Taterhead, it is understandable, as these companies are pushing the threshold of the max pressure range, not all firearms handle the same high pressure load the same way either.  I have asked Underwood about their ammo and they swear they are inside the SAAMI pressure values, but who is testing? and what testing is being done?

Yes the bore getting fouled can really affect the pressure...good call!

When working too close to the edge, doesn't leave room for the safety of small changes!

Dieselman, that needle is just past the 20 mark ever so slightly, if that was a digital caliper you would see 0.4215", I have measured many of the cases from Starline.

What is the measurement on one of the cases with popped primers?

He showed 0.4265"

Oh, I thought that measurement was taken above the extractor. Hard to follow along on this phone.

So some growth! !

Yes that was at the extractor cut, You were looking for a case rim measurement?

Yes. Exactly. Pressure that increases the primer pocket will manifest in an enlarged diameter case rim/head diameter. The rim?head diameter will grow over time in small increments,  but suspect these have noticeable enlargement. My friend's rims were too wide to fit in a gage after one firing even though the body of the case resized ok.

Measurments of other loads for comparison


#1.  Remington 180 gr UMC = .421  Chronographed @ 1128 fps  UMC brass


#2. Underwood 180 gr Gold Dot = .4225 Chronographed @ 1345 fps   Underwood brass


#3. 10.9 grs Bluedot/ 180gr XTP =  .423 Chronographed @ 1310 fps  Armscor brass


#4. 8.4 grs 800X / 180 gr HST =  .4225  Chronographed @ 1250 fps  Armscor brass

Yes, I have used the pass through system on some brass that did pop primers and were smiled as a test.  The pass through did close it back some to hold a primer but I don't recommend it!

The powder being a faster burning powder is building it pressure peak before the bullet can start to move because of it heavy weight.  This is also why we see some of the faster burning powders not shown with the real heavy bullets.

Quote from: The_Shadow on March 22 2015 03:49:00 PM MDT
Yes that was at the extractor cut, You were looking for a case rim measurement?

nonfired case rim = .420

blown primer case rim = .4225  ( Taken at widest point. Case rim is out of round)

Yes, it is stretching usually vertically in relation to the feed ramp.

Thank you all for carrying on this conversation with such detail in public.  It a fascinating and educational opportunity for us all.

It is educational, makes me interesting in handloading.

Would like to do 10mm & 38 Supers, saving the brass but don't want to spend too much.

  That barrel is a little tight in my opinion comparing numbers I have gotten in the past.

Quote from: Intercooler on March 22 2015 06:44:50 PM MDT
  That barrel is a little tight in my opinion comparing numbers I have gotten in the past.

In what regards are you referring to?  Velocity numbers or something else?

On the hotter stuff I see .428 - .431when measuring the expanded brass. Your results seem really low and makes me wonder if that is forcing everything out the back. I think their must be a nice balancing point.