85% or so competitive rimfire benchrest shooters use Eley brand ammo. Another 13% or so use Lapua. (my guess on the numbers, but its close)
Dan Killough sells Eley and whatever he has at the moment is listed on his web page.
http://www.killoughshootingsports.com/Webs/ammunition.html
Of the 85% probably 96% use either Tenex (the red box) and/or EPS (the black box). Most of us buy test boxes of several lots to see if we can find some killer ammo, then buy all of that lot we can find. Our rifles are often machine and speed sensitive so it does matter. Red Box runs about $15 per 50 and Black Box is about $10 per. Plus shipping.
Eley ammo is in short supply in the states just now. We are all waiting for the April shipment to come in so we can test and buy this seasons ammo. Eley Team is also good (Blue Box) and a bit less expensive if and when you can find some to buy.
The 13% or so of us like to use Lapua ammo. Charlie Scott is a good source.
His telephone number is 913-649-7658. There are three different Lapua that folks most often use; Xact, Midas+ and Center X. Xact is about $25 a box, Midas about $15 a box and CenterX about $10 a box. Plus shipping.
Me, I keep both Eley and Lapua on hand.
The last 2% use RWS R50, RWS R100, the new Federal made by RWS and various others.
If you want ammo to play with and practice consider SK Standard Plus or Wolf Match Target. They are the same ammo in different cartons. Either will cost about $4 a box plus shipping. You can get them from Midway, Champions Supply, Champions Choice etc.
If you are interested in what the winners shoot go to the ARA and/or PSL web sites and look at the equipment lists for the bigger shoots. You will be hard pressed to find something other than Eley or Lapua. bob