View Full Version : A1? Upper to Flattop
I recently bought a Bushmaster M4 16" CARBINE. It has a fixed carry handle. After shooting both it and my BCM 20" upper I have decided the fixed carry handle sucks. Too hard to mount a red dot. I had a BSA red dot laying around and put it on just to check it out and got a pretty much perfect co-witness. I used an NCStar drop down carry handle rail to mount it. Only problem is there is no way to get the rear aperture out of the way.
I figure I have two options; get rid of the BM upper and get another upper or swap out the upper receiver.
If I do a swap, what is a decent bare upper and how much can I expect to pay?
If I get a new upper, it will probably be a BCM since they give out cool caps:D.
I took both to the range yesterday, put 90 rounds downrange to get things sighted in and liked them both. Different reasons. The carbine sure handles nice, but the rifle feels better.
I'll keep a carbine upper for when the zombies come.
I guess I need to get another lower too. AR fever?
Try BCM, as you already seem to know about them. See this link (assuming your bushy has M4 feedramps, BCM also has non M4 uppers)
http://www.bravocompanyusa.com/Upper-Receiver-assembly-M4-Flat-Top-p/flat%20top%20-upper%20-m4%202.htm
BTW - Short of a retro nostalgia build, I have no idea why anyone would buy a fixed handle A1 or A2 receiver. I don't even like carry handles, much less ones you can't remove.
Try BCM, as you already seem to know about them. See this link (assuming your bushy has M4 feedramps, BCM also has non M4 uppers)
http://www.bravocompanyusa.com/Upper-Receiver-assembly-M4-Flat-Top-p/flat%20top%20-upper%20-m4%202.htm
BTW - Short of a retro nostalgia build, I have no idea why anyone would buy a fixed handle A1 or A2 receiver. I don't even like carry handles, much less ones you can't remove.
I bought it from an individual, unfired, no paper trail for the Brady Bunch to track me. Also I had no experience with flat tops. I hadn't fired an M16 since I retired from the Air Force in 1987 (they had A1s for "qualification".) Air Force qualification was a joke back then; I don't know about now. I always shot better than most of the Security Police in the same class, and I don't consider myself a good shot, just middlin'.
Checked out your link; didn't know it would be that cheap from BCM.
OK now, what do I need for tools? Will the normal "armorer's wrench" do the barrel? I can rent a big torque wrench for the barrel, I can already cover everything up to 750LbIn. I figure I can make a hardwood fixture to hold the receiver in a vise. I think I have the needed regular punches, but need to think about roll pin starters and punches. I have the Midway "Gunsmithing the AR-15" DVD and they want to sell me specialized tools for everything. This may well be the only upper I ever build, but who knows. My youngest son (he just got an AK-47) loves the gun. My older son hasn't seen it yet.
What's the best place to get stripped lowers anyway? I saw something the other day about 3 at about $75 each. If I get the tools, I might as well build some for the kids.:p Maybe I can dump the A1 on one of them?:rolleyes: Nah; they're family.
SEE HOW YOU PEOPLE ARE! Now I've caught the bug.:D
Now you know about A1 and A2 receivers, at least.
The cheapest quality lowers I have seen are made by Aero Precision. They can be had with either a roll-mark from Aero Precision or "SURPLUS AMMO & ARMS" from, naturally SurplusAmmo.com. These are probably the ones you saw referenced, and can be bought for $75ea if you buy 2-5. I have never owned one myself, but have seen one and heard lots of good reviews. Personally, I have been buying Daniels Defense lowers from Grant at G & R Tactical, one of our sponsors. They run $126 ea, and have a very nice flared magwell, in addition to be a well finished, high quality piece. Grant's website lets you add stuff, like a variety of LPKs (Grant assembles a very good one from several manufacturer's parts), receiver extensions, buffers, stocks and grips, all at competitive prices. Then, as a bonus, the lower comes assembled with your chosen parts. (of course if you were looking forward to building it yourself, that's not a plus.) I have two of these. One is topped with an AR Performance 18" SS 6.8SPC upper for hunting, and the other has a BCM 16" Lightweight middie upper. Both guns work superbly, although oddly enough, prior to the ARP upper, I had a Stag 5 6.8 upper on it that didn't want to feed worth a darn, but now works on a S&W MP15 lower I bought locally.
See how bad BRD can be!!
Either way, G & R is a good parts source, and on some parts, you can get an M4Carbine.net discount.
Now you know about A1 and A2 receivers, at least.
The cheapest quality lowers I have seen are made by Aero Precision. They can be had with either a roll-mark from Aero Precision or "SURPLUS AMMO & ARMS" from, naturally SurplusAmmo.com. These are probably the ones you saw referenced, and can be bought for $75ea if you buy 2-5. I have never owned one myself, but have seen one and heard lots of good reviews. Personally, I have been buying Daniels Defense lowers from Grant at G & R Tactical, one of our sponsors. They run $126 ea, and have a very nice flared magwell, in addition to be a well finished, high quality piece. Grant's website lets you add stuff, like a variety of LPKs (Grant assembles a very good one from several manufacturer's parts), receiver extensions, buffers, stocks and grips, all at competitive prices. Then, as a bonus, the lower comes assembled with your chosen parts. (of course if you were looking forward to building it yourself, that's not a plus.) I have two of these. One is topped with an AR Performance 18" SS 6.8SPC upper for hunting, and the other has a BCM 16" Lightweight middie upper. Both guns work superbly, although oddly enough, prior to the ARP upper, I had a Stag 5 6.8 upper on it that didn't want to feed worth a darn, but now works on a S&W MP15 lower I bought locally.
See how bad BRD can be!!
Either way, G & R is a good parts source, and on some parts, you can get an M4Carbine.net discount.
Aero Precision (with the Surplus Ammo mark) looks good. Maybe I'll pick up a couple payday. I like the multi-caliber marking. I'm thinking of a 6.5 Grendel or (less likely)6.8 spc.
The 6.5 has some great BC bullets and I have a 6.5-06. Need a 1 in 8 or 9 barrel though; probably 1 in 8 for the 6.5 grendel.
I think I'd put it on a .308 lower though lower though so I could seat the bullets out where they belong. Hmm. Maybe a 260 Remington?
Comments?
I still need to know what tools I really need to build a lower. An upper.
I don't know what I would without M16Carbine.net. Yes I do; I'd forget the whole thing.:o:
Of course, then I wouldn't have gotten hooked.:happy:
Here's a little info on a 20" Colt A1 upper that I "converted" to a flat-top.
Competing With the Past
More than thirty years ago, the article “AR-15 Match Loads” by Al Miller was published in Handloader magazine. As you would expect, the article chronicles Al Miller’s endeavors in developing accurate loads for the AR-15. The AR-15 he used in developing his match loads was an A1 version. (Did I mention this was done 30 years ago?)
http://www.box.net/shared/static/8cjkp7clex.jpg
Even though the M16A2 replaced the M16A1 as “Standard A” for the U.S. Military in November of 1983, the A1 has several characteristics that many people still find desirable today. Foremost would probably be the light weight of the rifle, which is due in no small part to the A1 barrel. The A1 barrel weighs several ounces less than an A2 government profile barrel (and one pound, 4 ounces less than an HBAR). Comparing the profile of an A1 barrel to an A2 barrel, we see that the weight reduction occurs in the area from the gas block to the muzzle.
http://www.box.net/shared/static/ody9g3zc41.jpg
Another feature of the A1 model that many people like is the simplicity of the rear sight. It is a “set it and forget it” affair with adjustment for windage only.
http://www.box.net/shared/static/6sh36nk97o.jpg
A third feature of the A1 model often mentioned is the shorter length of pull when compared to the A2 model. The A1 stock is 5/8” shorter than the A2 stock. [While the A2 stock is longer than the A1 stock, it is made of improved materials making it 10 to 12 times stronger than the A1 stock. (All the better to butt-stroke you with, my dear!)]
I had an unfired, 20” Colt A1 barrel assembly in excellent condition that I’ had been saving to use for a 20” KISS type build along with original Colt triangle handguards, and Colt A1 receiver. As Colt introduced the first AR-15 A2 model to the civilian market around 1984 and stopped producing the A1 Sporter model around 1985, I’m going to take a S.W.A.G. and say that the A1 barrel that I had was over 20 years old! The barrel was stamped “C MP CHROME BORE” and had a 1:12” twist.
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While I wanted to keep this KISS build as reasonably light as possible, I did want to make a few changes from the standard A1 configuration. One complaint generally heard against the A1 barrel is that it is “not very accurate,” though most often the complaint is made without any quantifying data being presented. Also, the A1 model uses the triangle handguards that are known for having poor heat dissipation and easy breakage. I decided to replace the triangle handguards with a 1st generation JP Enterprises free float tube to aide in heat dissipation and in ringing out all the available accuracy of the A1 barrel. The JP tube and barrel nut replace the triangle handgurads, handguard endcap, barrel nut and delta ring assembly. The JP free float tube and barrel nut actually weigh 1 ounce less than the original parts that they replace.
http://www.box.net/shared/static/pzvyv8pa5z.jpg
While I like the simplicity of the windage-only feature of the A1 sight, I prefer the sight aperture of the A2 sight. The “long distance” aperture of the A2 sight is about 0.010” smaller than the A1 aperture and the A2 aperture also has the “ghost ring” aperture for up close/low light shooting that is lacking on the A1 sight. Enter, the LaRue Tactical Back Up Iron Sight. This sight uses an A2 aperture but has adjustments for windage only; exactly what I was looking for. The sight attaches to the Picatinny rail of a flat-top upper receiver using LaRue’s throw lever mount.
http://www.box.net/shared/static/y31ou12k0j.jpg
You’ll notice in the last sentence that I said flat-top upper receiver. An A1 upper receiver weighs 9.9 ounces. An A4 flat-top upper receiver with the LaRue BUIS attached weighs 11.5 ounces for a difference of 1.6 ounces. Using the JP free-float tube along with the flat-top upper receiver and LaRue BUIS for this build gives me a net weight gain of only 0.6 ounces more than a standard A1 upper group. It also gives me the option of adding optics to the flat-top upper receiver and rails in just about any position I might need them on the JP free-float tube. Even though the LaRue sight is referred to as a back-up sight, I’ll be using it as the main sight on this KISS build.
The completed 20” KISS build weighs in at 6 lbs 15 oz. Here are a few pics of the the build.
http://www.box.net/shared/static/a5sc4oly28.jpg
http://www.box.net/shared/static/9dlmlilonx.jpg
http://www.box.net/shared/static/omd90lyxak.jpg
http://www.box.net/shared/static/9d69bpthe9.jpg
For his article “AR-15 Match Loads”, Al Miller used six different powders and five different bullets in testing, including Sierra’s 52 grain boat-tail hollow point bullet. He tested his loads off a bench at 100 yards using front and rear bags and a scope. His groups ranged from 0.75” to 2.75”. Unfortunately, he did not fire any 10-shot groups (I guess he didn’t get the memo. ) All of his groups consisted of 5 shots each.
Using his best tuned load, Al Miller turned in ten, 5-shot groups that had an average extreme spread of 1.075”. While these were only 5-shot groups, I was extremely impressed that he was able to obtain that level of accuracy using an A1 barrel. I was curious to see how my twenty year old A1 barrel would stack-up against his. (Obiously, I had an advantage with the free-float tube.)
Using one of my standard handloads for Sierra’s 52 grain MatchKing, I fired ten, 5-shot groups in a row from the bench at 100 yards (using front and rear bags and a scope) with the following results:
0.81”
1.10”
1.04”
1.34”
0.66”
0.73”
1.01”
0.98”
0.93”
1.08”
The average extreme spread for my ten groups was 0.968”. Following my standard protocol for accuracy testing, I also obtained three 10-shot groups from 100 yards that measured:
1.39”
1.26”
1.40”
Those three, 10-shot groups had an average extreme spread of 1.35” and more importantly the three groups overlayed on each other using RSI Shooting Lab had a mean radius of 0.45”. Here are some pics of the best groups.
http://www.box.net/shared/static/t2oyzpktgr.jpg
http://www.box.net/shared/static/6y20jdos12.jpg
http://www.box.net/shared/static/kgcgn3ubx9.jpg
In 1964, during testing for report number DPS-1471, the US Military conducted accuracy testing of production M16 rifles (which had the same barrel as the M16A1.) With the rifles secured in a machine rest, three 10-shot groups were fired (hmm . . . where have I heard that before) from 100 yards using M193 ammunition. “The average extreme spread of the groups ranged from 2.6 to 3.6 inches.”
For nostalgia sake, I fired three, 10-shot groups of IMI M193 off the bench at 100 yards from my A1 barreled upper. The average extreme spread of the three groups was 3.00”.
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