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Thread: Speed vs pressure

  1. #1
    Member
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    Speed vs pressure

    A question for the gurus...
    I have a load developed, and I know itís muzzle velocity. If I use a different brand of case (or a different primer) with the same powder and projectile, if Iím getting the same speed can I assume that the pressure is the same? I realise that to achieve the same speed the powder charge is likely to be different between the loads.
    Another way of looking at it is...does it take the same pressure to push a certain projectile at a certain speed (out of the same barrel using the same powder)?

  2. #2
    Member Tikka7mm08's Avatar
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    Mar 2012
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    Good question. I would have thought same speed same pressure. I've been using RE17 and CFE223 in 308 and they are pushing the 168gn BT at almost identical speeds...but the RE17 "feels" like less pressure...so I wonder if pressure curves - how quick max pressure is achieved - is a key factor.
    hamsav likes this.

  3. #3
    Member Micky Duck's Avatar
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    more importantly
    if you dont own rangefinder and arent twiddlin n fiddlin with dials....speed doesnt matter but pressure sure as hell does.
    Ive been known to use same load with same components and happily switch out brass or projectile without issue...BUT IM NOT RUNNING HOT LOADS.....if you are already at edge of abiss pressure wise dont go changing a thing...if you using a less than maximum load and have no pressure signals, you SHOULD be fine.....and at sub 300 yards a couple of fps isnt going to matter a shit....
    fired a 7 shot group last night (breaking in barrel so lots of time and cleaning between shots) 3 different brands of factory ammunition 2 different weights of projectile and its still a 1.5" group...not bad with 4x scope and rifle Ive now fired 11 times.
    Dama dama and shooternz like this.

  4. #4
    Member
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    Dec 2019
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    Okawa Hawkes Bay
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    Greetings Cigar and All,
    The answer is yes, sort of. John Barsness did an excellent article in Handloader a while back. He found a strong relationship between velocity and pressure and worked up loads with a chronograph with data for the same powder and projectile. As far as cases go a heavier case will have less capacity and will give more velocity and pressure but the same velocity will be close to the same pressure. Cases can vary widely in weight for the same cartridge. I weigh batches of cases prior to loading. Primers are different. Some primers develop more pressure without increases in velocity. I would be careful using Winchester primers, especially their magnum type with stick powders unless listed in the data. I believe that Winchester primers have been formulated for the harder to ignite ball powders. Projectiles are very different. Only data for homogenous projectiles should be used with them. The data is often several grains below that of soft projectiles like the Hornady Interlock. Data for the heavier jacket projectiles like the ABLR is often lower as well so again use the data for those projectiles.
    Regards Grandpamac.
    Tikka7mm08 likes this.

 

 

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