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9/22/2017 12:11:25 AM
Posted: 7/7/2003 8:36:59 AM EDT
After much thought, I finally decided to go with a Colt #6721 complete upper on my Colt #6520 lower, as I wanted the heavier barrel & flat top profile. I originally couldn't decide between a standard 16" M4 bbl, or a 16" HBAR profile. As the weapon will be used for a good deal of rapid semi-auto fire, I opted for the HBAR, if only for it's better heat dissipation qualities, as opposed to the lighter M4 style. Now that I've had a chance to put a number or rounds through it, I've learned that yes, it does heat up less than the standard M4 type, but is it ever HEAVY !! My question is, approximately how much weight difference is there between my Colt 16" HBAR (#6721) and the new SOCOM issue, heavy profile M4A1 barrels ? My AR6721 weighs about a pound more than a Colt LE6920, which is the same weapon, only with a standard weight 16" M4 barrel. Would it be worth the effort to perhaps have a RRA 16" SOCOM M4 heavy barrel installed on my Colt 6721, or would the weight difference be too little to notice ? ANY replies, comments or data will be deeply appreciated. THANKS. Regards, Dom Pastore
Link Posted: 7/7/2003 9:16:53 AM EDT
[Last Edit: 7/7/2003 9:18:20 AM EDT by Green0]
How do they compare? (you can mount a 203 on the not really new SOCOM barrel) You can't on a 16inch HBAR. The SOCOM barrel has a flaw (it still has the stepdown area and can still bulge there). The 16In HBAR is a more durable barrel (If you get a 16in fluted HBAR it won't be so heavy.) [b]I wonder when someone will actually produce a SOCOM style heavy M4 barrel? It seems to have some demand[/b]
Link Posted: 7/7/2003 9:48:55 AM EDT
The Colt HBAR is .75" most of it's length, right? IIRC, the M4 "HBAR" is only supposed to be .25 lb heavier than the M4 profile. I'm no structural engineer, but I don't like those sharp corners on the notch. :(
Link Posted: 7/7/2003 12:33:48 PM EDT
M4 and M4A1-heavy barrel. Picture by [b]KevinB[/b] [img]photos.ar15.com/WS_Content/ImageGallery/IG_LoadImage.asp?iImageUnq=3088[/img]
Link Posted: 7/7/2003 4:13:21 PM EDT
I just droped my BM 16" HBar off at the local gun smith to have it lightened to .75" the whole way. Shit I should have weighed if first.
Link Posted: 7/7/2003 5:02:59 PM EDT
We might ALL be blessed by the demise of the wretched step-down M4 barrel when Crane selects the new SOPMOD handguard system. Existing M203's might be retrofitted to rail mount, thus allowing the program to focus on the best performing barrel contour instead of forcing the contour to fit an outdated attachment system.
Link Posted: 7/7/2003 5:08:37 PM EDT
But M4s look so Cool NOT
Link Posted: 7/7/2003 5:27:59 PM EDT
Tag so I can check later. -REAPER2502
Link Posted: 7/12/2003 3:53:39 PM EDT
Wasn't the US Military mounting a 40MM grenade launcher on CAR-15s, the foprerunner of the M-4 series a while back? I seem to recall that the CAR-15 BBls were NOT stepped down. Any one know the reason behind this? Or even if I am correct on this ??? [>:/]
Link Posted: 7/12/2003 4:59:47 PM EDT
The CAR barrels are the same diamiter as the steped portion of the M4 Barrels. The step is to get the barrel back down the the orriginal diamiter so the old mounts will work.
Link Posted: 7/25/2003 8:25:47 AM EDT
Is that 0.750" under the handguard? It looks more like the 0.850" that the SPR has under the handguards. Does anyone know that the exact dimensions are? Thanks, IDHunt
Link Posted: 7/25/2003 11:05:31 AM EDT
Link Posted: 7/25/2003 11:19:28 AM EDT
What I'm wondering (about the heavy M4 bbl), is do the cuts under the handguards pose any structural problems there? Any bending or bulging there?
Link Posted: 7/25/2003 2:35:06 PM EDT
Link Posted: 7/25/2003 2:55:47 PM EDT
I have not noticed any issues with the 921 top end. The barrel is still .850 thick top to bottom in the flat areas. Mine is the most accurate (go figure) 14.5" barrel I have. The pencil C8 barrel is nicer to hump but the 921 bbl is nicer (IMHO) to use. I should shortly (Aug/Sept) be able to have some heating graphs available... Up to and including 16" Midlength graphs too.
Link Posted: 7/26/2003 10:25:44 AM EDT
Thank you guys for the measurements. It looked like 0.850". I think the 0.850" makes a good compromise between the 0.980"-1.00" under the handguard of the NM barrels and the 0.640" of the M4 barrels. I wonder if any research has been done into coatings with high thermal conductivity. Something that would not only protect and camo the metal, but increase heat dissipation. I think one of the selling points for Norrell's Moly Resin is the good thermal conductivity, but I know there is better stuff out there that is used in race engines etc. IDHunt
Link Posted: 7/27/2003 1:36:52 PM EDT
KevinB said The pencil C8 barrel is nicer to hump but the 921 bbl is nicer (IMHO) to use.
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What does a C8 barrel look like? Have seen some pics on the Diemaco website but they aren't clear enough to tell what the barrel looks like.
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