Measure this and measure that.

Discussion in 'Reloading' started by 4ked Horn, Apr 8, 2005.

  1. 4ked Horn

    4ked Horn Writers Guild

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    A bunch of you guys are measuring bearing surface and base to caliber for boat tails and base to ogive. All of which are length measurements. Are any of you measuring bullet diameter (maybe to +/- .0001") to see if there is a corelation to the length measurements? Would a longer BS corespond to a bullet with a larger diameter? By my thinking it should and if so I might be able to sort bullets based on diameter since I have a micrometer but I don't have a bunch of money for the other fancy gauges. At the very least this measurement should increase or decrease drag on the bore within a given BS length. Yes? No?
     
  2. 3sixbits

    3sixbits Well-Known Member

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    4Ked horn: There is a cheap way to check for varying bullets with the ogive checker sold by Sinclare under the name of Davidson's ogive checker, these attach to your calipers and are a poor mans way of having better control of spotting different lengths. I have seven of them for the various dia. bullets. You might want to look at these as they are about eight bucks a pop.
     

  3. goodgrouper

    goodgrouper Well-Known Member

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    [ QUOTE ]
    Are any of you measuring bullet diameter (maybe to +/- .0001") to see if there is a corelation to the length measurements

    [/ QUOTE ]

    Yes. On a few of those longer ones, there are high sides that make the diameter slightly larger but that has only been the case with the 300 grain .338 MK. All other bullets seem to be better.


    [ QUOTE ]
    At the very least this measurement should increase or decrease drag on the bore within a given BS length. Yes? No?




    [/ QUOTE ]

    Yes it does. On our 2000 yard shooting, bullets that were segregated according to bearing surface length made the standard deviations get reduced by half and the vertical stringing at 2000 yards was reduced more than just trimming meplats alone. In fact, the last time we tested the MOAG at 2k on our hunting trip, NONE of those bullets had been trimmed, but all were segregated by bearing surface. In the grand scheme of things, I would say that bs segregating makes 98% of the vertical stringing disappear, and meplat trimming makes up the remaining 2%!

    One thing I would also like to mention is that most of this extra technical stuff really means nothing if you are just shooting out to 1000 yards or less. Maybe even 1500 yards or less. I never do any of this crap to my other guns, and they shoot great at and up to 1500. Of course, they are using smaller bullets that are easier to make consistent than that big 300 grainer. I have 600 140 grain 6.5mm Berger vld's for "old blue" right now, and they have meplats that are perfectly flat right from Berger, and the bs and ogives on them vary less than .001"!

    In other words, on a .308 that goes subsonic at 900 yards or maybe 1000, and is just being used for varmints and gongs and not comp, I would just forget about all this tech crap. Just load them up with <font color="blue">normal </font> match techniques and go shoot. It is kindof like trying to super tune a toyota camry to run the quarter mile in 11 seconds by just changing the air filter. It ain't gonna do you much good. Better off just getting a tricked out muscle car. /ubbthreads/images/graemlins/wink.gif
     
  4. Brent

    Brent Well-Known Member

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    [ QUOTE ]
    Would a longer BS corespond to a bullet with a larger diameter? By my thinking it should and if so I might be able to sort bullets based on diameter since I have a micrometer but I don't have a bunch of money for the other fancy gauges.

    [/ QUOTE ]

    I'll say that it most likely would not effect bearing surface length, and here's why. To measure BS length a basic tool is used in order to engauge the bullet at a specific diameter on both ends. For a 30 caliber a hole with an ID of .300" is used and will engauge the bullet at approximately the same location on the ogive as the rifling would, the same ID hole is used to slip over the boattail as well. So, the two inserts with these .300" ID holes in them basically tell you how close the "near top" of the boattail is in relation to the "near bottom" of the ogive and thus the approximate bearing length that will be "engraved" by the rifling upon firing.

    If you have the capability to bore the .300" holes (or whatever ID you need) in these inserts you can think of many ways to creatively use a caliper of dial indicator to read the bearing length. You'll just need to keep things lined up and consistant, and remember these measurments are just relative to one another.

    In a nutshell though, the OD of the bullet will not tell you the length that will be engraved. It may tell you by your own experience if a bullet will foul excessively if it is too large or some other thing you attribute to its larger diameter, and possibly help weed out some bad eggs if you do sort this way. One thing to remember though is that most bullets are not uniform in diameter along the bearing length and you'd have to decide where to measure them for comparison, then if they varied (or did not vary) in the other area you did not measure, the question what to do arises.
     
  5. jb1000br

    jb1000br Well-Known Member

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    [ QUOTE ]
    A bunch of you guys are measuring bearing surface and base to caliber for boat tails and base to ogive. All of which are length measurements. Are any of you measuring bullet diameter (maybe to +/- .0001") to see if there is a corelation to the length measurements? Would a longer BS corespond to a bullet with a larger diameter? By my thinking it should and if so I might be able to sort bullets based on diameter since I have a micrometer but I don't have a bunch of money for the other fancy gauges. At the very least this measurement should increase or decrease drag on the bore within a given BS length. Yes? No?

    [/ QUOTE ]


    The manufacturing process really cant let the diameter be off -- unless different dies are used. I have a 50millionths mic, maybe i'll check a few 142's when i get a chance.

    JB
     
  6. Mysticplayer

    Mysticplayer Writers Guild

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    I hope that I am not the only one feeling this way. When I buy 'match' bullets, I want match bullets. Having to dick around and sort and separate and modify and toss is not what I feel deserves the match bullet cost premium.

    I here some shooters complain about the cost of custom bullets. I say, pay it. how much is your time worth? What happens when you have 50% of useable bullets? how much confidence do you have that the last shot to make a winning group doesn't have a wonky bullet and blow the match?

    I think QC from the big match bullet makers should improve. I discussed some new bullets with one main company and they were so excited because it met their 1/2 MOA goal for accuracy. YIKES!!!!!!

    I think Partitions do better...

    Jerry
     
  7. Dave King

    Dave King Well-Known Member

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    I've made several ogive "comparators".

    Last one was from a large metric nut found at a hardware store in those fancy yellow parts cases, drilled a 19/64 (.297) hole through one facet. Deburred and polished it a littel bit and it works like a champ. Looks a lot like the Sinclair comparator but less holes.
     
  8. 4ked Horn

    4ked Horn Writers Guild

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    3six. I have a lot of replying to do so I will simply say I read your post and thank you. 8 bucks is certainly in my price range.
     
  9. 4ked Horn

    4ked Horn Writers Guild

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    GG thanks. I don't do any compeating (sp?) so I had no practical experience to tell me at what distance to start sweating the little stuff. I will just buy wildcats and maybe the tool(s) mentioned by 3six and/or Dave and just check for major flaws.
     
  10. 4ked Horn

    4ked Horn Writers Guild

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    [ QUOTE ]
    I'll say that it most likely would not effect bearing surface length, and here's why. To measure BS length a basic tool is used in order to engauge the bullet at a specific diameter on both ends.

    [/ QUOTE ]

    This is exactly why I thought the larger or smaller dia would change the BS measurement. If you increased the diameter by .001" the ID of the tools would rest farther apart. If the ogive is tangent to the BS that one thou dia change would be maybe a 10 thou (or more) length increase on the BS.

    [ QUOTE ]
    One thing to remember though is that most bullets are not uniform in diameter along the bearing length and you'd have to decide where to measure them for comparison, then if they varied (or did not vary) in the other area you did not measure, the question what to do arises.

    [/ QUOTE ]

    Good point. I don't shoot enough to wait until I have enough with similar measurements in too many variable areas.
     
  11. 4ked Horn

    4ked Horn Writers Guild

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    [ QUOTE ]
    The manufacturing process really cant let the diameter be off -- unless different dies are used. I have a 50millionths mic, maybe i'll check a few 142's when i get a chance.


    [/ QUOTE ]

    I would assume that every variable is variable. It may be a closer tolerance than the other possibilities but the first rule of machining is that NOTHING is exact.

    Let me know what you find out. I will be interested to know If you would try measuring the dia just ablve the boat tail and also near the base of the ogive. The middle of the BS would be less significant (but not totaly insignificant).
     
  12. 4ked Horn

    4ked Horn Writers Guild

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    [ QUOTE ]
    I hope that I am not the only one feeling this way. When I buy 'match' bullets, I want match bullets. Having to dick around and sort and separate and modify and toss is not what I feel deserves the match bullet cost premium.

    [/ QUOTE ]

    I agree. It should be a simple and automated process for someone like Sierra to sort bullets coming off the line for BS and then to sell them accordingly boxed. It shouldnt matter to the shooter what the precise bearing length is as long as they are all the same in the same box. We, after all, don't care which lot of powder we have as long as the loads come out of the same lot. If we have many rounds to load we buy bigger lots.
     
  13. 4ked Horn

    4ked Horn Writers Guild

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    Dave. I am fairly well versed in drilling holes so that idea is right up my alley. I like simple fixes to simple problems. Thanks.
     
  14. brian b

    brian b Well-Known Member

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    4ked Horn,
    after reading your initial post I measured 100 sierra 300gr MK's (338 of course) 25 from 4 different segregated bearing surface lenghts and every one measured exactly the same .3380 . the ones with the hi side GG was telling you about were still .3380 but one side had a slightly longer bearing surface than the other side not a larger diameter. One point I will totally agree with GG on is that it is a waste of time doing bullet bearing surface comparing on a 1000 yard gun ,but on an Ultra Long Range gun bearing surface length makes a huge difference on your vertical stringing period. as far as meplat uniforming I cant really say that I am totally sold on this ,but with that said I do believe that sorting meplat length is beneficial and the ones that are a little too long in the meplat can be trimmed slightly to conform with the rest. (on a test me and GG did I trimmed the meplats on some 300grMK's so that they were perfectly square, at 2000yds they landed 20 feet lower than the untrimmed meplats although much more uniform meplat trimming can be seriously overdone and changes B.C. more than I ever thought) if you are just shooting to 1000 dont do this either but if you are trying to shoot a Chuck at 2300yds do anything you can.
    B