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Big jump
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<blockquote data-quote="tim_w" data-source="post: 1452347" data-attributes="member: 11132"><p>Also guys unless I am missing something. JE you are talking 0.036 with some people wanting max vel jumping a max of 0.100 in your post and saying the first number is about right for bullet jump and thats based even on the .189 freebore nonsaami ptg chamber spec sheet not zero freebore saami but the op is stating 0.330 so not 36 thou (0.036) but 360 thou (0.360) throat thats getting **** near 3/8" of jump. No way thats a normal freebore let alone no freebore with a 1.5 degree leade. With that kind of jump many bullet could be fully unsupported before it ever touches the lands in the leade. His jump is more than his 30 caliber bullet is in diameter !!!</p><p></p><p>Someone throated the hell out of that chamber!!</p><p></p><p></p><p>Thork,</p><p></p><p>What were you using to measure freebore? A bullet ? If so which or was a freebore tool which has a full groove diameter/full caliber insert which hits right where the leade starts the 1.5 angle till reduced to full bore/ lands diameter?</p><p></p><p>One thing for sure is he did not use a saami spec full reamer but either a custom or a throating reamer afterwards. Your old barrel based on your stament about the 185 and 168 sounds like a SAAMI chamber. </p><p></p><p>Using the 185 vld hunter based on your numbers. That bullet has a 0.214" BT. If you set it to have it just kissing the lands to even 0.010 you are only a bit over 0.100 of bullet bearing surface to case neck contact to hold neck tension. I am ok with 1/2 cal on many bullets but when you start getting below that with these longer neck bullets for hunting to me thats a no go..</p><p></p><p>Also you have to consider what is going to happen when the throat has its intial eroding in a few hundred rounds. If it were me I would be taking it back to your smith especially if you did not ask for any special throating he should have given you a SAAMI spec unless otherwise discussed. Have him cut the barrel back enough to recut the chamber enough to reset that freebore to give you a min jump for the coal your mag allows with a bit of room to chase the lands a smig. </p><p></p><p>These days the only Bergers I shoot are hybrids/EOLs and they are all very tolerant of jump. I start with the bullet in the case as far as I am willing to go based on case neck length and needed vel mag max coal etc and have freebore leade set to allow a 0.015 jump which I have found is the min I consistently am able to get great accuracy with many different hybrid calibers and weights. That way I have the max mag space and neck to bullet bearing surface to chase erosion and can still get very good acccuracy with jumps up to 0.80 sometimes a bit more. By then a good portion of the bore is coooked and a new barrel is needed anyways. </p><p></p><p>Sorry I can not be of help with vlds. When I shot them I found they shot best at a specific jump that seemed to vary from barrel to barrel and different weights and calibers etc.</p></blockquote><p></p>
[QUOTE="tim_w, post: 1452347, member: 11132"] Also guys unless I am missing something. JE you are talking 0.036 with some people wanting max vel jumping a max of 0.100 in your post and saying the first number is about right for bullet jump and thats based even on the .189 freebore nonsaami ptg chamber spec sheet not zero freebore saami but the op is stating 0.330 so not 36 thou (0.036) but 360 thou (0.360) throat thats getting **** near 3/8” of jump. No way thats a normal freebore let alone no freebore with a 1.5 degree leade. With that kind of jump many bullet could be fully unsupported before it ever touches the lands in the leade. His jump is more than his 30 caliber bullet is in diameter !!! Someone throated the hell out of that chamber!! Thork, What were you using to measure freebore? A bullet ? If so which or was a freebore tool which has a full groove diameter/full caliber insert which hits right where the leade starts the 1.5 angle till reduced to full bore/ lands diameter? One thing for sure is he did not use a saami spec full reamer but either a custom or a throating reamer afterwards. Your old barrel based on your stament about the 185 and 168 sounds like a SAAMI chamber. Using the 185 vld hunter based on your numbers. That bullet has a 0.214” BT. If you set it to have it just kissing the lands to even 0.010 you are only a bit over 0.100 of bullet bearing surface to case neck contact to hold neck tension. I am ok with 1/2 cal on many bullets but when you start getting below that with these longer neck bullets for hunting to me thats a no go.. Also you have to consider what is going to happen when the throat has its intial eroding in a few hundred rounds. If it were me I would be taking it back to your smith especially if you did not ask for any special throating he should have given you a SAAMI spec unless otherwise discussed. Have him cut the barrel back enough to recut the chamber enough to reset that freebore to give you a min jump for the coal your mag allows with a bit of room to chase the lands a smig. These days the only Bergers I shoot are hybrids/EOLs and they are all very tolerant of jump. I start with the bullet in the case as far as I am willing to go based on case neck length and needed vel mag max coal etc and have freebore leade set to allow a 0.015 jump which I have found is the min I consistently am able to get great accuracy with many different hybrid calibers and weights. That way I have the max mag space and neck to bullet bearing surface to chase erosion and can still get very good acccuracy with jumps up to 0.80 sometimes a bit more. By then a good portion of the bore is coooked and a new barrel is needed anyways. Sorry I can not be of help with vlds. When I shot them I found they shot best at a specific jump that seemed to vary from barrel to barrel and different weights and calibers etc. [/QUOTE]
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