Looking for some solutions here. I just finished loading up some 150gr SMK's using varget powder and new winchester brass. At my starting load of 43.5gr I already have signs of pressure, flatten primers and a buldged case. I full length sized the cases and trimmed to 2.005". I measured everything twice and can't find anything that could give this result. OAL is 2.800", giving 0.050" from the lands in this particular rifle. This is the first time I've used SMK's and new winchester brass. I've had no problems with 150gr TSX and federal cases. Any thoughts?
308 Pressure new brass
- Thread starter gillamboy
- Start date
I use 46gr. Varget with 154/155 bullets in Winchester brass (Fed. GM primers), so your load is certainly moderate. What kind of rifle are you using? By bulged, I assume that you are referring to the expansion ring in front of the head? That is more a factor of case and chamber diameter than excessive pressure. Flattened primers can be a sign of high pressure, but there can be other causes. Can you measure casehead expansion? That is, expansion of the solid portion of the case just in front of the extraction groove.
stubblejumper said:
Agree completely, this was my work up again, 43.5gr is a pretty light load. I'll get the casehead expansion and post it. The buldge is in front of the expansion ring on the case body, one side only. I'll try to get a pic posted if I can take one clear enough.
Casehead expansion is nil, started at 0.464" and was 0.464" after firing. The expansion ring diameter is 0.472" up from 0.462", which is the same as my fired federal cases (0.472"), except the winchester case is all on one side (buldged). Picture coming ASAP. What about the backed out primers? Thanks for the info so far.
Here's a link to the picture. The white background wasn't the best but you can see the buldge on the right side only.
http://i211.photobucket.com/albums/bb229/gillamboy/HPIM11962.jpg
http://i211.photobucket.com/albums/bb229/gillamboy/HPIM11962.jpg
I would say
that particular chamber is on the large side. Is it a factory cut chamber? My Rem 700 22-250 prior to becoming a 6BR showed the same sort of bulge on the brass.
Now that it is a 6BR cut with a chamber closer to the dimensions of the brass I have never seen any sort of bulging around the web area.
My dad has a Midland .243 Win that has a large chamber in the web area. I am not sure if my Lee press would be able to handle resizing the brass that comes out of it. At times it feels as if the casting on the press is ready to let go.
How is the extraction? By the sounds of it there should not be any difficulty........?
that particular chamber is on the large side. Is it a factory cut chamber? My Rem 700 22-250 prior to becoming a 6BR showed the same sort of bulge on the brass.
Now that it is a 6BR cut with a chamber closer to the dimensions of the brass I have never seen any sort of bulging around the web area.
My dad has a Midland .243 Win that has a large chamber in the web area. I am not sure if my Lee press would be able to handle resizing the brass that comes out of it. At times it feels as if the casting on the press is ready to let go.
How is the extraction? By the sounds of it there should not be any difficulty........?
shotgunjoe
CGN Regular
- Location
- winnipeg mb
It is posible that you got a batch of cases that were minimum spec.Hard to blame the chamber as the tikka is usually well cut.Did you measure the cases before firing?
lejarretnoir
CGN Ultra frequent flyer
- Location
- 162km from Connaught
IMO, a bad chamber cut or bad brass. Seeing that I cannot hold the case in my hand to be sure. You may want to send that rifle back if it's the chamber. Neck sizing only probably won't work with that chamber.
Yes I measured some before firing, case heads were 0.464" and the same after firing. I see spec is 0.470" though. But at the expansion ring it grew 0.010" which seems a lot to me, especially only on one side???? Also, I never had a problem with any factory ammo, federal, winchester, etc. I also had no problems with American Eagal FMJ's which I used as fire formed brass to do my last sets of reloads (neck sizing only). Again thanks for the info and ideas, keep it coming.
http://www.6mmbr.citymaker.com/f/Sierra308Win.pdf
http://www.6mmbr.citymaker.com/f/Sierra308Win.pdf
What dies are you using? I would look at the dies before jumping to the conclusion of an oversize chamber. See if you can borrow a different set of dies from someone. Maybe the die is not concentric with the ram/shell holder when you screw it down.
- Location
- Vancouver Island BC
Backed out primers are usually a sign of a light load , I have heard this from more than one source.
If Federal brass doesn't bulge, it's not the rifle.
The case looks just fine to me. Any bulges will go away in the sizer die. Check the lengths, trim as required, chamfer and deburr the case mouths and load 'em.
Can you post a picture of the primer?
The case looks just fine to me. Any bulges will go away in the sizer die. Check the lengths, trim as required, chamfer and deburr the case mouths and load 'em.
Can you post a picture of the primer?
303carbine said:
I've read the same thing, look at this link:
http://images.google.ca/imgres?imgu...q=flattened+primers&gbv=2&svnum=10&hl=en&sa=X
sunray said:
Speaking of primers, my terminology was wrong. My primers did not 'flatten' they backed out, just past the back of the case. The more I read this looks like low pressure, not high pressure. I still have 15 more rounds in my work up, maybe I'll shoot the next set up, with more powder and see if it improves. More thinking first...
