REALLY NEW to BIY but wanting to start right- I need help swimming through the BS

**Bucking the system** · 03-03-2007, 06:09 PM

As I looked around, I found titanium, 4140, 7075, 6061 and a number of other 80% receivers. I also found something (most of you know what this means but I do not!) that was called an 80%+2% receiver. I found the list of exact screws and taps and I found the approx screws and taps to the metric ten thousandth.

I thought by researching, I would find the info that I needed to make a good start at an 80% AR lower, but I have become a great deal confused at what I need to begin the process of the lower. I do want to build an M4 and an AR10, and I really would like to know the real basics on what I need to begin.

I have found great costs on castings, but I know that a forging is better. I read that 7075 is a waste, and that a steel 4140 is what I need.

Any of the vets out there have a list of absolute do's and don'ts. I really need them. There are so many options out there that I cannot begin what I want to do without a good foundation of understanding what is really needed.

Thanks in advance for the input!

flopshot · 03-03-2007, 06:30 PM

first rule of fight club is you don't talk about fight club.
first rule of AR's is you donn't "build" AR's, you assemble them.
best bet is a quality full lower, and a parts kit and the upper of your choice.
buy a quality lower, upper, and "assemble" it.
when you're ready to 'build', look into the AK kits, VZ58's, or FAL's

kernelkrink · 03-03-2007, 06:36 PM

OK, first of all "percentages" are a marketing tool, basically describes the amount of machining left for the homebuilder to complete. What a manufacturer does is submit a sample of his partially completed receiver to ATF and ask "is this a receiver or not?" Depending on the answer, he adjusts the amount of work done to the piece until he has a product that is not a receiver according to ATF, yet is still far enough along that it is capable of being completed by a home builder. Back in the day, the first people doing this decided their approved products were about 80% complete and the term stuck. An "80% +2%" is simply a receiver blank that has had a little extra machining done to it than most of the others, but still falls under the "not a receiver yet" criteria. IIRC, these usually have the buffer tube hole already tapped.

Aluminum works just fine in an AR lower as there is very little stress on it. Steel is overkill and adds to the weight, perhaps for an AR10 it would be justified but a semi Ar15 will do fine with AL. Ti is hard to work with, AL is much easier to drill and tap. Forgings are mil spec, but castings appear to hold up well when full auto fire is not an issue.

There are several options to start out with. The raw forgings and castings that do not have a completed magwell and FCG area are the most difficult, they will have to be cut out and that takes a lot of effort and special tools. One that has the magwell completed and the FCG area machined out is a lot easier, mainly those just require drilling and tapping holes, and hand filing the mating surfaces to match the upper. You can rent, buy, or make the jig plates that fasten to the blank to precisely position the holes, as well as rent or buy the tools to drill/ream and tap. For a one-off build, you could probably hand lay out the holes if you have some experience, but the jigs make everything a lot easier and repeatable.

**tanvil** · 03-03-2007, 09:40 PM

DEPENDING ON YOUR EXPERIENCE, A STRIPPED LOWER MAY BE A GOOD WAY TO GO. YOU CAN ASSEMBLE IT TO YOUR OWN LIKING AND PRICE RANGE. BUY A COMPLETE UPPER W/ BOLT CARRIER,POP YOUR PINS IN AND GO TO THE RANGE. I'VE PUT MANY TOGETHER. I DON'T HAVE THE MEANS FOR MILLING AN UNFINISHED ONE. SO THIS WORKS REAL WELL FOR ME. CHECK WITH FULTON ARMORY, THOSE GUYS ARE TOP NOTCH FOR AR, M1A AND GARANDS.

**tanvil** · 03-03-2007, 10:56 PM

7.62X39 RECOMMENDED CNCGUNSMITHING.COM. I WENT THERE AND NOW I'M CONVINCED IT'S NOT AS DIFFICULT AS I THOUGHT. THEY SELL A JIG THAT CENTERS IT FOR DRILLING AND LOCATES YOUR BUFFER TUBE. CHECK WITH THEM, THEY SEEM TO HAVE DONE AWAY WITH ALOT OF THE PROBLEMS THAT CAN TURN IT INTO A PAPER WEIGHT. THANKS 7.62X39!

**Bucking the system** · 03-04-2007, 12:42 AM

Thanks for the input. I have built up (assembled) two AR's in the past from kits and from finished receivers. I recently went to the extreme and began machining and learning the tricks of that trade. Has done wonders for my knife making, as well.

I wanted to learn how the metal is cut out and make my own, but there is so much info out there that it was hard to make sense of the many opinions. I appreciate the info on the AL. Heard from 2 sources that it was substandard, but I knew little stress was placed on the receiver - so it made little sense to me.

Thanks Kernkrink and Tanvil. I appreciate the input, informations and suggestions. I will look into the CNC site, and I have much of the equipment and tools needed to build up an 80%. I really would like to put an accurate AK together. Finding those more attractive all the time.

Again, thanks to all of you. I appreciate the kind and informative responses to a newbie.

Buck

kernelkrink · 03-04-2007, 12:54 AM

No problem Buck, always glad to be of assistance. BTW, I have an extensive collection of PDFs and blueprints of the AR15, as well as several step by step photos of someone machining a lower from one of the DSA raw forgings. PM me an email addy where you can receive several megabytes of attachments and I will send them your way.

**Bucking the system** · 03-05-2007, 01:37 AM

PM sent, kernelkrink. Thanks a bunch!

Buck

**Bucking the system** · 03-05-2007, 01:40 AM

Tanvil, thanks for the link. I will be checking it out. Got to get to bed. This could turn into an obsession if I am not careful!

**tanvil** · 03-05-2007, 07:57 AM

THERE ARE WORSE ADDICTIONS OUT THERE, DON'T WORRY. MY WIFE ALWAYS TELLS ME IT'S BETTER THAN SPENDING YOUR EXTRA MONEY IN THE BAR. SINCE YOU HAVE ACCESS TO THE TOOLS, WERE YOU GOING TO BUILD THE UPPER ALSO? YOU MIGHT CHECK FULTON ARMORY. RICH IS A MASTER ARMORER. I HAVE A COUPLE OF HIS "CREATIONS", ALL SUB-MOA OF COURSE.