MG3 Heavy Bolt versus MG3 Regular Bolt

[RevWarGuy]

Hello all! I am new to this forum. I have just finished looking through one of the "sticky" posts full of diagrams. I found two different bolt diagrams one right after the other. The first one was labeled MG3 Regular Bolt (I think) and the second one was labeled MG3 Heavy Bolt. So I have now determined that I have a MG3 Heavy Bolt. However, it looks like the bolts in the other MG42 diagrams as far as the shape of the parts and all. Are there going to be any differences in making the Semi Auto mods to this model bolt or to any of the other parts the bolt operates in or the other SA parts - bolt stop, trigger assembly, etc.?

Thanks!

RWG
Active Duty
US Army

[JBaum]

The heavy bolt is used (with the special buffer for it) to reduce the rate of fire. It does that by using more recoil energy to overcome inertia, thus slowing the action.

Since the semi auto version has very little spare energy to begin with, I would think that using a heavy bolt would cause fail to cycle problems, and would recommend against using it. Beside that, if you use a heavy bolt with a standard buffer, you'll just beat the back end of the gun to death.

[amafrank]

You will find that there are really 3 bolts for the MG42/MG3. The early bolts look like the body has been cast which is a good possibility. I don't remember the exact weight of the bolt/body combo but its somewhere in the 350gm range. The German MG3 bolts were 400gm if I recall correctly and look completely machined. They also have a spring in the feed plunger so that the topcover can be closed with the bolt in any position, a process not recommended for the early type bolt as the feed stud would sometimes damage the rail. The MG3 bolt will work fine in any MG42 though modifying one to use in a semi is a sad waste of a very good full auto part. There are many more MG42 bolts out there than MG3. The last bolt type is the 950 gm Beretta built bolt which was made by Beretta for the Italian army as they did not like the high rate of fire in the MG3 when adopted. The 950 gm bolt is obviously heavy and much larger than either of the earlier types. It is a big square bolt which is as wide as the bolt head from front to back. The lighter bolts have a wide lug at the rear for riding the rails and are narrower in the middle. The heavy bolts are normally marked on the top with PB and a 2 digit date. PB is Pietro Beretta. The heavy bolt does not use the standard bolt catch or ejector spoon and also has the spring loaded feed stud. In the full auto guns the use of a heavy bolt with a light bolt buffer will result in damage to the bolt rails and sometimes other parts. I've repaired a number of these and seen the damage in person. For a semi auto the heavy bolt is really an unneeded part. The modifications to semi would be much more complex and with the extra weight of the bolt the operation would probably be much less reliable. I don't have any of my MG3 bolt pictures on this computer but I'll see if they are still on the old one and post some. In any case the bolts are easy to tell apart once you see them.

hope that helps
Frank

[bulletbaron]

Frank: I am trying to send you a "PM" and all I get is a red lettered statement saying "TOO MANY RECIPIENTS" which I do not understand why. Will you please e-mail me at "admin@precisioncartridge.com"

THANKS Dennis

[weasel]

I use a heavy bolt which I made from 4140 steel. I wanted to slow down the rate that the bolt moved. In semi you don't need the speed. As far as the bolt beating the buffer to death I can't say. Mine is still working. The stock spring is only half the length.

Recoil is still there, yet easy to shoot.

Hi John B, hope everything is well with you and yours.

Weasel

[TactAdv]

I use a heavy bolt which I made from 4140 steel.
Weasel

Interesting. Yea, verily.

Here's some pictures of the "heavy" bolt group from my own Steyr MG-74 as a comparison(std MG3 bolt group on left):




I am curious as to why you left so much open space, milled away, if you wished to add greater mass as compared to the MG-74 bolt body above? BTW, altering spring lengths is usually a scary thing to do; personally, I'd find a different -RATE- spring that fits and functions rather than "clip" an existing spring.......bad ju-ju with all sorts of nasty surprises usually in the long run when you cut springs. YMMV. ;-)

-TomH

[amafrank]

Frank: I am trying to send you a "PM" and all I get is a red lettered statement saying "TOO MANY RECIPIENTS" which I do not understand why. Will you please e-mail me at "admin@precisioncartridge.com"

THANKS Dennis

Hi Dennis,
I haven't had any problems with my PM's incoming or outgoing. I don't know why you can't get a message to me....check to make sure there is only one person listed in the message header before you send. . .

Frank

[kevin917z]

my latest mg42 kit came with one of these different looking bolt cariers It has the spring loaded post on the rear and 4 small holes, 2 on each side of the rear of the bolt carrier. I guess i will mod this to semi auto but is it a rare bolt type i should trade to someone?

[amafrank]

my latest mg42 kit came with one of these different looking bolt cariers It has the spring loaded post on the rear and 4 small holes, 2 on each side of the rear of the bolt carrier. I guess i will mod this to semi auto but is it a rare bolt type i should trade to someone?

It sounds like what you have is a late M53 bolt. Its pretty much identical to the WWII German MG42 bolt but they added the spring loaded feed stud to prevent damage to the belt feed rail. They aren't really rare but aren't exactly common either. I don't know how the semi conversion will affect the operation of the feed stud or if the 4 holes in the back will cause any problems. If you have some question about whether it will work see if you can trade it off to some one for a standard bolt body. The bolt head is the same on all of them as far as operational concerns go.
If you want an accurate answer post a picture of the bolt.

Frank