MTM plastic storage boxes and brass failure

[Ray Newman]

In another thread on case separations, Griff wrote:

“Don't store empty brass in a plastic box like the MTM. I had a case separation on a round a few weeks ago. Loads were "hot", near max, but still about a factory equivalent. The separation ocurred at about the point at which an empty case would rub against the plastic case as they rattled around.”

See: http://www.levergunscommunity.com/viewt ... =1&t=47373


Griff, if I am reading your post correctly, you claim that the cases rubbed against plastic MTM box and this contact between the plastic and the brass caused the brass to fail?

What you experienced with the MTM box is entirely different from mine.

I predominantly shoot .45-2.1” (AKA .45-70) and .45-2.4’ (AKA .45-90) as well as a few other calibers “on the side”, like .45-110, .30 WCF, .35 Rem., .32 Spec'l. and .32-40.

On some of these cases, I have noticed this “ring”, but always attributed it to the plastic discoloring the brass, not weakening it. These cases have been loaded between 10 and 25 times without any case separation. The only failures to cases stored in MTM boxes were split necks when I failed to anneal the cases.

[Hobie]

That makes absolutely no sense to me.

[jnyork]

Griff, if I am reading your post correctly, you claim that the cases rubbed against plastic MTM box and this contact between the plastic and the brass caused the brass to fail?
.

I doubt it. No disrespect to anyone, but I doubt it.

[wecsoger]

I think in this case correlation does not imply causation.

If, and a very huge "if" the MTM boxes were bleeding some of the chemicals used in the plastic compounds it may affect the brass. But I'm seeing that as a long distance stretch to get there.

And I've kept some brass in MTM boxes for *decades* and not seen any obvious weakening. Now that I think about it, I've got some cases from the '80's I've had .45ACP and .38/357 brass in it. If there was some weakening process at work, I should have seen it in those by now. (hinges still work on those boxes too!)

Occam's Razor applies. I'd still look at headspacing first then do a chamber cast. Or borescope.

[Chuck 100 yd]

I doubt that any case failure can be found to be caused by a plastic case in that manner.
Although strange things have been known to happen I dont think this is one of them.

[Sixgun]

Been using them for 40 years. No issues.-------------6

[6pt-sika]

Been using them for 40 years. No issues.-------------6

Same here although I may not have quite that many !

[Griff]

Truthfully,

I don't think that's the cause either... but I had one case separate, no pressure signs on the case, the balance of the case fell out of the chamber, and only a light line at that point around about 50% of the balance of cases in the box. I haven't taken any pictures of the fired or unfired cases... so can only theorize! I haven't fired any of remaining rounds... but am somewhat leery of another separation.

[Pisgah]

Depending on exactly where the separation occurred, that sounds like case head separation,which will happen if a case has been resized and reloaded one time too many. Usually, it will happen only after many firings, but it can occur after only a few firings if the case is being overly resized. I am another who is very skeptical of the likelihood of the "plastic rubbing brass" theory.

[MrMurphy]

Agreed, former boss of mine had at least 5,000 rounds of .38 Super and .45 ACP handloads for competition kept in MTMs.....never had an issue with what you're describing. Over at least 30 years of competing.

[jmiller]

I've got over 4,000 rounds loaded in these cases in different calibers and some are over twenty years old. Never happened to any of them. I think it's a leap to conclude that the plastic case caused this failure mode. I've worked in quality and statistical engineering most of my adult life. It's very common for the average observer to make conclusions by observation and only seeing a few factors (or non-factors) and not seeing the root cause. In fact, the root cause may not be visible. I also worked at a large plastic manufacturer for a while and I'm positive the plastic isn't affecting the brass cases.

[AJMD429]

Depending on exactly where the separation occurred, that sounds like case head separation,which will happen if a case has been resized and reloaded one time too many. Usually, it will happen only after many firings, but it can occur after only a few firings if the case is being overly resized.

I've even had separations like that in NEW brass - evidently a bad lot years ago, but it got me worried that the gun (Mini-14) was out-of-spec. Gunsmith checked the headspace and it was ok, then a friend fired the same stuff in his Mini-14 and had one split after just a dozen or so fired. Company took the empty cases and remaining ammo back and said it looked like the brass wasn't annealed properly. Gave me a coupon for $50 though - and back in the 1980's that bought lots of 223 ammo.

[rogn]

Sounds like the history of the case is more of an issue. Either QC as mentioned, or prior contact or manipulation. Too, too many boxes out there w/o incidents. But Id scrutinize the rest of the cases in that box/lot.

[Blaine]

[sore shoulder]

Well if MTM plastic is that harsh on brass, maybe we should be making gun barrels out of it.

[madman4570]

Ray----------------------to be that type seperation you are talking about(the rubbing effect)you would have visual evidence right at point where that significant abrasioning took place. I am saying it has to be something else.(in my opinion?)

But---------ya know-------this post was put out with your best intrest at heart(you were looking out for us)---so thank you!

And to ensure your post was not in waste(any well meaning post)isn't a waste.
I have about (4) 100rd orange empty cased MTM (.223)ammo containers that have been in my Ford Escape(rear netting storage compartment with those empties bouncing around in those cases with em going bye bye in my SUV for about 5 or 6 years why those I have left there????????????
I will look them over real good and report what I find!

Thanks!

[Ray Newman]

Madman45-70: I did not have the case head separation.

What I quoted and asked about was Griff’s post in another thread on a case head separation and MTM plastic boxes.