[revo]

I searched around and saw that the Blackhawk convertible 45ACP cylinder does not need moonclips. Something about it relying on "headspace" to keep the rimless cartridge in place.

Please forgive my ignorance, but what is "headspace" and how does it keep the 45ACP cartridge from sliding forward in the chamber?

[Crosshair]

Well, the 45 ACP headspaces on the case mouth, think of it like how rimless rifle rounds use the case neck to headspace. Only the earliest 1917 S&W revolvers HAD to use moonclips. Today moonclips are used because the extractor on a revolver can't extract a rimless case and the moonclip gives the extractor something to grab. This is no issue in the Ruger convertables because cases are extracted one at a time with the hand ejector that pokes out the empties.

[JohnKSa]

WARNING! BEFORE reading farther, please read the disclaimer at the end of the post.

Headspace (in this context) is what prevents the cartridge from moving too far forward in the chamber.

Most revolver cartridges headspace on the rim.

Most rifle cartridges headspace on the shoulder.

Most autopistol cartridges headspace on the case mouth.

Headspace is also the measure of how much "play" the case has (forward and backward) in the chamber with the action closed. If there is too much play (headspace) in a cartridge that headspaces on the case mouth or case shoulder, the case may stretch excessively upon firing and can fail catastrophically. In a cartridge that headspaces on the rim, it's hard (and rare) to have excessive headspace. Probably because it would be pretty obvious if there were an obviously oversize gap between the chamber and the breech.

When you shoot an autopistol cartridge (that wants to headspace on the case mouth) in a revolver (that needs a cartridge that headspaces on the rim) you need to provide a rim. Moonclips act like a cartridge rim and also provide the benefits of quicker reloads and more sure ejection.

[cidirkona]

With a convertible, you can fold the roof back and store it in the trunk. No roof = infinite head space.

(Sorry, somebody was going to say eventually anyways. :) :rolleyes: :p :D :evil: :neener: )

-Colin

[Crosshair]

With a convertible, you can fold the roof back and store it in the trunk. No roof = infinite head space.
Do you know how hard it is to get doughnut out of a keyboard.

[cidirkona]

Do you know how hard it is to get doughnut out of a keyboard.

Nope, but I'm sure there a few officers on this forum that'd be able to tell you! :D

-Colin

Sorry #1 to the officers, I do respect your posistion, authority and risks.
Sorry #2 to revo for the thread hijack. </hijack>

[unspellable]

Infinite headspace is not always wise. My wife said, "put the top up, it's going to rain." I said, "naw, let's leave it down for while." She prevailed, I put the top up. You guessed it, five minutes later we got hit with a fence bustin' gully washer. proves you can have too much head space.

[Mal H]

Back on topic, please.

[Vern Humphrey]

The .45 ACP headspaces on the mouth -- that is, the edge of the case mouth rests on a ledge in the chamber and this ledge controls how deeply the case can go into the chamber.

During World War I, we couldn't produce .45 automatics fast enough. The Model 1917 Revolvers (the Colt New Service and the Smith and Wesson Hand Ejectors) were chambered for the .45 ACP round. The problem was to eject the fired rounds -- since the .45 ACP has no rim. Smith and Wesson developed the half moon clip -- a piece of sheet steel that clips 3 rounds together. Two clips made a full six-round load. The ejector star presses against the clip to eject the rounds.

Because of this the gap between the cylinder face and the recoil shield was greater than normal -- there had to be room for the moon clips. When the .45 Auto Rim was developed, it had an extra thick rim because of that gap.

When Ruger began manufacturing their .45 ACP-.45 Colt convertable, they got a lot of questions about the need for moon clips -- and what you printed is their answer.

The real answer is, you can't use half-moon clips in a Ruger Blackhawk -- it doesn't have a swingout cylinder! And you don't need them because it ejects with an ejector rod.

[revo]

Nice. Thanks for all the info, folks.

Wow. I had it completely backwards. So,the moonclips were designed to facilitate extraction. The ledge within the chamber serves to keep the cartridge from moving forward.

Does this mean that S&W 625's have that ledge in the chamber to keep the case from sliding forward? Same as the Blackhawk? They just need moonclips for extraction purposes, right?

[Vern Humphrey]

Nice. Thanks for all the info, folks.

Wow. I had it completely backwards. So,the moonclips were designed to facilitate extraction. The ledge within the chamber serves to keep the cartridge from moving forward.

Does this mean that S&W 625's have that ledge in the chamber to keep the case from sliding forward? Same as the Blackhawk? They just need moonclips for extraction purposes, right?

Yes. You can shoot .45 ACP in revolvers without the clips -- many years ago I had a Colt M1917 that I shot that way -- fortunately, not in the mud and muck of the trenches, so my cases mostly fell out by themselves.

The exceptions to this were the very early Colt M1917s, which had no ledge. They would not function without the clips.

[Tom C.]

I have a Model 25-2, a Model 625-8JM and several SS NMBHs in .45 Colt with spare .45 ACP cylinders. The problem with .45 ACP in a revolver without clips is the variability of the chamber depth, headspace if you will, and the extreme variability of .45 ACP brass length, particularly after it has been reloaded several times. Long chamber and short case can result in a misfire. Usually isn’t a problem with new factory ammo.
One answer to the problem is to use .45 AR brass for handloading. It works fine in the double action guns (it was designed for them after all), and the Ruger .45 ACP cylinder can be trimmed to use .45 AR brass in addition to retaining the capability to use .45 ACP brass. Similar loads in .45 Colt and .45 AR seem to favor the AR ammo for accuracy and consistency due to the smaller case. .45 AR is for bullets of 250 gr. and below. The .45 Colt really gets into its own with 300 gr. bullets.