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Select fire conversion for M249


ardrummer292

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You would need to completely replace the gearbox, as in rebuild the gun take a V2 or V7 gearbox.

 

Or buy a support gun based around a V2 gearbox like a Shrike or something.

The stock M249 gearbox is very basic inside, no cut off lever or trigger trolley, just a microswitch turning the motor on and off.

Jim.

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G&P M249s are based on V2 gearboxes. You could probably add semi auto functionality there with ease. If you allready have an A&K it's still possible with a programmable mosfet, no way to add a physical switch tho.

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12 hours ago, Tarr said:

You could probably add semi auto functionality there with ease. If you allready have an A&K it's still possible with a programmable mosfet, no way to add a physical switch tho.

 

I recall seeing a guy at my local field using a CA/clone Minimi with semi auto. He appeared to be using the safety as a fire selector. Any idea how that might be possible? I'm sure it's some sort of digital fire control, but I'm stumped beyond that point.

 

I wonder if I could program the WARFET installed in my Minimi to help out with this little project.

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Most programmable mosfets detect the one turn of the sector gear with a microswitch against the little nub that normally moves the cutoff lever. You could adapt a mosfet to the m249 layout for the cutoff function.

Same goes for the selector switch, its just a microswitch that needs to be tripped, the safety bar could do that if you place it right. 

Shame there is no ready made solution for this as far as i know but it can be done with a bit of soldering and tinkering. 

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Well there is no easy way to do this, the A&K gbox was never intended to have this feature. A Gate WARFET wouldnt work. You have to have some way to detect a cycle and the WARFET depends on the cutoff lever to do that. Since a cutoff doesnt have anything to "cut off" like in a v2 gearbox the only real option is a custom fitted computerised mosfet that uses microswitches to detect a cycle.

It can be done if you are determined enought but bottom line it's probably more efficient to just get a sidearm for those cqc moments, getting a mosfet that can do this and modifying it would cost about the same :)

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I have used a number of MGs indoors, and it is definitely less manouvreable than a carbine/PDW/SMG, though not less than anything longer than an AK47.    

 

TBH anything is possible, the question is how flexible are your field rules to having an MG class rifle indoors event on semi-auto.  TBH with speed triggers today, semi might as well be full auto.  

 

Putting a programmable mosfet seems to be the best way to go about creating select fire on the MGs.

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I'm not fussed about the bulk of the gun. As long as it chronoes within rifle limits and is actually capable of semi auto, the field doesn't care what it looks like. A pretty fair approach, if you ask me.

 

Blade/double triggers are banned at my local, so absurd semi-spamming is infrequent.

 

I'll give the project some more thought. As it stands right now, I'll likely continue to keep my MGs in reserve as specialty weapons for open terrain fighting.

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  • 4 months later...

Bit of a necropost, but I figure an update is in order.

 

I ordered a Burst Wizard, which I intend to program with a 1 round "burst" and a 1 second delay. This will manifest as such:

Upon pulling the trigger, 1 round will fire.

Keeping the trigger depressed results in no additional rounds being fired for 1 second.

Keeping the trigger depressed longer than 1 second results in normal full auto fire.

 

This effectively converts the trigger into a 2-stage setup, with the difference between stages dictated by time (rather than distance pulled). I believe the 1 second delay removes any possibility of me accidentally full-autoing people in close quarters. I'll do some testing to ensure that this assumption is correct.

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  • 2 weeks later...

Received and installed my Burst Wizard 3 today. My thoughts...

 

Hard-wired installation is a snap, especially with the dual signal wires included. My Minimi was already wired for a Gate WARFET, so the extent of my "hard-wired installation" was unplugging the WARFET and plugging in the Burst Wizard. Absolutely brainless install.

 

If your gun has a high rate of fire, getting the 1 round burst setting to only fire one round will probably take some work. Here's what I went through:

- Using command 2, I set the burst length to one round. Upon testing, I was getting 2-3 rounds per burst. Damn.

- Using command 7, I set the sensitivity to the highest number, which is 19. I was still getting 2-3 round bursts. Double damn.

- Using command 11, I set the burst length to 30 ms. Still got the occasional double cycle. Better, but still damn.

- Using command 11 again, I modified the burst length to 24 ms. Consistent single round "bursts" with crisp trigger response. Perfect.

- Please note that, if you have to manually set the burst length, yours will almost certainly be different than mine. The correct burst length to fire a single round depends on battery voltage, motor type, spring strength, gear ratio, and a million other things that are impossible to predict. I actually had to change my burst length when I downgraded springs (27 ms was perfect for a Guarder SP120, but 24 ms was just right for a Guarder SP110).

 

The stock 0.6 second delay between burst fire and full auto is too short to be safe in CQB, in my opinion. I really don't want to accidentally lace anyone up at close range, so I used command 3 and set it to 1.0 seconds. A bit overkill, but I'd rather be safe than labeled an *albartroth*.

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  • 2 weeks later...

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