Trying to understand the danger of

[Bearbait in NM]

firing a short case in a long chamber, ala 40 S&W in 10mm, 45acp in 460 Rowland or one of the 9mm variants.

I have seen written that it is unsafe to fire 40's in a 10. Patrick Sweeny discusses the results of a case head blow-out, without detail in a thread I found. Johnny Rowland advocates shooting 45acps in his Rowland chamber (which I have). I am trying to understand the mechanics, and where the risk may be. I fully understand headspace, and that the shorter case will have excessive headspace. But, if you do not have sporadic ignition, the case will be moved deeper in the case, actually giving the case head more support, as it is deeper in the chamber. If the case is thrust back after primer ignition, it cannot move back further than the longer case would, so I do not see how there could be excessive lack of case head support.

The only thing I can think is that you run the risk of the primer blowing back out to the rear, and perhaps out of the case? Or perhaps if you are running lead bullets, you can foul the throat/chamber stop area with the shorter case, and blow out the longer case full throttle load due to interference with the case releasing the bullet (akin to 45Colt/454 Casull)?

I have fired acp's in my Rowland, just not a lot, and I would like to more fully understand the risks, if any.

Thanks,

Craig

[log man]

While I don't have first hand experience with this I agree, not dangerous. At the instant of ignition the case head would be pressed against the breech face, same case exposure as the 10mm would have, the extractor would keep it from going deep in the chamber, just as it would do with a case that was undersize. I've heard of people accidently firing 45gap and thought they where 45acp until later with no ill affect. The only area that would bring concern to me would be from shooting lead that would obturate and scrape on the shoulder, perhaps causing a high pressure problem.

LOG

[Hawkmoon]

I don't think there is a serious risk, but that does NOT mean I think it's a great idea. The 1911 design is that the cartridge headspaces on the mouth of the case, and then end of the chamber. The case rim is under the extractor hook, both to help control feeding and because that's what lets the extractor ... extract.

A short case still feeds the same way ... rim in the extractor. The short case won't go fully into the chamber and headspace with the mouth at the end of the chamber, it will stay there with the rim in the extractor and the head basically held against the breech face. In essence, it is headspacing on the extractor. If the extractor holds the case tight enough to allow the firing pin to set off the primer, the gun will go bang. The bullet will have to jump that gap at the end of the chamber before it engages the rifling, so accuracy may suffer. But it will fire.

If the short cartridge escapes the extractor and somehow manages to headspace on the end of the chamber, unless the difference in case length is rather minimal I wouldn't expect it to fire at all, because the firing pin may not reach the primer.

There was a report here awhile back from a guy who ran a full magazine full of .45 GAP through his 1911 before realizing the drone at the gun shop had sold him the wrong stuff. No harm done.

I don't think it's inherently dangerous, but I also don't recommend doing it.

[Iron bottom]

I've been told it is dangerous because when the round is fired, the thin brass near the case mouth is expanded and held to the chamber wall by the pressure. The brass gets thicker near the case head. When the point is reached where the pressure will no longer expand the thicker brass to the chamber wall, it will tend to stretch reward, thin out, and seperate.

I did shoot a box of GAP in a .45ACP barrel with no ill effects. but probably got lucky.

[shovelwrench]

When the point is reached where the pressure will no longer expand the thicker brass to the chamber wall, it will tend to stretch reward, thin out, and seperate.

This is assuming that the cartridge is'nt pushed to the breachface prior to brass expansion. And that the pressure is great enough to make the brass grip the chamber wall. It would be interesting to see if .45 gap brass grows after a few reloads fired from a .45 acp.

Every person I know who was brought up around guns started with the few basic rules of safe firearm handling. One of those rules was, be sure you have the correct ammo for the gun you are going to be using. That has always been my practice, except in revolvers, but then .38 is correct for a .357, sorta.

I agree wit Log Man that lead buildup on the shoulder could be a serious issue.

I guess the big question is, is there a known instance of a 1911 ka-booming because of exsessive headspace.

[log man]

Hey, shovelwrench, I'm going out on a limb that doesn't worry me at all and say that excessive head space will not case a ka-boom , excessive case exposure will and is often confused with head space. Firing off the extractor and limited accuracy would be the limit of negative results from it. So with that in mind a smooth bore created by reaming the entire barrel to chamber diameter dimensions would not be accurate nor would it ka-boom as long as the barrel ramp remained in spec.with the breech face. Might be fun!

LOG

[shovelwrench]

On a side note.

I was working up a target load with a freind for his .357 (he was currently running .38 brass), we found that the load he had been using was the most accurate from his gun, but, was still yeilding unacceptable groups. We reworked the same load in .357 brass, matched the velocity of the .38 load (.5gr more), and it knocked 1" off his group at 25yds.

All done from a ransom with a chrony.

[El Gato]

the issue here is headspace... the auto cases headspace on the case mouth the 38/357 headspaces on the rim... apples and oranges...
Some...autos have a tight enough extractor that they will hold the case against the breachface with enough force to fire the cartridge ... the case may "grow" and be useless for reloading thereafter.. the casehead may seperate if it is slightly off the breachface and cause a catastrophic failure... like blowing the grips off your nice 1911...
I have witnessed people, on numerous occasions firing 9mm through a 40 sw glock.. the gun fires because the case is held by a springloaded extractor but the case fails.. because there is a mm of space around the case, there is typically no blowback of gasses into the action...
I know someone who has put about 1,000 rds of 40sw through his 10mm glock using the 10mm glock barrel... the gun is actually very accurate ... my guess is that the bullet jumps to the forcing cone and that evens out the pressure curve on the 40sw or something...
A better bet is to buy an additional barrel... fit it ... and then shoot the 40 or 45acp rounds... the rowland barrel I have no experience with but isn't the caselength the same as the acp?... could be wrong about that by the way...
That's my 2.3 cents worth anyway... :)

[log man]

El Gato, firing a 9mm in a 40S&W chamber as a comparison of shooting a 40 S&W in a 10 mm chamber or a 45GAP in a 45ACP chamber is like comparing apples and man hole covers, come on that just doesn't relate nor do the expected results.

LOG

[Iron bottom]

The problem arises mainly when a short case gets ahead of the extractor. What we have in the 1911 is a firing pin that will protrude into the chamber a good 1/4 inch or more. I did measure this after my little escapade. It may or may not have the momentum to light off a primer after traveling this far. I don't really know. I do think a case head seperation is a possibility with all the room behind the case head.

[El Gato]

El Gato, firing a 9mm in a 40S&W chamber as a comparison of shooting a 40 S&W in a 10 mm chamber or a 45GAP in a 45ACP chamber is like comparing apples and man hole covers, come on that just doesn't relate nor do the expected results.

LOG
or apples to ...or..or...oh I give up..you're right ...man hole covers...
the point being the extractor on a glock will hold the case... that is all ... nothing else...carry on ...

O by the way... case head separations in Browning typer pistols.. hi-power included ... are the kinda fun that pegs the old fun meter a little too drastically for me... I'll pass...seen it too many times... have a client who has permanent nerve damage in his hand from a "gun show reload" fired in his belgium browning during one of my classes....seen too many damaged pistols too.. 4 digit serial number commercial 1911... made tears come to the eyes....

[Hawkmoon]

I've been told it is dangerous because when the round is fired, the thin brass near the case mouth is expanded and held to the chamber wall by the pressure. The brass gets thicker near the case head. When the point is reached where the pressure will no longer expand the thicker brass to the chamber wall, it will tend to stretch reward, thin out, and seperate.
You need to be careful about who you listen to when they "tell you" things.

Think about it -- just exactly where and how is the thicker brass section at the head going to go anywhere? It is already essentially in contact with the breech face, held there by the extractor. It can't move more than a few thousandths of an inch. As to the thin brass at the case mouth being "held" in the chamber while the head stretches itself off the case? No way, Jose. Brass certainly doesn't have the tensile strength of steel, but I think it has more than whatever "stiction" is momentarily developed by the temporary expansion of the thin brass at the case mouth.

[Hawkmoon]

So with that in mind a smooth bore created by reaming the entire barrel to chamber diameter dimensions would not be accurate nor would it ka-boom as long as the barrel ramp remained in spec.with the breech face. Might be fun!
I have a partially unfinished barrel that would make a perfect candidate for this little experiment. If you want to follow though, PM me your address and I'll ship it off to you.

[frsorrow]

i would love to see the results of this test

[log man]

I have a partially unfinished barrel that would make a perfect candidate for this little experiment. If you want to follow though, PM me your address and I'll ship it off to you.

Well, it's going to have to be fitted to a frame and slide and is probably right up Tuner and Bill Caldwells alley. As I think about it they may have already done this. Appreciate the offer, and already have a half dozen take off barrels to play with.

LOG

[berkbw]

The issue here is NOT headspace. Also, the possibility of case stretch in a standard pressure .45ACP is mathematical, at best. The largest problem that I fear is that the longer travel in an oversized tube might allow for a poorly aligned entry into the lands with higher pressure buildup.

$0.02

[Jim Watson]

Actually, Ironbottom is not far off.
A short round that feeds up under the extractor will shoot normally. If it gets ahead of the extractor and the unlimited firing pin protrusion sets it off, there can be fireworks.

It wasn't in a 1911, but Maj. George C. Nonte demonstrated it with the Astra 400 which was sold surplus here as shooting all 9mm rounds. A sales gimmick because the proper 9mm Largo was not available in the Colonies. He shot the Astra with 9mm P under the extractor and they did fine. He chambered one ahead of the extractor and it blew out the primer and a good section of the primer pocket.

Not in MY guns, thank you.

[Bearbait in NM]

Thank you for the thoughtful replies. I kind of figured that a case that got ahead of the extractor would blow a primer. I think one of my specific issues is the pressures involved. The ACP runs at about half of the pressure as a 40 or 9, and I have not seen or measured any brass or primer issues in the ones that I have fired. Still, 18k down the magwell would not be fun. And the Rowland chamber is indeed cut deeper than an ACP chamber.

And, this is not something that I have to do, just wanting to understand the mechanics. Rowland says it's OK, and I saw him doing it on his show, when he had one. But, I am not one to see one person do something, and assume it is safe. I am funny that way, with that much pressure in my hand. ACPs from my Rowland are extremely soft shooting, and very accurate. It would also give me some options when hunting with the Rowland, if I want to drop in an acp to pot a bunny or grouse. It could also be helpful in the winter, when I am forced to shoot in the snow. The brass bearly clears the ejection port, and would make finding and collecting the brass easier.

Craig