DISCLAIMER: This is a guide. Everything listed within is for information purposes only. All loads should be worked up carefully. We have seen significant pressure and velocity differences between powder lots, brass manufacturers and chamber configurations. The 6.5 SAUM is not a SAAMI-standardized cartridge. Failure to start low and carefully work up a load for your individual rifle could result in damaged equipment or injury. USE AT YOUR OWN RISK.
The 6.5 SAUM is a high-performance 6.5mm cartridge based on the Remington Short Action Ultra Magnum case. In its simplest form, it is the 7mm SAUM necked down to accept .264-inch bullets. It is also commonly known as the 6.5 GAP 4S, a version of the cartridge made popular by George Gardner and GA Precision.
The cartridge gained a strong following among long-range shooters because it offered considerably more velocity than cartridges such as the 6.5 Creedmoor while remaining in a relatively short and efficient case. With modern high-BC bullets, the 6.5 SAUM remains one of the highest-performing practical 6.5mm cartridges available to the handloader.
The 6.5 SAUM was never standardized by SAAMI. That is an important distinction and one of the main subjects covered in this guide. There are several chamber configurations, neck dimensions and freebore lengths in use, and those differences can substantially affect pressure, velocity and cartridge overall length.
6.5 SAUM History
The 6.5 SAUM began as a wildcat based on the 7mm Remington Short Action Ultra Magnum case necked down to 6.5mm. The basic idea was straightforward: combine the efficient SAUM case design with the excellent ballistic coefficients available from modern 6.5mm bullets.
George Gardner of GA Precision helped make the cartridge widely known through his use of the 6.5 SAUM in long-range competition and through rifles produced by GA Precision. The GA Precision version became known as the 6.5 GAP 4S.
Over time, brass became available with the 6.5 GAP 4S headstamp, eliminating much of the case-forming work that was originally required.
The success of the 6.5 SAUM also demonstrated the demand for a high-performance 6.5mm cartridge in this general case-capacity range. The later introduction of the standardized 6.5 PRC gave shooters a similar concept with widespread factory support.
The 6.5 PRC eventually became the more commercially successful cartridge, but the 6.5 SAUM still offers slightly greater case capacity and remains an excellent choice for the experienced handloader.
6.5 SAUM Versus 6.5 PRC
The obvious comparison is the 6.5 PRC. Both cartridges were designed around the same basic goal: push high-BC 6.5mm bullets substantially faster than the 6.5 Creedmoor without moving all the way to the much larger .264 Winchester Magnum class.
The 6.5 SAUM has more case capacity than the 6.5 PRC and, all else being equal, generally has somewhat greater velocity potential. That does not automatically make it the better cartridge.
The 6.5 PRC has several important advantages:
- SAAMI-standardized chamber dimensions
- Factory ammunition
- Factory rifles
- Widely available properly headstamped brass
- Broad die and component support
- More predictable chamber and magazine dimensions
The SAUM’s advantages are primarily of interest to the custom-rifle builder and experienced handloader. Its additional capacity provides more flexibility with heavy bullets and slow powders, and the lack of standardization also allows the rifle builder to tailor freebore and cartridge length specifically around the intended bullet.
If I were recommending a cartridge to someone who wanted to buy a rifle, purchase ammunition and go hunting, the 6.5 PRC would be the easy recommendation.
If I were building a dedicated custom rifle, planned to handload everything I shot, and wanted to extract the most performance I reasonably could from this size of 6.5mm cartridge, the 6.5 SAUM would still deserve serious consideration.
Chamber And Freebore
This is probably the most important thing to understand about the 6.5 SAUM. There is no single SAAMI 6.5 SAUM chamber.
Different reamers have been produced with different neck diameters and substantially different amounts of freebore. The rifles represented in our Long Range Only data collection included freebores ranging from approximately .081 inch to .188 inch.
Shorter-throat versions were developed around shorter magazine lengths and the 130- to 140-grain bullets that were popular when the cartridge first became established. Longer freebore versions allow modern heavy 6.5mm bullets to be seated farther out of the case, preserving powder capacity and providing additional flexibility with cartridge overall length.
This means a load that is perfectly reasonable in one 6.5 SAUM chamber may produce significantly different pressure in another.
Before beginning load development, know the following:
- Chamber neck diameter
- Freebore
- Maximum cartridge overall length to the lands with the intended bullet
- Magazine-length limitation
- Loaded-round neck diameter
- Brass manufacturer
This is not a cartridge where I would blindly duplicate someone else’s powder charge simply because the barrel length and bullet happen to be the same.
Action Length
The name Short Action Ultra Magnum would suggest that the obvious home for the cartridge is a short action. It can certainly work very well in one.
But whether a short action is the best choice depends largely on the bullet you plan to use. With 130- to 140-grain bullets and an appropriately designed chamber, a short action can make an extremely compact and efficient rifle.
As bullets become longer, particularly in the 147- to 156-grain range, magazine length becomes increasingly important. Seating a long bullet deeper into the case reduces usable powder capacity and may prevent the handloader from taking full advantage of the cartridge.
For that reason, several successful 6.5 SAUM rifles have been built on medium or long actions even though the cartridge case itself is short enough for a traditional short action.
If I were building specifically around the Berger 156 EOL or another similarly long bullet, I would want enough magazine and action length to seat the bullet where the chamber wants it rather than designing the entire load around an arbitrary short-action magazine limitation. A modern medium-length action may be the best compromise.
Brass
Brass availability was historically one of the largest disadvantages of the 6.5 SAUM. Before properly headstamped brass became readily available, shooters commonly formed cases from 7mm SAUM or .300 SAUM brass.
That process may include:
- Necking the case down
- Annealing
- Expanding or mandrel sizing
- Neck turning
- Final sizing
- Checking loaded neck diameter against the chamber
The Long Range Only data collected for this cartridge includes brass from several sources, including ADG, Bertram, Norma, Remington and Hornady/GAP.
The important point is that case capacity can vary considerably between manufacturers. That can directly affect pressure. A load developed in one brand of brass should not automatically be transferred to another brand at the same charge weight.
Bullet Selection
The 6.5 SAUM works with a broad range of 6.5mm bullets, but the cartridge really begins to separate itself from smaller 6.5 cartridges with bullets in roughly the 140- to 156-grain range.
120- to 130-Grain Bullets
Light bullets can be driven extremely fast. Our collected data includes 122- and 124-grain monolithic bullets at approximately 3200 fps and beyond, even from relatively short barrels.
That can make an excellent combination for deer and antelope where the shooter wants a very flat trajectory and a tougher bullet construction. At the same time, muzzle velocity alone should not determine bullet choice. Very light monolithic bullets can produce excellent close-range penetration, but the hunter should still evaluate the bullet’s minimum expansion velocity before using it at extended range.
140-Grain Class
The traditional 140-grain class may be the most balanced bullet weight for the cartridge. The SAUM has enough capacity to push these bullets comfortably above 3000 fps in many rifles while maintaining excellent ballistic coefficients.
The Berger 140 Hybrid and similar bullets have produced very good accuracy and velocity in several SAUM configurations. This bullet weight also works particularly well when trying to retain a relatively compact rifle and shorter cartridge overall length.
147-Grain Class
The 147-grain Hornady ELD-M has proven to be an excellent match for the cartridge. Our collected data includes 147 ELD-M loads in the neighborhood of 3050 fps from a 24-inch barrel with excellent accuracy and very low extreme spread.
153- to 156-Grain Bullets
The heavy 6.5mm bullets are where the SAUM becomes especially interesting as a long-range hunting cartridge. The Berger 156 EOL is one of the bullets that can take full advantage of the SAUM’s additional capacity over the 6.5 PRC.
Depending on barrel length, freebore and powder, our collected data suggests approximately 2800 to 2950 fps is realistic from 22- to 25-inch barrels.
Powder Selection
The 6.5 SAUM generally performs best with slower-burning rifle powders, particularly as bullet weight increases. Based on our collected data, several powders stand out.
H1000
H1000 may be the most universally useful powder represented in the SAUM data. It has produced successful loads with bullets ranging from the 139-grain class through the Berger 156. It also has a long-standing reputation for good temperature stability.
RL26
RL26 can produce outstanding velocity in the 6.5 SAUM. It performed particularly well with 140- and 147-grain bullets in the data we collected. Several rifles produced excellent accuracy and velocity with RL26, but availability has often been inconsistent.
Vihtavuori N565
N565 falls into an excellent burn-rate range for this cartridge and is particularly interesting with heavier bullets. It provides good case fill and has produced strong velocity in several high-performance 6.5mm cartridges.
Retumbo / AR2225
Retumbo is slower and becomes increasingly useful as bullet weight and usable case volume increase. Our collected data shows very good performance with the 156 Berger.
H4350
H4350 is considerably faster than the powders I would normally select for heavy bullets in the SAUM, but it can work very well with lighter projectiles. A 124-grain Hammer load in our data produced approximately 3185 fps from a 22-inch barrel with excellent accuracy potential.
Primer Selection
Both standard and magnum large rifle primers have been used successfully in the 6.5 SAUM. Our collected loads include:
- Federal 210M
- Federal 215M
- CCI BR-2
- CCI 250
- Winchester Large Rifle
I do not consider the cartridge to absolutely require a magnum primer. Primer selection should simply be treated as part of the load-development process.
Barrel Length
The 6.5 SAUM does not require an extremely long barrel to perform well. The rifles represented in our data ranged from approximately 20 to 27 inches.
One particularly useful example involved the same rifle and 139-grain load before and after the barrel was shortened. Velocity was approximately 3070 fps from a 24-inch barrel and 2990 fps from a 20-inch barrel.
That particular rifle lost roughly 80 fps when four inches of barrel were removed. I would not use that as a universal velocity-per-inch rule, but it does show that the SAUM maintains very respectable performance from shorter hunting barrels.
For a modern hunting rifle, especially one intended to be suppressed, I think 22 to 24 inches is a very attractive range.
Twist Rate
For 140-grain-class bullets, traditional 1:8 twists have worked very well. For a new rifle intended to shoot the Berger 156 EOL and other long modern bullets, I would lean toward approximately a 1:7.5 twist.
Expected Performance
Every rifle is different, especially with a non-standardized cartridge, but the data collected by Long Range Only gives us useful general expectations.
These should not be treated as load-development targets. They are simply representative of what properly configured rifles have produced. Chamber dimensions, barrel length, brass capacity, powder lot and pressure can move these numbers significantly.
Representative Load Data
The following loads are included only to show combinations that have produced good results in actual rifles. They are not starting loads. Reduce charges and work carefully toward any load in your individual rifle.
These are representative loads from individual rifles, not starting loads. Reduce charges and work up carefully in your rifle. Chamber, freebore, brass, powder lot, seating depth and barrel differences can materially change pressure.
Accuracy
The 6.5 SAUM has developed a reputation for excellent accuracy, and the data submitted to Long Range Only supports that reputation. Several rifles in the collection repeatedly produced groups in the .3- to .5-MOA range with developed handloads.
More importantly, some of the data included extended-range testing rather than only single three-shot groups at 100 yards. For a long-range hunting rifle, I am far more interested in a load that repeatedly performs at distance than one impressive group fired once at 100 yards.
Hunting Performance
The collected Long Range Only data includes successful use on deer, antelope and elk. As always, bullet selection matters more than the cartridge name.
The SAUM produces substantial muzzle velocity, so the bullet needs to perform correctly both at close-range impact speeds and at the lower impact velocities encountered at extended range.
The 140- to 156-grain lead-core bullets offer a very broad performance envelope and are where I think the SAUM is most compelling for long-range hunting.
Brass Life And Pressure
The data collected from SAUM shooters shows good brass life is certainly possible, but it also contains several examples where pressure became noticeable as loads approached the upper end.
Ejector marks, sticky bolt lift and loosening primer pockets should never be dismissed simply because another shooter is using the same powder charge.
The 6.5 SAUM rewards careful load development. It also punishes the handloader who becomes fixated on achieving a specific advertised velocity.
A barrel may speed up as it breaks in. A new powder lot may produce more pressure. A different brass manufacturer may have less internal capacity. Temperature can change pressure. If a previously safe load begins showing pressure, back it down.
Reloading Dies
Because the 6.5 SAUM remains a wildcat, die selection deserves more attention than it does with a standardized cartridge. A quality full-length sizing die and micrometer seating die are my preference.
Bushing dies can also work very well, particularly when neck-turned brass is being used. Before selecting bushings, determine actual loaded neck diameter with your brass and bullet combination.
Advantages Of The 6.5 SAUM
- Excellent velocity with high-BC 6.5mm bullets
- More capacity than the 6.5 PRC
- Excellent long-range external ballistics
- Very good accuracy potential
- Works with a broad range of bullet weights
- Can be configured around short, medium or long actions
- Performs well from relatively moderate barrel lengths
- Excellent choice for the experienced handloader building a custom rifle
Disadvantages Of The 6.5 SAUM
- No SAAMI standard
- Multiple chamber and freebore configurations
- Primarily a handloading proposition
- Limited factory ammunition compared with the 6.5 PRC
- Brass availability has historically varied
- Case forming may still be required depending on components
- Magazine length can become limiting with heavy bullets
- Load data must be interpreted carefully because chamber dimensions vary
Conclusion
The 6.5 SAUM was one of the cartridges that demonstrated just how much performance could be extracted from modern high-BC 6.5mm bullets in a relatively compact case.
The arrival of the 6.5 PRC did not make the SAUM obsolete. It simply gave most shooters an easier path to similar performance.
For someone who wants factory ammunition, standardized chambers and broad commercial support, I would recommend the 6.5 PRC.
For the experienced handloader building a custom rifle and willing to pay close attention to chamber dimensions, brass capacity and cartridge overall length, the 6.5 SAUM can offer a little more flexibility and a little more performance.
I would especially consider it for a rifle built around the modern 140- to 156-grain bullets.
The key is understanding that 6.5 SAUM does not describe one universally standardized chamber. Know your reamer. Know your freebore. Know your brass. Build the magazine and action around the bullet you intend to shoot. Then develop the load for that rifle rather than chasing somebody else’s velocity.
Do that, and the 6.5 SAUM remains an outstanding long-range hunting cartridge.
