The Nosler #4 manual has data on the 6.5/06 which is essentially the same case capacity of the 6.5x284.
That will give you some idea as to what a 24" bbl delivers.
The velocity loss will be almost the same as the .270wcf with 130gr bullets which also run about 3,000fps from a 24" bbl. A 22" tube will loose 80-140fps.
On the other hand, there's no real way to determine what YOUR velocities will actually run.
In 2004, I traded for a Remington M7 in 7mm-08 w/20" factory barrel (new rifle). I was planning to rebarrel/rechamber it to either 6.5/284 or .284wcf. I made the mistake of shooting it with some PMC factory 140gr ammo that came with the deal.
Best mistake I ever made!
The factory ammo ran across the chrono at 2,900+fps. What I was hoping for from a .284 or 6.5/284 and 200fps faster than a .260 with same barrel length.
Best accuracy however is at ~2,800fps, which is no big deal. Rifle has since taken 1-6x6 elk, and over 2 dozen deer. My all-time favorite centerfire rifle.
I've got a Savage M110 left-hand in '06 that I bought to rebarrel to 6.5/06 but just haven't gotten around to it. Have the dies and bullets/brass ect, but no barrel......
I think that you'll be satisfied with the rifle. Just don't get too hung-up on chrono numbers. Remember that the 6.5's get their reputation from the high S.D.'s and B.C.'s of the bullets. The only reason the match shooters worry about the velocity is to keep the bullets super-sonic at the 1,000yd line. And the original reputation of the 6.5's as game killers came from standard low-tech 154-160gr round-nose cup-and-core bullets at ~2,300fps.
I've got an aquaintance who's son that is a top competitor in NRA bullseye, rebarreled him a Remington M700 with a Shilen barrel in 6.5x55. His 26" tube runs 140's at about 2,850fps and shoots under 2" at 300yds with the Lapua Scenar OR Sierra MatchKing..... He shoots deer with a 125gr Nosler Partition and gets monotonous Bang-flops out to,,,, way across-way out there on a gas-line ROW and soybean fields in South Georgia. (one shot he claims was over 600yds according to range finder).
I'd get the 6.5x284 and FIND OUT WHAT IT ACTUALLY GETS...... I'd bet that it will suprise you.
FWIW; I've got a Savage M110 in .300RUM with 26" bbl. It actually has the same throat as the .300WbyMag rather than the short Remington throat (.375" free-bore). With the 26" tube, I'm seeing max pressures at about 1.5-3.0gr under book listed max loads,(ie:Retumbo at 98.5gr gets 3,300fps) and more than 100fps higher than max load listed velocities for the 26" Remington tubes. My IMR7828 loads for 180gr bullets are ~200fps faster than those listed in the latest Speer book with the SAAMI 24" test barrel at same charge weights.
Savage sometimes does some things a little different than the other manufacturers. Who knows what they'll do with the 6.5x284. I'd bet it actually comes with a 24" or 26" tube as does their 7mmRemMag rifles, rather than a 22" as may be currently listed. My above mentioned M110LH '06 has the SHORTEST chamber of any '06 I've ever measured/loaded for. It requires ALL bullets to be loaded to SAAMI spec's or they won't chamber. It also won't take the usual loads. IE: a 150gr spt with IMR4064 is usually listed as max with 52.0-53.2gr. Mine max's out at 50gr with slightly sticky extraction, and faintly cratering primers.... but, velocities are right up there at near 3,000fps from the 22" bbl . Go figure!
So, just like the fellow above with the re-barreled Montana action (slow barrel), you don't know what you've got till you try it out.
