Parts For a 3-Gun Upper?


Chris Rhines
September 11, 2004, 09:05 PM
I'm looking at puting together a 20" AR-15 soley for Limited/Tactical class multi-gun competition. To save a bit of cash, I'm just going to build the upper assembly and plop it on one of my Armalite lowers.

So, I'm a lookin' for some parts.

For the barrel, I want a light barrel, 20", with a fast twist. I'd prefer a chrome bore and chamber - the ease of cleaning makes the slight loss of accuracy worthwile, at least for me. Any suggestions for brand/where to buy?

I'm also looking at a PRI GenIII float tube, mainly for the light weight. Who has the best prices on the PRI tubes?


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September 11, 2004, 09:22 PM
You have a conundrum here.

You want:

20" A1 or A2 profile bbl
1/7 or 1/8 twist (are you willing to compromise to 1/9?)

A Colt SP1 upper, for example, would fit the bill perfectly...except the twist is way too slow for the neat new bullets coming out of Black Hills, and you'd have to replace the upper receiver to get a flattop for optics.

A Bushy 20" A2 barrel, would also suffice...except that Bushy only puts out very limited quantities of 1/7 IIRC - perhaps e-mailing them would clear things up?

Companies like LMT and CMMG offer 20" uppers, but from what I can tell, most are HBARs, or at least saddled down with all the heavy rail systems people seem to like these days. I'm not very familiar with LMT and CMMG, and they may offer exactly what you are looking for, so I'll let a more enlightened AR-15 guru take over from here...;)

Chris Rhines
September 11, 2004, 09:34 PM
Hmmmm... If I had to compromise on something, it would be the twist rate. I could settle for a 1-9" twist.

Something else I just wondered about. Would a 20" fluted HBAR barrel be lighter or heavier than a 20" A2 barrel? Choices upon choices upon choices...

- Chris

Zak Smith
September 11, 2004, 10:34 PM
Hbar is almost too heavy for 3Gun. There's no reason to go that heavy.

Things that are mandatory, IMO:

. Rifle-length GAS SYSTEM. The mid and carbine length gas systems upset the gun much more.
. no worse than 1.75 MOA accuracy. This still allows hit on steel at 330 yards.
. A good muzzle comp. JP BC, Benny Hill, Miculek, MSTN QC comp are all good modern designs.

I suggest getting a 1:8" twist. It will allow you to shoot the 75-77gr bullets if you ever want to.

MSTN sells a "competition" version of the PRI GenIII tube which is lighter than the "tactical" version.

Chris Rhines
September 11, 2004, 10:55 PM
Yeah, what I was wondering is if a fluted HBAR barrel would save more weight than a standard A2-profile. Looking at a couple of barrels, I think the answer is no.

The rifle-length gas system is the reason that I'm building this rifle - my current multigun AR is a 16" carbine that is a pain to shoot rapidly.

I've already got a JP muzzle break coming. I love them.

I would get a 1:8" twist barrel if I could find a chrome-lined one. As far as I can tell, no one makes chrome-lined 1:8"-twist barrels. The 1:7" Colt may have to do...we'll see.

- Chris

Zak Smith
September 11, 2004, 11:00 PM
You don't really need chrome-lining in a 3Gun barrel. Really, it's not a big deal. Go stainless and replace the barrel in 15,000 rounds.

Cleaning? We're supposed to clean these things? :uhoh:


September 11, 2004, 11:14 PM
Go stainless and replace the barrel in 15,000 rounds.

I notice how Zak is steering you towards his rifle. :) ;)

Zak Smith
September 11, 2004, 11:20 PM
Well, it might sound that way, I suppose.

Chris Rhines
September 12, 2004, 10:40 PM
Heh. Not that I would mind - I've seen Zak's rifle.

In fact, if I were smart, I would probably just send a large check to JP and get one of their CTR uppers. But I just can't help myself... :D

- Chris

Bartholomew Roberts
September 12, 2004, 10:47 PM
Bushmaster sells an A2 profile, 20" 1/7 barrel on their website. Pre-ban (soon to be no-ban) only.

Zak Smith
September 12, 2004, 11:34 PM
I've never met someone who regretted buying a JP upper or rifle. Anyway, back on topic..

More mass in the rifle helps on long-range stages were your heart is pounding and you're breathing hard (e.g. stages 1 & 4 at RM3G this year, and at the ITRC). However, I don't like Hbar. JP's Mid-weight 20" barrel is as heavy as I'd want to go. It is actually quite thin under the handguards (not quite Govt/A2 thin, but close), but then it's bull from the gas block to the muzzle. They experimented and found that this was more accurate, and you get rid of all that extra mass under the handguards.

My next 3Gun/tactical upper will be a lightweight 17" (1:8") stainless with a rifle-length gas system and PRI GenIII tube. 17" is as short as you can go and use the rifle-length gas system.


September 13, 2004, 11:21 AM
"my current multigun AR is a 16" carbine that is a pain to shoot rapidly."

Just curious - what is it about the shorter gas system that makes them a pain to shoot rapidly? Do they malfunction, cycle slower, or what?

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