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-   -   Jump or no jump (https://www.huntingnet.com/forum/reloading/398500-jump-no-jump.html)

Mr. Longbeard 03-29-2015 04:10 AM

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???

SecondChance 03-29-2015 05:25 AM

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.

Mr. Longbeard 03-29-2015 12:54 PM

Well I'm shooting 7mm-08 with a Sierra Game King... I'm using a ogive gauge that goes on my calipers...

redgreen 03-29-2015 03:04 PM

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.

Nomercy448 03-29-2015 08:36 PM

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.

Big Uncle 03-30-2015 05:06 AM


Originally Posted by Nomercy448 (Post 4192033)
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 could not agree more.

One small addition: mono-metal bullets (Barnes, etc.) need to be much further off of the lands than most.

buffybr 03-30-2015 11:44 AM


Originally Posted by redgreen (Post 4191996)
Impossible to touch the lands with my Weatherbys. . .

Yep, the controlling factor in my .300 Weatherby Vanguard is the inside dimension of the magazine.

Blackelk 03-31-2015 03:52 AM

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.

Nomercy448 04-01-2015 08:52 AM


Originally Posted by Blackelk (Post 4192172)
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.

Seems like you explained it purty well Blackelk - same process I use. I shoot groups with different bullets to line out what bullet my barrel likes best, then ladder test with different powders with a fixed 20thou jump, then once I pick a powder and charge weight, I work longer towards the lands to find my best accuracy.


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