www.MG42.us

I know that this has been beaten to death over the years, but does someone have a WORKING re-build on a 43/53 kit that can tell me the length of the main spring they are using??

I am down to that point. I am using one of Pirates bolts and a FAL grip stick conversion. I will be using it with both 7.92mm and 7.62mm ammo. I am not certain that the spring is different for either ammo.

I have studied John's manuals on the post war weapons and in the one for the MG1 and MG2, they call out a different recoil booster but do not bring up using a different spring.

I may have to get a 7.92mm booster as both of mine are 11.5mm, which is shown for the 7.62x51. The manual shows a size of 14mm for 7.92mm so will have to get one or drill one of mine out.

Thanks for any info,

Chuckm

There is only one spring made as the main (recoil) spring in an MG42. Caliber isn't an issue. You may find that a small nozzle hole is better for your semi. The manuals are good for specifics for a full auto only. With a semi, everything in the book becomes a starting point/suggestion instead of the final say.

With a semi build, the spring needs to be as absolutely long as possible. As each combination of built parts can be slightly different, there is no single answer for the exact length of the recoil spring.

Cut only enough off of the recoil spring so that the bolt will go fully rearward and hit the buffer. It actually needs just a wee bit more than that cut off, because the buffer needs to compress a little when it stops the bolt, and it uses the buffer spring compression to help the bolt forward again, it isn't all about the recoil spring. Maybe one wrap more than what it needs to have the bolt hit the buffer will do it. It may take a little more. If the buffer can't do its job, you'll lose recoil energy by jamming the spring coils together, and the gun won't function correctly, besides beating the spring to death.

Each home built semi 42 is a custom, non-standard piece, and requires a customized, correctly fitting recoil spring. It doesn't hurt to have a couple springs, because you may cut one off a bit too much, or you may beat it to death by not cutting off enough of it. The second one is good for reaching the sweet spot for your gun.

And then there is another main spring - it's made by brp

http://www.brpguns.com/products/MG42-Se ... pring.html

It's what I'm using. Also the above from John is great advice using the old original style spring.

Later 42rocker

I would go to RTG and get about 3 used recoil springs (they are cheap) - like $6 last I knew.

I have 6 springs in my semi-auto tuning kit. Just like boosters it is not always one size fits all. A lot will depend on what B/C you are running, ammo, how tight the gun is, belts, etc.

My WLA M53 recoil spring is about 13.5" long. My home built semi MG3 clone with BRP B/C is currently running a 12" spring. Both work fine in those guns.

I would start with 12" spring and cut another with one coil more and another with yet one more coil assuming you have a standard length receiver. If it short strokes with the longest, switch to the next smaller one. Make sure too that the one you try isn't too long as it will coil bind and not allow the long semi B/C to move fully back. A hand cycle check with the top cover up can confirm this.

I cut mine with a dremel. Keep the closed (uncut end) towards the B/C. Another thing I like to do is color code mine with a dab of paint (red, green, white, blue). Helps me remember which works best while swaping them around at the range.

You can try the BRP spring as well. I have one in my kit and it works ok, but I like the added zip of stripping the belts using a cut original spring.

Its really just trial and error.