[blackfoot1]

I found three airsoft guns in the attic yesterday, one of them was my old MP001 "Sharp Shooter" (which I thought was a little optimistic).

If you type MP001 into Google you can actually hear the internet groan with disgust...
I've read endless internet drivel about these guns and heard all the horror stories about this and that not fitting, I was told it wouldn't accept an upgrade trigger set only trigger parts, well I tried a TM G-spec trigger on mine and it works perfectly...
Surely this would mean a complete upgrade trigger set would fit too?
Also this particular gun has a removable cylinder head so I will be seeing what I can get in there to spice things up a little.

On an indoor range at 15m (49ft?) it was grouping five shots at just over three inches :'(.
It's firing one shot to the left by about 1" and the next to the right by the same amount, after shimming the hop arm, cleaning the barrel and hop rubber/bucking the problem was still there. It has me stumped.
I'm really enjoying tinkering with this gun and it's a real pleasure to shoot, but the wandering POI is a bit irritating.
Anyone got any ideas what could be causing the problem?

If the wind dies off sometime soon I'll get outside and see how it shoots over a longer range. If I can fix this problem, I just might have found my competition rifle

*Notice I didn't say competition "winning" rifle

 

[chappie]

One of my older airsoft sniper rifles did this to me and come to find out the inner barrel was bent. This could be the same problem with yours. Also maybe even check out the hop up and give the whole gun a proper cleaning (if you haven't already).
I hope this helps

 

[blackfoot1]

If it was a bent barrel I'm pretty sure the POI would stay consistent, It wouldn't change from left to right each shot (it would be off target yes, but it would be off in the same place each time).
Because it changes, I think it must be a moving part that is "moving" in the wrong direction e.g. the hop arm or maybe the bucking isn't staying seated properly.
I've tried to shim and tape everything up as well as possible but maybe I'm missing something.

Would I be right in saying that the piston/spring has no effect on BB accuracy and that it's got to be the hop or the barrel causing the issue?

I will check for a bent barrel when I get home from work :-[

Edit
Got home, stripped the gun and checked for a bent barrel but it's as straight as can be...

POA was dead centre of the box
In case you can't make out the numbers -
Shot 1 hit the top of the box
Shot 2 was directly above 1
Shot 3 was the first of the fliers and hit to the left
Shot 4 went crazy and nearly missed the target completely
Shot 5 hit right and up of shot 1.

I'm using .25 BB's (.28 has the same problem)
15m indoor range
Target is roughly 4" wide so the fliers arn't flying too badly but they shouldn't be flying anywhere except where I aim.

Edit #2
I've managed to reduce the number of fliers by re-shiming the hop arm and wrapping a layer of tape around the pin it pivots on.
Jamming a coin into the slot where the hop adjuster arm sticks out next to the barrel also means the hop can't creep, making things a little more consistant.
On the downside, we now have a feeding issue. Every now and then It will try to load three BB's. This isn't really a problem, you just pull out the mag, shake the loose BB's out, re-cock the gun, fire the BB out of the hop and bung the mag back in.
This usually happens when I've shot three sub one inch shots and only need two more for a personal best five shot group :