Hornady OAL gauge numbers don't make sense.

[Matno]

Okay, silly rookie question. I've loaded "simple" stuff before (i.e. pistol rounds), but I'm new to reloading rifle cartridges for max accuracy. I finally got around to trying a Hornady OAL gauge today, and I'm a little confused by the numbers. I have a .223 Wylde chambered AR-15, which I know has slightly different dimensions than standard 223, but not terribly different. When I use the gauge with Hornady 55 grain soft point bullets, it gives me an overall length that is shorter than the recommended OAL according to the reloading manual. Measuring 2.151" vs 2.250". I'm pretty sure that mean that if I load to the recommended OAL, I will be pushing my bullets into the rifling.

I thought maybe it was a fluke, but after repeating the measurements dozens of times with multiple bullets, and getting very similar numbers repeatedly, I want to make sure I'm not doing something wrong. When I measure my chamber, the cannelures are actually not visible at the case neck, so the numbers seem backwards. I also measured length to the ogive, and although I don't know if there is a "standard" length for that, at least it was also consistent from bullet to bullet.

When I did the same measurements with 77gr SMKs (which are the only ones I've loaded up to now), I got numbers that were slightly longer than the recommended OAL. (Measuring 2.265" where recommended OAL is 2.260"). That gives me a relatively small "jump" but at least there is one! I really don't want to load up rounds that are over pressured, but I can't see why I'd be getting cartridges that look too short (based on the cannelure) but measure too long.

Can someone explain my dilemma?

 

[ChrisGarrett]

In your manual, what gun are they using that yields the 2.250"? If it's a bolt gun, one might have plenty of room to move the bullet out. If it's an AR-15, it seems like they're just loading to mag length (2.250" +/- .010") and calling it a day, with plenty of room to cheat out on most AR-15s.

Unless the throat of your AR-15 with Wylde chamber is somehow shorter than it should be, you're not tapping your bullets into the rifling as far as you can, would be my guess? You should feel the bullet stop, but you don't want to hammer it into the rifling, either.

There's also the possibility that you're not cinching the thumbscrew down precisely and it's backing out a bit, causing the bullet to drop back into the modified case, which is giving you a shorter measurement than you really should be getting.

These tools take a little bit of finesse to master, as touch is everything. A typical piece of printer paper is roughly .0035" thick, so it doesn't take much movement to make up a specific 'gap' in your measurement, but 1/10th of an inch is a pretty big number in COAL land.

Tap the bullet too hard and it's going to get pushed further into the rifling and give you a longer COAL, if you measure properly. Tap the bullet too lightly and you might not be butting up against the rifling, giving you a shorter COAL.

I have both the curved tool and I have the straight tool. What I do with the bolt gun tool is to take 3, or 5 bullets and measure each of them. I take three measurements per bullet, taking the thumbscrew on the tool and placing it at the 12:00 position and then measure, writing that down. Then I put the thumb screw at the 3:00 position and measure and then finally, the 9:00 position and measure.

I repeat this procedure for the next 2, or 4 bullets, having 3 measurements for each of those 3, or 5 bullets. For each bullet I average those 3 measurements together and then I average those 3, or 5 'averaged' measurements together, to get a final 'ballpark' measurement.

I mark each of those bullets and then place them all in a baggie with the measurements, so I can measure throat erosion going forward.

Now, with the semi-auto curved tool, you're not going to be able to take 3 measurements, because the ejection port is too narrow for you to rotate it into different orientations, so you're a bit SOL there, but you can work on your technique.

Try tapping a bit harder and be careful to tighten the thumbscrew down while NOT moving the outer sleeve, or rod.

Chris

 

[Matno]

Try tapping a bit harder and be careful to tighten the thumbscrew down while NOT moving the outer sleeve, or rod.

Chris

That must be the problem (not tapping hard enough). I was just gently pushing until I felt a distinct stop, but it was always light enough of a push that the bullet came right out by tipping the barrel up. Maybe I just need to get it closer to the point where the bullet sticks in the lands (but not all the way to that point). I turn small screws very carefully for a living (hand surgeon) so I don't think I'm getting variation there, but anything is possible. I have the straight gauge, so I'll try rotating it too.
Thanks!

 

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I start with the bullet and rod all the way out and let the lands push them in. Never failed me yet

 

[ChrisGarrett]

That must be the problem (not tapping hard enough). I was just gently pushing until I felt a distinct stop, but it was always light enough of a push that the bullet came right out by tipping the barrel up. Maybe I just need to get it closer to the point where the bullet sticks in the lands (but not all the way to that point). I turn small screws very carefully for a living (hand surgeon) so I don't think I'm getting variation there, but anything is possible. I have the straight gauge, so I'll try rotating it too.
Thanks!

I'm always having to tap my bullets out. In fact, when I do the above, I always have a rod in the bore.

Lead and jackets are soft, so you don't want to hammer the bullets in, but like I said, there's a certain finesse that needs to be acquired to run these tools properly. Plus, with my multiple measurements for each bullet for multiple bullets, I get a good average, so like gymnastics, I can essentially throw out the low and high scores and get a good average.

Plus, if you mark and save those bullets and their measurements, you can then measure for throat erosion as you put rounds down the tube and you'll have even more information!

Chris

 

[earthquake]

Make sure your chamber/throat is really clean. The first time i ever used one i had numbers that were way too short as well. Cleaned it and got what i was expecting. Like others have said, it's a technique to get it right with the tapping.

I insert it with my bullet in the case pretty far, slide the rod once the case is seated, and give it a few light taps, then carefully lock the screw. I always have to push the bullet out with a rod. I do this 12 - 15 times, toss the high/low and average them.

 

[shaggyaggie01]

Curious, for those that measure this, what is the purpose of measuring this on an ar? Mag length is your limiting factor, right?

 

[No1]

Curious, for those that measure this, what is the purpose of measuring this on an ar? Mag length is your limiting factor, right?

Not if you want a single shot AR. seriously though, I can't load 75g hornady match bullets to mag length. Therefore, I have a single shot mini-14 if I want to shoot these heavy bullets.