Concerns with 300WM load

[NCHillbilly]

Looking for your thoughts on a situation I ran into today. I'll try to give all of the info I can. The rifle is a gen 3 Ruger RPR chambered in 300WM. 26 in barrel, 1-9 twist factory barrel with (at the time) less than 100 rds down the pipe. I had some Nosler 210gr RDF's that I had loaded up for some load development. I do not have the latest Nosler manual, but I used the newest Hodgdon load manual, and used data for a Hornady 208gr eldm. The listed starting charge using IMR-8133 is 74.5 grains, with a max of 81.0 grains.

Due to component shortage concerns, I started loading at 75.7grs, and stopped at 79.6 grains. My concern is this; My velocities from start to finish was WAY high, compared to the Hodgdon manual data. My first shots at 75.7 grains was over 2900 fps (measured with labradar). I actually found an outstanding load at 77.8 grains that was sub half-moa, and the velocity averaged 3023. At this level, I got very slight primer cratering with no other pressure signs.

Here is the load data:
Nosler 210gr RDF
IMR-8133 (75.7grs-79.6grs)
FC 17 military cases (1x)
Fed 215M Primers
CBTO 2.859" (touching lands)
COAL 3.600"

My concern is the velocity being so much higher than what my manual lists. I see nothing at 77.8 grs that worries me, and the load is damn accurate. I had used the labradar with two previous weapons earlier in the day, and the readings were in line with what I expected. Any thoughts?

 

[Rocketmandb]

I haven't fired a win mag in years, but 3k fps with a 210 gr bullet is far faster than I would think it would go under normal loads. I was getting about 2850 out of a 24" barrel with a moderate h1000 load and 200 gr bullets.

So, if it is indeed faster than it should be, what are the possible culprits?

Small chamber
Unlikely with a factory barrel, but a possibility. You an measure various places along a fired case and compare to Saami.

Small case capacity of the brass (thicker case walls)
Easy to measure with h20 and compare to other fired brass from the same chamber.

Powder is off
Unlikely to be that much off, but you never know. Can you get a hold of something like H1000 or Retumbo to compare?

 

[wpeach1912]

You may just have a fast barrel. As long as you don’t have bad pressure signs you’re likely fine.

 

[NCHillbilly]

I haven't fired a win mag in years, but 3k fps with a 210 gr bullet is far faster than I would think it would go under normal loads. I was getting about 2850 out of a 24" barrel with a moderate h1000 load and 200 gr bullets.

So, if it is indeed faster than it should be, what are the possible culprits?

Small chamber
Unlikely with a factory barrel, but a possibility. You an measure various places along a fired case and compare to Saami.

Small case capacity of the brass (thicker case walls)
Easy to measure with h20 and compare to other fired brass from the same chamber.

Powder is off
Unlikely to be that much off, but you never know. Can you get a hold of something like H1000 or Retumbo to compare?

I use H1000 and Rl22 in some other loads. I picked the IMR-8133 specifically because it is supposed to give slightly higher MV, and I'm trying to build a load to reach a mile. I could build the load again using one of the other powders on hand, but I don't have enough bullets, and can't find anymore at the moment. This damn situation with components is killing me.

 

[cornhusker86]

 

[NCHillbilly]

You may just have a fast barrel. As long as you don’t have bad pressure signs you’re likely fine.

I honestly didn't see any bad pressure signs at 77.8 grs. Had slight primer cratering. No ejector print, no sticky bolt lift, nothing to concern me. Now, when I got above 78.5, the cratering got heavier and I started getting slight ejector print, still no sticky bolt lift. I've never used the RDF's in the 300WM, so wasn't sure what to expect. They've got a nice high G1 BC of something like .706, but I really had nothing to go by, since I was using Hodgdon's manual and the closest thing they had was a Hornady 208gr eldm.

 

[918v]

Hodgdon uses Winchester brass which has way more capacity than Federal. That’s why the velocity was higher and now your primer pockets are gone.

 

[NCHillbilly]

View attachment 7606151

Thanks. That's kinda helpful and scary at the same time. I've got 2 extra inches of barrel, but I don't think that would get me that much faster than the fastest listing on here. I'm surprised IMR-8133 isn't listed, but I'm not sure how long that powder has been out. It's one of the powders in the enduron series, so it may have come out since the manual was produced. Anyway, thanks for the info.

 

[NCHillbilly]

Hodgdon uses Winchester brass which has way more capacity than Federal. That’s why the velocity was higher and now your primer pockets are gone.

I'll definitely check them with a primer pocket gauge before loading them again.

 

[Bullspotter]

Might want to check pockets now to make sure your not toasting them, and keep toasting them........

 

[NCHillbilly]

Finally got my primer pocket gauges today. Deprimed and checked cases. Primer pockets blown out at 76.9grs of IMR-8133. Fortunately only lost about 22 cases. Next to check case capacities, but at least now I know the limit on this particular load. Still amazed that I never felt it in the bolt lift. Last round fired ejected just like the first.