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Discussion Starter #1
Have my m2 mostly finished up, just at that tedious hand fitting point, everything went together as expected, but there is a serious amount of drag on the bolt, so much that the gun will not cycle. Extracts fired case aprox 2" then not enough energy to overcome drag.

The drag begins when the bolt is retracted aprox 1/2" and all the way back except the last 1/2" of travel. When hand cycling on the bench it damn near takes two hands to retract the bolt. When the bolt is released it has to be pushed very hard to close, usualy by sticking something in the bolt pin hole on the left side and forcing it forward.

I have spent a few hours today studying every possible rub point.

With the back plate off (return spring out) everything is as smooth as glass as soon as the buffer is depressed completely into its housing there is to much drag.

If I pull the buffer out of housing and reassemble gun , return spring back plate etc, everything is very smooth, no binding at all.

With everything reassembled and buffer in place the binding/drag returns. I initially thought it was the accelerator rubbing on bottom of bolt but I can reach in thru slot in left plate with small screw driver and hold accelerator down , its not the problem.

Hopefully someone can guide me in the right direction


Also in the fm it says insert buffer in housing , slot vertical, arrow pointing right and the grooves in buffer body will engage housing so as not to rotate. I dont see anything that engages the slots in buffer to keep it from rotating. There is a 1/4" diameter hole at the bottom rear of housing but I dont see anything on the leaf spring under housing that would protrude thru hole to engage notches.
 

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Richard, make sure that the return spring assembly is not binding inside the bolt. That's just off the top of my head. let me think about this some more and I'll post any other suggestions that occur to me.

Harry
 

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Discussion Starter #3
Its def something to do with the buffer, all is glass smooth until buffer is compressed into housing, spring and guide are free.

With everything assembled in the box , no buffer, butter smooth

With everything assembled in box including buffer, no return spring, it takes two hands to retract and alot of force to close bolt

Will study buffer shortly and figure this out
 

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Please let us know what you come up with. Some others may be having similar buffer troubles.:(
 

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1) Explain to us how you headspaced and timed the gun. Yeah, I know you havnt actually fired it yet, but I want to start with the simple stuff.

2) With the backplate off and the recoil spring REMOVED, is the charging operation taking as much effort? Many guys dont realize that charging a M2 is not a nice, controlled act..... you have to rip that entire charging handle back with your entire shoulder. Charging a M2 with a simple 'biceps curl motion' is impossible.

if all the above is done correctly, then your binding is somewhere in the cocking lever assembly. Ive seen them put in backwards and its a royal mess.

EDIT: Im drunk and didnt read your entire post. If you are still binding mid way with the recoil spring removed, I really suspect something on the cocking lever side of the house is binding.
 

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Discussion Starter #6
TiredIron, I didn't write your # down quick enough, can you PM me.

Scott its nothing to do with cocking handle or the bolt retract pin.Gun is smooth with return spring in or out, box is square. Bolt sticks, but retract handle can easily be returned forward. Pin is not binding in slot.

BHO mechanism is not installed but block it goes in is riveted in place.

Gun is sloppy wet with oil.

No rivets protruding.

Oil type buffer, was new in wrap

The only time there is drag is when the buffer is in place
 

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...check it out...

Believe that the buffer spring retainer...(holds the buffer spring in place)...may be your problem. There is a protrusion on the retainer that must be placed into the slot of the buffer housing. Take the buffer housing,place the buffer assembly in it and slide it back and forth. Make sure the slot that keeps the retainer in position is free of burrs and does not have any restricted areas....or the buffer will hang up. I've had this problem a couple of times and now check the movement of the buffer in the housing before I install it in the receiver.
 

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Discussion Starter #8
Thanks Len, Thats def in the right direction. My buffer and buffer housing were new unused parts, I just went out and scrubbed the housing and buffer with a tooth brush and mineral spirits just to get the last remnants of cosmolene out of all the crevices. No change

What I do see is that the washer, for lack of a better term, that retains the spring is getting pretty scraped up for a part thats only been hand cycled a few hundred times
 

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Not sure if it will relate to your gun, but my M3HB needed a relief hole in the buffer tube or else I had the same issues. Many of us drilled a small hole in the rearward portion of the tube.....

Verify this before doing that tho, as you may have a different set up than mine was.....
 

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pm sent.....
 

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Discussion Starter #13
Ok finally figured it out. The clearance between the bolt and the block for the BHO mechanism was only .006". Everything was nice and smooth until the buffer was installed then the barrel extension cocks up just slightly causing the top of the bolt to rub on the BHO block riveted to top cover.

I flipped the receiver over and filed the underside of the BHO mount creating aprox .015" clearance between it and the bolt and everything is nice and smooth.

Thanks for all the help.
 

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Discussion Starter #15
more m2hb newby questions

Day 2 of live fire testing, Action cycles nicely by hand, A little force required to rotate handle downward but bolt feels very smooth afterwards, no drag.

Using factory fresh Lake City ball the gun begins to unlock and pulls next cartridge out of belt by about an inch, but not enough energy to cycle. Breech cam lock has right amount of play.

Loading and firing single rounds (no belt) the bolt opens aprox 2" but wont travel far enough to eject.

the bronze breech cam lock in my parts kit was a little deformed, but using machinist vice, rubber mallet and machinist sqaure I think I have it straight enough to work smoothly while I wait on a new one to arrive.

Buffer is oil type and has good seals , full of oil. I have not tried draining oil and leaving screws out yet to see if it operating more like an air buffer helps, Thoughts?



How hard should I have to pull charge handle to open breech?

Should I replace with steel or bronze cam lock?

is older style or newer breech lock preferred?
 

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This is too easy.

Drain the oil out of the buffer and vent it. the heavy barrel gun is not supposed to have oil in the buffer, it will cause what you are describing.

 

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Old style breech lock(steel) not an Aircraft V cut lock which has only 2/3 `s the locking surface :eek: and a steel breech cam , float your cam like a 1919`s :D.
 

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This is too easy.

Drain the oil out of the buffer and vent it. the heavy barrel gun is not supposed to have oil in the buffer, it will cause what you are describing.

brassmagnet said:
Not sure if it will relate to your gun, but my M3HB needed a relief hole in the buffer tube or else I had the same issues. Many of us drilled a small hole in the rearward portion of the tube.....

Verify this before doing that tho, as you may have a different set up than mine was.....
Alright then - I'm glad someone agreed with what I posted earlier. I know this was an issue among many of us at the time we were building our 50's. I'm just not that well versed in the troubleshooting aspects of the M2HB/M3HB guns to claim a good knowledge base. Let's hope it helps with his issues if he relieves the pressure in the buffer.
 
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