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1/25/2018 7:38:29 AM
Posted: 11/21/2003 10:30:40 PM EST
[Last Edit: 11/21/2003 10:35:15 PM EST by billclo]
I have a AR that I was considering having Kurt's Kustom guns turn down for me.

It is a Bushmaster Postban 20" 1/9 HBAR, with fluting. I noticed that BM is now offering the A2 Govt profile on Post ban barrels (something they were not when I got the 20" HBAR + Fluting).

I see that Kurt's will turn down and repark to an A2 profile or A1. I have approximate weights from Bushmaster's site that say that a 20" HBAR fluted weighs approx 3.0 lbs, and a 20" A2 Govt weights approx 2.5 lbs. I have been unable to find figures on the Net for the weight of an A1 profile barrel.

On the one hand, I suspect that the A1 profile would be lighter than the A2, which would be nice, but...on the other hand, will it heat up too quickly? I won't be doing full auto fire, but I don't want a barrel that would heat up too quickly in a hypothetical firefight either.

I find that my other rifle, an 16" M4, heats up pretty fast (2 30-rd mags within a couple minutes of each other), so an comparison with how an A2 or A1 heats up would be useful.

I have this rifle setup with flattop and an Aimpoint CompML2, and frankly, it isn't as light as I'd like...

Anyone have experience with A1 barrels, and/or have weight figures?
Link Posted: 11/22/2003 4:17:50 AM EST
[url]groups.msn.com/TheMarylandAR15ShootersSite/techdata.msnw[/url] Listed weight for an A1 profile barrel < .600" entire length, 20" > is 2.2 pounds. Kurt has reprofiled a couple of HBAR's to A1 <14.5"> for me and while they do heat up quicker, they cool down quicker. Not exactly scientific I realize, but I've done Tweak's 120 round quick and dirty reliability test on all my AR's including the A1 profiles <120 rounds through the 'ol girls as fast as you can fire and change mags... 0 failures = good [;)] > {no failures from any of my Bushy's or ArmaLite's Tweak!!!} and the A1's are singing hot, but cool much quicker than the heavier profiled barrels. Heat is the enemy of barrel life, so I would figure that my A1's MAY not last as long as the heavier profiles, but to me that fact is outweighed by the ligher weight and easier handling... no free lunch, I'm afraid, but in a real world situation I'm going to reach for one of the A1 profiles over the heavier profiles...
Link Posted: 11/22/2003 5:23:15 AM EST
If you go with the A1 profile, you will end up with a 20" rifle that weighs slightly less than the M4's, plus you will have an extra 150fps over the 16 inchers. Heat shouldn't bee that big a problem, if the situation gets that bad, just shoot yours till it melts down, then pick up another from a gremlin you just dropped. I am shooting an A1 and even with sustained fire, enough to make the clp on the barrel smoke, the POI does not shift. It shoots to the same point hot or cold. That is most important to me.
Link Posted: 11/22/2003 6:44:10 AM EST
If you're like me, and shoot 55 grainers pretty exclusively, you might consider just picking up an A1 barrel, and selling off the Bushie barrel. There are scads of GI surp A1 barrels out there at the moment, so if you can live w/a 1 in 12 twist, picking one up, and selling off the HB job would save a bubch of bucks.
Link Posted: 11/22/2003 8:12:22 AM EST
[Last Edit: 11/22/2003 8:26:57 AM EST by billclo]
Thanks alot for the info, DarkStar. I saw the page where Forest had the weight of the entire gun, but missed the link to individual component weights. Cool. I guess an A1 profile would be alright - after all, the military used them til the early 80s, without the guns croaking prematurely...and yes, having an 20" barrel with the weight of an M4 barrel is very tempting. I just measured my barrel, using Forest's info, and mine measures .750 under the front sight assy, so I guess getting an A1 profile is out of the question. A2 will be a help though. Shamayin, While that is a good idea, I plan to be using 69-gr loads in this gun, probably one of Black Hill's loads. 300-400 yard work with a scope.
Link Posted: 11/22/2003 8:43:45 AM EST
Originally Posted By billclo:I just measured my barrel, using Forest's info, and mine measures .750 under the front sight assy, so I guess getting an A1 profile is out of the question. A2 will be a help though.
View Quote
You can still have the barrel turned down to A1 specs fore & aft of the front sight, it just won't be quite as light as a true A1 because there will be a short thick section under the front sight/gas block.
Link Posted: 11/22/2003 9:42:01 AM EST
Billco, I think you can make out the stepdown at the FSB in this pic. I had Kurt leave the area under the FSB heavy. Kurt can also remove the FSB and reprofile this area as well, leaving it heavy only were the FSB actually sits on the barrel... [img]img.villagephotos.com/p/2003-3/122167/KKFA3.jpg[/img]
Link Posted: 11/22/2003 11:32:13 AM EST
[Last Edit: 11/22/2003 11:33:35 AM EST by billclo]
That's good to know, and might be the best way to go. Yes, it does show up well in the picture. Thanks. Are there 2 different Front Sight Bases, one for A1 profile barrels, and another kind for A2? I wonder if it'd be cost effective to just have him remove the A2 and replace it with an A1, and just profile the whole barrel to A1...
Link Posted: 11/22/2003 1:08:53 PM EST
My A1 barrel walks so much when it comes back it brought Cokes with it.
Link Posted: 11/22/2003 4:32:48 PM EST
Originally Posted By DarkStar: {no failures from any of my Bushy's or ArmaLite's Tweak!!!}
View Quote
Glad to hear it DS, ya done good.
Link Posted: 11/23/2003 1:43:50 PM EST
You aren't going to melt down a A1 barrel any faster than an A2 in reality. I've fired M16A1's so fast the gas tube was glowing bright red. They still worked and shot good enough. The only difference in the actual barrel between the A1 and A2 is the thicker portion between the front sight and the muzzle. The A2 has the same profile under the handguards as the A1. You'll get some better heat transfer with the heavier-out-front barrel, but not enough to really make a hill of beans in real use. The big difference IMO is in balance. Handle an AR with an A1 barrel and one with an A2 barrel (make sure they have the same length buttstock) and you'll notice a difference in handling. Choose which you like better. Personally, I like the A2 Govt profile balance overall. I opt for that barrel at the cost of the half pound. I wouldn't bat an eye at an A1 profile either. In actual use, they work just fine. They are lighter as well, which is what the AR was originally all about. Some folks like the A1 balance better, and I can't fault their choice either. Just get a high quality barrel of the profile you like. You won't have to worry about too much heat, beleive me. I have a C7A1 clone, and it's the perfect rifle. I also use the A2 profile on my CAV arms lower, though cut-down to 18". That made it a bit lighter, but still kept it balanced nice (and it got rid of those evil threads). You might give that a thought. No expensive lathe work, just a cut-off and muzzle brake (I left mine bare to rethread if the AWB ends). Ross
Link Posted: 11/23/2003 9:04:50 PM EST
Originally Posted By Ross: You'll get some better heat transfer with the heavier-out-front barrel,
View Quote
That was the intention of the design, based on the results of USN heat trials using A1 and HBAR barrels and A1 and A2 handguards. Because of the excellent cooling effects of the A2 handguard the Navy report recommended that any metal added to the barrel be added to the area [b]not[/b] covered by the handguards.
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