Cap question and Modifications

Post by ljerr2

I have purchased an MGC M4A1. It is new, but it doesn't really fire that well on full auto consistently.
I am running Marushin 7mm caps. Would the MGC 7mm caps be better?
Is there anything to check on the gun that might be leading to this? IE, I have heard sometimes you need to do some tinkering? Filing?
How about lubrication?

Thanks for any help.

Post by Mark

Hi ljerr2,

Welcome to the forums!

The MGC M4A1 usually is a very good performer out of the box..It's rare to hear that one has a problem (or so that i have heard) Sometimes the magazine lips have burrs on them that catch on the cartridge cases and slow down the action. These burrs can be removed from the magazines lips with a small file or whet-stone. Also, check to see that you have the propper amount of silicone oil in the action as lubrication is the key to propper functioning.

Also, place a small amount of grease inside the cartridge when loading the internals. This will help the cap and the "piston" to slide and this will help function.

Personally, i prefer the MGC caps to the marushin caps as they don't "spark" when they are fired. (the caps are all manufactured by Kane Cap in Japan who is by the way the only source of 5/7mm caps) the power seems to be the same as the amount of phosphrous is identical in either the Marushin or the MGC caps.
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MGC MP40 Marushin MP40 Nakata MP40 TRC MP40

Modelgun manufacturers, past and present:CMC,CAW,Hudson,HWS,LS,MGC(R.I.P. 1960's~2007) Marushin,Marui,Kokusai,Shoei,Tanaka and Western Arms