I am no expert when it comes to building AKs but I am trying to learn!
I have drilled and tapped four AMD-65 kits now for screw builds and two of them were for myself and two that I drilled and tapped for another guy. The problem with drilling and tapping is that those little taps just don't like steel that hard and they brake and brake easily and there are times I swear they brake even if you do everything right. When the f-ing things brake you will have a bitch of a time getting the tap back out of the hole! The only other thing that seems to be a problem with screw builds is that guys drill too deep and they ruin a barrel.
Now, if you buy a press and pull the barrel you could drill and tap without the barrel in the front trunion but if you have that much invested in tools you should just do the build with rivets.
As for rivet builds, I am still collecting the tools to do my first rivet build and I am doing it the expensive way. I have bought all the fancy gismos that come from lots of careful thought in the past and you can see the list of tools I have purchased here:
www.quarterbore.com/forum/viewtopic.php?t=73Figure the folowing prices:
$90 for barrel pressing tools
$125 for used 555th jig
$100 for 12-ton H-press
$120 for Plinker's rivet press
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$435 invested in AK tools and doesn't include standard tools like headspace gauges, files, and the other general tools.
It would require building more then a couple AKs to make this pay for itself when you consider a very functional SAR-1 can be bought for about $350!
I would suggest doing your first build with the cheapest kits you can get and make your mistakes with that one. After you do your first kit you will have a better idea of what you are doing and if you have the right tools it should be easy to build a really nice weapon!
Hope this helps... and I am a newbee to AKs as well!