Accuracy=seating depth or tenths of powder

Discussion in 'Reloading' started by johnhhernan, Sep 1, 2015.

  1. johnhhernan

    johnhhernan Well-Known Member

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    I have a question for some of you seasoned LR accurate reloaders.

    What is more important having the exact tenth of grain of powder or being within .005 to .010 of my seating depth.

    The reason I ask is I loaded 51.8 grains of 4831SC powder and that seems to be accurate for my load so I then figure out my seating depth and I consistently come up with a group at 1.5 inches at 550yds which I'm happy with but I loaded up 51.9 by accident and I didn't see a difference in accuracy but if I shoot 51.8 grains of powder and my seating depth is .005 to .010 off of what i'm used to my accuracy grows to about 2.75 inches.

    Now you see why ask what is your experience is in this situation.

    Please enlighten me...

    John Hernan
     
  2. kguzman

    kguzman Member

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    John that's a good question obviously it matters because I see the same behavior on my reloading as far as bullet seating so I've been trying to correct it. looking forward to here what kind of feed back you get
     
  3. rcoody

    rcoody Well-Known Member

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    What bullet?

    In lots of cases you will find an accuracy node as wide a 0.3 of a grain. Consistent charges are what is important and it become more important the longer the range.

    Some bullets (bergers especially) are more sensitive to seating depth than others.

    every barrel is different. you have to find what works
     
  4. FEENIX

    FEENIX Well-Known Member

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    So I don't misconstrue your question, are you saying your seating depth is .0075" + or - .0025" (.005" to .010") off the lands?

    Consistency, consistency, consistency is the key!
     
  5. Mikecr

    Mikecr Well-Known Member

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    My experience leads me to the notion that no amount of powder change produces the affect amplitude of seating change.
    You really need to mind best cartridge base to ogive(CBTO) with every round you assemble. No shortcuts there.
     
  6. FEENIX

    FEENIX Well-Known Member

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    Yep!

     
  7. dsculley

    dsculley Well-Known Member

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    Many hand loaders first test for the perfect powder/charge weight (a course adjustment when done this way) and then fine tune with seating depth. There are those that state this is the wrong method. They say you should pick a beginning test charge, then use this to test for the best seating depth before working on a charge weight. In this method, the seating depth is the course adjustment and the powder charge weight is the fine adjustment. The longer I load, the more I defer to this method. If you test for/select a charge weight first, you are changing the case volume/pressure when you change the seating depth. If you are on a wide node, then you probably won't see a measurable change. If you are one who likes maximum charges then the increase in pressure from seating deeper could be an issue.

    Of course, as was stated in an earlier post, some bullets/guns are more sensitive to seating depth than others. A wider node will be less sensitive to changes in pressure from seating depth changes, but those changes will put you either higher or lower in that node due to the pressure changes. If I first determine my seating depth, then find my OCW node I will be in the center of the node and less likely to be affected by temperature changes.

    So, to answer the original question, they are both important. If the bullet is sensitive to seating depth, that becomes the most important. If the bullet is not sensitive to seating depth and the node you are loading in is narrow, the charge weight becomes the most important.

    FWIW, my 2ยข

    Dennis
     
  8. Mikecr

    Mikecr Well-Known Member

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    A narrow seating window is removed from concern once you set them all the same.
    That bullets shoot best at some particular setting might as well be assumed. If you do full seating testing, you will find THE best place, and no other is 'best'.

    Seating depth is the coarse adjustment, powder the fine adjustment. Anyone who's ever calibrated something knows you adjust coarse first, followed by fine.
    So seating, then powder, then you should go back to seating and tweak it a few thou each way to 'shape' grouping. This final tweak is not tuning or developing(you're past that), and does not affect tune -unless you go beyond a few thou or into/off lands.
    This is where most people screw up load development. They go powder first, then collapse their powder node with seating testing, which at that point is two changes at once. They'll almost always conclude that whatever seating they pulled from their butt to do powder testing -must be best... But there was never a reason for any random chosen seating to be best. That would just be blind luck if it happened.
    The way to find best seating is with a powder load no where near any node. Worst powder load is best for seating testing, and with this the only dramatic changes occur purely from seating adjustments. That's how you find best.
     
  9. ODAVID

    ODAVID Well-Known Member

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    Obviously I hope you are sorting your bullets by weight first, then ogive measurement using a comparator?????

    Doing this along allowed me to get 1/2" at 200 yds. I am still tweeking.

    Best of luck
    ODAVID
     
  10. youngbuck

    youngbuck Well-Known Member

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    Mike,
    How do you determine what powder and how much when you start? Right now I'm working on a 264, well actually 2 of them with matching barrels that got the same reamer. I tried several powders and a few bullets. I took my most accurate powder and my most accurate bullet and then increased powder charge until I got the velocity I wanted without pressure signs. Now I'm adjusting seating depth on that combo. One of the rifles shoots 1/2 MOA out to 500(all we have shot on paper) the other right at 1 MOA, which is why I am tuning my seating depth. In your experience, it shouldnt matter the powder? For instance I tried retumbo and H1000 in both 264s, I got the velocity I was looking for, but my best groups were 2MOA with all the bullets I tried.
     
  11. johnhhernan

    johnhhernan Well-Known Member

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    Yes, I have just recently started to sort bullets=tedious. I was just curious of what's more important seating depth or a tenth of a grain difference. It sounds like seating depth.

    So Next question on seating depth do any of you go and try to define the seating depth by 1000th of an inch?
     
  12. NATE40

    NATE40 Member

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    IMHO case Cartridge Case Capacities play a big part of accuracy I feel more than powder weight, consistency is what you should strive for. a bullet seated deeper can take up powder capacity and could slightly raise the velocity a bullet seated longer can reduce pressure but too long may really increase it, even dangerously . I think weighing brass +/- .5 grain can really improve consistency because brass thickness plays a huge part in case capacity and powder burning consistency more so than powder weight. all 3 should be used when working a really good load for a rifle. Rifle chambers can have slight differences so seating depths should be worked for every rifle separately

    more than loads, barrels, rifles _know your equipment- and once you really know the rifle it will tell you exactly what it want's
     
  13. SidecarFlip

    SidecarFlip Well-Known Member

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    I agree 110%, especially with those frigg'in Bergers.:)

    Powder charge equates to velocity and sometimes spread but seat depth is everything and every stick is different, like fingerprints, no 2 are the same.

    Case in point, 2 of the sticks I'm playing with had their chambers machined in succession, same size barrel blanks, same reamer. Different actions, different stocks but the headspace is within 0.015 of each other. One likes loaded almost to the lands, the other likes to be 0.044 off the lands, same load, same pill, same brass, same primer, same powder, same sizing regimen. No 2 are the same.....

    Gee, I'm only playing with 4 sticks in 2 calibers with 2 brands of brass and 3 wieights of pills from 2 manufacturers with 3 distinctly different powders in 2 charge weights plus 2 different primers (same manufacturer, different strengths) at one time right now.

    hard to keep everything straight Thank goodness for post it notes and MTM cartridge boxes..... and digital calipers or my eyes would cross...

    Far as I'm concerned, get them to shoot sub moa and then play with velocity over a chrono.

    At least I'm not doing the shooting. I'm just loading and cleaning. Someone else is suffering the recoil......
     
  14. SidecarFlip

    SidecarFlip Well-Known Member

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    With Bergers, because of the secant ogive, a change of 0.001 can and will make a difference, which is why I only seat with a front load RCBS Competition Micrometer seater.....

    besides, I hate pinched fingers.....:D

    Other pills aren't as sensative to seat depth.

    I can dial and repeat 0.001 in succession plus the pills load from the top and are supported in a teflon lined alignment sleeve (caliber specific) but you can buy one seater and RCBS will supply you with alignment slides and seater plugs on request direct from them. I make my own seater stems and alignment slides in the shop but again, they are available so you buy one high buck seater and it's good for everything (except I think 50 cal) but I don't want a 50 unless it's a front stuffer....