20” barrel versus 16” barrel ..?

[Buncheong]

Since you already have several 20" ARs, see if you can try out someone's 16" upper/carbine. Use the same ammo at the same distances, same sights/optics if possible, and same weather conditions and judge for yourself. It would probably make for an informative day of shooting.

Great recommendation - recently, I did just that.

Used 55 gr M193 and 62 gr M855 ammo for both, and I couldn’t tell much difference in accuracy between the two. 16” was slightly louder maybe, slightly more recoil and flash. Full disclosure though, we were using steel targets we’d set up at roughly 200 and 400 yards - groups may have varied widely, no way to tell that day.

But afterwards I got to thinking, “maybe 20 inch rifles are more of a luxury than a beneficial necessity,” and so ... I posted here to ask the pros...

[Buncheong]

You don't have to give up sight radius on a 16".

Here's a look at my 'Dissipator', 16", carbine gas system.

Great photos - thanks for the visual, it’s of great help!

[Humpy70]

A lot depends on your age.

When the M14 was THE Service Rifle (along with M1) in highpower competition you had the top shooters in their 40s winning. When the ARs came in the top shooters are under 30 because their eyes are young and can accommodate better so their shooting careers are much shorter. You won't find many guys with any miles on them shooting the AR because of a simple rule, "You can't hit what you can't see." haha

That is the reason the CMP now allows optics in Service Rifle which gets the "high mileage" shooters back in the game.

Some guys could not see sights on 26" barrels and Bloop Tubes were the fad which put the front sight 8 to 10 inches in front of the muzzle which really helped. Then the rule was changed to allow a front sight with magnification and that really helped.

The Army Wound Ballistics Lab determined the 55 and 62 grain ammo both lost terminal ballistic capability at 95 yards with 20" barrels and I don't think the WBL was still up and running when the 16" barrels got popular as Fackler (the commander) retired and there was no one to replace him. I suspect the capability has been deteriorated down to about 88 yards.

The flash signature got less with the M16A2 solid bottom design and I have not seen flash signature photos of a M4 but I can tell you for sure if you get a M4 with no flash cage at the muzzle and you shoot it at night the guys in the space shuttles are going to know where you are. I have a 16" Rem 7615 pump gun and the flash signature is about the size of a 2 gal barrel in DAYLIGHT ! ! ! !

That is one of the negatives on ball propellants is the flash signature.

I have one 16" barrel and several 20 and one 24" varmint from RRA I have had for years but never got around to shooting it.

A SHTF rifle I am building has 18" barrel and a M16 flash suppressor (2nd variation) on it opened up to accommodate a 30 cal bullet passing through. For sights it has a pistol scope mounted on barrel forward of the receiver so the clip slot can be used.

THe action is a 1903A3.

[1168]

Using data available here:
http://www.sadefensejournal.com/wp/b...-nato-weapons/
And here:
https://rifleshooter.com/2015/12/223...s-to-6-inches/
A 16” barrel has 93-96% of the velocity in a 20” barrel. While 20” barrels are awesome, most commercially available ammo is going to do just fine in a 16”. There are many reliable 16” options on the market. Bolt life is unlikely to be a realistic problem. Muzzle flash with an A2 is negligible. For sight radius, get a mid-length or a mock dissy, like pictured above. If you go with a free float, a 13” URX4 puts a Troy fixed front sight in almost the same position as a M16, and a 14.5” URX4 has a longer sight radius.

If you want retro-cool and near maximum ballistic efficiency, go with a 20”. If you want a light, handy carbine that has more than enough ballistic prowess, go with the 16”. There’s zen in a 16” barrel.

Montana Marine, who did that mock dissy barrel for you?

[markm]

You don't have to give up sight radius on a 16".

Here's a look at my 'Dissipator', 16", carbine gas system.

Exactly. I bring out and shoot this dissy more than any other AR.

[jsbhike]

PSA does a midlength dissipator or 2:

https://palmettostatearmory.com/psa-...165449779.html

I though BCM did, but may be making a mental leap of their Kino 12.5" carbine.

[MontanaMarine]

This link should show PSA's dissipator uppers.

https://palmettostatearmory.com/cata.../?q=dissipator

I assembled my own because I wanted an A2 upper, and had the barrel looking neglected in the spare parts box.

[MontanaMarine]

Exactly. I bring out and shoot this dissy more than any other AR.

Very nice.

[1168]

PSA does a midlength dissipator or 2:

https://palmettostatearmory.com/psa-...165449779.html

I though BCM did, but may be making a mental leap of their Kino 12.5" carbine.

This link should show PSA's dissipator uppers.

https://palmettostatearmory.com/cata.../?q=dissipator

I assembled my own because I wanted an A2 upper, and had the barrel looking neglected in the spare parts box.

Thanks, guys. I actually have a PSA mock dissy upper, but I’m always keeping my eyes open for others because it doesn’t have a true 5.56 chamber and has a strange barrel shoulder that makes me a little scared to put a can on it. Its a ton of fun to shoot, though.

[vicious_cb]

I'd generally avoid barrel lengths greater than 16" for anything other than dedicated precision builds. Modern optics negate the need for sight radius and as posted above the velocity gain is negligible, Esp when modern defensive loads are put into the mix.