ES/SD - Better or worse when seated into lands?

Discussion in 'Reloading Forum (All Calibers)' started by MikeMcCasland, Oct 11, 2018 at 10:32 PM.

  1. MikeMcCasland

    MikeMcCasland Silver $$ Contributor

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    Gents,

    Reloading theory question for you...

    Assuming your case/powder/primer/bullet/charge weight/neck tension all stay the same, would you expect to find more consistent ES/SD wtih the bullet loaded into the lands?

    I'm in the process of trying to test this myself, but don't have enough data points to draw a firm conclusion. I also question if it's possible to come to a statistically valid conclusion with a human driving the rifle (i.e. rifle hold can affect ES/SD).

    That said, there are some extremely smart folks on this forum; many of whom have done extensive testing, so figured I'd toss a line out to see who bites.

    It's my hypothesis that ES/SD numbers would be reduced (to what extent I don't know). Just my SWAG. ;)
     
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  2. dkhunt14

    dkhunt14

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    If you shoot free recoil it is not effected by human interference. I shoot an 85 pound heavygun and free recoil. Touch nothing but trigger and that is only 2 ounces. I believe the human factor is taken out. I also shoot everything in the lands. In all my testing
    It was more accurate at 1000. I don't worry about ES. I have some guns where the ES was 2 or 3 and it shot bugholes at 100. When shot at 1000, it would shoot all vertical and 13 to 16 inches of it. The same gun with other loads of 10 or more ES would shoot 10 shot 4 inch groups at 1000. The tune of the barrel comes into play. Matt
     
  3. Dusty Stevens

    Dusty Stevens COVFEFE Gold $$ Contributor

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    The only data points that matter are the holes in the target.
     
  4. WillyTP

    WillyTP FBBW Gold $$ Contributor

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    Amen
     
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  5. F Class John

    F Class John Gold $$ Contributor

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    The type of bullet plays a part in that too. Some are more consistent off lands and some are better jammed. For instance I’ll get much better ES (I don’t care about SD) jamming a VLD while a hybrid will SD better when jumped. At least that’s what I’ve found.
     
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  6. NorCalMikie

    NorCalMikie Gold $$ Contributor

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    ES/SD?? All I know from experience is: I can take my 6 BR, load it up a little on the hot side with a jump to the lands and start seeing pressure signs.:eek:
    That same load of powder, bullet and primer with the bullet "jammed" .010 INTO the lands will show NO pressure signs AND, I can go even higher on the powder charge with no issues. Don't know why but it works for me. SO, all my loads are built with the bullets "jammed" .010 into the lands. AND, I have pulled bullets on a loaded round and dumped powder into the action. I knew what to expect and was ready when it happened.;)
     
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  7. damoncali

    damoncali Gold $$ Contributor

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    At the end of the day, I suspect it doesn't matter. The accuracy you give up going with a sub optimal seating depth will probably trump any gains in velocity consistency, if they even exist.
     
  8. dkhunt14

    dkhunt14

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    Every gun i ever had shot better in the lands. They shot their smallest groups testing and won me alot of competitions. Now we only shoot 10 shot groups at 1000 and groups always take preference over score. Matt
     
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  9. ricco1949

    ricco1949 Gold $$ Contributor

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    The most memorable thing I gleaned out of "Secrets of the Houston Warehouse" is that not a single rifle would agg in the .000's unless bullets were seated in the lands.

    Correction: The reference to "in the lands" only related to Virgil's rifle as noted below. No mention is made of any other rifles in this regard.

    One thing that IS important is that the bullet be precisely seated against the lands. T.J. Jackson reported this fact in the May 1987 issue of Precision Shooting. In a letter to the Editor, T.J. wrote, “...in all our testing in that Houston warehouse... and the dozens and dozens of groups that Virgil King shot in there ‘in the zeroes’... he NEVER fired a single official screamer group when he was ‘jumping’ bullets. All his best groups were always seated into the lands, or at the very least... touching the lands.”


    Rick
     
    Last edited: Oct 13, 2018 at 5:23 PM
  10. Alex Wheeler

    Alex Wheeler Gold $$ Contributor

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    Over the last couple years I have tuned up a large variety of rifles. What a ppc or br acts like is so different than your average hunting type cartridge that its almost a totally different subject. You almost cant make a br shoot bad enough ES to really hurt your groups. So context matters here. I dont find that seating bullet in or off the lands will make enough difference in ES to be a driving factor in group size. I rarely find that the smallest group is the best ES anyhow. Can you shoot 2" groups at 1k with 20fps ES? Yes you can. I have been messing with a big 338 lately and it has shot a few 3-4" groups at 25 fps ES. If your 20 or better, that not whats holding you back.
     
    Last edited: Oct 12, 2018 at 3:48 PM
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  11. chkunz

    chkunz Gold $$ Contributor

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    Mike,
    Several years ago I bought some good bench rest equipment and spent considerable time learning how to use the equipment and developing bench rest procedure so I could answer a lot of my questions like yours. I bought a chronograph so I could get velocity data when needed. I did a study of statistical analysis to help me decide how many shots per group and how many groups I needed to shoot to have confidence in my conclusions. I did a study on the various methods for analyzing groups in addition to extreme spread. My experience with data analysis in another life has been helpful in analyzing the data from this type of testing. The answer to many questions are unique to your gun and ammo and may be different from what others may report. Your get a lot of opinions and "a friend of my buddy" answers from folks that are really trying to help but may be different from what you find with your equipment if you do the testing yourself.

    I can now answer many questions that I think are worth the effort and I have confidence in my data. This is something that you and others may want to consider. It takes a lot of time and money to develop this capability but I recommend that any serious competitor or shooter develop this capability.

    Best wishes,
    Clyde
     
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  12. Dusty Stevens

    Dusty Stevens COVFEFE Gold $$ Contributor

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    Only one guy could agg in the zeros and he could only do that when nobody else was around.
     
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  13. ckaberna

    ckaberna Gold $$ Contributor

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    Excessive pressure may be due to reduced case capacity when you are “jumping”. Caused by pushing bullet further into the case.?? I dont know if .020” or .030” would make any difference but if that’s all your changing, you have to wonder.
     
  14. rwj

    rwj Silver $$ Contributor

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    Gee... I wonder why:rolleyes:
     
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  15. Ned Ludd

    Ned Ludd Silver $$ Contributor

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    The additional people's excessive breathing must have disturbed the otherwise perfectly still air and wrecked his groups. ;)
     
  16. johara1

    johara1

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    ES. has nothing to do with weather it seated in or out, it has to do with tune if you get the velocity tuned and the bullet leaves the barrel at the same point every time it will shoot small anywhere. Ones preference for a bullet changes the picture as does chamber dimensions, most important is if it repeats.... what the groups looks like ......Barrel quality means so much at long range, without it you will be average..... jim
     
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  17. NorCalMikie

    NorCalMikie Gold $$ Contributor

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    While folks are chasing ES and SD, I've already burned off 200 rounds of bug holes.;):D
     
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  18. ricco1949

    ricco1949 Gold $$ Contributor

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    Dusty, in the BR Central sticky thread "Secrets of the Houston Warehouse", Dave Scott states the following from his interview with Virgil King, the builder of the warehouse:

    1. "Circulating around at that time were mutterings that the warehouse conditions were flawed and the shooting there invalid. From what I knew about the warehouse, I wondered how anyone could fault it. After all, some of the shooters were firing numerous consecutive groups measuring “in the zeros”. Flawed conditions, indeed!"
    2. "That’s not to say that the bulk of rifles showing up there — even the reworked ones — would shoot in the zeros. Virgil estimated he could count on his fingers the rifles he had seen that would consistently shoot to this awesome accuracy level. T.J. Jackson owned two such rifles, both chambered by him for 6BR. One of his rifles, a Heavy Varmint class gun, consistently shot .050". The other, a lighter rifle, would hold at about .060". T.J. also built an exceptional 6PPC for a customer, which T.J. later purchased. Why? We can assume part of the reason is that it grouped at the .050" level. Frank Wilson had two rifles that would shoot in the zeros, but only after they had been reworked."
    3. "In the warehouse, not even the best competitive shooters in benchrest approached what Virgil was routinely able to do. His long, consecutive strings of zero-level groups, fired over a period of years and witnessed by other shooters, stand alone."
    However my original post was incorrect as the reference to "in the lands" only related to Virgil's rifle as noted below. No mention is made of any other rifles in this regard.

    One thing that IS important is that the bullet be precisely seated against the lands. T.J. Jackson reported this fact in the May 1987 issue of Precision Shooting. In a letter to the Editor, T.J. wrote, “...in all our testing in that Houston warehouse... and the dozens and dozens of groups that Virgil King shot in there ‘in the zeroes’... he NEVER fired a single official screamer group when he was ‘jumping’ bullets. All his best groups were always seated into the lands, or at the very least... touching the lands.”

    I took all of Dave Scott's interview with Virgil to be factual.

    Rick
     
  19. Laurie

    Laurie

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    Amen to that!

    I did a classic varied-jump series a few weeks ago with the newish 183gn SMK in my 284 (1:8 gain-twist 30-inch Bartlein; load: Lapua, Murom KVB-7, 53.8gn Viht N165.)

    I usually shoot 180gn SMKs set around 15-20 thou' 'in' or 175gn SMKs jumped in this rifle, same brass, primer and powder, but wanted to see how the very long 183 'uber-VLD' worked out as I have the barrel twist to allow its use. So I'd previously had a go with varying charges and the bullet well 'in'. ES values were fantastic, all single figures for 4-round batches, one charge weight with an ES of 1fps - ie three shots with identical MV and one only 1 fps different. (With some of the chronographs I've owned over the years, I'd have discounted these ranges as a chronograph accuracy error, but this was from a Labradar.)

    Groups though were not as satisfactory. All had at least a trace of vertical, the worst a four shot vertical string. So the 183s went back on the shelf and relegated to another 'go' when time and inclination allowed. Then I started to see AS Forum threads saying they like to be jumped, super-VLD long nose shape or not (Litz measured Rt/R ratio value of 0.37, one of the lowest values = most aggressive secant ogives listed in his latest book on bullet shapes and performance, The Performance of Rifle Bullets 3rd edition.)

    So, taking the charge weight giving the least amount of vertical in the previous series, I loaded 3 shots at the original 'in' COAL simply to foul the barrel and provide a baseline MV, then 5 rounds each at: barely touching, 10 out, 20 out, 40 out

    MV for the first three 'in' was 2,738 and I didn't bother about ES, then:

    just touching: 2,741 Av / 17 ES
    10 out: ......... 2,740 Av / ES 9
    20 out: ......... 2,738 Av / ES 11
    40 out: ......... 2,728 Av / ES 12

    So, until the final 40 thou' jump, remarkably consistent MVs and no real range of ES values although no 1 fps result now! The slight drop for a large jump confirmed the previous studies I've seen on this, principally one by Lapua or Viht many years ago with a 7.62 NATO military loading showing seating the bullet successively deeper in steps produced neither pressure nor velocity change until a certain point was reached where the jump was such that the bullet gets 'a run at the lands' and both readings fell. (This of course is the opposite of what many believe to be the case.)

    (As to groups, the 40 thou' jump did the trick and I now need to see how the combination performs at long range in a match. Using it in a 600 yard BR match produced promising results, but the weather was such that it wasn't a good day to learn a great deal - or shoot small groups. However, as Alex says under 20 fps and that's good enough as long as the groups are OK)

    Two other things worth mentioning. The 100 yard groups not only saw no or little MV change but barring the 'just touching' setting which produced a 0.9-inch C to C vertical string, every other group centre was in a near horizontal line. Finally, the BR match used Shot Marker electronic targets that also measure retained velocity and they produced SDs that would pretty well match those with 10-20 fps ES values at the muzzle, so one of the four strings aside, it seems spreads didn't grow by much over 600 yards with this bullet at ~2,730 fps MV.

    BUT ... this is one make / model of bullet in one load combination from my Barnard P action and Bartlein barrel. As chkunz says, it just cannot be extrapolated to other bullets, barrels or loads.
     
  20. rwj

    rwj Silver $$ Contributor

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    Objective evidence would go a long way towards verifying the claims...
     

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