What's a reasonable OAL spread: .308 Hornady 150g

[azrocks]

Just got through my first ever batch of rifle rounds (300AAC, load workup), but I'm wondering if my wandering OAL is going to make the results meaningless.

Using brand new brass all trimmed exactly the same. Dillon 550B with Dillon carbide dies (except crimp - that's lee FCD). Hornady 150g FMJ-BTs. Crimped light into the cannelure. Set an OAL at 2.070 before I started loading. But the resultant rounds range from 2.058 to 2.080.

The only thing I've loaded before is straight-walled pistol, & my OAL is always on the money, but those dies index on the nose of the bullet where it appears these index on the ogive.

Is this par for the course? Acceptable? Am I using the die wrong somehow? Bad bullets? Set me straight, por favor.

 

[Bhennessee1]

Just got through my first ever batch of rifle rounds (300AAC, load workup), but I'm wondering if my wandering OAL is going to make the results meaningless.

Using brand new brass all trimmed exactly the same. Dillon 550B with Dillon carbide dies (except crimp - that's lee FCD). Hornady 150g FMJ-BTs. Crimped light into the cannelure. Set an OAL at 2.070 before I started loading. But the resultant rounds range from 2.058 to 2.080.

The only thing I've loaded before is straight-walled pistol, & my OAL is always on the money, but those dies index on the nose of the bullet where it appears these index on the ogive.

Is this par for the course? Acceptable? Am I using the die wrong somehow? Bad bullets? Set me straight, por favor.

Make sure the shell plate is reasonably clean and tightened down far enough. In my experience a little spilled powder under the cases goes a long way toward messing up my oal.
In my opinion driving the ogive rather than the tip of the bullet with the seating stem gives a much better chance of consistent pressure. I noticed that the tips on the Hornady bullets I loaded today we're very inconsistent.

 

[azrocks]

Thank you, sir. No issues w/ shell plate. I cleaned, adjusted, & lubed everything prior to this project. No slop... right on the edge of being a hair too tight. All dies except powder are making light contact as the platform is raised to full extension so there's no way it's canting inconsistently.

Found an online reference saying up to .025" extreme spread was gtg and expected w/ bullets like this. I'm at .022" across 35 rounds. Hopefully that's the case:

http://bulletin.accurateshooter.com/2020/03/cartridge-base-to-ogive-cbto-length-factors-to-consider/

 

[Bhennessee1]

I just checked 50 rounds I loaded today on my 550 the spread was .007 it's .223 rcbs seater, Lee fcd, harnady bullets. I think you have some bad bullets or some calipers that are telling you lies. I'm not an expert by anyone's standards, but .022 seems like a big spread to me.

 

[azrocks]

Thanks again, Bhennessee1. Not my calipers, quality & calibrated. Not a mistake, triple-checked all measures. For better or worse, .022" extreme spread.

 

[jmorris]

Hornady 150g FMJ-BTs. Crimped light into the cannelure. Set an OAL at 2.070 before I started loading. But the resultant rounds range from 2.058 to 2.080.

The only thing I've loaded before is straight-walled pistol, & my OAL is always on the money, but those dies index on the nose of the bullet where it appears these index on the ogive.

If your equipment gives you .000” variation with pistol bullets and you think .022” is a lot of variation (sounds like a lot to me too) there are a couple things you could do as far as locating the issue.

I would start with the bullet, grab a hand full and measure them.




Don’t be surprised if they are not the same OAL. If they are .022” max/min, you can stop looking, you have found the cause.

On your rounds that are already loaded you can get special made devices that attach to the calipers that allow you to measure off the ogive.



Others that are more universal without buying or machining inserts With different ID’s.



Or the cheapest way and one that will be the exact point the seater contacts the bullet, is to use the seating stem itself.



If you have .022” using that last method, I’d say something is wrong for sure but I imagine that won’t be the case.

 

[azrocks]

@jmorris, Thank you so much! Now I know what I'll be doing today (and maybe ordering). Much appreciated.

 

[30Cal]

It’s a fodder bullet that goes into a box from a number of different sets of tooling. What you’re getting sounds about right. Even match bullets will have a good amount of variation and those should at least come off one set of tooling.

Check your gear and move on. The seating die shouldn’t be pushing on the point so where the point ends up is not really of concern for accuracy. If you chase that COAL measurement you’ll end up with a box of ammo that has a wide variation in bullet jump.

Also, don’t be surprised if the cannelure is not in the same spot all the time. You don’t have to use the cannelure, nor do you need to crimp for a bolt gun or gas gun.

 

[azrocks]

@30Cal, really appreciate the info. Only reason I used the cannelure is because it was there and actually lined up at the O.A.L. I had chosen based on other factors. Being generic .308 bullets I was actually surprised it did.

When you speak of the variation - even among match bullets - does that variation usually only extend from the ogive up? Is the distance from the base of the bullet to the ogive generally more consistent, so that even when the OAL varies the depth the bullet is seated in the case does not (as much)?

I'm going to try to use the seating stem today to see if I can measure from the base to the ogive & see if I get more consistent results.

 

[edwardware]

Hornady 150g FMJ-BTs. Crimped light into the cannelure. . . resultant rounds range from 2.058 to 2.080.

Assuming that your setup is tight, a 0.022" variation in tip to ogive is a bit more than I'd expect. Pull your seating stem out, use it as a comparator, and see if you have ogive variation; if you do it's your setup.

 

[azrocks]

Assuming that your setup is tight, a 0.022" variation in tip to ogive is a bit more than I'd expect. Pull your seating stem out, use it as a comparator, and see if you have ogive variation; if you do it's your setup.

I'm going to do exactly that today. Thank you, edwardware. Will post my findings.

 

[Rod47]

30Cal nailed it. Same bullet, multiple production machines, all mixed together.

 

[30Cal]

@30Cal, really appreciate the info. Only reason I used the cannelure is because it was there and actually lined up at the O.A.L. I had chosen based on other factors. Being generic .308 bullets I was actually surprised it did.

When you speak of the variation - even among match bullets - does that variation usually only extend from the ogive up? Is the distance from the base of the bullet to the ogive generally more consistent, so that even when the OAL varies the depth the bullet is seated in the case does not (as much)?

I'm going to try to use the seating stem today to see if I can measure from the base to the ogive & see if I get more consistent results.

Seating to the cannelure is fine, but probably not optimal for accuracy. That said, a cannelure is usually an indicator that the bullet design has sacrificed accuracy for reliability. That’s not to say they cant shoot surprisingly well. Some do and some are just dogs. My impression is that the Hornady makes a good one.

Open tipped bullets are the simplest design to get the most uniform outcome. The variation in length you get with them is mostly at the metplat (tip). Up until very recently, this was simply ignored because they shoot really well. Now you can buy premium bullets where that is trimmed back uniform.

seating die usually meets the bullet somewhere between the tip and the start of the ogive. When the press/die is set right, it’s easiest to assume that the ogive is getting consistently located. I’ve never taken the time with a comparator to get a feel for how much variation you may see; perhaps someone else has some info there.

 

[azrocks]

Alright, guys. Got it figured out. All is well in the world now. Thanks so much for all your advice!

I measured the remainder of the bullets from that package. Over 63 bullets, the extreme spread in length was .021" (again, my spread of loaded rounds COAL was .022"). Just as in my loaded rounds, 1 or 2 outliers is what opened up the spread. If I had trimmed the dataset excluding the highest & lowest values, both sets would be around .010" from high to low.

Even better, when I used the seating stem as @jmorris & @edwardware suggested to measure from the contact point of the die to the base of bullet, the spread was only .002". That included the most extreme examples of long/short bullets. I stopped measuring 1/2 through because it was obvious this measure was extremely consistent.

So yeah, to answer my own question: At least with these bullets, any variation in length is all from where the bullet seating die contacts the bullet up to the tip. I should have a very good foundation now to see what charges work, & what don't. Seating depth shouldn't vary by more that .002", & all cases trimmed to same length. Plus 110 meters like water (love it).