700 chamber has fractured

[gamestalker]

I have an old 700 chambered in 7 mag. that has had about 5K-6K of slow burning powdered loads through it that has developed a fracture. About 200 rounds ago a small swollen spot showed up on the brass. I was obviously concerned being that the defect on the brass is pushed out, and not inverted. So I continued shooting the rifle and kept a very close eye on the defect, which is located just above the web where incipient head separation commonly occures when brass has reached it's expiration. I didn't change or get any larger, and then suddenly I had a complete separation yesterday. After the separation I inspected the chamber as good as I could and couldn't see any indications suggesting things had gone completely south. So I chambered and shot another 3 rounds thorugh it, and all had incipient separation that were all located radially in line with the defect.

So toady I inspected the chamber and can't find any reason for the defect or the separations. I had a small carbon build up where the defect is presenting so I used some solvent and a patch to remove it which went just fine. I also used a small stiff wire to check for a fracture, and bingo I located it and confirmed my chamber did in fact go bye bye!

My question is why? I have shot these loads for years and years out of many actions and have never had anything happen. Do chambers just say enough is enough and then fracture like this, or is 4k-5k of full powered loads a reasonable cause for this type of failure? All the years of reloading and shooting I've never experienced a catrostrophic failure. And the groups this particular rifle shoots even after the problem presented, is as tight as anything I've ever shot. I put 3 rounds at 200 yds. touching each other, after the fracture opened up enough to cause head separation.

 

[blarby]

Sadly, metal fatigue does occur.

Sometimes it take a long time, but nothing subjected to the kinds of pressures used in rifle lasts for ever.

Could have started at birth in the metal as stress from boring the chamber into a very tiny linear weak spot in the metal.

Sound the taps, send it to a smith and have it reworked, or wall hang it ?

Very sorry for your loss... I know you loved that 7 !

 

[FROGO207]

It probably was that the metal blank had a defect in it when manufactured and you were the lucky one to get that particular barrel. Any piece of metal that is poured/rolled/forged can have a defect in the structure of it when it is manufactured and the problem was not seen when the barrel was machined. Unless each barrel was X-rayed when made I doubt that it could have been detected anyway, but who wants to pay for the extra cost for this test when buying a barrel. It always hurts when a good tool breaks for no good reason that's for sure. Are you going to get a new barrel? I would think that it usually would be worth it unless the rifle was a beater or really inexpensive to begin with. I would treat it the same as worn rifling or eroded throat issues in a well used barrel. FWIW have you checked on shortening the barrel and re boring the chamber? Still I would always wonder if it was going to happen again if I re-bored it however.

 

[Old Shooter]

The barrel probably did have a small defect from the date of manufacture but it was so small as to not be noticable, time and use took it's toll.

You can't really sell it as a shooter so the only option I can see is treat it as a shot-out barrel and have the action re-barreled.

OR you could disable the current barrel and sell/use the gun for parts.

I'd be really concerned about a possible catastrophic failure down the road with that barrel. If the defect has gotten worse in the last 200 rounds that indicates something is moving and that isn't good.

Sorry for the loss.

 

[JLDickmon]

time to put into honored retirement...

hey, any excuse to buy a new gun, right?

 

[4v50 Gary]

Rebarreling is the solution.

 

[MtnCreek]

Do you think this could be related to loading cases till head separation or do you think it's unrelated?

Sorry to hear about your rifle. Hopefully the next barrel will be as good as the original. Good luck on getting her put back together.

 

[rcmodel]

I doubt if it's cracked.

I would rather think it is flame cutting in the chamber wall from the high pressure gas that leaked out. Maybe more often then you think it did.

I have never seen or heard of a barrels chamber cracking like that in 50+ years of fiddling with them.

Had it actually cracked, I think bad things would have happened when the leaking gas made it to the barrel threads.

rc

 

[gamestalker]

RC, this is the first I've ever heard of, or in particular this case, seen happen. As far as shooting my brass till it separates, I don't do that. I load and shoot my brass only after carefully inspecting it after resizing and tumbling. I toss anything that has internal or external signs of impending separation. In the history of loading for this firearm, I have only had a couple of cases that slipped by that resulted in a visible separation in which gases had escaped through.

Such a shame, as this barrel was a tack driver. But when a guy loads the kind of stuff I do, there is always an inherent risk of being the guy that discovers the barrel that had the defect most would never have encountered in a life time of casual shooting. I would imagine the average shooter only puts a few hundred rounds down range from a high power magnum in it's life time. And although I don't shoot thousands per year, I do shoot a bit more than those who shoot once or twice a year in preparation for hunting season. I feel like I got my money worth though.

 

[MtnCreek]

I feel like I got my money worth though.

5k plus out of a 7RM, I'd say you sure did! Off memory, I thought you were talking about shooting cases till head seperation not too long ago?

 

[Slamfire]

Sometimes the metal used in the barrel is not appropriate for the application.

Get a new barrel before your rifle looks like this M1a:

Most Horrendous M1A/M14 kB! Ever

http://thegunzone.com/m1akb/762r.html

 

[fguffey]

Gamestalker, again, I took a Model 70 Winchester chambered to 300 Win mag to their warranty shop, I explaind to them the chamber was the ugliest chamber I had ever seen, Winchester told me I should shoot it more, at that point they thought I was impossible, then they suggested the Winchester warranty shop should have the opportunity to polish, hone and ream the chamber and I could not understand how polishing, honing and or reaming would make the chamber smaller, the warranty shop attempted to make the chamber smaller by honing, polishing and reaming, then they sent the rifle back to Winchester, and we had words, I wanted a chamber that would fit my dies or I wanted Winchester dies that would fit their chamber, and that is when they thought I was impossible.

Cases fired in the Winchester could not be sized in my RCBS full length sizer dies, nor could they be sized by my small base sizer die or my BAR dies, etc., etc., or my case forming die. The only way I could size the large cases was to size the base of the case in front of the belt was with a collet in one of my lathes, and that is mindless, it is possible overworking brass is geographic, sizing the base of a case to fit my reloading dies is working the brass needlessly. Winchester never asked me how I determined the chamber was too long, too large in diameter and gouged, they returned the rifle in a new box without an explanation, that was 4 years ago, I do not need the rifle to have something to shoot, if I had confidence in it I would, I have new take off barrels for the Model 70 for Magnums but I do not have a bolt for the 30/06 case head.

the Remington model 700

http://www.remington.com/product-families/firearms/centerfire-families/bolt-action-model-700.aspx

is the ring around the ring around the ring design, gas escaping and cutting is not impossible, case head separation is not impossible, many bolt faces have been cut with hot high-pressure metal cutting gas around the primer and because of punched primers. 5,000 to 6,000 thousands rounds is enough to ware out a barrel, the barrel is hammered every time a round is fired, it is believed the barrel chamber is elastic, it is believed it expands and then recovers, that is not necessarily true, recovery may not always equal compression, but, who saves a fired case from the first box of ammo fired for comparison.

Normally throat erosion/cutting is the first sign of having been fired many times, a bore scope would help. I started to remove 6 bullet in a 357 magnum, no barrel bulge, removing the barrel seemed to be the best place to start, problem, the forcing cone had expanded .012 thousandths, I replaced the barrel.

Suddenly, all at once and with out warning is not the norm, it would be interesting to check muzzle and throat erosion, if your cases cause the problem it seems the chamber cutting ahead of the belt would be random, not in one position unless you were indexing the cases before firing.

Removing the barrel could be interesting.

F. Guffey

 

[TNBilly]

Unless it's scoped I doubt you'll ever know if there were previous pieces of metal lost in the barrel, I suspect it's probable. Good news is, if it were mine, 7mm Mag barrels are the biggest take-offs there is on GB. You can likely pick up a brand new one for less than $50.

 

[Skyshot]

Sorry about the loss, but time for a new air gauged match barrel in 1:8 twist so you can shoot them 180 gr. berger VLD's in that 7mag.

 

[x_wrench]

while i would retire that barrel, i certainly would not retire the gun. a new barrel will get you back to shooting your favorite gun. find a good smith, and either opt of a new "custom" precision barrel, or buy a new take off, from gun broker or the dreaded "eBay". lots of people buy a new gun, to have a custom made from it. and the brand new barrel that came with the gun goes up for sale, usually by the gunsmith doing the work. that is what i did with my remington 700, 300 win mag. unfortunately for me, i did not pick a good smith. he was supposed to be one of the best around. but he did not do a good job as far as i am concerned. after 3 trips, it is now safe to shoot. but i am not really happy about the way it came out. he has lost a client, for sure.

 

[gamestalker]

Even though it's an old ADL and was only about $289 NIB, I think I'll rebarrel it. That particular barrel has been a tack driver from day one, even after 4K-5K of reloads.

Thanks ya all!
GS

 

[Art Eatman]

Decision made...

 

[Walkalong]

And life will be good again.