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· Master Endmill Breaker
1,302 Posts
Are you talking about the 80% Century castings for $14.99 from Tapco? I kid you not, I've seen them sell on eBay for $100 or more. I bought several from Tapco in hopes of doing versions in 7.62x39, .223, ,45ACP and maybe a .22LR. I don't think I'd trust one in .308 because of the need for perfect heat treating. They are supposed to be 4140 cast steel, so machining shouldn't be a problem with decent tooling.

There are currently NO correct/complete blueprints for finishing one of these. The drawings that are available for free online (or for $10 on eBay or gunshows) are all the same ones. These drawings assume a 0 reference point from the lower front corner of the receiver (just under the barrel). I've read several discussions that say this is a VERY bad idea. The general concensus was that the locking shoulder hole or pivot pin hole would be the best 0 reference. The biggest recommendation is to compare EVERY dimension to a finished receiver.

The drawings are available on Roderus forums in a couple different forms.;act=ST;f=14;t=191

The operations needed to complete one are (in no particular order):
mill sides flat and parallel (most castings are slightly twisted)
tweak magwell (all my castings have a sag that makes the mags fit too tight)
trim back of casting to length to fit lower
drill/ream pivot pin hole
drill/ream locking shoulder hole
mill inside width for bolt carrier
mill carrier rail slots
mill dust cover slots
mill cocking handle slot
open hammer slot (casting may be tight)
drill & tap bolt release/mag release hole
drill ejector block pin holes
trim casting to finished length
cut carry handle slot (optional)
bore barrel hole
bore gas tube nut hole
thread barrel hole (hopefully get the timing right)
thread gas tube nut hole
mill type I or type II lightening cuts (optional)
make openings in bolt rails for cartridges to feed properly (depends on caliber)
remove Century markings and replace with correct info
clean up machining marks
heat treat your finished part

None of the castings I have will line up correctly on any of my FAL lowers. They are all about 1/16" or so too long. If the back end of my castings are milled down that much, the pivot location will line up perfectly. That's where I plan on starting.

70% has been started...;act=ST;f=20;t=55
Some of his initial machining setups scare the hell out of me!

FAL CAI receiver for blow back?;act=ST;f=20;t=81

Century Arms Receiver Casting Alloy, Required info for heat treating;act=ST;f=20;t=78

· Registered
4 Posts
scubadvr said:
Have and of you guys worked with or have any knowledge about the 80% FAL receivers out there. How hard are they to work with, what needs to be completed and what is the best. thanks Jack
Couple of guys on the falfiles have done it. As with anything, the learning curve is the most time costly. I'd hazard a guess that completing a FAL receiver is MUCH more knowledge intensive than other commonly available builds.
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