Finding Max OAL for specific bullets

Discussion in 'Reloading' started by Skubasteve, Oct 1, 2013.

  1. Skubasteve

    Skubasteve New Member

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    This is my first post, I've been gathering very useful information as I started reloading and begun to shoot long range, so thanks for helping me not blow myself up!


    Anyways back to the post, so I've been trying to find the best way to measure OAL for each bullet and haven't found anything really consistent till I started playing with my caliper. I know I'm not the first but let me know it this is an accurate way of measuring out to the lands. Ill be using a Nosler 165gr BT chambered in .308 as an example:

    - Remove bolt, Drop a bullet down the barrel (wiggle it around) then measure from a set point on the bolt entry to the bullet (needs 6"+ caliper)- 6.606"

    - Drop a fired casing in and measure from the same point to the rear of the case- 4.822" (this number will not change between bullets)

    - so now subtract these two numbers (1.784") then add in the length of the bullet (1.215") which gives you a final result of 2.999 for max OAL

    I've tried the marker,smoke, and loose bullet techniques but this is the only way I got the same number everytime. Let me know if this method seems accurate. And also where should I start my load length at? I always hear " back off a little" but could use some actual numbers, thanks



    Measurements done on Remington 700 ADL .308 SA 26" barrel
     
  2. el matador

    el matador Well-Known Member

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    The method you describe should work just fine. Seems like a lot of work, but reloading is just that! I use the RCBS Precision Mic for measuring jump to the lands. It has a dummy cartridge that you chamber and the dummy bullet is pushed back as it contacts the lands. You then remove the cartridge and place it in a device that measures from the cartridge base to the point on the ogive where it hits the lands (it does not measure from the bullet tip). You then make a note of the measurement and seat your bullets down until they give the same reading on the device. It's simple, quick and you can double check whenever you feel like it. The kit also comes with a tool for measuring case length from base to shoulder, which is very useful when body sizing or full length sizing to get just the right amount of shoulder bump.

    There is no magic number for how far off the lands to seat. Anywhere from .120 off to .010 into the lands may work. Just be aware that pressure could go up significantly as you get really close to the lands, so definitely use starting loads and work up. Try a few maybe .010 off, .050 off, and .090 off and see how they perform.
     

  3. Skubasteve

    Skubasteve New Member

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    Thanks for the reply, ill be picking one of those up soon. But curious if this was an effective way for guys first starting to reload, $30-40 doesn't seem like much But after you buy bullets,powder, reloading equipment , etc etc. it starts hitting the pocket book hard
     
  4. Scot E

    Scot E Well-Known Member

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    Most of the other ways to do it involves measuring from base to bullet tip, which isn't the way you want to do it if you want to get the tightest groups. Measuring from base to ogive gives you the same amount of jump to the lands as it measures off the bearing surface.

    Scot E.
     
  5. yobuck

    yobuck Well-Known Member

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    back in the old days we just took an empty unprimed case and partialy seated
    the bullet. then put it in the gun and closed the bolt causing the bullet to be fully seated. then by turning the stem on the die you can get the exact seating
    depth desired. using a sharpie or smoke from a match will tell you when no
    land contact is made. when your happy with the seating depth keep the sample for future reference. that way if you change bullets you can easily reset your die back to that one.
    no tools involved at all.
     
  6. Bodywerks

    Bodywerks Well-Known Member

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    Hmm. I just close the bolt, run my cleaning rod down the barrel until it hits the bolt face, and mark the rod, in relation to the end of the muzzle, with a piece of tape. Then I remove the bolt and put a bullet into the lands and hold it in place while doing the same with the cleaning rod. The measurement between the two pieces of tape is the oal for that particular bullet. Of course, we're more concerned with ogive length, so measure the total length of that bullet and measure the length of the base of the bullet to give and subtract that value from the bullet length. Take that value and subtract it from your oal. This is your ogive length to the lands, and it is the same value regardless of the bullet you use
    t
     
  7. Mike 338

    Mike 338 Well-Known Member

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    I use the Hornady OAL gauge. It takes longer to get the tool from the drawer than do the actual measuring. Fast and as accurate as anything.
     
  8. Skubasteve

    Skubasteve New Member

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    I understand that the ogive is what matters, weather I measure from the ogive or the tip I still maintain the same result per bullet( with tips intact and consistent ) I just feel more confident measuring from the tip. Where are you guys starting your loads at? My accuracy hunting load is already determined but I bought some 208's and 125's to play with, nosler measures 2.999 to lands and is accuracy tested @ 2.775. Should I use this same distance? .224 from contact?

    And after measuring a few times it was within .010 even pushing on the bullet a bit. It really doesn't take long after you measure the first one
     
  9. Scot E

    Scot E Well-Known Member

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    That is the issue though, the tips and overall lengths aren't consistent. So if you measure from the tip your bearing surface will be off and accuracy will suffer. Only you can determine if the result you get doing it less accurately is sufficient.

    Scot E.
     
  10. g0rd0

    g0rd0 Well-Known Member

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    every time I open a new box or bag of bullets I use a fl sized case with no primer or powder lube inside the neck place a bullet from the new pack in the neck and chamber it. It has seated the dummy to the lands measure this and write it down ,now place the dummy on your press and with the seater die (with the seating depth plunger all the way up) raise the dummy up in the die and screw down the plunger to the bullet, now screw it down just a little and remeasure. I like .010" shorter.
    When I have loaded all 99 from the pack I pull the dummy and load it also.
    For each pack I do this unless the new pack has the same sku number as the old pack.
     
  11. Mikecr

    Mikecr Well-Known Member

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    The cleaning rod method is sound. Better is the R-P tool, which further refines the cleaning rod method.

    Measuring to the tip is not a problem, because it's representative of THAT bullet, for COAL of your master. After measure you load the master to matching COAL with THAT bullet, and then measure it's OgvOAL with a comparator that you always use.
    Log this value.
    With this, you can reproduce seating w/resp to the logged value.

    This number doesn't represent a truth, but your load development results do.
    And all that matters is that you can reproduce THAT truth.
    When you change bullet types, do it all again.. Find the new truth

    You know, the only reason to measure Max OgvOAL is to know in load development when you're contacting lands & causing a step change in pressure. Other than that, it's really of no value.
     
  12. Skubasteve

    Skubasteve New Member

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    I've tried most of the methods listed above and this was the only consistent "foolproof" way I found for myself. I understand that each bullet tip may vary, that's why I took out 5 bullets out to check my measurements were accurate, and to get the ogive all you would have to do is measure the ogive and input it in the little equation. What are you guys starting your new loads at? Does the seating need to change with different bullet weights?
     
  13. Bodywerks

    Bodywerks Well-Known Member

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    Measuring to the tip is the least accurate way to load precision rounds. But if you take that one bullet that you used to measure your oal to set up your seating die(assuming your seater is the competition ogive type) then you'll be fine. But you have to understand that, discounting any account for throat erosion, your oal to the lands of your rifling will be the same for any bullet, be it a long nose vld bullet or a soft point hunting bullet. This is why precision reloaders choose to measure to the ogive, which is the part of the bullet that contacts the lands of your rifling.
    To answer your question. Seating depth is important and different for each type of bullet. Some like to be jammed into the lands and some like a little jump. It is important to measure ogive length of a loaded round to ensure the jump distance is consistent. This is good for the bullet but also ensures that the pressure spike occurs at the same point as the powder burns. If you were measuring oal from the tip of the bullet then the jump would be inconsistent, meaning the pressure spike would be inconsistent, causing velocity to be inconsistent, causing accuracy to suffer.
    Consistency of pressure is key. It is the reason that neck tension consistency is so important also, along with case capacity, charge weight, etc.