A tale of three lots (bullets).

[EdHarley]

After several years shooting 1K BR we had evolved to the point bullets were the limiting factor. Coming from the short range game and having made bullets for many many years I knew we needed the most accurate bullet we could make. Several of us convinced Randy Robinette to make us a flat base bullet. Flat base is easier to make than a boattail. Randy made a 187 gr bullet that was just easy to tune and shot very well. No need to measure anything. While this was moving along I noticed many of us had unexplained vertical fliers. Studying the bullet holes it clearly showed some bullets had a bit of yaw in them. Meplats passing through the paper off center. I had heard of a test Dr. Oehler and an F-class shooter, Larry Bartholomew, had done. They setup Oehler 43's at 127 yds and 1K yds. They tested 20 some bullets measuring BC's. Larry kindly shared the test results. I studied them for several evenings. The bullets with most uniform BC's, muzzle to target, were Hornady A-Max's. A light came on. It's the meplat dummy. Early one Saturday morning I went to the shop and made a meplat trimmer. It didn't take a rocket scientist to see that trimming the meplats to a uniform shape and diameter was an improvement. Bullet holes showed much less yaw. Meplats centered up. That lead to me getting a 43's myself and testing. Meplats matter. That lead to a test for Sierra where I installed their green varmint tip from 22 to 338 caliber. That proved to be even better. We got a slight increase in BC instead of a slight decrease from trimming the meplat. I remember one test shooting Sierra 105's. We had .020" difference in the BTO measurement out of the same box. Sierra does a much better job these days not mixing lots. We determined modest differences in length, BTO, do not matter in a given lot. Even .020" difference in BTO length got lost in the noise. We sorted every which way you could think of and it did not change much of anything. Obviously you want consistency within a given lot of good bullets. But slight variations did not show any change in performance. When shooting HPBT's unless you trim meplats, any use of OAL is misleading at best as the meplat has no relationship with the rest of the bullet. It's shape, form, length is a function of the lube, the point up die and the press stroke.
Bottom line is
WHAT DOES THE TARGET TELL YOU

Now that they are selling pointed bullets and the TMK with their artificial tips is there any point in measuring anything in a given lot of bullets?

 

[DaveTooley]

Now that they are selling pointed bullets and the TMK with their artificial tips is there any point in measuring anything in a given lot of bullets?

There can always be outliers in every box. For a hunting rifle I wouldn't. For a target rifle it depends on the required accuracy and what's on the awards table. At most I would do a quick BTO check looking for the odd ones. You may quickly get bored and move on.

 

[DaveTooley]

Here’s something to consider, the standard comparator inserts don’t actually touch the bullet at the same place that the bullet touches the rifling. So is it really a critical place to measure? Also I’ve never seen any testing on this, but if we’re jumping bullets. Is it really the distance to lands that’s important, or is it the internal case volume with a seated bullet? Since rifling wears with continuous shots, then your measurement there is changing as you shoot. People have found that chasing the lands isn’t that important.

It's the distance to the lands. The percentage change in internal capacity is so small there is no way to test the change. The ogive shape will be the same on every bullet coming out the same point up die. Any measured error is in the way we measure them.
Have your gunsmith cut a small section of barrel with the finish reamer. Cut a window in to see the neck length. Use it to measure bullets ( BTO ), case length, and shoulder bump. You'll still need something to record a measurement for seating depth. Example Wilson seater, the stem length. Whidden makes a gizzy that holds regular sizing bushings. So you could use a bushing -.002" under nominal bullet diameter to get closer to the base to bullet/barrel intersection.
I had a job trouble shooting an accuracy issue on some ammo. Multiple lots. I had 10 bushing, all the same size, surface ground so I had a sharp edge on the ID. 7 out of 10 would get essentially the same measurement. That enabled all the parties involved to do an apples to apples comparison.

 

[Mark W]

Here’s something to consider, the standard comparator inserts don’t actually touch the bullet at the same place that the bullet touches the rifling. So is it really a critical place to measure? Also I’ve never seen any testing on this, but if we’re jumping bullets. Is it really the distance to lands that’s important, or is it the internal case volume with a seated bullet? Since rifling wears with continuous shots, then your measurement there is changing as you shoot. People have found that chasing the lands isn’t that important.

I’ll argue that the comparator doesn’t necessarily need to measure to the exact point that the bullet touches the lands as long as it measures to a consistent point for a given bullet. Of course it would ideally be as close as possible. As an example, moving in or out .002 on the comparator should still move the actual contact point in or out by a corresponding amount. At the bare minimum, it provides a consistent repeatable point from which to measure for testing purposes.

 

[AlNyhus]

It's the distance to the lands. The percentage change in internal capacity is so small there is no way to test the change. The ogive shape will be the same on every bullet coming out the same point up die. Any measured error is in the way we measure them.

Morning, Dave. That's something that's hard for people to get their heads around and visualize. Provided the bullets come from the same point die, the difference in base-to-ogive length will be the difference in how much of the bullet is in the neck.

Any easy way for people to think of it is that any measured difference goes back, not forward.

When multiple dies may have been used, your idea of the windowed stub or using the stripped bolt 'Touch Point' method work well. If the barrel is off, Mike Ezell's EZ Checker is really slick and easy to use for multiple bullet profiles.

Good shootin' -Al

 

[Ringostar]

It's the distance to the lands. The percentage change in internal capacity is so small there is no way to test the change. The ogive shape will be the same on every bullet coming out the same point up die. Any measured error is in the way we measure them.
Have your gunsmith cut a small section of barrel with the finish reamer. Cut a window in to see the neck length. Use it to measure bullets ( BTO ), case length, and shoulder bump. You'll still need something to record a measurement for seating depth. Example Wilson seater, the stem length. Whidden makes a gizzy that holds regular sizing bushings. So you could use a bushing -.002" under nominal bullet diameter to get closer to the base to bullet/barrel intersection.
I had a job trouble shooting an accuracy issue on some ammo. Multiple lots. I had 10 bushing, all the same size, surface ground so I had a sharp edge on the ID. 7 out of 10 would get essentially the same measurement. That enabled all the parties involved to do an apples to apples comparison.

I like the idea of using neck bushings. You can get one the same size, or there about, as the actual drill hole size of your barrel. Or for those that want to measure at stem contact, can get one in that size range. Some people have gone to measuring only by total bullet length. I believe that I read somewhere that even Brian Litz quit measuring BTO and went to total length.