308 pressure signs

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Pierre-Luc

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here's my problem . i'm reloading 308 using S&b brass , cci 200 primers , 178g a-max ... started a load at 40g of varget and i'm getting sticky bolt (3 out of 6 round), flat primers and some shiny marks on the base of my brass.
my load is not compressed and i loaded at 2.800 OAL. brass is trimmed to 2.005.
what could it be? i've mesured my fired brass just over the extractor grove at .0470
 
Maybe case capacity? Have you tried the load in a different brand case? There can be a substantial difference in my experience. I have found Federal brass to have a smaller capacity than RP and WIN brass.
 
Just because the bullet manufacturer says it is 178 gr how do you know? plus or minus 2 or 3 grains at 178 could mean much more at 40 grains. Clean the pan and arm of your scale and zero it, then weigh your bullet then you may see a difference. 40 gr of Varget is a minimum load.
 
Not all rifles/barrels behave the same.
That's assuming you have no water(rain) or lube in your chamber and that your brass/chamber are dry.
 
labrador76 said:
Maybe case capacity? Have you tried the load in a different brand case? There can be a substantial difference in my experience. I have found Federal brass to have a smaller capacity than RP and WIN brass.
Click to expand...


We have a bingo and I would be willing to bet that labrador76 is almost as smart and good looking as I am, did I mention modest too..:evil: (good call labrador76) ;)



Pierre-Luc

If you have a fired case that you have not resized yet then weigh this case, then fill the case with water level with the mouth of the case and let us know what you find.

The average is 56 grains of H2O case capacity.

I'm guessing but I think the Prvi Partizan cases will have "less" case capacity because the cases are made to military standards and are thicker in the base web area.

Cartridge Case Capacities
http://kwk.us/cases.html

Below are two .223/5.56 cases one with 30.6 grains of H2O capacity and the other with 28.8 grains of H2O case capacity and over 7,000 psi difference in chamber pressure.

288_zps26698a67.jpg


308_zpsf81bb4cc.jpg


Any time any reloading component is changed the load should be reduced and a new work up load be developed.

If you always start at the bottom and work up your load you will learn a great deal about "YOUR" rifle by reading the primers and checking the case for over pressure signs.
 
iceman2 said:
Just because the bullet manufacturer says it is 178 gr how do you know? plus or minus 2 or 3 grains at 178 could mean much more at 40 grains. Clean the pan and arm of your scale and zero it, then weigh your bullet then you may see a difference. 40 gr of Varget is a minimum load.
Click to expand...

It would likely mean less error at a lower weight.
How is your throat? Is your brass neck too thick? That seems like a very low load to have pressure issues. I think it would be very hard to fit enough uncompressed Varget in a 308 case to cause pressure signs
 
182.5 grains empty case fired in my rem 700 ... 237.7 filed with water. which mean 55.2grain of water this is for a s&b case
181.8 grain empty case fired in my rem 700 ... 236..6 filled with water . which mean 54.8 of water ... this is a Federal case ( F . C stamp)
 
bigedp51 said:
We have a bingo and I would be willing to bet that labrador76 is almost as smart and good looking as I am, did I mention modest too..:evil: (good call labrador76) ;)



Pierre-Luc

If you have a fired case that you have not resized yet then weigh this case, then fill the case with water level with the mouth of the case and let us know what you find.

The average is 56 grains of H2O case capacity.

I'm guessing but I think the Prvi Partizan cases will have "less" case capacity because the cases are made to military standards and are thicker in the base web area.

Cartridge Case Capacities
http://kwk.us/cases.html

Below are two .223/5.56 cases one with 30.6 grains of H2O capacity and the other with 28.8 grains of H2O case capacity and over 7,000 psi difference in chamber pressure.

288_zps26698a67.jpg


308_zpsf81bb4cc.jpg


Any time any reloading component is changed the load should be reduced and a new work up load be developed.

If you always start at the bottom and work up your load you will learn a great deal about "YOUR" rifle by reading the primers and checking the case for over pressure signs.
Click to expand...

Still, run Varget in a 308 case, I don't think you would fit enough in there to reach saami max, can you? Given with high start pressure from a bullet in the lands and too small neck diameter for a given case neck, sure, but I think something else is at work here.....
 
this is a new gun with under 300 rounds (rem 700 sps aac-sd )how do i check my throat? my neck mesure .335 with a bullet seated . .344 fired

this is a starting load ( lyman call for 39.5 but i jumped to 40 )
 
The start load for the 178 grain A-Max in the Hornady manual is 32 grains of Varget and 43.2 is Max

You said you measured the base diameter at .470 after it was fired "BUT" what was it before it was fired, any increase over .001 is excess pressure.
 
.469 unfied , .470 fired ... so i believe my book was wrong , i found the hornady manual page online ... i does start a 32grains starting load for 178g a-max ... should have read more source ...
 
This is where a Chrony helps. Hi pressure signs with high velocity means too much powder for the case.


Hi pressure with ordinary velocity means a tight neck chamber or the powder is not what you think.

Any chance your powder got contaminated with a faster powder?
 
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