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Posted: 5/16/2026 8:17:29 PM EDT
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Was not really sure how to title the thread. Had someone offer to me a 50BMG "project" rifle. It is a single shot bolt action that was originally made to be mounted in a tank barrel to use for shooting 50 bmg out of it as a training aid. This thing right here: https://americanapex.com/aimtest-devices/ The large aluminum part has been removed and it is now just a bare barreled action. Here are the pictures sent to me.    Could something like this even be turned into a functioning rifle? Apparently it has a electric solenoid to fire it instead of a trigger. So you would either have to make a trigger, or just use the solenoid. I would have no delusions what so ever of this being a 1000 yard match grade rifle. This would be nothing but a range toy. The tripod comes with it and it would possibly just get mounted to it, with some basic open sights. Just curious what some other people thing about this thing? |
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Very cool. It even has the advantage or being chambered in 50BMG unlike the M8C spotting rifles which uses the shorter, dedicated spotting round. I imagine a split clamp block could be used on the barrel and also attach to the tripod, a stock, or whatever. Something like this in concept:  |
 AIMTEST 120mm Quick Install with Title Card  AIMTEST 120mm Quick Load |
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Cool project. Looks like the hardest part of building a gun from scratch would all be done. Does the solenoid push on the sear on the bottom of the action to release it? If so, depending on how much force is necessary, a pivoting trigger with a lever could push up on that to fire the action. |
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Originally Posted By Postal0311: Cool project. Looks like the hardest part of building a gun from scratch would all be done. Does the solenoid push on the sear on the bottom of the action to release it? If so, depending on how much force is necessary, a pivoting trigger with a lever could push up on that to fire the action. I do not own it, me and the current owner have not started serious talks about buying it just yet. I just wanted some opinions about it before I went much further. I do not want to end up with something that would be a endless money pit and end up spending about as much on it as if I had just bought a commercial single shot bolt action. I know nothing about the way the solenoid operates, but I had the same thoughts as you, in that it does look like it would simply push up on (what appears to be) the sear on the bottom of the action. If that is the case, then it might be possible to modify the solenoid housing and install a simple pivoting trigger. The pull weight might be shit, but it is not a match grade rifle. I may contact the owner again tonight and ask. |
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$600 and I have a new project. This thing is CHONKY. Pictures do not convey the size and weight of the action alone. It is a hair under 2.5in in diameter and 12.75in long. It has two locking lugs on the bolt. That is a sear on the bottom of the action. Pushing it will fire. The electric solenoid simply pushes on the sear. He says it works, I have not tried it yet. The barrel is like a javelin. Son of a bitch is 45 inches long. He said he thinks it is a modified browning M2 barrel, and I look up those barrels online and sure enough, it looks like a modded one. Google says the M2 uses a 45 inch barrel. It has some type of a stainless cone type muzzle device on it. I am hoping I can use my barrel vice and remove that thing, leaving the muzzle threads. It has two flat spots for a wrench. Hopefully they are a thread size I can find a muzzle brake to fit. The collar goes around the barrel and is held on with 3 set screws. You thread the barrel in and then use the little locking block to hold it in place. Like the video above show. He thinks that the headspace may be adjustable by way of that collar. I have no idea about the tripod.            |
| Yeah. That's an M2HB barrel. All the original M82 barrels were turned down M2 MG barrels until they went to Batten Machine chem etch barrels for a long time. |
I hated going to weddings. All the grandmas would poke me and say "You're next". They stopped that when I started doing it to them at funerals.
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Sic semper evello mortem tyrannis
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Originally Posted By 50cal: Yeah. That's an M2HB barrel. All the original M82 barrels were turned down M2 MG barrels until they went to Batten Machine chem etch barrels for a long time. I mean, it would make sense. Why go through the trouble to make a barrel in house when you can just get one pre made "off the shelf" and then just design your receiver/action around the barrel. |
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I put the barrel in the barrel vice and tried to remove the muzzle thing. It did not want to budge. I heated it with a propane torch and gave it another good tug and it broke loose with red locktite falling out of it. I cleaned it with with a wire brush and measured. The OD of the threads measured .990 and according to my thread gauge, it is 20 tpi. So I am guessing this is most likely 1-20 threads, which appears to be a very uncommon thread. No 50bmg brake out there has that thread size. The two most common I see is 1-14 and 7/8-14. So I bet it could be turned down just a little and rethreaded to 7/8-14. I cleaned the solenoid with a wire brush and it says it is 24v. |
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I actually have 1 round of 50bmg I keep on my desk for display. It is a live round. I took the striker out of the bolt (was actually pretty easy) and then installed the barrel and tested the round in the chamber. The bolt was stiff to close, like the headspace is too tight. There is a SN on the barrel, but it does not match the receiver. Now I do not know if the barrel was numbered to the receiver, or if the number on the barrel is just unrelated. Seeing how the guy said he saved it from the scrap bin, it seems like there is a chance the barrel and receiver are not original to each other. I happened to notice a set screw in the front of the receiver I overlooked before. I got looking a little closer and the receiver has a threaded sleeve/collar (whatever you want to call it) in the receiver threads that the barrel tightens against. it has two notches for being able to turn it in/out. That set screw locks it in place. So it appears the headspace could be set/adjusted by loosening that set screw and turning that collar in/out. So I will eventually need to rent/borrow a headspace gauge when the time comes. 
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I have rented a set of headspace gauges from 4D reamer rentals yesterday. Once they get here I will check and adjust the headspace if needed. Once that is checked, I will move on to the rest of the build. The receiver is 10 inches long and I found a 10in section of pic rail on ebay. So I will drill/tap and mount it to the receiver. I have not fully figured out a stock just yet. Also have not decided if I want to try and make a trigger or try and use the electric solenoid. I am leaning towards making a trigger, as I kinda do not really want to rely on a battery. Also that solenoid is very large. |
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Albeit that it's a single shot, it looks like the perfect setup to make a remote controlled 50Bmg rifle. Top it with a thermal or digital scope with wifi and your golden. SJC 50 Bmg Remote |
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Originally Posted By SGT-Fish: I think id be working on a mount for it rather than a stock. Mini AT gun! I have thought about using the tripod it came with and making a couple clamps that go around the barrel and then fit into the mounts on the tripod. However it seems the tripod is worth more than what I paid for everything. https://www.ar15.com/forums/armory/Can-anyone-ID-this-tripod-/22-562552/ I could possibly sell the tripod to help pay for making the stock. |
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Got a couple gun shows coming up locally. What is a ok price for surplus ball 50 bmg? Most 50bmg I see online is new target style ammo, and I do not see much for just run of the mill surplus ball. However most local gunshows seem to have at least a couple people with surplus. Again, I know this is not going to be a match grade accuracy gun, so I do not want to waste target/match type ammo in it. So military surplus ball is fine. |
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Originally Posted By Jeeps-And-Guns: Got a couple gun shows coming up locally. What is a ok price for surplus ball 50 bmg? Most 50bmg I see online is new target style ammo, and I do not see much for just run of the mill surplus ball. However most local gunshows seem to have at least a couple people with surplus. Again, I know this is not going to be a match grade accuracy gun, so I do not want to waste target/match type ammo in it. So military surplus ball is fine. A couple years ago the cheapest I was able to find was Federal and Barrett. Most of the surplus I see is higher end projectiles. |
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People who don't like motorcycles are just... weird.
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Here are my plans for the barrel. There is the large section that measures just a hair over 2in. There is then some threads, a keyway cut, then it steps down twice till it goes into the receiver. I want to take the barrel and machine it down to the same diameter it is at the breech end, up to the large section, removing the threads and that keyway cut. I then have bought a section of seamless 2in od, .188 wall seamless tubing. It will only need to be opened up just a little. The OD of the barrel at the breech end is 1.675, the ID of the tubing is 1.615. Then use that as a light press fit sleeve over the barrel, to make it the same diameter from the receiver to that large section. That way it will look more like a normal barrel where there is a shoulder on it that tightens against the receiver. The two step, I then want to just put a 45* taper on them just to make it not a flat step. I called a couple local gunsmiths and their lathes are not big enough for this barrel. I tried a local just regular machine shop, who has a lathe big enough to fit it, but once they saw it was a gun barrel they got spooked and refused to touch it. They gave me a name of another shop I am going to try and contact monday if I can remember.  Originally I was thinking just have the barrel re threaded from 1-20 to 7/8-14, as the 2 thread sizes for 50bmg brakes I see are 1-14 or 7/8-14. But threading is kinda expensive when you have to pay someone to do it on something this big. I can not easily just mail this thing out to have someone do it. So I got looking at that muzzle device. It is just a tapered cone of a sorts (you can see it in the above picture). I found a very reasonably priced 1-20 tap on ebay (less than $20) and bought it. I tested that muzzle device and I can confirm it is 1-20 threads. So I chucked it up in my lathe and using a boring bar, bored out the inside of it to be the same ID all the way through. I then took the tap and just continued the threads all the way through. My idea is to take a piece of bar stock I have, thread one end to 1-20, then thread it into this muzzle device, leaving some sticking out, then thread that to 1-14 to match the available muzzle brakes. Basically making a thread adapter. Anything I can do myself to save having to pay other people is a plus. I have it threaded, I still need to shorten it a little. Then make the thread adapter. Just doing things in my spare time.  I also went to a local gun show and looked for 50bmg ammo. I found a couple people selling surplus for $7 a round LOL. I can get PMC new production for 4-4.50 a round online. But I did find a guy who had 24 rounds of linked ball for 3.50 a round. So I bought that. I get home and looked it over and noticed the headstamp was not LC. I never even though to check the headstamp at the show. The headstamp is IK 88. Doing a little looking online, turns out this is Yugo and is CORROSIVE! Fuck. I treat corrosive ammo as if it has herpes or the bubonic plague. I know a lot of people corrosive ammo is no big deal, but I hate it and I refuse to shoot it in any of my guns. So I will try and sell it locally and check the next gun show next month, making sure to check the headstamp this time. If I have no luck finding any at the next show, I will just order some PMC online. |
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