7.5" AR ballistics

[298436]

Solid question rob_s.

I don't buy the argument in the 'magazine. 3 rounds in a half-inch group at 50yds "without breaking a sweat". Yeah right. I personally have ...shall we say supervised...the instruction of many "normal" shooters and you'd be amazed how many couldn't crack 4moa. 1/2" at 50yds = 1 MOA.

Less than 1/10 people even got close to 4moa - as in, reliable -- on demand 4moa, consistently. This is prone, supported with a rifle sling. If he did it from a bench, I would understand the accuracy statement, but not that conflicts with this statement: "I defy anyone to tell me that they can't take down a bank robber or an errant gunman wrapped in body armor with an M7A1."

You definitely will not be able to use a nice bench with a rest on it and bags in that situation.

Moreover, many normal home defense AR15 owners who also like to blast would be served just fine with a 16". 18" gives you better velocity but for urban use I would use a 16". 7.5" is a movie or toy upper, IMO.

[Godallmighty]

I think it's an "unfair" comparison that people tend to compare a 7.5” barrel to a full length rifle or a carbine length barrel. They are not intended to be used for the same type of distance or environment... It's like comparing a Ferarri to a Fiat, cuz they both are italian!

a 7.5” barrel (or a 10.5) should be comparable to a SMG! Meaning a 7.5” AR... compare it to a 9mm SMG... that would be more equal and more realistic! (and they would be in the same size) If you want a rifle or carbine with accuracy and range, go by rifle or carbine. You want a 5.56 SMG... 7.5”, 10.5" or the "Commando" 11,5" are relatively OK!

If you intend to engage targets at 300m+... 7.5” is useless... but for targets around the 50m rage it works ok, and the 11.5" can without problems reach out to 300m at will, if you are not a total "nube" behind your rifle!

[TiroFijo]

So, can I ask:

Does an 7.5" AR beats a 9 mm SMG, in:
- penetration against Level IIIa vests (I assume yes)
- permanent cavity damage (?)

We know by DrGKR the recommendations for 9 mm ammo, do the same choices sitll hold true at the slightly higher velocities (longer barrels) of a SMG?

What are the best ammo choices for an 7.5" AR?

Is there a (marked, slight, or?) difference between a 10.5" AR and a 7.5" AR regarding terminal ballistics and fragmentation range?

To my very ignorant point of view, an AR barrel is better sized at 11.5"+, those 4" don't seem like too much in size unless concealment is a requirement.

[Godallmighty]

I’m not an expert, just a user so i dont know the numbers. I have 3 rifles, LMT Patrol Rifle (carbine) , Elisco 11,5” and some cross breed 7.5”. (Work Executive Protection) ) 90% of the time I carry the Elisco, but when “fancy” I carry my x-breed!

I wouldn’t consider my 7.5" to be able to take out targets beyond 50m, and using Norma 55g lead tip they would not be able to penetrate a class III BA... but luckily most bad guys don’t carry BA! On a soft target you could probably F***F*** the exit wound when using the Norma Ammo! (It's intended for deer hunt, and has excellent expansion capabilities!)

[rob_s]

Outside of penetrating soft armor, and operating under the assumption that the round isn't going to expand, conventional wisdom appears to be that you'd be better off putting a 9mm hole in someone than a 5.5mm hole.

Is this hunting ammo you're using in the 7.5" 5.56 guns expanding/mushroominig/fragmenting in soft tissue at close range?

[Godallmighty]

correct! the DoD issued 5.56 has to high velocity on close range, it was never designed for CQD!
Using a std issued military round on close range is ineffective! It has a too high velocity to deliver any punch into target!
A hunting round on the other hand has a lower velocity, and is designed to be used on shorter range!

[geminidglocker]

So the Author got paid buy Hornady and Troy. This is nothing new. Don't beleive everthing you read. Either that or the trauma plate was made of wood. Disregard the article. 99% of SWAT magazines readership is mall ninjas anyhow.

[Jack-O]

Outside of penetrating soft armor, and operating under the assumption that the round isn't going to expand, conventional wisdom appears to be that you'd be better off putting a 9mm hole in someone than a 5.5mm hole.

Is this hunting ammo you're using in the 7.5" 5.56 guns expanding/mushroominig/fragmenting in soft tissue at close range?

Seems to me that the ONLY reason for owning a 7.5 AR is for penetrating soft body rmor. It would not seem to be good at anything else!!

Now I gotta know what mag and who wrote this article. I have mostly stopped reading gun rags anymore, because of the tripe that the writers were spouting.

If i had to make a SWAG on the author I'd have to say that it sounds alot like Charlie Cutshaw... the uber accessorizor.

[Josh-L]

Necro bump.

I am planning on building an 8.5 inch upper. This is just a range "toy" but I'm still interested in "ballistics". Everyone always says how poor ballistics with 7.5 barrels are but I've never actually seen any data or gel testing or whatever. In my search I found this thread...

http://www.silencertalk.com/forum/vi...ornady#p469368

... now I don't know how scientific milk jugs are but that's the closest thing to any actually testing I've ever seen.

I got issued a M4 at work so I no longer have to carry my personal AR which is why I'm building this VSBR but I am still interested in finding a possible good defensive load for it just in case ya know. I have a buddy that goes coyote hunting a lot and I'd like to take one out with my VSBR.

So I bumped this thread to see if Doc, or anyone else, has any updated ammo recommendations or can link to any test data where a VSBR platform has been tested.

[RyanB]

If you receive proper professional training, you will find there is little to no "maneuverability" issue with an M4 of normal length.

There is little reason for a 7.5 inch barrel in an AR.

Once the gun is out of the backpack you smuggled it into the third world in...