Edited, see below.
My mistake, no one else’s fault for things not working properly.

Nevertheless, I’m still curious about the reason for a hole through the length of the screw that attaches the stock to the receiver extension (buffer tube).

Is it to allow water to drain out of the extension if the rifle is dropped into a river, or to vent the air from the tube when the buffer is driven to the rear during firing? (The hole actually seems to be a little small for the air venting purpose, but perhaps not.)

What say the authorities?

This message has been edited. Last edited by: sigfreund,

A bit of research revealed one Internet discussion about the subject, and as usual, it seems, with the questions I ask here, there is no clear consensus. Some think it’s for water drainage, others to vent air as the buffer cycles. It’s obviously not for direct water drainage because it’s so small, but it would allow air into the tube as the rifle is pointed downward and the water drains out the front. The air venting theory seems much less likely because again, the hole is so small; ever try to exhale quickly through a small straw or tube? It seems to me that most of the air would escape forward around the front of the buffer.

Anyway, I’ll leave this here for others who may have the same question, and especially for anyone who has a good, hard answer.

A vestige of the manufacturing process, perhaps. Maybe it aids in the extrusion process.

I was told, way before AlGore invented the WWW, that it was to vent, (water or air, or whatever) and part of the specifications drawn up for that part,

kinda like the A1 pistol grips having the round parts for the swivel (like on a AR18) that serve no purpose,

I would hope the rifle made fart noises as it cycled if you used an "unvented" bolt.

Edit:

It turns out I had gotten the factory stock screw and the Magpul PRS screw mixed up. When using the Magpul screw with the Magpul stock, everything is fine: Imagine that.
My mistake, no one else’s. (And the Magpul rep responded to my question very quickly and helpfully.)

But this shows some vented screws:

Vented screws.

This message has been edited. Last edited by: sigfreund,

According to the Colt armorers school I just attended it is an air vent to, in essence, prevent the buffer and extension from acting like a shock absorber and causing short cycling.

Yes, the answers vary.
The Magpul rep I was just in contact with said he understood it's to help water drainage.

The vented stock screw is there to give moisture a way to exit the buffer tube as the rifle heats and cools. I have non vented screws in some AR's and they don't short stroke due to the lack of the vent.

And here's PS magazine's own Sgt Halfmast laying down the buttstock PM for you. The vented screw is mentioned as a 10 level operator maintenance item.

"When you’re cleaning your rifle,
run a pipe cleaner through the buttstock
drain hole to clear it. If the hole
plugs up, moisture can collect in the
buttstock and corrode the lower receiver extension."


PS issue 573, "No buts in buttstock maintenance".

quote:

Originally posted by SgtGold:
And here's PS magazine's own Sgt Halfmast laying down the buttstock PM for you.

Very informative; thanks.

quote:

Originally posted by arcwelder76:
I would hope the rifle made fart noises as it cycled if you used an "unvented" bolt.

A farting rifle?? Watch out -- these might be phased out with cows. And Mexican food. And any food made with tofu.

Got to keep the greenhouse gases under control.