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New Temperature-Stable Reloder TS 15.5 Powder for Precision Rifles

Ideal for 6mm wildcat cartridges, the new Reloder TS 15.5 splits the difference between Reloder 15 and 16 and is reliable in extremely hot and cold climates.

New Temperature-Stable Reloder TS 15.5 Powder for Precision Rifles

New Temperature-Stable Reloder TS 15.5 Powder for Precision Rifles (RifleShooter Photo)

This space-age new propellant has a burn rate between that of Reloder 15 and Reloder 16, and it was engineered to provide excellent consistency and stability across a broad range of temperatures. Temp stability—which the “TS” portion of the TS 15.5 denotes—is a characteristic that’s grown from valued to vital in the eyes of modern long-range competitive shooters. It’s a characteristic that enables a propellant to produce similar velocities whether shooting in 105 degrees in Arizona or Nevada or in freezing temps in Wyoming or Montana.

Until recently, there were only a couple of players on the scene. First was Hodgdon, with its groundbreaking line of Extreme powders. Unfortunately, the plant in which it was produced suffered a catastrophic plant fire some years back, and it’s been in short supply for years. IMR stepped up five or six years ago and introduced its Enduron line of powders. Not only are these temp-stable, they feature an element that breaks down copper, so rifle bores tend to build up less fouling, making them easier to clean. Enduron is more consistently available than Hodgdon powders, but competitive shooters loyal to Hodgdon have been somewhat slow to adopt the Enduron options.

And more recently, Winchester’s StaBall 6.5 made its debut, and it was the subject of last issue’s column. This powder not only is temp-stable but also meters very consistently. Until a couple of years ago, Alliant powders were mostly valued for their good accuracy and top velocities. However, the traditional Reloder numbers such as RL 15, RL 19 and RL 22 are not even sort of temperature stable, and long-range competitive shooters rarely give them a second glance.

Then, Alliant introduced RL 16 and RL 26. The first is outstanding in the 6mm Creedmoor, and the latter is a go-to powder for the popular .300 PRC. Importantly, both closed the gap on temperature stability and were consistent enough. Nearly.

New Reloder TS 15.5

Reloder TS 15.5 Best Group
In a custom 6.5 Creedmoor, TS 15.5 delivered excellent accuracy, low standard deviation and little change in velocity from cold ammo to hot.

This brings us to Reloder TS 15.5. Sporting a burn rate that is optimal for the 6mm wildcats prevalent on the PRS circuit—cartridges like 6mm BR, 6mm BRX, 6mm Dasher and 6mm GT—it is advertised to possess “world-class temperature stability.” Additionally, Reloder TS 15.5 features a de-coppering agent, much like IMR’s Enduron. Interestingly, while Reloder TS 15.5 is supposed to produce top velocities in the aforementioned 6mm wildcat cartridges, according to one Alliant spokesperson, the company is not going to publish pressure-tested data for said cartridges. Since they are not SAAMI approved, there’s no standardized, approved pressure spec.

However, the same spokesperson suggested that since TS 15.5 is slightly slower burning than RL 15 and Varget, shooters can look to their starting loads for those powders as a safe starting point. Alliant literature suggests that Reloder TS 15.5 is ideal for heavy-bullet .308 loads, too. Perusing Alliant’s data, it’s readily apparent that the powder will push projectiles in the 180-grain weight range to near .30-06 speeds. That’s excellent velocity, and it provides some insight on the bore-to-capacity ratio that TS 15.5 is ideal for.

It’s important to note the .308 has a similar propellant capacity to bore diameter ratio to the mild 6mm wildcats mentioned earlier. So, it makes sense that TS 15.5 works well in it. However, since the 6.5 Creedmoor has a greater capacity-to-bore ratio, TS 15.5 isn’t quite as good for heavy-for-caliber projectiles in this cartridge. However, it does very well with lighter bullets in the 120- to 130-grain weight range. As you step down to the 6mm Creedmoor, the propellant capacity-to-bore ratio becomes considerably greater again, so TS 15.5 is best suited for light 6mm bullets. So much so, in fact, that Alliant has only published 6mm Creedmoor data for 75- and 90-grain projectiles.

According to published data, in 24-inch barrels, Reloder TS 15.5 produces excellent velocity with heavy-bullet .223 loads and could be ideal for the .224 Valkyrie. To put Reloder TS 15.5 through its paces, I loaded two test batches of ammo. The first was in .308 Hornady cases, capped with Federal 210 Gold Medal primers and topping 46 grains with Hornady 178-grain ELD-X bullets. With the projectiles seated to kiss the rifling of a Remington Model 700P LTR, overall length was 3.00 inches. That’s too long to feed from the magazine, so I single-fed each cartridge.

Temperature Stable

Using boiling water, I heated a cooler up to 105 degrees and ziplocked nine rounds inside in a bowl until they acclimated. I put another nine rounds into my deep freeze, which is set at 15 degrees. Ambient temperature outside was hovering in the 30s. Lying inside my sliding glass back door, with a suppressor installed, I ran the muzzle outside and, starting with the frozen ammo, fired three consecutive three-shot groups at 100 yards.

The charge of 46 grains of TS 15.5 under the 178-grain bullets was derived from recommended charge weight for 180-grain Federal Fusion bullets, which Alliant has published data for. It’s a compressed load and a max load as well. Impressively, it produced an average of 2,712 fps in the 20-inch barrel. Assuming a 24-inch barrel would produce around 60 fps more, that’s well into .30-06 territory. It’s worth noting that I found a bit of ejector swipe on a couple of my cartridge case heads. If running another test batch, I’d reduce charge weight by a grain. 
Standard deviation was 9.9 fps, which is excellent for cold-weather testing. Usually, frosty temps cause velocity spreads to open up. Group size average was 0.61 inch at 100 yards—also impressive.

After bringing the rifle fully inside to warm up, I repeated my group testing with the hot ammo. To my surprise, the 105-degree ammo actually clocked 2,697 fps, which is 15 fps slower than the frozen ammo. That’s opposite what I expected. Still, only 15 fps difference is a laudable achievement. Also impressively, standard deviation with the hot ammo was just 6.3 fps. Average group was 0.76 inch, close enough to the frozen-ammo average that it’s certainly within shooter margin of error. Intrigued, I repeated the test with a custom 6.5 Creedmoor built on a Defiance Deviant Hunter action and has a Proof Research barrel. With tuned handloads it will regularly shoot five-shot groups under 1/2 m.o.a. I opted to use Hornady’s new 130-grain CX, accepting ahead of time that I would not achieve top velocities when pushing it with TS 15.5 powder. Priming Black Hills cases with Federal 210 Gold Medal primers, I charged with 36 grains and seated the CX bullets to a 2.825-inch overall length.

For charge data, I used Alliant’s data published for the 130-grain Terminal Ascent bullet, which is a solid-shanked projectile that I figured would take the rifling much like the Hornady CX. As it turned out, I could have safely bumped the charge up a couple of grains and achieved more speed and less empty space in the cartridge case, but for a first-go-around test I wanted to stick with published data. As mentioned, I knew velocity would be decent but not impressive, because Reloder TS 15.5 is a tad fast-burning for a long, semi-heavy monometal bullet with a lot of bearing surface. Velocity was pedestrian, but accuracy was impressive. Frozen ammo clocked 2,612 fps and averaged 0.43 inch at 100 yards, with a standard deviation of 10.9 fps. Hot ammo clocked 2,630 fps—just 18 fps faster—and averaged 0.46 inch with a standard deviation of just 6.9 fps. 


With an extreme temperature spread of 90 degrees between hot and cold ammo batches, there was insignificant velocity deviation—less than 20 fps in both cases. Accuracy ranged from promising to outstanding. Standard deviations were admirably tight in the hot ammo and acceptable in the cold ammo. I think this new Reloder TS 15.5 is good stuff. It certainly does what it’s advertised to do. I saw tight standard deviations and easy accuracy in all the testing I’ve performed. If you’re a long-range precision shooter, you might find it delivers for you.


The loads shown here are safe only in the guns for which they were developed. Neither the author nor Outdoor Sportsman Group assumes any liability for accidents or injury resulting from the use or misuse of this data. Shooting reloads may void any warranty on your firearm.  

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