Getting started on my M2HB build

[SPOOK331945]

They are registered "new old stock" sideplates, made before the ban. The sideplates are 100%, they've just never had the rest of the gun installed on them. I even saw a registered Maxim sideplate come up for sale a few years ago. Lots of sideplates, trigger packs, and auto sears were built and registered in the months after FOPA 86 was passed, but before it took legal effect. S&H Arms had new FNC auto sears for sale clear up until the late 90s because they had built and registered so many. Bushmaster sold their last new transferable M-16 in 1994. Ramo, Group Industries, and every other company in that business space at the time did the same because they could see the writing on the wall. Prices increased over the years as supply dwindled and demand increased. The sideplates and such you see for sale now are all on the secondary market - someone bought it new, never built it, and just happen to be selling it. There might still be a few "new" transferable guns or receivers in the big corporate collections (Ruger, Colt, etc.), but those aren't for sale and won't be coming out unless there is a bankruptcy and even then it is not guaranteed. Reed Knight got a lot of his rare Colt experimental guns as payment when Colt was in dire financial trouble and owed him a bunch of money for design work he had done for them.

ETA: That last transferable Bushmaster M-16 - I held it in my hands and viewed the special factory documentation that was with it when it was being resold at auction around 10 years ago. It was a real trip reading that factory letter!

ahhhhh makes sense.. Thank you for clearing that up for me. Love to get my hands on one of those side plates one day

 

[Slow Hand]

My Sterling is a ‘tube gun’. Basically it was a section of pipe with a serial number stamped on it and a piece of paper saying it was a machine gun. My buddy bought three tubes several years back and had a friend built them up out of demilled parts kits.

Ive read that Norrell had an office full of secretaries typing up forms to register as many 10/22 trigger packs as he could before the deadline. He was releasing 10 or so a year. I don’t know if he finally ran out or not.

 

[SPOOK331945]

Is there such a thing as a pre-'86 transferable side plate? Not that I would ever have the budget for such a thing, but that would be amazing.

going back to your original question, I saw a RAMO side plate for a M2 this weekend down at the creek. $28000 lol. ooooo if I had the money

 

[Beowulf]

going back to your original question, I saw a RAMO side plate for a M2 this weekend down at the creek. $28000 lol. ooooo if I had the money

Yeah, I saw that too. By the time you found an M2 parts kit and did the building, I'm not sure you'd really save any money.

Then again, I haven't really seen much in the way of MG deals at Knob Creek over the last few years. Though, I did see an M11/9 for $7500, which is pretty reasonable (I almost talked my buddy into buying it... almost).

 

[AmmoManAaron]

Then again, I haven't really seen much in the way of MG deals at Knob Creek over the last few years. Though, I did see an M11/9 for $7500, which is pretty reasonable (I almost talked my buddy into buying it... almost).

I saw either a Ruger AC556 or a converted Ruger Mini-14 (I didn't look close) for $9,500. I didn't look close because I'm not in the market for one, but the price seemed very reasonable/mild bargain to me.

Regarding the M2 sideplate - if you could get it down to $25k, you would be doing ok after getting a parts kit (figure $5k to $7.5k for that).

 

[Beowulf]

I saw either a Ruger AC556 or a converted Ruger Mini-14 (I didn't look close) for $9,500. I didn't look close because I'm not in the market for one, but the price seemed very reasonable/mild bargain to me.

Regarding the M2 sideplate - if you could get it down to $25k, you would be doing ok after getting a parts kit (figure $5k to $7.5k for that).

You know, you are right, I saw that too. I think it was actually at the same table as the M11 I saw. The one MG vendor with decent pricing (not stellar deals, but pretty good pricing).

 

[SPOOK331945]

Yeah, I saw that too. By the time you found an M2 parts kit and did the building, I'm not sure you'd really save any money.

Then again, I haven't really seen much in the way of MG deals at Knob Creek over the last few years. Though, I did see an M11/9 for $7500, which is pretty reasonable (I almost talked my buddy into buying it... almost).

the window is definitely closing on the difference. Most Of the M2s I've seen have been hovering around the 40k mark. Might save a couple thousand, hard saying. You'd really have to do some shopping. I have seen a couple completes going for around 30k but they're well used to say the least.

 

[SPOOK331945]

Started early this morning doing a bit. I milled the relief on the Buffer body for the RSP clearance. What seperates the "Semi" RSP from the "Auto" RSP are what I like to call "denial islands." Now that term is probably not the true technical term but that what I call them lol. Essentially what these "islands" do is keep anyone from installing factory full auto parts into the receiver box by basically reducing the overall internal width within the receiver. Each Semi-auto RSP manufacture has their own island locations and designs. So depending on who you use for your RSP you'll need to use their print dimensions. I'm using KMP's side plate and trigger/sear assembly. Similar relief cuts will have to be made to the barrel extension and bolt. I'll have pictures of those later this week once I get them done. These relief cuts are not super critical, so if you go to do a build yourself one day don't stress it if you don't hit the numbers. Word of caution though, its better to have it a little over than under. Don't go crazy and cut 1/4" over the dimensions given! That is not what I'm saying! Use common sense and good judgement, don't remove the more material if you don't have to, but its not going to hurt you if you're .010" over nominal. But if its lower than the nominal dimensions given it may contact the islands and not allow the internal to be installed. Chances are the dimension given already provide plenty of clearance, so if its under just a touch if may not hit the island. The way I toleranced the dimensions was +.010" -.000". That was my rule of thumb in this situation and this situation ONLY.

Not the greatest picture of the inside of the RHSP but you can see the islands. kind of. You can find more examples by googling it.

DISCLAIMER HERE: I am not responsible for ANYTHING on your own build if you choose to build a Semi-Auto M2 one day. I'm just providing some knowledge and tips for anyone that wants it. If you don't like how I did something or you would have done it this way vs. mine that is completely fine. My way is not the only and best way to do it, it is just simply what works best for me. I'm a Tool Maker by trade and an engineer, so I have experience on Manual mills, lathes, surface grinders, jig grinders, honing machines, EDMs, Wire EDMs, CNC and other various shop equipment. I'm very familiar and comfortable with the operations needed to achieve the build. If you don't have experience with equipment like this I personally don't recommend building one. It can be done though, there has been many that have done the build without all this. Just remember this "size" of caliber it can get ugly real fast if things go wrong so pay attention to what you're doing and why. It's your build, have fun with it and most of all be safe and legal!

Milling on the buffer body kind of caught me off guard because of the way it machined. It machined very similar to cast iron. NOT saying that is what it is, and also I highly doubt that is what material is. Just saying it machined very similar. Anyone that has worked with cast iron will know that the chips fracture and it is very dusty. I've machined 1919 trigger frames which is somewhat of a similar part and they didn't produce chips like this did. I was using a 1/4" carbide endmill. I'm using carbide because some internals like the bolt will be hardened. They wont be super hard, but hard enough to increase service life and wear resistance. It doesn't list the radius in the bottom of the relief so I'm starting with 1/8" radius for now. A 1/4" endmill will give a 1/8" radius naturally in the corners, that is why I chose that size cutter. Might have to reduce it later though we'll see.

 

[SPOOK331945]

Almost got the internals done this morning, still need to cut the slot or the new semi sear. I have to order a cutter first. Should be the last thing other than modifying the trigger bar bracket for the new trigger and disconnect.

Bolt

Barrel extension

 

[praff]

I have been wanting to do one of these for a while and NOW I really want to do one!!!

Trade you a $300 surface grinder for it!!!!

 

[SPOOK331945]

I have been wanting to do one of these for a while and NOW I really want to do one!!!

Trade you a $300 surface grinder for it!!!!

Don't tempt me lol oh what I could do with one of my own....

 

[SPOOK331945]

here is everything together. Seems to all line up nicely. For now.. We'll see after riveting hahaha

Buffer body relief is a little hard to see due to some insta blue I put on it. Probably re park all of it later but for now that'll do.

 

[SPOOK331945]

Quick update on build progress. Working with the pawl brackets this morning. When I first purchased my kit it came with a set of pawl brackets, unfortunately it came with two right hand side brackets... These where newly manufactured brackets. Something I realized quickly was that the link stripper (both versions) did not line up with the pin. Little further research and in search of a new matching left and right set I notice that there is a relief cut in the top of the bracket to allow the stripper to seat lower and align with the hole. This is something that I haven't seen anyone discuss of any other build tutorials. I'm guessing because most builders are using a surplus receiver kit that has already had it done. With older surplus kits drying up you're starting to see more virgin parts, like mine for example. Almost all the receiver plates are new except for the top plate. So little features like these aren't added yet because the parts are not standardized like they used to be. There's so many manufactures out there that the receiver parts don't necessarily interchange, forcing them to leave certain features out until the assembly process.

I was able to located a new matching set through BMG parts. Beautiful set, but the slot was still missing. Not a big problem just wasn't expected I guess you could say. Now both Left and Right side plates are new, so the rivet holes are not drilled yet for the brackets. Locating these holes will probably be the last ones I drill for the fact that I will be using the trunnion and link stripper to locate the pawl bracket. The trunnion also has the relief cut into it, but the new side plates don't. Once I have the main rivet holes located and drilled I'll bolt it all together and use the trunnion to located the relief cut on the side plates. Following this the pawl bracket/link stripper assembly can be located in the slot and the holes for the pawl brackets can be located and drilled on the side plates.

I used a 3/16" cutter. Depth isn't something to worry about so much but the width, its probably best to keep it pretty snug. Leaving just enough room for the parkerizing. The stripper itself is going to have a reasonable amount of force being applied to it, as the round is being pulled from the link. So the side to side slop you would get from a slot that is cut too wide wouldn't do it any favors in the long run, possibly causing feeding issues too (completely my personal opinion on this part I'm being picky). There's quite a bit of surface contact on the slot cut in the trunnion too to add to the side to side rigidity. It most likely wont be a complete killer if its a touch sloppy. Some others may even just use a hand file, but once again I'm being picky lol. Below you can set the slot I cut for both left and right brackets.

new style stripper, combined with the rear cartridge stop

old style with a separate stripper and rear cartridge stop.

raised lip that calls for the relief slot.

 

[1911ly]

What an awesome project. There is just something to cool about shooting a belt fed. Looking forward to seeing it come to life.

I haven't shot my 1919 in a few years. I need to get it out. Yours sure beats it by a mile! What an awesome gun you have!

 

[JeepHammer]

I wonder if the semi versions are as tempremental about headspace/timing as the military full auto versions...???

A good 50 Gunner that could keep it running was worth his weight in gold, platoon Sergeants used to fight over the best gunners in combat outfits.
M2 wasn't my thing, I couldn't seem to get more than about half a belt out before I became a 'Single Shot Sucker'.
8 to 10 shot bursts, the same trigger time it takes to say "Die! Mother F****r! Die!" (with feeling ) just in case you never knew a Marine...

Other than having one out of time and masturbating the gun for single shots I've never fired a semi-auto version.
Not exactly semi-auto when you spend more time jacking the charging handle than shooting...

Long before .50 BMG rifles came along, the Marines used M2s for 'Sniping', there are still a few of the optics mounts around that mount on the receiver for 1" tubes, I saw one at Knob Creek last month, I think it was the Viet Nam version.
The Korean war version didn't have the Leatherwood ART range compensator, but I don't know how long after Viet Nam they used the ART type elevation adjustment for them, we still had some in service in the 90s, but the receiver clamps were different.

The slow cyclic rate let you click off single shots very easily, some of the aircraft .50 BMG machine guns had a MUCH higher cyclic rate of fire than the infantry version did.

 

[SPOOK331945]

What an awesome project. There is just something to cool about shooting a belt fed. Looking forward to seeing it come to life.

I haven't shot my 1919 in a few years. I need to get it out. Yours sure beats it by a mile! What an awesome gun you have!

Belt fed guns definitly give you a bug, I'm on #4 now haha. It is exciting the closer I get. I have to keep telling myself to slow down and be patient

 

[1911ly]

I wonder if the semi versions are as tempremental about headspace/timing as the military full auto versions...???

A good 50 Gunner that could keep it running was worth his weight in gold, platoon Sergeants used to fight over the best gunners in combat outfits.
M2 wasn't my thing, I couldn't seem to get more than about half a belt out before I became a 'Single Shot Sucker'.
8 to 10 shot bursts, the same trigger time it takes to say "Die! Mother F****r! Die!" (with feeling ) just in case you never knew a Marine...

Other than having one out of time and masturbating the gun for single shots I've never fired a semi-auto version.
Not exactly semi-auto when you spend more time jacking the charging handle than shooting...

Long before .50 BMG rifles came along, the Marines used M2s for 'Sniping', there are still a few of the optics mounts around that mount on the receiver for 1" tubes, I saw one at Knob Creek last month, I think it was the Viet Nam version.
The Korean war version didn't have the Leatherwood ART range compensator, but I don't know how long after Viet Nam they used the ART type elevation adjustment for them, we still had some in service in the 90s, but the receiver clamps were different.

The slow cyclic rate let you click off single shots very easily, some of the aircraft .50 BMG machine guns had a MUCH higher cyclic rate of fire than the infantry version did.

If it is anything like a 1919 build they are able to tighten up the head spacing a lot solve a lot of issues. The cyclic rate is so low/slow on the semi. Jeephammer can comment on this. It should be fun to soon.

I have a second carrier assembly I need to re-machine so I can more easily swap between 762 and 30-06. I have 2 762 and 1 30-06 barrels. I'd like to pick up a 8mm Mauser and a 762-54 barrel and a few more carrier assembles. It is really easy to change calibers. 10 minutes or so at most. Swap the barrel assembly and remove the bullet guide. Hopefully this summer. Head spacing on it is so simple and a lot tighter then the full auto. Semi is like 2-3 clicks off tight on the barrel locking tab. Full auto is 10-15.

Jeephammer, 4, too freaken awesome!! Following along for sure!

 

[SPOOK331945]

I wonder if the semi versions are as tempremental about headspace/timing as the military full auto versions...???

A good 50 Gunner that could keep it running was worth his weight in gold, platoon Sergeants used to fight over the best gunners in combat outfits.
M2 wasn't my thing, I couldn't seem to get more than about half a belt out before I became a 'Single Shot Sucker'.
8 to 10 shot bursts, the same trigger time it takes to say "Die! Mother F****r! Die!" (with feeling ) just in case you never knew a Marine...

Other than having one out of time and masturbating the gun for single shots I've never fired a semi-auto version.
Not exactly semi-auto when you spend more time jacking the charging handle than shooting...

Long before .50 BMG rifles came along, the Marines used M2s for 'Sniping', there are still a few of the optics mounts around that mount on the receiver for 1" tubes, I saw one at Knob Creek last month, I think it was the Viet Nam version.
The Korean war version didn't have the Leatherwood ART range compensator, but I don't know how long after Viet Nam they used the ART type elevation adjustment for them, we still had some in service in the 90s, but the receiver clamps were different.

The slow cyclic rate let you click off single shots very easily, some of the aircraft .50 BMG machine guns had a MUCH higher cyclic rate of fire than the infantry version did.

Head spacing is same, but timing isn't involved at all on the semis. Timing is to keep the round from cooking off before the bolt has a chance to be fully seated.

Mechanically I can picture it in my mind and what its doing far better than I can put it into words. Sounds like you're pretty familiar with the ol girl. Here is the best I can describe it for the ones who are not.

At the far left is the trigger, timing adjustment screw and trigger bar, at the far right you can just barely see the bottom of the trigger bar and the top of the sear.

When you "adjust" for timing in the M2, you turn a screw that is located on the top plate in the rear inside of the receiver. As you adjust the screw up and down you are changing the stopping point of the trigger bar.

When you press down on the butterfly trigger it is lifting the trigger bar up to meet the timing screw. Now base on where you have it screwed out to, it will contact it sooner or later. Moving on down past the pivot point on the trigger bar you get to end where it actually contacts the sear itself. Because the timing screw directly changes the stopping point on the trigger bar it will change where the end of the trigger bar stops above the sear also.

On the bottom of the trigger bar there's a slight angle lead in, where the sear contacts. As the bolt is traveling forward the sear will drag along this "angle" being forced down to release the firing pin. Changing the stopping point higher or lower, you are geometrically changing where the sear actually starts to "ride" the ramp. In geometric terms the hypotenuse leg of the triangle. If it contacts lower on the ramp it will begin its travel upward sooner than if it was to contact higher on the ramp or hypotenuse leg. Depending on if its contact point is higher or lower on the ramp it will release the firing pin sooner or later, changing when the round is fired in relation to how far forward the bolt has traveled to meet the barrel.

With semis having a disconnect this eliminates the need for timing because the bolt will fully seat, engaging the disconnect. The trigger then has to be released before the disconnect will disengage. This is why bump stock aren't worth a d#$% in my opinion. It over speeds this whole process causing malfunctions. All closed bolt full auto guns have some form of timing going on, some are adjustable some aren't. Well.. easily adjusted. Everything is adjustable if you really know what you're doing.

The 1919s operate on the same principal, just put the trigger on the bottom of the receiver and push the sear upwards to release the firing pin. Just opposite movement.

excuse my poor drawing, tried to de-clutter the process as much as possible. Its a little bit of Four bar linkage theory going on here. My triangle is inverted but the concept is the same.

Four bar linkage is what Mr. Browning could do in his head so well. This isn't the exact diagram just an example of what I'm talking about.

Main objective to all this is making sure that the bolt has time to fully seat and the breech lock is in place before the round is fired. Circled in red is the breech lock, youll see the notch in the bottom of the bolt it will sit in once everything is moved into place.

 

[SPOOK331945]

Just finished the bolt up this morning. It is now officially neutered...

The slot for the sear had to be enlarged for the new semi auto sear. Enlarging the slot of course makes it impossible to drop in the original full auto sear. The .500" width that is listed I think is an old revision. the sear has another raised section but it matches the original slot width on this portion so no cutting is needed here. Only the .755" and .625" width are of concern. Got a cutter for this that measures .750" wide and .125" thick. Originally I was going to make an electrode and sink this on the EDM but I was being lazy and didn't want to go through all that trouble. Plus the bolt wasn't as hard as I expected it to be. A hand file would touch it so I was able to order a HSS cutter vs. carbide. If I had to do carbide I was definitely doing the EDM, just for cost alone. Wasn't going spend 200-300 for a single cut.

I kept it pretty tight dimensionally here. So take your time indicate it in square. Its a snug fit but moves freely, going to taking some lapping compound just to clean it up a bit. Kept it tight so that over time the sear would wear in and not wear out. I would have rather had a cutter a little more under the .755", just to take out the flex factor of the tool when cutting. I choked it up in the quill as high as I could to reduce the flex as much as possible. In hopes of reducing the chances of over cutting the slot. Luckily it worked out just fine.

This pretty much completes everything internally that needs modifications to make it semi auto. Going to start moving forward on the receiver and start getting it ready for riveting.

Kurt sidewinder attachment is worth its weight in gold.

 

[JeepHammer]

Not really up on the M2, I was a field creeper.
In 16 years I cleaned more than I can count, fired a bunch during qualifications, but it wasn't my job.
Snipers got the optics mounts and distributed them generously among gunners, which is why the old Viet Nam era 50 mounts are scarce.

The new guys have all kinds of red dots and holographic sights, it's a different mount.

You will learn a lesson about optics when you install one on a .50 BMG of any kind...
Watch a slow motion firing cycle with optics some time and you will see why!
When the tube deflects 1/2 or 3/4 inch and comes back to zero, you understand why a Bushnell isn't going to live long...
It REALLY takes a beating, and Leupold, Unertl, and a couple others are the only ones that live more than a few rounds.
The $100 bubble pack optic isn't going to cut it.

I always moved the rings out as far as I could get them, towards the objective & ocular bells, just adding a little support to something that was never intended to be a pry bar!

Don't get me wrong! ALL of the .50 gunners were excellent! (If you weren't, you did something else you were good at).
Some were just absloute surgeons, when someone is slinging 700 grains of lead at 3,000 fps, 10 meters from your position, you REALLY don't want me behind the gun!
I leave that up to the actual gunners, and they CAN do it!

Are you aware that Carlos Hathcock II had the sniping record for 35 years with a M2?
In Viet Nam, they used a long Unertl target scope, mounted it on an M2, and Carlos Hathcock hit a man at 2,500 yards on the second shot.
The first shot took the handle bars off a bicycle he was pushing, so missed by about 8" at 2,500 yards on the first shot.
This WASN'T a 'Super Duper' or 'Tricked Out' M2, it was one off the line...
And it was common field issue ammo...
Think about that!

In Korea, Marines harrased an island off the Korean coast, a mile away, and scored kills firing single shots.
The North Koreans & Chinese nearly pushed the Marines into the ocean...
They killed wounded, tortured, and excited POWs.
The Marines wanted some payback once they stalled the advance, and started picking off enemy soldiers at over a mile away with a line issue M2 and a WWII made target scope!

If you were North Korean, you just HAD to be scared to death to patrol or pull guard duty, even a trip to the crapper was a life & death decision!

Carlos Hathcock heard about this (never giving the Korean Marine's name, .50 BMG was a 'war crime' to use against men, it was anti-material) and had optics mounts manufactured to fit the receiver of M2s.

If you think it's only good for busting up hardware, THINK AGAIN!
Rock steady tripod mount, screw thread adjustable windage & elevation adjustments, over a mile range, up to 765 grain bullet @ up to 3,300 FPS...
And that's just the surplus military ammo on the market...

I've seen guys put 10 round burst in car door size targets at 1,000 meters on full auto,
Punch the 'V' in 2,000 meter targets shooting singles.
This is the DEFINITION of long range & hard hitting!
I don't care who your god is, if you want to meet him, shoot at a good .50 gunner!

And, just for the record,
Carlos Hathcock's record was broken by a .338 Lapua, special, purpose built rifle with the latest, greatest 20x optics money can buy,
It was 2,700 yards, and the sniping team threw 25+ rounds before they got a kill.

If you have ever looked through an early 1960's optic, you know what I'm talking about, it's like looking through the bottom of a dirty soda bottle...
Carlos did it with an 8x optic, off the line M2 and standard issue ammo... In 2 rounds... Cold bore shots...

I don't believe every Carlos Hathcock 'Super Sniper' story, but that one was witnessed & documented.
No room for question.
No question what an M2 will do either!