I order from Numrich Gun Parts once in a while (http://www.gunpartscorp.com/) and found a trick to get discount on shipping, which can either make it free shipping for small items or some decent discounts.

Your Order Total
Under $9.99 $4.95
$10-$19.99 $6.50
$20-$39.99 $7.50
$40-$79.99 $8.50
$80-$139.99 $10.50
$140-$249.99 $12.00
$250-$399.99 $13.50
$400 or more Actual Shipping Charges($15.00 min. charge

All you have to do is call 866-NUMRICH (866-686-7424) during their business hours, M-F 8:00 a.m. until 7:00 p.m. Eastern. Go through as if you are going to place an order, you will then be instructed to hang up and order online and use coupon code xyz for the discount. The code changes often, I think maybe even daily.

I know it's not much, but I figure it's worth sharing.

Al