How do I find the lands?

Discussion in 'Reloading' started by jeffwhip, Aug 17, 2011.

  1. jeffwhip

    jeffwhip Well-Known Member

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    I am getting ready to sight in my 280 AI and was wondering how I can find out EXACTLY when the bullet touches the lands?
     

  2. brubo

    brubo Member

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    Find a rod just slightly smaller than your barrel ( not steel) aluminum or brass.
    Make sure rod is long enough to reach chamber. You will also need a wooden dowel 18" long. Drop bullet in chamber so it goes to lands, slide rod into muzzle of barrel so it contacts tip of bullet, with a fine point marker mark rod right at muzzle. Remove bullet insert bolt & close, with rod against bolt face make another mark on rod at the muzzle, measure between these 2 marks that should put you close. Oh the dowel is to hold the bullet in the lands.
    Brubo
     

  3. 80Maro

    80Maro Well-Known Member

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    What I do is cut a slit in the neck of a empty case and insert a bullet so it's seated extra long. Thrn chamber the round and close the bolt. Carefully extract the case, making sure the bullet dosen't drag along the side of the chamber. Measure the case afterwards. Do this at least 10 times to get an average. You will start to see consistant numbers, disregard numbers that are way out to lunch, either the bullet was pulled out some when extracting it or what not. Works for me. I don't know if this is accurate enough for you, just throwing it out there. Do this for each bullet type you intend to shoot to find the distance to the lands for each type.
     
  4. BountyHunter

    BountyHunter Writers Guild

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    this works but two significant issues here the way it was explained.

    1. this method does not measure where it touches. it measures the "jam" into the lands which is about .-040-.050 into the lands. does not it is a bad technique, you just need to remember where you are actually starting from, which is way into the lands.

    2. You need a comparator to measure the ogive of the loaded bullet, and not the cartridge OAL. That can vary as much as .017 between bullets in the same box depending on that particular lot.

    there are several technical articles on the reloading part of sinclair internationals website, giving very detailed instructions using several tools that they sell that work quite well.

    BH
     
  5. Mikecr

    Mikecr Well-Known Member

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    I use an R-P Tool as described well here by Woods:
    Reloader's Nest Forum - OAL

    It's a cleaning rod approach brubo is describing, and has a flat end for the rod + stops.
    This allows me to find actual 'touching' -vs- some amount of jam.
     
  6. djtjr

    djtjr Well-Known Member

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    Have tried it all get the Sinclair tool formthis and with some practice you will get an avg of.002 differences bw measurements. To me it's definitely the most accurate but always take an avg and discard outliers as mentioned above
     
  7. jeffwhip

    jeffwhip Well-Known Member

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    Thanks for the info!
     
  8. Mikecr

    Mikecr Well-Known Member

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    I didn't like the Sinclair tool, or the Hornady/Stoney point approach for similar reasons.
    The Sinclair tool takes measure from a loose collar/dummy bolt that will not set flush in actions(due to their extractrion ramp). They also seemed to miss the concept that a bolt handle is not what holds a bolt in place.
    Both tools leave you averaging because they don't actually represent the boltface, but the back of a case w/resp to it's shoulder stopping in the chamber. We already have bullet nose angles to mess with things, and we don't do better adding shoulder angles as well.
    If 5 people used these tools with 5 different guns, they would not produce consistent results.

    A rod from the muzzle gives you bullet tip to actual boltface. It doesn't have to be averaged.
    With this, you seat THAT bullet in any case until the COAL matches your measurement. Then you find it's OgvOAL with a suitable tool of your choice (just always use that tool). LOG IT

    No matter the method, on firing, the ogive will hold w/resp to shoulder seating (especially if loaded off the lands). So it's another reason headspace should be carefully controlled.
     
  9. brubo

    brubo Member

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    Mikecr I also have the r-p tool. I got mine from the maker ( ragn cagn) Spelling? On predator masters forum. I like the tool.
    What is the tool called that measures from the ogive.
    Thanks Brubo
     
  10. Mikecr

    Mikecr Well-Known Member

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    I'm content with use of a Sinclair 'nut'.
    Sinclair Hex Style Bullet Comparators - Sinclair Intl

    I wouldn't even know where to buy an R-P Tool today..
    I'd go to a hardware store & get aluminum rod stock and a couple bushings for it. then I'd install set screws in em.
     
  11. brubo

    brubo Member

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    Thanks alot for the link Mike. Brubo
     
  12. jeffwhip

    jeffwhip Well-Known Member

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    Ok guys, here is what I did. I bought the Hornady Lock-N-Load Straight O.A.L. Gauge from Bruno's Shooter Supply in Phoenix. I also bought a 280 Remington case with a 30 deg shoulder because I figured it would work for my 280 AI as long as I turned the neck. Next, I turned the neck to .0125 so it would fit into my tight neck chamber 280 AI (.311).

    After several measurements, I was consistently measuring 3.375". Next, I seated the same bullet to 3.507" on two different cases and then slowly chambered the round. When I felt the resistance, I slowly forced the bolt closed. Next I opened the bolt and extracted the round. I did this on two different rounds and then measured the length. The first one measured 3.402" and the second one measured 3.407".

    After reading the comments on my post, it appears that when I chamber a round jammed into the lands, it is .032" & .027" longer than my measurement. So, my question is which reading should I use as my starting point? After talking to a buddy here who has the exact same gun & barrel made from the same reamer, he is running his .020" off the lands. Thanks again for your responses.
     
  13. woods

    woods Well-Known Member

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  14. 80Maro

    80Maro Well-Known Member

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    One thing to be careful of is when your measuring the case, make sure there is no primer seated in it spent or new. Or if there is a primer make sure it is not interfering with the measurements by sticking out too far.