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Stupid questions regarding paradox type rifling in a BMG chambering

[486]

[486]

ugh, that guy again?
Joined
May 19, 2020
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pine city MN
So, I've got a stellite liner from a .50 barrel, it's about 9" long
I could buy a couple more of them and make a 32" barrel after accounting for making the chamber and all outta a separate piece of bar stock

Got to thinking about just extending the barrel out past the 9" of rifling with smoothbore DOM reamed/burnished out to .509 or something
Then later on I got to thinking about just having 20" or so of freebore at .510, then just have the liner at the muzzle end.

650 grain bullet going 2500fps or whatever is gonna be quite the 'bang' when it hits the rifling, but putting the extension on the other side would have leakage channels from the grooves in the bullet. I don't think the smooth barrel extension would reduce the spin of the bullet significantly but that's just seat of the pants idiot talking

Buying a couple more would be an additional 60 bucks. Prolly worth it to just sleeve them together with DOM and abandon the whole thought experiment.
Sadly M3 barrels aren't $200 any more, and M2 barrels are waaaay out there in price

Thoughts?
 
pfff
buncha fearmongering clickbait

Interested to see what it was, everyone seems to say shit ammo. All I remember was that it was the saboted stuff
That SLAP stuff is way interesting, the swedes are still using the 308 version that we abandoned long ago for poking holes in the side of m60 barrels
 
Chamber it for .500 S&W instead and build a single shot SBR, or weld a Form 1 can on it to make it 16”.

Twist rate for .50 BMG is 1:15”, .500 S&W is 1:18.75”. Wikipedia claims the land diameter on the .50 BMG is 0.498”, should be fine with a .500” jacketed bullet.

Would be fun to shoot deer with and a home built gun pushing a 300 gr bullet at 2000 fps has to be much safer than one pushing a 650 gr bullet at 3000 fps.









































Or you could just shove it up your ass. :flipoff2:
 
The bullet needs to engrave the rifling right at the chamber before the velocity gets too high or it will probably kaboom when it hits the lands at freebore speed. It could just wipe the jacket off, and kaboom on the next round?
 
Gatorgrizz27 said:
Chamber it for .500 S&W instead and build a single shot SBR, or weld a Form 1 can on it to make it 16”.

Twist rate for .50 BMG is 1:15”, .500 S&W is 1:18.75”. Wikipedia claims the land diameter on the .50 BMG is 0.498”, should be fine with a .500” jacketed bullet.

Would be fun to shoot deer with and a home built gun pushing a 300 gr bullet at 2000 fps has to be much safer than one pushing a 650 gr bullet at 3000 fps.
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hard gay
you should be ashamed of yourself
 
Wtf are you trying to do? Honestly pjecing together a barrel sleeve just sounds dumb. Youll have to clock the sleeves or the barrelling wont line up. Youll just end up with garbage bullets coming out the barrel.
 
Stuck said:
Youll have to clock the sleeves or the barrelling wont line up.
Click to expand...
trumpwrong.jpg
the lands don't really need to be aligned, it only causes a bit of gas leakage when they aren't which might eventually cause some erosion eventually

but it's just a low volume rock thrower I'm tossing together for laughs
if I can halve the project's overall cost by going with a pieced together barrel, all the better
 
[486] said:
trumpwrong.jpg
the lands don't really need to be aligned, it only causes a bit of gas leakage when they aren't which might eventually cause some erosion eventually

but it's just a low volume rock thrower I'm tossing together for laughs
if I can halve the project's overall cost by going with a pieced together barrel, all the better
Click to expand...
I really don't know what you're trying to do but... you're right, the rifling really doesn't need to be aligned. I never would have thought about that if not for this thread. Learn something new blah, blah... :beer:
 
I guess it depends on the accuracy youre going for. If its just lob heavy bullets at a couple hundred yards its probably fine. If youre trying to hit man shaped targets at 600+yds youre probably gonna have issues.
 
Stuck said:
I guess it depends on the accuracy youre going for. If its just lob heavy bullets at a couple hundred yards its probably fine. If youre trying to hit man shaped targets at 600+yds youre probably gonna have issues.
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it'll never see anything that isn't bottom barrel surplus ammo
probably won't get anything but a crappy set of airsoft gun iron (plastic) sights

Know what, I'm just gonna give it a go with a chamber, 1/2" of freebore, 9" of rifling and 20"+ of .510 smoothbore
I have very low expectations for accuracy, and it'll probably surprise me nonetheless

https://www.gunpartscorp.com/products/1570740
is the piece of stellite liner that I got for cheapcheap
 
Why not do a single shot break action pistol?

It you're gonna have something crude and inaccurate it may as well at least be somewhat handy. Then why you get tired of firing $5 bills you can whip up another one in a cheaper caliber using all the lessons you learned on the first.
 
arse_sidewards said:
Why not do a single shot break action pistol?

It you're gonna have something crude and inaccurate it may as well at least be somewhat handy. Then why you get tired of firing $5 bills you can whip up another one in a cheaper caliber using all the lessons you learned on the first.
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What idiot is paying $5 per round? M33 can be found for $2.65. Fuck API is $3.80. :flipoff2:
 
Aisin said:
What idiot is paying $5 per round? M33 can be found for $2.65. Fuck API is $3.80. :flipoff2:
Click to expand...
I just figured prices doubled since I last checked. :laughing:


Even still, $2/bang sure does suck some of the fun out of it.
 
arse_sidewards said:
Why not do a single shot break action pistol?
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gay
even a 16" barrel seems like it'd be worthless, just about may as well be a .45-70 with how slow the powder burn rate is
plans is for looong barrel and an interrupted thread breech cap
though a bit more than the 5 threads of engagement it looks like the serbu one has, prolly go with a full inch of thread engagement with something like 8 tpi
 
[486] said:
gay
even a 16" barrel seems like it'd be worthless, just about may as well be a .45-70 with how slow the powder burn rate is
plans is for looong barrel and an interrupted thread breech cap
though a bit more than the 5 threads of engagement it looks like the serbu one has, prolly go with a full inch of thread engagement with something like 8 tpi
Click to expand...

Fair point on the powder. I figured if you were happy with 10moa you'd also be happy with 1200fps.

If you wanna do fancy machining you can get equivalent thread root cross sectional area by doing a coarser multi start thread.

For maximum troll factor you could extend the cone of an NPT thread and then do an interrupted thread breach. It would piss off both machinists (the uptight tool room kind who "take pride in their work" and get pissed off when you CNC dick shaped pockets into things to add lightness) and firearms people.

You would need a taper attachment or a CNC lathe (or a powered compound feed, lol).
 
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or just an 8tpi thread because that's what my leadscrew is so it simplifies threading
got a metal shaper so making a conventional interrupted thread is very easy
headspace doesn't even really matter
Might just chamber it nearly straight walled because the fired brass will prolly just be getting used as 12gaFH stock. Leave a little 3/8" or so of proper neck support for alignment, have the case shoulder be whatever angle the drill bit is.
Could chamber it with a boring bar, but why bother when the brass is gonna be fireformed out straight anyways.
Breechplug will prolly just be a "half moon" that grabs onto the rim, handles headspace (holds the case head against the breechface) just fine and can nearly eliminate any unsupported case head.

I'm having difficulty finding it but there was some heavy MG that used a cartridge as the charging handle, there was a circular cutout the size of the base, and it had a protrusion into that cutout that grabbed onto half of the rim, the half that was to the front of the gun, so when you pulled on the case body it worked as a charging handle. Zero moving parts, just clever machining.
That, but as a bolt face. Pressed up tight against the chamber with zero unsupported case head.
 
okie dokie
bought an m2 barrel
it's got some bad scoring in the throat of the chamber, straight to bore axis doesn't follow rifling twist, on the lands and grooves pretty equally, probably 5/8" to 3/4" long from where the throat is

only thing I can think of would be cleaning rod damage, because even something like a rock caught in a bore brush would follow the twist of the rifling
Anyone seen something similar?
Tried getting a couple pics but they suck, here they are anyways
20220211_160138.jpg

20220211_160122.jpg
 
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