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Too much jump?

 
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  #1  
Old 08-04-2013, 09:31 PM
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Location: West Central, Idaho
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Too much jump?

How much jump is too much jump? I'm shooting a savage 111 long-range hunter in 7 mm. I measured my total overall length and I can run 3.421 COAL. When I load to bergers specifications, i'm coming up with the jump of .136 in my rifle

I've shot some handloads that are to berger specs lengthwise they seem to shoot really nice conversely I've shot HSM which puts the bullet closer to the LANs, can't remember the specific dimensions they didn't group so well.

Anyways I know there's more to consider than just the jump between these two, accuracy wise. I plan to do the test recommended in the berger manual, but if this gun likes jump, where is the limit?

Also if anybody has any load data for this gun I would love to compare some notes.

Just started into reloading and as I thought I'm falling deep down the rabbit hole, I can never do anything in moderation.

Last edited by Iclimb; 08-04-2013 at 10:32 PM.
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  #2  
Old 08-04-2013, 10:34 PM
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Join Date: Nov 2010
Location: Clovis, NM
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Re: Too much jump?

I'm right with you on figuring this out, but I think you have to consider that the more jump you have, the less case capacity you have. Less case capacity = higher pressure for a given amount of powder, equals wasted potential. Check your Berger manual for another article by Litz that talks about taking advantage of longer throat lengths - the longer you can load your bullet before hitting the lands, the more case volume - larger volume allows increased powder charge (and velocity) without increasing pressure as much. The lower you seat the bullet into the case, the more you reduce the theoretical maximum velocity for the components you select. Ideally, I *think* you'd like a powder that fills the case 100% and burns 100% as the bullet travels down your bore, yields maximum velocity over all other powders with an acceptable pressure, AND that such a recipe yields a bullet velocity that miraculously equates to your barrel's natural harmonic "node." If I could get those variables to line up for all my rifles, I think I'd be cooking with grease...I suppose you could offset the lower case capacity with a faster burning powder? I'm over my head though...

On the other hand, when you go the opposite direction and seat a bullet into the lands, you can create a pressure spike, or so my reloading manuals tell me (including the Berger). Wilderness Means suggests always developing max loads with bullets seated .01" into the lands for this reason - good info on his web page, just Google.

Bottom line, if your case neck goes beyond your bullet's ogive, I'd say you went too far If anyone sees anything "crazy" in my spiel, please advise and correct! Good luck!
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  #3  
Old 08-05-2013, 07:59 PM
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Location: Michigan
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Re: Too much jump?

I follow the lead of the rifle. If it shoots best at loading manual OALs, that's where I'd run her. My practical experience is that usually 10 to 50 thou is the range I end up in. I do have a rifle that only likes Bergers at 0.145". That's where I load it!
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  #4  
Old 08-05-2013, 08:58 PM
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Re: Too much jump?

The answer to "How much jump is too much jump?" is the same as for "how much jam is too much jam?". 'Too much' of any setting is that which produces worst accuracy than just right.

For long range hunting your focus should be on accuracy, and not maximum velocity or book values(which are meaningless).
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  #5  
Old 08-06-2013, 09:16 AM
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Re: Too much jump?

I agree I could care less about speed as of the moment looking for consistenct and accuracy I'll adjust for whatever velocity the combo yields. I guess I was mostly concerned if too much jump, seating the bullet too far back would create a dangerous situation in the gun besides pressures of course.
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  #6  
Old 08-06-2013, 09:12 PM
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Re: Too much jump?

Is your setting putting bullet bearing into neck-shoulder junction?
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  #7  
Old 08-06-2013, 10:44 PM
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Re: Too much jump?

Interesting subject. IMO, whatever the rifle likes up to the point where you can't load them in your magazine anymore. My Savage 308 likes the standard COAL whereas my 338 likes them long, to the point where they just fit the magazine. There are guys on here that load their 338's to the lands but that eliminates the magazine and makes the rifle a single feed. Myself, I like the option of 5 in the magazine and one in the chamber.

My rule of thuimb is load ladder a test group and seat at different lengths to see what your particular weapon likes.
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