Over the years, I have probably chronographed more than 10,000 muzzle-loaded rounds through an extreme range of different modern and traditional muzzleloading rifles. And I've recorded velocities in a wide range of weather and temperatures extremes, and at elevations ranging from 16 feet above ses level to higher than 8,000 feet. Out of the same rifle with the exact same loading, I've seen variations in velocity as extreme as 100 f.p.s., even though during the testing at such extremes my velocity spreads may have stayed within 15 f.p.s.
Of all the variable that can and will have an effect on muzzleloader velocities, the No. 1 factor for me has been the temperature. A rifle and load will not shoot the same when it's 20-degrees and when it's 90 degrees outside. My finding has been that wtih colder temepratures, velocities tend to be 30 to 50 f.p.s. faster than when it's hot and sultry, especially when shooting with plastic saboted bullets. And for that reason, I now try to do most all of my chrony shooting when temperatures are between 30 and 50 degrees. That's also when I most commonly shoot my best groups as well, and that' probably due to the fact that I experience less deviation from standard velocity when shooting in that temperature range.
I have found that Blackhorn 209, being a nitrocellulose based powder, is less affected by high humidity levels as carbon based muzzleloader propellants. But other factors can still affect the velocities achieved, and that is evidenced right in the ballistics that Blackhorn 209 provides for the powder. For instance, their data gives velocities for 6 different saboted 300-grain bullets - and with a 100-grain charge the velocities given range from 1,813 f.p.s. on the slow side to 1,925 on the fast side. Likewise, I've seen the data shot by others, and have seen a similar spread. Like I've said, I have experienced it too. Making it work is to strive for as narrow a velocity spread as possible - at the time of year and temperature when you are shooting.
Following are some of my favored sabot and bullet combos. These velocities were shot in late fall/early winter - in the same temperatures I usually experience when hunting. All of these loads have proven capable of keeping three-shot 100-yard groups right around an inch - often inside of an inch.
ALL TESTING DONE WITH 27" BARRELED KNIGHT .50 "LONG RANGE HUNTER"
Bullet: 250-Gr. Knight Polymer-Tipped .451" Spire-Point (Barnes all copper)
Sabot: Barnes .50x.45 (Yellow) For Boat-Tail Bullet
90 grains...1,916 f.p.s./2,037 f.p.e.
100 grains...1,991 f.p.s./2,200 f.p.e.
110 grains...2,053 f.p.s./2,338 f.p.e.
Bullet: Harvester Muzzleloading 260-Gr. .451" "Scorpion PT Gold" Spire Point
Sabot: Harvester Muzzleloading .50x.45 "Crush Rib" Sabot
90 grains...1,904 f.p.s./2,090 f.p.e.
100 grains...1,968 f.p.s./2,236 f.p.e.
110 grains...2,039 f.p.s./2,401 f.p.e.
Bullet: 290 Gr. Knight Polymer-Tipped .451" Spire-Point (Barnes all copper)
SAbot: Barnes .50x.45 (Yellow) For Boat-Tail Bullet
90 grains...1,836 f.p.s./2,166 f.p.e.
100 grains...1,929 f.p.s./2,398 f.p.e.
110 grains...1,976 f.p.s./2,511 f.p.e.
Bullet: Harvester Muzzleloading 300-GR. .451" "Scorpion PT Gold" Spire Point
Sabot: Harvester Muzzleloading .50x.45 "Crush Rib" Sabot
90 grains...1,823 f.p.s./2,211 f.p.e.
100 grains...1,918 f.p.s./2,451 f.p.e.
110 grains...1,961 f.p.s./2,560 f.p.e.
When testing a few recent rifle models, I have shot with 130- and 140-grain charges, but have settled on the following load as my favored deer/elk/bear load for the two Knight rifles I shoot and hunt with most - the .50 caliber "Long Range Hunter" and the new "Moutnaineer". (The latter is a protoype that I've shot for the past year.) Both have 27 inch Green Mountain barrels.
Bullet: Harvester Muzzleloading 300-GR. .451" "Scorpion PT Gold" Spire Point
Sabot: Harvester Muzzleloading .50x.45 "Crush Rib" Sabot
120 grains...2,063 f.p.s./2,832 f.p.e.
This load, with temperatures averaging around 40-degrees, is still flying at around 1,500 f.p.s. at 200 yards, and the 300-grain bullet hits with right at 1,500 f.p.e. Typically, I can keep three shot groups between 2 1/2 and 3 inches at that distance, but I have poked a couple inside of 2 inches. Drop from 100 to 200 yards is just a fraction over 9 inches. The buck in the above photo was taken at 186 yards...and went less than 20 yards after taking the 300-grain "Scorpion PT Gold" squarely through the chest. - Toby Bridges
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