Re: Let's talk 7mm choices ....
There are lots of great caliber options in the "7mm" (0.284") bullet diameter category. I put 7mm in quotes because it really is 7.2mm, but commonly referred to as 7mm. Everyone has their own preferences, but here is a quick summary from my perspective.
7mm-08: Popular for high powered silhouette shooting. Norma and Lapua brass are excellent. Triumphs 308win with less drop and wind drift because of higher BC bullets for weight. Does not match the velocity of short mags or rem mag, but shoots more efficiently from shorter barrels (e.g 20" to 22").
284win: In between 7mm-08 and mags in velocity and barrel life. Limited availability for good brass. "Wildcat" 6.5-284 is more popular the parent cartridge.
7mm WSM: Winchester brass is relatively reasonably price, it is good if your sort and prep. Larger case capacity then 7mm-08 and 284win gives you higher velocity, and essentially matches 7mm Rem Mag in a short action. Some argue that in order to seat to high BC bullets (180grs), the case capacity shrinks too much to maintain enough of a charge for higher velocity nodes when feeding from an AI magazine and that you really need a long action...however Alpha mags & Seekins makes magazines that allow you to seat bullets long.
7mm SAUM: Nosler brass is supposed to be better, and more expensive, but it is very difficult to find in stock. It is slightly more "efficient" than 7mm WSM with similar velocities at slightly lower charge, but 7mm WSM has larger case capacity and thus slighly higher max velocities. To me, this is really splitting hairs, and they are essentially almost identical, pick either 7mm SAUM depending on your rifle, brass, etc. preferences.
7mm Rem Mag: Much more options in factory loaded ammo and rifles. More case capacity then WSM and SAUM, but does it less efficiently needing more powder for same velocities, and thus shorter barrel life. Belted case is not liked by many reloaders, and may be less inherently accurate than short mags.
For the calibers, of course, as you go up in velocity, you trade that for shorter barrel life.
There are other 7mm (0.284"), such as the 7mm Dakota and 7mm STW that are popular with hunters, but less so for competition shooters.
For me, I would first think about what you will be shooting and at what distances. I presume you reload, otherwise I think 7mm rem mag is the only real viable options for you. Then I would consider what barrel length is acceptable to you. To take full advantage of the short mags, and get near complete powder burn for their larger case capacity, at least a 24" to 26" barrel is preferred. If you are going with a 22" or shorter barrel, then look at 7mm-08 or 280AI instead.
