O.K., let me try this..
To use a leather M1907 sling, first, it needs to be attatched correctly to the rifle.
First, take the smaller of the two pieces and thread it through the butt swivel so that the hooked end is closer to the rifle, (inside), hooks facing away from the rifle.
Next, place a keeper, (small leather loop), around the longer portion of the sling, then thread the long portion through the brass loop on the short portion, again with the hooked piece of the long portion on the inside, closer to the rifle. Make sure that the first small leather loop is between the long portions' brass hooks and the short portions' brass loop. If you've done this right, both sets of hooks will be on the same side of the sling, and against the bottom of the stock.
Place the hooks of the short piece onto the closest set of holes on the long piece.
Thread the free end through the small leather loop, so that the brass loop of the small piece is completely encircled.
Thread the remaining small leather loop onto the free end of the sling, then take the free end and place it through the muzzle end of the upper sling swivel. Bend it back towards the butt of the rifle. Then pass it through the leather loop closest to the muzzle.
Now hook the long-piece hooks onto a set of holes on the free end.
NOW...
To use it, you'll need to either completely unhook the the butt strap, (short portion), or hook the short portions' brass hooks into the set of holes closest to the hooks, creating a very small loop on the rear swivel. Either appears to be legal for Highpower service rifle competition.
Next, you'll need to adjust the large strap to the length you'll use for the position you'll be using. (TIP: numbering the holes will make this easier to reproduce if you need to make changes in your position).
You'll need to place your arm through the middle loop in the sling if you've decided to keep the butt strap attatched. To do this, you need to first twist the sling so that your arm enters the loop from the opposite side of the sling, (note: if you're sitting with the rifle muzzle pointing to your left, the sling part closest to the stock comes toward you. If I'm wrong or you do this incorrectly, you'll get an edge of the sling digging into your wrist. Just change the twist direction and try it again!).
Slide the sling up onto your bicep to where it meets your deltoid.
Bring your sling-arm hand back underneath the sling toward the muzzle of the rifle. Then place the sling arm hand as close to the front swivel as you can, between the stock and the sling.
Shoulder the rifle. It should be tight enough to hold the rifle into your shoulder without your firing hand supporting the rifle.
To adjust the sling, move the leather loops away from the brass hooks on the large portion of the sling. (If it's been put together correctly, the leather loops can be placed directly above and below the long portions brass hooks. This assists in maintaining the tension in the sling). Place the hooks higher or lower on the free end depending on the initial tension in the sling. You can pass the excess free end through the leather loop closest to the butt swivel, into the arm, (middle), loop.
It's alot easier to do it than to explain it without pictures.
The sling should be tight in your shoulder, but not necessarily tight on your bicep. My DI's and PMI's alwayls insisted that the bicep loop be painfully tight enough on the bicep to decrease the circulation considerably. I've tried both ways, and can't really tell a difference.
I hope this helps. Please feel free to tell me I'm fu~ked in the head.