IMPORTANT:
Proceed at your own risk. We're not responsible for you blowing yourself or your gun up
Blank Adapting the 1919a4 Browning 30 Caliber
Date Written: September 2011
Author: Chris Guska
Blank Adapting the 1919a4 Browning 30 Caliber LMG
1.) Selecting blanks
2.) Feedway modifications
3.) Booster / BFA modifications (you are here)
4.) Belts vs Links
5.) Feed parts
6.) Troubleshooting
3.) Booster / BFA Modifications
This portion is pretty straight forward in my opinion. I'll mostly cover this in photos. Basically, the idea is to take a 308 booster, thread it for a bolt, weld the bolt in, center drill the bolt and thread for set screws to make an adjustable restrictor type BFA.
Starting point: Unmodified 308 Booster. Note: The 2 piece style are "more correct" - in that the 1 piece straight wall style is a late war part. They do show up in the ETO, but are not in the majority.
Step 1: Threading the Booster for 5/8 NC
Step 2: Prep for welding. Chamfer the edge of the threaded hole to create a V for the weld bead to go into. Cut down a Grade 8 5/8 NC bolt to weld in place. DO NOT use allthread or a mild steel bolt. It will SEVERELY erode from the blanks.
Ensure that you cut the bolt to be of sufficient length that the set screw to be used later can sit fully inside, with material left for an internal shoulder. Weld the bolt in place.
Step 3: Dress the weld and recut the takedown slot.
Step 4: Center drill (5/16") bolt in preparation for threading for 3/8 NC.
Step 5: Thread for 3/8 NC or the set screw of your choice. Do not thread THROUGH - only thread deep enough such that the set screw to be used will sit flush with the takedown slot.
Step 5 - Center drill the set screws to the desired size.
I like using stainless steel set screws, as they do not require annealing as the hardened carbon steel plugs do.
I typically make set screws for 1919's from .115 through 0.195, increasing by ~ 0.010 per screw. The aperture size used can vary wildly depending on the blanks used as well as the gun itself. My browning 30's typically run @ around 0.145 - 0.165 with current surplus 308 blanks.
Step 6 - Parkerize.
Not gonna get into this. Its a whole article in and of itself. Of note, I do this booster modification and parkerization for a price. Contact me if you don't want to do the work yourself.
