Bulged barrels?

[lundy]

A question to those that may know.

What pressure is being developed to bulge these barrels?

PPosey shot 108 gr. H4198 and over 400 gr of bullet and sabots. Is it linear or does it have an x factor? Double normal load pressure or much more?

At what point does a double load barrel bulge have the potential to become an exploded barrel instead?

What if he had been shooting a load of 64 gr of H4198 as his base load?

I think you can see where I'm going with this. If you are shooting a load that is in the higher (what ever that is)pressure ranges and make a mistake and double load are you risking a exploded barrel versus shooting a lower pressure load and almost assured of only a bulged barrel with a double load?

What would be the ranges for a load that is defined as low, normal of high pressures? Where does a 40K load fall in those pressures ranges? I think it is a middle of the road load.

Sorry for all of these questions, just trying to increase my knowledge and understanding.

Thanks,
Kim

[pposey]

Only 54 grains of mine shot,,,, I had 2 complete loads, powder,,, bullet, powder ,,,bullet,, so it was 54 grains powder pushing 454 grains of weight

[ET]

Lundy I’m no expert and can only reply from my limited knowledge & experience.

There are many variables for generation of pressure. Even sabot/bullet fit can alter the pressure as seen from resulting velocities. Temperature can also play a role here. Powder lots can slightly change that again affects generated/resulting pressure.

The barrel for the 10ML-II is rated for slightly over 90,000psi if properly quenched and tempered. Now what happens if a barrel doesn’t quite reach that rating and comes out say at 85,000psi? Still safe to shoot recommended loads that are in the 40,000psi range.
I am not aware of an x-factor you could employ even if it exists because of so many variables that are encountered.

For me if you stay in a given boundary of pressure say under 50% of rated barrel Yield strength (10ML-II) then you have a decent margin for safety when unintentional higher pressures are generated.

If memory serves me correct the Fail strength of the 10ML-II barrel is around 120,000psi. The metal will tear itself apart.



Ed

[lundy]

Oct 7, 2010 6:54:01 GMT -5 pposey said:

Only 54 grains of mine shot,,,, I had 2 complete loads, powder,,, bullet, powder ,,,bullet,, so it was 54 grains powder pushing 454 grains of weight

Did the second powder load ignite? I would think so given the results

Did the barrel bulge with only the initial 54 gr load igniting and the 454 gr of weight restriction?

[lwh723]

Oct 7, 2010 7:38:37 GMT -5 lundy said:

Oct 7, 2010 6:54:01 GMT -5 pposey said:

Only 54 grains of mine shot,,,, I had 2 complete loads, powder,,, bullet, powder ,,,bullet,, so it was 54 grains powder pushing 454 grains of weight

Did the second powder load ignite? I would think so given the results

Did the barrel bulge with only the initial 54 gr load igniting and the 454 gr of weight restriction?

I suspect only 54grs ignited.

Makes me wonder if the barrel ruptures we've seen weren't from double loading and the second load also igniting.

This somewhat makes sense to me since as I recall most of the barrel ruptures were with books load with more easy to ignite powder like A5744.

I was told a story by an old black powder shooter how he saw a guy seat a load by "throwing" a brass ramrod on the load for the final seating. The black powder ignited from the pressure, and shot the ramrod up through the range roof. Now I don't know if 5744 would ignite just from pressure, but I'm sure there's some heat involved too with a double loading.

Just a thought...

Glad you're okay pposey.

[pposey]

I dont think the 2nd load fired, If so I would have lost a hand,,,,,, or a head

[chuck41]

Hard to tell what the second load did. Under the extreme pressure I would suspect that it must have ignited. Two loads that normally produce 40,000 pressure would likely generate 100,000 or so stacked like that which would explain a bulged, but not failed barrel. I doubt if just the extra weight of a projectile of near 454gr instead of the planned 200 would be enough to do that. The 458 WinMag with 58gr of H4198 and a 500gr bullet only produces 51000 CUP. Excessive to be sure, but still not enough to bulge a heavy barrel.

Keep in mind that a diesel works that way. Lots of pressure raises the temperature enough to light the fire. 40,000 lbs of pressure could generate enough heat to light most any fire even without a bit of gasses leaking around the first bullet/sabot to add to the mix.

[Richard]

I would almost feel that IF the second charge did ignite? Then it would almost be like two seperate ignitions. NOT one big blast? Each producing its own combustion in a seperate chamber. In my opinion, it is just the sudden force of the first charge, trying to move all the weight of the bullets, powder and sabots on top of it that causes the pressure spike. If the second charge ignited, it would simply fire the top bullet out
Richard

[rangeball]

I posted it in the other thread, if someone with quickload or powley could estimate the pressure from the load, that would be great

[lundy]

Maybe my questions are stupid I don't know.

Based upon what Chuck posted. Wouldn't the second charge have had to ignite to create enough pressure to bulge the barrel. That is where I have been trying to get to I guess since my first questions.

Wouldn't the gap around the first sabot allow for the first powder charge burn to ignite the second?

The 458 WinMag with 58gr of H4198 and a 500gr bullet only produces 51000 CUP. Excessive to be sure, but still not enough to bulge a heavy barrel. [/color]

Thanks

[tasaman]

I doubt the second load ignited either. Flame would have had to get past the sabot seal and that is doubtful. I think when the first load ignites, it moves the first bullet forward effectively compressing the second charge while waiting for the top bullet/sabot to move creating a hydraulic effect. Since the first bullet is moving forward and the top bullet isn't it squishes the second powder charge outward instead of forward. Could be wrong though.

I have read from several sources that if you load two saboted bullets it still won't bulge a barrel but it will quite often happen if it's two full loads one on top of the other.

Ed

[lwh723]

I don't think it necesarrily needs to ignite. Rifle & shotgun barrels are regularly bulged or worse from a stuck wad or other barrel obstruction.

1+1 doesn't equal 2 in the case of barrel obstructions.

[minst7877]

Also remember that the bottom bullet is acting as a wedge on the powder charge that is in front of it. Thus the resulting side pressure is dramatically increased on the bore of the gun.

DC

[pposey]

I don't think the 2nd charge blew,,, there would have to have been a huge fireball if it did,,,I couldn't burn more than 55 grains 4198 without one

[pposey]

Oh and my primer removed easy and wasn't in any abnormal condition,,,, not alot of extra blow back either,