New to me issue with brass

[xsn10s]

I'd see this with a 7 RUM with a double spike on the Oehler 85 Ballistics pressure testing. As said before the idea was that the case neck doesn't seal properly and it dents the cases inward until it seals at the shoulder. That seems like a low charge of H4350 judging from Hodgdon's 175 gr loads. But that's only a guess because I don't have a Hornady manual.

 

[Grubby]

I appreciate all the comments. The data I am using is from the Hornady guide for that particular bullet. Those loads are coming out at 2925 ft per second already so they are a pretty fast bullet. It is happening at the chamber, not resizing. I am going to go up a bit on the charge and check again. Are these cases safe to use again?

Thanks again,

Grub

 

[asd9055]

I'd see this with a 7 RUM with a double spike on the Oehler 85 Ballistics pressure testing. As said before the idea was that the case neck doesn't seal properly and it dents the cases inward until it seals at the shoulder. That seems like a low charge of H4350 judging from Hodgdon's 175 gr loads. But that's only a guess because I don't have a Hornady manual.

I am not questioning that you have seen it, I am trying to wrap my head around the physics. the moment the bullet leaves the case, if there is not a total seal, the pressure inside and outside the case is the same.

 

[jimbires]

Clean that resizing die out. Make sure relief hole in side of die is not plugged with lube.
Gun scrubber spray works good.

good catch on mentioning the die vent hole .

 

[jimbires]

I appreciate all the comments. The data I am using is from the Hornady guide for that particular bullet. Those loads are coming out at 2925 ft per second already so they are a pretty fast bullet. It is happening at the chamber, not resizing. I am going to go up a bit on the charge and check again. Are these cases safe to use again?

Thanks again,

Grub

YES , the cases are safe to reuse .

 

[RockyMtnUT]

Interesting, the one with a black line, hard to see a dimple. So, let me understand this, we use COW, no bullet to seal around, to fireform, and we can get dimples like this from underpressure. I still would like somoene to explain the physics

The bullet leaves the barrel too fast and creates a vacuum, causing the brass to collapse. My Creedmoors do it all the time.

 

[Grubby]

Here is the load data from the Hornady App:

 

[asd9055]

The bullet leaves the barrel too fast and creates a vacuum, causing the brass to collapse. My Creedmoors do it all the time.

Thats interesting. I'll have to think about this one. It is also interesting that his load is at the minimum.

 

[xsn10s]

I am not questioning that you have seen it, I am trying to wrap my head around the physics. the moment the bullet leaves the case, if there is not a total seal, the pressure inside and outside the case is the same.

There's no way to actually tell unless you get a camera in there internally. That's just not going to happen as far as I know. How it was explained to me the guys in the ballistics lab figured the bullet got started moving and then jammed into the rifling. There was a lag in the pressure because of the weak seal and then the pressure built up again to send the bullet through the bore. I don't think I kept the print out but I'll check this weekend.

 

[RockyMtnUT]

Put in a factory round and see if it does it. If it does,it's in your chamber. If not it's your reloading and or process

 

[Grubby]

These were cleaned prior to the photo. I use a home brew for my case lube which consists of lanolin and rubbing alcohol. I checked a few other cases by heavily sprayI guess them and and running them back through the dies and no further denting was visible…however, they were already resized. I am going to do some testing this weekend with more powder and see what happens.

I really appreciate all the quick feedback. You guys are the best!!

Regards,

JG

 

[xsn10s]

Here is the load data from the Hornady App:

View attachment 379232

So @ 64 gr of H4350 you're below the starting loads. I'd try bumping up your load if you aren't seeing pressures.

 

[asd9055]

There's no way to actually tell unless you get a camera in there internally. That's just not going to happen as far as I know. How it was explained to me the guys in the ballistics lab figured the bullet got started moving and then jammed into the rifling. There was a lag in the pressure because of the weak seal and then the pressure built up again to send the bullet through the bore. I don't think I kept the print out but I'll check this weekend.

Thank you. Don't worry about it looking for it. It will just cause more questions in my mind. I accept that it happens.

 

[Grubby]

Actually, the starting load for the bullet is 58 grains, I just couldn't fit it all in the screenshot so this charge is in the middle range of the recommendations. I am going to jump up to 64.4 and go up in half grain increments up to the max load.