300 PRC Sizing

[dguns18]

Trying to resize some 300 prc brass (Factory Hornady 225 ELDM, Bergara custom shop) and noticed on the once fired brass, there is a substantial bulge at the bottom of the case (see picture). Using a Hornady sizing die, there is alot of resistance when trying to size over that bulge (so much resistance that I broke a RCBS Rock Chucker Supreme linkage arm) Looks like the bulge was too big to overcome by the sizing die. I am using Unique sizing lube.

Is the bulge on the brass an indicator of somtehing wrong with the chamber or something else?

Once Fired Brass:


Piece of brass that broke press:

Factory Ammo:

 

[A382DWDZQ]

Can you measure the factory and the bulged case at the same location and see what the difference is? Looks like it might be a larger chamber, but might also be a tight die.

 

[dguns18]

Can you measure the factory and the bulged case at the same location and see what the difference is? Looks like it might be a larger chamber, but might also be a tight die.

Measured .33" up from the base.

once fired brass is .544"
Factory ammo is .520"

Die body is .532"

 

[wapitibob]

Chamber is hosed up, should be .533 at the .200 line. No way on planet earth that brass grows .010 on a spec chamber no matter how hot the load is.

 

[dguns18]

Chamber is hosed up, should be .533 at the .200 line. No way on planet earth that brass grows .010 on a spec chamber no matter how hot the load is.

should also mention I read somewhere on a forum ( don't know which one) to test the chamber by wrapping painters tape around the brass and see if it chambers. I wrapped 2 layers of painters tape around the area that bulges on a factory round, and it chambered. Which seemed weird, so I tested it with factory ammo with my tikka 308 and it wasn't even close the chambering with 1 layer of tape.

 

[dguns18]

Chamber is hosed up, should be .533 at the .200 line. No way on planet earth that brass grows .010 on a spec chamber no matter how hot the load is.

I measured about .200" up, and it is .520". The bulge is higher on the case, about .330" up.

 

[TaperPin]

It looks like a lot because the case doesn’t have a belt, but I’ve had a number of cases expand like that. Having said that .544” is .012” over spec as others have said. Normal full length dies don’t usually take all of the bulge out like that - it wouldn’t happen to be a small base die? (Edit: I see you answered that question with die measurement)

The chamber dimensions are minimums and can be .002” larger. The cartridge dimensions are maximums and can be .008” smaller. At least that what the fine print says.

 

[A382DWDZQ]

I measured about .200" up, and it is .520". The bulge is higher on the case, about .330" up.

That’s probably just the webbing keeping it together near the base. Hopefully you can get that taken care of by the manufacturer.