There are so many unknown variables, could you please give the following:
1. Weapon-
A. make;
B. model;
C. barrel length
2. Bullet make; we know it is 100gr BTSP but who makes it?
3. COL? How far off the lands in your barrel?
4. Did you trim the new brass? Length?
5. How much crimp?
6. You said you were working up loads, did you load lighter loads, then work up, or did you just load this one?
Reasons: Some makes and models have tight chambers, which can up pressure.
Longer barrels will produce more pressure than shorter ones.
Different bullets have different alloy jackets and can increase or decrease pressure.
The cartridge overall length can cause pressure increases the closer the bullet is to the lands. Touching the lands can cause tremendous spikes.
If the case is too long, when chambered with a bullet in place, the chamber of the rifle may be crimping down on the bullet, causing pressure.
The tighter the crimp, the more chance of getting a pressure increase.
Any one of the above can cause a pressure spike, but a combination of any 2 or more can add up in a hurry. I have published data that goes from 29.0 to 42.0 grains.
My Observations:
First, Remington brass is a hair thicker than Winchester brass, therefore reducing the Remington case capacity, and thereby increasing the pressure when using an identical load to the Winchester brass. I have worked up loads with both types of brass in the same weapon, and almost all Remington loads were 1 to 2 grains less than the Win when pressure signs started.
Second. Powders can vary from lot to lot. Therefore when you load a powder that has a different lot number than the one you have previously worked up, to be safe, reduce the load by at least 5% and work up.
Third Brass can vary from lot to lot, and bad brass can escape factory notice.
