The Real and Dirty on the Tokyo Marui M870 Gas Shotgun ( hpa tm m870)

Discussion in 'General Airsoft Discussion' started by 258eagle, Jul 27, 2015.

  1. 258eagle

    258eagle New Member

    21
    0
    Bear
    Not much is said out there on the TM m870 shotgun, issues, and modifications. I wanted to share this information with others because most of my searching came up empty!

    So quick review-

    Gas shotgun has a true range of 150 ft on 3 shot!

    TM quality

    Takes those cheap spring tri shot shells

    Tank gets me about 7-8 shells worth (way less on 6 shot mode and only 50 ft range)

    Nothing new here that you cannot find elsewhere, I want to get to what it is like to own one!

    The real deal;
    Propane is too much for this shotgun, green gas is too much for this shotgun, 6 shot is worthless, no confidence in the gas tank, and the shotgun leaks often. Constant disassembly and regreasing are required.

    It did not last the entire game at OLCMSS Freelander
    [​IMG][/IMG]

    But when it worked it was too much fun.

    So what makes this shotgun worth owning? POTENTIAL
    If one can get a reliable power source and stop the leaking, this individual would be left with a truly skirmishable shotgun that is no longer a novelty item but a force on the field! So i attempted this because a shotgun that wasn't a joke is something I wanted.

    Here is how I achieved this;
    HPA!
    and it was incredibly easy to do. there are a few routes to go; $200 angry gun m4 stock with a hpa fill nozzle replacement(ugly and expensive$$$ route!) or mod your current gun to hpa for $20.

    Here is how I hpa'd my tm870 maintaining the original stock and maintaining the potential to return to factory gas set up.

    Step 1- Split the original stock in half (be carefull of glue, use acetone or heat)
    [​IMG][/IMG]

    Step 2- Cut out old 8mm tubing and replace with a desired length 8mm tube(easy to find 8mm plastic tubing online, i got mine from amazon)
    Step 3- Get a 8mm 1/8" threaded fitting
    Step 4- Get a 1/8" threaded male quick disconnect (i got mine from amped airsoft)
    Step 5- Drill 8mm hole in the bottom of the stock grip.

    What these steps look like:
    [​IMG][/IMG]

    Final steps- reassemble stock (glue if necessary)
    [​IMG][/IMG]

    BAM! HPA shotgun for about $20 in parts.
    [​IMG]

    Why hpa? if you live an area with more than one season then the gas tank will not be reliable or usable all year long.

    Next Issue: LEAKS! So many leaks!
    My only leak always came from the output release valve inside the "gearbox" shell of the shotgun.
    [​IMG][/IMG]

    So i did the typical move and bought the cure-all SAT output valve!
    [​IMG][/IMG]

    Well it didn't work at all (this was prior to hpa). I thought this was me using propane so i took everything apart and greased everything. I only used green gas after this and still leaks! SO disassembly and grease again... Next came hpa at 80 psi, the shotgun performed terrible at this low psi and after 3 games leaks! it emptied my air tank. So i took it upon myself to come up with a solution.

    The Leak Fix;

    I was never happy with how the valve, the portion that was struck by the hammer, returned to the ready position. It did not seem very firm, and the valve failing to return to close is what was causing the leak. So i decided to put a stronger spring in the output valve. I took 4 coils off the factory tm output valve spring and installed it into the SAT output valve. the Valve returned very firm now. I was afraid this meant I would need a better hammer spring and go on a trial and error phase but nope! it worked and worked like a dream. I am 500 shots/slamfires in and 100% performance. I am going to op red storm east soon and will report back.

    What would have I done differently?

    Never gave $80 of my dollars for the SAT output valve, instead go out to a local hardware store and get a stronger spring for your factory tm output valve and i believe you will be just fine.

    What is it like now?
    Epic, I am running 95 psi, getting 150 ft with .28g bbs, and 330 fps w/.20g bbs. It was very effective to use and great fun! No longer fearing of running out of gas means i shot a lot! and it didn't leak a bit. I shot 40 shells today and had a ball. Prior to hpa i never would have fired so freely.
    [​IMG]
    [​IMG]

    Please please share this because others need to know there are hpa options other than the $200 angry gun option or expensive mod shops.
     
    Last edited by a moderator: Jul 27, 2015
  2. Rushin

    Rushin Well-Known Member

    3,926
    32
    Kalamazoo
    Thanks man! My friend has a shotgun, and when it works, it's amazing. And when it doesn't, (quite frequently) it's frustrating and annoying. He's planning on going the angry gun route because he likes the look but I'll definitely point him towards this guide.
     

  3. Alpha_Wolf

    Alpha_Wolf New Member

    84
    0
    Thanks for making this thread . The m870 is fearsome when it's working right and when it's not...well

    Exellent post over all. Sadly enough I've never heard of anyone buying the SAT valve and having problem free improvements . It's issue after issue. Which doesn't excite me for their new gas tank.

    Question : what are you thoughts on the standard TM output valve. Would you still change the stock and if so how is the proper way for the best results. I've ordered an %150 hammer spring in anticipation

    Edit : is the pro arms output valve any better ?
     
  4. SomewhatInsane

    SomewhatInsane Active Member

    156
    26
    Augusta
    I have some parts to use the setup you've described here on the way. Great post and a ton of useful information! :D

    As others stated above... And is so true, when this gun works it is an absolute workhorse on the field, however... When it fails, o-so-frequently, it is disappointing and frustrating.

    Hopefully we can keep this thread going as a bit of a compilation of information. And helpful tips and tricks.

    After I put mine back together I'll edit some stuff in!
     
  5. 258eagle

    258eagle New Member

    21
    0
    Bear
    Update:

    I am +10,000 rounds through the shotgun running at 115 psi and I report ZERO issues. I continued this project assuming I would need to spray oil in every few hundred rounds, do a tear down & grease internals every 5,000 rounds but nope! I have converted the shotgun to hpa and put in a stronger valve return spring and the gun is performing as it should. I have used this shotgun with great success at Lion Claws Operation Red Storm East and solely use this shotgun in my weekly skirmishes.

    [​IMG]

    I continue to improve using this gun, there are some difficulties using a manual operated shotgun vs polar stars but it is a blast.

    I have found that Six Shot mode is not entirely useless, in fact in very close quarters battle it is down right dirty, lol.

    [​IMG]

    Six shot is devastating in cqb but once you exceed cqb at any level it is back to being useless.

    More Upgrades;

    I have been harassed since day 1 about cutting the outer barrel down, selling to get a breacher, get an m4 stock; blah blah blah.
    There is some truth in what they say, the inner barrels on the full length tm870 are the same length as the breacher version(260mm).
    Lastly I was impressed with the performance but knew that just a tad better would send this shotgun over the top.

    I present to you the Wii Tech M870 Long Inner Barrels Set (6.03x380mm)

    [​IMG]

    First outing didn't go well, I saw no increase in performance. I then switch from .28g or green .25g bbs to white .25g bbs and that was key. The fixed hop up doesn't handle .28g bbs well; and my green bbs were not visible. When i switched to .25g white bbs and saw the distance I was amazed. The improvement showed on my next skirmish as I could engage all those who engaged me. No longer did I have to wait for enemies to come in range. The grouping is better but not too noticeable as the grouping was always good.
    [​IMG]
    Favorite part of this barrel set is the spacers/holders included with the barrels. A little more difficult to install but the spacers are so solid and eliminates that annoying nut strip on the ammo tube ring. After installation there is zero barrel wobble and it is by far one of my favorite aspects of this upgrade.

    -Secondly I got the wii tech rail handguard
    [​IMG]

    It is an exact clone of a troy trx but changed to fit a shotgun. I love that this replaces the old set up. I can now easily re tighten the arms without disassembly, the arms often come loose. The rail can be removed without any diassembly and reveals screws to allow a lot of gun disassembly without dissembling the barrel assembly(a good amount of time saved here). the bottom rail does not remove like a real trx so in the future i will be getting a trx and cutting it to fit for an even slimmer handguard. the rail hooks onto the pumps arms like any rail attachment for a trx, spacers through the trx squid holes and screws into the arms. Very simple and thought-out.

    Wii Tech is a hong kong airsoft company that CNC's their own stuff. Never heard of them before but their products have been of superb quality and I love them.
    [​IMG]
    [​IMG]
     
  6. 258eagle

    258eagle New Member

    21
    0
    Bear
    pro arms appears in every way to be the same exact product just different color.

    If i had to do it again I would not buy a new valve, just get a stronger valve return spring and you should be good to go. I personally like the stock (i do wish it was slightly shorter as i have short arms) and the only thing i will be changing is throwing in an amped line inside the stock, twice now i had crimping issues.

    I am done with green gas, weather here on the east coast is too fickle, either blazing hot or blistering cold. leaks were never a result of the tank so I do not know how a new tank could fix anything. my tank did leak but just like a gas pistol, remove the fill nozzle and grease them.

    I really hope so!! so little real info about this gun out there. Youtube celebrities say it is perfect, this gun quite frankly sucks in stock form but a few simple mods makes this AMAZING!
     
  7. Sillypancake

    Sillypancake New Member

    173
    0
    Kansas City
    Thank you bumping this thead; your shotgun is just...wow. Hey, by the way, what's your home address, and what's your daily schedule during the week? Just curious... ;)

    Lol, but seriously good job. Do you have your own YouTube channel? If you don't, I think your videos would be amazing.
     
  8. Bio1_Hydra

    Bio1_Hydra Member

    378
    2
    Williamsport
    I agree that'd be pretty fun to watch
     
  9. SomewhatInsane

    SomewhatInsane Active Member

    156
    26
    Augusta
    You've got a wicked looking build man!
    I'd definitely watch gameplay footage. Still need a regulator for mine! Otherwise it's good to go.
    Any idea what your max range is right now after installing that Wii Tech barrel set?
    I'm sort of intrigued by those. Seems handy of it increases your range that much! :D
     
  10. 258eagle

    258eagle New Member

    21
    0
    Bear
    I may have just recently got a go pro :cool:

    i'd say 150 ft with .28g bbs but the bbs droop quite a bit and feel like they just barely get there. Now with these barrels and .25g I can hit a 12 inch wide tree trunk at 150 ft, all three bbs and they peg the tree hard. I'll do some more testing on max range. But with these barrels and .25g bbs i'd confidently say range is topped at 175 ft. (i mean some bbs out of about 3 shots will get to your target).
     
  11. moomoose

    moomoose Member

    852
    2
    Eagle
    .... I seriously JUST talked myself out of buying one.... AND now I REALLY want one -_-
    Seriously though great thread, there was some info here that I hadn't heard anywhere else
     
  12. Wingman703

    Wingman703 Moderator Staff Member Moderator

    5,540
    525
    Atlanta
    I just received mine. I'm in love. The rack is SOOOO GOOOD OMOMGOMGOGMGOMGOMGOGM
    Need shells now...
     
  13. SomewhatInsane

    SomewhatInsane Active Member

    156
    26
    Augusta

    Dang. That's quite a bit better than what I'm getting. With .25's I've been getting around 130 ft.
    I really wanted to use .3's but the hop up in it's stock form doesn't seen to have the loft for them...


    BUY ONE.




    Welcome to the 870 master race.
    M4's: meh.
    Ak's: meh.
    Mp5's: meh.
    Bullpups: meh jk bullpups and AK's are <3
    But TM 870's are where it's at...
     
  14. Holy_Schmidt1796

    Holy_Schmidt1796 New Member

    14
    0
    Chicago
    I cant thank you enough for all the help u have given me. I'm the jerk that has been slamming you with questions on Instagram. I have spent hrs over the past few days with multiple techs from evike asgi and amped. Here is what I have come up with I purchased a slip connector for a 8mm air line to an 1/8 npt thread, and a amped airsoft AGL with a 6mm slip connector that I will be unthreading and putting the 8mm connector on.
     
  15. 258eagle

    258eagle New Member

    21
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    Bear
    Let's start posting progress photos guys :)
     
  16. Holy_Schmidt1796

    Holy_Schmidt1796 New Member

    14
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    Chicago
    I would but I haven't started yet. I am waiting on that damn slip connector :mad:. I have literally ordered every piece of HPA gear from the tank, regulator, line and the AGL. However, its all sitting in my armory or closet, one or the other because that stupid slip connector has to come from china. The connector will hopefully be here on Oct, 17 to Nov, 3 and you can bet you butt it will be built that day and photos later that night because it shouldn't be to hard.

    Eagle-That clear line you used for your macro line when it goes under my steel rod it does slightly kink my macro line should I be concerned or just it be. I'm going to sand a bit out of the stock to make a little grove so the macro line has a little more room for less kink of the line.

    Eagle-Did you use some kind of epoxy to put the stock back together? I ask cuz the barbs that held it together are no longer doing the job, and I never plan on opening this stock again because I have 2 stocks one for green gas and one for the HPA.
     
  17. 258eagle

    258eagle New Member

    21
    0
    Bear
    It squeezes the line a little but never kinks.

    And yes i used super glue to hold it all together. It's been doing fine.

    I will be opening the stock one more time to install the agl line.

    If i had another stock to mess around with i would mess with using bolts to close the stock so that i can always access my lines.
     
  18. 258eagle

    258eagle New Member

    21
    0
    Bear
    Here is some footage from yesterday.

    [ame="https://www.youtube.com/watch?v=XvAECISoo9I"]https://www.youtube.com/watch?v=XvAECISoo9I[/ame]


    [​IMG]
    [​IMG][​IMG][​IMG]
     
    Last edited: Oct 20, 2015
  19. ThePinballWiz

    ThePinballWiz Member

    616
    2
    Buffalo
    Thanks for the excellent write up and updates. An 870 tac is now the next gun I'm going to get.
     
  20. Holy_Schmidt1796

    Holy_Schmidt1796 New Member

    14
    0
    Chicago
    ImageUploadedByAirsoft Society1446790915.808180.jpg time for me to join the party