Looking to build a custom gun on one of these cases, which one is a better choice and why?? Thanks

Kind of different ends of the stick. The Wby. is going to give you about the max. in a 1/4 bore. The .25x.284 is a .25-06 in a shorter case, but needs a long action anyway (to seat bullets out where they belong). If you want max. vel. get the Wby., for a nice allround 1/4 bore, built slim & lt. wt., go .25-06.

ask over at www.24hourcampfire.com id go with what ever one that you like. they are both good for what they do.

Have hunted with a 25-284 since 1965 - rechambered a Remington 722 that was a 257 Roberts. It is a short action -same as a Rem Model 700. Shot many animals with almost every bullet possible - including nice caribou in Alaska - dropped in its tracks with a 117 (no longer made) gr Nosler behind the shoulder. Even with 120 gr bullets I could reach 3100 fps with H 4831 - bullet seating depth not an issue - its deeper than would be for a long action but the numbers don't seem to suggest I'm loosing anything - no action re-work either for the wider case. 3300 fps with 100 gr which I prefer for this caliber. The barrel is pitting near the throat now but accuracy still superb. The 257 Weatherby is a different animal - much more power and a long action needed. Good Luck

price weatherby brass first. then decide if you want properly headstamped brass. next, choose barrel length. if you go the weatherby route then 26" is on order to get the maximum use of that case. if you are building a flyweight then the 22" 25/284 should move up your list. if you like to be able to buy factory ammo in a pinch then it is weatherby for sure. bring your wallet.
or, you could build a really nice 25-06 AI and do everything the above cartridges would do, buy factory ammo if you choose for little expense. you can run in a 22-24" tube and also available of the shelf in many flavors. you can modify as you go.
personally i think the TI in 25-06AI would be the cats ass.....
good luck
woofer

I love my Mk5 but it is heavy, which is fine. If you want handy a 25-284 built on a 600 or mdl 7 action with a little scope and a light stock is perfect. 100 grain barnes and partitions don't take up alot of room and really sizzle. I'm trying to talk an uncle out of an old rusty beat up 600 to transform into a 25-284 myself.

really hard to answer the question without more info... there are a lot of great quarter-bores out there, but you've gotta know the WHY before we can tell you WHAT.

I hunt deer with a 25-06, best whitetail, mulie, 'bou, and sheep cartridge out there... IMO, now, I'm replacing it with a 258wby Vanguard, why? cause it makes a bigger BOOM!!!!

for a gun that will only be used sparingly and not abused and with no need for off-the-shelf ammo, 257roberts AI, for an "hunter" with some character, 25-06AI, and for sheer rip-roaring MV, the weatherby.

again, comes down to the "why"

from teh two you list, the wby is the easy choice for me. but I will admit to being conflicted personally on my choice to scrap the 25-06 as it is a FINE round out to 350yds. and there is EXCELLENT factory ammo available. (btw, be sure you have enough twist in the barrel for your bullet weights... mine doesn't like anything over 100gr, which totally kills it for me as I MUCH prefer the 117s and 120s.