Has anybody used the BFH method(Big Fucking Hammer) instead of using a 12 or 20 ton press to bend your flats?

If so how well does it work?

I have.  It works.  I can see where a press could be easier.  Mine turned out just fine.

I tried a hammer and had no luck.  I think I needed a bigger hammer.  I just didn't like the idea of banging on my $125 jig with a hammer.  Used my buddies press and had the whole thing done in 10 minutes.

It works fine.  It will take a lot more time and effort than using a press and jig.  It just doesn't make sense to invest in a press and jig to make a few receivers.  

Although you can start with a piece of sheet metal an make your own holes in it, it probably isn't worth the trouble since you'll have to find an appropriate alloy.  Premade receiver flat can be bought for under $15.  Screwing one up isn't the end of the world.  

get two bars of flats stock 1.25 inches wide (the internal width of the receiver).  Half inch thick is probably best.  You will need to drill hole through both in several places along it's length to match of with the holes already in the receiver flat.  Use 1/4-20 bolts.   You will need to grind notches in the bar that will be on the inside of the receiver to provide clearance for the dimples (unless your flat doesn't have dimples) when it is folded.  Make sure the ground notch in the bar only is made to accommodate the dimple; the bottlom of the bar should have straight edges.  The top portion will have the notches ground in it.  

Center the to bars on each side of the flat.  Use dial calipers to get this centered a precisely as possilbe.  Tighten the two flats together with the 1/4-20 bolts.  You may want to get some quality bolts for this so they can be tightened a lot without snapping off.

Mount this assembly in a big vice and by with a chunk of wood, big rubber mallet, hand pressure or something else, start bendind one side partially, but don't used a hammer on it at this time without padding of some sort.  Just bend it a little at a time, flip over and do the other side.  It will not look pretty at first, but that wont matter if the bars are tight and don't slip.  How much each side and be bent will depend on the size and type vice used.  You sould be able to get one side bent most of the way.

Now get  a hammer.  It can be used directly on the receiver, but will like leave little dents all over it.  This is a cosmetic issue, but it is good to minimize it.  One way is to not hammer on it directly.  Get a thing piece of flat stock, place it on the receiver and hammer on it.  Tap back and forth the langth of the crease being formed a little at a time, be patient.  Eventually a sharp edge will be formed.  Do a little at a time.  Don't do each side independantly.  Do a little on one side then switch to the other.  At first the hammering is done with the jaws of the vice clamped on the two pieces of flat stock bolted to the receiver.  Eventually the assembley can placed on an anvil or back of the vice or other solid surface to hammer on the creases.  

As long as the bolted bars don't slip and were precisely centered to begin with things should be fine.  After bolting the bars be sure to measure again to make sure they are still centered before bending.

After the sides have been folded somewhat to 90 degrees and a good sharp edge has been formed, the bars can be removed.  It might take some effort to pop the inside bar out, especially if the flat as dimples (as most due). After the bars are removed, minor adjustments can be made with the hands until it is a perfectly 90 degrees.  Check with a combination square.  

You now have a partially formed receiver.  Make sure it is square and everything looks alright.  Take one of the bars that was orignally bolted together.  Deternmine the inside dimentions of the receiver between the bottom and the inside edge of where the upper rails will be and scribe marks.  This can be found from dimension drawings, or if you have the pieces of a cut of receiver that came with the kit being asseble, you can get the dimension from there.   Place the top edge of the bar inside the receiver aligned with these marks.  Clamp this together in a vice tightly.  Be sure to pad the vice some how.  Scratches are are to fix.  Maker sure the marks are still lined up with the bar.  Now hammer the upper rails down.  Do this lightly and slowly.  Hammer on a piece of flat stock of possible to minimize denting.  Be careful not to nock the bar out of alightment with the marks.

After all of this done, check for squareness and correct as needed.  All the rest is file or dremel too work to make appropriate notches in the upper rails and trimming things to fit.  Do this slowly and a little at a time untill things fit in place.  There will likely still be nicks, scratches, little dents or other cosmetic flaws afterwards.  Lots of sand paper or emery cloth work can correct this if desired.

It is amazing how sloppy a receiver can be made and still work with some tweeking.  It is also amazing how good of a receiver can be made by this method if enough effort and patience goes into it.  All done with common tools.

Bending jig: $125.00
12 ton press: $90.00
TAPCO flats: $15.00 ea.
Having all my fingers intact: PRICELESS
Seriously though a press is easier but you could bend one of these up fairly well using the BFH method. I just wouldnt do it using a jig.

The best way to do this is attend a build party.  Get enough people with all the tools and you're good-2-go.  That's what I'm doing and it's been schweet!!  There's gotta be a build party in TX somewhere.  

Couldn't we run nuts and bolts all the way through the jig (through the mag and trigger openings) to pull the flat and upper jig piece into the jig?  Could enough force be generated to bend the flat without snapping or stripping the bolts?

I read where someone (either here or Akfiles.com) used big C-clamps to bend them.  I bent four with a hammer and still have all my fingers.  The first was with a 3 pound hammer from Big Lots.  Worked alright.  Then I just pulled out an old 5 or so pound sledge thats been sitting in the corner and that seemed to do the trick a lot easier.  With less hits that is.  Either way.  If your jig is made good, you are not going to tear it up or hurt it with a hammer.