Its a nylon gearbox shell. LTD, is a metal gearbox shell.
Also, ihobby is now advertising mp5k mags, for $25…
T-piece…
Pulled apart…
@Friendly_Fire , im having trouble getting the upper part of the mag cover to slide in, over the top of the assembled gearbox.
This raised point( where screwdriver is pointing to) appears to be the rear stop for rearward travel , of the cycling mag cover . No problems, dremelling that off…?.
You mean the upper receiver? 
Looks like it might just be a stop for the blowback assembly, which you’ve disabled anyway… if so, dremel away. 
But can you tilt the upper receiver up and over it? I think it only keys into the lower receiver right at the back.
… got told the other day that they weren’t available. At least that saves me trying to mod the LDT mag
If you look at post #73, i dremelled off the downward tab, from the ejection cover assembly.
Trying to fit it in, it goes in so far, then stops.
Lots of wiggling, jiggling, and force.
It seems to be catching on something, and that tab is the likely suspect.
I’ll look 2morrow, with fresh eyes…
Would a m110 spring, be worth considering, for fps.?
I would be changing to a 50% cylinder for sure with a barrel that short. Grossly over volumed boxes don’t change much with bigger springs, you’d likely get more fps out of a cylinder than a spring.
Yes the JM has mag prime using the charging handle - which also opens the ejection port
Cheers Wombat… Good chance that’s the microswitch for priming then.
BME… STEP AWAY FROM THE DREMEL 
Too late…
It’s gone… as is mag prime…
Good news is , the assembly slides in super easy now…
Also, screwing the back plate back on, it’s very easy to unscrew the main spring rear cover, from the gear box…
Using fresh xforce pinkies, I’m seeing a more consistent 220 fps now…from jm
Premature eHACKulation…!!
Better FPS… at least you’ve cracked 200! 
I still think on the LDT a 7.3 inner barrel and porting the living daylights out of the cylinder would be a good course of action. you’re really only chasing another 20-30FPS.
But it’s your build, BME… your call. 
The JM is doing 220.
The LDT is …all over the place.
I would rather play with I/b and nozzle, before porting further….
Those steps are reversible…
Dunno about you, but I certainly don’t go onto GRINDER…!
Ah but here’s the problem…
Swapping to a 7.3mm IB may up your FPS, but it also reduces your barrel volume, making your already bad VE worse. Conversely, if you put in say a 7.6 barrel you’d increase the barrel volume and improve the VE, but you’d probably lose FPS as a result.
Swapping to a tighter bore makes porting the cylinder more necessary. In the name of science I’m happy to give you a 50% cylinder to try, no risk then.
I think the t piece is moving around, notice there’s no spring in front of it to seat it rearward like you have with most M4s… or the tappet spring’s not pulling the shnozzle forward to the same place every time. Stronger tappet spring maybe? 
I dunno, what do you think?
General question for everyone, is it worth short stroking with a 50% cylinder?
Would certainly quieten it down…
I’m happy to trial a 50% cylinder, if you have one lying around.
If it quietens it down, all the better…
Kinda annoying, upgrading the parts for better performance, and not alot happens.
We saw the increase in sealing, from leaky sieve to solid, but it didnt translate to better fps…
The 260 fps kit model, is ported, so there is that…
@Friendly_Fire it can optimise the setup well on a short barrel and 50-60% cylinder blaster.
The thing with short stroking is it can have undesirable fps loss, but it can increase cycle speed and response. Depends on spring, cylinder volume and barrel length.
Some examples… notes etc.
I would never short stroke a blaster with a barrel longer than 330mm. That said, I once worked on an m16 with a full length barrel that was short one tooth and still got power, and was as inconsistent as a full stroke m16… so it isn’t to say it won’t work it just won’t be optimal.
Full cylinder blasters generally will lose about 15fps per tooth. Given a barrel 300mm to 350mm, m100 -m110 spring.
80% cylinder with 275mm-ish barrel may not lose any fps if short one tooth, but can lose 5-10 fps. Take two teeth and you will loose 30fps on an m100 spring though.
Blasters with a 60% cylinder, can generally lose 4 teeth and still get 285-300fps with an m100 spring provided the barrel is long enough. An m110 can get around 330fps.
One of my favourite builds is an m120 spring, short 4 teeth. Full cylinder or port that doesn’t come into effect, 240mm barrel. This will send gels at 350fps.
Worth noting there isn’t a lot of gearboxes that will safely handle a m120, but it’s a fun build as you can ramp the rps to high 30s and have a great consistent blaster.
@BME if you want a 50% cylinder I have plenty of stainless ones. I’d definitely give one a go. My ump used to have a 200mm barrel, and full cylinder and with an m100 struggled to get 260fps. Changed to a 60% cylinder and it got 330fps. Short barrels can be fussy with volume.
Thanks for that good info, @RokSolid… filled a few gaps.
Porting and shortstroking aside, I guess we need to address the air seal issue at the t piece first, with all that good gear in it the LDT should be doing better than 200. The compression out of the nozzle’s there, it’s just not getting any further. If we can get the FPS up and it’s spraying gels everywhere due to horrendous VE then I’d be happy to try a 50% cylinder if BME wants to give it a go, maybe even a short stroked piston too.
With spares available and the original parts intact there’s nothing wrong with a little trial and error fitment.
Thanks for the offer.
We’ll try a few of the options, and definitely take you up on the offer, if thats the path it looks like we need to go down…
Thanks.!
So just had this popup in my emails…
Is this the jinming mp5?
