Okay, I loaded up 22 rounds of 300 grain CT Fail Safe moly coated bullets. Using my Nosler #3 guide and IMR 7828 powder, the recommended charge is 110 - 114 grains with the max load listed as the most accurate for their 300 grain partition. I chose a middle of the road charge of 112.5 grains figuring that the moly probably would reduce pressure somewhat.


Midway had a sale on the Nosler #5 book so I picked it up. The load listed for the 300 grain patition and CT fail safe with 7828 is 107-111 grains and 100 fps slower all the way around. Now my quandry is my loads would be a 1 1/2 grains over the #5 listed max, but still 1 1/2 grains under max load with the number 3 guide.

Should I pull the bullets and powder and start over, or shoot a few and watch for signs of pressure. I wonder why Nosler has reduced their charges. The number 3 guide was made in 1989. Has the IMR 7828 changed over the years, or is this just another conservative reduction in the wake of liability?



Good looking round though!

I donno I have a #3 and have used it in 2 378s but it was with the partition. Is your 378 a factory weatherby or have a weatherby throat? Is there a reason you are useing moly bullets?

It's a factory Mark V with the normal freebore. The CT's were on closeout from Midway for 20 bucks a box of 50. No reason for using moly other than the closeout price. In fact two more boxes I ran though the tumbler and took most of the moly off. I heard of some accuracy problems, but I bought 10 boxes....plenty to develop some good loads I'm sure or the rest will go on ebay.

Keith

I just wonder why t

While I cant comment on the CT/molys I would start 5-10% below max and work up. You have a mic. and a chrono? I wish you luck... its always nice to see a fellow 378 user.

The liability issue is overrated on this point. Most of the reduction in loads over time can be attributed to better measuring of the pressure in cartridges and need for all the pressure measures to stay below the maximum. There was a good thread on pressure a few months ago where someone explained quite thoroughly the statistical measures involved. The short version as best I recall is that it's not sufficient for the average pressure of the sample of cartridges of a given load to be below the maximum pressure but all the sample cartridges of a load must measure below the maximum pressure. This insures that all catridges of a given load are safe not just the average cartridge.

Since you have a Weatherby, which is a hell for stout action, and it has the factory freebore, which is generous to say the least, this is probably safe to try. BUT, why would you want to? Like smallfry said, start 5-10% under maximum and work up.

LWD

Keith,
This is an example of the need to pay attention to the bullet type specified by the manual, if they are specifying.

Some bullets may produce pressure spiking whether by vent of too hard, soft, long, or grabby friction from the bearing surface characteristics, etc.
I believe the CT Fail Safe did not exist in 1989, eh?
The load was reduced to give one that would work safely with both the Partition and the CTFS 300-grainers.

The CT-FS is a longer bullet, is it not, and has a steel cup inside its base, does it not?
Both of those features might increase pressure for a given charge of powder versus the old Partition.

BTW, I have found the Sierra GameKing and the Partition to be similar in the velocities they produce with the same charge.

111.0 grains of IMR-7828 is my favorite load for the 378WBY with either the S.GameKing or N.Partition, producing about 2900 fps from my 25" barrel (rechambered CZ), and excellent accuracy. I would not want to go higher.

You ought to pull the bullets and start with the new starting load in edition 5.

BTW, I have a copy of all 5 editions of the Nosler manual, thanks for reminding me to install them in a shrine.

Thanks for the info guys.

I'm going to pull them and start over. Usually I only load about 5 at a time, but I got carried away with my new rcbs chargemaster!

My wife complains why I have so many reloading books, but this is a perfect example of the need to keep current.

Keith