i recently put a sling on my B-26, using 'uncle mike's' swivels which are made to clamp to the magazine tube of a marlin or winchester lever action carbine.
i use a simple, black nylon sling, 1-1/4" wide, very cheap, no pad.
i used a modified 'hasty' sling with the left hand back near the trigger guard instead of in the normal 'front of the forearm' position
until saturday's match, i have never been able to hit a target at the mandatory offhand lanes. i can't remember if i got one or two points while shooting offhand, but the sling certainly made a difference.
When shooting WFTF/International, I always use a military (single point of attachment when in-use) sling for prone and kneeling and have used one for standing. I think it helps a bit for standing but the hassle-factor is high when trying to handle pellets, tighten coat, etc.
AAFTA rules definitely allow one for non-Hunter; for Hunter, the rules call for a two-point sling (like a hunter would use).
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