sfoskey's experience set off warnings in regard to my current situation. I wish to remain on the safe end of all rifle ejecta. Bear with me as I'm attempting to tell the whole story as I know it. Feel free to criticize, admonish, and ridicule. Photos of the rings will be at the bottom.
A few weeks ago I changed out a 12BVSS from .223 to .260 by installing a Shilen prefit barrel. A go-gauge was used to set the headspace approximately 0.002" longer than the gauge. The bolt closes freely while chambering the tool. Bolt face to datum in the chamber (or wherever the tool seats) is 1.563" as close as I can tell using a piece of tape on the face of the gauge. (I know I know, but it's what I've got) At least the bolt displays no resistance without tape, and some resistance with. Calipers measure the tape as 0.002"-0.003".
The ejector was removed from the bolt while setting headspace and has not been re-installed.
I bought some Corbon ammunition to shoot while waiting for reloading supplies. The brass and bullets they used were Lapua. The Corbon ammunition averaged just over 1.561" base to shoulder using a Sinclair Comparator Body and Bump Gauge Insert. I thought it a bit strange when some of the ammo chambered with a bit of resistance upon closing the bolt, but went ahead and shot it anyway. Opening the bolt showed some resistance with some cases as well. It was not noted if the cartridges that closed with resistance were the same as those that opened with resistance.
There were no flattened or cratered primers, no image or any other mark where the ejector used to be, but all cases show a ring around the head in the form of a bump, about 0.08" forward of the groove. As close as I can figure, the bumps are up to 0.002" in height.
The once fired cases measure an average of 1.564", so the base to shoulder length increased approximately 0.003".
A few days ago I loaded 20 rounds for an OCW test. I initially thought I would just neck size, but after running all the once fired cases through the rifle's chamber decided against it as too many chambered with some difficulty. I used a Redding Body Die to set the shoulder back an average of .002"-.003". I immediately noticed an increase in press handle resistance when the die started across the raised ring. This was my first attempt with a new press, and new type of die, so my technique was and is a little ragged. Some cases came out a little less, some a little more in shoulder bump. Anything longer than about 1.5630" was bumped back again as they chambered with resistance. The cases were then neck sized using a Lee Collet die.
I headed to the range after closely following Dan Newberry's instructions in loading for the OCW test. The bolt showed resistance on opening on only a couple cases, but every CCI 200 primer was flattened, and flattened equally from the lowest charge through the highest. There was no cratering on any round. The ring around the head is still visible on the twice fired cases (sizing them left the high spot shiny), but it is much more difficult to feel with a fingernail. The bump seems to be non-existent or nearly so. The bumps on the once fired cases have a much more noticeable feel.
Some questions. Why would some of the Corbon rounds chamber with resistance when, according to the Go-Gauge, all factory ammunition should chamber safely?
The SAAMI spec sheet says the .260 Remington loaded round should be 1.5598" from base to shoulder. Is that a maximum?
Why are the primers flattened upon firing the reloads, but show no other pressure signs? There were no flat primers on the originals.
Should these cases be scrapped?
Should the rifle's headspace be increased?
Once fired case is on top, twice fired below:
A few weeks ago I changed out a 12BVSS from .223 to .260 by installing a Shilen prefit barrel. A go-gauge was used to set the headspace approximately 0.002" longer than the gauge. The bolt closes freely while chambering the tool. Bolt face to datum in the chamber (or wherever the tool seats) is 1.563" as close as I can tell using a piece of tape on the face of the gauge. (I know I know, but it's what I've got) At least the bolt displays no resistance without tape, and some resistance with. Calipers measure the tape as 0.002"-0.003".
The ejector was removed from the bolt while setting headspace and has not been re-installed.
I bought some Corbon ammunition to shoot while waiting for reloading supplies. The brass and bullets they used were Lapua. The Corbon ammunition averaged just over 1.561" base to shoulder using a Sinclair Comparator Body and Bump Gauge Insert. I thought it a bit strange when some of the ammo chambered with a bit of resistance upon closing the bolt, but went ahead and shot it anyway. Opening the bolt showed some resistance with some cases as well. It was not noted if the cartridges that closed with resistance were the same as those that opened with resistance.
There were no flattened or cratered primers, no image or any other mark where the ejector used to be, but all cases show a ring around the head in the form of a bump, about 0.08" forward of the groove. As close as I can figure, the bumps are up to 0.002" in height.
The once fired cases measure an average of 1.564", so the base to shoulder length increased approximately 0.003".
A few days ago I loaded 20 rounds for an OCW test. I initially thought I would just neck size, but after running all the once fired cases through the rifle's chamber decided against it as too many chambered with some difficulty. I used a Redding Body Die to set the shoulder back an average of .002"-.003". I immediately noticed an increase in press handle resistance when the die started across the raised ring. This was my first attempt with a new press, and new type of die, so my technique was and is a little ragged. Some cases came out a little less, some a little more in shoulder bump. Anything longer than about 1.5630" was bumped back again as they chambered with resistance. The cases were then neck sized using a Lee Collet die.
I headed to the range after closely following Dan Newberry's instructions in loading for the OCW test. The bolt showed resistance on opening on only a couple cases, but every CCI 200 primer was flattened, and flattened equally from the lowest charge through the highest. There was no cratering on any round. The ring around the head is still visible on the twice fired cases (sizing them left the high spot shiny), but it is much more difficult to feel with a fingernail. The bump seems to be non-existent or nearly so. The bumps on the once fired cases have a much more noticeable feel.
Some questions. Why would some of the Corbon rounds chamber with resistance when, according to the Go-Gauge, all factory ammunition should chamber safely?
The SAAMI spec sheet says the .260 Remington loaded round should be 1.5598" from base to shoulder. Is that a maximum?
Why are the primers flattened upon firing the reloads, but show no other pressure signs? There were no flat primers on the originals.
Should these cases be scrapped?
Should the rifle's headspace be increased?
Once fired case is on top, twice fired below: