Pretty simple, I am wondering about experiences with 10mm brass-life/condition/#-of-reloads in the Glock 20 SF factory barrel compared to the KKM barrel. I plan on running hot loads that will be at published maximums or slightly below, I will not be going above book max. I will be using Starline brass and 180 XTPs and lead.
I would like to stick with the factory barrel, but if brass life is increased/bulging is decreased I will consider the KKM. From the looks of photos the chamber support seemed similar between the barrels, but the Glock chambers might be a bit looser. I don't know if this has any practical impact on longevity of the brass.
Thanks.
Quote from: control_the_trigger on January 23 2015 12:12:25 AM MST
snip.. 10mm brass-life/condition/#-of-reloads in the Glock 20 SF factory barrel compared to the KKM barrel. I plan on running hot loads
I would like to stick with the factory barrel, but if brass life is increased/bulging is decreased I will consider the KKM. From the looks of photos the chamber support seemed similar between the barrels, but the Glock chambers might be a bit looser. I don't know if this has any practical impact on longevity of the brass.
The more brass is worked , the more brittle it will become. So if the brass is expanded and then resized a lot , sooner or later it will show a crack and become useless.
The hotter loads you run, the more the case expands to the limits of the chamber ( or beyond as in a smile in which case it's junk ).
I can tell you that I mostly do warm loads, (not super hot) with the stock barrel... some cases from starline have gone more than 7x so far ( I don't think I have any loaded more than 7x but no reason to think they won't last longer ).
After I used some of the brass for the now and then 'hot' load, they are put in a bin for light loads and aren't used in my normal reloads... so can't answer the hot loads number. I would think there are many variables.
And, yes, the glock barrels are looser.... And I really don't worry about the brass... just check them over good after every use and reload till NG.
Glock chambers are definitely looser.
Running max loads my Glock returns case heads that measure .431-.432. The EAA runs .429-.430. And my Para run .426-.427.
Like others I tend to give my brass 3-4 hot loads, then relegate it to practice loads, until the case mouths split.
As tommac919 says, brass work hardens. Also, unlike bottleneck cases, which expand and thin the metal just above the web, straight wall cases tend to shrink. I infer from this that the case head and lower case wall do not thin, but I have never checked.
In any case, at least in my perception, your 10mm brass gets more and more pressure worthy over time, assuming you don't bulge a case. A bulged or smiled case has been subjected to shear and should be discarded. Unfortunately, with max loads you will find some bulges.
control_the_trigger, these two guys pretty much covered the bases.
I do shoot so hot stuff from my G-20SF and G-29 (pre SF) factory barrels, both of these factory barrels see a max case expansion of 0.434", which is the measured chamber of the factory barrels. Any more than that they will start to "SMILE" (the smile is a distinct line that develops and is the start of shearing on the molecular level). I will add that I use a Wolff non captive recoil system with 22lb and 21lb spring setup respectively. I have measured a increase in the amount of spring pressure applied to maintain lockup before the slide moves.
The aftermarket Storm Lake 10mm and 40S&W measure 0.4270". My S&W is a tighter chamber at 0.4280", it also uses a Wolff 22lb spring.
With all of that said, can the brass still "SMILE", YES, if the load is of such a high pressure impulse to exceed the brass and recoil systems. Brass quality can be quite different from one make to the next. Star Line is a quality product which is made for handloaders, with that said it is softer more malleable so that you can get more uses from it before it work hardens with use.
I will add, that I inspect and pass-through size all of my 10mm brass prior to resizing. This has shown to recondition the brass, where most standard sizing dies can't reach. What this does is squeezes the case head back to fit the case gauge and even improve the primer pockets on those that had gotten loose. I can say that this has been the most important part of my loading process, this has made the cycling and feeding reliability 100% in any all of my guns.
Over time and use I have seen brass split usually longwise, in testing the limits of some loads (factory and handloaded), I have experienced popped primers, and have seen only two SMILED cases with the same, by the way it was not from the Glock barrels.
The use of the faster burning powders can also cause casing failures because the pressure builds so fast it tends to snap the brass outward to fit the chamber.
Good luck and best regards! :D