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Sti Trubor Blowd Up w Autocomp


fastshooter03

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I am puttin a new top end on a stock STI Trubor 38 super for a local open shooter.  It was blown up using 8.5 Autocomp and 115's.  Only 3-4000 thru pistol.  Anyone else heard of this happening?  He pulled the rest of that batch and found no abnormalties and no bore obstructions.  Peeled the top of the chamber.  Just curious as I remember something about Autocomp being faster than it's supposed to be.

 

Nick

 

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39 minutes ago, jcc7x7 said:

I'm at 7.4 grs of AC with 115 and getting 173-75 PF

Wonder why he was at 8.5 of AC

8.5 WOW

I run 7.8 WAC with 115’s in 9mm. The OP mentioned 38 super.

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7 minutes ago, HoMiE said:

Bullet setback? 

Something had to happen. I see people commenting about how many guns are blown up by WAC but by most standards it’s a pretty safe Open powder. 

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6 hours ago, Sarge said:

I run 7.8 WAC with 115’s in 9mm. The OP mentioned 38 super.

 

6 hours ago, Broncman said:

Ahhh.. Got 9 Major on the brain. 

Yep, didn't read it very well

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Tough for a bullet to "setback" when there's 8.5 grains of powder
under it - that's a pretty full case.    ???

That’s not all that full in a 38 super is it? I’ve heard of guys well over 10 grains with other powders.
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8.5 grains of WAC in 38 super sounds about right for 173-175 PF in a TruBor barrel.

My Trubor barrels are quite a bit slower than my KKM's or Schuemann's.

 

Also, I've cracked 2 slides in open so far... both while using WAC.

Doesn't prove anything of course, just an observation.

Haven't loaded with WAC since last spring. Only loading AA7 or 3N38 for open now.

 

 

 

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On 3/12/2018 at 5:53 AM, Hi-Power Jack said:

 

Tough for a bullet to "setback" when there's 8.5 grains of powder

under it - that's a pretty full case.    ???

In a 38s case a 115 could set back a lot.  Wac don’t fill the case all the way and the 38 is a much longer case 

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Must remember that per the national equipment survey most of the open shooters are running WAC or CFE (like 60+% IIRC)so most of the bad stuff that happens when we mess up will happen with that powder. it was most likely a over charge, most likely not duplicated in the rest of the loads he pulled because it was a mistake that got missed,

stuff happens 

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2 hours ago, 4n2t0 said:

I've yet to see any definitive proof that bullet setback can cause a catastrophic failure. It's a term that gets thrown around when people can't explain or understand how they f*#k3d up.

My experience loading 9 major for a short throated barrel with a variety of powders supports this with one exception.

 

True Blue powder responded to reduced case volume with non-linear pressure & velocity increases once you crossed the 'line'.

Evidenced by flattened primers and violent recoil characteristics with only minor shortening of OAL. One more reason to choose your components & OAL first, then work up your load incrementally from that. 

173 PF @ 1.150, primers fine,

175PF @ 1.130, same charge, primers flat, recoil violent.

 

I've observed minimal difference between 1.130 and 1.165 OAL loads with WAC, HS-6, 3N38 & AA#7 in my barrels with 115 MG JHP's loading to a 172-173PF target.

 

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4 minutes ago, BiggMike said:

In 9mm major, I played with CFE but it felt like it was too hot. I went back to HS-6; I know it is dirty but it does work.

 

I too have found even though WAC and CFE make the same velocity with the same charge, CFE 'feels' a little hotter.

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2 hours ago, kneelingatlas said:

 

I too have found even though WAC and CFE make the same velocity with the same charge, CFE 'feels' a little hotter.

I've come to the same conclusion,  maybe it's the eraser "Pixie dust" that does make it feel harsher.

 

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