Home Forums Reloading Big Game Rifles 300 Weatherby and Retumbo

Doing load development and need max load for 300 Weatherby using Retumbo Powder on 180gr for both Accubond and BTip's. Using Weatherby cases in a Weatherby Mark V.

I tried doing research here and LRH, as well as Nosler and Hodgdon Manual with only one post claiming 88.0 grain load(not referenced as max).

It seems that H1000 and RL22 are favorites, and are powders I have, so will start with about 1.50 grains below max on those(87.0gr and 79.0gr respectively). I also have RL19, and IMR 4350 and 4831 but research says to try these if slower powders don't produce. I was suprised not to find more references to the use of Retumbo, though Hodgdon does list a max load of 84.5g for 200 gr bullets so maybe the bullet choice is relatively light.

Any help on Retumbo load would be helpful.

I tried Retumbo in 2 300s, one a Mark V and the other a Vanguard. IIRC Hornady list 86gr as max with 180s. It shot well but velocity was too low to suit me (around 3000 fps) IMR 7828 has been good for mine and I'm loading H1000 for the Mark V now, great combo of speed and accuracy.

Thanks for the response. What speeds are you getting on your H1000 and 7828 loads, and what gr are you running on them. I'm looking for reference points to judge the speed of this barrel. the gun is a friends, not mine.

Avg of 3220 with 84 gr of 7828 and 3100 with 85 gr of H1000 both using 180 Ballistic tips and Partitions. The H1000 is going is going into .5" groups with both bullets out of the Mark V. I'm using Fed 215s for both.

I'm probably the guy who posted the info on the retumbo. I had a couple of 300 wby's. Most like 7828 and h1000. The gun I went to retumbo in was an early lightweight and it HATED everything till I tried retumbo. Doesn't mean retumbo is a best choice for all 300 wby's but it was for this gun. If you have the powder on hand why not play with them all....it's the fun that reloading is all about!!

So what charge weights did you use.

88.2 retumbo under a 180tsx gave me 3250 out of a 26" barrel and 1.9" at 300 yds. This out of a gun that could barely hit a pie plate at 200 yds with some other powders and bullets. I also had very good luck with 86 grains retumbo under a 200 accubond but not as good as the 180 load.

Kraky,

Did you have a reference for what a max load should be on the Retumbo for the 180 grain, as MagMarc showed 86.0 gr as MAX. Just curious.

I went to the range with my chrono and used quickload to help me forcast my work up. Also, this gun likes hornady brass but the batches I got are really really soft in the primer pocket area. Using other powder like 7828 and getting to 3250 fps would give me loose pockets although no extractor marks. Other brands of brass like wby and rem didn't do this. Using Retumbo at 3250 keeps the pockets on the hornady brass intact.
Bottom line is you can use my data and his data as "thermometers" but in the end you have to work the loads up in your gun. My gun is no doubt different than magmarc's gun....your gun is too. My lot of Retumbo most likely isn't from the same batch as his and yours may also be different from all of ours. If you found a really stellar load at 3175 or 3200 there would probably not be much need to keep working up unless you are curious.

84.5 gr's Imr 7828, CCI 250, 180 gr AB's give me 3220 fps & 1/2" at 100 yds.