Aliens are coming...

[benbangui]

I just sent this text to a buddy of mine that is a ballistic genius. But as I was re reading the text I thought... well this would be a fun open discussion

Please don't turn this into a CA legalities discussion



So:
Ballistics. I have read about it already... just wanted your opinion ��

Ar10 308...

10.5 pistol build... slightly out of the question... balistically might as well build a .300blk

I read 12" was bare minimum?

At that point why not just do a 13.7 with pinned flash to OA 16.1" so you don't have to have a "funny stock". (I know the intent thing... I still chose to use that wording because this is a "fun" thread, let it go...)

I'm building a rifle to fight some aliens... 5.56 isn't enough to me... availability of 308 is the next standard choice. I wanna be able to "run and gun it" so I want as short as possible.

But ballistically is 13.7 stupid?

Thoughts ��

[benbangui]

i just want a battle rifle that hits harder then a 556... I'm not concerned with range. It would have a 1-6 or red dot on it.

Like if there was a alien in your house, down the hallway right now...
308 shorty or 556?

[DArBad]

Againts marauding aliens, I prefer a true " battle implement ". The M1 Garand with all internals and sights updated to modern standards. I like the punch of the 30.06

[Xanthippus]

7.62x39. Cheaper than both .308 and 5.56, very plentiful, and very effective.

[MarikinaMan]

Ive read some cases where a factory issued short barrel had a different twist rate vs a 16". Good luck on your project.

[CandG]

7.62x39. Cheaper than both .308 and 5.56, very plentiful, and very effective.

This is probably the right answer.

300BLK is good too, and probably what I would choose for an AR, but the better choice for this, IMO, is just an old-fashioned AK in 7.62x39. You can shoot steel-cased ammo at aliens all day long for 22 cents a round. With 300BLK you'll go broke before the second spacecraft full of alien invaders lands, and there won't be enough time to take out a second mortgage.

.308 SBRs are just silly I think. Aside from custom handloads, that cartridge was really never meant for anything less than an 18" barrel. Shorter than that, and the powder is still burning long after the bullet left the barrel - The sound and flash will be insane (but cool though)

[ar15barrels]

Ive read some cases where a factory issued short barrel had a different twist rate vs a 16". Good luck on your project.

That's common sense.
Velocity is a factor in bullet stabilization.
As you decrease velocity via shorter barrel length, you need to spin the bullet faster for it to stabilize.

As a practical example, 77gr bullets will usually stabilize in a 20" long 1:9" twist barrel, but often do not stabilize in a 16" 1:9" twist barrel.
The loss of velocity in the shorter barrel of the same twist rate causes the bullets to be unstable.

[Mag+1]

...before the second spacecraft full of alien invaders lands...

Maybe he is referring to these types of aliens, operating these types of "spacecraft" ...

[Brush Guard]

Meh, I’m thinking space aliens since this thread is supposed to be fun.

But for the OP…
I’m no expert but for .308, 16” seems to be the shortest popular length.
18” is as short as I like to go. A collapsible stock helps somewhat if wanting to keep it short. Also maybe run with no muzzle device to help keep it short.

Although I like having muzzle devices to help protect the crown.

I would only use 5.56 M193 because I want to minimize the green acidic alien blood on my belongings.

Hopefully you can avoid nuking it from orbit.

[edgerly779]

My blaster is 6.8 spc pistol close range and 6.8 cqb rifle for mid range and m1a beyond that.

[Opappy]

I'll take a 12 gauge. Buckshot if they're small and fast. Slugs if they are Big and slow.

[Endless]

.308 is the best round of the 3, regardless. Not a fan of 7.62x39 never have been since the 1990s when I sold all my AKs and Mac90s. Tried an AK pistol in 2013. Blah. AKs for me are good plinking toys and that's about it.

Price isn't an issue unless you're shooting a 20 mm or 50 bmg.

With the .308 in all reality you can use 11.5-18 inch barrels and be just fine.

They had a .308 AR pistol I almost bought before I left Maine but changed my mind. They were well under $2000. Not the bull**** $5000 price California residents would pay. 😂

[benbangui]

I'll take a 12 gauge. Buckshot if they're small and fast. Slugs if they are Big and slow.

This is honestly probably the best answer lol

But it's just not cool enough! I wanna wast thousands of dollars for minimal gains!

[benbangui]

That's common sense.
Velocity is a factor in bullet stabilization.
As you decrease velocity via shorter barrel length, you need to spin the bullet faster for it to stabilize.

As a practical example, 77gr bullets will usually stabilize in a 20" long 1:9" twist barrel, but often do not stabilize in a 16" 1:9" twist barrel.
The loss of velocity in the shorter barrel of the same twist rate causes the bullets to be unstable.

Hey! Hehe I was gonna call you for the barrel chop if I go that rout

[benbangui]

so here is the thing... I know 308 will have unburt powder and is more effective with longer barrel...

The real question, is what's more powerful from 5-50-100 yards...

13.7 308...
76.2x39...?
6.8
12 gauge slug... no?

Am I missing anything abyone else said?

"Battle rifle" also implys easy/cheap ammo... so 6.8 and 300blk isn't really in that ball park? If I'm wrong please continue

it really truly is a ballistics question. Someone with charts already in there head to yell out. I just don't have that info rattling around in my head...


Again I'm not worried about it being efficient, making it to the calibers full potential...

Im just curious what hits hardest at close range? Would 13.7 be acceptable for close range? I guess I need to just chop it Randall and then crono it lol