Underwood case blowout over on 1911Forums

[Bro KV]

So is this condition relevant to Glocks?

[sqlbullet]

Glocks operate differently.  Same principle, but evidence is certainly that extreme spreads drop and accuracy increases with heavier springs.  Therefore the anecdotal evidence is that there is a difference in how the Glock operates.

Comparing the two action, my 1911 barrels swing down and unlock after some 1/8" rearward travel or so.  The Glock begins unlocking and swing down immediately it seems.

[pacapcop]

I think a 170 JHP would be nice in the line up.Im even considering the Delta Load in my 1006 for carry.First Generation 170gn Norma 1400 fps 740fpe out of a 5 inch barrell then reduced to 1300 638fpe 2nd generation.Id say thats plenty to do the job and safe.

[REDLINE]

Regarless the operation differences between 1911s and Glocks, there's still something to be said about timing with how and when each setup begins to unlock, especially between the difference of a 30,000 PSI 10mm load, and another that ranges from 37,500 PSI (SAAMI maximum average pressure for the 10mm Auto) to 38,700 PSI (SAAMI probable lot mean for the 10mm Auto). 

Then take into account that every now and then IMO a Underwood 10mm load easily surpasses 38,700 PSI. 

To put things further into SAAMI perspective, SAAMI's maximum probable sample mean (the MAX PSI that should neither be tested beyond in any platform or have ammo developed beyond for retail sale, and means no ammo should actually EVER "average" this pressure level) for the 10mm Auto is 40,500 PSI.  I believe every once in a while an Underwood 10mm load is bumping this level, hence issues.

[Intercooler]

    The 1006 and Match have yet a different barrel lock-up still correct?

[sqlbullet]

Yeah.  All are modified derivative of the browning tilt lock, but different.

The 1006 and Witness guns follow a path profile very similar to the 1911 though.  The Glock begins to disengage a bit sooner I think.  I don't have them right here so I am going off of memory.

[The_Shadow]

People are quick to assume that it is Underwood's ammo..better QC is still an option. 

I still question the Star Line brass at the Underwood level of performance with a slight lack of case support!    It is a softer brass alloy and seems to stretch, flow and even tear at the upper limits of 10mm performance and pressure.

Does Star Line even test its product to some sort of pressure test standard?
Does Star Line brass test to the full pressure of true 10mm loads with a slight lack of case support?   
Does the Brass as made by Star Line meet the SAAMI criteria of pressures for 10mm? 
Does Star Line do destructive pressure testing?

Example of 205 10mm pressure MAP
The specific loads of the test have to fit the MAP set by SAAMI.

Here is a typical MAP as set by SAAMI
Nominal Mean Instrument @ 15 feet with =/-90 fps from test barrel
Maximum Average pressure MAP of 35700 psi
Maximum Portable Lot Mean MPLM of 38700 psi
Maximum Portable Sample Mean MPSM of 40500 psi

The ammunition in test (10 rounds) would need to fit this established profile.

So now if Underwood's ammo fits this MAP, then the brass he uses needs to also comply as well...This would also mean it needs to conform to all chambers of commercial guns and viseversa.

If the brass is made to a lesser pressure tolerance, with respect to lack of chamber support, then it would seem to be out of spec.

Underwood has several options...
He used Star Line for years and now has brass marked with his company name, not sure if Star Line is his supplier since the change.
1.) Change the load pressure values to fit the brass pressure profile with respect to chamber support.  He did this for Delta Elite guns...
2.) Change to a brass with better pressure specs. With attention to the area exposed with the lack of chamber support.  Not likely...but it could be an alloy change, internal dimensional change or both.

In my opinion, the brass needs to remain unchanged at the 37,500 psi pressure level and maybe start to expand at the 40,500 psi and not SMILE or blow out.  Of course different chambers will show different results...

[Intercooler]

None of my Underwood brass says Underwood 

[sqlbullet]

I posed the general question to starline via their feedback form.

[REDLINE]

Of course different chambers will show different results...

That said, no handgun brass cartridge case was ever designed to contain the SAAMI probable lot mean (38,700 PSI for 10mm Auto) pressure of any handgun cartridge I've ever heard about.  And there's no question Starline Brass does that in any barrel with enough case support with zero issues whatsoever.

[DM1906]

Thanks for posting the pics Bro KV!

It's hilarious to me that Wilson Combat would consider their barrels to have full chamber support.  IMO they aren't even close let alone being seriously hogged out at the chamber mouth.  Overall, I can't see that they offer any better support than a G20.  Don't get me wrong, I'm not saying they don't make a quality gun overall, as I consider them second to none in the 1911 world.  That said, their 10mm chambers offer nowhere near full case support!

And it's not just WC either.  I have yet to see a 10mm barrel outside of a T/C Contender that has full chamber support.  Some, like my Storm Lake barrel are very good, but anything less than 100% IS NOT full support.  Kimber barrels are the closest to full support I've seen, and they aren't full support.

10mm TC and the revolvers have FULL chamber support.  None of the auto's do.  Some come closer (Kimber) than others (CDE), to compare extremes.  WC falls somewhere in the middle.  In any case, this is only an issue when exceeding ANSI/SAAMI specs.  Case bulge, and even "smiles", are normal for some chambers, including Glock, and especially Colt DE's, at full pressure.  This can be an acceptable level of full power and reliability, at the expense of unusable brass..  There's a reason why cases tend to shorten when fired in auto's, and lengthen in revolvers (and TC's).  It's SOP.  The TC and RBH will withstand repeated pressures well beyond 54K PSI.  64K PSI, theoretically (I haven't pushed them that far).  Cases in my RBH will actually separate at the wall, just behind the bullet seat depth, at "Ruger Only" loads, if the cases are too short (but still within the acceptable range).  These are fun to shoot, a few times (as much/more recoil, compared to "Ruger only" .45LC and .454C).  Ultimately, "fully supported chamber" is a relative term, with auto's.  The Kimber chambers I've seen are the "fullest", but still not up to "full".

In other words...... Yeah, I agree.

[DAVIDF]

Intercooler,

Did Kevin seem to be interested in producing some slightly reduced or "original" loads. I would like to seem him release some of his Delta Elite loads or something similar with 180gr TMJs, Gold Dots, or XTPs or 200gr TMJs or XTPs. I'm not sure what bullets are actually available in 170gr, so a load that exactly duplicates the original Norma may not be that feasible or appealing.

[The_Shadow]

Intercooler,

Did Kevin seem to be interested in producing some slightly reduced or "original" loads. I would like to seem him release some of his Delta Elite loads or something similar with 180gr TMJs, Gold Dots, or XTPs or 200gr TMJs or XTPs. I'm not sure what bullets are actually available in 170gr, so a load that exactly duplicates the original Norma may not be that feasible or appealing.

I know handloading is not everyone's cup of tea, but the benefits of being able to handload exactly what you want, has its rewards! 

[DAVIDF]

Yes, I agree totally. I handload for my 44's & I don't approach max in those. I don't see a need to with the 44 anyways as I can get plenty of velocity for my needs without pushing the limits.

I am new to the 10mm & Glock 20. I will probably handload for it once components become easier to find. I won't be pushing the limits with my own loads for the 10mm either.

In the meantime I will be relying on Underwood for 10mm loads as well as some 9mm.

I have been learning a great deal about the 10mm from all of you on this forum & appreciate it very much.

[The_Shadow]

Be sure to look in this section for the commercial ammo pull down information for what is being used and the as weighed amount and type powders.  Very good information for what's being sold and tested by several guys...