40 S&W it's not the round it's the case support that is the problem


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kidcoltoutlaw
March 29, 2006, 11:47 PM
I say chamber support not hot load

I had a minor Kaboom with a 40 the load pushes a 135 JHP at 1482 fps.
People said I was stupid for firing a max load in a case I did not know how many times it had been fired. Tops it had been fired 3 times .OK lets say there right . So I did this I took a once fired case or a least they were bought as once fired. I loaded 12 plus grains behind a 135 Nosler JHP I say plus because I used a powder measure and 5 of the 10 loaded rounds were 12.3 grains. No big deal right only I loaded the SAME case 10 times to see if it was a case problem. The case held up fine not even a loose primer pocket. I would not do that with a SIG barrel. A case fired in a SIG barrel will not fit in a Bar-Sto barrel until it is sized. The better chamber support from the Bar-Sto barrel let me keep all my fingers and I did not need any Spare parts for me or the gun. I am thinking of selling some SIG barrels to replace them with Bar-Sto barrels I have 9 I could sell.

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mrapathy2000
March 30, 2006, 05:55 AM
imo its both. but when the chamber support is very good to excellent problems will be minimal. but casehead seperation may occur dont hear about it much in pistols.

which Sig model are you referring too?
226,229,239,2340,2022 ?

RyanM
March 30, 2006, 06:25 AM
That's why I had my Glock's feed ramp TIG welded up. It now supports the case 100%, and feeds just fine. It'll even feed empty cases, if you ease them in.

I'm kinda curious how much a 1/10" bullet setback would increase pressure in a 9mm or .45. They say it doubles pressure in a .40. I'd guess nearly the same in most other straightwall calibers, assuming a similar load density and powder burn rate.

kidcoltoutlaw
March 30, 2006, 02:05 PM
Was with a SIG P229 with a SIG factory barrel. Bar-Sto can walk on water the way I see it. I have 4 of there barrels with 2 more on order. Im thinking about selling some SIG factory barrels to get more Bar-Sto barrels. What is a fair price for SIG factory barrels. The bigger question is how do I sell them without getting ripped off. Or how do I get people to buy them with thinking they are getting ripped off,

Thanks,Keith

Grump
March 30, 2006, 02:36 PM
They say it doubles pressure in a .40.

I maintain that this is an Internet/Gun Culture myth. Perhaps more than a decade ago, I read (and later re-read to clarify) an article in American Handgunner which discussed bullet setback, and here is a summary of what it said:

according to some computer software (Quickload?), I ran a projection with some caliber and a fast-burning powder, and HOLY NUMBERS, BATMAN!!!! the pressure went through the roof with only so-and-so much deeper bullet seating.

There was NO attempt to verify whether the mathematical modeling was accurate. Numbers are everything, BUT I can tell you from personal experience that NOT ONE of the 9mm or .40 S&W rounds I've intentionally fired after being set back more than .05 and sometimes fully .10 showed anything near the 60,000+ pressures needed to expand a primer pocket or imprint breechface marks in the casehead. Do the math. Double 33,000 PSI or CUP or Piezo or whatever in either of these higher-pressure rounds should be quite noticeable.

Most of my setback loads were with WW231.

Taylor's knockdown, some other one I used to read about, IPSC Power Factor and other measurements get all screwy when you start plugging in numbers that are outside the norm intended. The classic was the knockdown power of a slow-moving bowling ball. Those numbers or mathematical models or projections lied with the bowling ball!:neener:

RyanM
March 30, 2006, 04:17 PM
Hm. I always thought the double pressure at 0.1" thing was based on actual loads. So much for that.

WayneConrad
March 30, 2006, 05:10 PM
I've got a lot of those gosh darned overfat hardcast lead bullets for 9mm. The manual calls for 1.100" OAL, but I have to seat them to 1.000" so that the entire base can be squished smaller by the Lee FCD (it's only way these blankity-blank bullets will chamber).

I've worked up loads using AA2, Unique, and HS-6 all the way up to book max. No signs of overpressure in any of 'em, and that's with a full 0.1" of setback. No primers flowed, no expanded primer pockets, no nothing. Could be I'm just lucky. It seems likely that 0.1" setback at max load is causing pressure over SAAMI max, but not high enough to cause obvious signs of overpressure. But twice the pressure? It's hard to imagine that me or the gun wouldn't notice double the pressure.

PS: My sense of danger is probably busted. Shooting max loads with intentional setback is not recommended.

kidcoltoutlaw
March 30, 2006, 05:29 PM
What 9mm are you using,

Thanks,Keith

WayneConrad
March 30, 2006, 05:59 PM
The bullets? Kead L-FP 122, from the run he did in... 3rd quarter 2005, if I recall.

The firearm? P99.

HSMITH
March 30, 2006, 08:42 PM
Keith, I have pushed my 40 HARD and not had a problem. My Glock has less chamber support than your Sig from what I have seen. Been a ways past that 12 grains of Longshot with the 135 too. My experience has been that Longshot is fairly linear in pressure increases to a point, after that point it gets nasty quick. Even just a tenth of a grain more than the last load that was just starting to show some primer flow now has a primer that is darn near pierced. Never played with OAL to see what it does to pressures at the top end with Longshot, but I suspect that once you hit a certain pressure level it will go nasty with even a very small change in OAL.

I don't know what the pressure level actually is where it gets ugly, but suspect it is somewhere above 40K psi. Your chronograph will tell you it is coming before it gets ugly, velocity increases will flatten out a couple tenths or three before the primer starts to flow.

I think you are pushing the load a little too hard in some of your barrels. Back it down a bit and do some chrono runs, I think you will see the flat spot in velocities long before you have another case failure.


I don't buy the pressure doubling thing either, that is VERY powder specific and none of the claims I have read have taken the burn characteristics of a specific powder into account. With Clays or Universal? They go from mild to extremely ugly very quick. Power Pistol? It stays pretty linear until you are WAY up there in pressure, well outside of published data.

Clark
April 1, 2006, 11:51 AM
CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The High Road, nor the staff of THR assume any liability for any damage or injury resulting from use of this information.

With the stock Glock 22 barrel, I got case bulges [pre cursor to kaboom in overload work up] with +25% powder charge over max book load:
135 gr 11.6 gr Power Pistol [9.3 gr is max per Alliant Powders]

The Stock Glock barrel had .235" of feed ramp intrusion into the chamber. 40 S&W brass has a .180" thick web. That leaves .055" of thin unsupported case wall.
Then I TIG welded up the feed ramp and chamber and re cut the feed ramp and chamber, so the case is supported up to the web.

With the welded barrel the work up went to +114% extra powder before case failure:
200 gr 13.5 gr Power Pistol [6.3 gr is max per Alliant Powders]

TIG welded G22 and P32s for better chamber support
http://www.thehighroad.org/attachment.php?s=&postid=191655
finished G22, rechambered and new feed ramp for case support to the case
web
http://www.thehighroad.org/attachment.php?s=&postid=245376

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