Monday, August 10, 2009

ka-POP!

While shooting at Eagle Creek yesterday, Shootin' Buddy brought out his AR-7 which he had just picked up from his gunsmith. The rifle was an older, Charter Arms-manufactured version, which he had bought new and just had refurbished after shooting the wheels off it for many years.

After assembling the rifle he immediately began having failure-to-fire issues with the bulk .22 he was using. I can't remember off-hand, but I believe it was Federal. He switched to some of the Remington blue-label subsonic target ammunition that he had along for his suppressed MkII and one of those managed to fire.

Boy howdy, did it fire.

There was an unusually loud report and the second round didn't chamber fully. Shootin' Buddy pulled the magazine, and it had smoke floating up out of it. That's not normal.

"Case failure?"

Sure enough, the separated case head was laying on the carpet scrap at his shooting station, while the remainder of the brass was still snug in the chamber, as seen in the accompanying cell phone photo.

Monday morning quarterbacking, I'm going to guess that the sequence of "light strike, light strike, light strike, et cetera" followed by "case head separation" points to an excessive headspace situation.

In layman's terms, this would mean that the cartridge had too much room to move forward and back in the chamber when the bolt was closed. If this was indeed the case, the light strikes were caused by the round shifting forward when struck by the firing pin. The one that actually went off would have had too much room for the brass to stretch in the chamber, and it stretched past the point of failure.

Of course everybody was wearing eye protection, and nothing bad happened to the gun, but be careful when saying "Oh, it's just a .22." While its powder charge may be small, the modern high velocity .22LR chamberings operate at higher chamber pressures than .38 Special or .45ACP. SAAMI maximum allowable pressure specification for the .22 Long Rifle is 2,500 PSI more than .380, and 3,000 psi more than .32 H&R Magnum.

Remember: The eye you save may be your own.

29 comments:

Anonymous said...

"Behold, I have become death, destroyer of guns."

Shootin' Buddy

Carteach0 said...

I saw something like that on an UZI, on which the barrel hadn't been fully seated into the action. Got away lucky, with just a small blow out into an extractor groove.

ajdshootist said...

I had five case failures a couple of months ago with American Eagle 22 ammo in a Win Mod 63 but put 22 Blazer in it and it runs fine trouble is all 22s seem to have favorite ammo i have Three 22s and they all like or hate different Brands.

aczarnowski said...

"Refurbishment" doesn't include a head space check?

Tam said...

That's going to be between him and his 'smith.

tomcatshanger said...

I had two out of battery case failures with my Carbon 15 .22 lr before it went back to Bushy.

It might be a teeny tiny little round, but not well contained explosive expansion is something to be respected. Destroyed a magazine the first time and the extractor the second. Weee.

MCSA said...

I had a Ruger Mk1 KB...

It was interesting, especially the feeling of getting hit in the nether regions by a fast moving extractor...

Tam said...

The kinda embarrassing part about the whole thing is that while Shootin' Buddy was having issues with his AR-7, I had just pulled out the Marlin Papoose he got me for Christmas last year.

While he's over there dealing with light strikes, I'm wearing out my "Zombie Bob" target in a fountain of spent brass. They called the range cold and, as I started loading up my Papoose mags for another go, I said "Man, this is fun! I love this Papoose!"... ... ...long pause... ... He says "Yeah, it's running like a sewing machine," and goes back to diddling with the defunct AR-7.

D'oh! :S

Anonymous said...

Mess up that headspace and timing with a M2 or M3P in .50 cal by using the wrong gages - now THAT is a KB. Wear your goggles - Old Gaijiin

Kristopher said...

I used to own a Charter Arms AR-7.

Utter crap. I sold it to some kid, ASAP.

Replaced it with a Garcia Bronco ... a neat skeletonized .22.

( Photo is not mine ... mine is in much better condition )

Tam said...

Wow, a Bronco? Your shoulder is much machoer than mine, especially if you shoot slugs! :o

Kristopher said...

Ermmm ... it's a .22 LR ... although they did make a .410.

Or ( more likely ) am I being obtuse and missing a joke/snark?

Tam said...

Ah. I was thinking of the .410 with the bent coat hanger for a shoulder stock...

You wouldn't think that a bitty little shotgun could hurt that much.

Kristopher said...

Sounds painful. I take is some sadist inveigled you into shooting one?

Tam said...

If you spell sadist "g-u-n-s-m-i-t-h".

"Here, you wanna shoot this?"

"Why, does it hurt?"

"It doesn't weigh anything and has a wire stock with five feet of drop. It hurts like a sumbitch. You chicken?"

Anonymous said...

Had that happen once with a nearly new Ruger Mark II. Firing out of battery was the conclusion after much investigation. It's digested a few thousand rounds since then without any trouble. Since it was my then five year old son firing it, I guess it was a combination of extreme limp wristing and a little dirt, caused the bolt to stop just short of battery, but close enough for the mechanism to fire it. A .22 bore brush pushed the broken case out. We quit shooting for the day, and went as far as sending the case remains and lot number to Remington, who came up with the "out of battery" reply. It only happened that once. Keep it nice and clean. -- Lyle

Les Jones said...

"Garcia Bronco"

That's a new one on me. Hinteresting.

Mostly, though, I'm just glad to find someone whose feet rival mine for ugliness. If he'd get ingrown toenails on both big toes he might just have me beat.

Standard Mischief said...

Ah, I've had the misfortune to have an AR-7. Mine came with this wonderful crinkle-coat paint job, inside and out.

Anyway, I'd go with Carteach's theory about the barrel. Is there any chance it was not put on correctly? I'd try to reassemble first (after getting that brass out) and then try hand-inserting some spent 22LR and try to make some primer dents.

If it's still wonky, next I would check:

1. Make sure no one went too aggressive with smoothing around the chamber throat.

2. Remove the bolt handle, the bolt, and check to see if the springs and that little plastic thingy that holds the springs are all original and still there.

3. Check the bolt face for alterations and push on the firing pin, making it protrude. Check to make sure no one tried to "sharpen" or monkey with the firing pin, and make sure it's sliding back and forth OK.

Since it's just a simple blow-back action, there's not much to go wrong with the headspace unless someone was trying to get subsonics to cycle by monkeying with the bolt springs or someone went overboard on the smoothing.

Favor: Could you ask him if his stock is cracking right below where the receiver attaches to the stock? Every single AR-7 I've seen has this issue.

SteveC said...

I had the very same thing happen with a friend's AR-7 that I was shooting. Unfortunately, I shoot left handed and did not have ear protection. (Hay, it was 30 years ago. Nobody used ear protection.) Took the joy out of a day of plinking.

Dr. StrangeGun said...

"It doesn't weigh anything and has a wire stock with five feet of drop. It hurts like a sumbitch. You chicken?"

Spacegun's stock is right up there. 4" by 1/2" square middling-hard rubber... and it's sneaky. It's doesn't "hurt", it's just a little uncomfortable. Then you get home and find you've bruised/rubbed the outline of the little pad into your shoulder. If I'd shot 5-6 more magazines worth out of it I'd probably have drawn blood.

I still remember the experience with the .405Win Contender.

I also still remember the "experience" I gave myself shooting a hot 3" slug out of Thumper, that lightweight Topper 12ga. Good bruise that evening... fingers still hurt too where the forend ripped itself out of my grip. Slug splattered on the backstop hard enough to shatter an overhead light... I don't recall if you were there that day to witness.

Fairlane64 said...

I had an old Remington pump jam a .22 shell sideways on me about 30 years ago, unfortunately I was looking right at the receiver when it jammed and went off. Put a piece of brass in my forehead and knocked me out for about 15 minutes. When I came to I had a big gouge on my head, covered in blood, and a headache for about 3 days. No doubt, even a .22 can kick your butt or kill you if you're not careful. I was just plain lucky!

Speaking of being lucky, I was wondering if anybody who knows a bit about old S&W top break revolvers can look at my page here: http://fairlane64.blogspot.com/ and leave a comment regarding ammo safety and shooting the old gal.

Thanks!

Turk Turon said...

I have never owned an AR-7; got persuaded out of it and got a Marlin Papoose instead. Great little gun.

Didn't James Bond shoot somebody with an AR-7 in "From Russia With Love"?

wv: sadizate
A group of people named "Sadie"?

Mad Saint Jack said...

Had an Armalite AR-7 with lots of feeding problems years ago.

Gun fired out of battery. My hand, that was wrapped around the magazine, was covered in gunpowder and the bottom of the mag was bowed out. Not a fun time.

A few months back saw a case failure in a ruger MK III, blew the loaded indicator out of the gun. Then it started to double.

E. Lawrence said...

A)Since .22LR headspaces on the rim, not the case mouth or shoulder, where would the extra room have come from other than grinding down the boltface?

B)Who in their right mind would do such a thing?

As MSJ above suggests, its an OOB event.


Eagle 1

Tam said...

Barrel not seated completely is a candidate. I'm by no means certain, though.

Beaumont Guy said...

Re: Garcia Bronco

I seem to recall, as a kid, seeing a .22/410 combo Bronco at JC Penney's. Yes, in those days, the JCP in Morristown TN sold many more guns than Wallyworld does now.

I have been searching for info on these combo guns without success. Has anyone else encountered on of these?

cj said...

I've got a funky AR-7 variant that actually works...if you hold the magazine JUUUST right, otherwise it's essentially a single-shot.

Anyway, I'm betting on the barrel not being fully seated. One of the major design flaws is the ability to screw the barrel on with the bolt forward, resulting in some extra space in there. Pull the bolt back slightly with one hand while attaching and screwing on the barrel removes that space.

Anonymous said...

James Bond shot down a helicopter with an AR-7. Ah, movie magic :-(

RSR

Tam said...

"Anyway, I'm betting on the barrel not being fully seated. One of the major design flaws is the ability to screw the barrel on with the bolt forward, resulting in some extra space in there. Pull the bolt back slightly with one hand while attaching and screwing on the barrel removes that space."

That's one of the nice things about the Papoose: Not only is it screamingly obvious when you're trying to seat the barrel with the bolt forward, but it comes with a spanner wrench for making sure that sucker's on there snugly.