I just got my 300 Win Mag back. I had it shortened by 0.85” at the chamber end and rethreaded and rechambered with a shorter throat. The original chamber (Walther barrel with custom chamber) had a 0.3085” diameter parallel throat that was 0.300” long and a neck diameter of about 0.3425” (fired cases have a neck diameter of 0.3412”. The new chamber has a parallel throat of 0.3083” and it is 0.140” long with a neck diameter of 0.340” (fired cases have a neck diameter of 0.3385”. I wanted to shoot the new Nosler 200 grain Accubond and the old chamber’s throat was too long to enable me to have the bullets seated close to the lands and still fit in the magazine.

Shooting the rifle yesterday showed me that this new chamber requires quite a bit less powder than the old one to get the same velocities. This morning I fired 5 groups of 3 shots each at 150 yards with the 200 Nosler Accubond and RL25 powder. I tried 75.5 grains initially and three different seating depths. Touching the lands gave me a 1.09" group. 0.025" off gave me a 1.31" group and 0.050" off gave me a 1.03" group. Then I tried 75.0 grains of powder and touching the lands gave me a 1.21" group (with two shots touching) but 0.050" off gave me a group of 0.57". The two shots that were touching with the load on the lands and the 3 shots at 0.050" off would have been in 0.57" had I fired at the same spot. Again these groups were at 150 yards. Velocity at 75.0 grains and 0.050" off was 3045 average for 3 shots. I am going out again this evening to see if the 75 grain load at 0.050” off gives me consistently good accuracy. Rufous

Just back from shooting the 75 grains of RL25 load with the 200 Accubond at 0.050" off the lands. I shot 4 shots at 250 yards to confirm my zero and they landed in a 1.87" group. Then 3 shots at 400 were in 2.46". Then I shot 5 shots at 500 yards and they were in 4.93". Last two shots were at 600 and they were 7" apart. Velocity from my 25" barrel is 3070 fps for 13 shots recorded. I think I will see if 74 grains is as accurate. This load is a bit hot even though the powder charge is low. All 14 shots fired this evening were in 7.4" with 13 of those in 5.1". One of the shots at 600 was 0.5" high and 1" to the right while the other was 3" high and 5.5" to the left. I am pretty pleased with this load. I am not getting awesome groups but it is certainly adequate. My 7mm is giving more accurate groups overall with the 160 Accubond so maybe there is a bit of room for improvement here. Incidentally my Swarovski 3-9 AV scope's clicks have a value of 0.28"/ click, not 0.25". It only took 30 clicks up at 600 from an initial zero at 250 instead of the 34 clicks that it should have taken (based on the ballistic coefficient and velocity and elevation). Rufous.

rufous, I've found that it often works best to change the seating depth in increments of .010"

I'm working on a similar load in 300 H&H. (200 grain accubond bullets) I get two snake eyes and a flier, averaging 2" to 2 1/2" at 100 yards. I think I can do better.

I'm glad they're showing such accuracy potential for you. I would agree that your loads are more than a bit hot with those velocities. Anything much over 3000 fps with a 200 is getting up there in a 300 WM.

I went out again this morning to try 74 grains of RL25 with the 200 Accubond seated 0.050" off the lands. I have shot this bullet in this chamber with 76.5 grains and did not blow the primer out like I did with 78 grains of H1000 so while 75 grains of RL25 is fast it does not seem dangerous. Anyway I was concerned with the high velocity of 3070 fps with the 75 grain charge and since 75 grains looked to be more accurate than 75.5 grains I thought I should try 74 grains. First group at 250 this morning was 1.02". Second group at 250 was 1.72" with all 6 in 1.72" (5 of those were in 1.02"). There was only about 0.7" of vertical for all 6 shots at 250 yards. First group at 400 yards was 3.82" (one shot well to the right of the other two with only 0.75" of vertical). Second group at 400 was 2.11" and it landed in the middle of the first group so I had 6 in 3.82" at 400. Velocity was 3030 fps. I have my load! Rufous.

I went out this morning to make sure that my rifle was zeroed from field shooting positions, not just from the bench. I shot the 200 Accubond with 74 grains of RL25 load at 250 yards from the prone position using my Kramer Snipepod and sling. Groups was perfectly centered and measured 1.7". Then I tried a group from the sitting position with my taller Kramer Snipepod and amazingly shot a 0.76" group that landed in the middle of the first group such that all 6 shots were in 1.7" at 250 yards. This rifle and load are amazing. I could not be happier. I have been trying for 5 years to get a good shooting 300 Magnum. I have finally arrived. Rufous.

Rufous,

Thanks for the posts. Currently using 180 Nosler BT with NO complaints. But I've have been thinking of trying something a little heavier, like the Accubond.

Think I'll give the 200 AB a try.

Regards,