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6.5mm Short Action Ultra Magnum

Posted on November 14, 2013
6.5mm Remington Short Action Ultra Magnum

M118LR 7.62x51, 6.5 SAUM 130 Berger HVLD and 6.5 SAUM 139 Scenar

In the spirit of transparency I have to start by admitting this project was somewhat encouraged by alcohol. That is one of the dangers of going over to Bill’s house. You drink a few beers, then Bill pulls out a bad ass rifle for hunting season and you just have to build one too!

After my team mate Bill finished building his 6.5 SAUM, I started looking into the cartridge. I was not yet convinced it was worth building until Bill directed me toward a thread on Sniper’s Hide with more information (New GA Precision Extreme Hunter 6.5 SAUM). After a fair amount of reading and research I decided to go ahead and build one for myself.

From what I have read the 6.5mm SAUM is a very curious cartridge. The barrel life and velocity quickly interested me. It is claimed to have great barrel life for a 6.5mm cartridge. George Gardner from GA Precision estimates barrel life in the 3,000 round plus Ball Park. The cartridge will shoot a 140 grain bullet @ 3,100 fps plus from a 24” barrel. Those velocities are ascertained using 60-61 grains of H-1000. The exceptional barrel life is believed to stem from the low operating pressure of the cartridge (similar pressure levels to a .308 Winchester).

To get this project off the ground I ordered the reamer and Remington 700 short action bolt with a magnum bolt face. Sheila from Pacific Tool & Gauge was very helpful and demonstrated excellent customer service. The bolt is one piece and cut for a Sako style extractor. The reamer has a 0.298” neck so I should not have to neck turn the brass after sizing down. Others on Sniper’s Hide have mentioned I may need to neck turn a “donut” that sometimes forms on the inside of the case mouth after necking down .300 SAUM brass.

Wyoming Coyote with the 6.5 SAUM

Wyoming Coyote with the 6.5 SAUM

With the bolt and reamer ordered I went ahead and made arraignments for the barrel. I have been impressed with Benchmark barrels after cutting a few for friends and team mates. The barrels are very accurate and have gone the distance. My team mate Tyler has over 3,000 rounds on a Benchmark chambered in 6.5 Creedmoor for his Desert Tactical Arms SRS. I decided to use a Remington Varmint contour barrel with a 1-8.5” twist.

We have been very successful with the 7mm SAUM rifles we have built. We have been using long actions to build them so we would have plenty of room to feed the rounds from a magazine while utilizing 180 grain Berger Hunting VLD bullets. That combination has worked very well. I was thinking about building one on a short action and realized that would be difficult because of the restricted cartridge overall length of the magazines (2.892”). The 6.5mm SAUM on the other hand is perfect for running from a short action receiver. The 6.5 SAUM hangs with the 7mm SAUM in trajectory and deflection but gives up energy on target and maximum effective range.

Build process

Gunsmithing

Trimming the tenon

When the barrel arrived from Benchmark I wasted no time getting to work on the rifle. The first thing I did was get the action/chamber end of the barrel trued up in the lathe. I was able to dial the barrel in with less than 0.0002” of run out. Once that was done and everything was locked down I began turning down the barrel tenon to 1.062” and threaded it 16 threads per inch.

With the tenon threaded I checked my measurements. Then using a counter bore bit, I cut the bolt nose recess. Once that was finished I put the recoil lug on and screwed on the action to make sure the bolt nose cleared and that the tenon wasn’t too long. I needed to make a small adjustment because my tenon was a few thousands over. After correcting that I deepened the bolt nose recess the same amount. At that point I was ready to begin cutting the chamber.

6.5 SAUM Finishing Reamer

6.5 SAUM Finishing Reamer

The chamber is the slowest part of the process and because we do not have a positive flow lubrication system I had to stop often and clear away the debris to ensure I didn’t roll a chip. The chamber cut without incident and once I set the head space I was just about done with that end of the barrel. The only thing I did different with the 6.5 SAUM versus other rifles I have build was give it a very health chamfer on the bolt nose recess and entrance into the chamber. I cut the chamfer at a 54 degree angle to help those rebated cases skip into the chamber from the magazine.

I wasn’t able to complete the rifle until the following Monday. By that time I had decided I was going to cut the barrel to 27” from the front of the recoil lug to the crown. Before I dialed in the muzzle end of the barrel in the lathe I torque the action and lug onto the barrel using 60 foot pounds. I then check my head space with the gauges. With that complete I went to work on the muzzle end by cutting off 2” and getting it in the lathe nice and straight. Once everything was set up I turned the muzzle down to 0.62” and threaded it 24 threads per inch (5/8×24 tpi). After cutting the threads on the muzzle I had to make a couple adjustments so the brake would clock properly, once that was sorted out I finished everything off by cutting an 11 degree target crown.

Now that the barreled action was built it was time for some cosmetic work. I set up to have the action, barrel, and base Cerakoted in Field Dark Earth and the PTG bolt will be finished in matte black Cerakote.

6.5 SAUM/ Mirage ULR chassis

6.5 SAUM/ Mirage ULR chassis

Rifle parts/specs

-6.5 SAUM (0.298” neck 0.081” free bore)
-24” Benchmark 1-8.5” twist Remington Varmint contour
-11 degree target crown
-Muzzle 5/8”x24 tpi (Cerakote FDE)
-POF muzzle brake (Black)
-Remington 700 short action (Cerakote FDE)
-PTG 1 piece bolt, magnum bolt face (Cerakote Black)
-Sako extractor
-PTG “high speed” firing pin assembly (Black)
-D.D. Ross bolt knob (Black)
-E.G.W. 20 MOA base (Cerakote FDE)
-Mirage ULR short action chassis
-US Optics LR-17  3.2-17x44mm
-Badger Ordnance 30mm low rings (0.823”)
-Badger Ordnance Angle Cosine Indicator mount
-Sniper Tools Angle Cosine Indicator
-Jewell HVR trigger
-Accurage Mag .300 WSM magazine

6.5mm Remington Short Action Ultra Magnum

6.5mm SAUM

 

Forming brass

On the reloading front I was able to secure 200 pieces of .300 SAUM brass and 8 pounds of H1000. My fingers are crossed 7mm SAUM brass is on the horizon because it would be easier to neck them down, but I will work with what I have. Since this rifle is going to be used for long range shooting and hunting I wanted a bullet that could do both. I decided on using the Berger 140 grain Hunting VLD. The Hunting VLD has proven to be an accurate long range bullet and very effective on game.

I ordered the Redding 6.5-.300 SAUM full length resizing die and bullet seating die from MidwayUSA. This is a custom/special order so the wait is very long, it is estimated I will receive the die set in January 2014. I also ordered a set of Hornady custom grade 7mm SAUM dies to help step the brass down from 0.308” to 0.284” and finally 0.264”. While I am waiting for my 6.5 SAUM dies I will have to head over to Bill’s and use his dies.

Bill has been using brass from Copper Creek, it comes neck turned and ready to go. You can also purchase loaded ammo from them. Bill also experimented will different ways to form 6.5mm SAUM brass. He was looking for a way to easily make brass from .300 Remington Short Action Ultra Magnum. When I finished my rifle, I used the same process (actually formed and loaded them at Bill’s house) to load rounds.

Forming 6.5 SAUM brass

Forming 6.5 SAUM brass

1. Run .300 SAUM brass through a full length 7mm SAUM die with the mandrel removed.
2. Run .300 SAUM brass through a full length 6.5mm SAUM die with the mandrel.
3. Run .300 SAUM brass through a 6.5mm neck resize die with the mandrel removed.
(Bill’s dies set up in his Dillon 550B really made forming the brass quick and easy)

With the brass necked down from 7.62mm to 6.5mm you end up with a couple defects. On the inside of the case mouth a “donut” forms, you will see a small amount of raised material if you look closely. On the outside of the case if you look closely or measure with your micrometer you will find that a “bell” has formed on the tip of the neck/case mouth. Instead of trimming the case length, inside neck turning and outside neck turning to make the brass pretty and perfect Bill set his Giraud trimmer to remove both imperfections. By doing this we save ourselves a lot of time, the Giraud trimmer removes the inside donut and outside bell while chamfering the inside and outside of the case mouth. Since we removed 0.040” of the neck, once the brass is fired, resized and reloaded we will not trim it. After resizing we will just chamfer the inside and outside of the case mouths letting the neck grow. Once the case overall length exceeds 2.0” it will be trimmed back to 2.0”. The neck tension on the bullet from our formed brass is substantially more than normal and will effect accuracy. We hope that when 7mm SAUM brass is available we can revisit making no neck turn brass.

While making brass we use a lot of resizing wax to allow the brass too easily to pass in and out of each die.  Sometimes a dimple or ripple may form on the case shoulder. Don’t worry about how it looks, once you fire the round, the case will be formed to your chamber. Even though the case head has .300 SA Ultra Mag written on it you most definitely have perfect 6.5mm SAUM brass! Even firing the rounds with dimpled shoulders accuracy was good. My three, three round groups using a Berger 130 Hunting VLD, Nosler 7mm SAUM brass with 63 grains of H1000 yielded an average of 0.6 MOA at 100 yards. That is very acceptable for a hunting rifle but if you really want to gain the full accuracy potential of this cartridge you will want to neck turn your brass. Neck turning the brass will yield much more consistent neck tension and allow for those bug hole 5 round groups we all love.

6.5mm SAUM load

6.5 SAUM 130 Berger HVLD

6.5 SAUM 130 Berger HVLD

140 Berger Hunting VLD
61.3 grains H1000
Tulammo LR primer
Remington .300 SAUM brass necked down to 6.5mm SAUM
COAL 2.825”
Velocity- 3,150 fps *estimated

130 Berger Hunting VLD
63 grains H1000
Tulammo LR primer
.300 SAUM brass necked down and neck turned to 6.5mm SAUM
COAL 2.825″
Velocity- 3,250 fps (with 24″ barrel)

Shooting

The 6.5 SAUM is a hammer! Bill 130 Berger Hunting VLD load shoots sub 0.5 MOA at 100 yards (5 rounds). At 1000 yards the projectile still impacts with over 1,000 foot pounds of energy and gets there with less than 6 mrad of elevation!

While shooting the rifle the recoil is very manageable. The R&D muzzle brake does a good job keeping everything nice and tame. I have noticed the 6.5 SAUM has a longer recoil pulse verse my 6.5 Creedmoor which makes sense because the SAUM has an extra 18.4 grains of powder. The barrel also heats up pretty quickly and when the barrel is hot my rounds will begin to impact low. My 6.5 Creedmoor also does this during rapid/long strings of fire. I have identified this during practice while running the Sniper’s Hide competition dot drill.

I decided to put the 6.5 SAUM in my Mirage ULR short action chassis. This chassis is light and solid, I really like the way it feels. While lying prone supported with the rifle I feel very stable. The Mirage ULR chassis is recessed and the barreled action actually drops into it about 0.5”. This lowers the center line of the rifle and aids in stability. The Mirage chassis is on the light side at 4.5 lbs and helps keep the total weight of the rifle down. This is especially welcomed because I plan and backing the rifle into some pretty rough country here in Nevada.

6.5mm Remington Short Action Ultra Magnum

6.5 SAUM, US Optics LR-17, Mirage ULR chassis

The 6.5 SAUM is a great all around cartridge for hunting and long range shooting. It can easily be run in a short action and the high ballistic coefficient and velocity of the projectiles make for a very flat shooting and hard hitting round. The BC and velocity also allow the projectile to fight deflection caused by wind. What that does is give you a greater margin of error while harvesting animals or shooting targets. If you make a windage or ranging error you still have a good probability of scoring a hit because of the impressive performance of the cartridge. We all know that performance comes at a cost and in this case we would assume a barrel life of 1,400-1,600 rounds. My fingers are crossed the barrel will make it to 2,000 rounds. I would be very happy with the barrel life and performance at that point. Now if George is correct and I can get close to 3,000 rounds on the barrel without setting it back then that would be a god send!

I’m not willing to bet the farm that the 6.5 SAUM will go 3,000 rounds but my fingers are crossed. I have read reports from George that he has a 6.5 SAUM that was set back around 2,000 rounds and it made it to 4,045 rounds! Bryan Yeung another team GAP shooter has a barrel that went 3,000 rounds, so the prognosis is good.

Hunting

Bill with his Wyoming Bull Elk

Bill with his freshly harvested Wyoming Bull Elk

My friend Bill is the first of draw blood with his 6.5 SAUM. He headed to Wyoming this season and harvested a bull elk and coyote. Bill will also be hunting mule deer here in Nevada later this fall.

Bill harvested his elk at “320 yards, he was heading up the hill away from me so my point of aim was his backbone. The first round hit him in the spine, but further back than I intended, that stopped him. Then the second round hit him point of aim point of impact, in the top of the back right behind the shoulders. That dropped him. He did get back up and made a few steps before tumbling down the hill (steep as shit). We didn’t gut him the first day because we didn’t have time to get it out of there that afternoon and we were trying to keep the “odors” to a minimum so the bears wouldn’t get to it before we can get back out there. The bears still got to it, but they just ate the guts out of it and the underside of the elk which is where my exit wound would have been if there was one. I wasn’t able to see any of that, but the entrance wounds were evident. One right in the spine just in front of rear quarters (when he was on the move) and one about an inch right of the spine right behind the shoulders, the fatal shot. He didn’t go 20 yards from the spot I first shot him to where he tumbled down the hill after the second shot.”

Wyoming Elk Hunt

Wyoming Elk Hunt

6.5 SAUM Remington 700 long action

6.5 SAUM Remington 700 long action

6.5 SAUM

6.5mm SAUM

6.5mm SAUM

Night time is the right time!

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