5.56 M855 debate

[agalindo]

The bullet doesn't tumble because of the twist, it tumbles because of the bullet design, it's heavier towards the base so once it is upset the base starts to move forward. All FMJ pointed bullets tumble regardless of twist, that is as long as the twist is enough to stabilize it. The velocity of 2700 fps or greater is what makes the bullet fragment causing the larger wound channel.

[jeepinbanditrider]

Originally Posted by gimp297

DOse any one know why they stoped using the 1 in14 barrles. If they put the 1in14 on the M4 would it still tumble and then make big enough hole in the BGs.

Because it wouldn't stabilize the bullet and it would tumble in flight causing it to fly off in unpredictable directions. When they made the A1 mods they moved to a 1 in 12 in twist then the A2 got the 1 in 7. The 1 in 14 twist barrel would stabilize the 55grainers in warm temps but up in on the Arctic test ranges they found the round would tumble in the cold temps. So they tightened up along with other mods for the A1 modifications.

Check out the ammo oracle (do a google search I think the original website moved) it explains it all.

[Alaskapopo]

Originally Posted by trelane

Ya Think!?
I had a conversation recently with a federal officer comparing the merits of his M4 and my SKS. I informed him that quite simply he was outgunned. "But my M4 is automatic, and a much newer design". I then described the shortcomings of the 5.56x45mm bullet in comparison to the much more powerful 7.62x39Soviet used by both the SKS and the AK-47. Lets say it was an eye-opening experience for him. He was however quite impressed with my XD in comparison with his Glock. Sadly he still gets all his ammo for free...

you can't win 'em all...

You are the one that is out gunned. I would take the 5.56x45 even with ball ammo over the SKS. For starters the 7.62x39 is not that impressive there is a reason why the russians copied us and went with the 5.45x39. Most 7.62x39 rounds do not tumble or frag on imact. In fact many leave a wound that looks simular to a 38 special round nosed lead round. Secondly no top loading 10 shot carbine with crappy sights is going to keep up with a good AR in a CQB fight nor at long range.
Pat

[jeepinbanditrider]

I have to agree with Alaskapopo here. While the SKS is a good Carbine it's simply outdone by the AR.

The M43 x39 ammo won't upset and begin to tumble for 30cm. That's roughly a foot. By that time it's already made it out of the body. The Yugos made a round that tumbled in about half that distance by making the bullet with an air cavity at the front it's called the M67.

[spamlovr]

Originally Posted by captdecoy

Hornady TAP uses the same bullet,just loaded hotter. It's regarded as one of the best. Go with the 75 grain

The 75 grain TAP ammo uses an OTM style bullet, and fragments well becasue of it's length, not necessarily it's velocity.

Start here: The AR15.com Ammo Oracle

[f0cker]

Originally Posted by jtkratzer

This leads me to ask why people are building SBRs in 5.56/.223...as short at 10"...is it just the "coolness" factor that you have an SBR? What good does an SBR do you if the performance of the ammunition you're using with that rifle suffers more and more as you shorten the barrel.

What is the minimum length barrel on the AR platform that will work sufficiently with the 5.56 FMJ ammo, m193 or m855? 16"?

A lot of the REAL reason for an SBR is CQB...a 11.5" barrel is plain easy to move around a house with. 14.5" is easy, but not as easy. 20" sucks. But most people get an SBR because they can. I will next year hopefully.

[jtkratzer]

Originally Posted by f0cker

A lot of the REAL reason for an SBR is CQB...a 11.5" barrel is plain easy to move around a house with. 14.5" is easy, but not as easy. 20" sucks. But most people get an SBR because they can. I will next year hopefully.

Right, but the indoors for CQB, I'd rather have a shotgun than a rifle that isn't going to provide sufficient performance for the ammunition.

[Alaskapopo]

Originally Posted by jtkratzer

Right, but the indoors for CQB, I'd rather have a shotgun than a rifle that isn't going to provide sufficient performance for the ammunition.

With proper ammunition a 10.5 inch AR will provide sufficient performance and it has a lot to offer over the shotgun.Some advantages being very little recoil high ammunition capacity, much better if you come across a hostage situation. Shotguns are great breaching tools and they are good for less lethal applications. But in a gun fight give me a carbine or a rifle any day.
pat

[spamlovr]

Originally Posted by Alaskapopo

But in a gun fight give me a carbine or a rifle any day.
pat

There are many good reasons to use a rifle/carbine over a shotgun in a gun fight:
- Range
- More ammunition
- Easier and faster to reload and re-engage
- Capable of precision that many shotguns lack, or is hard to acquire for the shooter
- Lighter weight
- low recoil/easy follow up shots

I think that you will also find many police departments, while adopting the carbine, are also not relegating shotguns to long term storage. They have their place in many situations.

[jtkratzer]

Originally Posted by spamlovr

There are many good reasons to use a rifle/carbine over a shotgun in a gun fight:
- Range
- More ammunition
- Easier and faster to reload and re-engage
- Capable of precision that many shotguns lack, or is hard to acquire for the shooter
- Lighter weight
- low recoil/easy follow up shots

I think that you will also find many police departments, while adopting the carbine, are also not relegating shotguns to long term storage. They have their place in many situations.

And none of these things really apply to what I was talking about with indoors CQB.

Other than amount of ammo and speed of reloads.