Designate grooves? Anyone know for sure?

I’m sure it’s somewhere in Rule, but I haven’t been able to find it.

image upload site

(GI seller photo)

That ‘6’ appears to have been Winchester’s under barrel caliber stamp for 264 Win Mag barrels. There are numerous other examples out there.

Thanks PJ. Have seen several so marked; as you stated.

AKWolverine: I thought it was a "9" myself?
Naw, just funnin ya - I have no idea what it designates.
I am guessing production marking to designate something?
Good luck in finding your answer.
Hold into the wind
VarmintGuy

They say Winchester’s stamped a 6 on the underside of the 300 win mag barrels as well. To designate 6 groove barrel.

I own several but I have never pulled the wood off to look.