Author Topic: Lite loads: How low can you go?  (Read 355 times)

Teninator

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Lite loads: How low can you go?
« on: December 28, 2017, 08:06:16 PM »
Hi all,

I've been reloading handguns a long time, but never autos until now. I like loading subsonic, indoor paper target loads for 357 & 44. But I don't see any such loads for the 10. Can one use 40 data without risking too high of pressures? Looks like plenty of 800FPS-ish loads for the 40.

I'm currently loading for a Lee cast 175gn SWC. Weirdly, the Lee manual lists no loads for that bullet. The lowest in the Lyman manual are about 1050 FPS. Actual weight with lube is 162, since they are pure linotype. I have 296, 231, CFE, and Power Pistol.

Glock 20SF with Lone Wolf compensated barrel, BTW. I am aware too light a load might not cycle, but I'm more concerned about pressures. TIA!

blaster

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Re: Lite loads: How low can you go?
« Reply #1 on: December 29, 2017, 04:41:44 AM »
why don't you put a .40 S&W barrel & magazine in it?

tommac919

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Re: Lite loads: How low can you go?
« Reply #2 on: December 29, 2017, 06:06:59 AM »
doesn't have to change the mag.... just the barrel

sqlbullet

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Re: Lite loads: How low can you go?
« Reply #3 on: December 29, 2017, 08:00:29 AM »
You wanna work down from 10mm data, not from 40 data.

Velocity is determined by your initial pressure (p)  and volume (v).  The amount of pressure is determined by the ideal gas law:

pv = nRt

Where p = pressure, v = volume, n = number of molecules of gas (amount of burned powder), R = ideal gas constanct and t = temperature.

Further, Boyles law tells us that when all else is the same, pressure and volume are inversely related.  If volume goes up, then pressure goes down.

If you sub 40 S&W data into a 10mm case, volume goes up, but nothing else does.  Therefore pressure will go down, and so will velocity.  In fact, it will go down quite a bit.

This will put you in the unfortunate situation of working up without good pressure test equipment.  It would probably be fine since you are looking for light loads, but why risk it.

Use the faster powders like red dot or 231.  Use the 10mm starting loads for the bullet weight, then reduce the charge until you hit your desired velocity.  By doing this you are reducing n (gas molecules/burned powder) to reduce p and therefore reduce velocity.  This is the safe method.

When working up your load the other slight concern is getting low enough that you have a squib. This means you have to ensure there is a new whole in the target each time you pull the trigger.  If you can confirm you hit the target, take the time to open the action and ensure you don't have a bore obstruction.  In theory in an auto-loader a bullet that doesn't leave the barrel will not impart enough recoil to operate the action.  In practice we don't want our gun to spontaneously disassemble, so we check.

I would guess you are going to find that about 4.5 grains of 231 is about what you want.

Blaster, the reason not to use a 40 barrel is you then have to deal with 40 brass, small primers, and two set-ups for seating and crimping dies.  And, there really is no advantage if you already have 10mm brass.  A 40 barrel makes a lot of sense if you are going to shoot cheaper commercially loaded 40 ammo.

Teninator

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Re: Lite loads: How low can you go?
« Reply #4 on: December 29, 2017, 12:27:17 PM »
why don't you put a .40 S&W barrel & magazine in it?

Well because for one thing I have over 1000 10mm brass cases, and zero 40's. Number 2, I also shoot moderate and hot 10mm loads.

You wanna work down from 10mm data, not from 40 data.

I was kind of hoping someone here had done that already.  :))  Anybody, Bueller?

Quote
I would guess you are going to find that about 4.5 grains of 231 is about what you want.

Lyman Cast Bullet Handbook lists 5.5 of 231 as the starting load for a 175 SWC 10mm. 4.3 in a 40.

I was hoping someone had already done all of this and had some load data.  >:(

sqlbullet

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Re: Lite loads: How low can you go?
« Reply #5 on: December 31, 2017, 10:26:07 AM »
I was kind of hoping someone here had done that already.  :))  Anybody, Bueller?
...
I was hoping someone had already done all of this and had some load data.  >:(

Most guys here are looking to go the other way.  I get what you are after, and agree that the real greatness of the 10mm isn't that it can run magnum velocities and power level, but that it can also do the opposite.

But, my light load is 7 grains of Unique for about 1050 from a 5" barrel, about 980 from a Glock 29.

will965

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Re: Lite loads: How low can you go?
« Reply #6 on: December 31, 2017, 10:36:20 AM »
I have a ton of 40 once fired brass I will trade you for 10mm,lol...I will do 2 for 1 in your favor 8)

The_Shadow

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Re: Lite loads: How low can you go?
« Reply #7 on: December 31, 2017, 11:12:48 AM »
Agreed, we have all tried to push the limits of upper 10mm performance...chasing the lower end while keeping function reliability is another quest in and of itself.

The recoil system can limit the ejection and rearward slide travel and having under powered springs can allow even lighter loads to be used.   Balancing out the loadings to the recoil system will help with the tuning...
The "10mm" I'm Packin', Has The Bullets Wackin', Smakin' & The Slide is Rackin' & Jackin'!
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The_Shadow

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Re: Lite loads: How low can you go?
« Reply #8 on: December 31, 2017, 11:19:46 AM »
Another thing is the economics of lighter loads, using less powder and I use cast bullets that keep cost way down!

Powders like Red Dot, Bullseye, #2, Tightgroup, some of the LOVEX are faster burning and very small mounts can yield enough power to work the slide reliably. 
The "10mm" I'm Packin', Has The Bullets Wackin', Smakin' & The Slide is Rackin' & Jackin'!
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sqlbullet

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Re: Lite loads: How low can you go?
« Reply #9 on: December 31, 2017, 04:54:14 PM »
Yeah...Big part of the reason I didn't mention my Unique loads in the first post is red dot or 231 will make the desired velocity of 800 fps with lots less powder.

RDub01

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Re: Lite loads: How low can you go?
« Reply #10 on: December 31, 2017, 06:14:18 PM »
Hello
I played with that bullet a little in a G20-SF with a KKM 4.6"SS barrel.



All of these, with the exception of target #8 and #14, are subsonic..  Speed of sound being around 1133 fps..  Generally, 0.1grs of powder equals about 10-15 fps.  So the Bullseye load would be under 1133 fps at 6.0grs or under.  The Blue Dot load would be under at 10.0 grs. or under.

Also tried 7.0grs UNIQUE..



Seemed to like that better.

Bottom line with this is, there has to be enough pressure to work the slide for reliable feeding..
Using the faster powders at near max levels will give subsonic velocities, yet build enough pressure to work the slide well.  Your gun will tell you what it likes the best.
Have fun

Happy New Year