My suggestion would be to take it apart and see what's going on...
I'm with Metal, I think your piston head or O-ring isn't doing it' s job.
I'm pretty sure that m150 has probably not let your piston cycle all the way back, and if it's polycarb or cheaply made, you might have some ate out teeth or broken ones...
This is what i'd do... I'd get a m110 or m120 spring...
Go to lowes, get a #14 Oring set, and replace that Oring on the piston head.
Get rid of that M150... it's not going to give you any more , high FPS maybe, but it's not going to let ya shoot any light BB worth a crap, and as I said before it's over-kill. That spring will eat up your motor fast, and tear up your internals.
To get top performance out of a m150, you are going to HAVE to replace every part almost in that gear-box, and possibly the shell of the gear box as well... I promise you, it will not hold up long if you don't, and at that point, you might as well, just buy a new upgraded AEG for what you are going to spend replacing needed parts, with high end stuff.
The CA sportlines, were never meant to have such a high velocity spring system in em. There's a reason they come with High Speed Motors in em... even the gear ratio is for higher speed set ups. ( it's cheaper grade gears. )
They simply weren't made to be high FPS or high velocity shooters in application.
Most generally all "sportlines" are intended to be a reasonable and cheaper alternative to the more "expensive" varieties.
Now, that's not to say... they can't be upgraded, but not from stock to "extreme" upgrades.
Also, it isn't a "bad gun" to start with... stock performance should have gotten ya by easily. If not, I think it's be a manufacturing flaw, or you bought it used from someone that really didn't take care of it, or know how to maintain it.
So, replacing the motor, with a high torque motor... but it still has light to high speed gears, should be alright for a m100 or a m110 , MAYBE a m120... maybe.
Lets say you go a m110 ...
That, if your airseal is good... is going to place you in the 330-360 FPS range with a .25 and hop up engaged. 350 FPs is optimum generally for field grade AEG combat... your .25s will go as far distance wise, as if you had a 400 FPS set up. Honestly, the "gain" from a higher FPS spring, is somewhat negligible... that 5-10 feet isn't really going to make much difference when you are actually in a simulated combat situation.
( It will be about 375-380 FPS, with Hop up off, with a .20 BB, not sure with a.25 with hop up off.)
Anything from 340 FPS through 400 FPS is generally what you'd want out of a field grade primary anyways. There's no need for anything higher, unless you are going for something very specialized... like a DMR.
I am assuming, you just want your primary operational, and to perform well on the field, and not going DMR or Sniper rifle with it. ( it's the "wrong" model for one of those though.)
You max range on BB flight, if not doing the "robin hood arrow drop" , (that is aiming in a high arc...) will be about 275 feet distance. ( about 92 yards, or 91 meters ) ... your accurate distance ( the range you can most likely hit a 2x2 target 75% of the time ) will be around 60% of it's total flight distance, which would roughly be at 55 yards, or 150 feet away.
That means... INSIDE 150 ( roughly) feet, you are more likely going to hit what you aim at ... given if there is no wind, or the BB has no variations. Outside 150, up to your max distance... every 10 feet drops that probability of a sure hit by about 10-15 percent. That is per single fired BB. ( which is why folks love FA outside... they can "walk" missed shots in, or send more, increasing a chance of a hit.)
MOST of your engagements in simulated combat are around 150-200 feet away outside anyways, or closer than that.
300 feet( 100 yards) or more... is usually too great of a distance, due to obstructions, wind/air distance, and concealment to accurately engage any OPFOR. The BBs will not travel that far generally anyways. Not with a roughly 1% chance of accuracy or less.
The fact is, you can see alot farther, than any "normal" velocity AEG can shoot. You can ( and people often do) shoot or try to at those distances... but sure hits are very rare, most of it is luck or perfect conditions if they do.
However, if you REALLY pay attention, good action "battles" and firefights, happen at much closer distances.
Even Sniping Rifles of high FPS ratings, with heavier BBs, and DMRs still have trouble accurately hitting a target at 300 feet away. The range, because it's a plastic round BB... just isn't there.
(It isn't real steel, the logistics are WAY different. )
The only "advantage" of a DMR or Sniping Rifle is they increase ACCURACY ( or are supposto) INSIDE the flight path. They don't really get much more in total range... they can just increase the percentage of ACCURATE distance inside a set max range to begin with.
Yes, they may get another 40 feet of MAX distance... maybe, or maybe more or a bit less... just depends. But the farther a BB travels, the less likely it is to accurately hit a target or OPfor.
So, back to the thing here...
Now that we've established, the BB will only go so far... how do you get max ACCURATE shot distance out of it?
First off... disregard FPS a bit... it IS NOT as Important as one is misled to "believe".
Instead, focus on AIRSEAL ... ( which does increase FPS by default if you are still worried about it.) So a m110 with a base rating of 340 FPS with a .20 BB, in an AEG with a great Airseal, is going to get about 380 FPS out of it.
Engaging hop up... is going to bring that FPS down a bit ( it's friction and slows down your BB a bit) , but it puts "spin" on the BB, to IMPROVE it's flight capability.
Tighten the barrel bore, only slightly... I've found 6.01s not to be as good as a 6.03 ... I think , due to variations in BBs... the tighter bores, often provide too much "friction" even if it does focus the airflow more. ( Kinda defeats it's own purpose in a way.)
The Combo of those 3 things... will offer you a greater accuracy distance, at a decent and MANAGEABLE FPS rating.
My example...
My Stock JG G36,( m120 spring) at a 380 FPS has a shorter accurate distance, and shorter range , than my MP5 that has about 350 FPS. ( m100 spring)
The differences , besides the different spring... is the JG is still stock. I hadn't air sealed it, I hadn't put a nice bucking in it, It has a 6.08 barrel in it. It shoot fine and all that as is...
But the MP5, I redone to increase distance and accuracy ... I dropped in a Tighter barrel, new nice bucking, and got my airseal as good as I can get without silicone the piston head.
I shoot .25s outdoors in both, and my MP5 with less FPS, performs a bit better hands down.
The "speed" of the BBs in flight, negligible , or you can't notice it by the naked eye... though obviously the MP5 shots travel slightly a bit slower than the G36 BBs do. ( only can tell by the chrono though, lol.)
So, in my opinion... you just tried to put "too much" behind the BB, relying on the spring to do the work for ya... which is a common mistake made. ( Just ask PorkChop , and the 51/50 guys, lol )
That and the internals, were never designed to take that kind of power or punishment, not out of a sportline, and I would say not out of most non-sportline models as well.
m150 springs, were made for 2 reasons:
1- for high end sniping rifles...
and
2- To sell to un-knowing FPS chasers.
a m150.. is just flat out, too much spring... and not enough BB by default.
