Bullet seating coal differences

[grizzly63]

Loading some 180 Nos BT into 300WSM and Coal I'm aiming for is 3.070 but a couple of the bullets ended up at 3.090. What is the cause of this. I assume the bullet seating is done off of the ogive so why are some longer? are the jackets not all symmetrical ? Is this a normal thing. I'm using Lee dies which I have had great luck with.

 

[Elktrack]

Loading some 180 Nos BT into 300WSM and Coal I'm aiming for is 3.070 but a couple of the bullets ended up at 3.090. What is the cause of this. I assume the bullet seating is done off of the ogive so why are some longer? are the jackets not all symmetrical ? Is this a normal thing. I'm using Lee dies which I have had great luck with.

That will drive a guy nuckin futs! I’ve dealt with this before and talked to most of my buddies that load and they all have experienced it before. It’s kind of a mystery because there’s so many factors that could contribute. ie,

Consistent speed and same force when seating. Don’t slam the arm down on one and go slow on the next. Be consistent.

Make sure everything is adjusted and tightened properly.

Obviously, check bullets. Most unlikely but could have a variance.

Neck tension is different from one piece of brass to the next.

Inconsistent chamfering.

Slight amount of slop in the seating stem.

Bullet not entering the die concentrically.

Seating over compressed loads.

Obviously you’re paying attention to details or you wouldn’t be concerned about it. I can tell you that I personally have never been able to detect any difference in my loads that have had this issue. I’m not a bench rest competitor chasing teeny tiny groups but I do like small groups and this kinda stuff makes me crazy. It’s even more annoying because I don’t experience it with every single caliber. I’ve got a 22-250 set up that comes out dead nuts exact consistently and I haven’t adjusted those dies for several years.
Measure some factory ammo and you will see the same thing.

I’d love to know what you find out.
Good luck

 

[HiMtnHntr]

Use a bullet comparator and go off of the ogive and you’ll get more consistency.

You can use the comparator to check uniformity of bullets before you load them as well.

Measuring COAL based on bullet tips is far less consistent.

 

[shb]

Measure over all length of 5 bullets , just the bullet, and you'll pull your hair out.

 

[Sheltowee]

Tough for bullet manufacturers to get those little plastic tips consistent down to the thousandths of inches. Compounding that is the propensity for those tips to get slightly dinged during shipment. Hornady and Nosler seemed the most consistent for me, Barnes a lot less so. I don't even bother measure COAL for most of my rifle rounds anymore. As several others have mentioned, buy a set of bullet comparators for your calipers, work from the cartridge base to ogive length (CBOL), go forth and prosper.

 

[N2TRKYS]

Base to ogive is inconsistent, as well. None of it matters. I kept reading about base to ogive measuring was the only way to do it. Well, I learned that that wasn’t true.

I don’t even worry about the ogive measurement anymore. I measure COAL and rock on. Neither of those two types of measurements are perfect.

 

[std7mag]

@N2TRKYS is spot on!

Talking with a custom bullet maker, he claims that getting the ogive consistent is the hardest part.
It varies enough that he will box up different base to ogive measurements for sale.

Of course his buyers have been known to weigh primers.....

 

[yakimanoob]

I don't have any evidence for this, but my gut says that MOST of the variance in seating depth (and the resulting COAL) is due to the variance in concentricity when loading. If concentricity is off, then length will be too, regardless of whether you're measuring to the ogive or the tip.

This is assuming you have very clean press contact points. Any dust, dirt, excess oil, etc where the case holder joins to the press cylinder, in the holder itself, or in the seating stem can cause lots of variance. Cleaning and re-trying should always be the first task when unexpected errors pop up.

 

[cowboy]

Don’t overlook the obvious- your vernier caliper quality and your personal use of it.

Take one loaded round, measure that same loaded round multiple times writing down the number you get the first go at it and see what your results are. Don’t try and get your last number or try to fool yourself. Have somebody else do the same with the same loaded round and compare. A lot of people would be surprised at the results.

Even better than one loaded round use say 3 of them and alternate readings.

Inferior equipment or procedures will never produce exact repeatable results.

 

[elevatorman]

The thing is the dies press the bullet in from the tip. So coal should be the same for them all right? I never check after setup. I check coal when setting my dies up to get my off the lands set. Then they're the same after that. I imagine the ogive might vary a tad

 

[Muleyfanatic]

Like everyone has said smooth consistent operation of lever. If getting differences measuring off o-give I would look at neck tension. I have had better results after annealing brass.

 

[yakimanoob]

The thing is the dies press the bullet in from the tip.

They do not. The cone in the die is (or certainly should be, anyway) quite a bit steeper than the cone of the bullet near the tip, so the die grips the bullet along a ring a little below the tip itself.

 

[yakimanoob]

Don’t overlook the obvious- your vernier caliper quality and your personal use of it.

Take one loaded round, measure that same loaded round multiple times writing down the number you get the first go at it and see what your results are. Don’t try and get your last number or try to fool yourself. Have somebody else do the same with the same loaded round and compare. A lot of people would be surprised at the results.

Even better than one loaded round use say 3 of them and alternate readings.

Inferior equipment or procedures will never produce exact repeatable results.

100% agree with this concept.

My only nitpick is to mention that someone else's measurements are irrelevant as long as your only concern is consistency (which is almost always the case in reloading). It's not important what the *true* CBTO or COAL measurements are, unless for some reason you're trying to compare to SAAMI spec or something like that. So it doesn't matter if your buddy gets a different measurement; what's important is that all your measurements are the same.