Friday, March 08, 2013

Geek KaBOOM! Part II

I heard from my gunsmith today about the STI EDGE (10mm) which blew a case last weekend. 

Actually, I had some information earlier this week, when I took it in to Rob's shop for an evaluation.  Apparently, the cause of the problem was that a case split from side to side ... no definitive cause of that event .. and the case bulge prevented the slide from cycling.  I still don't know the cause, whether from fatigue of the (x number of many times reloaded?) brass or an overcharge of powder.  I didn't see any problem with the brass when I inspected the loaded round, and I doubt the overcharge.

Here's what Rob had to say:
Got your pistol apart. It was a bit of a challenge to get the barrel and slide apart (due to brass flow), but was able to do it and I was successful in removing the entire case intact.

The grip is destroyed. It is cracked in at least two places, the worst being split all the way through at the rear of the magwell. It will need to be replaced.
Barrel: It appears the hood is bent up at the rear, causing it to drag significantly in the slide when removing the barrel for cleaning. When I reassemble the slide, barrel and frame, the slide operates freely. But there is less room near the front, so when removing the barrel from the slide, the bent hood becomes an issue. It is likely not safe to use and should be replaced.

Theory: I cleaned the barrel for inspection, and noticed when I drop a live round in the chamber, there is significant play side to side, but even more important to me is that the case drops too far into the chamber. I probably shouldn’t say anything until I know more, but I have a hunch there may be a headspace issue. If I am right, that could have (and likely would have) contributed to a case head blowout such as you experienced. I do not have headspace gauges for 10mm, an issue I intend to resolve. Once a “Go” and “No Go” gauge arrives, I will be able to determine if headspace is a contributing factor.

Further theory: Often a double charge causes massive, catastrophic failure. You didn’t experience this, which again leads me back to headspace as a question. I don’t know about bullets slipping back into the case and what the likely result of this condition is. I know bullet slip will significantly increase chamber pressures, but I haven’t seen enough guns in that “known” state to see what the end result was.

The important thing is that I have not found any noticeable damage to the slide or frame. I haven’t fully inspected all the small parts, but first glance tells me they are fine, even the extractor. The sear spring is bent, but it  looks like someone peened the side of the sear spring to tighten the fit to the frame, and in doing so, bent the sear leg a little. It is repairable, but the cost of a sear spring makes me think replacing it is a better choice.

If head space is an issue, what about warranty with STI? I don’t know how long you have had it, how many rounds, or if they void their warranty when handloads are used. Those are questions you’d need to find the answers to. I don’t think warranty is a likely option, but if headspace is the culprit, that is nothing you could have created yourself without a chamber reamer.

It will be several days for chamber gauges, but I’ll let you know what I find out then.
I replied to his email, saying (basically) that I wanted to fix the gun, but I need a parts-and-labor cost evaluation before I decide.  I would like to make the gun whole again, to restore it to the original condition.

Beyond that, I'm thinking about adding a C-more sight, because it is becoming increasingly difficult for me to use the gun competitively because .. damn!  I can't see the iron sights very well any more!

If the only added cost is parts and installation to add a dot-sight, I'm pretty happy with that.  I love the gun, and I know I'll feel more comfortable being able to see the sights and the target.  Moving to OPEN DIVISION with a LIMITED DIVISION gun isn't the wisest or most cost-effective solution, but it satisfies many of my personal criteria, so perhaps I can live with the expense if it resolves my current vision issues.

I've asked Rob to give me a price list for restoring the gun to the original condition, vs the same with the added expense of adding a C-more sight.  I still have The Beloved Kimber if I want to shoot in Limited (or Limited 10, or Singlestack) Division, but I think that the Edge is a superior pistol.

The question remains, whether the Edge is safe to shoot.  I still don't know why the ammunition was suddenly not "safe to shoot", but I have to say ... if my guns have to blow up I'm glad I have the 10mm STI Edge in my hands.  That may not make much sense to you, but I bought it because I thought it was a platform which would be "safe" even if the worst happened.

Well, "The Worst" happened, and I didn't get hurt.  I don't know why or how yet, but I do know that my confidence in The Edge is stronger than ever.

I'll keep you posted.


Anonymous said...

Hoping that the expense of restoring your edge to good health is not too excessive.

Rivrdog said...

Everything that happened took place in the chamber. Your smith says you have a flat-oval chamber and may have excessive headspace. New barrel should fix all of that.

Sounds like you've skirted the edge of disaster for a while, and that bad chamber would also be very hard on your brass, shortening it's life to well below what you were loading it to.

Scrap the barrel, scrap all your brass, and you should be fine. Only thing, the added cost of several hundred new hulls puts the gun in the "not econmical to shoot" category, most likely.

Anonymous said...

It looks like you may want your new barrel to be chambered for 40 S&W. Cheap readily available brass, and with the newer reduced PF you can safely make major without having to load to high pressure. In fact, you can allow a fudge factor and still keep pressures below 20,000 psi. There is a reason the 40 S&W is so popular in limited.