Measuring lands help needed

Discussion in 'Reloading' started by Elkslayer1, Jul 27, 2010.

  1. Elkslayer1

    Elkslayer1 Well-Known Member

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    I have a new 7mm Rem Mag ( Vanguard sub-moa ) and need some help measuring to the lands. Do you guys use the wooden dowel method? Split case method? Or do i just keep adjusting the 168 berger until I start to see rifling marks on the ogive? Please help. Does anyone have any pictures of your bullet touching the lands?
     

  2. 406pat

    406pat Well-Known Member

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    I use a hack saw or dremel wheel to make 4 cuts down the case neck to just above the shoulder junction. I file the cuts smooth inside and out then lube and size it just to make sure it doesn't bind up. You should be able to slide a bullet into the neck so it rests in there. Next, I cover the bullet with sharpie, rest it in the case and chamber it. If the bolt won't close (shouldn't take more force than normal for chambering a round), I take the case out and cut a little deeper in the neck toward the shoulder, file and size and try again.

    If you get a bullet stuck in the lands, a couple sharp raps of the butt on the floor should jar it loose.

    Once the case is where it needs to be, I mark up the bullet with sharpie, chamber and carefully extract. If it works right, you should be able to see rifling marks on the ogive of the bullet. There will also be marks on the flat of the bullet from the case. If you can see these when the case is extracted, the bullet has shifted during extraction and the process needs to be repeated.

    I do 5 or 6 measurements just to verify that I've done it right.

    Good luck!
     

  3. nfhjr62

    nfhjr62 Well-Known Member

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    OR use one of the many tools sold for doing this measurement too many to list
     
  4. coyotezapper

    coyotezapper Well-Known Member

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    Last edited: Jul 27, 2010
  5. Chas1

    Chas1 Well-Known Member

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    406pat, good tip, thanks for sharing.
     
    Last edited: Aug 3, 2010
  6. cbans

    cbans Member

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    I take one of my fired cases and seat the bullet longer than I know will be acceptable then I chamber it slowly. The bullet slides back under the pressure. My fired cases have enough neck tension to hold a bullet tight enough to do this. If they didn't, I would slightly neck size the case. I usually pull the bullet after I measure it and do this a good three times or so to make sure I have a good max OAL. This only works for the specific bullet that I have seated (do not measure one and then try to load another). It may not be the best way but, it has worked really well for me and I don't have to buy anything.
     
  7. SBruce

    SBruce Well-Known Member

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    There are a few tools that you can use to do this, that have been mentioned.

    I don't think anyone has mentioned the RCBS Precision Mic.

    They make it in alot of standard factory chamberings. I've used them for alot of years on the guns that have factory chambers. Wildcats require one of the other tools mentioned here.....I use the Sinclair for those guns.

    One big plus for the Precision Mic is that it's a three purpose tool. It can also be used to measure headspace and set up your FL sizing die to only size a minimal amount of the brass (minimized run out, work hardening and case head separation).

    I highly recommend them for factory chambered rifles.
     
  8. RT2506

    RT2506 Well-Known Member

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    I use the one cut on the neck from mouth to start of shoulder cut case. Insert a bullet with my fingers place case into the chamber and close the bolt. Extract and measure from ogive to base of case. This is the too the lands measurement.
     
  9. BobbyL

    BobbyL Well-Known Member

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    I have never found those tools to be accurate enough for what i do but they do help alot. I always size a fired un primed case and load a bullet long then chamber it. Then use steel wool to scuff up the bullet so i can see what kind of marks it makes after chambering it and continue to seat it deeper untill the marks almost go away. One thing that helps alot for me is taking the ejector and firing pin out so i can get a good feel for it. Then i label that round and keep it for future reference to see how much the throat has moved. Its also a habit of mine to check to see how well centered the bullet is in the chamber, or how well the chamber is centered....
     
  10. GCF

    GCF Member

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    I personally like the method described in Post #18 of this thread:
    http://www.longrangehunting.com/forums/f28/measuring-bullet-seating-off-lands-56811/index3.html

    As mentioned, simplistic, but seems to work - w/ a minimum amount of drama. The top of the case neck forms a very clean - & repeatable shoulder in the teflon tape.

    If someone has the actual precision equipment (I don't) to run a side by side test against this method, I'd be very interested in seeing the results.

    Gary
     
  11. SBruce

    SBruce Well-Known Member

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    One important thing to remember:

    Best or most accurate seating depth is different for every rifle/bullet combo.

    The method of measuring the lands is not nearly as important as getting a benchmark and varying the seating depths enough to find the best (most accurate) one................All methods work, but once we have a number to base off of, the seating depths should be varied in test loads. We will then shoot groups with those batches of varied depths and find out which is most accurate (Base to Ogive) with that particular rifle/bullet. Some sort of comparator will be used from that point on to set up the loaded round to the best Base to Ogive length.

    The RCBS Precision Mic is used to measure the Boltface to Lands, and then used to measure Base to Ogive. It is a very simple tool to use, not expensive and plenty capable of measuring your loaded rounds to .001 or less to ensure they are at the optimum depth. It can also be used later (as the throat wears) to measure how much barrel erosion has occured. If the throat has wore .010", then the Seating depth would be extended by .010" ect.

    Once again, everything is relative in this process. Most important thing is to find your most accurate seating depth and duplicate it for future loadings. As long as you stick with the same tool or method, the results can be repeated at any time.