Valornor
03-18-2017, 12:14 PM
About eight months ago I went on a tour of Southern Ballistic Research (SBR) and discovered a little round called 338 Spectre. I've since gotten a 16" barrel and finally finished the AR build. For those who don't know, this cartridge is based on the 10mm Mag necked down to .338 cal. Similar to 300 AAC Blackout, it was design specifically for launching 300gr SMK's at subsonic velocities. Starline makes the 10mm Mag brass and I use CH4D dies to neck the brass down to .338 cal.
I am still very new to this caliber. I just began working up loads last weekend in three different bullets. I've had some excitement with that (stuck a 285gr Barnes TSX bullet halfway down the bore), despite an obvious squib load, I have not seen obvious signs of over pressure pressure. I.E flattened primers, loose primers, excessive case length growth or ejector marks on the head of the case. QuickLOAD lists the max pressure of 37500 PSI.
As I was cleaning some of the brass I had used to work up these loads I had three cases out of about 30 that had pretty substantial longitudinal cracks on the case body. I've seen small cracks on other cases, usually at the neck or just in front of the head but never anything like this. I can think of maybe one cause, but would like to get input.
My thought is either the chamber is too large and the brass may be too small. Resulting in over expansion of the case and cracks on the body of the case. If this is the case I likely have a chamber that is over sized, and I need to contact SBR. If the brass is to small then fire forming the brass and just doing neck sizing from here on out should prevent the case from expanding more. Unfortunately I do not know what loads produced the cracks in the body, but I will be looking for it in future loads.
190947
These were the first time these shells were loaded after forming.
I am still very new to this caliber. I just began working up loads last weekend in three different bullets. I've had some excitement with that (stuck a 285gr Barnes TSX bullet halfway down the bore), despite an obvious squib load, I have not seen obvious signs of over pressure pressure. I.E flattened primers, loose primers, excessive case length growth or ejector marks on the head of the case. QuickLOAD lists the max pressure of 37500 PSI.
As I was cleaning some of the brass I had used to work up these loads I had three cases out of about 30 that had pretty substantial longitudinal cracks on the case body. I've seen small cracks on other cases, usually at the neck or just in front of the head but never anything like this. I can think of maybe one cause, but would like to get input.
My thought is either the chamber is too large and the brass may be too small. Resulting in over expansion of the case and cracks on the body of the case. If this is the case I likely have a chamber that is over sized, and I need to contact SBR. If the brass is to small then fire forming the brass and just doing neck sizing from here on out should prevent the case from expanding more. Unfortunately I do not know what loads produced the cracks in the body, but I will be looking for it in future loads.
190947
These were the first time these shells were loaded after forming.