bullet seating depth

Discussion in 'Reloading' started by jimbothepunk, Jun 4, 2010.

  1. jimbothepunk

    jimbothepunk Well-Known Member

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    so i see alot ppl talking bout seating the bullet .x" away frm the lands. how do you go about getting that number and measuring it against the round


    thanks

    lucas


    -------------------------------------------
    what ya going to shoot with that? ya no those deer that are just to far for you well there not for me
     
  2. woods

    woods Well-Known Member

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    Hey jimbo

    There are several methods, some require you purchase a tool and some you can use what you have on hand. Briefly

    Hornady Lock-N-Load Overall Length Gage Bolt Action - MidwayUSA (you will need a modified case also in your caliber)

    SINCLAIR INTERNATIONAL : Sinclair Seating Depth Gauge - (does not work in all rifles and harder to do)

    Cleaning rod method - file a cleaning jag tip smooth, put it on the cleaning rod and insert down the muzzle to the bolt face. Mark it with a piece of tape at the muzzle. Remove the bolt and insert a bullet down to the lands and hold it there with a pencil or wooden dowel. Insert the rod down to the bullet tip and again mark the muzzle on another piece of tape. Measure between the marks.

    Split case or bent case neck method - Either split a case with a dremel tool or squash it a little so that it will hold a bullet fairly firm but the bullet can move. Insert a bullet and chamber it and the chamber will seat the bullet into the neck. Carefully remove it and measure. You have to be carefull that the lands do not grab the bullet and pull it partway back out. Do it several times and you can even blacken the bullet so you can see where the neck scrapes if the bullet is being pulled partially back out.



    Main thing is not to try to get too close to the lands because there are a lot of variables: bullet ogives different, modified case headspace, seating dies, press linkage compressions, bullet grip variances, etc. etc. etc. So stay .025" off + and you will be fine. IMO .025" off the lands is preferable to the .250" off the lands which is what many manual OAL recommendations will give you.

    That should get you started.

    The method I use is an R-P tool that I bought 4 or 5 years ago for $25.00. You can e-mail the entrepreneur who sells them at r_reeves61@bellsouth.net. His name is Randy and he works offshore in Louisiana so he is probably very busy or not working at all because of the oil spill, but he is a great guy and will send you one and you can send him the money if you like it. I paid for mine cause it is the best $25.00 I ever spent.

    It is a stainless rod with 2 lockable collets and it works like the cleaning rod method described above except it gives you much more accurate measurements
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    I guess it wasn't so brief afterall!
     

  3. jimbothepunk

    jimbothepunk Well-Known Member

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    awesome might drap the laptop dwn tothe garage and gohave a play
     
  4. boomtube

    boomtube Well-Known Member

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    "so i see alot ppl talking bout seating the bullet .x" away frm the lands."

    Jim, first, Woods give you excellant info in how to find MAX length when seating to the lands. After that, all bets are off.

    Anyone telling someone else how far off the lands they should be seating will likely lie about other stuff too.
     
  5. BountyHunter

    BountyHunter Writers Guild

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    First off, IF it is a magazine gun you are limited to max COAL that will fit in the mag.

    So no point in even figuring where the lands are!!

    Start at that point and work back to see where the gun likes them.

    Single shots, work with a variety of techniques listed. you can also read on www.sinclairintl.com on their forum (Reloading Press), left hand side of the home page, how and the discussion of the tools they sell and how to use them.

    BH
     
  6. jimbothepunk

    jimbothepunk Well-Known Member

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    i realise that woods cnt tell me to seat my amax x off the lands because every rifle is different but what woods has done is given me a point to where i can seat out to so i dnt make 50 rounds take them to the range and find out there all shit cause there to long

    yes i can only go as lng as the mag but i have been told that the dne thing is to get a single shot non mag fit right then have a back up mag fitted round in the mag if need be.

    lucas
     
  7. zupatun

    zupatun Well-Known Member

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    Just to ressurect this thread a little. I need some help and/or advice.

    I measured some old factory ammo I have lying around and also pushed some bullets I have (165 Interbond, 165g Scirocco's, and 168g SMK's) into a FL resized piece of winchester brass loaded into my MCR Howa 308. After ejecting the chamberd test piece I measured with my calipers using a stony point bullet comparator (measured at ogive) and also for OAL just using the calipers. Here's what I got:

    Round, Comparator Meas. Inches, OAL inches, Note.
    Fed Prem. SGK 165gr, 2.125, 2.686, Factory Round.
    Win SuperX 150gr, 2.178, 2.708, Factory Round.
    Fed Fusion 165, 2.16, 2.718, Factory Round.
    Hornady IB 165, 2.253, no meas, As Loaded into Lands.
    Swift Scirocco 165gr, 2.221, 2.866, As Loaded into Lands.
    SMK 168gr, 2.267, 2.873, As Loaded into Lands.

    the average of the factory round measured at ogive on comparator was 2.154
    Average for factory OAL was 2.704 (most of these are sp hunting rounds)
    I have a couple rounds loaded up for my old Tikka with OAL of 2.802 which was almost max for the tikka Mag...measured at the ogive these are 2.182

    For the IB's in the HOWA I slotted the empty case to seat the bullets by chambering the round and measured OAL and with the comparator. The average on hte comparator was 2.247"
    The average for these OAL was 2.870

    Average differences between factory and hand chambered to lands was .093" delta measured on the ogive and .166" delta for OAL on average...

    Question is to what length do I seat these bullets for the OCW test for which I'm reloading, starting with the Interbonds...? It looks as if the factory loads are 0.1" off the lands...

    The Howa is an internal drop floor mag so I should have a bunch more room than the Tikka (max was a hair over 2.8" OAL). Where do I start seating? .04" thou off the lands .02" thou, or .01" off or .09" off the lands like the factory loads?

    Help or discussions greatly appreciated...

    Matt


     
  8. woods

    woods Well-Known Member

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    A little bit too much math and information for me to follow completely, especially with 2 guns. Every gun is different but IMO you COULD follow these basic rules:

    1. Load no longer than .025" less than the magazine length. That should keep recoil from your bullet tips
    2. Load no closer than .020" off the lands. IMO in the zone from .020" off the lands to seating into the lands, seating depth consistancy becomes hyper critical and a seating a few thousandths one way or the other will have a more drastic effect on POI
    3. With monometals like Barnes start .050" off the lands
    4. Stick with one seating depth until you have run up the powder charge ladder to find the best powder charge, then you can experiment with changing seating depth.
    5. If you want to change seating depth, go away from the lands in at least .010" increments and it would save time and barrel wear to go in leaps of +.025" each time

    For me, I start at .025" off the lands (when it will fit the mag) and 90% of the time find a powder charge that will fill my accuracy needs (hunting bullets in hunting rifles). Time then to load a bunch and do a bunch of long range shooting.
     
  9. zupatun

    zupatun Well-Known Member

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    Just thinking out loud in electrons,

    Looks like a 165 IB loaded to OAL of 2.80" is 0.071 away from the lands--max length for my old tikka. So, with the point below I should load the 165IB to 2.845 OAL or by my method 2.226 length measured on the Ogive with my bullet comparator...

    That bullet will look a little long, but I'll see how it fits in the HOWA internal mag and feeds.

    Matt

     
    Last edited: Aug 21, 2010
  10. woods

    woods Well-Known Member

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    If I am understanding correctly and the max magazine length for your old Tikka is 2.80", then you should load to an OAL of 2.775"

    2.80"-.025"=2.775"

    those will fit in your mag and may shoot just fine. There are some bullets that have an ogive shape that will allow you to seat closer to the lands if you want. You just have to try and see but I can't see not being able to use the magazine.
     
  11. zupatun

    zupatun Well-Known Member

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    My load for the tikka was 2.80, this is 0.071 from the lands...to get to 0.025 OFF the lands the bullet needs to be seated 0.046 CLOSER to the lands--making the2.846 comparator length of 2.226...

    Matt
     
    Last edited: Aug 21, 2010
  12. woods

    woods Well-Known Member

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    Yes, I thought your magazine length was 2.80"
     
  13. zupatun

    zupatun Well-Known Member

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    That was the mag length on the old Tikka I used to own. Now I have a re-barreled MCR Howa 1500 (thanks Kevin Cram!)...had some left-over ammo at 2.8" for reference.

    I will have to load one and see how it fits in the internal mag well of the Howa...

    Matt