Someone explaine this to me

[gadabout]

I haven't loaded 10mm in a while and I had quite a stock on hand anyway. Loading some up and was looking for the latest data. I went to Alliant on the net and the load called for 9.3g max of Power Pistol. Thinking this was high I checked my older loads and they were at 8.0. So today I found my Lyman 49th version of the loading book and max for my load was 8.0. BOY a 1.3 difference makes you wonder what is going on. I feel 9.+ is really pushing it for this weight in 10mm but I like them light. Someone explain the difference to me. I think we have had this discussion before but not this much of a difference!!

[The_Shadow]

Craig you are working with 180 Grain Bullets?

Here are some results of Power Pistol...The pistol used, was Glock G20 with a Glock Factory 6" 'Hunting Barrel' custom ported. The OEM spring/guide rod were used.

TEST #1.1        LOAD # 10XTP180.1

Bullet - 180g Hornady XTP JHP
Case -  DT (NEW)
Primer - CCI #350 LPM
Powder - PP 8.6 g.
# of Rounds Loaded & Fired - 5

VELOCITY:
1) 1359      2) 1359        3) 1357      4) 1335       5) 1330

Average Velocity - 1344 FPS:
Average Muzzle Energy:- 722 FT. LBS.
Extreme Spread:- 29 FPS

TEST #1.2             LOAD #10XTP180.2

Bullet - 180g Hornady XTP JHP
Case -  DT (NEW)
Primer - CCI #350 LPM
Powder - PP 9.6 g.
# of Rounds Loaded & Fired - 5

VELOCIITY::
1) 1426        2)1396        3) 1431        4) 1416        5) 1430

Average Velocity  : 1420 FPS
Average Muzzle Energy  : 806 FT. LBS.
Extreme Spread  : 35 FPS

Other data using Power Pistol
Glock20/6" 180gr. Golden Saber 9.6gr. PP MV:1331fps ES-34 ME:705ft/lbs.
Kimber 180gr. Golden Saber 9.6gr. PP MV:1376fps ES-97 ME:754ft/lbs.

This is just to help you get an understanding what was observed

[The_Shadow]

Alliant 2006 data

[sqlbullet]

180 grain FMJ correct?  Assuming we are not comparing FMJ to JHP or radically different COAL, etc.

Usually load data publishers stop when they reach max pressure as defined in SAAMI spec.  That is not nearly as simple as it sounds.  The statistical model includes maximum average pressure, standard deviation, standard error, maximum probable lot mean, maximum probably sample mean and maximum extreme variation.  The definition and methods are available in most of the SAAMI cartridge pressure guides.

And, methodology becomes a factor here.  A tight chamber and rough rifling in one test barrel could account for the difference between these two datapoints.

[The_Shadow]

This is some data that was published by LEE



The data shown with pressure values is still below the 37,500 psi mark

[gadabout]

Well I guess I really stirred the pot with this one. Thanks Wade for the data I was only curious as to why the big swing but also the Alliant is published as a recipe not even max and the Lyman data is old and most rounds have been raised over the years. I like my loads light but with 10mm I just love your data speed and I may try some of those loads.  Craig

[The_Shadow]

Craig, some of the data was from 6" factory Glock barrels, the Kimber data was from a 5" barrel where they used 9.6 grains

You may want to work up to see how your pistol works as you progress with you bullets of choice...

[Papajohn]

This is some data that was published by LEE

Please bear in mind that Lee does Not do ANY pressure testing, they only use other sources, more often than not without citing them.    :'(

[The_Shadow]

Papajohn, I posted the LEE data showing Power Pistol which actually coincides with the Alliant 2006 info I also posted...  One of the sad things that Alliant no longer adds the pressure values to their loading data. 

[gadabout]

This is interesting I feel. My copyright on my Lyman 49 is 2008 and I remember I had to buy it as I had no data for 10mm in any of my many other data books!! Oh well that is life I guess and I learned I can use 8-9.5 safely for my 180 JHP loads.You just can't shoot many in a row. Ha Ha Craig