Starting seating depth for Ultra Mag

[gmorganal]

I have a new Krieger barrel chambered in 300 RUM on my Sendero. I plan on trying some loads out tomorrow. It is a 10-twist, four-groove, varmint contour, 28.5 inches long barrel. I'll be shooting 208 grain Hornady A-Maxes with Remington brass and Federal magnum primers. What seating depth would you recommend to start at?

Thanks for your help.

 

[CJ6]

If you plan on useing it as a magazine fed rifle you should be @ a safe/cycling length for your rifle. If you shoot it single start @ mag length and slowly work to lands (watching for pressure) a AOL tool and bullet comparator will help in this.

 

[40X Guy]

My 28 inch Brux barrelled RUM like Retumbo right at the lands with 190 Berger's. I just ordered a box of 208 Hornadys along with some Viht N570 and want to try those as well. As already mentioned if you are single feeding without the magazine, you can realize the potential of this very potent cartridge!

Frank

 

[gmorganal]

I do and have done a lot of reloading, but everything I work with has either been a smaller case or had a throat so long I couldn't reach the lands. My gunsmith gave me a lot of warning about sticking these big bullets into the lands and lighting the fire to 100 grains of powder, so I was just wondering since I will be single loading this rifle where you guys would recommend starting with the seating depth in relation to touching the lands. Right now I have loaded up 20 rounds, five for sight-in and five groups of three shells each starting with 91 grains of Retumbo and working up to 96 grains. Right now the OAL is 3.886 and is just barely off the lands by a few thousandths. With this length I can put one in the chamber and one in the magazine. THis seating depth puts the boattail/bearing surface junction right at the neck/shoulder junction of the case. Would you think this is a safe place to start, or should I back it up some more off the lands?

 

[40X Guy]

Shoot the ones you have loaded up now, and see which grain amount of powder groups the best, then vary your seating depth, try seating at .020, .015, and .010. off the lands, your rifle will tell you what it likes. IMO you are on the right track with Retumbo. Let us know how she does.

Frank