M2HB Problems HELP PLEASE

[Lowpull]

I need some help with my M2HB. I have a new M2HB and the rifle has been sticking cases and been blowing the heads off the cases. I have set the timing and spacing with the GO, NO GO gauge. I could use some suggestions.

I have tried couple different brands of ammo
Seems to happen more when the gun heats up.
This is new ammo.

Any suggestions?

 

[maccrazy2]

Re: M2HB Problems HELP PLEASE

I have a semi 1919a4. I was told to set the headspace with the bolt just barely touching the barrel/trunion by the guy who helped me build it. I do not remember the exact reasoning but I recall him telling me I would have case separations if I used the headspace gauge for a full auto.
To clarify, are you using the flat headspace gauge?
Here is mine. I have a shroud that is a scale version of the M2 so I can make it a mini version of yours. I need to get another barrel to turn down before I install it.
I had planned to build a M2 but the parts kits got so expensive I never got around to it.

 

[Lowpull]

Re: M2HB Problems HELP PLEASE

I have tried several things

1-military manual says screw in the barrel 100 percent. Unscrew 3 clicks check with go/no go. Unscrew a MAX of 15 clicks. I have found that the gauge is GO at about 7 clicks.
2- I have tried a range from +3 Clicks to + 12 Clicks and NO setting works. All end is separated cases.
3- it seems in all settings that there is a LITTLE pressure put on the bolt(holding it open ever so slight) buy the round sitting in the tray under the pawl. NOT much but a little. Not sure that this is correct.

Thanks for the help

 

[fdkay]

Re: M2HB Problems HELP PLEASE

Have you tried a different barrel?
Could be a bad chamber or barrel.
Is the chrome chipped or damaged in the chamber or the chamber rusty?

Timing is not set with the go/no go gage.
Only headspace is set with the go/no go.
Timing is checked with the Fire/No Fire gage, timing is adjusted via the nut by the trigger bar.
If the gun will fire with thr no fire gage, the timing is early and you could have a case rupture with the action not fully closed.

 

[Lowpull]

Re: M2HB Problems HELP PLEASE

I have not tired a new barrel as of yet. Was hoping to not have to add that cost. BUT seems like i might have to. The chamber is clean and new. I even polished it what a chamber polish just incase.

I do understand the timing VS headgap spacing. I dont think it is timing purely because i have had it happen on the first round. Thank you for pointing it out.

I have been wondering if the chamber is incorrect my self. Too loose and there for cases fail.

Thank you for the input

 

[HANDYMAN]

Re: M2HB Problems HELP PLEASE

What manufacture of ammo are you using? There's been some reloaded stuff going around that I saw doing that at the last machine gun shoot I attended.

 

[TGagnon]

Re: M2HB Problems HELP PLEASE

How much did you polish the chamber? That could be your problem right there. Other than that I would say it sounds like it needs broke down 100% and gone over with a fine tooth comb. I like the M2 but hate that new M2A1 as the guys keep breaking off the lock pin that holds the barrel in position.

 

[Eagle1899]

Re: M2HB Problems HELP PLEASE

When you screw the barrel in and adjust headspace are you pulling the bolt back to the correct position? The barrel retaining tab must be centered in the witness hole. The go side of the gauge should fit snug and the no-go side should not fit at all.

http://www.pica.army.mil/picatinnypublic/m2_headspacetimin/m2-poster.pdf


How did you polish a stellite chamber?

 

[M C]

Re: M2HB Problems HELP PLEASE

Completely a headspace/timing issue. ^^^Fdkay is spot on.

 

[Lowpull]

Re: M2HB Problems HELP PLEASE

Hi Gang thanks for the replies.
-I have tried 3 different rounds. Israel loaded that was little long and would not fit in the tray, American Eagle, and TMI reloads. The problems all started with the American Eagle stuff.
-I polished the chamber VERY little used flex hone and mineral oil. I think like 7 -10 passes (did it last year do remember exactly)
-I just got the sheet that was linked for head gap spacing going to check it again. I was using the mil manual and it is NOT quite as clear as that sheet so going to give it another go.
-Dont think it is a timing issue since it is a semi auto m2hb. (i dont think i mentioned that sorry.)
-the lock pin is still functional but i am starting to get what i would describe as considerable wear on the locking grooves. This is due to the IN and OUT done buy constantly trying different head space.

Thanks for all the help gang. Going to try to get it out to the range again in the next couple days i will post more info. You all have given me some food for thought. Stay tuned.

 

[taseal]

Re: M2HB Problems HELP PLEASE

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowpull</div><div class="ubbcode-body">Hi Gang thanks for the replies.
-I have tried 3 different rounds. Israel loaded that was little long and would not fit in the tray, American Eagle, and TMI reloads. The problems all started with the American Eagle stuff.
-I polished the chamber VERY little used flex hone and mineral oil. I think like 7 -10 passes (did it last year do remember exactly)
-I just got the sheet that was linked for head gap spacing going to check it again. I was using the mil manual and it is NOT quite as clear as that sheet so going to give it another go.
-Dont think it is a timing issue since it is a semi auto m2hb. (i dont think i mentioned that sorry.)
-the lock pin is still functional but i am starting to get what i would describe as considerable wear on the locking grooves. This is due to the IN and OUT done buy constantly trying different head space.

Thanks for all the help gang. Going to try to get it out to the range again in the next couple days i will post more info. You all have given me some food for thought. Stay tuned.
</div></div>

but are you pulling the bolt slightly back?

there is a little hole on the right side (if you have behind the gun) towards the front. you have to pull the bolt back very little (like 5% of the whole way) until a little tab is exposed from the hole (we call it the tit or nipple in the army lol) now you do your adjustment.

 

[Lowpull]

Re: M2HB Problems HELP PLEASE

taseal you are spot on! Before your post i went out and found that spring and the hole. And i was able to turn the barrel in another 90 DEG. It made the world of difference. 100 rounds NO ISSUES!

Thanks every one! Got it fixed.

 

[TGagnon]

Re: M2HB Problems HELP PLEASE

Glad you got it fixed but I have to say I am amazed you bought a belt fed 50bmg without seeming to have any considerable experience with one? They are extremely complex piece of machinery to get into with a lot of power being handled to not know 100% what you are doing from the get go. Not realizing you didn't have the barrel screwed in was a big "Oh Fuck" moment, or at least it would be for most of the people I know.

 

[taseal]

taseal you are spot on! Before your post i went out and found that spring and the hole. And i was able to turn the barrel in another 90 DEG. It made the world of difference. 100 rounds NO ISSUES!

Thanks every one! Got it fixed.

You welcome buddy! I know my ma deuce. The most complex infantry weapon I have used. Most fun to shoot as well

Sent from my Xoom using Tapatalk 2

 

[taseal]

Glad you got it fixed but I have to say I am amazed you bought a belt fed 50bmg without seeming to have any considerable experience with one? They are extremely complex piece of machinery to get into with a lot of power being handled to not know 100% what you are doing from the get go. Not realizing you didn't have the barrel screwed in was a big "Oh Fuck" moment, or at least it would be for most of the people I know.

Yup... The barrel could have flown off. Iol

Sent from my Xoom using Tapatalk 2

 

[McCrazy]

Holy crap, I can't believe you own this weapon and didn't research how to safely operate it. Any time you are screwing the barrel in or out you need to put the nipple in the window.

I am glad no body was hurt but you can't leave that to chance. .50 cal is not a round to play with carelessly. I have seen video of M2HB barrels getting shot off because they were not installed properly and luckily the damn things are so heavy they don't fly far.

Learn from this: M2 Failure (headspace and timing) - YouTube
Learn this: TBS M2 .50 Cal Headspace/Timing Tutorial - YouTube
Set timing: http://www.armyproperty.com/Resources/PS-Mag/2008-05/666-24-25.pdf
Your hand versus a .50 round (click the RED "HERE" link for un-edited photo): Soldier Mutilates Hand By Hitting .50 Caliber Round

 

[samnev]

Glad you got the head space procedure straightened out. I have seen a few guys get really hurt when a blown case sent debris down thru the bottom of the receiver. That is why I never put my legs under the Ma Duce when I was shooting it.