If your looking for the USGI style cotton slings for M1 or M14, the ones with the metal buckle and the metal piece at the end that quickly detatches from the sling swivel, CMP sells them for something like $9.
Brownells used to sell some, but there were complaints. The two main complaints were:
1. Nylon ones buckle didn't clamp tight enough to keep the sling tight when using is as an accuracy aid
2. Near the buckle the sewn section was tripled instead of doubled. This caused a larger bunch of stuff that gets in the way
CMP's have only a double sewn section near the buckle, and they don't carry nylon.
Cons to ordering from CMP:
1. They don't always have them in stock (not really specific to CMP)
2. They sometimes take a long time to ship items
3. I think (not certain) that you have to be eligable to order from CMP
4. If ordering only one sling, shipping is almost as much as the sling (again not specific to CMP, likely going to get $5+ shipping anywhere)
Brownells used to sell some, but there were complaints. The two main complaints were:
1. Nylon ones buckle didn't clamp tight enough to keep the sling tight when using is as an accuracy aid
2. Near the buckle the sewn section was tripled instead of doubled. This caused a larger bunch of stuff that gets in the way
CMP's have only a double sewn section near the buckle, and they don't carry nylon.
Cons to ordering from CMP:
1. They don't always have them in stock (not really specific to CMP)
2. They sometimes take a long time to ship items
3. I think (not certain) that you have to be eligable to order from CMP
4. If ordering only one sling, shipping is almost as much as the sling (again not specific to CMP, likely going to get $5+ shipping anywhere)