More coated bullet tests, all of today's loads used the same basic load as last time because we are testing the coating not the load.
First up, Hi-Tek coating with Ben's Liquid Lube
-- 155 gr. bevel base
-- WW quenched at 385 F (~15 BHN)
-- 0.360" body with 0.359" front band
-- Ben's Liquid Lube
-- 17.5 gr. WC297
-- Win mag primer
-- 1.901" COL, right at the jam point
-- 1876 fps (awful slow for this powder charge)
-- 2.46% velocity standard deviation (horrible)
-- 1.34" mean radius
20 shot composite for the Hi-Tek bullet.
The barrel was very clean after the Hi-Tek bullets, with only these few streaks 6" - 8" beyond the breach. Before and after that stretch was squeaky clean.
Next, urethane shake-n-dry with 2 coats 45/45/10. Same load as before except:
-- air-cooled WW (~11 BHN)
-- 2 coats 45/45/10
-- 1.893" COL, right at the jam point
-- 1912 fps
-- 2.07% velocity standard deviation (poor)
-- 0.89" mean radius
20 shot composite for the Urethane bullet
Light fouling after shooting the Urethane bullets, 8" - 12" beyond the breach. Before that was clean. The fact that the fouling occurs so far down the barrel suggests that it is "running out of lube."
Next, polycrylic shake-n-dry with 1 coat 45/45/10. Same load except:
-- oven treated WW (~25 BHN)
-- 1 coat 45/45/10
-- 1.854" COL, right at the jam point
-- 1970 fps
-- 1.12% velocity standard deviation (getting there)
20 shot composite for the polycrylic bullet
Light fouling after polycryclic loads, 4" from breach. This is the spot where it fouled the most with uncoated bullets. This is an improvement compared to the uncoated bullets.
After polycrylic loads, 6" from breach. This is actually worse compared to uncoated bullets.
After polycrylic loads, 8" from breach. This spot would have been perfectly clean with uncoated bullets & HVR, so this is definitely a step backwards. The fact that the polycrylic & 45/45/10 fouling gets worse further down the barrel suggests that it was "running out of lube."
Today's target. Observations, Questions, and Conclusions:
-- I nose sized all the bullets with the same setting, hoping that would result in the same jam point, but because of the 3 different hardnesses -- 11, 15, and 25 BHN -- I ended up with a different jam point for each hardness. Drats.
-- 20 shots is not enough to prove much about accuracy other than to weed out the "bad" combinations.
-- but 20 shots is enough to prove something about velocity and standard deviation.
-- the hard bullet had lower standard deviation than the soft bullet, prolly because it has more engraving resistance that helps the powder burn.
-- Hi-Tek & Ben's Liquid Lube was the cleanest by far.
-- polycrylic & 45/45/10 was the least clean.
-- both polycrylic & urethane fouled lightly 6" - 8" beyond the breach, hinting they may have been "running out of lube."
-- apparently tumble lube is enough to prevent polymer fouling, however I suspect accuracy and velocity would be more consistent with "real" lube. Even though coated bullets don't require much lube to prevent fouling, the lube may still help provide a good gas seal and minimize velocity variation.
-- the jury is still out of on hard coated bullets vs. soft coated bullets. In general, coated bullets do not seem to be very sensitive to bullet hardness.Things to Try Next Time
-- I'm still inclined to make urethane shake-n-dry my standard coating, at least until I find a better coating.
-- shootout between Ben's Liquid Lube, Rooster Jacket, and HVR