Marushin MP40 Rate of Fire & Stuff... (contd)

Post by evil_kot (see also https://mp40modelguns.forumotion.net/modelgun-modifications-f7/marushin-mp40-receiver-tube-rof-mods-t486.htm)

Mark, is it your essay - http://www.mp40modelguns.com/marushin_mp40.htm ? If yes, you say there that “with a little work on the recoil spring, the rate of fire can be changed” (Marushin MP40 kit) May I trouble you to reveal what that “little work” is? You’ve also mentioned that you know where to get a metal chamber to replace the plastic one. May I buy such a chamber from you?

Not related to my question, but I’m dissatisfied with my MP40 kit. It jams like hell. I can seldom get 5 rounds fire, normally it jams after 2-3 shots… The old cartridge is still in chamber when the system is trying to load the next one.

Thanks!

Post by Mark

Hi evil_kot,

Yes, that is my essay on the Marushin.

The rate of fire can be changed by increasing the recoilspring tension by subsituting a spring with a slightly higher rate like one from a MGC MP40. I know that these MGC recoil springs can be hard to find but they can reduce the rate of fire.

Marushin MP40's can be difficult to fire with out jaming one problem is the magazine feed angle, it changes due to the fact that the magazine is usually grabed as a forward grip.

The magazine piviots in the housing and changes the feed angle and usually creates jams as the cartridge angle changes the succeeding cartridges hit the chamber piece at a different angle and this causes the cartridge to hit the bottom of the chamber right at the flat part of the ramp.

So, next time you fire your MP40, push the magazine slightly forward in the magazine housing and this will change the feed angle enough to fix some of the problem.

Another problem is the ABS chamber piece it is too soft and the cartridges wear this part out fast . The only solution that I have found is to make the chamber piece out of steel I make these out of both carbon steel and stainless.

I didn't plan to sell them but I have sold both of the prototypes that I have made sofar! But I can make one for you but, they are expensive at $65.00 for the carbon steel version and $75.00 for the stainlesss steel...

As for the cartridge that is left in the chamber that is usually caused by the extractor not grasping the cartridge case hard enough to extract the case you might check the extractors spring tension.

Post by evil_kot

O! You saying the recoil spring tension should be increased. What if I just stretch the original Marushin spring by hands? What do you think, will that help or I’ll just ruin the whole thing? As for the metal chamber, I’ve been expecting the price as about you have mentioned. My chamber is relatively in good shape so far, but, If you do not mind, I’ll ask you for the metal one when mine go bad.

Thanks!

PS: Mark, no offence, but you should charge modelgun makers for providing 24x7 technical support

Post by Mark
I don't recomend stretching the recoilspring as it will damage it! not increase the tension...Replacing it with a spring with more tension is better..

I would be happy to build a new chamber for you when you need one just let me know when you need one.

Well, as for the tech help, if I could speak/write Japanese I would ask them for more information on modelguns! I don't know if I would charge them anything for my services though..