M2HB Head space & Timing 

7249xxl thank you for the support!

I’ve heard 2 as well

You’re welcome.

If it passes that gaging check it should be good. But an annual gaging check should be completed with more precise gages.

I just have my notes on it: GO: .202 inch NOGO: .206 inch FIRE: .020 inch NOFIRE: .116 inch I am 99% sure this is correct. I am out of town right now and don't have access to my gage. I can confirm this in about 3 months when I return.

"Accurate headspace can only be achieved when the recoiling parts are pulled back slightly reward (approximately 1/16 inch) to ensure there is positive contact between the breech lock recess in the bottom of the bolt and the breech lock in the barrel extension."

The timing is off, if it's the M2HB then you take the backplate off, and adjust the timing nut. I would follow the tech manual or instruction that your department designates. But if you are in a bind, in the field, or just own one personally and need it done right now; clear and rack the weapon, take off the backplate and use the firing gage throughout the process: 5. Screw the timing adjustment nut all the way down (to left). The nut should be hard to turn. 6.Reinstall the backplate. Attempt to fire the weapon; it should not fire. 7.Remove the backplate and screw the timing adjustment nut up (to right) one click at a time. Reinstall the backplate and depress the trigger. Repeat until the firing pin releases. 8.Once the firing pin releases remove the backplate and turn the timing adjustment nut two more clicks up (to the right). Do not turn the timing adjustment nut anymore. 9.Remove the FIRE gauge. 10.Replace the backplate. 11.Pull the retracting slide handle to the rear, charging the weapon. 12.Depress the bolt latch release and slowly ease the bolt forward with the retracting slide handle. Recheck the timing with the FIRE/NO FIRE Gage two more times to ensure that the adjustment is correct. If it's the new M2A1, you cannot/should not adjust it and needs to send back for higher level of repair. *this for educational purposes and I am not liable for damage or injury caused by the user* lol

I would prefer to communicate just here if that’s possible for you. Also if someone else has the same questions, it will help them as well.

@@godiamo89 greetings. Thanks for your answer. We have wedge of bolt group. Power of gases not enough to recoil gun and its stops, cartridge rests on extension of barrel in the upper side of it. Timing and headspace - ok. Is it possible that barrel and corps not enough clean? It shoud be oiled or not? Next question - buffer in old modifications with oil or w/o ?

@@IllyaLazariev-z5v That is something new i haven't come across. I will probably suggest what you have tried already. Give the gun good cleaning, no grease or carbon build up anywhere. Check the barrel chamber to make sure that is clean too. Then i would check the driving spring rod to make sure it's straight. Keep the spring out and just manipulate the bolt with the bolt stud and your finger. Everything should feel smooth. If you feel it snagging on something leave the bolt where it is and try to see what it might be catching on. Also make sure all the parts were put back in correctly, it is easy to get some parts turned around the wrong way. As for how much oil on the parts, I like to put oil on it and then wipe it off, leaving a little sheen behind. If you are in the desert where there is sand and dust, keep it dry except where there are parts rubbing. You can see those spots where the bluing has rubbed off. Hopefully that was helpful. As for the buffer, I don't know if there is any part that contains oil in it. Just make sure to wipe it clean.

Greetings, i've fixed my problem. First of all its a problem in cartridges, its not enough power of powder in it, with another cartridges everything ok. Second one - part of mechanism for automatically run rubs the bolt group in the upper side, I've regulate it. Thanks for your support We change the barrel to new one and it becomes ok, even with bad cartridges. Maybe you know, is it possible to repair/fix the barrels?

@@IllyaLazariev-z5v glad to hear the problem got fixed! I would have not guessed the cartridge was the problem unless I saw other guns having trouble too. And yes, it can be hard to tell if the barrel is bad unless you can clearly see it or it fails gauging or I test it with other receivers and it has the same problem. As for fixing the barrel, that is above the level of repair I’ve done. We usually send it back to our main supplier/manufacturer for replacement. I don’t know if you have the options, but I would imagine it take some very special equipment to get all the specs right. I would just send it back for replacement, or trash it since it’s not reliable. Best of luck to you!

I'll give a summarized explanation of headspace and timing. Headspace is the gap between the bolt face and an inner part of the barrel, for our purposes it is the gap between the end of the barrel and the bolt face. The weapon fires before the all the inner components are fully forward, which is why I pull back on the bolt when I measure the gap between the bolt face and the end of the barrel. -If the gap is too wide and the "no-go" gage goes in, that means there is a chance of the round exploding inside the receiver. The round case has a thinner part of its wall exposed and the gas could possibly rupture out the side of the case instead of pushing the round out because there is less resistance. -If the gap is to close, and the "go" does not go in, that can cause the weapon to not function as designed and could possibly damage it. The timing is when the trigger bar reaches the point where it presses down on the sear and releases the firing pin. -If the weapons fires with the "no-fire" gage inserted, that means it is firing when not in battery and the round could explode inside the gun because the weapon fired too soon. -The weapon should fire with all the components at the point of the "fire" gage inserted. This needs to happen because it helps reduce the wear on the weapon. It is supposed to fire by the point of the "fire" gage because that is where the components are slightly not fully forward inside the receiver, but it is safe for the round to fire. If the weapon were to fire with all the components after they are fully forward; Example: they hit up against the trunnion block and then fire, the weapon would beat itself apart. With it firing right before pressing up against the trunnion block, the opposite force of the round firing helps reduce the amount of force of the parts hitting against the trunnion. Mostly it is for the safety of the gun not blowing up while firing and that's usually enough to make the shooters care about doing it. I hope this helps clarify why headspace and timing is important. I don't claim to have 100% knowledge of this and I'm sure there are other reasons too, but this is my understanding from the training I received.

@@godiamo89 Thank you very much. Finally I have some clue but I have a question also. 50 bmg is a rimless botleneck cartridge. That means it seats on the neck of the cartridge and the headspace distance is between the bolt face and the the place in the chamber that stops the cartridge. Still in M2 browning, the headspace is meassured from the bolt face to the end of the barel. Like in rifles with rimmed cartridge. I don't get this, can you please explain to me this. And also with time,cause of the wear of the gun, headspace distance increase. Then why when we adjusting headspace, we back even one click more. That would increase the distance even more? Thank you.

@@martinstojanovski6830 The 'headspace' between the bolt face and the beginning of the chamber that we check is not the 'true headspace'. You are right, a true headspace is the bolt face to somewhere at the end of the chamber and before the rifling. It would be a much larger and probably a lot more expensive gauge to do 'true headspace'; where it would be inserted into the chamber and measured. What we are checking can be considered a working headspace, meaning it's good enough to work and not blow up in your face 99.9% of the time. If you cut the .50 brass shell in half, hotdog wise, you will see it is very thick at the base where the rimless part is and mostly seals everything up past the chamber back with just full brass, if that makes sense. So that gap for the headspace clearance, where you can see the brass shell when it's chambered all the way, is pretty much just filled with solid brass and not a thin wall with gun powder. As for backing off two clicks at the start. I cannot tell you why we do that, other than that is what the tech manual says. I'm not an engineer or weapons designer, so I can't give you a reason why the instruction/tech manual tells us to do that. I can say following that instruction, I've never had a M2 blow up on me. I can guess we don't want to tighten the barrel all the way down because we don't want the bolt slamming fully into the barrel every shot in full auto. My opinion is that backing it off 2 clicks leave a gap thinner than a strand of hair between the bolt t-slot and the end of the chamber, so they don't beat into each other. That is only an opinion though and not based on anything I've looked up, just that I know it fires slightly before going fully forward. Hope that helps clarify things.

I am not sure who Mr. Pavin is, it’s been a while since I went to CSWI school and have forgotten the instructors names.

This M2HB performed within the tolerances of the gauges so no timing adjustment was needed.

I know, but it would have been nice to see.

Yeah, I was planning on making another video for disassembly and reassembly for the crew serve. I can make a video covering timing correction as well.

I have a semi-auto, so I don't need to worry about timing anyway, but there aren't a lot of good M2 videos out there.

Doing well, thank you

Yeah, go for it. I'll try to answer it the best i can.

@@godiamo89 thanks from Turkey.