"....358..." Hi. .358 Winchester? You want bullets or loaded ammo? Where you are is important. Buying either ammo or bullets on-line gets expensive when shipping is added.
Loaded ammo is pricey. Shooter's Choice, in Waterloo, wants $60.95 per 20 for 200 grain Winchester ammo. Brass runs $39.95 per 50. Hornady bullets runs $42.95 per 100 for 200 grain RN's. $50.95 per 100 for SP's. $52.95 per 100 for FTX bullets. $61.95 per 100 for 250 grain RN's or SP's.
Epp's lists it too. However, your local gun shop can order anything you want in whatever quantity you want. Be prepared to pay up front.
The .358 Win uses a #3 RCBS shell holder. Same as the .30-06, .308, et al.
Got load data? Buckets of it on Hodgdon's site.