IMPORTANT:
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Blank Adapting the M1917A1 Watercooled Machine Gun
Date Written: November 2011
Author: Chris Guska
Blank Adapting the M1917A1 Watercooled Machine Gun
1.) Selecting blanks
2.) Feedway modifications
3.) BFA Construction
4.) Gland Packing (You are here)
5.) Belts vs Links
6.) Feed parts
7.) Troubleshooting
4.) Gland PackingThis is critical if you want to run the gun "wet" with water in the jacket and not having it run all out at once.
Originally, asbestos string was used... obviously that is no longer an option. The modern off the shelf options are pTFE string, Graphite string, and O-rings.
I personally use pTFE string and have foound it to be acceptable.
What you're looking for at the hardware store is 3/32nd's pTFE typically used in valve packing. It should be $3 or $4 for a 24 inch long piece. This is enough to pack 2 or 3 1917's.
Packing the 1917A1 can be a bit fiddly at first, as it is very much a "feel" kind of thing to get the right amound of friction / packing buildup to keep water in, but not to retard the action to the point that it wont cycle.
The rear gland is pretty straight forward. It is a groove in the barrel that you simply fill. TIGHTLY begin to wrap the string around the barrel one full wind, then as it meets the starting end. Holding the starting end in place, start the second wind in the groove at an angle over the starting end and wrap around till it meets the angle. Cut / clip the string off so that you have everything filled, yet the string is tight. Use a small screwdriver to tuck the end in, then press and flatten the TFE string so that it is flattened into the groove and roughly flush with the barrel profile.
The packing should be flush and smooth with the outside of the barrel. Its OK to have a slight bulge over the profile, but it should not be sunk below.
Use a wipe / smear of waterproof high temp bearing grease on the barrel and test fit it in the gun. It should be a smooth fit and not bind or cause the action to require undue effort to operate.
The front bearing is a little less straightforward. Wrap a piece of TFE string around the barrel for 3 to 4 wraps and cut to lenght. Use a smear of the same grease on the barrel for the front 2 or 3 inches of the barrel. Wrap the string around the muzzle of the barrel while installed in the gun. Use the muzzle gland nut to push the string into the gap and tighten down till it is 2 or 3 full turns out of fully "down".
Operate the action to see that it does not bind and still operates smoothly.
Fill the water jacket. It takes about a gallon of water. Check for leaks as you operate the action. You may need to adjust the muzzle gland to tighten up to stop leakage or open up to allow free movement of the action.
Testfire and have fun.
