7mm Remington SAUM

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12 years 7 months ago #11202 by mts
7mm Remington SAUM was created by mts
Is anybody here shooting AR-10s in this caliber? The 7 RSAUM works well in the Armalite magazines for 5 rounds in a standard 20 rd. magazine, and its ballistics are better than .308. There are two of us here in the sticks with rifles chambered for the 7 RSAUM and we are having a fine time working up loads.

24" heavy barrel seems to like 175 and 180 gr. bullets especially the Berger VLD #28405. Powders that work well are Ramshot Magnum, VV N560, and Win 760 Supreme all at around 2800 fps.

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12 years 7 months ago #11215 by AR260rem
Replied by AR260rem on topic Re: 7mm Remington SAUM
No, but sounds interesting! I like different and under-appreciated calibers. Thought about the 300 SAUM AR-10 but haven't jumped on one yet. I've never seen one in 7 SAUM. Might keep my eyes open for one.

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12 years 7 months ago #11250 by mts
Replied by mts on topic Re: 7mm Remington SAUM
You probably won't find one on the shelf anywhere. Two uppers with 24" barrels were built on custom order by Accuracy, Inc. in Colorado. Finding long gas tubes is near impossible since Armalite completed a military contract and sold out their extras. The standard tube isn't appropriate for longer barrels. I would have liked 26" barrel length (would have had to cut a hole in my drag bag), but that wasn't considered possible with the gas tubes that are available.

The 7-mm choice was made because there are excellent bullet choices available with generally superior BC to the .308. The .308 is the choice that was made by the military probably because it's more or less a standard caliber for them. The big stuff like .338 Federal and Lapua is tough to get into the AR-10 frame profile. I wanted to stick with a standard Armalite AR-10 match lower.

The downside has proven to be absolutely lousy 7 mm factory ammo. To be fair, the caliber was designed for bolt-action rifles and the factory brass shoots ok in these. I have most of a box sitting on the shelf that isn't worth the trouble to shoot.

Remington brass is generally bad with at least 10-15% of any lot having loose primer pockets. Nosler brass in .300 RSAUM is good when resized to 7-mm, but is of course expensive. Once you discard the bad brass from a Remington lot there isn't much difference in price. The good news is that ten or more reloads are possible for each cartridge bringing the brass cost per round more resonable.

What is interesting is that the SAAMI spec for the caliber is 2.035" for brass length but the Nosler measures 2.005 out of its fancy box. Remington brass from their cheap plastic bag is closer to specification measuring 2.027-2.035.

The lighter bullets have not performed well for me, but the 162 Hornaday AMax seems to be a good choice probably out to 600 yds. The Berger 180 VLDs are definitely the long-range choice, but I just got a box of the Sierra 180 MK to try. The AR-10 magazine limits OAL to 2.825, or a little less in practice which means that you cannot always set the jump to an optimum value especially for a VLD bullet.

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12 years 7 months ago #11293 by AR260rem
Replied by AR260rem on topic Re: 7mm Remington SAUM
That's too bad. I did find a company, Accuracy Systems Inc in Colorado that makes some very interesting uppers. I was thinking about a 6.5x284 setup. I chose the .260 Rem AR-10T for the much better B.C. bullets over the 308 as well.

Thanks for the info!

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