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.



8 comments:

  1. Wow, that was a pretty of work.
    And why you choose Holmes design? A saw a plans of Browning .50cal rifle someday... but i suppose - it will be even harder to built.

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  2. It was a lot of work to build the way I did it, that's true.

    There are three single shot .50 designs that I know of, the Holmes design, the Maadi Griffin, and the Gunmetal Designs Big .50.

    The Big .50 is the best looking design, but the most involved. The Maadi Griffin does not appeal to me at all. The Holmes design was inexpensive, easy to build compared to the others, and left a lot of room for customization.

    I would LOVE to build an M2, but parts kits are running between 4-6 thousand dollars. Building one from scratch would be a lot of machine work.

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  3. Very well done Redneck. Your build and write up should be a 101 class. I hope you're getting a lot of hits because the entire build has been a thing of beauty. If I could only weld like that...

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  4. Thanks, Six. I appreciate your overly-kind comments. It's still coming together, slowly but surely I'll get it done.

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  5. Is Bill Holmes still alive?

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  6. That's one serious pierce of artillery. Wonder how much it'll cost to reload its .50 loads.

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  7. Sweden has the most strict weapon laws in the world, actually theres no equals - not even close. The obsession from our own government to unarm its own ppl can only be compared to other dictatorships.
    This is the only advertised democracy in the world where you dont have the right to defend yourself! If a maniac with a axe shows up in your backyard and he slips and hurt himself - YOU're the one who will face charges, and if you should fire at him with your hunting rifle you will end up in jail and the police will take your gun(s) from you, and also a life long banned weapon license. Even if you during the moose hunting season accidently shots for example a reindeer instead of a moose, you will lose your license and the police will take the rifles from you, they will take every chance they can to unarm the ppl.

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