Converting a G&P to a MK12 SPR DMR

[Matt.2504]

Hi everyone, 

I’m looking at converting my G&P M4 to a MK.12 SPR inspired DMR. This meaning I am going for an overall similar look but not going to be a stickler for the appearance to be perfect.

I have all the parts I need for the externals but despite having been an airsofter for about 14 years I am very inexperienced with internals.

On the assumption that the internals are all stock G&P, what upgrades would you advise to convert to a DMR? is it as simple as upgrading the spring and barrel?

how should I lock it to semi? For ease should I do the grub screw locking method / hideous glob of superglue?

FPS wise I am aiming to be at the 400 mark

any advice would be appreciated 

cheers

Matt

 

[Rogerborg]

Hi. You don't need to do anything other than a bigger spring and lock it to semi somehow.  Bear in mind that stock CYMAs shoot over 1.5J / 400fps, and that's pretty standard for Murcan fields, so this isn't extreme by any means.

What I would do is:

Radius the gearbox if it's not done already.  YouTube can provide videos.

Get the shimming and air-seal as good as you can.  Maybe think about an o-ring nozzle, a double-o-ring cylinder head, and replace and/or stretch the stock piston o-ring, add more ports to the cylinder head, and get it all silicone greased up.  A full cylinder will give you more air volume to play with if you're going for a longer barrel - I splashed on one.

Locking to semi is down to your local fields.  Some might be OK with a screw, some will want it selector locked, some might even want a mosfet with a 2-second delay (although you can of course disable that as soon as you've chronoed).

The way I went with was to remove a piece of the selector plate - I bought a spare, to keep the original aside and intact.

This bit here.  You only have to remove enough so that when you slide it to full auto, it doesn't push the cut-off lever.  Just get the gearbox out, slide the selector between semi and full a few times and watch how it interacts with the cut-off lever, and it'll be obvious what you need to remove.

View attachment 89251

Then barrel, hop rubber and nub.  I just run a Maple Leaf, no need for flat or R-hopping at 1.5J.

The second last thing I'd do is the spring, after everything else is as good as you can get it, because all of that will give you a better gun anyway, and you'll want the air seal optimised and the piston and barrel volume fixed.

The last thing I'd do is the motor, and only if it's struggling to pull the spring.  One problem with semi-auto locking is that you might get a lock up, which a meatier motor can help to avoid.  Again though, 1.5J isn't that big an ask.  You'll get a faster response, but with the time of flight a few more milliseconds isn't as critical as in CQB.

No need to go crazy with any of this stuff, you're going to be limited by all the usual real world factors, so just getting near 1.5J with heavier BBs and decency consistency is where you want to be.

 

[Matt.2504]

Thank you very much, your response was very helpful when I get around to working on it.