I’m trying to build my first AR15 with a mid-length 16" barrel as a range toy (unsuppressed). Anticipated firing position is 60% standing and 40% prone or from a bench. Favoring a lighter, but not quite pencil, weight I’ve narrowed it down to one of the following three contour barrels:
I’m sure I’d be happy with any one of these but the ADM flavor shaves off 3 oz and roughly $40 from the other two. All of the mid-weight barrels I’ve taken into consideration call for a 0.625" gas block except the ADM, which seems odd. Is there any advantage to having a larger gas block?
.750 vs .650 does not refer to the gas port, rather it is the diameter of the journal the gas block fits around. .750 is a common standard, and .650 is commonly found on lighter barrels. Either is fine, provided the gas block is attached appropriately.
I think you’re agreeing with me it’s odd. Care to expand why it’s more appropriate? Is it because the barrel has more weight where you don’t want it? This could very well explain the slight discount.
OP probably shouldn’t be building a carbine with this little of a knowledge base. Maybe buying a complete gun or a upper/lower combo is a safer bet. You can build the next one…
I don’t really agree asking why a lightweight contour barrel has a larger than typical diameter at the gas block disqualifies me from being capable of choosing components for or assembling a rifle. I’ve completely disassembled and reassembled (and I’m not talking field stripping) numerous pistols, a PCC (MPX), a shotgun, and built a bolt gun. Despite my experience with other platforms there are so many great suppliers, videos, and forums out there the population of folks that should buy, rather than build, their first AR15 is a very small one.
I started this journey thinking I’d get a Daniel Defense, which I agree would be safer but it’s far more fun to roll my own and a heck of a lot cheaper.
Not all that long ago, there was a wider selection of .750 gas blocks and most pencil barrels had a .750 journal. The ADM barrel profile is simply a holdover from that time. It’s not a bad thing, it just offers no advantage and weighs slightly more than a .625.
Your question didn’t leave me with the impression that your knowledge of firearms or the platform was all that high. My impression may well be wrong, but my recommendation stands. My take is that unless you have some kind of frame of reference to know what you want or need, you’re probably better served with a factory gun and you’ll have more money for ammo and training to gather that frame of reference.
Shheeeiiiit, there was a time that I thought that I wanted to put a RIS II on my 6720. Sometimes you don’t know what you don’t know.
Well, you have obviously never “rolled your own” before because it never works out that way, unless you’re talking about getting a PSA kit, in which case, carry on.
I’ve assembled numerous ARs, but during the last few years, I’m finding many options for factory uppers and lowers that make assembling them myself illogical.
One example is the LE6920 lower and 6960-CCU from Brownells. The complete Carbine will be $865 (less irons) with a Colt BCG from Arms Unlimited.
Puchasing a completed rifle from a LGS adds significant sales tax and I’d have to incur additional expenses to convert it to comply with state laws (I don’t live in a free state) given how I plan to use it.
My pencil barrel sports a .625 gas block. Just makes sense to keep a consistent profile and save the weight, unless you just have a specific .750 block you want to run. When I bought my pre-assembled BCM upper they were one of the few options running a .625 block. As previously mentioned above, back in the old days .625 blocks weren’t common so that pencil profile with more meat under the gas block was pretty common, but not today.
