Optimal distant between MPA-3 Ram and Sear

[pk5]

Hi Everyone

What is the optimal distant between the MPA-3 Ram and the sear?

Also: I noticed that most of the arm for a pneumag setup tend to be a cut down nail or aluminum pin, have anyone try to use something even lighter and smoother? Delrin? Titanium? carbon fiber?

[BigEvil]

Gassed up approx 1/8".

You can use a cut q tip shaft or a peice of welding rod for the trigger pin.

[Spider-TW]

If you have a fat lpr like a micro-rock, you can make the gap about 1/16". With something like a tickler, definitely stay around 1/8". I've used (still using) phenolic as a push rod. I would stick with something light.

[pk5]

Is there any other ideal material for a push rod? The hole that was drilled in my frame is a bit small, so right now a nail fit, but i am just wondering is there any other smoother material to use?

[Spider-TW]

I haven't heard of anything ideal. If a nail is too big, I might look at "piano" wire or just hobby steel rod of the diameter you want. Like BigE said, just about anything will work. I try to keep it light, but if it is very skinny, steel rod should be fine. Brass should work too, if a little heavier. Aluminum rod (like bare welding rod or hobby aluminum) would work too.

[TwilightG]

I think someone here once mentioned using a bamboo skewer too. I just wonder if it might splinter or wear down over time (not that it would be expensive to replace )

[OPBN]

If you have a fat lpr like a micro-rock, you can make the gap about 1/16". With something like a tickler, definitely stay around 1/8". I've used (still using) phenolic as a push rod. I would stick with something light.

Out of curiosity, what difference would it make as to what type of LPR is used in regards to the gap?

[Ando]

Recharge rate, amount of pressure it uses to trip the sear, also the volume they hold. Micro-rock LPR seem to do the best job.

[Spider-TW]

Out of curiosity, what difference would it make as to what type of LPR is used in regards to the gap?

I only had a couple years of fiddling with my one setup; however, the tickler would consistently droop below functioning pressure over several minutes, depending on the set pressure.

Because of my MPA-3 mounting and the piston I used, my gap was about 1/16" or a little less, aired up. I would set the lpr at its lowest functioning pressure then add a half turn. Apparently I had a very small leak and after several minutes I might pull the trigger and the ram would move, but not hard enough to trip the sear. I spent an evening playing with the tickler setting and letting it sit for different amounts of time. At about 80 psi, it either exceeded my patience (30 minutes) or was starting to bump the pressure back up when it dropped. I tried cleaning, lubing and changing o-rings. I could see a difference in the time to failure, but I couldn't eliminate it. Pulling the trigger several times would normally get it going again. I learned that I could bump up the tickler setting just a little right before I took my first shot and not have any trouble.

There are a lot of ticklers in pneu mags and I don't think there is anything different with mine. I think if I had more of a gap, the extra volume used would force the tickler to open up and put more pressure on the sear.

Playing scenarios, I couldn't put up with a failure to fire after waiting 30 minutes (which happened a few times). I was also headed toward EP'ing that frame and wanted to keep the pressure under 70 psi for the little SMC solenoid. All else being equal, I stuck a micro-rock on there and all my pressure problems were solved. It runs about 50 psi. I can make the micro-rock do the same thing, but that is turning it down to about 40 psi, where it can barely push a perfectly clean and lubed sear and on/off. It will fail to fire after sitting a while at that pressure, whereas it was shooting fine when you set it.

I expect it is a combination of seals setting up (lpr and on/off), like FSDO, but the LPR does seem to be a significant part of it.

[OPBN]

Ok. Thanks for the explanation. The pneu'd frame I bought came with a larger diameter LPR, but I switched it out for a slimmer bullet style that I had laying around. Much more aesthetically pleasing, and I didn't really notice any performance difference so far. I have a micro rock that is intended for an ebolted Tippy project that I may end up going to if I have issues.

Also, what is FDSO? I have seen the term a coupe of times and havent a clue.

Sorry for the thread jack.

[Spider-TW]

Ok. Thanks for the explanation. The pneu'd frame I bought came with a larger diameter LPR, but I switched it out for a slimmer bullet style that I had laying around. Much more aesthetically pleasing, and I didn't really notice any performance difference so far. I have a micro rock that is intended for an ebolted Tippy project that I may end up going to if I have issues.

Also, what is FDSO? I have seen the term a coupe of times and havent a clue.

Sorry for the thread jack.

First Shot Drop Off. It really isn't something you normally talk about with mags (takes two different problems to happen in a mag). My fault.

You see it in "low pressure" markers where the seals start to get "sticky" while sitting in the lube a while and they leave you with a pathetic first shot.

Same fundamental problem with regs though. You have to keep them operating outside the band of pressures they will stick (hysteresis). It's a combination of the sealing of the seat and the movement of the piston seal. Still applies to your LPR selection.

Some people have enough trouble that they turn up the lpr high enough that oiled hose barbs don't hold very well, which is a problem for a mag that likes oil.

Which brings up a point. My stock tickler barb was poop. Had no hose grip at all. If you have trouble with that particular joint, that's a barb I would replace.