Gunsmithing Need help : fireformed case /fresh cut chamber

[Vitali1342]

Well, long story short .
In procces of fireforming 300 NM to 300 NM 40 Imp. Almost full load of Retambo with 215 Hyb. Peterson brass. Case came out with nice crisp fireformed shoulder but about 1/3 of an inch to the base I noticed bulge only on one side of the case . Fired to fireform 300 NM Lapua brass and end up with the same deformed case in a little lesser degree ( I assume Lapua is slightly tougher brass ) .
My question is : a) is it normal for the case to get such deformation after first firing ?
b) my freshly cut chamber not concentric ?

Please refer to the last pic on the right

 

[Vitali1342]

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[Supersubes]

How long have you had your peterson brass? They recently added .002 to the base diameter to the new batch. Shouldnt change anything, except make the appearance of the bulge less pronounced. It is VERY short in headspace though, was your gun headspaced off a gauge, or brass? My guess is it was slumped in the chamber when it was fired, and the case expanded upward. Seems like an awful soft load as well, depending on barrel length, you should end up north of 3100. Regarding the bulge, don’t bump the shoulder when you size unless you must, and shoot them again.

 

[Vitali1342]

Thank you , that was my initial thought about underloaded charge . I'm gonna go up in charge , size neck only and fire the case again. Thank you !

 

[bjay]

Those bulge case was it harder to extract?

 

[Vitali1342]

No bjay not at all

 

[bjay]

No bjay not at all

One of my first 300nm imp reamer was .006" per inch body taper..i know ackley has .010 per inch but mine was so straight i was getting little bulgde close to the base and little resistance while extracting.maybe pressure is coming backto boltface after firing? ..i just hope its not your chamber
Have you tried dropping the load.or every case coming out with bulge

 

[Vitali1342]

bjay , i only fired those two cases , I'm at very beginning .

 

[bjay]

bjay , i only fired those two cases , I'm at very beginning .

Is there anyway you can check chamber is precisely cut or maybe barrel vise?

 

[DAVETOOLEY]

Just about every case fired in any rifle has a bulge. You have clearance between the brass and the chamber. When pressure comes up the case expands. Most of the time it's on one side. Probably the thin side but I've never sectioned any brass to find out because it doesn't matter. Just shoot it.