Short .45 ACP for Italy

Can anyone give me the background on the Short .45 ACP made for Italy by Hirtenberger, Austria. The standard .45 ACP has a case length of 22.83mm, but this “Short” version is 21.61mm. Headstamp is “HP * * 45 HP”. Does this round have a special name?

look at the 45 HP makers topic,you will find some news and pictures
Here in Italy this round is called “45 HP”,and was intended to be used in pistols originally chambered for the 45 ACP,because the american ordance was considered “for military use only” here until 1996.It dates back the first 80’s.
The only difference between the 45 hp and the 45 acp is the case lenght.
OAL,types of ball etc. are the same.
It is called 45 hp because was invented by hirtemberger patronenfabrik.


Go to the “45 HP ammo makers” topic.


Pivi–You say the only difference is the case length and that O/L is the same as the standard .45 ACP. Mine is not. The standard .45 ACP O/A is 32.13mm. My .45 HP is 31.2mm.

Sorry,I meant that the maximum cartrige lenght is the same.
If 32.13 mm is the maximum SAAMI or CIP cartridge lenght,this will be the maximum lenght of a 45 HP round too.However there are a lot of 45 acp loads whose lenght is less than 32 mm,so you will find some 45 HP loads whose lenght is less than 32 mm (there’s a little difference in lenght between hirtemberger and fiocchi loads such as between SWC or RN loads made by the same factory).The 45 acp pistols were modified simply putting a steel ring in the chamber so that the longer american case couldn’t be chambered.
I should have some articles about 45 hp ammo somewhere.If I will find them I will post the scans (unfortunately they are written in italian)


Most of the history is on the previously-cited thread and doesn’t need to be repeated here. However, the cartridge was introudced c.1984 by Hirtenberger.

Measurements of actual specimens in my collection for OAL are:

HP Ball FMJ RN 1.227" 31.147mm
Geco Ball FMJ RN 1.229" 31.15mm (Brass case)
Geco Ball FMJ RN 1.226" 31.11mm (Nickeled case)
Geco Lead SWC 1.203" 30.52mm
G.F.L. Ball FMJ RN 1.220" 30.10mm
G.F.L. FMJ SWC 1.196" 30.06mm
HP FMJ RN Proof Ld 1.221" 30.10mm (Knurled Rim)

“Handbuch der Pistolen- und Revolver- Patronen” by Brandt shows the nominal measurement spread for OAL as 1.220" - 1.229" (31.00mm - 31.20mm). This likely doesn’t take into account the semi-wadcutter bullets. Only Hirtenberger is shown as a maker, so the measurements may be from several specimens of only that brand. Brandt lists “11.4 x 21.7mm” as a synonym to “.45 HP” for this cartridge.

The .45 HP is a shorter over-all length cartridge than the .45 A.C.P. in loadings with bullets of similar shapes and weights. It is not enough shorter to cause feeding in a reliable pistol designed, including the magazine, for the .45 A.C.P. cartridge and converted to .45 HP by means of a new barrel or a sleeved-chamber in the original barrel.

I do not have any Hirtenberg or Fiocchi catalog that shows this round, that I could find. This may be due to most of my own catalogs being export versions, and this cartridge was never sold in the United States to my knowledge. There would be no use for it here, of course. A Geco German- language catalog from 1994 shows the FMJ RN version with a 230 grain (14.9 grams) FMJ RN bullet with a muzzle velocity of 260mps. The lead SWC version weighing 200 grains (12.7 grams) is shown at 280mps. In the case of the FMJ RN load, this is only slightly lower than that shown for their own loading of the 230 grain FMJ RN version of the .45 A.C.P. at 270mps. The effectiveness of the two rounds, .45 HP and .45 A.C.P., would be about the same in the real world.

I will give you some info about the performance of this caliber…


Would it be possible to safely fire a .45 HP round in a .45 ACP Chambered pistol?

Falcon–The .45 ACP headspaces on the casemouth. Since the .45 HP is about 1mm shorter I would doubt the firing pin would reach the primer.

You’d be shocked how far a standard length M1911A1 firing pin can reach.

Dan–You may be right. I know very little about guns. But, I would think the relilability of the .45 HP in a standard .45 ACP gun would be marginal at best. Firing SOMETIMES and not at others.

I’ve successfully shot a magazine full of .40 S&W out of a 10mm Colt Delta Elite. There is a much bigger difference in case length there.

BTW: I don’t recommend this practice. I was merely testing to see whether it could be done.

I would never recommend firing the .45 HP in a pistol still chambered for the .45 A.C.P. Yes, it could work once, ten time, a hundred times. Or, it could severely damage the pistol and perhaps the shooter’s hand. Only the extractor would be holding the round in the proper relationship to the face of the breech. The same goes for firing .40S&W in a 10mm. My opinion, but shared industry wide in the firearms industry, and by SAAMI. These rounds are NOT interchangeable.

Oh, I certainly agree. .40 S&W cases do not look very healthy after being fired in a 10mm pistol. In retrospect, I’m kind of surprised that I didn’t blow a primer or have a case head failure. My curiousity got the better of my judgment at the time.

FWIW: My friend Dean Speir has an article on the hazards of firing the .40 S&W in a 10mm chamber on his website “The Gun Zone.” (TGZ also hosts some of my articles.)

45 HP,230 grain FMJRN by fiocchi data: