Seating Depth Question

[TBASTIAN]

Here's a novice question...I just purchased a Hornady Lock-N-Load OAL gauge, and am working on some loads for my .300 RUM. The OAL's that I'm getting for the 200 grain AccuBond, and 180 grain Partition are well over the maximum OAL listed for the cartridge, and look to be longer than what my magazine will allow. Since I don't believe I'll be able to get close to the lands what is a general practice for OAL starting points? And is it suggested to work up and down in 0.02" or 0.05" increments. Thanks in advance.
-TB

 

[SJB358]

TB, I would start at mag length.. Two 300 RUMS (Brian's) have turned in some AWESOME groups. Distance to lands doesn't seem to be magical for them, at least not in those two cases with 200 AB's. You might have to tweak, but I bet once your around 93-95 grains of Retumbo for the 200 AB, you'll find something magical. Brian can give you his details, but both of his shoot awesome.

 

[Guy Miner]

With my limited .300 RUM experience, I'd agree. Start at magazine length, working with that 93 - 95 grain charge of Retumbo and the 200 gr AccuBond. It's an excellent and well proven load.

Typically the .300 RUM produces excellent accuracy.

 

[TBASTIAN]

Thanks guys.

 

[Oldtrader3]

I would work up or down in .025 inch increments. You can get finer when you get close to optimim.

 

[kraky]

I've owned 5 wbys that all shot pretty darn good at magazine length. The 6th one didn't shoot anything worth a crap. I mean 5-8" groups at 200 yds. Finally after trying a gazillion powder and bullet combos I tried seating really deep. The gun got so good it now shoots several combos under 3" at 300. It was a cruel lesson to learn.....never figured seating depth could take it from shotgun to tackdriver but it did.

 

[DrMike]

I worked up a load with my 9.3X64 Brenneke. The load was built around the 250 grain AB and was 0.010 inches off the lands. Unfortunately, I could load it in the magazine as it was too long. Consequently, the rifle was at best a two-shot proposition. That was fine, as there are few animals that need more than one shot. Nevertheless, I wanted to get a load in this new rifle that I could load the magazine. Here is the first test I ran with the load. The groups from left to right are 3.310 inches, 3.320 inches and 3.340 inches. They fit the magazine. At 3.340 inches, the group tightened dramatically. Velocity changed by about twenty-five fps with this final tweak. Seating depth can be magic for a good rifle.

[img]http://i251.photobucket.com/albums/gg316/DrMikeS/93X64250ABRL15.jpg[/img]

 

[Guest]

The old "seat it close to the lands for best accuracy" thing is a complete misnomer in my experience. Can rifles shoot well with bullets seated within .010" of the lands or closer? Sure, I bet some can. But every rifle I've ever loaded for has liked loads shorter than that. I always start at either magazine length or .010" off the lands, whichever is shorter, and work back in .005" increments once I find a decent velocity with a safe powder charge. My best shooting rifle is my 270Wby and with the freebore in that thing, my bullets are not even seated in the same zip code as the lands.

 

[OU812]

TB, I would start at mag length.. Two 300 RUMS (Brian's) have turned in some AWESOME groups. Distance to lands doesn't seem to be magical for them, at least not in those two cases with 200 AB's. You might have to tweak, but I bet once your around 93-95 grains of Retumbo for the 200 AB, you'll find something magical. Brian can give you his details, but both of his shoot awesome.

Good advise above, it will serve you well. My 300 RUM loves 94.5 retumbo, COL of 3.670 and a 200 AccuBond. I'm betting your accuracy COL will be between 3.650 and 3.675, Retumbo is the powder for the rum, RL-25 works well also.

Bill

 

[TBASTIAN]

Thanks guys. This really helps.

 

[remingtonman_25_06]

I shot a lot of H1000 in my 300 RUM with 200-220g bullets.

With the 200g AB, 92g H1000 was the load for my rifle...Retumbo shot decent enough at 95g, but not near as good or consistent as H1000.

Mine were seated to mag length and shot exceptionally well from the LSS.

 

[Oldtrader3]

Seating depth change problems seem to mostly involve really slow burning powders. Those of we mere mortals who use standard burning rate powders seems to have much less of an issue wih seating depth.

 

[jmad_81]

Mike, I have been under the impression that a guy wanted to go shorter when he was seeing the two and one groups. I have been getting 1" groups in that fashion with my 270 Weatherby. When I tried to go shorter groups got worse. I never bothered going longer, simply because of the line of thinking that two and one you shorten the COAL.

After seeing your groups, I'm going to try it going a bit longer. Couldn't hurt, and might just turn it into a .5 MOA rifle with a 140 AB doing 3285 fps.

A guy can sure learn a lot from hanging out here. Thanks.