Thursday, June 30, 2011

The .50 BMG bipod

Been moving along real slow on finishing the .50, this constant 100+ degrees every day is really wearing me out. I have gotten a few parts rough machined for the bipod, but still need to do some final machine work and sanding to them before adding the springs that will hold the legs in the down position or in the folded-up position.

I wanted to make the bipod and the scope mounts at least look like I cared, but they're shaping up to be just quick and simple so I can Duracoat this thing and move on.
To start, I took some .75" square cold roll steel to make the legs out of. Nothing real special, but sturdy and capable of holding up a recoiling .50 BMG rifle. I drilled 3/8" holes at each end, one end to mount to tabs I would weld on the receiver, and the other end to mount to "feet" that would spread the weight of the rifle out a little. I wanted the whole assembly to be able to pivot freely, so the legs and the "feet" are hinged. I plan to drill sequential holes down the centerline of the bipod legs to improve the aesthetic value and lighten them up a little. I'll get to photos of the legs in a bit.

For the tabs that mount to the receiver, I had some 1/4" thick, 2"x2" angle steel that I cut at a 30 degree angle then cut an arc in the opposite side, so it would support the bipod legs in two planes.

The legs were bolted up to the tabs, then I needed to find a way to do some angle matching. The legs were at 65 degree angles to the ground, and I didn't want to just cut the legs to match the angle, because it really would not have given the legs much footprint to spread the weight of the rifle around. I had some 1.25" square stock laying around, so I cut 2.5" long sections of it off. I took the two cut off sections and set them up in my mill vise at 25 degree angles, then milled the bottom flat. Once that was done, I flipped the stock in the vise and slotted them with a .75" end mill to a depth of 5/8", then drilled them out for the legs to bolt in place.
The resulting legs and feet are pretty stout, and fold up and extend nicely. I still need to do my sequential drilling in the legs, round off all the sharp edges, add retaining springs, and add in some leg stops of some sort to limit leg travel both fore and aft.

That's all for now, I should have these finished up in a week or so. I have already started working on the scope mounts as well, but unfortunately my first attempt did not pan out, so I have started on a new mount. I will probably just weld a simple base on the receiver and bolt a weaver rail to the base so I can call it done. The Duracoat will be ordered this coming week if all goes according to plan, I have decided on a gloss black base with a red DuraPearl and clear. I hope this turns out in real life as good as it has in my head, but only time will tell. This weekend I am sandblasting everything in preparation, then once the scope mount and bipod are finally finished I will do my final welding, fill in any pits or gaps, then do the final sanding before adding color.

Sunday, June 26, 2011

Bill Holmes .50 caliber rifle, reviewing the finished build

I'm still here. I've been working on my .50 trying to get it cleaned up and ready for Duracoat, as well as machine the bipod legs and scope mounts. It has been so hot here for the last few weeks that I have not been able to stomach the extreme temperatures in my garage during the day, so much of my work is done late at night after the family goes to bed.

The main point of this post was to put some information out there for the many people who have been searching for information on the Bill Holmes .50 caliber rifle. I seem to be one of the first hits that google pulls up when anything related to Bill Holmes is searched for. So, for all of you out there in internet land who find this post while searching for the plans or the video, there are some tips and other information I thought I would throw out there. One big thing that you should do is get both the video and the book. There are things mentioned in one that is not covered in the other and vice versa.

I will say that my rifle does not entirely look like the original one in the Holmes plans. There is a reason for that. The original design is UGLY to me. The good thing is, the receiver and bolt design are the important things, so as I found out, pretty much everything else can be easily changed about the design.
For those of you wondering, the receiver itself can be easily built without a lathe or milling machine, though both tools make it much easier. Since the rest of the parts are just simple parts, and are not an actual registered firearm, a local machine shop could machine the rest of the parts needed.

As far as the receiver, Holmes calls for the bolt slot to be cut all the way to the rear of the receiver, as the bolt handle is welded to the bolt, and the striker limiter is not removable in his plans. This slot would make the receiver spring apart some, as all tubing does when cut, which makes it look like crap and really doesn't help the rifle function smoothly. However, there are several ways you can get past this poor design.

If you use a striker system like the original plans calls for, you will notice that there is a part to be machined that threads on the rear of the striker. This part is supposed to keep the firing pin/striker centered in the receiver and also has a angled part that fits into the bolt, which I refer to as the striker limiter. This angled piece keeps the striker from traveling all the way forward and striking the primer unless the bolt has been rotated and locked in place. This part is poorly designed, as the whole thing is one piece, and would keep the bolt from being removed without the long slot down the receiver. You have an option on this striker assembly in order to keep from having to slot the receiver length:

Machine the striker limiter in two pieces, and use a small allen head bolt to hold the angled piece in place. I did this the first time around as can be seen in my post here. This did function, but it really wasn't reliable enough to use. I liked how hard the striker would hit dummy rounds, but the striker would sometimes slip on the sear by bumping the rifle hard enough. You can remedy this by machining a different striker limiter than called for in the plans. The one in the plans is designed to fit inside the rear of the bolt, but that does nothing for keeping it perfectly centered in the receiver tube, which was the problem with mine. Instead, cut a piece of 2" solid round stock, .25" thick, and bolt your angled striker limiter to this. Cut threads in the center of it so you can thread your striker into it to limit your firing pin protrusion. This will allow the striker to stay centered and not slip past the sear. Of course, I figured out how to make the system work after I had already switched to an AR15 hammer system.

I know what you are thinking. Why did I drop the striker system?
Simple. I did not like my original trigger guard system. It was very boxy and did not appeal to the eye. I machined one out of a block of steel that looked a little better, but I still wasn't happy with the way it looked and worked. I had a block of aluminum laying around that I figured would look better and weigh less, and I got really tired of trying to improve on a crappy striker design, so I just machined a fire control mount for an AR hammer system. It works, it's reliable, and it got the job done.
Were I building another single shot .50 with this receiver design, I would use the AR hammer system again. It's nice to build something entirely by yourself, down to every last little part, but I have been building this rifle over a period of several months, and I wanted the damn thing done. You can spend hour after hour after hour on building the fire control group yourself, or you can machine a simple mount to toss an AR group in, mount it to the receiver, and you are done.

Now, if you use an AR hammer group, and you mount it as far rearward as I did, you must do some modifications for it to work 100%.

First, plan on buying a Wolff hammer spring. Normal AR hammer springs will not light off a primer on the first tap. 50 BMG primers are hard, and the surplus round primers are even harder.

Second, you either must machine an extended firing pin, or you need to machine an extension that will hold a factory AR firing pin. I machined a piece of M2 drill rod that the factory AR pin presses in to, and it is set up so that the extension will not fall out of the rear of the bolt.

Third, you need to make a safety device that prevents the hammer from being able to tap the firing pin unless the bolt is rotated and locked in place. This is a must. Dropping the hammer on a live round with the bolt not locked in place will lead to a very bad and very loud experience. I cut a piece of tubing into a C shape, and ground it until it was a sloped surface and welded it to the rear of the bolt. When the bolt is rotated and unlocked, the tubing section slips under the hammer and slowly pushes the hammer back as the bolt is rotated. When the bolt is rotated down and locked in place, the sloped piece of tubing is not in the way of the hammer tapping the firing pin extension.

Fourth, you will need to slot the bottom of the bolt. The AR hammer will not cam back far enough for the bolt to cycle all the way to the rear, it will actually stop the bolt after an inch or two of travel. I cut a 1/2" deep slot about 2/3 down the bolt to allow for full travel so the rifle can be reloaded. With this, you will have do a little sanding on the AR hammer to make sure it has no hard edges to catch the bolt.

The AR fire control group must be positioned carefully so that the hammer will strike the firing pin extension squarely and not on the tip or off center. This can be a real PITA, but it is possible to do.

Another thing I should mention is the barrel extension and the barrel. This is one of the problems associated with the .50 BMG builders book versus the video. The book calls for using a surplus M2 barrel and turning it down to a given profile. I did not use an M2 barrel, I used an M3 aircraft barrel, which did work, but were I to do this rifle again, I would not use either of these barrels. It is very convenient to have a barrel that is already chambered, but other than that, there is a lot of machine work that has to be done to these barrels in order to get them to the final profile. If you buy or download the video, you will find in the video that Holmes calls for the surplus barrel to have most of the chambered area cut off and the barrel rechambered. At one time, these surplus barrels may have been inexpensive and common, but that is no longer the case. If you buy an M2 or M3 barrel with the intention of building Holmes' rifle, DON'T DO IT. Sell the surplus barrel and buy a simple barrel blank and have it chambered. You will save a lot of money, time, and trouble, not to mention that will ensure there is another machine gun barrel on the market for those of us with transferable machine guns. (No, I do not own a transferable M2, but I do own a transferable NFA item and I will leave it at that.) Another reason to use a barrel blank is that the M2/M3 barrels only have about 1" of thread on the chamber end. Now, this short thread length does seem to work just fine in the M2 machine gun, but I really would have felt better about the rifle if I had another 1/2 inch of thread there. The M3 barrel can not be machined to the dimensions Holmes lists in his book, either. The M3 barrel is much slimmer in diameter overall and though mine works, save yourself some time and money and just buy a barrel blank off of Gunbroker.

The Holmes buttstock assembly is also kinda goofy looking to me. I know he designed this rifle to be functional rather than aesthetically pleasing, but something I figured out halfway through this build was that if you are going to build it, build it to a level where you will be satisfied a year down the road. Half the changes I made to the rifle were due to aesthetics. I finally decided on the design that I have now after banging my head on the wall a few times because it was very difficult to make the rifle look one-of-a-kind and not have it look like a Serbu or a Barret or any other production rifle. Most of my problems with the Holmes rifle were due to aesthetics more than function. His original rifles went bang and supposedly there are a few of them still floating around out there. However, if you like the way the original rifle looks, feel free to build one identical to it, being a free country and all.

Another issue I had with the Holmes design was the drawings for the extractor. The drawing was horrible and even when I machined an extractor that was as close to the drawing as possible, it still did not work too well. I wound up just making a new bolt head that was slotted in the same manner as a shell holder for a reloading press. This has worked very well so far and is much simpler. This is a single shot rifle, after all, and given that I can't afford to feed it on a daily basis, it's probably best that I prevented myself from reloading the rifle very easily. The video outlines a different extractor than the book, and it looks much more usable than the one in the book

So, if you are looking to undertake one of these builds, my opinion is that it is worth it if you already have the tools and materials. There are indeed quite a few things to look out for in regards to the book instructions. Holmes makes it clear in the preface to the book that he is nearly blind and is also suffering from Parkinsons at that point in his life, and if I were to guess, he drew up the plans long after he had built his last .50 BMG rifle. There are just too many differences between the video and the book.
Buy the book and the video, go through both with a fine tooth comb, and grind some HSS lathe tool bits and get ready for a fun build and a lot of learning experiences. Never be afraid to build a part twice just to make sure you get it built right at least once. If you don't have anyone nearby that can harden all the bolt and barrel extension parts, then seriously consider making the parts out of 4140 prehard or 4140 HT (same thing), it is 4140 stock that has already been hardened to between 28 and 35 Rockwell. If you can find it, use 4140 QT, which is the 4140 prehard that has been quenched and tempered, and usually is between 35 and 38 Rockwell hardness, according to what I have heard. Do not take shortcuts here,  send all high stress parts out for hardening by mail if you have to if the proper material is not available. So far, my parts constructed of 4140 prehard show no wear or stress, but I will still be sending them out for final hardening and tempering to 40 rockwell hardness before final assembly. I have seen other rifles built on homebuilt firearm forums that were built entirely out of 4140 prehard and never hardened any further, but in reality it is only another hundred bucks or so to make sure your parts stay in one piece. Just my opinion.

With that, if any readers have a question or suggestion, please feel free to leave a comment.

Tuesday, June 14, 2011

Bill Holmes .50 BMG rifle update

Well, I disassembled the whole rifle to check for any damage/s. I had to clean it a lot more than I thought I would, that surplus ammo shoots DIRTY. No big deal, some rubbing and some CLP cleaned everything right up. In my visual inspection, I was looking for any cracks, abnormal rubbing, fractures, pits, and anything else that might cause a catastrophic failure later on.

So far, I have found exactly no damage, no fractures, no evidence of wear at all aside from being really dirty. Now, I did find a few issues I will have to address before finishing everything in Duracoat.

1. The bolt face needs polishing. There are still some tool marks on it from the milling and turning. These are mainly cosmetic, but there is one small area of metal where the cartridge sits on the bolt face that is about 0.001" higher than the surrounding metal, so when the cartridge goes off, it stamps an impression in the head of the case this small amount and makes it slightly difficult to remove. A small needle file and some emery cloth will remove this and polish it up smooth.

2. I will have to put in a firing pin return spring of some sort. I had trouble removing fired cases because of the previously mentioned tooling mark on the bolt face, but also because the firing pin sticks forward and won't easily retract, probably due to the gunk the surplus ammo leaves behind.

3. The firing pin now sticks out too far. In my efforts to get it to protrude enough to activate those hard surplus primers, I drilled the bolt head too deep for the pin. Now, the firing pin actually punctures the primers. This lets a bunch of hot burning gunk into the bolt head, which is part of why the firing pin sticks. Thankfully, since I drilled the bolt head too far, all I have to do is put in a small section of a spring coil to get the pin to retract. This should fit in nicely where the bolt head was counter-bored for the AR15 firing pin. No fuss, no muss.

4. The small allen head bolts that hold the bolt head to the bolt body did back out and made the bolt a little wobbly. Some locktite will easily fix this once the bolt is ready for final assembly after Duracoat. Given the epic shock I subjected them to today, I'm not surprised.

5. The barrel extension backed off of the barrel a smidgen. I forgot to torque it down before installing it the last time I had the barrel assembly out. This is not too big a deal, but it could have been a big problem had it gotten much worse, as that is what controls how the cartridge headspaces. I will likely integrate a small setscrew into the assembly and silver solder the barrel to the barrel extension after torquing it all down in a vise. All I need is a small "check" assembly that will prevent the barrel extension from easily rotating. This issue could have been prevented by me not having a case of temporary rectal-cranial-inversion, but I'm glad to see that even though it did loosen, the rifle did not blow up, and the threads on the barrel and barrel extension held together just fine.

6. I managed to scratch and ding the heck out of the stock and receiver today. I have a lot of sanding and polishing in my future anyway, so no real loss there....

7. The muzzle brake worked very well, despite not being fully ported. I meant to mill rotated ports in it similar to the last brake, but was on a bit of a time crunch, so I just bored 7/16" holes down it's length, spaced .75" apart, center to center. It vented the expanding gases to the left and right of the shooter quite nicely, as my stepson can attest to, given that he was filming to the left of the gun about 15 feet or so away and still got knocked back by the muzzle blast. However, I think it can work better, and I want to play with the design a little in my 3d modeling program a little more. This is the same program I have been using to design the silencer I plan to build once my form 1 comes back from the ATF.

8. I need more ammo. Shooting this thing is a.d.d.i.c.t.i.v.e.

It is unlike anything I've shot before, and is an absolute adrenaline rush. You start squeezing the trigger, and just as soon as you realize the trigger completed its' break, you feel the WHAM as the rifle shoves you back, (no kick, just a nice shove), you hear a decent BOOM, then the shockwave of the round exiting the barrel hits you. You can feel it for minutes afterwards. It is also very loud. The first time we had the rifle clamped to the ammo crate and fired a round off, I said, "Hmm. That's not too loud, although it does have a bit of a blast to it. That can't be much louder or have much more recoil than a Mosin Nagant or a M1 Garand." I decided to shoot my M1 Garand real quick, just to see.
I was wrong about that, too.
The M1 Garand sounds and feels like a .22 by comparison. My sporterized M44 Nagant is a kitten next to the .50. I imagine if I got around to building that muzzle brake for my M44 that it would have a lot less recoil than it does. Food for thought.

So, now I get to attend to a very small checklist of piddly things, as well as finish the scope mounts and bipod before I sandblast the whole thing and apply some shiny to it thanks to the good folks at Lauer Weaponry.

For now, I'm going back to my 3d modeling program and do some fluid dynamics calculations to see what I can get out of that muzzle brake. I hope y'all have enjoyed everything thus far, I know I have.

Monday, June 13, 2011

Sunday, June 12, 2011

How I became a gunnie.....

For what it's worth, I do read a lot of other blogs, but rarely comment on them. If I say something, I like to take my time considering what exactly I want to say and what my point is.
While perusing some other blogs, an interesting question came up here, asking how any of us bloggers became gun enthusiasts. A lot of other bloggers have participated, and I figured I might do the same. I don't like to jump on the coattails of other bloggers, nor do I like to opine about subjects that many other bloggers have already written about at length. I'm not a widely-read blogger, and I'm not one to steal content or ideas from others. However, I thought this topic was fairly interesting, and instead of being rude and leaving my response in someone else's comment section, I figured I would bring my response over to my little humble space on the internets.

Thursday, June 9, 2011


Well, the .50 goes bang.

I finally got the headspacing set on the new barrel extension/chamber piece I made. This took a few days as I have been pretty busy with family stuff. However, I got it machined although it still needs some fine sanding and cleanup. The loaded rounds chamber fine, and the rifle locks up reeeeeaaaaalll tight. There is actually a bit of force needed to rotate the bolt and lock in a round of ammunition. I am fine with this. I managed to get the firing pin transfer bar finished, and threaded some holes in the bolt head so I could affix it to the bolt body. The finished product looks good and works great, at least on the bench.......

I didn't want to try to take the rifle to the range only to find out it didn't go bang for one reason or another, so I figured I would take some of the .50 BMG rounds I had here, take the bullets and powder out, and try dry firing the primers in the assembled rifle. This was not a bad idea, except for one thing.
Military surplus rounds often have REALLY HARD primers, and my poor little AR15 hammer spring just could.not.get.the.job.done.the.first.time. Or the second. Or the third, etc.
At first, I did have a problem with the firing pin not protruding far enough into the primer to light the round off. A few trips back and forth to the lathe fixed this, and of course, the first time it actually went bang, I had just finished filming and had neglected to turn the camera back on before pulling the trigger a 4th or 5th time. I was actually surprised it went bang the first time, it scared me silly. I looked around and said, "What the hell was that?!!!" before I realized that it was my rifle actually working.
D'oh. *Headdesk*

I was pretty happy that it had worked, so I went and retrieved another live cartridge to test with. I pulled the bullet and dumped the powder then put the case in the rifle Dammit.
By now, I knew I had plenty of firing pin protrusion, so I figured that the problem had to be the milsurp primers. Sure enough, I went and got my stepson to come out to the garage and hold the camera while I worked the bolt and trigger, and after about four clicks (and resetting the hammer each time with the bolt), I got a nice loud BANG out of the rifle. Unfortunately, my stepson was laughing so hard at each failed attempt of the hammer dropping he had quit filming, and when it actually went bang, he didn't have the camera running.


Okay, round number 3. Pull the bullet, dump the powder, and chamber the round, this time with the camera (my iphone, actually) running, I cycle the bolt, pull the trigger, wait a couple seconds in case of a hangfire, then repeat. After about 5 tries, I finally decided if I couldn't get anything out of it the next time I pulled the trigger, I would hang it up for the day. I pressed the record button on the camera, aaaaand......



I'm going to go to my local merchant of death (A.K.A gun shop) and buy a box of commercial ammunition for the rifle. Hopefully I won't have any issues with primers not lighting off with some American Eagle ammo. Once I have those in hand, it's off to the range to put a couple rounds through the gun, albeit with a loooooong string attached and me standing several feet back. So, the next post about this rifle should be a report on the gun successfully going BANG and sending lead downrange, or a report on how it failed miserably and sent steel gun parts downrange.
Either way, it's gonna be LOUD.

And I'll probably be smiling, either because I now own an inexpensive, functional .50 BMG rifle, or because I just created the most expensive noise maker ever and have to start building a new one.

Saturday, June 4, 2011

Pics I couldn't find

Here's the pics of the .50 rifle I could not find yesterday when I posted.

It still needs a little work to get everything 100%, but it's rough fit together for now. Before it gets Duracoated all the edges will be beveled and radiused, and any pits or scratches or oversights will be finished as well.

Friday, June 3, 2011

Still alive and kicking....

I'm still here, shaving big pieces of metal down into smaller pieces of metal. I have been waiting for the last week or so on my 4140 prehard to make the barrel extension out of. I finally got the metal in the other day and have been turning and milling my way to another barrel extension. I'm going a bit slow about it as I want this one to work 100% and chamber every round as it should. Unfortunately, the metal didn't make it in until this last Wednesday, so I haven't gotten too far on it.

I did do some work on the receiver/stock and bolt the rest of it together. I also threaded a small barrel extension onto the barrel, then I sleeved the whole thing to at least make the barrel look a bit longer. I could live with the original barrel length, but I have to admit I liked the final length a bit more. The larger piece of steel on top (about 6" long piece) is the material for my new muzzle brake I am working on. I liked the old design, but after doing a little bit of math, I think that I would be better served building a longer brake with more porting.

This pic doesn't show the finished stock/receiver assembly. For some reason, I seem to have lost the pictures I took of it the other day.

In other news, it appears that in regards to my next project, I will be able to build a .308 mag-fed bolt rifle fairly easily. I will still build a few more subguns of my own design (semi-auto, of course), including a Thompson knockoff, but I think I will build another rifle first. I still have the Suomi M31 to finish, but it's not too far from being functional as it stands.
As far as the rifle goes, it will likely be another tube receiver design, somewhat similar to this .50 I am working on, though much smaller and lighter. I have already decided to go with an AR trigger group for simplicity, and I also want it to be box magazine-fed. I haven't settled on a mag yet, but I'm thinking either AR 10 mags or something similar. The width of the receiver will probably limit my choices in magazine, though. I don't predict that it will be anything too wild, but I do want it to be a tack driver and not too unconventional in appearance. I've seen a lot of benchrest tube rifles out there, and while most of them are pretty nice, I'm not too fond of how most of them look. That has been a big setback in building my .50. I've tried to build a rifle that's not only functional, but blends a reliable design with a smooth look. I've rebuilt so many parts of this rifle not because they didn't work or because I couldn't make them work, but because they were designed around the Bill Holmes original design, which is......not that great looking. I was too anxious to build this rifle at first, and simply threw together a handful of parts in an attempt to have something that would launch .50 BMG bullets downrange. Over the last year or so that I've been building this rifle, I've acquired some new tools and some better tools, and I've been more than happy to use these new tools to build a better rifle. I should have done a bit more research before starting this build, because since I started building it, I've found several other rifles that were built around the Holmes design but were vastly improved. Let's face it, for those of you that have seen the Bill Holmes rifle, you have to admit that it really isn't that good looking. It does work, and I've seen several finished rifles that follow the Holmes plans to the letter and work just fine. I guess in retrospect the only things I've kept from the original design is the tube receiver and the barrel retention. Everything else is a conglomeration of what I've seen from other real .50 manufacturers, other home builders like myself, and whatever else I could dream up while sitting in front of the computer, milling machine, and lathe.

When I started this blog, I had most of the work already done, and most of my posts were over work that had already been completed. Now, I post as soon as I have a new piece finished. My spare time has decreased steadily over the last 6 months, and when I get into the fall semester later this year, I will be taking 18 hours of engineering and math classes combined, so I won't have as much spare time to build as I do now. I still plan to dedicate at least 8 hours a week to building guns, that's how I stay sane. So, after this summer, build posts will be less common, and most of my posting will be about other things. However, I will still be building and posting about it. There are just too many cool guns out there and too many ideas floating around in my head to simply hang up my tools and keep my nose buried in a book. If I get a chance, I'll take some pics of the rifle as it stands now and post them up later. I'm really, really hoping to do a test-fire of the rifle by the end of this coming week, perhaps the week after. I haven't built the scope mount yet or the bipod, but the material is sitting here waiting on me to finish the barrel extension/chamber area. Once the rifle is successfully test fired and I can see that everything works 100%, I will send the necessary parts off to be heat-treated, and while they are being treated I will finish up the bipod and the scope mount before applying a few coats of Duracoat.

Anyway, things are still on the move in the garage, but they're moving slower than I like.