Cast boolits in an FAL?

Hello all, I've been a longtime lurker about this topic for reloading 308 winchester cast loads for semi-autos. I've had good luck running powder coated 160 grain gas check, lee 312 casts on my AR-10, pushing them around 2000 fps, cycling, last round lockback, and with decent accuracy.

I also ran the same casts in my L1A1/FAL with great success with one caveat...the area where the gas port (gas port never gets blocked though) and the piston gunks up with fouling every 100 or so shots. This is at least workable, as I often service and scrub the gas piston assembly clean every range session, but I'd like to know if anyone has ever found themselves in a similar situation and have done any measures to prevent fouling when running casts in a L1A1 or any other similar piston driven semi-auto.

Maybe you have a burr or erosion in your gas port.
Many fals are build on parts kits from the 50s/60s/70s (i.e. 60+ years old) and some
(e.g. Imbel kits used in south american wars and izzy kits) saw real, hard battle use by 3rd world troops.
Is it an original factory barrel or an aftermarket barrel?
Some aftermarket barrels can be machined rough, and a burr in the gas port may be causing the problem.

Is the "fouling" in your gas block/piston lead (i.e. shiny), or is it powder residue?

Also, when you seat the bullet in the case, is there a lead ring shaved off by the case not being belled enough?
the lead ring may be faint/thin and hard to see, and would stick around the case mouth.

It's an original barrel. Fouling appears to be lead. Cases are belled enough; pretty sure i am seating the bullet without shaving it.

I doubt there's a burr around the port on an original barrel, unless it was NOS, but I don't think they beveled the edges like on a lot of new barrels. You can see if a local gunsmith has the tool to bevel the edges of the port. That may help.

I shot several thousand 311291s and 311299s loaded over 4895 with a dacron filler through a Belgian made FN-FAL I had years ago. The bullets were cast of COWWs and WQ'd then sized, GC'd and lubed (Javelina) in a 450 w/.311 H&I die. Never had a problem with any fouling of the gas system. I adjusted the gas adjustment so the load giving 1850 fps would just lay the cases at 2-3 o'clock about 2-3 feet from me when shooting prone.

If you clean the bore and eyeball down the barrel and look at the gas port
(its tough, I know) does the gas port look eroded?

What diameter are you sizing the bullets to?
Is your barrel chromed lined (e.g. Imbel) or plain steel (e.g. stg58)?
If plain steel barrel, could it be that your barrel is a bit oversized/worn and your bullets are a bit undersized,
and you are getting gas cutting which causes the lead fouling?

If your ar10 doesn't have this problem, maybe its bore is tighter.
Also possibly in a FAL the piston mechanism may allow fouling to build up (since the pressure drops when the piston moves),
vs. in an ar10 gas system, its small diameter (higher pressure) all the way back to the bolt, so fouling gets blow out.

I use to mess with the FAL platform. I would wager the gas port on your riFAL has rough edges.

Later,
Stephen

All i ever shot in mine was Portugese ball.