American Air Arms Evol having cardiac arrest

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greenbeans

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Oct 1, 2024
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Orange County, New York
New to me 15in Evol in .22… needed some work from the beginning and I though I got it there but this last thing is damn persistent…

It’ll shot a handful of shots or so at the speed I set it to (965fps with 18grain / 890ish with 22 grain), then 1 to 3 or so shots way slower, then back to set speed. Example:

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This happens with any and all pellets I put through, 18gr, 22gr, 25gr doesn’t matter. With the 22 it’ll shoot 890, then 830-850, then 880 again. 25gr 840ish, then 800 and back up.

Spread was way worse when I got it. What I’ve done so far is: Set reg to 2,100psi, pulled hammer and spring, cleaned hammer channel properly, cleaned and polished hammer and spring, balanced hammer to reg at around 96.5-97% of max speed…

I’m almost guessing the reg is shot but, per gauge, holding pressure constant. Interestingly, it has the purple reg but based on the rest of the gun and serial it is a newer model and should have the blue reg, right?! The gun also sounds different when the slow shots occur, I can tell without looking at the chrony numbers… obviously also from POI… when it’s shooting as it’s supposed to it’s very accurate with the 18gr but the weird slow shots are all over so can’t trust it for now. Tried with different mods obviously but no change. The one on it right now is a Falx, which can go up to .30 so there shouldn’t be clipping.

Hoping the Evol fanbase has ideas ;) Thanks in advance!! Orings to rebuild the reg and basically the entire thing are on the way.

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Degas the cylinder and get to the regulator. I would do a rebuild of that for starters and make sure everything is good and clean, with just a small amount of lubricant. Make sure you use the suggested lubricant that Tom suggests, other wise you could find yourself getting into more problems.

The rifle is really easy to work so, so dont hesitate to open it up and do some cleaning. Toms rifles are extremely durable and not much to go wrong with them.
 
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woogie_man said:
Degas the cylinder and get to the regulator. I would do a rebuild of that for starters and make sure everything is good and clean, with just a small amount of lubricant. Make sure you use the suggested lubricant that Tom suggests, other wise you could find yourself getting into more problems.

The rifle is really easy to work so, so dont hesitate to open it up and do some cleaning. Toms rifles are extremely durable and not much to go wrong with them.
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Yeah that’s on the list once the orings arrive, so is pulling the valve and make sure it’s fine as well… No hesitation here to tear airguns apart :) still weird… it’s consistently inconsistent. Can almost predict the next slow shot.
 
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Hobbyman2007 said:
Any chance the hammer is dragging on the sear ? I haven’t studied the internal workings very much but that is something that gets overlooked quite often.
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Good idea. Checked that though and looked fine. Also based on how the hammer is designed it’s basically flying once the sear lets go. May be the “anti rotation” screw on the hammer is dragging but looked fine as well when i had the hammer out…
 
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I’ve had my fair share of inconsistent regulated rifles. Most were due to leaking probe o rings. Once in the last 10 years have I had a regulator problem where it was leaking past the piston , poor quality oring was at fault. Barrel/ transfer port leaks are another problem area. Mushroomed / bent valve stems from too much hammer strike and high reg pressures.
Just looked at the diagram and there’s really not that many seals in these guns to go bad. I’m sure you’ll get it with a fresh set of O rings.
 
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Hobbyman2007 said:
I’ve had my fair share of inconsistent regulated rifles. Most were due to leaking probe o rings. Once in the last 10 years have I had a regulator problem where it was leaking past the piston , poor quality oring was at fault. Barrel/ transfer port leaks are another problem area. Mushroomed / bent valve stems from too much hammer strike and high reg pressures.
Just looked at the diagram and there’s really not that many seals in these guns to go bad. I’m sure you’ll get it with a fresh set of O rings.
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Thanks! Yeah hopefully full reseal will do the trick… hard to get parts for them if it’s more than that…
 
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JaceSpace1369 said:
I want to say that's a reg issue, either reg is sticking on certain shots, possibly something with the valve. I have that same issue with my U2 600mm .177 I'll get tight 1-2fps spreads and then boom 17fps lows, then back ups, then again 12-15fps low.
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Yeah will pull the valve as well once I have the orings… gotta get the guns in shape for a flash sale if the stock market keeps doing what it’s doing ;) JK, they’ll be the last thing I sell :)
 
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greenbeans said:
Yeah will pull the valve as well once I have the orings… gotta get the guns in shape for a flash sale if the stock market keeps doing what it’s doing ;) JK, they’ll be the last thing I sell :)
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Just a few days ago I grabbed a DNT 335R before the market did it's thing. That's same morning the 635R went up $400
 
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Sooo I received to orings the other day and took the gun apart. The good news first: seems like I calmed its heart rate down :) not perfect yet but way better than before:
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There’s bad news though… this is how the reg looked like:

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Mind you the gun is supposed to have less than 200 shots through it… Plus maybe another 200 from me meanwhile. Whoever was in this thing before me shouldn’t be allowed to own fine mechanical machinery… Anyway, polished everything up, new orings, lubed properly etc. Also polished the trigger sear while I was in it, was beaten up as well. Plus hammer, and valve:
IMG_5849.jpeg


Now here’s where the fun starts: got the gun tuned more or less, strings looking ok but still lacking in the accuracy department. Well, I should probably not put it that way. It is shooting great but it throws way too many random Flyers. Out comes the borescope, look at this:

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And no, those are not 3 pics of the same “ring”. It’s 3 separate ones in the last 2 inches of the barrel (sorry for poop barrel pics/video, took them with phone off the bore scope screen):


What to make of this?!?!?
 
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Holy Smokes!!!!! That is horrible, I can’t believe that left the factory with a barrel that bad. I’ve had quite a few TJ’s barrels come through and never seen one that bad. And the workmanship on the regulator? I’ve done some pretty poor work in my day and don’t claim to be a perfectionist but I mean come on. That’s really bad.

Here’s what I can share so far with the experience I have with the paradigm. The hammers and HS spring are meant for high power, the bigger the gap in free flight the bigger the spread in velocity. I try to keep the gap to a minimum for consistency. Sure you can use the rear adjuster to reduce or increase velocity but I think it’s missing one thing, a preload adjuster for the spring itself . At least the hammer assembly I have in my rifle. It doesn’t look like what’s in the parts manual. Mine has a retaining washer and screw essentially making an SSG. I’m fairly certain this is a factory set up. I may take it apart again to see if I can make some adjustment .
 
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Hobbyman2007 said:
Holy Smokes!!!!! That is horrible, I can’t believe that left the factory with a barrel that bad. I’ve had quite a few TJ’s barrels come through and never seen one that bad. And the workmanship on the regulator? I’ve done some pretty poor work in my day and don’t claim to be a perfectionist but I mean come on. That’s really bad.

Here’s what I can share so far with the experience I have with the paradigm. The hammers and HS spring are meant for high power, the bigger the gap in free flight the bigger the spread in velocity. I try to keep the gap to a minimum for consistency. Sure you can use the rear adjuster to reduce or increase velocity but I think it’s missing one thing, a preload adjuster for the spring itself . At least the hammer assembly I have in my rifle. It doesn’t look like what’s in the parts manual. Mine has a retaining washer and screw essentially making an SSG. I’m fairly certain this is a factory set up. I may take it apart again to see if I can make some adjustment .
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Yeah it’s rough… I’m not sure that the barrel left the factory like that. I mean, how could that even happen?! Looks to me like someone got multiple slugs stuck in the barrel and fired them into each pitcher. Like double loaded, fired, and shot another one into the two stuck in the barrel near the muzzle. No idea man, but the barrel is probably done for. Would like to replace the reg as well just based on looks but it is doing a good job so far. Maybe just optics but function seems good after rebuild. If only it were easy to get parts for Evols…
 
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