Pressure Anyone?

WHISTLEPIG · Post by **WHISTLEPIG** » Wed Feb 28, 2007 6:33 am

I was doing a little reading about pressure indications which led to a little measuring. With my blade calipers, the extractor grove flat on a new WW case measures .3285. A fired case measures .3300. Difference of .0015. As I have read, this is the outside of a conservative tolerance. If any of you have done any measuring, I would be interested in the results.

Rick in Oregon · Post by **Rick in Oregon** » Wed Feb 28, 2007 7:09 am

WP: The only real way to have that measurement have any meaning, would be to measure just above the web of a fired factory case, and compare it to one of your working handloads.

Is this what you are referring to? As using an unfired case that has not been exposed to the pressure of firing, doesn't really tell us much.

I've read that the 204 operates at much lower pressure than some other high intensity varmint rounds, somewhere in the vicinity of 57,000cup, and have wondered why this is, as many operate in excess of 61,000cup. Wonder what's up with that?

contender hunter · Post by **contender hunter** » Wed Feb 28, 2007 3:02 pm

Also I have heard that the max. pressure for the T/C Contender is 50,000 cup and thats why its not chambered in calibers like the 22-250 , .243 , 270 etc. but is chambered in the 45-70 , .204 , 223 , 7x30 waters . How can it be chambered in the .204 if the pressure is over the max. of 50,00??

glenn asher · Post by **glenn asher** » Wed Feb 28, 2007 3:35 pm

CH, that's a function of case head thrust. Even if the .45/70 is running 30K, that's not too bad, but put that amount on a .473" case head and it might be too much for the receiver to handle. More, in a .378" case head, is okay, but do that in a magnum case head size, and again, it might be more than it can handle. Remember that Encore that came apart? That shouldn't be, but could be, what part of the problem was, there.
I know I'm not explaining it correctly, but that's the thrust of it.

WHISTLEPIG · Post by **WHISTLEPIG** » Wed Feb 28, 2007 4:48 pm

Rick, What I was reading was my Handloading for Competition, by Zediker. He was saying that a new case that was loaded for that first firing with a known safe load could safely expand up to .0015 at the case head. On the second firing with an unknown load the case can expand at the head no more than .00005 for a total of .0020. Any more and the load would be considered over pressure and expansion excessive. I did not explain this clearly this AM. My measurements indicate that after the initial expansion, any subsequent loadings have not thrown my case heads out of tolerance due to overexpansion. This is all according to his hypothesis. I was just wondering about this as I have not seen numbers put on it before. His reasoning for measuring at the extractor grove is that it is an identifiable spot on an area of the case web that is not supposed to be as elastic as the rest of the case and is a spot the can be repeatably measured, as opposed to a random spot somewhere up the case body. Once again not my idea. Just got me to thinking about it. Maybe the weather has driven me crazy.

Rick in Oregon · Post by **Rick in Oregon** » Wed Feb 28, 2007 7:19 pm

Well WP, the weather is driving all of us crazy....I'm hoping for our first squirrel outing for a 2-day affair the 10/11th...we'll see.

Now I see what you were referring to, and it all seems reasonable. I've always had a bit of a problem with the bit about "measure for expansion just ahead of the web of the case".....where ahead of the web? Seems subjective, and open for error. The extractor groove is a known location, and what Zediker says makes sense. Neil Knox also suggested that method back in the late '60's and early '70's, and it still makes sense now. I've always measured either at the extractor groove, or where I know the solid portion of the case web to be. Those readings agree with what I've always thought to be correct.

Thanks for clearing that up....I was in a pondering mode, thinking about it today.

contender hunter · Post by **contender hunter** » Wed Feb 28, 2007 9:03 pm

Glenn ,thrust and diameter I guess all play into it , but its fun just shooting them and not worrying about all that , especially the .204 !!!!

skb2706 · Post by **skb2706** » Thu Mar 01, 2007 8:21 am

Rick in Oregon wrote:WP: The only real way to have that measurement have any meaning, would be to measure just above the web of a fired factory case, and compare it to one of your working handloads.

Is this what you are referring to? As using an unfired case that has not been exposed to the pressure of firing, doesn't really tell us much.

I've read that the 204 operates at much lower pressure than some other high intensity varmint rounds, somewhere in the vicinity of 57,000cup, and have wondered why this is, as many operate in excess of 61,000cup. Wonder what's up with that?

The most common pressure data I have found lists the .204 Ruger in "PSI" and not "CUP" ...there is no correlation between the two. It would be very dangerous to cross these little tidbits of information.

http://data.hodgdon.com/cartridge_load.asp

ch - The reasons a Contender is limited in max pressure has as much to do with case head size as pressure itself.

Rick in Oregon · Post by **Rick in Oregon** » Thu Mar 01, 2007 8:26 am

skb: You're right, I should have listed that as psi, but as virtually on one on the board has either strain or piezo electric pressure measuring devices, it's probably moot, but thanks for pointing it out anyway.

I'm still at a loss as to why the 204 is listed at a nominal 57,000 psi though......

skb2706 · Post by **skb2706** » Thu Mar 01, 2007 8:33 am

no clue...Rick

Possibly to 'not' limit the suitable guns it can be chambered in. ie Contender.

Ray P · Post by **Ray P** » Fri Mar 02, 2007 12:53 pm

I don't have a measurement for you, but aaall I tell you is they wouldn't fit in the shell holder when I was resizing them after firing the factory loads. I Tried different makes of shell holder and the brass was still tight??? When you tried to turn the brass in the shell holder the holder would turn in my press not the piece of brass. Never had any problems with winchester brass and my handloads. Just this one box of hornady??
My only quess is the pressure was on th high side and the brass swelled at the head groove area of the brass. Hot load, bad brass??? Its in the re-cycling can now!!
Later
Ray P

skb2706 · Post by **skb2706** » Fri Mar 02, 2007 1:04 pm

ray - Had this problem on some Remington .204 brass. In my situation it had nothing to do with pressure. The groove in the case for the extractor wasn't cut to allow for the case to fit in a shell holder. May want to check that ...........

Ray P · Post by **Ray P** » Fri Mar 02, 2007 1:23 pm

SKB 2706 thanks for the input. It was only one box of factory loaded hornady. I have shot other factory boxes of hornady and reloaded with no problem other than tight primer pockets. This was discussed earlier on in a post that I read.
Thanks again and later
Ray P

gunut · Post by **gunut** » Sun Mar 04, 2007 9:57 pm

what is the best primers to use for the 204? i loaded some h322 and 32vmaxes and started at 26.5, 26.8, 27.1, 27.4, 27.7. i only shot 1 at 27.7 and pierced the primer. my best load was 27.1 as it made a cloverleaf. so i loaded up 50 and the first shot pierced the primer. i was shooting 5 shot groups at the range and only pierced a primer on 27.7. i was using some old federal small rifle primers. im thinking i need a better suited primer for this high pressure little round and want yalls opinion. thanks Kelly

acloco · Post by **acloco** » Sun Mar 04, 2007 10:21 pm

Gunut - at 27.7 grains of H322, you are 0.2 over the max load. I copied the info from the "load data page" on this site and checked online with Hodgdon - same info.

32. Gr. Hornady V-Max
H322 2.250"
25.5 3826 48,300 PSI
27.5 4030 56,400 PSI

Was the temperature different from your load work up range day to the next time you shot?

OAL different?

Different lot of H322?

Pressure Anyone?

Pressure Anyone?

Factory Loads..40grn A-Max

204 primers