284 Win. AR???

[300LW]

Would this make any sense? What barrel length would be required for optimum performance, and what would be the effective range?

I'm looking at alternate cartridges for the LWRC REPR. 7mm currently has my attention based on articles by Bryan Litz. Any feedback is greatly appreciated.

 

[jpach]

Re: 284 Win. AR???

I would suggest 7mm-08. IIRC the .284 would be beest suited for a bolt action with longer mag length to allow the use of heavier and longer 7mm bullets. In a .308 AR mag, the case OAL would not be prime for the 284. 7mm-08, however, should be just fine.

 

[FCS]

Re: 284 Win. AR???

284 Win in an AR would be severly hamstrung by magazine constraint on OAL.

Based on my 243AI AR-10, you'll have some putzing to do for reliable feeding.

7-08 would be a much better choice than 284 for an AR build.

 

[ORD]

Re: 284 Win. AR???

The 284Win is an available cartridge for use in the AR-10 platform rifles, but as folks have pointed out, you get screwed on the COAL because of the mags. Most all of the semi-auto AR-10/LR-308 mags on the market limit you to a 2.80" COAL whereas the best loads for the 284Win will need approx. 0.1" or more (2.90") in COAL.

 

[captrichardson]

Re: 284 Win. AR???

Per the posts above, you are not really going to be able to take full advantage of a 7mm bullet in an autoloader.

The best performance for a 7mm is going to require
- larger powder load from something like a .284 or 7mm WSM to get it up to optimal speed
- the longer COAL to get the bullets seated where you need them

The best that you are going to do in an autoloader in terms of a 7mm will probably be a 7mm-08, which Remington/DPMS offers the R-25 in that caliber. Unfortunately the 7mm-08 can't take full advantage of what the 7mm has to offer.

If you want to run an autoloader, you may want to take a look at the 6.5mm offerings like the .260 Remington and 6.5 Creedmoor.

I have had pretty good luck with my DPMS LR-260. They will not match the Bolt Guns in terms of performance, but if you are willing to sacrifice optimal performance for the advantages of having an autoloader they do what they were intended for well.

Best of Luck,
M Richardson

 

[sandwarrior]

Re: 284 Win. AR???

The problem with all AR's -15's and -10's is that you have to give up either powder room in the case (or case size) or bullet length.

The .284 will work in a way though you may not expect. You can take a 140 Berger VLD and seat it right to the ogive to get magazine length in an AR-10. You won't be able to chase the lands out with it but they will still give pretty good accuracy.

You're not going to get much better shooting a 7mm-08. The 168/180 Bergers barely fit in that case either to go in a AR-10 mag. On the backside they take up a lot of case room. Mine are loaded to 2.950" which is .150 too long for the mag.

So, you might as well go with the lighter bullet with a good enough BC and get more velocity. You can shoot the 168 Sierra's and keep the c.o.a.l. under 2.8" (mag length). Very marginal to get the 175's down to mag length. You could trim the meplat some but that's counter productive to ballistics a bit.
both of those will easily get you to 1k and are a little easier to stabilize.

The last problem with the .284 in an AR is the time of gas burn. In a bolt gun, it's just add more slower powder to get more speed. In the AR's you can't have too much pressure down the barrel because it will break your rifle. That is unless you can go with an adjustable piston system.

I would honestly say your best velocity would come from a .284 shooting 140-150gr. bullets. 160 SMK's as well. The 162 A-max's are too long for the .284 but will just barely fit in the 7mm-08. In that platform yo would be hamstringing the .284 some but you would still get better velocity than with the 7mm-08.

The last problem is to get it to feed correctly. With the 7mm-08 it would be pretty much a straight changeover without having to adapt from a .308. The .284 would require some 'massaging'.

good luck.

 

[300LW]

Re: 284 Win. AR???

Thanks for the replies, you've addressed most of my concerns. Based on the comments it appears that case capoacity and OAL restrictions would hamstring the cartridge. I suppose I should look at one of the 6.5's. I'm just wondering if a cartridge change can extend the range of an AR-10 based weapon without going to a larger form factor.

 

[Big_Daddy]

Re: 284 Win. AR???

I would have to 2nd the idea of 7mm WSM being the way to go if you are wanting the .284" bullet in an AR platform. I don't have the name offhand but there was a company specializing in the WSM cartridges in the AR10 platform.

 

[300LW]

Re: 284 Win. AR???

Both 7mm WSM and 7mm SAUM would solve the case capacity problem but wouldn't feeding be even more troublesome?

 

[bignada]

Re: 284 Win. AR???

Armalite and DPMS once chambered their 10 rifles in .300 rem SA ultra mag. Magazines held 5 or 6 rds and were special.

Haven't looked at case dimensions to compare the .284 with the saum case, but .284 is .500 in body diameter fairly close to the .473 of the standard .308win.

Would prefer the .284 case as no need to machine or buy a mag face bolt... A bit of magazine lip modification, if any would seem to be all you need do. A .30/284 pushing 185gr Berger's would be a real longrange hammmer... Just remember to stay with IMR 4064 (maybe xmr4350) or faster burnrate powders.