers efficiency = best mpg stuff
tune just above the knee will help with the slow starts, = best performance
with all respect to Mr Bob Sterne, the man who educated me for efficient air guns tunes.

with todays air compressors I do not care if I waste a little air, I am not a hand pumper worrying about getting the highest shot count

 

[Stubbers]

tune to the knee or just below delivers efficiency = best mpg stuff
tune just above the knee will help with the slow starts, = best performance
with all respect to Mr Bob Sterne, the man who educated me for efficient air guns tunes.

with todays air compressors I do not care if I waste a little air, I am not a hand pumper worrying about getting the highest shot count

Not sure what the 'knee' is as defined here, but I will add that the further from your peak/plateau you tune, the more your thermal efficiency increases until it peaks at around 40%, or in volumetric terms, 2.5 fpe/ci.

-Matt

 

[7Green]

Do a search of the forum on valve stiction. It is a fairly known issue that some have tried to address.

 

[TDK]

What Matt said and if your .22 is worse then you have to look a little deeper. What’s the reg setting on the .22 versus the other gun. Where is your micro on the .22 versus the other gun.

Yeah, I'm definitely going to tear it down. Trying to go into it armed with as much information as possible. Reg 125, Micro around 3.5. It's tuned around 94%. The beginning of the current tune, it was ~Micro 3.25 to get the right speed. Then one day I had to bump it to 3.5. Last time I checked (and the trigger to this thread) 3.5 was giving me 70fps low even after 10 warm up shots. The entire time I still get a max velocity of 995, so that tells me that its a friction issue that seems to be increasing.

My other M3 is a .30 - reg 148, hammer around 4.25. It sat for a year and when I pulled it out first shot was around 20 fps low and by third shot it was on the money. I totally get more warm up shots being required for lower hammer spring, but what I've got here with the .22 seems out of control. What would you estimate the "appropriate" number of warm up shots for 125bar/3.5 Hammer/94% tune to be? Gun is stock, no upgrades.

 

[Stubbers]

Yeah, I'm definitely going to tear it down. Trying to go into it armed with as much information as possible. Reg 125, Micro around 3.5. It's tuned around 94%. The beginning of the current tune, it was ~Micro 3.25 to get the right speed. Then one day I had to bump it to 3.5. Last time I checked (and the trigger to this thread) 3.5 was giving me 70fps low even after 10 warm up shots. The entire time I still get a max velocity of 995, so that tells me that its a friction issue that seems to be increasing.

My other M3 is a .30 - reg 148, hammer around 4.25. It sat for a year and when I pulled it out first shot was around 20 fps low and by third shot it was on the money. I totally get more warm up shots being required for lower hammer spring, but what I've got here with the .22 seems out of control. What would you estimate the "appropriate" number of warm up shots for 125bar/3.5 Hammer/94% tune to be? Gun is stock, no upgrades.

Definitely raise your velocity to 97-98% of peak by lowering your reg or increasing your hammer strike.

The need for extended warm up shots could be the o-ring on the balance piston is swelling more on this gun than your other, is not the same durometer for some odd reason, may extrude more dude to tolerance difference between piston and bore, or isn't lubed with the same lubricant. Those are just a few suggestions among many other possibilities I may be unaware of. GL

-Matt

 

[Vetmx]

Yeah, I'm definitely going to tear it down. Trying to go into it armed with as much information as possible. Reg 125, Micro around 3.5. It's tuned around 94%. The beginning of the current tune, it was ~Micro 3.25 to get the right speed. Then one day I had to bump it to 3.5. Last time I checked (and the trigger to this thread) 3.5 was giving me 70fps low even after 10 warm up shots. The entire time I still get a max velocity of 995, so that tells me that its a friction issue that seems to be increasing.

My other M3 is a .30 - reg 148, hammer around 4.25. It sat for a year and when I pulled it out first shot was around 20 fps low and by third shot it was on the money. I totally get more warm up shots being required for lower hammer spring, but what I've got here with the .22 seems out of control. What would you estimate the "appropriate" number of warm up shots for 125bar/3.5 Hammer/94% tune to be? Gun is stock, no upgrades.

Let me look in my notes.

 

[Vetmx]

Ok, looking back on my two MKll’s and M3’s, the average was about 5 shots to get them cruising at the proper velocity. Of the 5 guns in my notes, some would be within a reasonable ES number in 3 shots and I even experienced a dramatic slow first shot with one or two guns. If you aren’t going to build parts to help with the PUR oring extrusion and you plan to hunt with the gun, you’re going to have to try to find the accuracy you currently enjoy being tuned at the knee further up on the hammer strike. My one M3 is tuned at probably 98-99% for slugs but it has a real barrel and it does fine. My .22 Compact M3 slugger with a factory barrel just fights me unless I’m close to the knee but I am slightly above it. With my mods it only has one slow shot if the gun sits and it’s not horribly slow. But it is slow enough that the gun is harmonically off its slug tune so I won’t fire a cold shot at something past 50 yards. My pellet shooting M3 with mods has a slightly slow first shot but it’s no big deal with pellets. At the distances I hunt with it, the pellets don’t care. I cold shot a bird at 80 yards with it a couple weeks ago. That gun is tuned at 97% with a 130b reg setting so if you fix the oring extrusion problem, it really helps. Hope some of this helps get you pointed in the right direction.

 

[Scotaty]

I had this problem and solved it by polishing the valve rod and valve puppet with a very high grit. Now even first shot is at normal set velocity.
I used dremel to rotate the rod and used cloth polishing materials.

 

[bigHUN]

I polished the valve rod to mirror finish on portion where the PUR oring slides, also lapped the valve puppet to the seat. These will minimize the the friction between moving parts.
Also, polished the hammer + valve springs ends, originally these comes as a rough cut. When the spring compresses it morphs and turns, I minimized that friction as well, and applied a small touch of moly grease so it can morph easier.