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Fixing up MTR77 NP
https://www.airgunforum.ca/forums/topic74927.html
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Author:  Anatine Duo [ Fri Dec 30, 2016 10:08 pm ]
Post subject:  Fixing up MTR77 NP

Starting with the obvious, remove horrible burrs everywhere! Lube linkages, fill random holes. Tiny bit of silicone grease on the slightly-damaged-from-assembly piston seal. Checked transfer port (about 1/8" diameter) and poked burr in, removed.

Looks like a solid 900 fps with 7.9 gn copperhead. 770 fps with 10.5 premiums. Quiet with the 10.5 gn. I forgot to check the breech sealing (Crosman claims this is an 18 ft lb gun I think so maybe there is more speed to be had)

This gun is surprisingly solid feeling. Muzzle heavy. 40lb plus (bathroom scale) peak cocking effort seemed to smooth out within 3 shots. Trigger mods to come... not the worst trigger I've had but very bad. The MSRP is kinda outrageous I feel but I got this at a boxing day sale with a Christmas gift card from work so it feels like a huge bargain to me.

My first gas spring!

Author:  Joolz [ Fri Dec 30, 2016 10:11 pm ]
Post subject:  Re: Fixing up MTR77 NP

Hi, was this a Cabela's special? Cause my local store said they only have the sub Pal/under 500 fps version.
You by any chance using the open sights? If so, any issues sighting them for basement shooting?

Author:  Anatine Duo [ Fri Dec 30, 2016 11:38 pm ]
Post subject:  Re: Fixing up MTR77 NP

Yes it was from Cabelas, the 495fps version. I was hoping the detune was simply the piston bleed hole... confirmed on mine.

I will be using the peep sight on the flimsy handle until I can shoot it well... so far all my shots have been over a relatively uncooperative Chrony

There is a lot of glare indoors on the peep.

Author:  Joolz [ Fri Dec 30, 2016 11:47 pm ]
Post subject:  Re: Fixing up MTR77 NP

Oh so it was a simple hole plug huh? Please do let us know what fps you get out of it.
The peep sight is the main reason for getting this rifle, as it's rare to find a low cost gun that doesn't come with these ridiculous fibre optics sights. But the issue most seem to have with the MTR77 is the inability to sight them for close range. Apparently the rear sight cannot be elevated high enough for 10m shooting, as the POI is too far high. Have you experienced this?

Author:  Anatine Duo [ Sat Dec 31, 2016 9:13 pm ]
Post subject:  Re: Fixing up MTR77 NP

I had that problem with an airsoft M4. Must be common when the sights are 2.5" above the bore. Fine for 5.56 on human size targets but the geometry wasn't designed for airguns. Anyway I cranked the rear all the way up and the front down. I think if it does zero at 10m it will be ridiculously high at 20m but I'll try and get some data.

Back when I used to shoot 100 yards with 4x scopes I didn't shoot at my high-visibility aimpoint... shoot out the bull and then all you have to aim at is a ragged blur instead of a nice orange circle. It's one solution for informal paper shooting... if groups are good and where you think they are, then actual bulls will come when you need them.

Author:  Sid66 [ Sun Jan 01, 2017 7:19 am ]
Post subject:  Re: Fixing up MTR77 NP

Well it is good to hear you have a "normally" detuned gun instead of the bored out transfer port like mine.I removed my fake suppressor and shortened barrel shroud 6 " harder to cock but not 40 lbs worth.good luck

Author:  Anatine Duo [ Sun Jan 01, 2017 2:06 pm ]
Post subject:  Re: Fixing up MTR77 NP

Some more data:

at 10 meters it does zero with Crosman 10.5 and ironically has the same zero with the better-grouping and much lighter Copperheads... but conditions sucked (didn't even notice the trigger due to wind and glare) so that was only 9 shots total... could always file down front sight if needed.

It likes Crosman 7.42gn wadcutters for speed giving solid 950s fps/nearly 15ftlb (many shots) UNTIL...

... in my impatience to try a 5.2gn pellet for speed I made my own from dowel and masking tape... not good idea, tape shredded and the Chrony registered 718 fps suggesting a simulated dry fire. After that the 7.4 gn was in the 920s for another dozen shots. Looking forward to a teardown and see what that piston seal looks like.

Sid we'd love to see the dead space in that transfer port eliminated!!! I'm sort of looking forward to a transfer port fill job... but I know it sucks when you rather be shooting

Author:  Sid66 [ Sun Jan 01, 2017 5:38 pm ]
Post subject:  Re: Fixing up MTR77 NP

It has been a full week for sure.I bought this on black Fri. and my wife intercepted my package and kept it till Dec,25.I have have torn it down to all its individual parts and put back together 6 times so far {not getting results so double checking my work}and still manage to put about 700 pellets through it.I like the gun seems accurate at 35 ft in my basement I have already made a couple inserts but having a hard time drilling into a gun 1 week old.LOL.I read your transfer port was close to 1/8 so 95% sure my big port is the issue.

Author:  Anatine Duo [ Wed Jan 18, 2017 2:31 pm ]
Post subject:  Re: Fixing up MTR77 NP

tried another (7.90gn) pellet and could not get poi high enough to zero at 10m, which sucks for pesting... when I find a pellet it likes I'll work on the sights. Still room to file the front post down.

Not the best to learn tuning on... many screws!

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