I use a RCBS Case Master to monitor head wall thickness after each firing. I think its a great tool, I've been using it since I started shooting and reloading.
So far I've only found it neccessary to judge case life in this sence with my 6BR brass. My other cartridges tend to get turfed due to primer pockets getting loose over time, but the 6BR's just keep going until the heads thin. I've been turfing them when the valley gets less than .020" thick given that area of the case is approximately .032 thick when new.
I haven't seen a miinimum spec for this and think its probably best to work on a percentage loss rather than a minimum thickness.
Im interested to hear other members thoughts or process'?
Hi Dennis , I see no one has posted so here goes . This is coming from an f standard shooter . I've never measured the wall thickness at the head . But that is a cool little tool ! I've just always thought that when . The primers don't seat as well as they used to ..... Time to replace !
What sort of variance do u get between cases after they've been fired ?
Well i dont think so. As a 303 shooter/reloader you put wheels in motion because of the problems with 303 cases. That dial guage is now on my christmas list.
Will make life a whole lot easier. THANKS.
Not a waste of time and now has me thinking Denis. I have had one of these for a while and stopped checking case wall thickness a long time ago. The tests I did were different to yours though and I just searched individual cases for thinning near the web compared to further up the case. I just assumed once you control your headspacing well and have bugger all difference between fired and unfired cases you would see very little thinning (I did in intitial testing) and it would appear in a distinct band where you have the dial gauge located. The old consensus with poor headspacing was a dramatic "band" of thinning near the web that eventually split. But they may have generally been getting thinner??? I don't know. I tested tsome 6BR's at the time with 20+ firings and saw very little difference in the band where you have it to further up the case but I cannot tell you the overall thickness.
As Bindi says the old 303 rear locking bolt, rimmed case is a whole different story for headspace and case stretching issues.
But specifically to try and answer your question I guess if you start to see any cracks or separations then you have gone too far.
The other questions this raises are -
"Where is all this brass going - presumably forward (shoulder and neck) and backward (base and extraction groove)???"
"Are the shells getting a lot lighter from trimming and turning? (or are necks/shoulders getting thicker?)"
"Are you seeing much variation in case volume developing??"
One thing I have noticed with 284 brass is as the primer pockets start to loosen, the flashholes are also opening up - Some quite significantly especially the few fired in the rain last year. (that were ditched).
G'day all,
fwiw, I lost a set of 25 new 6ppc cases because I incorrectly set the FLS die to make 10 thou gap at the shoulder instead of 1 thou. It took around 20 firings (500rds) and 3 months but they all failed within 2 firings of each other in a match in Sydney, luckily I was able to borrow 10 cases to finish the weekend.
On inspection, all started with a bright shiny ring just forward of the extractor groove and I still have them in my reloading box as a reminder of the pitfalls of creating excessive headspace!
I've never worried about it since, but I keep a metal paper clip straightened out like the probe on that tool and sharpened the tip to a chisel point so I can drag it along the inside of the case.
It's surprising how sensitive your feel can be as you can detect the thinning od the case wall and I then make a decision as to ditch the brass or keep using it. I may dissect a case to check if I feel the need.
But I haven't lost a case now I've corrected the way I set my dies for my rifles. The barrels wear out now, not the brass.
Hope this helps,
Cheerio
Ned
If you regularly trim your cases and you are trimming a lot off, there is only one place it can come from--just in front of the web. The case will ultimately fail.
The cause of this is headspace -- too much of it. For those who size after every firing with a body die ( I do ) you need to make sure that you are not introducing clearance between bolt head and case.
It's better to set your dies to give a thou crush. Cases will still stretch over time but not as much as if you set with a couple of thou ( or more ) clearance.
Barry Davies wrote:If you regularly trim your cases and you are trimming a lot off, there is only one place it can come from--just in front of the web. The case will ultimately fail. The cause of this is headspace -- too much of it. For those who size after every firing with a body die ( I do ) you need to make sure that you are not introducing clearance between bolt head and case. It's better to set your dies to give a thou crush. Cases will still stretch over time but not as much as if you set with a couple of thou ( or more ) clearance.
All quite correct Barry. I do not like crush which translates into more bolt thrust, maybe not important but I like to avoid it. I run with about .0015" "bump". & consistently have "good" batches of brass last to 50 plus reloads. I do not neck anneal or use bushing dies or expander buttons. Excessive shoulder bump, tapered cases with less than 30 degree shoulders along with high pressures are the culprits of web thinning. These are my findings for what they are worth & which I have accumulated with over 50+ years of hand loading in all manner of rifles, calibers & conditions.
Keith H.
I don't mic all my cases. When I clean and check at each reload I use the scribe to feel for the groove. If there's no groove or its barely felt I won't bother. If the valley feels deep I'll mic them.
With my 6BR brass, I body size/shoulder bump .001"....... when I do.
I use to shoulder bump the 6BR every firing though I only body size approx. every 3rd firing now.
This first batch of cases has 20 firings.
The wall thickness at the head in a newish case is approx. .032" and tapers down to approx. .020" just before the shoulder junction.
I wonder if as the brass flows, the taper in wall might also start even out slightly.
That said, these cases are lighter than they were new. I'd have to check my previous load data to be certain of how much. I think each case might be on average between 1 - 2gns lighter.
I trim them to length every 2nd firing. Normally only .001" - .002" comes off if that. More was coming off when the cases were newer.
I'm definitely not over sizing the cases. I'm on the ball with my shoulder bumping.
Regardless though, these cases are thinning and need monitoring. I don't want to let them get to the point of cracking. Just wondering if others had a limit so to speak.
I guess I could keep firing them until I get the light ring around the head, measure it and that's the limit.
Point is Denis, If you correctly headspace and don't use hot loads, you don't have to worry about case separation, as the necks will split long before any sign of imminent separation. ( unless you anneal the necks )
I agree with Keith's statement re extra lug pressure because of cases being too long, but a thou or so you will barely feel.
Head clearance causes case stretch--trimming--thinning of the case-- followed ultimately by failure.
I don't think you could state a minimum case thickness at the point of ultimate separation as this would vary depending upon a number of circumstances --not the least being case hardness.
KHGS wrote: I do not neck anneal or use bushing dies or expander buttons. Excessive shoulder bump, tapered cases with less than 30 degree shoulders along with high pressures are the culprits of web thinning. These are my findings for what they are worth & which I have accumulated with over 50+ years of hand loading in all manner of rifles, calibers & conditions. Keith H.
Keith if you don't use a bushing die or expander button I am curious how you do resize necks? I am always looking for ways to improve my system.
Dennis,
Looks like a very handy and versatile tool that is now also on my wish list.
Thanks Barry for the advice. I anneal every firing and have done from the start. I don't think my necks will be splitting any time soon. Of late, I've skipped annealing on the subsequent firing where a meet has left me time poor. But generally the 6BR's get done every firing.
That might raise another possibility. Maybe softening the necks and shoulders every firing allow more brass flow than if the neck and shoulder was allowed to work harden.
Thinking back on the case weight reduction, a fair percentage of that would be attributed to having turned the necks twice in their life. Once at the beginning and another at approx. 12 firings.
My loads a standard 105 VLD load of 30.4g AR2208 with CCI450's.
Denis - I don't like water. The surface tension can create bubbles and inaccuracies but it is what most use. I use metho; weigh dry case with a lead shot squeezed into primer hole for a seal (BB good for large rifle - can't remember small rifle) then wet case insde and tip out and fill - carefully watching meniscus. With care this can be done repeatedly to within 4-6 mg.
The weight loss of brass gives you a good indication of how much case capacity is "gained" also (just remember the conversion ratio of brass weight to water weight.
I don't do it often but have used this method for some of our experiments of case capacity vs brass weight and velocity/pressure etc
I may have misunderstood your first post though - only a crevice and not general case thinning - in which case I could find no evidence after 20 firings of 6BR when I did it. - gauge didn't move at all for last 1/3 of case by memory - I may check a few of the old cases again though just for fun.
And I have Quickload and do use it to get a rough idea - especially on the few wildcats I have made but then just work up a load as per normal methods.
KHGS wrote: I do not neck anneal or use bushing dies or expander buttons. Excessive shoulder bump, tapered cases with less than 30 degree shoulders along with high pressures are the culprits of web thinning. These are my findings for what they are worth & which I have accumulated with over 50+ years of hand loading in all manner of rifles, calibers & conditions. Keith H.
Keith if you don't use a bushing die or expander button I am curious how you do resize necks? I am always looking for ways to improve my system.
Dennis, Looks like a very handy and versatile tool that is now also on my wish list.
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