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Seating depth vs. Charge Weight

Discussion in 'Handloading and Reloading' started by BJung, Nov 12, 2022.

  1. Howa 9700

    Howa 9700 Member

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    If that is right, that would be encouraging. At 200 yards with a bit of crosswind, I was happy with the group of 7,8, 9 and 11. If my real accuracy node is 7 and 8, I'm twice as good as I thought.

    Always amazes me what experienced eyes can see that I can't.
     
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  2. South Prairie Jim

    South Prairie Jim Member

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    9 is unstable and number 11 is outside of that node.
    JMHO
     
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  3. Varminterror

    Varminterror Member

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    Don’t sweat the accuracy of your powder dispensing method too much. Specifically, getting within +/-0.1grn isn’t actually crude measurement, as the sensitivity of the result to varying charge weight is actually very, very low.

    I provided specific details on this particular page of a thread some time ago as to the sensitivity of group size to powder charge accuracy. Whether a shooter is loading to the nearest kernel (~0.02grn) or nearest 1/10th of a grain, the result is only slightly greater than 1 click’s worth of adjustment on the scope at 1000yrds.

    The solution is rather simple - load in a node. That cuts the influence to near zero regardless of whether you’re loading +/-1 kernel or +/-0.1grn. This analysis is rather the WORST CASE SCENARIO where a shooter unwittingly chose an antinode instead of a node, and has huge velocity deviations.

    https://www.thehighroad.org/index.p...tudy-of-powder-weight-per-piece.902618/page-3

    The analysis done for that thread showed somewhere around 1 fps per kernel for both Varget in 6 Dasher and H4350 in 6 Creed. Exploring actual velocity vs. powder charge curves (consistent with dozens of replications of the same experiment for the same cartridges), I show the statistical sensitivity of group size EVEN IN THE ANTINODE to be less than 1 click in the scope.

    Here, the red circled portion represents one of the nodes, with the blue circled portion representing an anti-node, theoretically the worst portion from which to pick a charge weight. And even here, where the sensitivity is 4 times greater than the linear average, the penalty is

    8D472D7E-7D41-404E-83A7-25E63F58A0A7.jpeg

     
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  4. fxvr5

    fxvr5 Member

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    So, based on one shooter's result loading 148 gr HBWC in 38 Special.
     
  5. Varminterror

    Varminterror Member

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    At 3.1” coal, you’re loading rifle cartridges. In a rifle cartridge, you do not need to be concerned with pressure increase when seating deeper into the case.

    3.1” is a weird OAL, maybe a 7 Mauser? Starting there - case capacity for 7 Mauser is 0.238in^3. Seating a 7mm bullet 50 thousandths deeper only changes the capacity by 0.003in^3. So roughly 1.3% change in internal volume. Since the peak pressure happens somewhere around 2” of bullet travel - total entrapped volume somewhere around .4in^3, around 1.5x the original case capacity - we really just don’t see a pressure influence from seating rifle bullets deeper with the same powder charge as long as we don’t enter into compressed loads due to the deeper seating depth.

    Worrying about increasing pressure by tweaking seating depth in rifle cartridges is much ado about nothing.
     
  6. LiveLife

    LiveLife Member

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    OP did ask an "off topic" opinion and I gave my "guess".
    I know, "opinion" based on secondhand information from a "bullseye match shooting" THR member @ljnowell but I have bought brass from him many times (Good brass BTW) and give consideration for winning bullseye league match posts some credence.

    But that was my "guess" and now I have some AA No 2 on hand, will start doing load development and comparison range tests, hopefully out of welded/hard mounted machine rest to bolt to my welded 5'x8' landscape trailer on tri-pod set up (Around 1000 lbs finished with shooter) to do 25/50/100 yard pistol/carbine testing (I am thinking about hard mounting the barrel/shroud to mount for carbines and still working out the details for pistol mount).

    So before too long, we should have some group size data with different powders. Stay tuned.

    [​IMG]
     
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  7. BJung

    BJung Member

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  8. fxvr5

    fxvr5 Member

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    So A#2 is the most accurate powder for all guns?
     
  9. LiveLife

    LiveLife Member

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    Oh, no. OP just asked for opinion between No 2 and Bullseye for Makarov (I am thinking .380Auto?). I think depending on the caliber, bullet weight and velocity load (Full power vs lighter target loads), different powders can produce greater accuracy compared to other powders on the burn rate chart.
     
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  10. GeoDudeFlorida

    GeoDudeFlorida Member

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    TiteGroup, No.2, Red Dot, and Bullseye are all good for the full range of the Makarov’s operating range with milspec, original springs. Wolff sells lighter and heavier springs if someone wants to change their load. Cheap enough to keep several sets.
     
  11. Howa 9700

    Howa 9700 Member

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    To update this thread, my personal plot thickens.

    As suggested, loaded test rounds at promising nodes 7 and 8 and found no joy. In fact, things got worse.

    But, after first two 3 shot rounds.......where 2"+ groups at 100 yards were centered 1 to 2 inches to the left, adjusted scope to what I thought was 1 MOA to the right. Groups moved 1 to 3 inches to the right, then up, down and all around. Groups shot at target centers with aim points 4 inches apart look like it was hit with a shotgun. Can't tell which bullets went where. Impact points co-mingled. That ain't good. That wasn't on me and wind was mostly calm. Gun has new Timney trigger and has been pillar bedded and barrel free floated. Rem 700 BDL in 6mm Rem. Original barrel with less than 500 rounds down the tube.

    Either gun can't / won't shoot worth beans, or something else going on. After seeing results of scope adjustment, and thinking back to problems like it, beginning to suspect scope is bad. Leopold 3 - 9 X VariX II, but also nearly 50 years old.

    Have a nearly new Nikon 3 x 9 laying around, so will swap that out to see what happens. Stay tuned.

    Does THR have a "bad scope" thread? If not, we might want to start one.
     
  12. South Prairie Jim

    South Prairie Jim Member

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    Bummer’
    We have to have good data to make good decisions, I have not had the problems with scopes that other fellas have but it does seem to happen.
    Please report back when you get a handle on it.
     
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  13. Howa 9700

    Howa 9700 Member

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    Will be very frustrating (but also huge relief) if it turns out to be an optics problem. Accuracy problems been there all along, but well within what could be possible from either ammo or gun. So kept chasing those, assuming optics good.

    First major warning sign was when shooting load ladders. One or two shots of 15 missed target completely. Like 8 inches off to left. Always left. Would then return to base. Ignored that. Should not have.

    But again, still guessing. Hoping swapping optics will help clear this up.
     
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  14. Blue68f100

    Blue68f100 Member

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    Make sure you check your mount too. The last scope I had that went bad was a Nikon, the mfg replaced it. Over the years I've had the most problems with Bushnell, no longer by them. I've since have set my standards higher after splurging for a Nightforce NXS 8-32. It has the clearest optics I've ever used and the extra power allows me to see how much movement I have, and actually see 223 holes at 300 yrds. No spotting scope required.
     
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  15. AJC1

    AJC1 Member

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    Your question was a defined process. It's as simple as two steps removing the finer points. 1 charge weight- choose your favorite path, ocw/ladder/satterly and 2. Seating depth. I use berger but Eric Cortina and others have their way. That's it. After the fact you may want to go back and find the edges of your powder window at the seating depth and load in the middle or favor one side if you developed cold and only expect it to get warmer or the opposite. To reduce confusion I call those two steps load development and other finer points like neck tension tuning but that's just me. Tuning a load can use a pile of components and is a target exercise for most and can spill over to hunting but doesn't need to.
     
  16. Howa 9700

    Howa 9700 Member

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    I'm counting in the Nikon (already mounted) to last long enough to tell me the rifle groups well if the aim is true. If that pans out, will be on to new (or repaired Leopold) glass and back to the beginning on load development.
     
  17. ballman6711

    ballman6711 Member

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    I had a scope go bad years ago. Mounted on the rifle and working on zero. I almost had it and suddenly my shots were all over the place. Several shots and a lot of head scratching, couldn't figure it out.

    And then one more shot and the vertical crosshair went diagonal. :cuss:

    You'll get if figured out. Take your time and work one step at a time. Sounds like a scope issue to me.

    Best of luck with it.

    chris
     
  18. South Prairie Jim

    South Prairie Jim Member

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    One thing we do in long rang load development is the use of sharpie’s on the ogive of each incremental series of rounds to identify them after impact at an increased distance eliminating the need to take the time to record each impact on a separate target at the bench. We also use one point of aim, send all the rounds then connect the colors and follow the stable overlapping load.
     

    Attached Files:

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  19. Howa 9700

    Howa 9700 Member

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    Good, bad or ugly.......here is what I found out.

    Target 1 was shot with original, 45 year old Leopold scope. 3 shots each, only difference in hand loads was each number increased seating depth 0.003. Was looking to see if nodes would show up. After #1, moved scope to impact 1 inch to the right (prior target all were also impacting to the left). After scope adjustment, shots flying everywhere. .Some OK, 5, 6 and 8 were so wild and comingled, couldn't tell who shot what and one round missing entirely. Don't know where it went.

    IMG_0523.jpg


    Target below shot today after swapping to a spare inexpensive Nikon scope, hastily mounted. Bore sighting revealed crosshairs to be 2 feet below bull at 50 yards. Say What? Then remembered son had been trying to shoot it to half a mile on his 308 and had ran out of elevation, so must have left it there when he took it off to replace it with a Vortex.

    Anyway, a few sight in shots, then 3 hasty fired groups at 100 yards. Center group.......4 rounds of 20 year old Remington factory ammo. Then moved bottom left......shot 5 rounds of some hand loads my buddy did a few years back (lot of variation in those) and finally, Then 8 clicks left to center shots above aim point and 1 more round to confirm. Then bottom right, 6 more rounds of Remington factory ammo to clean out the box. First two groups of factory and reloads did not impress me much, but better than average of what I had been doing. Last group, starts to resemble an actual repeating group. Wind was behind me if it matters and was a good breeze blowing stuff around a bit. 100 yards.

    IMG_0524.jpg

    I'm thinking problem lies in scope. Gun will probably shoot well enough to print 1 MOA groups with right loads and optics, so gun may have bought some more time. So either stick with Nikon as is or start shopping for a new scope. Decision time.
     
    Last edited: Nov 17, 2022
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  20. Howa 9700

    Howa 9700 Member

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    For a bit of irony, as I was leaving range, a nice 6 point buck was standing in an opening, about 60 yards away. He moved into some light brush to hide.....but still clearly visible. He just stopped and watched me drive past. Drove around him in a semi-circle......me watching him and him watching me. He never moved. But at that range, rifle shooting good enough to have hit within an inch of aim point. Pretty typical of the type of shots we get. Maybe good enough is.......well......good enough?
     
  21. Blue68f100

    Blue68f100 Member

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    Leopold backs their scopes no matter what age they are. Contact them and send it in for repair. Could be something shook loose and it's repairable, if they will replace it. The last one I sent in the eye piece focus was out of wack, parallax. They made the repair and sent it back in less than 2 weeks. Free of charge.
     
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  22. BJung

    BJung Member

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    I'm looking at the groups Howa shot with varying seating depths. Since consistency is key, would grouping brass by weight or volume a then adjusting neck tension be the next logical step?
     
  23. South Prairie Jim

    South Prairie Jim Member

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    you shouldn’t even do seating tests until the scope is secure, then repeat / confirm/ refine the charge window. The cases should already be of one lot number if accuracy is the goal.
     
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  24. Blue68f100

    Blue68f100 Member

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    Once I have my accurate node, my first tuning knob is OAL. Then I try different primers. I have found some loads like Federal Gold Metal Match primers. These shrunk my group by reduce the SD & ES. Some times the primer I start with is best sometimes not. You just need to test to see what your powder likes.
     
  25. Howa 9700

    Howa 9700 Member

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    To clarify, the seating depth groups were put together and shot with the original Leopold scope. Loads developed downstream of previous load development. If all else was good, only difference to show up on paper would be due to seating depth. But then seeing the large changes in impact after only small changes in scope adjustment, concern immediately shifted to the scope. I freely admit I'm not the best shooter on the planet, but I'm not that bad. So swapped out scope, then shot the second lower target.

    Swapping out to the cheap Nikon scope brought about precise, predictable changes in impact.......what is supposed to happen. Wasn't getting that before. If optics has been bad all along, everything I've done prior has been a waste of time and components. Time to start over.

    Looking at my 2nd set of groups.......two things stand out....at least for me. First is change of scope helped things. Second.....even with change of scope, groups still not very good, but also fired with generic ammo. If following old deer rifle standard of 2 MOA, certainly good enough to plug deer inside 200 yards......but not going to win any shooting matches. 1 MOA was the goal. May, or may not get there. But getting reliable optics first step on road to finding out.
     
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