A little 45ACP accuracy testing

[captaint]

Where to begin. I'll tell you now, though, this is gonna be a letdown. I decided to do some accuracy testing in my 45ACP's. Where to begin - with the brass. So I started measuring length on some mil WW once fired brass. Very nice brass too. Got most cases measuring around .890. Then I separated into three groups. Two thou shorter, two thou longer and within four thou of .890. No problem. Now, it gets interesting. We've always heard and said "yes, the 45ACP headspaces on the case mouth". Well after trying the plunk test on just the empty brass, this is not even close to being correct. My cases are around .015 short of passing the plunk test. And, I used the longest group of cases. Most were around .895. So I measured some commercial Federal cases. They were all well short of .890. Initially, I was hoping to get a group of brass that would plunk test right on the money for starters. That is not going to happen.
Now, I can't be the only guy that ever noticed this. I'm sure many of you folks have seen the same thing. Also, I don't think my barrel that I measured with is much different from yours.
So, what's the deal ?? I mean, I don't have a problem headspacing my ammo on the boolits. Always plunk tested any time I changed a load or boolit, so no big deal. Also, I tried this with brass that was sized and not. Any opinions ?? Mike

[Forrest r]

The 1911 doesn't headspace on the brass, they headspace on the shoulder of the bullet. That's why some bullet designs do better than others. You'll see ia a lot of posts where the reloader likes to have around 20/1000ths of the bullets shoulder sticking out of the cases.

Or 100's of reloaders all came up with the same oal for the same bullet.

Countless 1000's of reloaders have come up with this for the h&g 68/68 clone.

67333


Note the 20/1000th's lead shoulder sticking out above the cases. That's what sets the headspace on the 1911 in 45acp.

[captaint]

Forrest, you are absolutely correct. And I do the same thing as you do and, I assume, everybody else too.
So - Why then (and you must have heard this a million times also) do we say "the 45ACP headspaces on the rim" ??. I'm thinking we should just get over it and say it headspaces on the boolit - because it certainly does !! Thanks Mike

[pipehand]

Forrest r, I noticed you use the 1.250" length with the # 68. Me too, works great.

The plunk test is to make sure the bullet is not seated out too far, preventing the round from chambering, or if the round is too fat. My experience with 45acp pistols is limited mainly to 1911's, but I know my copies will headspace off the extractor before they headspace off the mouth of the cartridge. Even new brass is too short. I vaguely remember reading an article on the subject, but can't recall the publication.

Whatever it headspaces off of, it's a very forgiving cartridge.

[captaint]

Oh, yeah. I love the 45ACP. Shoot it more than anything else. I was actually hoping to find 50 nice long cases that would pass the plunk test empty, and start from there for the testing. Guess I'll use the cases that are close to .890 and go from there. We have 4 or 5 really great boolits for this caliber. I still want to try and see (in my guns anyway) which one shoots best. It'll be fun, either way. Mike

[w6br]

Ok, I then have a question?? What do you do, when you are using a FMJRN bullet?? What do you headspace that on??

Ron

[btroj]

Ogive of bullet into lands.

[captaint]

W6br - Not trying to be smart, but I don't. Haven't bought or loaded a jacketed bullet in years. My only experience with the 1911's and the 45ACP is with boolits. I would assume, however, you could load and plunk test the jacketed the same as the lead. Mike

[captaint]

w6br - Just remembered I have an old box of Rem Mil 45 Ball downstairs. Dropped on in the same barrel I have been using. It dropped down .015 too far. Just like the empty brass. Now, certainly it will fire and function just fine that way. I'm actually glad you asked that question. Interesting. Mike

[35remington]

Most of the time the cartridge will headspace off the bullet or the case mouth......much more so than headspacing on the extractor using the case's rim near its base. The extractor/breechface gap on 1911's is such that it is intentionally toleranced to prevent rim headspacing the vast majority of the time, even given short brass and longish chambers. This gap from extractor hook to breechface is larger than most automatic pistols.

http://i6.photobucket.com/albums/y228/johnnyrem/DSC02342.jpg[/URL]

Note the relatively enormous gap that the cartridge must be driven across for the extractor hook to headspace. It's quite a lot, and it's more than most chambers and most cases will allow before the case mouth strikes the stop shoulder in the chamber.

I did a considerably lengthy post on this awhile back. Whether your pistol headspaces on the extractor or not is a matter of simple measurement. The measurements will reveal that most of the time extractor/rim headspacing doesn't happen. If an argument is to be made for the rim headspacing on the extractor the 1911 is not a good candidate for making one's point. Other designs are more likely to do this than a 1911.

Also keep in mind taking the barrel out and judging whether the rim is flush with the hood or not is not a judgement of headspacing. Headspacing much take the breech into account as well, and some, if not most, 1911's are fitted with some barrel hood/breechface gap.

So we're back to case mouth or bullet headspacing the round most often, just as it always was.

[35remington]

BTW, captaint, if your cases are 0.890" in length I'll guarantee they'll never, ever headspace on the extractor. They'll headspace on the case mouth or bullet first.

What is your hood/breechface gap, if any? I can just about quantify how short a case it would take to headspace on the extractor if you can tell me this dimension. It's a much shorter case than likely any you have in your collection.

Whether a FMJRN bullet can headspace on the bullet or not depends upon the curve of the bullet's ogive. If the curve is a 2 radius like most ball bullets it is common for the cartridge's overall length to exceed the 1.275" maximum for the 45 ACP before it headspaces on the bullet. Loaded to the more correct 1.265" it probably is headspacing on the case mouth. Since I cannot speak for all FMJRN's it is possible some with a nonstandard radius will headspace on the bullet before the case mouth, but these would look different from most military ball or commercially available offerings of 230 FMJRN's like that from Hornady.

[pipehand]

35Remington- what you're saying is that when the firing pin hits the primer, the case is driven forward, and the casemouth stops it? When that happens, there is considerable space between the cartridge head and the breech, so that by design, a 1911 is made with what we would call excessive headspace in , say, a Mauser rifle. But it works, and works well. And a 1911's firing pin protrusion is way long unless it is hitting a primer.

In an effort to find the article I wrote about earlier, I looked through the 1981 NRA Handloading manual I have. It says in one place, that the rimless cartridge headspaces off the casemouth. And in another, that the cases are usually too short, and that SWC bullets should be seated out to provide a shoulder so firing pin impact wouldn't be wasted.

I was wrong about the extractor thing.

[35remington]

What I am saying is the round most often headspaces on bullet or case mouth. Even if the bullet is seated deeply the 1911 will headspace off the case mouth far more often than the extractor. Yes, there's a lot of gap between case and breechface when headspacing off the case mouth, comparatively, and it doesn't particularly matter in the 1911. The extractor hook distance from the breechface sees to it that it doesn't headspace the round. If it does, it is only rarely.

What I am saying is extractor headspacing doesn't occur as often as many claim it does. Norm Johnson's commentaries on this matter are quite off base, for instance, and he's usually a very knowledgeable commentator. Measuring will clear this right up, but few bother to do it, even though it's not that difficult to figure out.

Take the OP's measurement. I presume he was suggesting his cases didn't "pass" the plunk test (actually they did because, as you pointed out, it's a clearance/functionality test not a "must be flush" test) because his 0.890" cases were 0.015" below flush with the barrel hood. If, assuming if, his hood is flush with the breechface when locked up that means he has 0.007" headspace over the SAAMI maximum case length of 0.898" which is pretty much in the short/middle side of the headspace measurement spectrum. Adding a reasonable 0.004" gap between hood and breechface means he's pretty much exactly in the middle. Which is what we'd expect in any bell shaped curve.

Given the typical distance the case is held away from the breechface in a 1911 if extractor headspacing comes into play, the case would have to be about another 0.020 to 0.025" shorter than it is (0.890") or around 0.865 to .870" to headspace on the extractor in his gun, with the actual figure most likely needing to be closer to 0.865." If it has the mid spec headspace measurement, that it. If it has no hood/breechface gap the case would have to be shorter yet to headspace on the extractor.

I've measured a lot of 45 ACP cases and even the short ones aren't that short.

Measure your own dimensions to determine. Extractor headspacing if the bullet does not? Not very often. Most often if the bullet does not headspace the round; the case mouth will do so if bullet seating depth allows it.

This is exactly as it was toleranced to happen, so we shouldn't be surprised that it does happen that way in a 1911.

[pipehand]

"This is exactly as it was toleranced to happen." Which is testament to JMB's genius. A cartridge and pistol designed as a system , where nothing fits perfectly, but everything works perfectly together. How does all that work out when the platform is chambered for say, 10mm, or 40S&W? Do the tolerances have to tighten up because the operating pressure doubled?

[35remington]

I can't say what the gap from the extractor to breechface is when the 1911 is in 40 or 10 format. A little measuring would be in order here to discover that truth.

[gray wolf]

35 REMINGTON and I go on and on about this often times, lately he has left me alone when I dispute some of this.
If we look at the picture we see the case head has been picked up by the extractor hook and at that point would be in the barrel. Yes the case is not being held at that point by the extractor and at that point it looks like the extractor is-- lets say at rest for a better way of saying it.
But the case head seems to be against the breach face, yes I know the breach face barrel interface is not exact and could be .004 shy. So why is the so called short case not deeper into the barrel ? answer, it's being held in position by the front band on a SWC that has the correct OAL. I don't think the inertia of the firing pin strike will drive it forward enough for the case mouth to contact the rim in the chamber, thus over coming the front band contact of the rifling.
Setting up a SWC bullet in a 1911 so the case head is flush with the end of the hood is a well accepted way of establishing OAL for a 45 ACP SWC in a 1911 it also helps with consistant ignition. Depending on how short the case was I'll bet if the slide was closed on an empty short case the forward inertia of the slide would drive the case forward and depending on how short it was, it may or may not reach the extractor hook, But the extractor would be there as a stop gap for a very short rare case and hold it within the tolerance range of the pistols design.
For other shaped bullets I guess I agree that the case would be driven forward
and MAY OR MAY not have the case mouth head space on the shoulder in the chamber. Again if the case was extremely short the extractor hook would hold it in speck.
I beg to say that if the extractor hook was not there a very short case could fall short of a good primer strike, at best ignition will or could be less than ideal.
Did it all come together for ball ammo and a pistol that was designed as a combat pistol ?
I don't thing many would say no to that question, of course it excelled as a combat arm.
That's my story, it makes perfect sense to me and I am sticking to it.

[35remington]

Uh, gray wolf, you're tilting at windmills here. The round will indeed headspace on the bullet when the case is held against the breechface by the bullet's shoulder bearing against the leade. That's not my point.

Reread my posts. Tell me the part you didn't get and I'll try again. Please read the first sentence of post #10. Please read the first two sentences of post #13. Still feel like arguing the point?

The point was simply that extractor headspacing occurs less often than bullet or case mouth headspacing. Because the extractor is quite a ways from the breechface, and does not prevent most loaded rounds from being headspaced by the case mouth if they don't headspace on the bullet. Ball ammo is an example of this.

Even if the extractor was not there, and the case was very short, the case would fire perfectly well. Because the firing pin goes well forward of the breechface on a 1911. Further than even a ridiculously short case can "get away" from.

Look for yourself.

We have nothing to discuss, really, as my points have nothing to do with yours. I'll "leave you alone" because you're not arguing about anything that I said previously. I'm certainly not afraid of any points you are making; mine stand up perfectly well in comparison and are not the point of dispute.

I also think you need to look at the picture again to get my point, as it's simpler than you're trying to make it. It simply shows how far the case must be forward of the breechface to be headspaced by the extractor......it's a long ways. Far enough that extractor headspacing is quite rare, as it's toleranced larger than most cases and most chambers.

[gray wolf]

Now your being defensive, I don't totally disagree with your findings and I certainly don't thing that Mr. J M Browning put his pistol together wrong.
Thank you for acknowledging that what I said about the S W C head spacing on the front of the
bullet when it's OAL is set up correctly. I think that's the point I was mainly trying to get a cross.
You can have all the rest of it. You win, OK ? I didn't mean to ruffle your feathers.

[35remington]

"..........lately he has left me alone when I dispute some of this."

There was nothing to dispute. My points were exactly correct as written. Glad you agree.

[captaint]

Wow - This finally got interesting. Good. I don't see any gap between my barrel hood and breechface. And I'd like to see, at least in my guns, headspace other than on the boolit...
Mike

[35remington]

captaint, if there is no gap between barrel and breechface and given what you've mentioned so far it appears that your headspace measurement isn't on the long side (as most guns are not) and extractor headspacing is unlikely save for abnormally short cases.

If case length is known, you can measure your headspace directly or indirectly. The direct method is to take the barrel out and measure from inside step of chamber shoulder to hood if your hood fits the breechface with no gap. Due to wobble in handling the depth gauge portion of the calipers you'd be within a thou or two of correct measurement but in effect that's close enough.

To see if you are headspacing on the case mouth or not, drop empty case into chamber and measure gap between case and hood. Note dimension. Then seat the bullet in the very same case to your chosen depth and note if this dimension has changed. If it has not, it's headspacing on the case mouth. Some HP's and ball ammo are most likely to do so as often the full diameter of the bullet is mostly inside the case. Most SWC's have some shoulder showing and will headspacing on the bullet depending, of course, on how much shoulder is sticking out of the case and how long or short your leade is.

Guns vary. My 1911's average longer throats (or more gradual leades) than some of my other 45's like my Ruger P97 which doesn't have much leade taper at all. A chamber casting showed this pretty clearly. Thus a cartridge that would headspace on the case mouth on one gun might headspace on the bullet in another.

[captaint]

35r - While I don't think my brass is unusual in length at .890 - I have about a .015 space above my fired, plunked brass to the top of the hood. About the same thing with the 70's military ball. I don't know if chambers have changed over the years (in length). Certainly, I'm headspacing on the boolit. I'm fine with that, because it works. Just found it curious that we always say - the 45ACP headspaces on the case mouth. In my case, it does not. As a side note, I just opened up the Speer #9 to find their stated case length for the 45ACP is .898. My brass, of various makes is considerably shorter than that.
Sorry for the absence, I have been away applying my flyfishing skills?? on Penns Creek for a couple of days.
Those wild browns will school us quick !!! Had a great time, though. Mike

[35remington]

0.015" is nothing and quite tolerable. Your extractor holds the rim about 0.043 to 0.045" from the breechface, on average, given the tolerances of most pistols. If 0.015" is what you find and no gap exists between breechface and hood your headspace measurement is a little shorter than middle of the road. Your cases would have to be nearly 0.860" in length to headspace on the extractor if extractor gap is average, and I bet you don't have any cases anywhere near that short.

The cartridge does indeed headspace on the case mouth with some jacketed bullet rounds, especially those factory loaded, and those with ball or ball like ogives. And depending upon how long your throat is as I mentioned in an earlier post.