300BO 10.5 blow up today

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dieselherb
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300BO 10.5 blow up today

Post by dieselherb »

I was shooting some hand loads today. 110gr then decided to try some 230gr cast. First round, blew the pistol up. I have shot these rounds many many times maybe 3-400 at least. Using CFE Black 11gr. Cartilage 2.17 oal brass with .335 bullet with .305.
Any idea what happened? Maybe by mistake used H110 but still 11gr, weighed the other in the mag.
ReadyAimDuck
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Re: 300BO 10.5 blow up today

Post by ReadyAimDuck »

Any pictures?
dieselherb
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Re: 300BO 10.5 blow up today

Post by dieselherb »

Of what?
ReadyAimDuck
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Re: 300BO 10.5 blow up today

Post by ReadyAimDuck »

The blown up pistol?
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bangbangping
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Re: 300BO 10.5 blow up today

Post by bangbangping »

dieselherb wrote: Fri Dec 31, 2021 7:26 pm .335 bullet with .305
Can you explain what these numbers mean? If we're talking about a 300 blackout, a .335 diameter bullet could be a problem.
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dellet
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Re: 300BO 10.5 blow up today

Post by dellet »

dieselherb wrote: Fri Dec 31, 2021 7:26 pm I was shooting some hand loads today. 110gr then decided to try some 230gr cast. First round, blew the pistol up. I have shot these rounds many many times maybe 3-400 at least. Using CFE Black 11gr. Cartilage 2.17 oal brass with .335 bullet with .305.
Any idea what happened? Maybe by mistake used H110 but still 11gr, weighed the other in the mag.
What are those numbers?

If 335 is neck diameter of a loaded round, it could be a problem, it’s possible to have zero or even a interference clearance at the neck in the chamber at that diameter. Pinching the bullet in the neck. You might get away with it using CFE, not likely with H110. 11 grains is close to max load.

If you have been using a lot of CFE, it a very dirty powder, and with a really dirty chamber and tight chamber, again pressure spike is possible. Chronograph numbers for the shot would be helpful would be helpful if you happen to be using one.
300 Blackout, not just for sub-sonics.
dieselherb
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Re: 300BO 10.5 blow up today

Post by dieselherb »

That was brass width at neck, bullets are .3005 for laegest most .299. Have a pic of the casing in the barrel, but not sure how to load it here
ReadyAimDuck
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Re: 300BO 10.5 blow up today

Post by ReadyAimDuck »

Don't worry about the pictures, if you can't find a way to load them. I was just kind of curious to see to what extent the damage was. I'm glad you are safe and presumably unharmed.
dieselherb
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Re: 300BO 10.5 blow up today

Post by dieselherb »

Thanks, bruised finger thats all. It blew the side out of the casing near the primer. Haven't been able to get it out of the barrel.
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dellet
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Re: 300BO 10.5 blow up today

Post by dellet »

dieselherb wrote: Sat Jan 01, 2022 10:07 pm Thanks, bruised finger thats all. It blew the side out of the casing near the primer. Haven't been able to get it out of the barrel.
That sounds more like a mechanical malfunction with the rifle, firing out of battery, or a case head separation.

The case head separation is the more likely. Brass with multiple firings and excessive resizing often fail there, it’s where most of the stretching happens and eventually the brass gets so thin, it blows or pulls apart.

But your measurements are still questionable. Your bullet should have a max diameter of the bearing surface of .308” for jacketed and more likely .309” for cast. You should probably check the zero sitting on your measuring tool. If it’s off by .003” then your bullet is actually .308” and your neck diameter is .338” and that will also cause the case to come apart with excessive pressure. An undersized bullet would have very little pressure and very low velocity, most likely very noticeable to the shooter. So this may actually be the root of the problem.
300 Blackout, not just for sub-sonics.
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