Index Home About Blog
From: (Bart Bobbitt)
Subject: Re: Maintenance for gas-operating semi-autos
Organization: Hewlett-Packard Fort Collins Site

Our MENGM (Most Esteemed News Group Moderator) [pronounced men-gum]
had these words about frozen water and me:

: [MODERATOR:   *gulp*  I always feel I'm on thin ice when I mention
: something contrary to Bart's advice ... but ...

You're not on thin ice.  Besides, the pond is very shallow; the water at
high tide in July doesn't even come up over your shoe soles.

And these words he got from a 'smith:

: Many gas operated rifles
: (certainly not all) and the M14 specifically are made with the intent that
: the gas piston should work dry, not lubed.

Well then, why are all the military team members at the Nationals, Inter
Service, Regional, State, and hundreds of local matches putting Hoppe's
No. 9 in their M14's gas cylinders to keep the powder residue from making
the piston get sticky and not return to exactly the same place for each
and every shot?  When that floating gas piston rests at different places
for each shot, the groups open up vertically about half a MOA.  I don't
think those folks want that to happen.

Remember that Hoppe's No. 9 is not a lubricant, but instead a powder and
copper solvent.  It softens any powder residue on the gas piston and
that soft stuff is easily blown out on the first couple of shots.

The way to ensure the gas piston is free and not bound up is to raise and
lower the rifle's muzzle so you can hear the piston bouncing off the op
rod and gas plug.  If it's not free to slide back and forth, it's gummed
up with powder residue.  Put in some No. 9, let it set for several minutes,
then raise/lower the muzzle from a horizontal position.  The piston should
now be free and heard pinging off each end.  If this doesn't free up the
piston, then you gotta remove the plug with that special tool, then use
special reamers (or the right size drill bit) to peel out the powder
residue well-bonded to the cylinder walls.  And clean it off the piston,

But I agree, the piston `should' work when dry.  The reason it doesn't is
due to extra-dirty, extra-fouling IMR4895 powder used in M852 LC Match Ammo.
Why in anybody's name does the best high-speed metering powder for decent
LC match ammo have to be so darn dirty?  When IMR4064 is used, both the M1s
and M14s gas system isn't powder-fouled nearly as much.  They don't need
cleaned with No. 9 nearly as often.  And with most service ammo being
loaded with ball powder, the amount of powder fouling is even more reduced.
Which supports the `gas piston should work dry' philosophy.  But match
grade service rifles are not used quite like their standard service version
was designed for; they are expected to drive tacks (with very small heads).
So, to do that, they have to use extruded powder that satisfies several
mass production requirements; IMR4895 does just that.  The compromise is
that you gotta keep powder residue from gumming up the gas piston works
and that takes extra effort and a few drops of good old Hoppe's No. 9.




With all that hot air just dispersed over the pond, I think that thin ice
has melted and all the water evaporated.  Now you're standing high and dry.


	[MODERATOR:  High and dry .. the story of my life ....  :-)
		(Thanks as always, Bart.) ]

Index Home About Blog