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Thread: Cartridge overall length

  1. #1

    Default Cartridge overall length

    I started reloading about 6 years ago. I pretty much only hunt big game with one gun and I found a load I liked and I haven't changed it since. Now I'm helping a friend lean to reload and I remember when I was figuring my cartridge overall length I either read or was told to make the length just long enough so I could barely lower the bolt, then back off .05 inches so as to get an accurate round without risking dangerously high pressure by making the length too long. I was reading back through my books and couldn't find the reference. I was wondering if this sounds appropriate to you guys? Thanks for your help.

    Luke

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    Member tccak71's Avatar
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    Don't know if you read that in a reloading manual or not but Marshall Stanton at Bear Tooth Bullets recommends what you stated (at least for lead cast bullets)- making the length long enough to barely close the bolt than backing it off. I'll have to look in the BTB technical guide to find exactly what he says.

    Tim

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    Quote Originally Posted by Olaf View Post
    I started reloading about 6 years ago. I pretty much only hunt big game with one gun and I found a load I liked and I haven't changed it since. Now I'm helping a friend lean to reload and I remember when I was figuring my cartridge overall length I either read or was told to make the length just long enough so I could barely lower the bolt, then back off .05 inches so as to get an accurate round without risking dangerously high pressure by making the length too long. I was reading back through my books and couldn't find the reference. I was wondering if this sounds appropriate to you guys? Thanks for your help.

    Luke
    COAL is adjusted from the OAL to the lands in your particular rifle. I like to be .030 off the lands, so my bullet doesn't touch.

    There are various ways to find OAL to the lands.

    You can seat a bullet long and chamber it, and the bullet seats against the lands, and can be measured, IF IT DIDN'T MOVE on ya. Most people have some way of making the bullet loose enough to move in the neck when the round is chambered, and tight enough so it won't stick in the barrel and lengthen when you take it out. I size a small portion of the neck. Some people split a sized case neck.

    When you get the OAL, you can seat the bullet deeper, .030 for example, if that's what you're after.

    I sometimes size a tiny portion of the neck to hold the bullet with a little tension. On occasion, Iíve even used a fired case without any sizing, IF the bullet fits tight enough.

    I've read about, how to smoke the bullet or use a Sharpie on it, trying different seating depths until they can barely see marks from the lands on the bullet.

    ďA SIMPLE way, Iíve been using of late, is to put a bullet in the chamber, and hold it there. (With a Pencil, if you have a Bolt Action rifle.

    Put a wooden dowel down the barrel to touch the bullet, and mark the dowel at the end of the barrel with a knife. Then take the bullet out, and close the bolt and push the dowel against the bolt, and mark it again.

    The Max OAL for (a cartridge with) this bullet is the distance between the marks. You can measure that with a Dial CaliperĒ.

    It may not be as accurate as seating bullets long, and chambering the cartridge.

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    Thanks for the replies. It was helpful.

    Luke

  5. #5

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    Remember that this length will differ for every bullet type that you use because of the different ogive each bullet has. A Barnes TSX and a Speer Grand Slam will have very different OAL in the same rifle when both bullets are just touching the rifling lands.

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    Member HuntKodiak's Avatar
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    I too use the doweling method that Smitty mentioned, and yes, you absolutely have to do this for each different bullet manf & type you will reload. Two addional points:

    Don't dry fire your rifle before this measurement because the protruding firing pin will throw off the measurement.

    Because you are marking the dowel at the end of the barrel, there could be some variance in how you mark the wood dowel. I use a mechanical pencil with the lead extended so I can do my best to hold it at a right angle to the muzzle while marking the dowel. I recommend you repeat the measurement 2 or 3 times just to make sure you are getting the same measurement. I erase the pencil markings after each measurement to remove any potential influence over the next time I measure. I also use the pencil because it allows me to use the same 1/4" dowel for all my rifles except my .223.

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    Quote Originally Posted by HuntKodiak View Post
    I use a mechanical pencil with the lead extended so I can do my best to hold it at a right angle to the muzzle while marking the dowel. I recommend you repeat the measurement 2 or 3 times just to make sure you are getting the same measurement. I erase the pencil markings after each measurement to remove any potential influence over the next time I measure. I also use the pencil because it allows me to use the same 1/4" dowel for all my rifles except my .223.
    Hmmm, I'll allow that.

    I'll probably even TRY it. Thanks for the idear.

    Your life would be simpler if you didn't have so many rifles. You know that don'cha?

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    Member HuntKodiak's Avatar
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    But it wouldn't be nearly as much fun Smitty!

    Mike

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    I've always coated a dummy round's bullet with marking pen, leaving the bullet out longer than standard recommended overall length. If the coating has marks in it from the bullet hitting the lands after chambering, after touching up the rifling marks, I seat the bullet about .020" deeper until the bullet doesn't have marks on it from the ends of the lands. Then I leave it, unless I need a specific recommended distance off the lands for the load I'm working up if it's for utmost accuracy, but not for hunting loads. I then have a dummy load for that bullet in that cartridge for future use in that rifle. I have about 60 dummy rounds I doubt I'll ever use again, lol.

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    Quote Originally Posted by mauserboy View Post
    I have about 60 dummy rounds I doubt I'll ever use again, lol.
    Do you spose, that's why they call them "dummy rounds"????

    Nahh,

    Smitty of the North
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  11. #11

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    Doh! And they're not even round.

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    I've always used candle smoke til it is smudged then seat it .020 deeper.

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    One important point to remember is that the length that reaches (or gets close to) the lands is not always possible to use in a repeater rifle. I have several rifles where if I seat the bullet out enough to be close to the lands the COAL is longer than the magazine will take. This seams to be especially true of short actions.

    I payed for this the hard way the first time. I did all my load development putting in one at a time while shooting off the bench. Once I found a good load, I loaded a bunch. When it came time to go hunting I went to fill my magazine and found the bullets were too long to fit. Doh!

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    Quote Originally Posted by AKArcherdaddy View Post
    One important point to remember is that the length that reaches (or gets close to) the lands is not always possible to use in a repeater rifle. I have several rifles where if I seat the bullet out enough to be close to the lands the COAL is longer than the magazine will take. This seams to be especially true of short actions.

    I payed for this the hard way the first time. I did all my load development putting in one at a time while shooting off the bench. Once I found a good load, I loaded a bunch. When it came time to go hunting I went to fill my magazine and found the bullets were too long to fit. Doh!
    LOL, I worked up a common load to fit in 2 diff guns once - did the same thing - loaded a 100 or so then found one of the guns ( diff brand ) would not accept them in the magazine!
    When asked what state I live in I say "The State of Confusion", better known as IL....

  15. #15

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    Couple of things:

    1. Midway USA sells a little plastic gizmo they call the Cartridge Overall Length Gauge (#190-644). Regular price is around $16, but its often on sale. Its pretty much just a fancified version of what Smitty described. I have one and use it with every new bullet design I try in any given rifle (see ANGCorsair's reply)

    2. You have be careful using the rule of thumb about being barely able to lower the bolt, and then backing off .050". If your cartridge resizing isn't quite right (this would be headspacing issue), you could be feeling that resistance on the shoulder of the cartridge, not the bullet entering the throat of the barrel. Is that about as clear as mud? What I'm trying to say is, make sure that you are resizing your cases correctly -- not too long and not too short. Too long and you get insufficient headspace; too short and you get excessive headspace. THEN, make sure your case length is right -- i.e., does not exceed SAAMI specs. Only after these two steps are done can you "play" with bullet protrusion from the case, or COAL (cartridge over all length). Some loading manuals will recommend that you stay out of the barrel by .050", some will say less. Its a variable you can adjust for, but only to the extent your rifle's magazine will allow. I generally back off about .020".
    In God We Trust.

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    Member Armymark's Avatar
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    I always make it a point to teach people new to reloading to use the SAMMI specs. Show them where to find it and to always work from there. That way they can customize after the know the limits and how the find and achieve them. Some folks may have more than one gun of the caliber and try to use the same cartridge formed for a single rifle. Just a suggestion, recommend you teach the fundamentals and move on from there.

  17. #17

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    Take a sharpie pen and completly color the bullet. Seat it in a resized case just enough to start the bullet and hold it in the case straight. Put it in the firearm and close the bolt. Let the lands seat the bullet for you. Eject the case and measure if bullet comes out with case. This will seldom hapen. Take a dowell or cleaning rod and slide down barrel and tap the bullet out. It will have distinct marks as to how far the bullet was pushed into the case as well as have marks where the bullet touched the lands. Reseat the bullet to this mark made by the case neck. That will give you the length that the bullet touches the lands. Seat bullet about .020 deeper and try it in magizine. If it will fit you have a place to start working up a load.

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