I chronographed 3 factory Weatherby 200 gr NP rounds out of my 30-378 W today. Velocities were between 3324 and 3389 fps.

Im handloading 116 grains of Hodgdon BMG50 and only getting 3180 on the chrono (yes I realize this is above Nosler's book value for this bullet, Im reading pressures and measuring case head exapnsion, no lectures please). The highest listed velocity for any handload with this bullet is 3200 fps. Most are 3050-3180. Are powder manufacturers "downloading" this round to account for rifles without free bore?

180 to 200 fps more from a factory load than a handload is way out of the norm based on anything I've seen. Anyone else seen this? My case head expansion, primers, and easy extraction of cases tell me my pressure is still low.

If everything is fine, then you might as well proceed ahead carefully.

If you're checking primer pocket expansion and all is well.....besides the routine other things to look for.....no other signs of pressure.....I'd add a grain and see what you get.....continue until you see signs of pressure then back off at least two grains.

Most of my guns have been self chambered very tight to the "GO Gage" and I know the headspace is quite close.....so I rely on the appearance of primers as well.....and actually quite a lot!

How's the primers look?

What really got me thinking is that the actual measured velocity is 200 fps higher than the advertised velocity for the factory ammo. That never happens. The chrono is showing 180 gr velocity for 200 grain bullets (yes i pulled a cartridge apart and weighed the bullet to make sure its a 200 grainer).

Any way to accurately measure primer pocket expansion (other than ;oad it 3 time and see if the primers no longer fit tightly). I get very different data using dial calipers just based on where in the pocket I measure. It seems that the that the pocket doesnt have a slight taper towards the bottom.

Primers look fine, no flow where the firing pin hit em and the edges are still radiused, no set back etc... Extraction is easy, no hard bolt lift.

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Originally posted by elkhunter:
Any way to accurately measure primer pocket expansion (other than ;oad it 3 time and see if the primers no longer fit tightly).

Actually if you have gone too far you'll notice it immediately at the loading bench seating the very first primer...it'll seem like a loose fit and will be obvious.....this is assuming you're a practiced reloader.

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I get very different data using dial calipers just based on where in the pocket I measure. It seems that the that the pocket doesnt have a slight taper towards the bottom.

A dial calipers is a poor tool to measure case head expansion or primer pocket expansion....

Go to the press and seat a new primer.....you'll have a feel for it immediately!

Most folks would consider 3,200 fps on a 200 grain bullet good enough.....but this is your gun and your call.....

Elkhunter, I don't personally load for the 30-378 but do for the 338-378. I'm using IMR7828 with good success and comparable velocities to factory ammo. The load I worked up in the cooler months averaged about 20 - 30 fps shy of factory. I shot the same load when it was 108 outside and the handloads were faster then the factory loads by about the same margin. I'm more then 1 grain shy of the listed max using Barnes TSXs so I wasn't too concerned about overpressure in the heat. During that session I saw zero signs of pressure and the brass measured out as expected from the previous load workup. Factory 225 grainers were going approximately 3170 and I was getting roughly 3150 in the cool months. In the heat the factory ammo was running about 3185 and my handloads were running about 3205. Again, no signs of pressure. In my Accumark the factory velocities I recorded were very close to the listed values for factory ammo.

Ken....