I have not seen the rifle yet but here is the story. It is a model 70 stainless, in 300 Weatherby. He said...when he fired the rifle the barrel bulged about halfway down (big bulge). I know the barrel is gone, what would you expect on the action, as I said I have not seen the rifle yet as it is on its way, opinions on what would you see on a accident like this.
Is it worth checking headspace, knowing the pressures involved?

I expect no damage whatever to the action. Why check headspace; you need a new barrel anyway.
If there was any gas leakage you will see it on the bolt face. But there will likely be none.
Barrel bulges are not caused by excessive chamber pressure; they are caused by obstructions in the barrel causing a local pressure spike.
Probably the PO left a patch in it.

Wouldn't you want to check for lug setback?

quote:

Originally posted by montea6b:
Wouldn't you want to check for lug setback?

That was one of the questions that came to mind. Thats why I wondered about head space.

Bulges are really weird things. I have spoken to the people in the know while doing warranty with the manufacturers and their opinion is always much the same as Toms. It's simply the pressure wave following the bullet that actually catches up with the bullet when it encounters the obstruction and creates a micro, momentary pressure spike just behind the bullet. As Tom says it is supposedly localized right in the area of the bulge and very seldom if ever causes any other problems. In all my years and the hundreds of bulged barrels I have dealt with I can not remember a single one that had any problems outside of the bulge. I have also seen badly bulged barrels that have shot just fine with the bulge and the owners have chosen to just leave the barrel as it is. One guy I know with a particularly unsightly one has been shooting it like that for years with no problems. It groups under an inch. So, go figure.

Right, in all the cases I have seen with budged barrels, there is no indication of excessive chamber pressure. it is a local pressure spike in the barrel; not in the chamber. That would be evidenced by typical high chamber pressure indicators; which are usually not there. It is caused by crap in the barrel; not high chamber pressure. Even oil in the barrel will do it. We had them in our tank cannons (M256, 120mm). usually from dirt being scooped up in or just back from the muzzle. Or leaving a muzzle boresight in. The barrel would bulge or break off, but the breech was un damaged in any way. In fact, the crews often did not notice it.
Which is why I would not be concerned about the action. Of course you can check if if you want; to; easiest way is to shoot it and see if it is hard to open. Hell, it might shoot fine. Seen that too as Speer has.
As he said, it is the pressure wave stopping abruptly because the bullet has slowed down; something has to give and it caused a bulge.
High chamber pressure does not cause barrel bulges.

Rifle came in today, barrel looks like a snake that swallowed a golf ball half way down. I ask him did you clean it before you went shooting..no, did you check the bore prior to shooting..no, will you next time...yes. lesson learned the hard way. He is a good kid just had a memory lapse.

Oil, grease, patches, brushes, wasp nests, cleaning rods, boresights, mud, bullets, and many other things will cause that.

I have a related question but, won't hijack this thread.
Sako barrel
Thanks,
George

I was talking with Jim Clark (Clark's guns) and then my mechanical engineer boss about this thing, sometime long ago, about a lever gun with a bulged AND split (cracked) barrel that they had on display -- ( i THINK it was a 44, for whatever that's worth) - the rifle has had a squib load, and the bullet was still in the barrel when the next bullet was fired.

Jim was interested to show how the failure occurred closer to the stuck bullet, but not on or at the stuck bullet - rather it was behind the obstruction, between it and the chamber.

Okay, that's neat - what does it mean?

Ike (my then boss -- wow, it's been awhile) tried to explain it to me in some really cool math, that i wasn't actually able to follow - BUT, he grabbed a simple pump - a balloon pump, btw, about as simple as it gets ... and pumped it a few times "these are the pressure from a normal shot" ... okay, i get that .. then he pull it back all the way, pushed in about 10%, put his thumb over the end, and couldn't mush much more --- he asked me if the pressure was at his thumb or what?

well, since i understand boyle's law, i told him OF COURSE the pressure is at his them -- and then he went into some interesting fluid dynamics stuff on impulse and then into failure modes (Ike is a great guy, and will explain anything to anyone, in great detail) -- but, again, in a simple model, he grabbed a sheet of paper, laid it flat on the desk, and then with his finger tips, pushed the ends towards each other ---

and, of course, the paper folded up just about in the middle ---

okay - makes sense...

then he repeated the same, but put one hand about 3" on to the paper, and the other at the edge -- and guess what? it folded in about the middle of the distance between his fingers, not in the center of the paper..

then he went on to explain that, in this case, the pressure built up, created an impulse between the obstruction and the "piston" which is why the bulge didn't occur at the midpoint from the caliber of the unfired cartridge and the obstruction...

then he explained that the taper of the barrel comes into play , which made sense, until he wanted to do the math ----


i think i was 27 at the time, and this left a heck of an impression on me

j