i was reading on another thread about a guy who was worrying about web growth of 0.003" after firing. i went to my bench and randomly grabbed a piece of fired brass (.300 Savage) and measured the web on it as well as a piece of unfired brass. guess what......the fired case was .003" increased at the web. is this really unacceptable stretching in the web?

Please be specific as to where this "web" is. Measuring from the base how far up the case are you getting .003"?

The term is usually called head expansion and in a rimless case like your .300 Savage it's measured just above the extractor groove. At that point an expansion of .001" would be considered hot.

You must understand that the web of the case will not grow from firing, it will only get thinner. The web, properly spoken of, is at the base of the case, not the sides.

When you measure head expansion, as previously described, that same expansion will actually thin the brass. In additon, this is probably not what you are seeing. You can only measure head expansion on the rim, the belt, or just barely in front of the extractor groove. Acceptable limits for head expansion vary according to the exact method used, but load up until you get 0.0004-0.0005" (ten-thousandths)and back off a half grain of powder and consider that your maximum.

What you are seeing is beyond the head of the case, forward of that described area, and in a place where the brass has thinned out quite a bit--according to its natural taper. This area starts to bulge because it is made to do so. The main function of a cartridge case, in any event, is to seal the breech. What you are seeing is the expansion ring where the case started to stretch to fill the chamber and seal the breech. It is called the expansion ring, too. It is normal because the chamber has to be a little bigger than the case or you cannot feed the ammo into the chamber and 0.003" at this point is not excessive at all.

As long as all you are seeing is expansion at its normal place, all is fine. I have a rifle that will expand a case considerably more than that and a case has never ruptured. Cartridge cases are made of brass so that they will expand and seal the breech and then shrink back a little to allow release for extraction.

Hope this helps.

my mistake. you are both right. i meant to say "head" not "web". if either of you have a copy of "Handloading for Competition" by Glen Zediker you might refer to his cartridge case cutaway on page 30. that was the picture i was using to desribe the location of my measurement. in his picture, my measurement was taken at the web. in any case, i measured them again and actually read .002" as opposed to my earlier measurement of .003".

i was careful where i measured this time. i measured immediately above the extractor groove. i put the caliper jaw as close to the beginning of the groove as possible. anyway, there are no signs of bulging like you described, George. whatever is happening is happening uniformly all the way up the case. i guess i'll really set it up this weekend and check it for accuracy. the rifle is a recent acquisition.

Savage99: from you name here, i assume you are somewhat knowledgeable about Savage99s? if so, how can i tell which one i have? there are a whole mess of variations of this rifle and i'm curious. the only thing i know for sure is that it is not a 99E. i already have a 99E and this one looks all together different.

Bill,

I am not expert at all on Savage 99's. I have but two however I like to hunt with them. One at a time however. Both of mine are 99F's with sn's about a million.

Over at www.24hourcampfire.com you will find an active Savage section in the forums.

savage99: well heck, i thought i was on to somethin there. i'll check out the forum you suggested. thanks again. by the way, your 99s are newer than mine. mine is 74xxxx. thanks again. i too like the 99 to hunt with.

eshell: never considered that angle. i'll fire it again this weekend and heed your advice. thanks.....

Bill,

I'll give you my experience with handloads and factory 416 Weatherby ammo and then hear what others have to say about it too.

I use the Oehler 43 for pressure testing and MV and have tested factory ammo only for reference, at $100 a box it's to damn expensive to use it for anything else.

Both factory, and handloads using virgin brass both measure between .602" and .6025" on the belt, which is the same location I measure case head expansion on beltless cases too. After firing 400gr Swift A-Frames in the factory stuff it measures between .6055 and .606". Now pressure in the factory ammo was 63,000 psi ave, so I loaded my handloads to the same. Well, the A-Frames would duplicate the 2650 fps MV and belt expansion was exactly the same too.

Now it gets interesting...

Take the same cases and load up the same load, that didn't exceed that pressure and you get no additional expansion, or maybe .0005" more at the most. It always stabilizes at .606" if pressure is below 65kpsi, and this is for three, four, five, six more loadings, it don't matter. Now, if you move the pressure up to about 67-68kpsi or above, the belts will go to .607" in one firing. If high enough, .6075" and sometimes as far as .608" max if near 70kpsi. The point I'm trying to make is, if I get to a point where belt expansion is been increased beyond the initial expansion.... it won't stop, as the loads are too hot, it will increase by that amount with each successive loading nearly. When it gets to .608" it's time to pitch the brass, as it's too difficult to cam the bolt open the last little bit. If it's difficult to lift the bolt from the very beginning, headspace is too tight(usually off the shoulder tho), if it's only too tight to cam over the last bit and lifts easily, headspace is fine and case head has expanded too large.

The initial growth on the first firing of new brass tells us quite little, but after that can tell you quite a bit if you measure at the same place. The FL die will not size down the case head, just above it, so when it gets too large the brass is toast. There is a guy who makes a collet for sizing them, just not the big Weatherby case, and it may work fine. I do know mine stabilize at 65k or below, and if I had to reduce them to 55 or 60kpsi to keep it from growing, I'd definitely go to a beltless or get the collet die.

So I think .003" - .004" "initial" expansion is just filling the chamber, however large it may have been cut back there, after that you'd better not get .003" or .004" tho!! In my opinion, if it doesn't stabilize there or a thou above, you're too hot and fixin to loose cases if you stay there. I'm here to say, one hot load can ruin a case this way, well before it fails and ever leaks. In my case, at $2.00 a piece for the 416 cases, I watch this very closely and can't afford to loose any and go over 65kpsi.

Brent: thanks for the help. i'll watch close on my reloads.

[ 09-11-2003, 20:30: Message edited by: bill smith ]