7 PRC Resizing

[JM151]

In your soot picture of the one that doesn't fit, is your case mouth not completely bright indicating contact? Hard to tell. I'm guessing you didn't see a big ol carbon ring...

The neck was solid black. I didn’t see any carbon ring but did notice these two weird lines that would be in the chamber area. The lines are pretty far from the throat so wouldn’t think it’s your typical carbon ring.

 

[A382DWDZQ]

I don’t think it’s an issue with your shoulder or headspace because your empty, sized cases fit from both boxes. I think that something must be happening during the seating. Are you using a bushing die to set the neck tension? Are you able to reduce the neck tension a bit. If you have a bullet puller, pull the projectile from the case that doesn’t chamber, and see if that empty case will chamber. If it does, just reseat the bullet, but seat it back ridiculously deep. Then check that. If that doesn’t chamber, then that would make me think that the case has deformed somehow during the seating. Maybe the die is hitting the neck and pushing it down? Or the neck tension is too tight and the case is getting bulged or something during the seating.

 

[wapitibob]

Ok so did some more testing. I wanted to test if seating the bullet was causing my issue. I seated the bullet back into the case .005" at a time and it still wouldn't fit.

The next test was smoking my brass. I took a lighter and covered it in silt. I attempted to chamber and it appears to have contact right past the shoulder. See in picture 1.

View attachment 936627

Picture 2 is from my borescope and you can see black silt left in chamber.

View attachment 936628

Picture 3 is from a piece of brass that does fit and you can see right past the shoulder you have black silt from contact in chamber from the leftover. That seems really tight to me. Do I potentially have a crazy tight chamber? My 1x fired case at a datum measurement of 1.896 and my 2nd fired case at a datum measurement of the same 1.896. Reamer prints show minimum would be 1.900. If it's hitting there then this wouldn't be a shoulder bump issue correct?

View attachment 936633

That black ring of soot is exactly where my body die sizes my brass (body and shoulder bump) with my current barrel. Kind of an odd spot from my past barrels but that's where this brass grows. Not sure it makes a difference but I use separate body and neck bushing dies instead of a full length sizer.

 

[JM151]

I don’t think it’s an issue with your shoulder or headspace because your empty, sized cases fit from both boxes. I think that something must be happening during the seating. Are you using a bushing die to set the neck tension? Are you able to reduce the neck tension a bit. If you have a bullet puller, pull the projectile from the case that doesn’t chamber, and see if that empty case will chamber. If it does, just reseat the bullet, but seat it back ridiculously deep. Then check that. If that doesn’t chamber, then that would make me think that the case has deformed somehow during the seating. Maybe the die is hitting the neck and pushing it down? Or the neck tension is too tight and the case is getting bulged or something during the seating.

Yeah I’m using Redding Comp bushing die. I believe my bushing is .312. I also use an expander mandral from 21st century and it’s .2832. When I measure empty cases my neck is .313. When I load a bullet it’s .314. Which would be what .001 neck tension.

I’ve tried one like that. I took one loaded round that wasn’t fitting and seated it lower and lower by .005 at a time and it wouldn’t fit or never fit.

I was wondering about the seating die bulging out the brass somewhere as well, according to the silt it’s right past the shoulder.

 

[A382DWDZQ]

Yeah I’m using Redding Comp bushing die. I believe my bushing is .312. I also use an expander mandral from 21st century and it’s .2832. When I measure empty cases my neck is .313. When I load a bullet it’s .314. Which would be what .001 neck tension.

I’ve tried one like that. I took one loaded round that wasn’t fitting and seated it lower and lower by .005 at a time and it wouldn’t fit or never fit.

I was wondering about the seating die bulging out the brass somewhere as well, according to the silt it’s right past the shoulder.

That would be neck tension of .002”, OD of the loaded neck minus the bushing diameter. Do you have a larger bushing? Also, are you chamfering, deburring, and dry lubing the neck? Have the cases been wet tumble cleaned? Have you checked the seating die without a bullet, just an empty case to make sure it’s not hitting the mount?

 

[fraz01]

Your picture looks to be the transition from chamber to the throat. it looks like there is a little carbon staining on the edges that's pretty common. I may have missed it but if you pull the bullet on a case that won't chamber, will the case without the bullet? May be a concentricity issue or a very tight chamber dimensions.