Of the six 257 I and my friends own: we all shoot the 115 Berger. One rifle uses H1000, Five use RL-25 and mine uses RL-33.
I was just at the range yesterday verifying a new lot (8 lb) of RL-33 and my friend was using a new lot of RL-25. We wanted to find out which powder charge weight would duplicate the previous loads. Turns out both powders had no variance in performance with same charge weights.
The RL-33 beat RL-25 by 85 fps. The rifle with RL-33 is 1 1/2" longer (27 1/2" vs 26") which may account for some of this difference. Otherwise the two rifles use the same 3 groove Lilja, moly coated 115 bergers, same seating depth, reamer, primer, and brass.
I hesitate to show the actual load data because it these rifles are the same rifle that one would get with a "regular" 257 Weatherby.
Why? Custom reamer with different throat angle and less freebore, 3 groove barrels, minimal bearing surface VLD and moly coating.
Nosler shows a max load with a 115 bt as 72 gr of RL-25. The rifle shot yesterday used 74.5 grs for velocity of 3600 fps
RL-33 load is 83 grs for velocity of 3685 fps.
For load data with RL-33, I have found that in many cartridges I could start RL-33 with the max data for Retumbo and go up from there.
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RL-33 seems to work best with the heaviest bullets for that caliber.
Posted this before when the powder first came out. :
There is little data to on RL-33 reference at this point. Determined by comparisons and now by testing that RL-33 is slower than Retumbo for the 7 Rem Mag, 257 weatherby and 6mm-284.
With all three rifles didn't make any changes other than switching powder. Used the same brass, primers, bullets, seating depth, neck tension etc.
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The loads below are worked up carefully in my rifles. Your results may vary. Please work up carefully.
7 Rem Mag: 24" Rem barrel, moly coated 162 A-max seated .010" into rifling.
Original load: 72 gr of Retumbo 2975 fps
RL-33:
starting load 76 gr vel 2837
Unfortunately the chrono had to be adjusted, shot without it till they had a ceasefire.
worked up to 79 gr for vel of 3000 for very small gain over Retumbo
80 grs showed a hint of lift and a small shiny spot on casehead.
I used a bullet seating comparitor and noticed that even with the use of a drop tube the powder was filling the case. 79 gr and up caused the OAL to lengthen over .010", enough so the bullet wouldn't fit into magazine.
I can see why Alliant only mentioned a load for the 175 gr bullet.
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An earlier barrel on my 257 Weatherby (now retired): 28" #5 fluted SS Lilja 3 groove barrel, moly coated 110 accubond, .015" off rifling.
Original load 75.5 gr of RL-25 vel 3615 fps
RL-33
starting load 76 gr for vel of 3318
jumped to 80 gr 3432 fps
81 gr 3525
82 gr 3559
83 3625 which slightly faster than old load with RL-25
83.5 3674 fps shot well two shots were same velocity
84 gr 3704 fps shot well two shots were same velocity
84.5 gr 3735 slight signs of pressure on one case of four this is max case capacity with drop tube
This makes a 91 fps gain over a max load of RL-25
No signs of pressure what so ever.
6mm-284: 28" SS Bartlein 5R barrel 1 in 7.5 twist
Original load: 58 gr of Retumbo, 105 Berger target hybrid seated .065" off rifling (to feed from magazine) vel 3307 fps
RL-33:
starting load 58 gr vel 3074
jumped to 61 grs vel 3274
62 grs vel 3335
62.5 gr 3376
63 gr 3414
63.5 gr 3453
64 gr 3485 fps excellent accuracy (used this load)
64.5 gr 3535 a bit warm max case capacity using drop tube
Old velocity with Retumbo was 3307 which was the highest charge of powder without pressure issues. RL-33 yielded a 178 fps increase!