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Thread: Pressure signs but using the same load

  1. #1

    Pressure signs but using the same load

    Hi people,

    I worked up a load of 35.3gr imr 4164, vmax 87gr in once fired ppu brass and It shot. 0.34 moa with no pressure signs and 3025 on the chrono so I made 60 rounds up.

    Shooting today I had heavy bolt lift and the little crescent on the brass.

    I did notice the coal shifted from 2.625 to 2.619 (using Lee hand loader). So I wonder if that is enough to make a difference in pressure.

    The groups are fine so is it safe to continue shooting the rounds?. I have put 10 through and not all show signs of pressure, maybe 50%.



    This is a group from today's practice.

    The ppu has been fired twice now, does anyone know how many shots I should expect it to be OK for?.

    Thanks all

    Sent from my D5803 using Tapatalk

  2. #2
    Shorter COL means less volume in the case. Less volume means higher pressure....................... warmer temp also means a pressure rise. Sounds like you working right on the ragger edge. Question is do you really need to be doing so?

  3. #3
    Quote Originally Posted by Conure View Post
    Shorter COL means less volume in the case. Less volume means higher pressure....................... warmer temp also means a pressure rise. Sounds like you working right on the ragger edge. Question is do you really need to be doing so?
    Nope don't want to be anywhere near the edge. The suggested max load is 37gr. I noticed signs of pressure at 36.1 which is why I knocked it back to 35.3 as I didn't have any signs at that load and it shot really well but after making up a stack of them.i am.now noticing issues.

    Sent from my D5803 using Tapatalk

  4. #4
    Hi go back to basics, check your scales are accurate, size the brass. Keep the seating depth constant. As said the change in COAL and temperature may be the cause.

  5. #5
    Quote Originally Posted by JamieDenny View Post
    Nope don't want to be anywhere near the edge. The suggested max load is 37gr. I noticed signs of pressure at 36.1 which is why I knocked it back to 35.3 as I didn't have any signs at that load and it shot really well but after making up a stack of them.i am.now noticing issues.

    Sent from my D5803 using Tapatalk
    That is the suggested maximum load in their equipment ................................... not yours! In your rilfe the chamber could be tighter, the leade shorter the bore tighter and your brass might have less internal volume any or all of these will raise pressures. Some of the posts about reloading here really make me wonder about those who are reloading and their ability to read, understand, and follow the safety guidelines. Hell most do not even seem to have a reloading manual so probably have never even read the guidelines!

  6. #6
    I am assuming this is a .243? if so then you may want to try a slower powder, I imagine you will have quite low case fill with this so any variance will be edgey.

    Have a look on here re temperature sensitivity.
    Some are more so than others, N540 is pretty bad for example.

    http://www.hodgdon.com/smokeless/extreme/page2.php#top

    Re the length, 10 thou could make a difference but I doubt so dramatic.
    Have you changed anything else, like the resizing dies?

  7. #7
    Quote Originally Posted by Milligan View Post
    I am assuming this is a .243? if so then you may want to try a slower powder, I imagine you will have quite low case fill with this so any variance will be edgey.

    Have a look on here re temperature sensitivity.
    Some are more so than others, N540 is pretty bad for example.

    http://www.hodgdon.com/smokeless/extreme/page2.php#top

    Re the length, 10 thou could make a difference but I doubt so dramatic.
    Have you changed anything else, like the resizing dies?
    Hi,

    Thanks, it is a very low case fill. Just find it very odd that I worked up a round that has been fine and no signs of pressure for it to then change.
    I wondered if it was because of the ppu brass that has now been fired three times.
    But as you point out, if temp effects it and it has been baking hot these last few days. Maybe that's the issue.

    I have checked everything over again and scales, dies etc.. Were all accurate. Even picked up another set if callipers to be sure.

    Sent from my D5803 using Tapatalk

  8. #8
    Quote Originally Posted by Conure View Post
    That is the suggested maximum load in their equipment ................................... not yours! In your rilfe the chamber could be tighter, the leade shorter the bore tighter and your brass might have less internal volume any or all of these will raise pressures. Some of the posts about reloading here really make me wonder about those who are reloading and their ability to read, understand, and follow the safety guidelines. Hell most do not even seem to have a reloading manual so probably have never even read the guidelines!
    I understand that thank you.
    My question was why would a safe load that was well under a load I had signs of pressure on. That I have been shooting for a month suddenly show signs?.

    My first idea is something has to have changed but I have checked the scales and die (I did this before making up these loads).
    The only other two variables I can think of are the brass and the weather, but I am very new to this.

    I would expect there to be stupid questions on here. It is a place to learn and I would hope anyone would rather ask a stupid question than be dangerous. I for one understand more through discussion than just reading material.

    Thanks

    Sent from my D5803 using Tapatalk

  9. #9
    Quote Originally Posted by JamieDenny View Post
    I understand that thank you.
    My question was why would a safe load that was well under a load I had signs of pressure on. That I have been shooting for a month suddenly show signs?.

    My first idea is something has to have changed but I have checked the scales and die (I did this before making up these loads).
    The only other two variables I can think of are the brass and the weather, but I am very new to this.

    I would expect there to be stupid questions on here. It is a place to learn and I would hope anyone would rather ask a stupid question than be dangerous. I for one understand more through discussion than just reading material.

    Thanks

    Sent from my D5803 using Tapatalk
    not a stupid question at all.
    My money would be temperature.
    I've had this on a .308 and a .260 with viht powders, fine in winter but flat primers in summer.

    If it were me I'd want the case fill to be more like 43-44gr ish, in my experience it produces more consistent results.

  10. #10
    Quote Originally Posted by Milligan View Post
    not a stupid question at all.
    My money would be temperature.
    I've had this on a .308 and a .260 with viht powders, fine in winter but flat primers in summer.

    If it were me I'd want the case fill to be more like 43-44gr ish, in my experience it produces more consistent results.
    Maybe time to look for another powder. It has also just occurred to me that my ammo tin is essentially a hot box (standard ww2 ammo tin). So that sitting in the back of the truck cooking away nicely probably exaggerated the issue.

    As I don't know how many shots this brass is good for I was expecting to change brass and powder at soke point.


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