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Discussion Starter · #1 ·
I have the hornady oal gauge and bullet comparator. From what I understand I am using the oal gauge to find the seating depth where the bullet meets the throat. Is that correct? Can someone explain the steps to do this? And how I then use the bullet comparator with my calipers. Is finding this seating depth only good if I am using a competition seater die? or will I be able to seat my bullets to that exact length with a regular seating die?
 

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I use all the Hornady gauges myself, I have a few good posts here with good discussions, about setup, measurments and good use info. Search them they will give you some good heads up. You are correct the OAL gauge will give you the maximum allowable OAL your chamber will allow. The problem with using that is, it will be so long that the rounds won't fit in the mag. And function problems will be encountered. The comparator measures your OAL from the ogive of the bullet, allowing consistent measurements between any type of bullet. You will be able to keep it pretty close with a standard seater. But if you plan on running close to max. I would reccomend a competition seater. I can keep it +/- .004 with a standard one. See if these help, http://www.hornady.com/assets/files/manuals-current/metalic-reloading/LNL-OAL-Gauges.pdf , http://www.hornady.com/assets/files...lic-reloading/LNL-Headspace-Gauge-Bushing.pdf
 

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Discussion Starter · #3 ·
Ok So I did my measurements in my rifle. Where the bullet meets the lands I'm getting an oal of 2.843. I read it says you want a free travel of .020 to .040. It says anything over .040 will result in a loss of accuracy. I'm confused here. In my reloading manual it says the 168gr hpbt oal is 2.775.

Can someone help me better understand all this and what I should go for my oal?

Thanks.
 

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I seat 168 gain Noslers, to an OAL of 2.81"

I'm pretty sure 2.82", is the longest you can fit in a mag.
 

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Discussion Starter · #5 ·
So I should seat as close to 2.810 as I can but that will fit in magazine? If it's that close to maximum length will I have issues with feeding in the magazine? Like when the round being chambered forced forward may move the round beneath it in the magazine?

I'm very new to reloading so I'm just trying to get an idea based on my info I provided how the oal will affect my accuracy and by how much?
 

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Discussion Starter · #6 ·
Btw, I should note that I'm using the rcbs x die and did the initial resize and trimmed my brass to 1.995. With this short case for the first firing I'm not sure if this will affect my options on seating near 2.8. Any help would be appreciated. Thanks.
 

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Every mag is a little different in one way or another and that includes the max length of a cartridge that will fit.

All of my mags (25 from a variety of manufacturers) will accept up to 2.82" without a problem and most will take up to a 2.84" cartridge but I actually have one mag that will take a cartridge as long as 2.87" (a SA 5 round mag).

My favorite length up to about this past year has been 2.81". But I have been doing a lot more testing in the last year and I've come to the conclusion that 2.83" seems to be a better length for the 168 grain Hornady A-Max bullets.

The length of the bullets themselves will vary. It is not unusual, even within the same box/brand/manufacturer, to see bullets vary by 3 - 6 thousandths of an inch. Knowing this to be true, you have to realize that there are specific lengths that seem to work best with specific bullets and those lengths vary depending on bullet weights/brands/muzzle velocities etc. That's why I actually use the length at the bullet's ogive rather than the tip of the bullet for my overall length dimension. I use the Hornady OAL comparator to measure this dimension. Measuring at the ogive helps eliminate some of the confusion that results from the variation in actual bullet length.

How to do you know when your overall length is right? The solution for me has always been to start with a load recipe that I'm happy with and then just tweak the length a little either way to see if the performance improves but go no longer than 2.83" at the tip unless it will be a special round that I will only use in my long 5 round mag and even then I will only go out to a max of 2.86".
 

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Discussion Starter · #8 ·
Thanks. I want to make sure all my rounds will fit in any mag. I want it to be 100% reliable. I'm using the matchking 168gr bthp. Should I start at 2.8 oal and work from there?
 

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I think it is always a good idea to start with the recommendation from a valid reloading manual and go from there. 2.80" is probably how I would start and keep using that length until I was satisfied with the powder charge weight. Then I would start making adjustments to the length and experiment until I was satisfied that the group sizes and velocities were where I wanted them.
 

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Discus i use the X die as well and it's great, you will not need to retrim again the for the next loading of that case it will grow a few thousandths but will stay well within serviceable length. I also use sierra 168gr hpbt match #2200, and Hornady 168gr hpbt match bullets. I load them at 2.800" +/- .003" and all day long can create large holes through the center ring at 100yds. I use IMR 4895 and H4895. I read the Zediker info. when i started loading this round and it helped me alot. This load i describe is pretty much THE standard load for an M1A, if your rifle doesn't shoot it, Then send me your rifle!
 

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If you are going to use the Hornady OAL Gage along with the bullet you will be firing you will have to get the comparator insert to measure from the ogive or it will be a moot point, due to bullet irregularities measuring from base to tip will vary as much as .015" even with match bullets and will not give you a true reading and as far as the m14/M1A Service Rifle heck for that matter any semi-auto Service Rifle running close to the lands is going to be tough as you will be limited by mag length.
For me and my Springer I have a max OAL of 2.290" (Base to ogive) using a Nosler 168 CC which put's the base to tip approx 2.850"+ due to tip irregularities and won't reliability feed from the magizine so I run with a max of 2.240 which come out to be 2.810" and that is about all I can do and feed from all the mags I have, and if this boggles your mine wait until you start looking at using the headspace insert to control how far you bump the shoulder MCORPS1
 

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Hornady's recommended lengths of .010" & .020" off the lands for the respective load is just a place to start. I have loads anywhere from .003" to .050" depending on what a particular gun likes. Sometimes you hit it right the first time, sometimes it takes some playing around.
Some bullets just like to jump. I'm a big fan of Swift bullets, but was getting frustrated that accuracy just wasn't what I'd hoped for. Then I talked with a Swift factory rep whom told me that their bullets like to jump. I moved from .005" to .040" off the lands and groups shrank from 1 1/8" at 100 yards to three shots in one ragged hole at the same distance.
 

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so the overall strategy is to contact the lands to find it. Then you move back as long as necessary so that your bullets fit into the magazine? I understand that in theory a particular bullet might like +/- distance to the lands. How do you know how far in you can go until its dangerous. I understand that compacting the powder in a round can be dangerous unless specified by the powder or reloading manual?
 

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so the overall strategy is to contact the lands to find it. Then you move back as long as necessary so that your bullets fit into the magazine? I understand that in theory a particular bullet might like +/- distance to the lands. How do you know how far in you can go until its dangerous. I understand that compacting the powder in a round can be dangerous unless specified by the powder or reloading manual?
Shorter (than 2.800") is probably never better and, depending on your actual chamber, you may never be able to get even close to the lands. First of all, the longer rounds may not fit the magazine or you might be using a BTHP bullet and what's left of the bullet forward of the BT isn't sufficient to hold the bullet in the case. You probably need at least one bullet diameter of length holding the bullet.

So, you probably can't do much more than fiddle with 0.010" or so. Maybe that makes a difference, maybe not. My Rem 700 has an extremely long throat. If my measurements are right, I have about 0.150" of bullet jump to the lands. If I were to try to load anywhere near the lands, the bullet would fall out of the case (175 gr BTHP). Yet the gun shoots well under 1/2 MOA and I have one group where all 3 rounds went through the exact same hole - a 0" group! So, I load to 2.800" and leave the rest to Sierra and Remington.

Why is the throat so long? Well the SAAMI drawing shows that pretty clear. The throat itself (before the lands) is supposed to be 0.1637" and the forward half tapers. So, the bullet is sitting inside this throat area aligned with the centerline of the bore. Whether it touches the lands or not may not be that important in anything other than a bench rest gun. The bullet will be guided into the lands quite nicely.

http://www.saami.org/pubresources/cc_drawings/Rifle/308 Winchester.pdf

What you are measuring with the OAL gauge is the distance to the lands and you simply can't get there from here. And you probably don't need to if the throat is sized properly.

As I said above, you need a certain amount of contact between the bullet and the case neck just to keep the bullet in place. You really don't want the bullet moving around from recoil. In fact, shoot up a magazine's worth and measure the last round. Is the bullet where you put it?

Now, my M1A is a basic model so I don't have great expectations. I load to 2.800" and call it a day. As a bench rest gun, it's pretty poor - maybe 1-1/2 MOA, maybe 2. So I'm not going to try to make a silk purse out of a sow's ear. The rifle will easily hit the Ram silhouette at 500m and that is probably good enough.

All of that will change in a couple of weeks when my Super Match gets here. I will start with Federal Gold Medal Match (175 gr BTHP) and see how that goes. This ammo is loaded to exactly 2.800" so I will have every incentive to load mine to the same length, assuming it shoots well. I can use one of the comparators to measure my reloads against the factory loads.

The short answer? Load to 2.800" and vary the powder charge to get better groupings. If you study the Sierra manual, you will find that their "Accuracy Load" is almost never a maximum charge and will often be just middle-of-the-road in terms of velocity.

BTW, the Sierra accuracy load for the 175 gr BTHP is magnificent. Slow but very precise.

Richard
 

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One other thing: Loading such that the bullet touches the lands will increase pressure. That can be accommodated by varying the powder charge and powder selection. Some bench rest shooters leave the neck tension loose enough that the bullet is actually seated to the lands when the bolt is closed. But the loads have been developed specifically for this kind of loading and it clearly doesn't apply to a semi-auto. Remember, the M1A doesn't have anywhere near the camming action of a bolt gun when it comes to chambering a round.

I think you can get where you want to be in terms of grouping by leaving the OAL at 2.800" and varying the powder charge. Or possibly selecting a different bullet.

Richard
 
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