Three ways to find the lands - Page 2

hounddawg · October 18, 2021, 02:37 PM

some call it touch, some call it jam. Regardless it is a datum or reference point from which adjustments to the base to ogive for any particular load are made from. The ogive is another datum point which is just a arbitrary reference point since any two inserts for a comparator may or may not be the same diameter. When I first got into 6BR's I used my .22 cal insert for the longest time to measure and adjust my bullet seating.

@ bart - irrelevant unless you subscribe to the belief that you have to know the exact distance down to the .00001 of a inch. As long as the adjustments are made in comparison to the original measurement. The amount of erosion per shot will be determinate on a number of factors such as the temperature of the powder used and more importantly what cartridge. A 22 -250 firing a 55 gn bullet might use 36 gn's of Varget and have a barrel life of 900 - 1000 rounds before burnout while a .223 Rem would only use 25 gns of Varget and have a barrel life of 3000 - 4000 rounds.

Myself when I notice my accuracy eroding I will drop down to 100 yards and test seating again working my way out from the previous seating depth .003 at a time until I find another accuracy point. A trick I learned from watching Erik Cortina videos

Bart B. · October 18, 2021, 03:23 PM

I think accuracy to a couple thousandths inch is good enough.

My 308 Winchester chamber throats advanced about .001 inch every 3 dozen shots. Acceptable accuracy for 3000 to 3500 rounds

hounddawg · October 18, 2021, 03:38 PM

Bart I really do not measure after the first time. I just let the holes in the paper tell me what I need to know. I know what I normally shoot, I know when it drops off time it is to move the seating out a few thousandth.

Bart B. · October 18, 2021, 04:11 PM

I've soft seated bullets for single round loading in bolt action rifles so they seat deeper when loaded. They've all produced best accuracy that way.

hounddawg · October 20, 2021, 10:57 AM

I was prepping for a load test tomorrow and got to thinking about this thread. I used the Horandy to check five 105 6 MM bergers in one of my rifles. Using the .24 comparator insert the numbers were 2.811, 2.812, 2.810, 2.810 and 2.812. I decide to call 2.811 touch, or jam but I think I will call it zero. I seated the bullets for this charge test at 2.800 since my other barrel likes that bullet .010 - .015 from "zero". Is that bullet really .010 - .012 from the throat or lands? No idea but it gives me a reference point so if this barrel does not like the bullet seated .012 from zero and I need to adjusting seating depth I can go out to 2.808 with no fear of a bullet being stuck in the throat in case of a squib, or I can go to 2.797, 2.794, or 2.790 if I want to try more of a jump. To me that is the only purpose of "finding the lands"

October 18, 2021, 02:37 PM	#26
hounddawg Senior Member Join Date: March 1, 2009 Posts: 4,232	some call it touch, some call it jam. Regardless it is a datum or reference point from which adjustments to the base to ogive for any particular load are made from. The ogive is another datum point which is just a arbitrary reference point since any two inserts for a comparator may or may not be the same diameter. When I first got into 6BR's I used my .22 cal insert for the longest time to measure and adjust my bullet seating. @ bart - irrelevant unless you subscribe to the belief that you have to know the exact distance down to the .00001 of a inch. As long as the adjustments are made in comparison to the original measurement. The amount of erosion per shot will be determinate on a number of factors such as the temperature of the powder used and more importantly what cartridge. A 22 -250 firing a 55 gn bullet might use 36 gn's of Varget and have a barrel life of 900 - 1000 rounds before burnout while a .223 Rem would only use 25 gns of Varget and have a barrel life of 3000 - 4000 rounds. Myself when I notice my accuracy eroding I will drop down to 100 yards and test seating again working my way out from the previous seating depth .003 at a time until I find another accuracy point. A trick I learned from watching Erik Cortina videos __________________ “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

October 18, 2021, 03:23 PM	#27
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	I think accuracy to a couple thousandths inch is good enough. My 308 Winchester chamber throats advanced about .001 inch every 3 dozen shots. Acceptable accuracy for 3000 to 3500 rounds Last edited by Bart B.; October 18, 2021 at 03:29 PM.

October 18, 2021, 03:38 PM	#28
hounddawg Senior Member Join Date: March 1, 2009 Posts: 4,232	Bart I really do not measure after the first time. I just let the holes in the paper tell me what I need to know. I know what I normally shoot, I know when it drops off time it is to move the seating out a few thousandth. __________________ “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

October 20, 2021, 10:57 AM	#30
hounddawg Senior Member Join Date: March 1, 2009 Posts: 4,232	I was prepping for a load test tomorrow and got to thinking about this thread. I used the Horandy to check five 105 6 MM bergers in one of my rifles. Using the .24 comparator insert the numbers were 2.811, 2.812, 2.810, 2.810 and 2.812. I decide to call 2.811 touch, or jam but I think I will call it zero. I seated the bullets for this charge test at 2.800 since my other barrel likes that bullet .010 - .015 from "zero". Is that bullet really .010 - .012 from the throat or lands? No idea but it gives me a reference point so if this barrel does not like the bullet seated .012 from zero and I need to adjusting seating depth I can go out to 2.808 with no fear of a bullet being stuck in the throat in case of a squib, or I can go to 2.797, 2.794, or 2.790 if I want to try more of a jump. To me that is the only purpose of "finding the lands" __________________ “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 Last edited by hounddawg; October 20, 2021 at 09:28 PM.

October 18, 2021, 04:11 PM	#29
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	I've soft seated bullets for single round loading in bolt action rifles so they seat deeper when loaded. They've all produced best accuracy that way.