.300 SAUM vs. .300 WSM

Hey all,

Just bought a Les Baer .308 Match Semi-Auto and I'm loving it. I've been doing some research on upper conversions projects and I've run across the .300 WSM and .300 SAUM catridges. Both seem to have better balistics overall than the .308, and have very comparable balistics, and I was curious to know if they make upper conversions for either of these calibers for the AR-10 platform? My only real concern here is whether the rounds will feed through the AR-10 magwell which is designed for a .308 cartridge. Thanks for your help.

SAUM for an AR-10.

For the same reasons the 6.5 Creedmoor is a better choice than the 260 REM
in the AR-10.

Buy 2K-5K pieces of brass and have at it.

Armalite built some factory 300 RSAUM rifles a couple of years back (I have 2). The choice was made because the 300 Remington has a little more brass in the case head area, and the 300 RSAUM case is a little shorter than the Win. I do not know if the shoulder angle is the same. The 300 RSAUM factory rifles have the gas port moved (3 inches IIRC) towards the muzzle and used a quad rail extension on the older style float tube to cover the gap that resulted between the tube and gas block. They had the 24 inch T barrel, the ejector port was opened up slightly and bolt face was opened up.

The lower was same as a 308 just marked 300 ULTRA Magnum IIRC. The mag was a slightly modified 308 10 rounder, I think, and was called a 5 round mag. Some have experimented with larger mags with some success- I need to do so also.

There is a company, Accuracy Systems, that does many custom conversions- I have no experience with their products.

I guess my next question is how the ballistics of a .300 SAUM compare to a .308 remington? Would it really be worth the conversion if I'm looking at shooting 1,000 yards? I'm guessing the .300 SAUM will now have as much drop over 1,000 yards as the .308?

Also, I'm assuming the .300 SAUM use the standard .308 mags since the cartridge is shorter than the .300 WSM but is a larger diameter cartridge?

Thanks again for the help.

I guess I should also mention that I am wanting to start competing and I will not be using either setup for hunting purposes, or at least hunting isnt the main purpose.

The 300 RSAUM will push a 168 gr Sierra Match King 3000 FPS vs a 308 which runs about 2750 in maxed-out loads.

See the exterior ballistics of a 168 travelling at various velocities at:

http://www.exteriorballistics.com/ebexplained/4th-rifle_tables/pdf/308168hpbt.pdf

The mags are slightly modified 308 mags as I mentioned before. The 300 RSAUM is the same brass length and overall length as a 308, whereas the Winchester is longer. Mag length would require seating bullets deep in a Winchester Short Magnum. This then possibly means non-standard rounds vs. off-the shelf ammo for the RSAUM. Accuracy Systems will do a 300 RSAUM upper for about the same price as Armalite did when they were available, and you can use a standard lower. A good idea would be to buy a 308 T rifle then add the 300 upper if you want later, then another lower if/when you have the $$$.

Both Winchester and Remington are about $50.00 for 20 rounds factory ammo. I reload so the costs is less than that.

The reliability came down to the mags for me. I had one of the 1st 300 RSUM off the line and it would not feed, I sent it back and it runs with everything, even SPs. Reliability is there.

Standard mags, different follower.

You can find decent deals on RSUM brass at closeouts. I picked up 2k a few years ago for a song, but I shoot it in a bolt as well.

If you never have shot 1k, I would suggest going the 308 route as that will allow for more practice and make you a better shooter overall. It will be cheaper and there is match ammo available to make it easy. A bigger round does not mean better LR rifle. At those ranges the shooter is more important (spotter really) than the cartridge.

If you go to RSUM, you have to reload as there is limited match available.

If you are a relaoder, seasoned LR shooter, and just looking for a upgraded round in a semi rifle, then the 300 RSUM is for you. If not, there are better options

IIRC the follower a slightly modified Gen 1- my factory mags are. I have not tried other mags/follower mods and would like to know if anyone had success.

I have experience with short magnum rounds in bolt guns. They are a lot of thump for a paper gun, stick with the .308Win for you purposes. It is an easier round to shoot and tends to be more accurate than the short mags. You will use almost 70 grains of powder in a short mag load while in a .308 it will be around 44. That adds up to a cost savings. The steep shoulders of the short mags make for finicky feeding, some bolt guns have trouble with them so they are even more challenging for a gas gun.

If you need the smash for hunting elk or moose then give it a run, if not stick with the .308.

Not an AR10. Wrong forum.

What type of competition are you looking to get into? That will almost dictate what you can and cannot have right there. Rules and all.

And yes, its NOT an AR10.

OP- did you make any progress?

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