Spurious Speed Deviation - FX Impact M3

[IanB]

Anyone had issues with there Impact M3 randomly dropping speed, not a small amount, the fun is tuned to 960fps - 292 m/s for shooting slugs but every now and then the gun will drop to around 640fps - 195 m/s are around that mark, then back to 960fps - 292m/s for 5-10-15 shots. I've removed the 1st stage regulator and monitored regulator pressure, this seems stable and I've changed to the new brass piston also trying to remedy this...

Someone suggested it might be a Hammer issue, the internals have not been touched and they are as supplied by factory..

Any suggestions ?

 

[RodrigoR]

i'm having this behavior with my maverick .25.

 

[Chukar60]

Folks if you want help with your gun the good people here need information. Pertinent information to diagnose your situation.
OP states their gun is shooting @ 960 fps. Shooting what at 960 fps?
What are your reg settings? OP states they deleted the first reg. Good info but what is the second reg set at? Gotta have that number.
What are your hammer settings? On the M3 where is the micro adjuster set? Include the macro as well.
On the Maverick need to know 1st and 2nd reg settings, power wheel setting and the IHS dimension.
On the M3 where is your valve knob set?
Every point of adjustment on your air gun is critical to its function. All the things I listed will affect how the hammer and valve interact with each other. Without knowing all those values there is no way to diagnose a problem.
Not hammering on you, just saying with generalized posts like these you are going to get crickets for a response.
Worse you get frustrated and turned away from a great sport.
Wish you all the best and hope the forum can help you fix your issues when they get the needed information.

 

[IanB]

Folks if you want help with your gun the good people here need information. Pertinent information to diagnose your situation.
OP states their gun is shooting @ 960 fps. Shooting what at 960 fps?
What are your reg settings? OP states they deleted the first reg. Good info but what is the second reg set at? Gotta have that number.
What are your hammer settings? On the M3 where is the micro adjuster set? Include the macro as well.
On the Maverick need to know 1st and 2nd reg settings, power wheel setting and the IHS dimension.
On the M3 where is your valve knob set?
Every point of adjustment on your air gun is critical to its function. All the things I listed will affect how the hammer and valve interact with each other. Without knowing all those values there is no way to diagnose a problem.
Not hammering on you, just saying with generalized posts like these you are going to get crickets for a response.
Worse you get frustrated and turned away from a great sport.
Wish you all the best and hope the forum can help you fix your issues when they get the needed information.

Why do you have to have that number, how would it explain a spurious 300fps drop on occasion ? The 2nd reg is set at 140barg, if it was set at 110barg, 130barg or 160 barg, it should not do that, the hammer is in no way maxed out, and it's not going over the curve and dropping back off in power from too much hammer for the reg. I've tried the valve stop right out and edged in until a slight drop is noticed.

I own other impacts, mk2's and they are no issue at all.. Hence the reason I'm asking for anyone who has noticed similar.

 

[nervoustrig]

Do the slow shots produce a weaker report or a louder report or the same?

 

[Gambler]

Can the chrony be low on power or interupted of some sort?
I guess you have checked it but that was the case with me.
Does the shot that drop down in fps also drop low when shooting at paper?

 

[IanB]

I also tested at 50yds and I get a great group and then get a random shot drop 2" and slightly left. Testing on chrono shows a spurious 300fps speed drop intermittently ...

Really annoying

 

[nervoustrig]

Really annoying

Really annoying indeed. Sort of like when someone volunteers to help troubleshoot a problem by asking a very simple question with a very simple answer, and is ignored.

 

[Chukar60]

Why do you have to have that number, how would it explain a spurious 300fps drop on occasion ? The 2nd reg is set at 140barg, if it was set at 110barg, 130barg or 160 barg, it should not do that, the hammer is in no way maxed out, and it's not going over the curve and dropping back off in power from too much hammer for the reg. I've tried the valve stop right out and edged in until a slight drop is noticed.

I own other impacts, mk2's and they are no issue at all.. Hence the reason I'm asking for anyone who has noticed similar.

Just a process of elimination.
I had a Maverick that had a rough edge on the hammer that caused it to have weak hammer strikes occasionally. worked the burrs down and then polished it up with 3M cloth. Solved the issue. You may also want to check the passageway for the hammer and make sure it is free of any debris.

 

[weevil]

Why do you have to have that number, how would it explain a spurious 300fps drop on occasion ? The 2nd reg is set at 140barg, if it was set at 110barg, 130barg or 160 barg, it should not do that, the hammer is in no way maxed out, and it's not going over the curve and dropping back off in power from too much hammer for the reg. I've tried the valve stop right out and edged in until a slight drop is noticed.

I own other impacts, mk2's and they are no issue at all.. Hence the reason I'm asking for anyone who has noticed similar.

Well - people often come on here to seek generous advice and have some really odd settings and mods. One I recall recently had a guy shooting an M3 or Maverick with a tungsten hammer and a reg pressure of 110bar, which yielded the scenario you describe above. In fact, most of the issues people report are user error, so the helpful folks around here, like Chukar and ‘trig, are simply requesting contextual info. I was going to ask the same question as ‘trig. How do those low shots sound in comparison, both in terms of the hammer action and the muzzle? Many of us were tuning before chronographs were around and used our ears and the feel of the shot cycle to determine when we’re on the knee of a tune.

The other thing I’d suggest is taping some tissues around action/breech to see if there’s an oring that’s failing to hold on occasional shots.

 

[Raider03]

Double loading (2 slugs) will cause that much velocity drop.

 

[IanB]

Issue resolved, through some fault finding.

Problem was my own fault, I fitted a Kraford and Lypt probe carrier, which are excellent, but I didn't check probe seating depth, the probe was only half way across the transfer port, doh !!!! Adjusted and much better...