I can't add to the propane discussion, but I did get to paw at one.

They're physically smaller than a real 870, and it's noticeable. With my hands being the size they are (large but not huge), it's borderline uncomfortable. Somebody looking for the best facsimile of a shotgun will be disappointed. The ergonomic issues therein can be fixed by adding a pistol grip, but they'll have to be made for this shotgun as real wood kits etc clearly just aren't going to work.

HOWEVER, the gun itself feels goodamn solid. Fit and finish is TM through-and-through. The pump action just rules. I have no doubt that this gun will become the golden standard of skirmishing shotguns. It's just... small.

Does anyone have further insight into it's guts? Could this reservoir issue be bypassed completely in favor of a remote line? Running one of these on a Co2 tank would be pretty ballin'.

I've had propane in my gas tank for almost a week now, and there has been no signs of bulging or warping. Tank goes in and out smoothly.

As for the gas resevoir, it most definitely looks like a candidate for a regulated HPA tank. I'm going to be dismantling the gun this weekend to try and fit a custom handguard to the foreend. I'll try to document, the process and get some photos of the breakdown.

I have yet to skirmish the gun but it's a lot of fun to toy around with. Range and accuracy are really good with both 3-round and 6-round modes.

Even on a cold day the gun was performing very well on propane, not so much on duster. I only managed to get a few shots off on duster in the cold weather (15 deg C).

Some good how to take down info in the Arnie's Airsoft thread.

Got mine; just in time for the weekend!

First impressions. Awesome! Wish it was louder though.

Will you use propane?

Depends on ambient air and how sensitive the people I'm shooting are.

No worry about the flex issue?

The gas tank will be okay as long as you aren't storing it fully pressurized and then under hot conditions. If you vent the gas after you're done it should be okay.

I have noticed a slight flex to mine after having it been pressurized for over a week on propane. I put it in a vice and squeezed it back with no issues and it still holds gas. I will avoid storing gas in there from now on.

In colder conditions, you almost have no choice but to use propane, on duster you don't get very many shots and it's horribly under powered with duster. You may be able to get some better performance using duster if you chilled the gas tank first and warmed the duster can before filling. I haven't tried that yet.

I've had propane in my gas tank for almost 2 months now. So far, my gas tank seems to be fine. Will let you guys know if I have any trouble with it.

I wouldn't consider 15C cold....but OK. More like 0C to 5C.

Reminds me of my old Maruzen M870 - I hope this model has more mileage on the seals than that one.

Pressure tank defect.
 

I just received TM 870 and under close examination I see some issues with pressure tank. Basically what you see is a small irregularities, biggest one is 1mm deep. I would not mind, but this is a pressure tank, and this look like a structural weakness in it. Is it?

I might send that tank back.

I really want a shell saddle on the receiver; nothing on the stock please.

If you use propane, like p.presh said, don't storaging with fully gas filled, the pressure of propane could push the end wall of the tank a bit wide open. Would it become trouble in long run, may be? Most or all of the Japanese airsoft are designed for HFC-134a, around 80psi. But propane is 130psi. Pot metal may not strong enough to hold it in shape. This gas tank is too wide and long inside, shouldn't only three lock pins for support, should at lease using one screw at the centre to hold the wall in place. If you just using HFC134a gas would be fine.

Are they any aftermarket propane tank going to be released?