FINALLY - 5 Underwood 10mm Ammo Disections

[REDLINE]

With the help of some friends I have accumulated 5 different examples of 10mm Underwood Ammo loads and disected 4 of each.  That's 20 total rounds disected where I made note of two measurements.  Those were COL and powder charge weight.  All round were clearly loaded with IMR 800-X. 

One thing nice about disecting loads that contain 800-X is that you don't have to wonder if a couple grains of powder were stuck in the primer pocket or kinetic bullet puller toward getting an accurate weight measurement since the power flakes are very large and it's easy to tell if you've collected all of them (not that I still didn't make use of a flashlight to make sure).

All powder charges were weighed on two different scales.  One being the Redding #2 beam scale, and the other being the Hornady Digital Bench Scale.  COL was measured by both my dial and digital calipers.

After the noted bullet load is the listed range of COL I encountered in BLUE, and secondly the range of powder charge weight in RED.

UW 10mm 135gr Nosler =    1.249"-1.252", 11.4-11.7 grains
UW 10mm 155gr Gold Dot = 1.249"-1.254", 10.5-10.7 grains
UW 10mm 180gr Gold Dot = 1.249"-1.262", 9.6-9.7 grains
UW 10mm 180gr XTP  =       1.250"-1.252", 9.4-9.6 grains
UW 10mm 200gr XTP  =       1.253"-1.258", 9.2-9.4 grains

The results really make me wonder how much further they would have varied had I disected more than 4 rounds from each box of 50 total rounds.  When I grabbed the rounds to disect from each box I didn't grab any together that were next to each other, but rather some distance apart from each other from each tray of a different load.

Someday I'll hopefully be able to get out and chronograph some of the rest of them from my G20.  At this point what I can say is that I am now in no way surprised by others variance in their chronograph results, which does beg the question;  How much are pressures varying?

Intercooler says Kevin says all loads are meant to be at 37,000 PSI.  Clearly that isn't the case.  The bigger question is in what way does the PSI trend, and does it matter?

What isn't in question is the sloppy load practice in at least the 10mm loads by Underwood.

[enidpd804]

Thanks.

[Intercooler]

Interesting. Who is getting these "variance in their chronograph results"?

My own opinion on it and take it for only that... a Glock isn't a suitable platform for consistent results. What pressure data did you get?

As for sloppy loads I am reading +/- .2 grains. Is that much with Cornflake size 800-X?

[The_Shadow]

Thanks for the reporting.
Were these measured on an electronic scale?  That could explain some of the variances...
It is a difficult powder to measure from a volume measure, hand weighing makes for better results.

[Yondering]

For 800X, that doesn't look like "sloppy load practice" at all; it looks pretty darn good. +/- 0.1 gr is pretty acceptable, especially with a hard to meter powder like that. I'm a little surprised Underwood chose 800X, specifically because of it's poor metering, but looks like he's doing pretty well with it.

[Yondering]

My own opinion on it and take it for only that... a Glock isn't a suitable platform for consistent results.

Not trying to start an argument, but that's not true at all. I'm not a glock fanboy, but they are just as consistent as anything else, and the Glock 20 is one of the very few actually designed for the 10mm. People seem to forget that.

[sqlbullet]

Thanks for the work Redline.  Appreciate the data.

One thought for you in the process.

I like to weight each round assembled first, then weigh the components after disassembly.  Sum of the parts should equal the whole. That helps me catch if anything gets spilled, lost, stuck, etc.

Just a thought.

[Intercooler]

One of my lifetime sayings is : You don't know more than the manufacturers!

In Glocks case we have had more than one spell it out in written print. I don't pretend to know more than they do.

[REDLINE]

Were these measured on an electronic scale?

Each of the 20 disected rounds was first measured on a Redding Model #2 Beam Scale, and then also on a Hornady Digital Bench Scale.  Both scales agreed with each other in all 20 separate powder charges.

[REDLINE]

Thanks for the work Redline.  Appreciate the data.

One thought for you in the process.

I like to weight each round assembled first, then weigh the components after disassembly.  Sum of the parts should equal the whole. That helps me catch if anything gets spilled, lost, stuck, etc.

Just a thought.

I hear ya.  But with 800-X in conjunction with a clean work area, it simply wasn't an issue.  Not even a second guess.

[The_Shadow]

Thanks REDLINE...Good to know!  I actully like the performance of the 200XTP better with the 800X than the LongShot from my testing of 9.4 grains of each.  While velocity was about equal, I think the pressure generated with the LongShot was higher.  This was based off the SwampFox 1240 fps loadings where he used LongShot...he himself said he liked 800X better with the heavier bullets.

[REDLINE]

+/- 0.1 gr is pretty acceptable

That may or may not be true.  We don't know what UW's target charge weight is for each load.  So if the target powder charge weight is exactly in between what the results show, then yeah, argueably.  If not...

Also, to my knowledge, my random sampling is the only random sampling ever shown, at least openly.  It would be nice to see results from a couple of others too, even though I wouldn't hold my breath.  The point is, my sample size isn't all that great.

I'm not as impressed as you are, and there are still other unknowns that keep us from understanding a full picture.  No matter how we slice or attempt to discern what I've shown in this disection, we still also know that some UW 10mm 200XTP are capable of 1300fps, and there is something wrong there.

Either way, I'm glad I got to do some disecting to give us some idea of what's in'em and how much, variance or not.

[REDLINE]

I actully like the performance of the 200XTP better with the 800X than the LongShot from my testing of 9.4 grains of each.

Have you personally seen the same with any bullet lighter than 180gr?

Does 800-X make Longshot obsolete across the spectrum of bullet weights?

[REDLINE]

One of my lifetime sayings is : You don't know more than the manufacturers!

Nor do we always know less than a manufactuer.

[Intercooler]

The most scrutinized ammo ever