confusing load data

[deadeye dick]

Just installed a .45ACP convertable cyl. on my Cattleman .45LC. Looking at the data in my files

.
45ACP states for 200gr. Lead RNFP at5.1 to 6.4 Gr. Greendot
.45 LC states for 200gr Lead RNFP at 7.3 to 8.3 Gr. Greendot
Why the wide discrepancy? Same bullet. only the brass is different. Shouidn't the pressure be the same?

 

[.38 Special]

The Colt case is comparatively huge and takes much more powder to produce the same pressure. Moreover, SAAMI specs allow 21,000 PSI for the ACP and 14,000 for the Colt. And beyond that, many if not most manuals intentionally hold down pressure and velocity in their lead bullet loads, so that they don't get hate mail from tyros with leaded barrels.

Short version: you're talking two completely different cartridges which have essentially nothing in common except bullet diameter. In that light, appropriate powders and charges are naturally going to be different.

 

[Slamfire]

Just installed a .45ACP convertable cyl. on my Cattleman .45LC. Looking at the data in my files

.
45ACP states for 200gr. Lead RNFP at5.1 to 6.4 Gr. Greendot
.45 LC states for 200gr Lead RNFP at 7.3 to 8.3 Gr. Greendot
Why the wide discrepancy? Same bullet. only the brass is different. Shouidn't the pressure be the same?

Shoot those loads over a chronograph and believe the numbers you see. A tiny airspace makes a huge difference in velocity, and pressures.

 

[deadeye dick]

Shoot those loads over a chronograph and believe the numbers you see. A tiny airspace makes a huge difference in velocity, and pressures.

Don't have one.
Checked the Hogdon site Dont list GD.
HP38 is as follows
45ACP 4.4 to 5.3
.45 LC 5.9 to 8.0
Wide pressure difference between the two also

 

[Seedy Character]

THAT discrepancy is exactly why I shoot ACP, 4 -1 over .45 C.
Nearly twice as many shots per # of powder.

 

[.45Coltguy]

THAT discrepancy is exactly why I shoot ACP, 4 -1 over .45 C.
Nearly twice as many shots per # of powder.

Pretty much agree here^^^. Once I got the .45 Colt fever out of me, I just shoot a lot of .45 acp rounds thru my Pietta clone. Not always, but, enough.

 

[EricBu]

Just installed a .45ACP convertable cyl. on my Cattleman .45LC. Looking at the data in my files

.
45ACP states for 200gr. Lead RNFP at5.1 to 6.4 Gr. Greendot
.45 LC states for 200gr Lead RNFP at 7.3 to 8.3 Gr. Greendot
Why the wide discrepancy? Same bullet. only the brass is different. Shouidn't the pressure be the same?

Huge difference in case capacity. Also, 45 ACP is a much higher pressure than classic colt load. If you were to use say........C45S brass, with that same 45 ACP charge and bullet, you'd get very nearly the same velocity (and pressure) as the 45 ACP...which is higher than a traditional 45 Colt is rated for.

 

[deadeye dick]

What i'm concerned about is it safe to shoot. Ran 6 thru it and it seemed ok. Hit where i aimed and recoil seemed the same.

 

[ArchAngelCD]

Don't have one.
Checked the Hogdon site Dont list GD.
HP38 is as follows
45ACP 4.4 to 5.3
.45 LC 5.9 to 8.0
Wide pressure difference between the two also

You keep comparing 2 totally different cartridges and I'm not sure why?
The case sizes for each are VERY different in volume.

That max 45 ACP load generates 16,900 CUP according to Hodgdon.
That max 45 Colt load generates 13,800 CUP according to Hodgdon even though the powder charge is much larger.

Again, I'm puzzled as to why you continue to compare 2 completely different cartridges???

 

[AJC1]

Just installed a .45ACP convertable cyl. on my Cattleman .45LC. Looking at the data in my files

.
45ACP states for 200gr. Lead RNFP at5.1 to 6.4 Gr. Greendot
.45 LC states for 200gr Lead RNFP at 7.3 to 8.3 Gr. Greendot
Why the wide discrepancy? Same bullet. only the brass is different. Shouidn't the pressure be the same?

Think of the below bullet volume as an air tank. The 45 colt is a much larger tank and requires much more gas to fill to the same pressure.

 

[gwpercle]

Huge difference in case capacity between the 45 acp and 45 Colt ...
you can't compare the data ...
Here is some Green Dot Data from the 1976 Speer Reloading Manual #9
45 ACP : test fired in Colt 1911 - 5" barrel length
200 gr. swaged lead SWC (Speer brand)
start load - 4.6 grs. GD @ 729 fps
maximum load - 5.0 grs. GD @ 833 fps

45 Auto-Rim : test fired in 1955 S&W Revolver - 6 1/2" barrel length
200 gr. swaged lead SWC (Speer brand)
start load - 4.6 grs. GD @ 703 fps
maximum load - 5.2 grs. GD @ 803 fps

As you can see these soft swaged lead bullets were not pushed very hard in either the 45 ACP or 45 A-R . I have a feeling cast and lubed or coated could be pused harder .
Finding Green Dot data is hard ... the Speer #8 Manual has cast bullet - Green Dot data but I'm not going to list it .
Also interesting to see velocity differences between 1911 5" barrel and 1955 revolver w/ 6 1/2" barrel velocities .
Gary

 

[EricBu]

What i'm concerned about is it safe to shoot. Ran 6 thru it and it seemed ok. Hit where i aimed and recoil seemed the same.

For 45 ACP, with your 45 ACP conversion, you use....45 ACP data. When shooting 45 Colt, with the 45 Colt cylinder, use 45 Colt data....don't try and interchange the data for the two cartridges!!! It's apples and oranges, two different cartridges that happen to share the same caliber. You might as well be asking if 22 Long Rifle and .223 have the same pressure, because the caliber is close to the same, only the brass is different.

 

[cfullgraf]

Checked the Hogdon site Dont list GD.

FYI.

Not a surprise since Green Dot is not marketed by Hodgdon.

Just like you will not see HP-38 on the Alliant web site.

 

[deadeye dick]

For 45 ACP, with your 45 ACP conversion, you use....45 ACP data. When shooting 45 Colt, with the 45 Colt cylinder, use 45 Colt data....don't try and interchange the data for the two cartridges!!! It's apples and oranges, two different cartridges that happen to share the same caliber. You might as well be asking if 22 Long Rifle and .223 have the same pressure, because the caliber is close to the same, only the brass is different.

Thanks to all for all the great info. I understand completly now. Did'nt consider all the differences, now i do. This site never ceases to amaze me.

 

[25-20 WCF]

What i'm concerned about is it safe to shoot. Ran 6 thru it and it seemed ok. Hit where i aimed and recoil seemed the same.

Published data for either caliber will be safe to shoot in your revolver. It is best to start lower than maximum charges even with these low pressure chamberings.




.

 

[mdi]

The only thing those two cartridges have in common is bullet diameter and weight. Two completely different cartridges = two completely different loading parameters. I think the question is just an "I wanna know for my curiosity..." thing, but trying to extrapolate data from one to another is not wise for the average reloader...