284 Winchester?

[jump70]

Gents

Also posted this in the varminting rifles section...

I posted a couple of weeks ago about potentially re-chambering a rifle into .308 or .308winAI, or anything else with potential that would feed through accuracy international mags in a rem pattern short action.

After a fair bit of thinking and talking to a few people, I'm now leaning towards .284 winchester (7mm/284) in a 9" twist barrel. It will fit and feed through my mags and has far superior ballistics to the .308. Downside is less barrel life than .308, although it will be noticeably more than its necked down 6.5/284 or 6/284 cousins. I'd form the brass by the simple expedient of necking up 6.5/284 lapua brass to 7/284.

The only concern at this stage is to load/feed rounds for LR hunting through the mags, I'd have to seat them pretty deeply - to about 2.800" or so. I'm a little concerned that I'd lose a bit of case capacity and potentially, accuracy, with some of the bullet shank probably going past the neck/shoulder junction. There'd be a fair jump to the rifling also. I'm thinking of the 162 A-max or 150 Nosler BT for the hunting application, although I'm concerned about driving the a-max too fast and having it break-up in flight.

Target/comp work is not such a big deal due to having to single load by hand after each shot, so I can seat the match projectiles out as far as needed.

Any thoughts?

P.S. Anyone know where I can get some 180gr Bergers? .7+ B.C!

[Tony Z]

Jump, you will never blowup the 162s in the 284 with a 9 twist. I doubt it would happen even with an 8 twist. The Amax got a bad reputation in the early days when the nose tip was an alloy, not a polymer like today, and they often came loose mid flight causing the bullet to fail to reach the intended target. But they had a much different profile than the current breed, were 1.5 inch long, and very sleek with a reported BC in the high sixes, but soooo inconsistant that they were not worth bothering with at anything much past 300m. They had to be shot in an 8 twist as anything slower would not stabilise them. The recent Amax's have had their fair share of critics, and are certainly not a patch on the good old 00-326 batch that many on this forum have won matches and set records with. They don't shoot to the 326 standard, but they certainly do not blow up, just have inexplicable flyers at long range. Shots that leave the group by ten inches or more at 1K in a completely random manner. I have removed the polymer inserts with a special tool i made up, re-cut the tips and reamed the cavity and then replaced the insert and then tested the product. The end result was that the work involved was returning a level of accuracy that was not enough to justify the effort. The 168 SMKs just shot rings around them at all ranges. The other thing about twist rates for this projectile is that the best accuracy i ever obtained was out of a 10 twist Maddco and later on an 11 twist in a 7/300 WSM. Faster twists i found were just increasing the RPM with no gain except increased vertical dispersion in strong winds at long range. The threshold i often talk about of 260,000 RPM with any projectile is applicable to the Amax more than most others, mainly because the spinup combined with a loose insert is what i consider the primary failure of this bullet. Your 9 twist at 284 speeds will be under this threshold.
As for the 180 Berger, i do have 400 of them for sale if you want them. 100 moly, the rest are clean skins.

Tony Z.

[Rinso]

The unfortuneate 7mm .. full of promise but the inability of consistantly getting a run of good quality bullets sees them suffer a less than promising fate.

cheeers
Rinso

[Plasmaboy_AU]

Hi Jump , I shoot a 284 Win in my F open rifle .. of course its much different to a hunting rifle .. but with a 1:8 twist trueflight barrel , with a load I guesstimated , the 162 AMAX's got me 2 x 98's at 400 meters . Thats two lots of 8 x 10's + 2 x very tight 9's on a 1/2 MOA bullseye. speed was 2980 fps .. So the AMAXs can keep up with the "bigboys" like berger and matchkings with ease . * amaxes are also a LOT cheaper then Bergers

[wem]

I also run a straight .284W running 175 SMK in FO. Just recently scored a 99 at 600yds at Castlemaine on the championship target. It can't be too bad.

Maca

[jump70]

Tony - If I decide to go down this calibre path, I'll definitely make you an offer on the clean-skin projectiles. Does anyone in Aus sell these - reason I ask is that 3-400 projectiles won't last long if they shoot well...

There seems to be nothing wrong with the 284 and it seems to be a much under-rated cartridge, although I do agree there isn't a wide range of projectiles to choose from. I don't have a lot of choice on polymer tipped projectiles to choose from for hunting purposes either...162a-max or 150 b-tip seem to be the main choices, or maybe the 120 v-max for a bit more velocity...

My only real issue is the round OAL when it comes to feeding my LR hunting rounds through an accuracy international .308 magazine. The 284 case fits ok but, OAL-wise, I'm going to have to seat them pretty deep - so the jump to the lands will be pretty long and I'll have to drop the powder charge, although to be honest, potential loss of accuracy issues as a result of deep seating/long jump is what bothers me most. Obviously, loading for comp is not an issue, given single loading