primers - Page 2

hounddawg · August 27, 2020, 03:37 PM

what Nick said, hard extraction is a definite warning sign

sako2 · August 27, 2020, 08:49 PM

Yes i did back it down to my original charge. Trying find out why I lost velocity and my es is 70 fps. Unclenick I am using adg brass. If I remember right the ones with hard extraction have 12 firings on them.

**Unclenick** · September 2, 2020, 09:04 PM

Sako2,

Velocity decreasing as charge increases is another high pressure sign. What happens when pressure gets high enough is the chamber itself starts to stretch (what allows the brass to expand enough past it's yield point for the steel to snap back down on it and make extraction sticky). The stretching messes up the combustion volume and produced gas quantity ratio, dropping final velocity by not burning the powder as quickly as the bullet goes down the barrel as the increase in charge would do without the stretch. That is causing acceleration and therefore the velocity to lag. The stretching of the chamber is very accurately proportional to pressure, so any shot-to-shot pressure variation makes the stretch vary as well as its effects. That's what makes the velocity spread increase.

hounddawg · September 2, 2020, 09:14 PM

Thanks Nick, that is my something new for the day. I have often wondered why near the top of my load tests I started seeing diminishing returns comparing velocity to the of the amount of powder being used, now I know

sako2 · September 3, 2020, 04:09 PM

I'm 8 tenths of a gn under the the max charge and right at the velocity for the data I have. I can lift the bolt handle with the back side of my hand. Most shots are within 20fps of each other. Then I get 1 that's 50fps faster then a couple shots I get 1 50fps slower.

August 27, 2020, 03:37 PM	#26
hounddawg Senior Member Join Date: March 1, 2009 Posts: 4,232	what Nick said, hard extraction is a definite warning sign __________________ “How do I get to the next level?” Well, you get to the next level by being the first one on the range and the last one to leave.” – Jerry Miculek

September 2, 2020, 09:04 PM	#28
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,738	Sako2, Velocity decreasing as charge increases is another high pressure sign. What happens when pressure gets high enough is the chamber itself starts to stretch (what allows the brass to expand enough past it's yield point for the steel to snap back down on it and make extraction sticky). The stretching messes up the combustion volume and produced gas quantity ratio, dropping final velocity by not burning the powder as quickly as the bullet goes down the barrel as the increase in charge would do without the stretch. That is causing acceleration and therefore the velocity to lag. The stretching of the chamber is very accurately proportional to pressure, so any shot-to-shot pressure variation makes the stretch vary as well as its effects. That's what makes the velocity spread increase. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

September 2, 2020, 09:14 PM	#29
hounddawg Senior Member Join Date: March 1, 2009 Posts: 4,232	Thanks Nick, that is my something new for the day. I have often wondered why near the top of my load tests I started seeing diminishing returns comparing velocity to the of the amount of powder being used, now I know __________________ “How do I get to the next level?” Well, you get to the next level by being the first one on the range and the last one to leave.” – Jerry Miculek

August 27, 2020, 08:49 PM	#27
sako2 Senior Member Join Date: April 12, 2009 Posts: 766	Yes i did back it down to my original charge. Trying find out why I lost velocity and my es is 70 fps. Unclenick I am using adg brass. If I remember right the ones with hard extraction have 12 firings on them.

September 3, 2020, 04:09 PM	#30
sako2 Senior Member Join Date: April 12, 2009 Posts: 766	I'm 8 tenths of a gn under the the max charge and right at the velocity for the data I have. I can lift the bolt handle with the back side of my hand. Most shots are within 20fps of each other. Then I get 1 that's 50fps faster then a couple shots I get 1 50fps slower.