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> Precision long range hunting and shooting
> velocity increase via seating depth?
velocity increase via seating depth?
@ 07:33 am (GMT) |
Thomas Kitchengood evening gentlemen.done some load testing today in my 308 norma mag. i tested seating depth using Nathans method in the reloading book. .5 deeper seating depth gave me 140fps velocity increase and 1mm gave me 180fps over original load. first time i have played around with seating depth as i normally have short mags so little perplexed about the velocity increase. cheers for any help |
Replies
@ 01:05 am (GMT) |
Paul LevermanRe: velocity increase via seating depth?No expert here, but maybe the extra depth is acting like a freebore section. |
@ 05:56 am (GMT) |
mark whiteleyRe: velocity increase via seating depth?Thomasthe internal volume of the cartridge is decreased so higher pressure I have seen this while playing with quickload best regards mark |
@ 08:02 am (GMT) |
Hamish GibbsRe: velocity increase via seating depth?If Paul's no expert then I'm a deer with no eyes, Norma mag case size surely its more to do with freebore than a little less case capacity by seating .5 to 1 deeper? Sure you were not jammed to start with? Thanks for sharing Thomas has been something that has been on my mind a little about playing with freebore and bullets with long bearing surfaces. Will be interested in what replies you get. |
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@ 08:10 am (GMT) |
Hamish GibbsRe: velocity increase via seating depth?Sorry mark was certainly not writing off your knowledge, im all ears, just questioning which would effect velocity the most as I understand it both could have an effect. |
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@ 11:54 am (GMT) |
mark whiteleyRe: velocity increase via seating depth?not a problem HamishThomas if you would like me to put your load into quickload and do a simulation to see if I can reproduce what has happened could you give a little more information, such as projectile brand and weight, powder used and weight, oal from tip to base and the original velocity. there are other things to factor in to fine tune quickload but for this that will be enough if this doesn't work at least we will know what it's not best regards mark |
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@ 04:57 am (GMT) |
Thomas KitchenRe: velocity increase via seating depth?thank you for your comments everyone.Mark that would be good if you don't mind original load is 69.2gr of 2213sc and a 208grain amax with a coal of 87mm/3.425 inches giving velocity of 2690fps jump load was 69.5gr of 2213sc with 208gr with coal of 86/3.385 with velocity of 2880fps. from best of my knowledge it wasn't jammed into lands, no stiffness on bolt when closing on live round or extracting live round |
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@ 11:40 am (GMT) |
mark whiteleyRe: velocity increase via seating depth?Hi Thomashere we go 308 norma mag 208 gr amax 86mm oal 69.5 gr 2213sc 2880fps 26" barrel and the results are: 86mm 59544psi 2881fps 85.5mm 60163psi 2888fps 85mm 60797psi 2895fps if you have a 26" barrel you are right on a node at 85mm (so quickload says) barrel time 1.329 the higher velocity from deeper seating is not drastic enough for it to be the problem sorry that it looks like it cant be the culprit but at least we know now what it's not maybe what Paul said has more to do with it good luck with it anyway best regards Mark |
@ 03:38 pm (GMT) |
Bryan WebsterRe: velocity increase via seating depth?Hello folks. I was wondering if it were possible it might be an issue with the chronograph being used. A while back on a bright sunny day I got some readings on my shooting chrony that seemed suspicious. Another shooter offered me the use of his Magnetospeed V3 chronograph and it was a fault with my setup. Without that I would have still been pondering...but normally I have seen no issue with mine other than having to oick the right conditions or rather than use it the normal way having to use the LED lit cover to remove environmental effects.Just a thought. |
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@ 08:19 pm (GMT) |
Thomas KitchenRe: velocity increase via seating depth?thank you for that Mark really appreciated.just looking at my target for 86mm i had vertical stringing but good accuracy and i know my ES was pretty bad so might muck around with it some more. at 2880fps with 208gr amax i might be giving a few 300 win mags a run for there money if i can find a nice load. Bryan i did wonder that myself but the next day i had mate shoot his gun through my chrony while he had his magno one on his gun the difference between the to was 6fps so im happy its not playing up, if it was the day before im not sure. i might be a lot closer to the lands then i thought who knows time for some investigations |
@ 10:41 pm (GMT) |
Martin TaylorRe: velocity increase via seating depth?Yes, sounds like your Norma is having a "free lunch" on the jump Thomas which is a bonus & your not wrong about giving some WM's a run! I don't have my figures but your up there.Grant may have the throat measurement that he cut to that will give you a bit of a guide. Same as Bryan has found, with the right set up our Chrono is hard to fault most days. Being most affected by patchy cloud. |
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@ 10:54 pm (GMT) |
Hamish GibbsRe: velocity increase via seating depth?Thanks for that mark, most interesting seeing the pressure change.Guess the obvious thing to do would be to waste a couple of rounds, duplicate your start load and fire them spaced randomly through your next sesh to verify? If you wanted to rule out a chrony error. |
@ 04:54 pm (GMT) |
murray sandersRe: velocity increase via seating depth?Hello , I just purchased a Mauser 66 in 300 Weatherby Mag , I checked the free bore with a dummy round using Norma brass and a .308 diam 168 grain Nosler balisic tip bullet , the measurement was OAL 3.913 inches which means i have a huge amount of free bore before hitting the lands , I was going to give the bullet a short jump into the lands but it is sticking out to far over max OAL which is 3.560 inches , not knowing anything about Weatherby cartridges and rifles maybe some one could tell be why they have so much freebore and should i just seat the bullet to the max book dimension |
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@ 07:06 pm (GMT) |
Thomas KitchenRe: velocity increase via seating depth?i should probably do an update since the topic came up again.Nathan suggested i check my coal again, and what do you know he was right on the money. the coal i hadn't checked i just went i what i thought was the reamer specs so i was decent distance off the lands to begin with and ended miles off them which gave me so much extra velocity. have changed to 225gr eld-m now and have great results with 1mm jump. Murray the weatherby's have a freebore design to give extra velocity. i would recommend Nathan's books as they cover this a great deal. you need to seat bullet no longer out then start of boat tail to bottom of case neck. also do wonder if you should look at your projectile choice, im not sure what your hunting but the 168 ballistic tip might be bit of a varmint grenade out of a weatherby mag |
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