Underwood 180gr Speer TMJ Pull-Down

[45BBH]

When I loaded for 10mm, a 180gr JHP would do 1205 fps from a Glock 20 using 8.5gr Power Pistol.  9.8gr is "only" ~13% over book max of 8.7gr.  Hmmmmmmm.  I see Buffalo Bore is using even more 10.0gr, 15% over book.  I wonder if people new how much over book these are if they would think twice?

[Patriot]

When I loaded for 10mm, a 180gr JHP would do 1205 fps from a Glock 20 using 8.5gr Power Pistol.  9.8gr is "only" ~13% over book max of 8.7gr.  Hmmmmmmm.  I see Buffalo Bore is using even more 10.0gr, 15% over book.  I wonder if people new how much over book these are if they would think twice?

Reloading books are routinely far below SAAMI max pressure for liability purposes. I don't have my info in front of me at work but I don't think the Buffalo Bore is over max SAAMI pressure.

[The_Shadow]

Alliant 2006 data shows Power Pistol powder values from 5.5" BBL as:
200 FMJ @ 7.7 grains 1,145 fps 35,600 psi
190 JFP @ 8.2 grains 1,200 fps 35,900 psi
180 JHP @ 8.7 grains 1,240 fps 34,900 psi
180 Lead @ 8.7 grains 1,235 fps 34,700 psi
155 Lead @ 9.5 grains 1,320 fps 33,000 psi
150 JHP @ 9.7 grains 1,415 fps 35,600 psi
135 JHP @ 10.6 grains 1,530 fps 35,600 psi

At these values they are far below the 37,500 psi but this is a faster powder and builds pressure fairly quickly.

[Intercooler]

How do the books establish max? Seems they vary.

[The_Shadow]

The loads just need to fit the inside the SAAMI Spec as set.  It doesn't matter if the data is published at lower values as a safety cushion. 

Pressure testing info...
http://www.saami.org/specifications_and_information/publications/download/205.pdf

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 Adverage 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.

Nothing in the sample over 40500 psi

[Filthy Phil]

I have some of this due today.
Will de-virginize my glock (perfection prolly tomorrow with it and some buffalo bore, some cor bon, and american eagle 40 short n weak powered

[REDLINE]

Will you be chronographing any of them?

[The_Shadow]

Tested in 10mm S&W1006 5" June 8, 2013
Underwood 180gr  Speer TMJ 1312 fps (failed to extract) / 1025 fps ?

I have seen this (failed to extract) a couple of times, 135 Gr @1700 with popped primer, this one and the 220 gr UW, and awhile back with the 9x25Dillon test.  I need to inspect the extractor and spring and for foreign debris behind the extractor...

[Intercooler]

No extraction problems here. Close again to the ~ 1300 I have been getting.

[REDLINE]

Tested in 10mm S&W1006 5" June 8, 2013
Underwood 180gr  Speer TMJ 1312 fps (failed to extract) / 1025 fps ?

LOL.  Another weird velocity that we'll never have an answer to.  Just irks me, but I'm better now.

[Intercooler]

It's not weird. You get these every so often and that's why shooting 5-10 shot strings tell the picture.


I think I have passed enough ammo over one to be a field service technician about now 

[REDLINE]

Maybe weird was too strong of a word for the context I used it.

Either way, in my mind, it would be nice to know the "why" to ammo that was meant to do 275 more FPS than one round achieved, didn't.

We're not talking normal standard deviation here.

[The_Shadow]

Redline, these Chronographs can even see even powder specs, the blast wave can disrupt the timing if it passes over a sensor.
BB's are easily seen and counted, if using the thing with out the sky screens, a bird or bug can trigger timing circuits.

I had about 3 readings that registered less than they should have...you guess is as good as any I suppose.

[REDLINE]

Can't really say I even have a specific guess.  Overall I figure there are really only two possibilities though;  1)  Chronograph Error for whatever reason, or 2)  Undercharged round.

I'm pretty much with you in leaning toward a bad chronograph reading.

[harrygunner]

The variations in Underwood O.A.L. affects my 1911. That gun feeds Double Tap and Buffalo Bore hollow points very reliably but rounds won't make it into the chamber with a lot of the Underwood ammo.

I'm thinking of getting handloading equipment not only to assemble ammo I'm pleased with, but to pull apart and rebuild some of my UW rounds.

Is that doable, reassembling UW rounds with carefully measured power and carefully seated bullets?