I got my first Form 1'd lower receiver approved at the beginning of February and quickly set about putting my first short barreled rifle together.
The result:
"We're here for the bank's money, not your money!"
I've always been enthralled by the bank heist shootout scene in Heat, and I really like Retro ARs, so an RO733 "Commando" clone was a no-brainer.
The lower:
- Stag lower receiver
-Colt receiver extension/castle nut/end plate.
-BCM H buffer and recoil spring
-Milspec FCG
-A2 grip (I used to hate these, but I've been shooting so much with guns with A2s on them lately they don't bother me so much now)
-M&A Parts CAR stock.
The Upper:
* * - Windham C7 upper with M4 feed ramps.
So regarding the receiver, originally this gun was built with a Fulton C7 upper w/ ramps but I was having intermittent failures to feed. A receiver swap seems to have alleviated the issue, although I think the culprit was actually the barrel extension, not the upper receiver itself. The Windham's ramps are just shallower and thus change the geometry enough so the barrel extension isn't snagging the noses of incoming rounds.
One interesting aside is that while late production "700 series" carbines could be found with true "M4 feedramps", earlier production 700s often had what were termed "extended carbine" feedramps, which were similar but shallower and shorter than M4 ramps. The ramps in the Windham upper are noticeably less pronounced than other sets of M4 ramps I've seen, thus making them perhaps more "correct" for a 700 series clone. Although I'm kinda assuming this was an accident and not something Windham did on purpose, because to assume the latter is probably giving then too much credit...but hey, it works.
On to the rest of the parts...
* * -Spike's 11.5" CHF/CL pencil barrel. I'm kinda "meh" on Spike's in general but 1/7 11.5" pencil barrels aren't too common nowadays so I had to take what I could get.
- Non-F FSB pinned on by John Thomas at Retro Arms Works. He also removed the bayonet lug and reparked the area where the lug was. 733s came both with and without intact bayonet lugs, but the guns used in Heat were of the lugless persuasion, so I went that route.
* * -A2 flash hider and peel washer (I hate peel washers..)
* * -BCM gas tube
* * -BCM Delta Ring etc..
* * -Son's of Liberty Gun Works BCG
* * -Colt charging handle.
* * -Unknown make of 6-hole CAR handguards.
Gun weighs about 5 1/2 pounds. Basically it's modeled after the "later" 733s, which could have A2 lowers, Fiberlite stocks and round forward assists. 733s were pretty variable in terms of the parts used to assemble them during the course of the years they were produced. Apparently some of the latest production 733s actually used A2 uppers and "government profile" 11.5" barrels.
So while overall I'm happy with my Commando clone it should be pointed out it's not 100% correct. The receiver extension is a 4-position (I tend to shoot one position in from fully extended with carbine stocks for some reason), and it has a castle nut instead of the old CAR lock ring on it. The lower was assembled years ago, and rather than pulling it apart to put the old lock ring on it, I decided to just roll with it the way that it was.
Most notably, the gun is black, rather than the iconic Colt Grey.
And I deliberately used an A2 aperture instead of the A1 style just to give myself the option of the larger aperture at close range.
Eventually I'm going to Form 1 another lower, but in the meantime I decided to put together a 10.3" upper with a more "modern" configuration together too, and use it on the SBR lower as well, which to my understanding, requires no notification to the ATF provided it isn't a permanent change and I retain possession of the 11.5" upper, which I obviously intend to do.
So the lower is the same as above, and as far as the upper half:
* * - Upper receiver is an Aero.
* * - Colt 10.3 "CQB" barrel
* * - Three-prong flash hider.
* * - LMT rear sight
* * - Dark Hour Defense melonite gas tube.
* * - BCM Delta Ring
* * - Colt snap ring/weld spring.
* * - AIM 7075 charging handle (will eventually go back to pulling "backup parts" duty and get replaced on this upper with a BCM Gunfighter CH or something.
* * -Toolcraft Bolt Carrier (also will eventually go back to the backup parts bin and get replaced by a SOLGW, BCM or similar)
* * - SOLGW Bolt, firing pin and cam pin.
* * - BCM PKMR handguards and BCM VFG.
* * - Aimpoint PRO.
I have a couple hundred rounds through the 733 upper and, yesterday being the first day out at the range with the 10.3, 103 rounds through that one. XM193 and Wolf Gold.
One interesting thing with the 10.3" is that at 100yds during my initial sight in, the gun required zero windage adjustment, which is like the first time that ever happened to me. I centered the rear aperture before shooting and was surprised when I didn't have to move it at all in order to make hits on Shoot-n-C 6" bullseyes at 100 yards. I only needed to make a couple minor elevation adjustments on the front sight. Eventually I'll probably do a 50yd zero for it instead of 100 yds though.
I realize ejection pattern is symptomatic but not necessarily diagnostic of gassing, but based on ejection, the 10.3 seems almost perfectly gassed, and the 11.5" seems maybe slightly overgassed. I don't know what the port size in the 11.5" barrel is because Spike's considers that info proprietary for some reason.
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Originally Posted by 1168
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