Variations in OAL when seating my bullets? I could use some help on this one.

[Rob.308]

Hiders,

I could use your help. I load and shoot a fair amount of .308 rounds. Just like the rest of us on this site I am always looking for the “MOST” accuracy I can squeeze out of every rifle.

Problem: when I seat my rounds I constantly get a difference in OAL that varies by about .007 I usually load about 50 rounds at a time.

Components used:

Winchester brass

Hornady 30501 rounds

Brass is cut to exactly 2.015

OAL varies between the two rifles I shoot most often

Each OAL measurement is taken from the bullets OGIVE.

I am using Redding Dies and each piece of brass is run through the full length resizing die before being trimmed to length.

I have cleaned the dies thoroughly and ensured there isn’t any debris in the dies.

Questions:
Is this the .007 difference normal for everyone?

Can I make the difference smaller or make it go away completely?

I greatly appreciate any input I can get on this issue.
Thanks,
Rob

 

[GrantA]

A couple things come to my mind-
Are you sure the seater plug in your die is making contact on the bullet's ogive? The plug may need to be lapped/polished to fit the bullet
What about the press? Consistency is key, is it mounted solidly? Same stroke every time?

 

[Rob.308]

Grant,

The press is solidly mounted to the bench. It is bolted down using three bolts and lock nuts. I will check the seater plug for sure. I believe it is coming in contact with the OGIVE but I will certainly check it to make sure. I would say that the stroke is the same for each round. I am pushing it firmly downward on each stroke to ensure I push the bullet consistently to the same depth for each round.

Thanks for your input!

Rob

 

[GrantA]

What kind of press? I suspect the .007 is nothing to fret about but as far as possibilities why, in addition to a wobbly seater plug fitment, if you are using a turret press there could be enough play in the toolhead to cause variations too.

 

[18Echo]

Are you compressing the powder? Have you measured just the bullets to see if the OGIVE is varying in length?

 

[Rob.308]

Grant,

I am using a Lee single stage press and I can't see the die moving at all. That was one of the things I thought it could be but I am pretty sure it isn't the problem, but I appreciate your input.

Rob

 

[Rob.308]

18 Echo,

I haven't measured the rounds yet....but I will do it today. I guess I just assumed that Hornady was making near perfect rounds. I will measure them today to see what I can find.

Thanks for your input!

 

[Rob.308]

Oh yea, I forgot to mention this in the other reply, but, I am not compressing the powder. The last set of rounds I did was with 43 grains of Varget in a .308. There is plenty of "free space" in the rounds when the rounds are seated.

Thanks again for you input!

 

[TOP PREDATOR]

Hornady 30501 BTHP....could it be the meplat (hollow tip) variations? you'll many with less than a flat nose.

try to have the seater resting on the ogive, not the very tippy top of the bullet, but will still vary as a OAL, but the amount of space between the bottom of the bullet and the powder inside the case should still be the same distance.

 

[Rob.308]

TP,

I am measuring the rounds on the OGIVE and not to the tip of the round. I do appreciate you input. Any other ideas?

Thanks,
Rob

 

[Rooster721]

I'm not familiar with 308, personally I shoot magnums over & above anything else.. BUT, (can say in the case of magnums) I have seen my own seating depths vary like that once the necks start becoming badly hardened*

Annealing cured my issue. Softened the brass and is giving me MUCH more uniform neck-tension and seating depths alike. Before, I too was seeing 0.002-0.007" variance.. now I'm down to 0.002" flat! Groups more consistent, flyers been minimized (have seen very big improvement)

So yah, not saying that's what's wrong in your 308.. it could be dies (as stated in someone elses post/it could be many things) but if you knew the dies were good before, and if that brass has possibly been worked over & over (and might be hardening) my money would be on a problem with your neck-tension sooner than anything else*

 

[Rob.308]

Rooster,

I will give that a try and see what I can come up with. I had shot the brass 3 times prior to reloading it this time.

Thanks for your input.

Rob

 

[sharpshooterbr]

Sounds like the seater plug is making contact with the tip of the bullet, rather than the ogive. All bullets will have quite a variance in tip length, especially hollow points. Ensure that the tip of the bullet is not hitting in the seater plug, if it is, you can either relieve the cup of the seater plug with a small drill bit to allow room for the bullet tip, or most of the die companies now offer seater plugs for vld type bullets that will have more depth in the seater plug.

One other trick I use when seating bullets, is to apply a dab of redding dry neck lube to the case neck...really smooths out bullet seating and yields better consistency.

 

[Rob.308]

Sharpshooter,

I checked the die and the tip of the rounds is not touching the top of the die. It is being seated by the ogive. Any other thoughts on this?

Thanks for you input,
Rob

 

[18Echo]

Have you measured just the projectiles yet?

 

[Rob.308]

18Echo,

I haven't measured just the rounds yet.....my issue is the length of the projectile shouldn't matter much in OAL (I could be wrong), but if around was a little longer wouldn't it just get pushed a little deeper into the case? I am guessing that the distance between the die and the shell holder remains constant and that in theory would make each round the same length. Thoughts??????

 

[GrantA]

A couple more thoughts for you.
Have you tried measuring the same round multiple times? Could be a measuring issue.
You could be seating the bullet a bit deeper while measuring too.
Are you using the comparator that clamps to the calipers, like Hornady? If so, everything good and tight?

Most importantly though, how do they shoot?


Sent from my DROID RAZR HD using Tapatalk

 

[Rob.308]

Grant,

I am using the comparator that clamps to the calipers, however, I have checked and rechecked everything and it all seems tight. I have also re-measured them several times and consistently get the same measurements.

They do shoot well. I have shot some great groups with them, this is really about figuring out why they are varying and if I can fix it what impact will it have on accuracy.

Thanks for your input!

 

[LawnMM]

I would guess its variations in the actual projectiles themselves that you are seeing the difference crop up from, though I would normally expect the difference to be from ogive to tip, not ogive to boat tail.

 

[PDXGS]

Shim the shell holder so that it's absolutely stationary while you press. I use a set of cheap feeler gauges- find the one that fits and trim it with some shears with about 1/2" of extra length. I've found this significantly reduces variability in COAL on my Rock Chucker and T7 turret press.

 

[mdmp5]

Rob 308,

Your variance in seating depth is due to the variance between bullets, and nothing more. The seating stem on your redding die is a diameter of less than .300, so it is indexing off a spot on the bullet forward of the true ogive and of the lands contact point.

 

[918v]

Consider you are shooting a mass produced bullet.

That kind of variance is normal.

 

[mtang45]

I posted a similar question a week or so ago and the correct answer took a bit to sink in. The difference is due to where you are measuring length on the ogive and where the seater makes contact with the ogive. If you were measuring at the exact same location as where the seater makes contact, then yes you could expect zero variation.

One more comment, even if the above measuring and seating points were coincident on the ogive there would still be variation between that location and the actual datum line on the ogive that makes initial contact with the lands. Ideally to eliminate all measuring and real variation those three contact points should be the same.

 

[09cs]

I had this problem today with my Lee dies as well, lot of good info here.

 

[anarchist]

I've had the same issue with my RCBS Competition dies and the SMK 175. In my case, it's just variations in the bullets. I haven't been to the Sierra plant, but I assume they have multiple machines making the 175 and all dumping them into 55 gallon barrels. Each of those dies in those machines have to be in a different state of wear. If you could get the production of just one machine, I'm sure the consistency would go up. Everything has tolerances, otherwise they'd be too expensive.

I talked to a bench rest shooter about this. His approach is to seat the bullets and then measure the OAL. Group the rounds by length and then tweak the die for each group until you get them all to the desired depth. If you did that on a per round basis, it'd take you forever. This came from a guy who shoots nothing but custom bullets, so that tells me that even the custom bullets have tolerances.