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Discussion Starter · #1 ·
I've been looking at building a 50bmg single shot rifle for some time . I have the two common sets of plans you can find on the net .
Searching around for info I came across the serbu RN-50. It uses a threaded breach cap .
It seems like the easiest way to build a 50bmg rifle .
Wanted to know what you guys think of it .
What thread pitch would you use for the cap.
 

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IMO you can do better.
I think the novelty of a 50BMG going bang will soon fade an you will be stuck with clumsy inaccurate weapon.

If were going to build one if these ( im not)
Id use a 16 pitch thread what ever size the blank OD is.
Mosburg sells chambered blanls for about $175.

A standard cal rifle with a take off barrel could likely be built for about $ 45
 

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aka: SDK1968
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I've been looking at building a 50bmg single shot rifle for some time . I have the two common sets of plans you can find on the net .
Searching around for info I came across the serbu RN-50. It uses a threaded breach cap .
It seems like the easiest way to build a 50bmg rifle .
Wanted to know what you guys think of it .
What thread pitch would you use for the cap.
if by 2.... you mean Marks & the Holmes plans? id use Marks... he sells tons of these & they are made better than the Holmes plans.

dont get me wrong, back when we first did the Homes plans? they were all there really was.. they made a functional, fairly ugly, clunky rifle in 50bmg...

better advancements out there now.

i still tell everyone who builds a 50bmg to use a tri lock head ... you only have to see 1 bi-lock head fail to never want to see that again. it takes your more machine time & better set up.. but your life is worth it.

pic of bi lock....

pic of tri lock...

Cylinder Gas Automotive tire Auto part Nickel


Drinkware Wood Paper towel Tableware Serveware


go for some version of TRI LOCK......
 

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in the blueridge mtns
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It seems like a really cool idea to me. I was thinking about it recently. Fine threads or rotating interrupted coarse thread? Kinda a CZ 24-26 thought?
 

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Discussion Starter · #5 ·
if by 2.... you mean Marks & the Holmes plans? id use Marks... he sells tons of these & they are made better than the Holmes plans.

dont get me wrong, back when we first did the Homes plans? they were all there really was.. they made a functional, fairly ugly, clunky rifle in 50bmg...

better advancements out there now.

i still tell everyone who builds a 50bmg to use a tri lock head ... you only have to see 1 bi-lock head fail to never want to see that again. it takes your more machine time & better set up.. but your life is worth it.

pic of bi lock....

pic of tri lock...

View attachment 40321

View attachment 40322

go for some version of TRI LOCK......
I wish I could buy a barrel extension
And bolt head .
My plan was todo some thing like this .

So I would then need to thread the extension to match my barrel and make the rest of the recivier .
I just don't have the indexing heads or rotary table to make the lugs my self :( sad face .

I had a chance to buy a set dirt cheap but I forget what happen . If I remember right my debit card got stolen .
 

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in the blueridge mtns
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There are two trains of thought there. A "twist and turn" interrupted cap or a fine thread screw on cap. Even a coarse thread cap may have it's advantages. It's a 50 BMG being fired next to your head. Start with point a before going to point b please. Pressure and thrust. Not saying I haven't been thinking about.
 

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Discussion Starter · #9 ·
There are two trains of thought there. A "twist and turn" interrupted cap or a fine thread screw on cap. Even a coarse thread cap may have it's advantages. It's a 50 BMG being fired next to your head. Start with point a before going to point b please. Pressure and thrust. Not saying I haven't been thinking about.
I'm a far better machinist then a engineer lol .
 

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Discussion Starter · #12 ·
& it was my fault for moving from your threads to the bolt lock...

gun in your pick looks nice..

this is Marks cheapest option: http://www.serbu.com/img/content/rn-50.jpg
That's what I was thinking of doing .
I could do that with no cost other then the barrel blank with the scrap metal I have .
Just am stumped on what threads for the breach cap.
 

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I wish I could buy a barrel extension
And bolt head .
My plan was todo some thing like this .

So I would then need to thread the extension to match my barrel and make the rest of the recivier .
I just don't have the indexing heads or rotary table to make the lugs my self sad face .

I had a chance to buy a set dirt cheap but I forget what happen . If I remember right my debit card got stolen .
I think you would be better off doing a build with a bolt .
Marks setup has some issues IMO . The rail on the hand guard is the most obvious .

I don't know why your in the dark on the thread pitch I posted one of the most common .
if you want a conformation then here is what one of the best actions uses to retain the barrel in the business , here is a link
http://www.accurateshooter.com/gear-reviews/monster-bat-machine-50-bmg-action/

Its a 1.5" -16 thread .

I have a commercial barrel here off a bolt action an its also 1.5" but its a 12 TPI . like a MC Millian uses there actions have a 1.5" long thread BTW

Earlier Years - Lilja

Id go with a 16 Myself . the amount of threads is important as well .
keep im mind if you going to be screwing the cap on an off all the time then tread damage on a finer thread will be more likely .

Im sure Mark did some calculation on his offering but what one must consider is if you get a case head separation the entire breach cap becomes the force that the pressure is acting on not just the diameter of the case head .

Not to be rude but if the Serbu 50 was in any other calibure it would be a laughing stock any were you took it . I have seen some of your work an I encourage you to take it up a notch IMO you can do better .

Id be leary of taking advice from guys here who have never built a thing but talk like they have some knowledge . I am giving you threads that work to keep a barrel in a bolt action . I cant comment on the seubu set up has more thrust on it in a case separation than a bolt gun or not .

I don't know if any of his guns have been built yet ? I know there is a bunch of guys waiting for stuff from group buys from quite awile ago before this thing was designed an offered in a different pre buy .

I saw bolt heads some were for sale ( two lug ) a while back for about $100 .
Ill see If I can find to link .

you don't need a rotary table to make a barrel extension you just need to lay out were to mill an do it .
The corners can be done with a file .

Id be more worried about the type of metal a cap is made form an the temper of it .

I think that set up is sort of a joke unless you just want to hear a 50BMG go off . the gun is also pretty light better plan a really serious brake .

I considered making one of these in 243 Win just for giggles as I could do it for about $40 if cobbled up some AK FC parts . with a $175 barrel an the material used on a 50 I would think the gun could be made for about $ 300 with a AR FCG an a few store bought parts .
I sure the hell would not mount scope on the float tube were a section of it is unsupported an also is affected by the Bipod . Bad set up IMO .
 

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aka: SDK1968
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there are a couple guys out there who make trunnions & bolt heads for 50 bmg's....

if you check over at biggerhammer you might find someone who will sell you one.
 

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Discussion Starter · #17 ·
there are a couple guys out there who make trunnions & bolt heads for 50 bmg's....

if you check over at biggerhammer you might find someone who will sell you one.
I'll check that site out .

I wish I could make this out of stainless I got no work at my day job and a crap ton of 316. Could say I'm making a fixture lol .
 

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My Pa and I built one up many many eons ago,,mid60 ish I'd have to say and we used a Mauser receiver and bolt assy. from a 13.2mm anti tank gun and that thing was the shits. Of course back then we were never able to find any scope to hold up to the recoil and ended up with a Lymann receiver target peep and a hooded front globe. A nice accurate set up,, but far from ideal sense you could shoot WAY further than you could see your target!!!

Now ,,IF you could possibly even find one nowadays would be another question all together??? I doubt it seriously ?? And if you did ,,it would probably be worth way more original as is,, compared to what it would be worth for parts and nothing you'd ever cut up!! If the values of a normal K98 are any indicator I can't even imagine what one of those anti tank Mausers would be worth nowadays in all original condition?? A Substantial amount I'm sure. Probably as much or more than a modern 50 BMG would cost more than likely?

The one you showed looked very much like what we built, a plain chassis but we did use the original butt stock end from the Mauser modified to fit the steel chassis we built.

But any-hoo,, that was what we used way back in the prehistoric period to build ours. It worked great BTW and never failed to turn heads and ended up being very very accurate,,,best we could tell??? Anything more than around 800-900 yards with open sights was pretty much a waste sense you couldn't even see you target much after that. But anything up to that ,,it was deadly!!!

I know it may not be much of a help, but that is what we used way back during the days of the dinosaurs!! I wish I still had the original Mauser we used though!!!:bawling:

In case you'd never seen one,, here is what we used ,,,,,,,it may give you some design ideas?

https://video.search.yahoo.com/vide...8&sigi=12bidvi0u&hspart=mozilla&hsimp=yhs-004
 

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in the blueridge mtns
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I had never seen a 50 on a mauser action before twa! Thanks for sharing that one. I have seen things that sit on the AR15 lower tho. Hmmm.
 

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:lolup: Yup,,,it would be ,,"a cold day in Hell" before I ever put a 50 cal on an AR platform lower!! No Way In Hell would I ever trust an aluminum receiver to hold up to those kind of pressures!!!!!!

Bad part ,, with the Mauser receiver we built it was still in the 40 lb range like the original, so not really a great woods gun,,,,

unless the woods your shooting in was 2 miles away across-ed a valley!!! Then you'd be Golden,,as long as you didn't have to move that damn howitzer,,,and that's damn near what it was IMO!!! A real beast ,,,,,but seriously fun!!

Of course when we built it you could still snag a case of 50 cal for next to nothing sense no one wanted it or could use it in anything made back then. I remember paying 15 bucks for 2 cases of 50 cal back in the day, hell you can barely buy a 50 box of target 22 for that nowadays!!! Gone are those days,,,,,
 
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