I just started to test some loads using 100 gr. GS bullets in my Tikka .243 and I had some strange pressure issues, the latest was blowen primer and blew the extractor off. Although it did not break and I was able to have the local gunsmith look it over and put it back together it definately is a concern. This load was about in the middle of the load range and unfortunately I did not have my crony with me to check the velocity when this happened. Has anyone out there seen pressure problems with this bullet. The speer manual does not show data using H-4831SC but I was using 41.0 gr. when this happened. Other manuals with 100 gr. flat base bullets show up to 44.9-45.5 gr.

Check all of the "usual" suspects: (1) wrong powder by mistake, (2) partially hung up charge drops in next shell with full charge from powder measure, (3) foregn matter in case prior to charging, (4) partially obstructed barrel, (5) right powder, but misread scale results in 5 grains more than intended, and (6) ad infinitum.

Unless you have a "bad" lot of powder (meaning mislabled or otherwise not in spec) there should be no way that a charge this light would result in excessive pressures. EXCEPT ONE. That would be Secondary Explosion Effect, a somewhat rare phenomenon that may result when slow-burning powders are loaded to a density of less than, say, about 85 percent. S.E.E. seems to result when too much case volume allows the powder to burn erratically, and was the bane of original surplus 4831 when "conservative" reloaders simply loaded too little of it in larger cases. S.E.E. would be very unusual in a case the size of a .243, and also very unusual in a loading density that would have to be close to 90%. I know of no research that indicates the the Short Cuts from Hodgdon are subject to S.E.E., either. Still, if you've got the right powder, you're closer to an S.E.E. underload than to an overload.

A new gun means new load development. A good place to start is 10% below max. Then creep up on your load. Look for the obvious signs of pressure as you go. Sticky bolt lift, shiny extractor mark on the rear of the case, flattened primers, increases around the expansion ring on the body case. If any of these are encountered then back off. What you read in the manuals are merely "guidelines" to be used in conjunction with a healty dose of common sense. When you throw your powder do you then go the pan with every charge and then weigh and verify your weight? Are you certain you did not substitute IMR for H loading data? You did not mention your bullet seating depth in relation to the lands. Of course if you have bullet jam you could get pressure excursions like you experienced. Powder measures will sometimes "bridge" meaning you only get a partial charge when you dump your powder and then the next charge will be overweight--the reason I weigh each and every charge. Do you only work with one powder on the bench at one time? Is it possible you dumped the wrong powder into the wrong cannister after a previous loading session?
And the question no one else has the guts to ask you--where you sober when you loaded those troublesome rounds?
And the last possible thought I have--Do you have Kids? Do you keep your powder locked?

Thomas I just had a thought. Have you taken one of your fired cases and tried to drop an unfired bullet down into your fired case? If your bullet does not drop in freely--this would indicate the neck thickness in the brass you are using is too thick for your chamber.
Take your calipers and measure the O.D. of your fired case. This this the I.D. of your neck inside the chamber excluding brass springback.
So, If you take a .243 bullet and add for example .018 for neck thickness then add that number one more time you get .036 plus your .243 for a total number of .279 Now what was that O.D. measurement of your fired brass? Are you trying to shove 2lbs into a 1 pound hole? This will give you huge pressure excursions like the one you just experienced.
People--this is why they warn you to start 10% below max. until you can verify your math and such. Go measure and then let me know what you find out.

quote:

Originally posted by Mohunt:
The speer manual does not show data using H-4831SC but I was using 41.0 gr. when this happened. Other manuals with 100 gr. flat base bullets show up to 44.9-45.5 gr.

The Hodgdon manual:

100 GR. SPR BTSP
COL: 2.650"


H4831 42.0 2924 50,100 CUP

Based on the above, you were 1 grain under their published max. Perhaps this was beyond your rifle chambers max. Or right at it.