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  #1  
Old 01-12-2008, 08:16 AM
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Question Barrel bulge causes?


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This past Monday when my slide locked rearward never to return (without force) a gunsmith the next day showed be a bulged barrel he said was caused by a normal round following a squib round. I recall no audible difference between the reports of the last round, the suspect round, and the previous round. Assuming there was nothing wrong with the charge, what else could cause this? the loads in question were .40 cal 180gr. LSWCs charged with 5.7gr. N350 at 1.125 in. lightly crimped. I do most of my rounds on a Lee 4 hole turret press so charge variation is not very likely.
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  #2  
Old 01-12-2008, 09:51 AM
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Got to agree with your gunsmith...it's a barrel obstruction, mostly likely caused by a weak round that logdged the bullet, followed by a full power round. Most common is a short-charge of powder, but it could have been caused by powder contamination (blob of lube on a bullet base that melted into the charge....glob of wetness in the case...etc.

Last edited by ribbonstone; 01-12-2008 at 09:54 AM.
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  #3  
Old 01-12-2008, 11:27 AM
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Thats about the only thing that can cause a bulged barrel. Something lodged in when a full power load hits it. It's seen in 22 rifles and handguns the most. Lots of those ringed barrels used to come thru the pawn shop I worked in. Not so many big bores.
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  #4  
Old 01-12-2008, 11:33 AM
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I would not assume that there was anything wrong with the charge. Yes, it is possible that you had such a large blob of lube, and you had the cartridges stored for a while in high heat condition, that resulted in the lube contaminating enough powder to cause a squib and sticking in the barrel.
But, since a primer alone will usually move a bullet out of the case (and in a revolver sometimes stick the bullet in the forcing cone), and you are using lead bullets, you are possible talking about 1 grain or less of powder being in the case. This would be sufficient to move the bullet down the barrel enough to allow another cartridge to feed.
You said that you are using a Lee turret, so it is possible that there was something that held up the powder measure. I am not familiar with N350, so I don't know if it is spherical, flake or tubular powder. Generally spherical flow easily through a powder measure.
However, as discussed in other threads, the older style of Lee powder measure with the spring return can sometimes hold up, resulting in low or no powder going into a case. What type of powder measure are you using?
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Old 01-12-2008, 11:42 AM
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I'd agree, except for the fact that the supposed squib round obviously had enough recoil to cycle the slide and chamber the next round. I have to wonder if a squib would do that. I'd have thought not.

But insofar as I can't think of any other reason for the bulge, perhaps it was gas pressure and not recoil that cycled the slide. Beats me.

(The one alternative cause would have been a separated core/jacket that left only the jacket in the bore. But these were LSWCs, as per the post.)
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  #6  
Old 01-12-2008, 01:27 PM
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My first experience witnessing a bulged barrel came about at my local range when the shooter to the left of me let out an "ouch" and dropped his revolver on the shooting bench. The revolver exhibited a bulge and split about 2/3rds of the way up the barrel. Seems the shooter had a friend who sold him the revolver (S&W Victory model) along with two boxes of WWII military ball ammo. The shooter thought everything was going fine until this happened. A look at the barrel showed a jacketed bullet lodged there in plain sight not quite clearing the muzzle. It was thought that one of the rounds was a squib and the following round slammed into it. Fortunately, no one was injured, a few feathers were ruffled, and a fine vintage revolver was in need of some gunsmithing.
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Old 01-12-2008, 03:03 PM
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Quote:
Originally Posted by Rocky Raab View Post
I'd agree, except for the fact that the supposed squib round obviously had enough recoil to cycle the slide and chamber the next round. I have to wonder if a squib would do that. I'd have thought not.

But insofar as I can't think of any other reason for the bulge, perhaps it was gas pressure and not recoil that cycled the slide. Beats me.

(The one alternative cause would have been a separated core/jacket that left only the jacket in the bore. But these were LSWCs, as per the post.)
I've done it. Squib load that only drives the bullet part way down the barrel usually is too weak to cycle the slide, but it can have just the right amount of pressure to piston back the slide and load another round. IF you feel like living very dangerously, can duplicate the effect (but it's not a recommended experiment).
------
I've personally seen three guns bulge their barrels. One was a SIG 220 at a combat match (was running the timer/wearing the RO hat). Rapid fire, the slide cycled, but no "ding" or obvious bullet impact...even the shooter kind of knew something was wrong, but was shooting so fast there was no way he could stop the second shot. Bullet in barrel/slide cycled from gas pressure, second round ran into the first.

I stopped myself in time when testing a .401WSL (rifle)...that's a blow back rifle and not a locked breech, but was the same effect. Got a nice loud "bang" but noticed the gas, smoke, and sparks of burning powder ejecting. However, if I was really bearing down hard in a rapid fire string, doubt i'd have caught myself in time.

What the two above taught me is that it takes longer to recognize that recoil was "off" than it does to stop a fast trigger finger.

Revolvers can do it as well, with the added fun of the noise and gas escape at the cylinder gap to hide the problem (goes bang, gas doesn't leaks out the back end, so you might conclude noting was wrong).
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Old 01-12-2008, 04:29 PM
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Dang. I'm amazed that it could, and only typed that as a theory. So I AM amazed! Thanks!
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Old 01-12-2008, 04:30 PM
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Originally Posted by ribbonstone View Post
. . . Squib load that only drives the bullet part way down the barrel usually is too weak to cycle the slide, but it can have just the right amount of pressure to piston back the slide and load another round.
Yup. Exactly so. If the squib had been just a hair stronger and actually got the bullet just clear of the muzze, the slide would not have cycled back far enough to pick up the next round. The usual recoil inertia and muzzle rocket effect that cycle a slide for a normal round would have been absent. But with the bullet stuck in the barrel, you now have a pressurized cylinder and piston, and that pressure pushes back on the case until it clears the chamber to bleed the pressure off. By then the cycling inertia has been acquired by the slide.

There was a CO2 powered dry fire practice gadget around for awhile that replaced the barrel with a same-size piston that cycled the slide. Same piston principle. No bullet being launched at all.
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  #10  
Old 01-12-2008, 05:01 PM
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Long as we're mentioning barrel obstructions, will ad a few not related to your case.

Have seen over driven HBWC's put two holes in the target...one from the solid front, and a ragged one from the expanded and blow skirt. Have also seen part of a skirt ( a "ring") left in the forcing cone. Have seen a few revolvers used exclusivly with HBWC ammo that had unexplained rings. Good bet that the skirt can be blown and stay in the bore (helps if the bore is leaded), waiting for round #2 to slam into it. Shooter would have NO CLUE...gun would go "bang", hole (from the solid front 1/2) would show up on the target.

When 1/2 jacketed were popular, esp. in home swaged bullets. Had a tendency to leave the 1/2 jacket in the bore if used at lower velocity..Speer at least use to carry the warning on their .357" 160gr. SP and .410" 220gr 1/2 jacket bullets (but i haven't bought or used any of those in a long while).

BTW: shot guns are not immune. Have seen several old doubles and one O/U that had little "dings". With a weak crimp (reloader either not loading right or getting one more load out of worn out shells), can have barrel one fire...recoil break crimp of barrel #2's shell...shot spill forward..then when #2 fires, it "dings" into loose shot on it's trip down the bore. Seemed to be more common with duck guns, but that's probably becasue they used larger sized shot.
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  #11  
Old 01-13-2008, 10:00 AM
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Better attention to detail?

Thanks everyone. I respect and accept the opinions rendered. Case lube was not an issue as I don't need case lube with my setup. The cause has to be some sort of charge contamination but I have yet to figure what. The load in question was one of numerous rounds made on my 4 hole turret press with a Lee perfect powder measure on the charging die. On my test rounds I fire slowly for observing effects and weigh every charge individually. In this case I wouldn't quite call it rapid fire but fast fire, maybe 2-3 rounds per second so comparison between one round and another was not perfect. I'm left with extremely bad luck or not exacting enough on my powder handling somehow.
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  #12  
Old 01-21-2008, 07:46 PM
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I've seen it happen at the shooting range, there was spilled unburned powder all over the shooters hand, he realized what was happening even though he'd never fired this gun before and didn't do the loading. I also had a bulged barrel on my Mauser 1914, but it was like that when I got it.
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