Is the gun completely stock? If so, then it could be a few things causing the veering to the left.
1. The stock hop up is cheap and not very good, as is the rubber. It could be deformed, putting more pressure on one side than the other. You could need an entire new hop unit, just a new rubber, or even just a hop arm.
2. The stock barrel could be a cause of the problem, with two possibilities: it could simply be bent, I've seen people say this about Well stock barrels, or, the cut outs at the end could be misaligned, the notches that hold it in place in the unit or hold the rubber on not lining up with the hole cut for hop to be applied - this was the case in my L96. If it's either of these, you're going to need a new barrel.
3. The outer barrel, could be causing the problem in a few ways: the mag catch that screws into the hop unit, through the outer barrel, holding it all together could be misaligned, meaning when you put the gun together, even if the outer barrel is straight, the inner barrel and hop won't be, if this is the case, it's simple to fix - loosen the screw and adjust accordingly. The outer barrel holes cut into it could be misaligned, meaning you'll probably need a new outer barrel, or maybe you could drill the holes out a bit to make them the right place/size/shape. It could also be that the outer barrel isn't aligned properly, as there's a little play in it, take the stock off and loosen the grub screw in the bottom of the bolt housing to twist the outer barrel to align it.
4. A combination of all of the above issues.
Regarding getting a new hop and inner barrel, which are the most likely two to be causing the problem, you have multiple options for each:
Hop Units.
1. You could source another stock hop unit as a replacement in hope that it is built better, or you could get a new hop arm, or both even.
2. Get an ASPUK hop unit, this gives a better air seal than the stock one, comes with a better hop arm, and uses the same adjustment method. Only thing is, you'll need to use AEG cut barrels and hop rubbers.
3. The most expensive, get a PDI hop unit. Has advantages of even better air seal than the ASPUK hop unit, has two hop arms, which can be fiddly and annoying to set up, but once done correctly, will allow you to fine adjust for BBs veering off to the sides as well as up and down. Once again, you'll need AEG barrels and hop rubbers for this, and they can be very fiddly to adjust - the Allen key that comes with it isn't any good for adjusting once the stock is on the gun, and it's an extremely small Allen key, I believe 1.27mm.
Barrels.
1. Once again, source another stock barrel - I wouldn't advise this, as you probably won't notice much improvement, they're a very basic and cheap brass barrel.#
2. Depending on what hop unit you get, you'll either want an AEG cut or specific L96 cut barrel. You can get moderately priced tight bore barrels quite easily, personally, I wouldn't go lower than 6.03mm inner diameter, but other people have claimed better results from a 6.01mm. I suggest MadBull for a decent price
erformance ratio.
3. Go the expensive, but best, route once again and get a PDI barrel. They make both AEG cut and L96 cut at the perfect length for their hop unit, you'll struggle to find another AEG cut one at the right length (495mm), and they're a very very high quality. People say that diameter is important, maybe it is, but I think it's pretty negligible, with some people claiming better results from 6.01 and others 6.23, barrel quality, material and finish is much, much more important. I currently have a PDI 6.05mm inner barrel in my L96, and this far out performs my previous barrel, a MadBull 6.03mm. Giving me better consistency, better range, accuracy and a higher FPS (50-60 higher) - meaning I can reach that 500 limit by putting less strain on the rest of the internals.
If you have any other problems or questions regarding the L96, feel free to PM me or ask on here, I'll get a notification either way. I've had my L96 for a few years now, and despite it not currently working correctly (completely jammed it, waiting to get home from uni before I can get it sorted), I think I've encountered every problem possible with the gun, and I've had 3 sets of internals; stock ones, full ASPUK with MadBull barrel, and full LayLax/PDI, and pretty much any mix/combination of the three possible.
