Primers for .243 (confused)

Hello. I am new to reloading,and I am planing to reload 85 gr TSX Barnes bullets in .243 wit Hunter and Varget powders.I bougt the Barnes reloading manual number 4,and it mentions for this load : Federal primers GM210M,so I have being trying to get them with no succsses. In other chapter, for .308 it mentions Federal 210,for other caliber 210M; at Cabela web site they only mention federal 210 Large Rifle.
Is the federal GM210M diferent from 210,210M.210 Large rifle ?
Can any one be used for this load?
Any idea why the manual uses diferent letters?
Any information will be apreciated.

Sounds like a little clarification is in order here, and that's no big deal. The 210 and the 210 Large Rifle are exactly the same, the respetive writers are just using slightly different vernacular. The 210M is a different primer, but can be used interchangeable with the 210. The 210M is a Match primer, while the 210 is the standard large rifle primer. Priming mixes and compounds between these two is identical. The 215 is the Magnum primer, and would require reducing the load and reworking it. Primers in metallics (unlike shotshell reloading) are actually pretty interchangeable, and you're not locked into just using the 210. Any Large Rifle primer, such as CCIs, Remington's 9 1/2 or WLRs can all be used in the same cartridges. Just start at the lowest loads listed, and work up with the new primer as pressure signs dictate.

There is, unfortunately, no standard abbreviations used between the various manufacturers, leading to some confusion for the reloader. Some may list a legend, explaining what abbreviations they use in their manual, but ther than that, it just comes down to determining what's what by a little investigation.

The GM in the GM210m is Gold Metal as in Gold Metal 210M or a 210 match primer.

They are basically a high quality(match grade) large rifle primer. A CCI BR2 would be an equivalent.

A number of other large rifle primers could be used in place of that specific primer.

Winchester WLR,Federal 210, CCI 200,Remington 9 1/2, etc.

Thank you gentelmen,you have clarified all my doubts in such a short time.Thanks again.