Bob Long M-TAC Disassembly

[Cdn_Cuda]

My fourth Bob Long in a row is a Bob Long M-TAC, a Marq -based tactical shooter using the Proficiency Engine. Featuring an offset feedneck, aluminum uppers and lowers and capable of using 4c eyes.

[Cdn_Cuda]

First step is separate the upper and lower section. So removing four small bolts you can split the receiver.



Now I need to remove the grip frame to get at the board. And oh look, another battery!



And this battery’s bottom has completely corroded off. Never seen that with a 9 volt before.

[Cdn_Cuda]

So now I can see the board and I can disconnect the solenoid and eye wires.



And now the halves are separated and we can see how the lower receiver connects:


And here is the bottom of the upper have, including the solenoid:

[Cdn_Cuda]

Next step is to try to get at the bolt engine. So to do that we need to remove the stock, so the two body bolts need to be removed. Once removed the bolt engine slides out with the stock as a solid unit.

And now the body is empty, aside from the detents and eyes.

[Cdn_Cuda]

Seems like I’m missing the bolt…. Hopefully it’s in the case. There was a bunch of extras with it.

[RPP]

Yes. Missing the bolt "tip".

[Cdn_Cuda]

It's always just the tip.... I was thinking having a rod in the middle of the drivetrain seemed awfully strange.

[Ecapnation]

Don't lose the oring between the frame and body it's a weird size iirc.

[Cdn_Cuda]

Thanks for the heads up!

[Cdn_Cuda]

Good news, bad news! I have a bolt, but it’s broken. Likely the reason it was not in the marker. Good news is it’s the same bolt as in the Bob Long Victory I am also working on, so I can just use that bolt.

[Frmrspec]

Oof

[Cdn_Cuda]

So here is what the bolt is supposed to look like:



And this is how it connects to the engine, just kind of cupping the shaft.



Can’t say that this is my favourite bolt design.

[Frmrspec]

It always seemed janky to me but when you consider the breech is holding everything inline, it doesn’t seem as janky.. plus screwing the halves together on the VIS is annoying AF

[Trbo323]

It always seemed janky to me but when you consider the breech is holding everything inline, it doesn't seem as janky.. plus screwing the halves together on the VIS is annoying AF

No it still seems janky to connect the bolt that way. The few I've seen I've always been concerned that that's a weak point and here we have proof that it is

Sent from my motorola edge 2024 using Tapatalk

[Cdn_Cuda]

Trbo323 agreed. High rate of fire + janky connection = failure. And it looks like trying to source another bolt tip is a difficult task.

[Ecapnation]

No it still seems janky to connect the bolt that way. The few I've seen I've always been concerned that that's a weak point and here we have proof that it is

Sent from my motorola edge 2024 using Tapatalk

It's only weak if you make it impact something other than paint.

Half the time I saw these break were because some dope shot with a squeegee in the barrel or breech to muffle sound while dry firing

[Frmrspec]

Just don’t take a look at the proficiency engine quick disconnect lol.. that one was like an .08” ball

but in all seriousness it wouldn’t take much to make a threaded version of what you have.

[Trbo323]

It's only weak if you make it impact something other than paint.

Half the time I saw these break were because some dope shot with a squeegee in the barrel or breech to muffle sound while dry firing

Sure but, the majority of other markers don't break the bolt if you have a squeegee all the way down the barrel.

They also don't use this slide on connection thing either

If I were a detective wondering if it's a jenky connection that could be weak, I'd call that a clue

Sent from my motorola edge 2024 using Tapatalk

[Ecapnation]

Sure but, the majority of other markers don't break the bolt if you have a squeegee all the way down the barrel.

They also don't use this slide on connection thing either

If I were a detective wondering if it's a jenky connection that could be weak, I'd call that a clue

Sent from my motorola edge 2024 using Tapatalk

I've never broke this version.... The earlier marq quick release bolts I have, they were even thinner but Bob stopped making that design.

To be entirely honest though neat looking fast and somewhat efficient the marqs in general were atrocious

Each version had so many quirks that eventually they nuked the poppit idea and went fully spool valve....which has its own quirks. While I was sponsored I only used the marqs because they wanted me too, I generally ran older timmys unless I knew there was a photographer at the event

[Frmrspec]

God those old delrin threaded heads were the WORST.. pressure balancing was so finicky.. system didn’t have enough weight behind it to open the valve if your HPR was a little too high, so if you bumped the LPR to compensate, the internal hose would blow off. However if you got the aftermarket valve spring…. Phew… smoothest shooters ever.