I have owned a AR for less than 24 hours (S&W MP 15) and wanting to build another one. I can see this can be addicting.
My #1 concern is measuring headspace, and how important this is in building an AR.
Do you guys do this, or can you have it done. If you don’t is it unsafe.
Also where do you start, I see so many options out there.
Since the lower is the main part, I would think you would start with the best lower and build on to that.
What is one of the best lowers you can get, I know many are always out of stock.
I kind of think of the lower as just something that holds the fire control group and hooks onto the upper. I.O.W. the lower doesn’t seem that critical. What does seem important is the barrel, the carrier, and the bolt. So, the upper is where I start thinking. If you put an LMT upper on an Olympic lower, you’ve still got a 95% LMT rifle in terms of performance and durability.
Having said that, there are definite cosmetic differences in lowers. I’m kind of partial to CMT sourced lowers, myself.
agreed. for the most part, a lower is a lower. you can get a decent lower (LMT) for $110. i think i would build around the barrel. (20" SDI $400) your rifle will only be as good as your bolt carrier group and your barrel. your stripped upper will run you anywhere from $100 to $250 depending on the make. CMT/stag seems like decent upper and the price is right at $130. a good site to find parts in stock is www.ar15review.com
You have a pretty wide variety of options with building a rifle. Since you already have the S&W, you should take it out and spend some time shooting it. This can help you decide what types of things you might change on the rifle (if anything) or how you would prefer to set up the rifle you build later on.
As for building, a complete lower can be assembled easily with a minimal investment in tools. The only specialized tool I purchased for my first lower was a stock wrench ($10 from brownells). For my second lower, I picked up a few roll pin punches and a roll pin holder which worked well.
Assembling an upper will require a larger investment in tools. Unless you plan on building more than a few rifles you will be money ahead buying a complete upper. If you wish to add a rail system, keep in mind that some of them require removing the barrel for installation.
I’m still pretty new to the AR. The first rifle I assembled was a FAL. Headspacing is the most critical part of the build on a FAL so I learned to be pretty cautious about it. I understand the mechanics are different on the AR design, but I’d still check the headspace on an upper I built up from parts. A decent gunsmith should be able to do this for you for a small charge.
AR headspace is very important in terms of it needing to be right, but it almost always is. it’s not adjustable, and is set the moment the barrel extension is installed on the barrel. so long as you buy a quality barrel and a quality bolt/BCG, you’ve got a better than 99% chance its fine. it’s a good idea to get a gage set and check your headspace, but keep in mind that if your gages fail the chamber, there’s nothing you can do about it.
i’ve built a multitude of ARs, and never had a problem with headspace in a new build, for what its worth.