300 RUM Seating Depth

[Richracer1]

Being somewhat new at reloading (only been doing it about 3 years), how much will bullet seating depth, ie changing the COL, affect accuracy. Reason being, I'm working on my 300RUM load using Retumbo, 200ABs and haven't got very good results. My development COL was 3.645". I have just reloaded some more with 95gn and varied the COL from 3.65 to 3.70". Am I wasting my time doing this or ?????. I got around 1.5" MOA at 100M. My next step is to see what COL groups the best, then start working on the Limbsaver barrel deresonator (something similar to the Browning BOSS). Any info would be great, as I would prefer to shoot the 200AB. I have a load for the 180 AB that's just barely sub-MOA.
Thanks

O, almost forgot, if Retumbo doesn't work, anyone have RL-22 and 200AB information? Alliant has data for RL-22 using a 200gn Speer Hot-Cor with 86gn as max.

 

[Guy Miner]

Changing the seating depth can, in some cases, make a substantial difference in accuracy. Some bullets & chambers seem to tolerate a wide range of seating depths and still produce good accuracy, others are pretty picky about working well.

Barnes TSX's and Berger VLD's come to mind as bullets that have been picky about seating depth for me.

Nosler competition bullets on the other hand have been very flexible, providing about the same accuracy if I load them short to function through the magazine, or long to just kiss the lands.

Dunno how your .300 RUM & Accubonds will react to various seating depths, but it's well worth exploring. Typically my rifles have shot better when I've reduced the jump the bullet makes before contacting the barrel lands & grooves.

Best of luck w/your project, I've been loading for 40 years more or less but only started messing with the .300 RUM earlier this year myself. At this point I haven't tried a lot of different combinations.

Regards, Guy

 

[remingtonman_25_06]

More or less, finding the right seating depth is a matter of finding out where that particular bullet likes to be off the lands. Every rifle/bullet is different. But I can tell you this, .010" one way or the other can make or break a great group.

 

[FOTIS]

My 300 RUM gave best results with 95 gr Retumbo and 92 gr of RL 25. Both with the 200 gr AccuBond and loaded as far out as the mag would allow. Both loads are max :wink: :wink:

 

[Richracer1]

Thanks for the info. The farthest I dare work my COL is 3.67, as this is getting extremely close to the forward magazine wall. Well, hopefully one these COL tests work out.

 

[JD338]

Richracer1,

Load your COL as long as the magazine will allow. Take a look at RL25 and Federal GM215M primers. Let us know how she shoots.

JD338

 

[Richracer1]

Richracer1,

Load your COL as long as the magazine will allow. Take a look at RL25 and Federal GM215M primers. Let us know how she shoots.

JD338

Using my "trained eyeball" :shock: , it appears that 3.67 is the max COL and still fit and function in the magazine. As for primers, all my "magnums" use GM215M primers. In regards to powder, I have 8lbs of Retumbo and 5lbs of RL-22, so getting another powder type (RL-25) isn't very high on my list. I do have 1lb of H1000, may give it a try if the COL testing doesn't pan out. My luck it'll probably work great.

 

[Powerstroke]

+1 For Pop & JD
I have had better luck with the 180gr AB's than the 200's. Powder of choice for me right now is the RL-25. Viht N-165 gives the same results, short of not knowing velocity across a chrony. COL 3.660

 

[Richracer1]

Well, here is the result of today's COL testing. It may not be a one hole three shot group, but not all rifles will do this. This is at 100yds w/95gn of Retumbo, 200AB, GM215M, and a COL of 3.635".

 

[Powerstroke]

Doesn't look too bad at all !!
I haven't tried the Retumbo yet, but so far I've been unable to get the 200grns to shoot......I get those results with the 180's.

 

[remingtonman_25_06]

Richracer- thats plenty accurate for the 200g ab. I worked up a similar load in a buddys sendero. Only thing different is the OAL. I made his 3.660". Velocity is 3225fps, and accuracy is 1" at 200 yards.

 

[Richracer1]

Funny thing, I just got done shooting in Vandenberg AFB's "Any/Any" rifle match with my 204 and then started shooting the Rummy. Made me realize just how hard this thing really kicks, but then a 204 kicks like a 22LR. 8)