Jump or no jump
03-29-2015, 04:10 AM
#1
Nontypical Buck
Thread Starter
Join Date: Feb 2003
Location: Pa
Posts: 4,647
Jump or no jump
Kind of curious how many people load there bullets off the L&G or kissing the L&G???
I've started mine 30 thousands off the lands and work my way closer in 5 shot group increments... How about you guys???
I've started mine 30 thousands off the lands and work my way closer in 5 shot group increments... How about you guys???
03-29-2015, 05:25 AM
#2
Nontypical Buck
Join Date: Sep 2010
Posts: 1,834
Depends on what the rifle will be used for and who is using it. My personal rifles, benchrest as well my Varmint are loaded to with in .010 and some closer.
You did not mention what kind of dies you are using or bullets. Some bullets have a longer ogive creating an issue with getting them close to the lands. I use Foster Micrometer for my Benchrest 6mm-284 and Redding Micrometer for my .308, .220 Swift and 22-250. The rest are loaded to within .010 and 99% of the time seem to like it over longer.
You did not mention what kind of dies you are using or bullets. Some bullets have a longer ogive creating an issue with getting them close to the lands. I use Foster Micrometer for my Benchrest 6mm-284 and Redding Micrometer for my .308, .220 Swift and 22-250. The rest are loaded to within .010 and 99% of the time seem to like it over longer.
03-29-2015, 03:04 PM
#4
Nontypical Buck
Join Date: Feb 2003
Location: Alberta Canada
Posts: 1,081
Impossible to touch the lands with my Weatherbys. I did touch them with my silhouette rifles, but the pressure spike made me back them off to .005 The accuracy when touching was incredible, but I had to back down 5 grains before the pressure spike was acceptable.
03-29-2015, 08:36 PM
#5
Nontypical Buck
Join Date: Oct 2009
Location: Kansas
Posts: 3,902
Hunting rifles should have a jump. Largely, that's to let you load and unload without worrying about pulling the bullet if it were jammed into the lands. It also gives you a bit of a "safety factor" for thermal versatility in a hunting rifle that might find itself hunting a very very cold morning (powder cooks off a lot slower) or hunting a mild and sunny afternoon. A load that's safe in cold weather when kissing the lands might blow your rifle apart on a 60degree day.
I know that I don't have any loads in my "cook book" that run a 30thou jump. I start at 20 thou off to do my early load work, then work my way in, usually end up between 0.015 to 0.005 jump, depending on my application and how often I tend to clean a given rifle. I used to jam 10thou in my bench rest rifle, but I don't load any that way anymore.
I know that I don't have any loads in my "cook book" that run a 30thou jump. I start at 20 thou off to do my early load work, then work my way in, usually end up between 0.015 to 0.005 jump, depending on my application and how often I tend to clean a given rifle. I used to jam 10thou in my bench rest rifle, but I don't load any that way anymore.
03-30-2015, 05:06 AM
#6
Nontypical Buck
Join Date: Dec 2009
Posts: 1,780
Hunting rifles should have a jump. Largely, that's to let you load and unload without worrying about pulling the bullet if it were jammed into the lands. It also gives you a bit of a "safety factor" for thermal versatility in a hunting rifle that might find itself hunting a very very cold morning (powder cooks off a lot slower) or hunting a mild and sunny afternoon. A load that's safe in cold weather when kissing the lands might blow your rifle apart on a 60degree day.
One small addition: mono-metal bullets (Barnes, etc.) need to be much further off of the lands than most.
03-31-2015, 03:52 AM
#8
Typical Buck
Join Date: May 2009
Location: Colorado
Posts: 797
I wish I was good at explaining things. This is my last stage of my reloading to find the sweet spots. Maybe you already know how to measure how much jump your rifle has vs standard COL depths. You can really tune a bullet with seating depths but also spend a lot of range time fine tuning loads. I would start trying to tune a load at 300 yards it will show you a lot more of what your groups are actually doing than shooting at 100 yards.
First thing I would do is a ladder test at 300 yards with different powder charges and the standard COL then think about bullet jump. Here again I wish I was less redneck and more of a intellectual. But alas where two or more of your powder charges come close to each other in the string of shooting your getting closer to your sweet spot charge.
Nomercy or Ridge could explain this better.
First thing I would do is a ladder test at 300 yards with different powder charges and the standard COL then think about bullet jump. Here again I wish I was less redneck and more of a intellectual. But alas where two or more of your powder charges come close to each other in the string of shooting your getting closer to your sweet spot charge.
Nomercy or Ridge could explain this better.
04-01-2015, 08:52 AM
#9
Nontypical Buck
Join Date: Oct 2009
Location: Kansas
Posts: 3,902
I wish I was good at explaining things. This is my last stage of my reloading to find the sweet spots. Maybe you already know how to measure how much jump your rifle has vs standard COL depths. You can really tune a bullet with seating depths but also spend a lot of range time fine tuning loads. I would start trying to tune a load at 300 yards it will show you a lot more of what your groups are actually doing than shooting at 100 yards.
First thing I would do is a ladder test at 300 yards with different powder charges and the standard COL then think about bullet jump. Here again I wish I was less redneck and more of a intellectual. But alas where two or more of your powder charges come close to each other in the string of shooting your getting closer to your sweet spot charge.
Nomercy or Ridge could explain this better.
First thing I would do is a ladder test at 300 yards with different powder charges and the standard COL then think about bullet jump. Here again I wish I was less redneck and more of a intellectual. But alas where two or more of your powder charges come close to each other in the string of shooting your getting closer to your sweet spot charge.
Nomercy or Ridge could explain this better.
