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  1. #1
    Marksman Max Volume's Avatar
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    OAL and reloading for accuracy

    Not mine but I found it on a Bookface group. Sorry, a bit of dyslexia there. lol The best thing about that site is closed groups who have plenty of usefull information.

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    OK...for new reloaders that want to load for accuracy you guys have been hearing me preach on OAL gauging your rifle to load for accuracy, why it is important and why you OAL the rifle for every different bullet you load and even for different brass so I decided to spend the afternoon taking pics and measurements to better explain the situation...it requires a few tools and some math. If you say buying correct tools is expensive or you dont like math....then maybe loading your own ammunition for accuracy isnt your cup of tea.
    JUST TO MAKE IT CLEAR THIS IS NOT A *COMPLETE GUIDE TO ACCURACY ARTICLE...ITS ABOUT HOW TO OAL/HEADSPACE YOUR RIFLE PROPERLY, WHAT THE TERMS HEADSPACE AND O-GIVE MEAN, WHY THEY ARE IMPORTANT AND WHY YOU SHOULD LEARN HOW TO USE THE TOOLS AND HOW TO MEASURE THEM. THIS IS A (BEGINNING) POINT TO LOAD DEVELOPMENT FOR ACCURACY AND THE MOST IMPORTANT BEGINNING POINT. FINDING THE DISTANCE FROM THE O-GIVE OF THE BULLET TO THE LANDS THAT YOUR BARREL LIKES WITH THE BULLET YOUR LOADING IS ONE OF THE MOST IMPORTANT FACTORS YOU NEED TO OVER COME WHEN DEVELOPING THE MOST ACCURATE LOAD FOR YOUR RIFLE BECAUSE IT IS A MAJOR PLAYER IN THE HARMONICS OF THE BULLET GOING THROUGH THE BARREL, YOU WANT THE BULLET TO FLOW THROUGH THE BARREL....NOT VIBRATE THROUGH IT. ANOTHER ISSUE IS THAT IF YOU (GUESS) AT SEATING DEPTH AND YOU HAVE IT TOO LONG AND THE BULLET IS PUSHED TOO FAR INTO THE LANDS IT CREATES EXCESS PRESSURE THE SAME AS TOO MUCH POWDER AND CAN BE DANGEROUS AND DO DAMAGE TO YOUR RIFLE. THIS SHOULD ALWAYS ALWAYS BE THE FIRST STEP IN YOUR LOAD DEVELOPMENT FOR YOUR RIFLE. (STARTING POINT). AFTER THIS STEP YOU PLAY WITH THE JUMP TO THE LANDS, POWDERS, SETTING CONCENTRICITY OF THE BULLET ETC. BUT THATS AN ENTIRELY DIFFERENT ARTICLE.
    For those of you that already know all of this thats great...I wrote this for the new guys that want to load precision that do not already know it so please ignore...but you may actually pick up a trick or two.
    This write up will show why NOT to use C.O.A.L. to load for precision loading but instead using a bullet comparator set measuring o-give. Even if you just want consistant accuracy for your AR platform and you need to keep your C.O.A.L. to magazine length you need to load one to max COAL and then take a o-give measurement and load with that measurement on every bullet because even some name brand match grade bullets can have a 0.010 to 0.040 difference in the length of the bullet but the o-give will be 0.000 to 0.001 difference normally so loading by o-give length will make the accuracy of your precision mag length loaded ammo more consistant.
    This write up will also show how two brands of the same weight and profile bullets will vary greatly at the o-give vs COAL measurement which is why if you load one brand at the same COAL as the other brand they will shoot totally different because there is a big difference in the jump to the lands of your rifle.
    Tools Needed: #1 OAL Gauge (hornady's straight OAL gauge will do bolt guns and AR platforms) it works very well and has a flat spot for the caliper arm to fit into to make measuring easy. #2 Headspace Comparator Set (checks shoulder to head of case measurment) #3 Bullet comparator set with insert body (checks head of case to O-GIVE of bullet) #4 Decent set of digital calipers (people will tell you manual calipers are more accurate..thats folk lore and simply not true)
    I compared Hornady Match BTHP 168gr vs Nossler Custom Competition BTHP 168gr bullets. You would think that they would be the same basic length and profile...I mean they are both the same weight and BTHP (boat tail hollow point) so they should be *close enough* right? Wrong...and here this proves why!
    Total Length of the two was only 0.009 of an inch different...so if you load them both to the same COAL they should shoot the same right? Again...wrong! When you check the o-give measurement they are 0.036 different where it actually counts...the distance from the o-give to the lands of your rifle. Doesnt seem like much difference until you look at the pictures of the two gap differences on the calipers and then there is that pesky little fact that at 500 yards and so on it can make the difference of a 1 inch group or a 3 inch group. Thats a big accuracy difference over a 0.036 difference in the length of the round!
    OK...enough of that, let's get to the math!
    Hornady full length of the unloaded bullet was 1.220
    Nossler full length of the unloaded bullet was 1.211
    Difference of 0.009
    NOW THE O-GIVE MEASUREMENT
    Hornady 0.605 vs Nossler 0.641 for a difference of 0.036!!!
    When I did the OAL of the rifle with both using the gauge and modified case here is the math:
    Hornady OAL using o-give to the lands 2.854
    Nossler OAL using 0-give to the lands 2.819
    Thats a difference of 0.035 which means I did a pretty accurate OAL measurement that matches within 0.001 of my bench measurement of both bullets!
    Now if you wanted to start load development for your rifle for accuracy and wanted to start with a 0.020 jump to the lands which is a common starting point this means #1 if you didnt take seperate OAL measurements in the rifle using both bullets and just used one and thought *CLOSE ENOUGH* guess what? One of them would have already exceeded the 0.020 jump you wanted by 0.015 before you even got started!!!
    Same goes with not doing a headspace measurement on the modified case used on the OAL guage vs the actual case being loaded to measure the shoulder set back difference...in my scenario here is the math:
    Modified case headspace measurement 1.623
    Actual case headspace measurement 1.619
    A difference of 0.004
    I hear guys say thats such a small difference it doesnt matter! This drives me nuts!
    The actual case being loaded has a shorter shoulder than the one you tested the OAL to the lands with...this means if you load your round by o-give using the math from the modified case you measured with....this means when you do the math for wanting a 0.020 jump...you now actually have a 0.024 jump.
    Now lets get really crazy! If you had went off the Hornady OAL measurement...then loaded the shorter Nossler thinking the two would be the same since they are same weight and profile....now your 0.039 off the lands when you think your 0.000 dead on the lands as the hornady was!
    See how fast this gets out of hand and why your precision ammo is shooting like absolute crap? Now your blaming the powder or the two brands of bullets when in reality its YOUR fault LOL
    I can not say it enough...a *close enough mentality has NO place in precision loading* !!! Or in any loading for that matter!
    Hope this helps everyone understand the terms OAL, Headspace and O-GIVE...how it applies to reloading and especially to precision reloading and shooting.

  2. #2
    Grandmaster sloughfoot's Avatar
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    Way too much distracting info. OAT is not even factored in. I been shooting for lots of years more than some of you been alive. Here is my advice. Load your ammo to magazine length at a moderate velocity. Life will be good. It will shoot just fine depending on the quality of your barrel and how hard you hold.
    Red Fire 372

  3. #3
    Expert Sniper 79's Avatar
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    Quote Originally Posted by sloughfoot View Post
    Way too much distracting info. OAT is not even factored in. I been shooting for lots of years more than some of you been alive. Here is my advice. Load your ammo to magazine length at a moderate velocity. Life will be good. It will shoot just fine depending on the quality of your barrel and how hard you hold.
    This is how I live. Life is good!

    Now if I had a range longer than a hundred yards and a pea shooter that was actually capable of shooting that far and unlimited time and money things might change...........maybe
    I won’t be wronged, I won’t be insulted, and I won’t be laid a hand on.

  4. #4
    Marksman Max Volume's Avatar
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    Yeah, too much for me also but I figured someone here may find it useful.

  5. #5
    Expert Robert Richardson's Avatar
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    Quote Originally Posted by sloughfoot View Post
    Way too much distracting info. OAT is not even factored in. I been shooting for lots of years more than some of you been alive. Here is my advice. Load your ammo to magazine length at a moderate velocity. Life will be good. It will shoot just fine depending on the quality of your barrel and how hard you hold.
    I totally agree.

  6. #6
    CZ Wizard llh1956's Avatar
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    Too much, it makes my head hurt!!

  7. #7
    Master Yeah's Avatar
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    I read:

    This write up will also show how two brands of the same weight and profile bullets will vary greatly at the o-give vs COAL measurement which is why if you load one brand at the same COAL as the other brand they will shoot totally different


    Which is a long way around the block to tell folks to learn what does what and why.
    Book elk have to ride on the wing struts.

  8. #8
    Expert
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    I learned many years ago to "smoke" the bullet of a case and bullet assembly to determine when the bullet touches the lands. Once determined, measure the OAL and set the seating station to allow the "Jump" you desire. If you are wanting to determine what shoots most accurately, run 10, rinse and repeat with a longer/shorter length and run 10, etc. Then hit the range!
    Life member NRA - FFL -03 (Collector) life LTCH

  9. #9
    Master
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    As soon as I saw the use of the term "O-GIVE" instead of ojive, I was out. Just another Internet rant that isn't worth the time to read.

    Every good reloading manual has an explanation of the four different primary means by which headspace is controlled; case rim, case mouth, shoulder or belt. The chamber itself can be cut within a certain range, as defined by SAAMI, or worked out between you and your gunsmith. Then there is the headspace created (and hopefully controlled) by how we size the brass going into our chambers. Understanding what your resizing die does, and doesn't do, as well as the actual dimensions of your chamber, is critical to determining how your brass should be sized. Fortunately for the masses, the overwhelming majority of factory chambers are cut properly and the overwhelming majority of factory ammo is (under) sized properly. The challenge for reloaders who want more than those potentially indiscriminate dimensions is to collect factual information about their firearms and their reloading equipment so that they can adjust their processes accordingly.

  10. #10
    Expert tenring's Avatar
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    Well worth the money, use on all my reloads. Simple to use, and order all the cases that you want to reload for. They even make a curved one for semi autos. https://www.midwayusa.com/product/1012747079/hornady-lock-n-load-overall-length-gauge-bolt-action

    Last edited by tenring; 1 Week Ago at 10:28.
    Keeping our future warriors in one piece @ MTek Weapon Systems

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