Barrel Bushing Again
Barrel Bushing Again
My barrel and barrel bearing came today and I was test fitting them into the shroud. The best I could get as far as the measurement between the end of the bushing and the bearing was 15mm with the barrel all the way forward. Is that within parameters? I read on another forum that he was wanting 13mm. With the barrel retracted I get 8 to 9 mm.
Re: Barrel Bushing Again
Didn't know how to edit the post, but when the barrel is retracted it's only 4- 5mm. I had neglected to install the cam piece when I took the initial measurement. Oops.
Re: Barrel Bushing Again
The 8mm retracted and 13mm extended is a measurment we use assuming you are using the shorter 8mm type (MG42 or M53) barrel bearing. The MG3 bearing is slightly longer and the numbers will be different if you use the later longer type (I found that out the hard way).
There are a couple of ways you can measure at different points in order to double check before welding. I like to get set up like I mentioned with the camming peice installed, using a freely moving barrel, 8mm bearing and going stop to stop using the 8/13mm measurement.
You can then double check at some other points if you like. You can also measure from the barrel stop under the front sight to the end of the gun. With a tape measure hooked around the barrel stop to the bushing's end, 19.5 inches seems to be a good number.
Another place you can locate off of for a quick check is from the front of the bushing to the front of the rectangular barrel stop opening on the outside of the shroud (left side) which should be very close to 18 inches. A tad longer I wouldn't worry about, but too short could be a problem.
My Wiselite M53 is about 1/4" short at the bushing and has a peening issue on the bearing to bushing lugs every time I run several hundred rounds through it. I end up cleaning the peening burrs off with a round file at the front of the bushing lug slots. Sooner or later I am going to cut the bushing off and move it foward a 1/4" to fix it for good.
My home build MG3 clone that runs great with no issues has the mentioned measurements, so those are what I'm using on my next MG1 clone build.
From what I've gathered from internet build reading the 8/13mm numbers seems to be a good number taken from an original gun so that's the main one I'd roll with.
Here are a few pics showing what I mean;
8mm retracted:
13mm extended:
Barrel stop to bushing end:
Front of outside barrel stop rectangle opening to bushing end:
There are a couple of ways you can measure at different points in order to double check before welding. I like to get set up like I mentioned with the camming peice installed, using a freely moving barrel, 8mm bearing and going stop to stop using the 8/13mm measurement.
You can then double check at some other points if you like. You can also measure from the barrel stop under the front sight to the end of the gun. With a tape measure hooked around the barrel stop to the bushing's end, 19.5 inches seems to be a good number.
Another place you can locate off of for a quick check is from the front of the bushing to the front of the rectangular barrel stop opening on the outside of the shroud (left side) which should be very close to 18 inches. A tad longer I wouldn't worry about, but too short could be a problem.
My Wiselite M53 is about 1/4" short at the bushing and has a peening issue on the bearing to bushing lugs every time I run several hundred rounds through it. I end up cleaning the peening burrs off with a round file at the front of the bushing lug slots. Sooner or later I am going to cut the bushing off and move it foward a 1/4" to fix it for good.
My home build MG3 clone that runs great with no issues has the mentioned measurements, so those are what I'm using on my next MG1 clone build.
From what I've gathered from internet build reading the 8/13mm numbers seems to be a good number taken from an original gun so that's the main one I'd roll with.
Here are a few pics showing what I mean;
8mm retracted:
13mm extended:
Barrel stop to bushing end:
Front of outside barrel stop rectangle opening to bushing end:
Re: Barrel Bushing Again
Thanks for the info Der Alder. I'm still a little confused though. I'm building an MG3, and the bushing is from BRP. The measurements with the barrel fitted are the best I can get with the shroud I've got. The other measurements you suggested were well within the suggested lengths, but way off from the initial measurements with the barrel test fitted. When I use the 19.5" inch measurement, the bushing is a lot further back into the shroud than my initial experiment. The 18" measurement method moves it further back still. So that is my dilemma. You mentioned a difference between the 8mm and the 308, what would that be?
Re: Barrel Bushing Again
I stand corrected. Just went back and messed with it again, now everything is coming out right. Don't know what I was doing wrong earlier. Thanks again Der Alder
Re: Barrel Bushing Again
Just to clarify, what I meant on the .308 vs 8mm...I refering only to the barrel bearings that are different in some cases.
Other than that with the correct parts they build with the same specs. The thing is the later MG3 type (usually chromed) barrel bearings meant for the MG3 type flash hider is slightly longer than the 8mm style and should be used with that type FH.
If you are going to run a .308 barrel combined with the 8mm type FH'er, I would use an 8mm type bearing on your .308 barrel and the correct sized booster nozzle. That is if you prefer the 8mm look, which a lot of guys do.
The only time the bearing lengths come into play is when you are building and measuring off of them prior to welding. The 8/13mm spec we see used on a lot of build tutorials is assuming that you are using the 8mm type. Now once you get it built you can switch to the MG3 type bearing and FH. On the same token if you do use the longer MG3 type I figure a 6/15mm spec should be about right.
I would just build it using the older 8mm type with the 8/13mm spec then switch after.
Here is a related thread where I posted about it a while back with pics explaining it (down towards the bottom):
http://mg42.us/viewtopic.php?f=9&t=1286 ... g3+bearing
Other than that with the correct parts they build with the same specs. The thing is the later MG3 type (usually chromed) barrel bearings meant for the MG3 type flash hider is slightly longer than the 8mm style and should be used with that type FH.
If you are going to run a .308 barrel combined with the 8mm type FH'er, I would use an 8mm type bearing on your .308 barrel and the correct sized booster nozzle. That is if you prefer the 8mm look, which a lot of guys do.
The only time the bearing lengths come into play is when you are building and measuring off of them prior to welding. The 8/13mm spec we see used on a lot of build tutorials is assuming that you are using the 8mm type. Now once you get it built you can switch to the MG3 type bearing and FH. On the same token if you do use the longer MG3 type I figure a 6/15mm spec should be about right.
I would just build it using the older 8mm type with the 8/13mm spec then switch after.
Here is a related thread where I posted about it a while back with pics explaining it (down towards the bottom):
http://mg42.us/viewtopic.php?f=9&t=1286 ... g3+bearing
Re: Barrel Bushing Again
You've been a big help, thanks.