Similar?
http://www.ray-vin.com/tech/slinghelp/slinghelp.htm
http://www.nealjguns.com/ss_store/Slings.html
On our old match Anschutz .22's we had a clip in sling.
You'd buckle it to your bicep and it would clip with a swivel clip, into an adjustable rail under the forward stock. The further you moved your supporting hand toward the clip's location, the more tension you'd create almost locking your arm in position. Very stable once you get used to it.
As seen here, it can be done with an old service sling.
http://www.snipersparadise.com/marks...th_a_sling.htm
Here's the quick-cuff:
http://www.tacticalintervention.com/...gmodeltwo.html
