I was looking at the guidelines suggested for the Triple Shock, and the use of the feeler gauge to measure the case head expansion to identify excessive pressure. If a feeler gauge is used between the bolt face and the belt and .0005 identifies excessive pressure that would be .001 with a micrometer. Is this right? I think it may but it may be .0005 over all.

crimedog - NO - .001" is TWICE that of .0005".

.0005
+ .0005
.0010

If you are getting .001" of expansion, there is TOO much and you are probably over expanded, and over pressures. Other idea might be you can't read the micrometer well enough. I would get a digital one that reads to .XXXX" and make sure before duplicating that load again.

You would not want more than .0005" of expansion from a new, sized case at the head, to a fired case at the same point. After that.0005" is where you will be into excessive pressure.

If you use a .0005 feeler guage or blade micrometerto measure the space on one side, the other side would have streched .0005 also making the total overall strech .001, that is with once fired brass. Please read the link and tell me how you perceive the instruction. I didn't work up a load.



To compensate for the reduced pressures associated with the Triple Shock, you may have to work up 1 to 2 additional grains above listed loads to achieve equal pressures. Pressures can jump dramatically; therefore we recommend that you work up in 1/2 gr. increments until you are no more than 1 to 2 grains above the listed max load or until signs of excessive pressure are evident. Whichever comes first. You should watch for excessive case head expansion, sticky bolt lift, flattened primers or shiny spots on the base of the case. If you have case head expansion of more than .0005" with a once-fired case, this is a sure sign of excessive pressure. You will have to measure your case head with a Blade Micrometer just in front of the extractor groove, or you can use a regular micrometer and measure the belt on belted cases, before and after shooting. When any of these signs appear, back down one full grain and you will have a max load for your gun.

The other side of what?

The case head expansion of .0005" is meaning the total amount of stretching of a cases TOTAL DIAMETER just above the grove where the extractor will pull the case out of. You measure the case, nothing more.

I have seen data that lists .0005" as the maximum allowable expansion just ahead of the extractor groove on non belted cases and .0007" on the belt of belted cases.However this only works with new cases as each firing will supposedlywork harden the case slightly.This is taken from a loading manual but I don't recall which one right now.Then again the results can vary if you get a lot of hard or soft brass.I have seen the measurements vary from lot to lot even though the load and resultingvelocity were the same.Most remington and federal loads that I tested expanded .0002" to .0005" when fired in factory rifles,while I have seen weatherby factory loads expand over .002" when fired in weatherby rifles.Some of the new 270wsm and 300wsm factoryloads expanded .001" when fired in factory rifles.These are merely my observations so feel free to either ignore them or to draw whatever conclusions that you see fit.

For example:

The 8mm Mauser SAAMI specs for the brass just above the extractor groove is .4716". That is what the diameter of new, sized brass should be. When you fire, you measure the same point above the extractor groove on the case. If the measurement is more than .4721" diameter, youare over max for the gun. Then itsays to drop down the load one full grain, and you are at max.

Be sure to measure and mark each case before firing as even brass from the same lot# will vary enough to skew the results.Also measure at several points around the case as they are seldomperfectly round.

Barnes replied to my email and it's .0005 over all.