Bullet Ogive Consistency

[Thumb]

I've been getting ready to load up some rounds using Sierra .22 cal 77gr & 80gr HPBT Match bullets and started to check the ogives of random bullets from each box. What I found was not too reassuring.

On the 80gr bullets I got these readings: 1.984, 2.048, 2.046, 1.993, 1.987, 2.047, 2.048, 2.047

On the 77gr bullets I got these: 2.004, 2.012, 2.012, 1.954, 2.006, 1.967, 2.000, 1.988

Now if these are competition match grade bullets, I don't think they would be able to hold a group worthy of anything, maybe not.

My question is, is this normal for getting such dramatic measurments from the same lot of bullets? Now I know I'm not perfect and may have made a little mistake in pressure when pushing the bullets in but not .060 worth.

If it is, I guess you just have to go through each bullet and sort them out.

BTW, I have decided not to load up any 80gr loads because of the OAL required and my rifle will not handle it.

 

[223Randy]

Thumb,
I am confused as to what you were measuring? either you are measuring these in a case removed from your rifle? or something is incorrect, as neither of these bullets would be these lengths.

Please explain your steps to me.

 

[Thumb]

I am using a Hornady Lock-N-Load Overall Length Gage with a 223 special case. You insert a bullet that you want to measure to the lands. Insert the gauge with the bullet in it and then push the rod in just until you feel the bullet touch the lands. You then tighten down the rod and remove the gauge then measure the length of the round with the correct comparator and you get the bullet ogive for your barrel. Those are the readings I got when doing the above. Those lengths are from the base of the case to the ogive of the bullet.

Does that make it more understanding? I might have messed up on my description before.

 

[Lapua40X]

.064 is a very large number - be very careful to apply the same seating force on the bullet when using the Hornady gauge with each measurement. Run successive tests using the same bullet - the results should be consistent. If not, you're not applying consistent pressure on the bullet when taking the measurement.
I'd suggest that you measure the bullet lengths with a "naked' bullet - straight from the box. You'll find some variance, but not .064 or anything close to that.
Sort the bullets into groups and find the average bullet length, then use those bullets to determine the OAL to land contact using the Hornady gauge according to instructions.
When you seat the bullet you want to have the distance from the ogive to the lands consistent. That portion of the bullet that extends beyond the ogive, within reason, isn't critical.
I usually start with .020 jump and work from there.

 

[Thumb]

.064 is a very large number - be very careful to apply the same seating force on the bullet when using the Hornady gauge with each measurement. Run successive tests using the same bullet - the results should be consistent. If not, you're not applying consistent pressure on the bullet when taking the measurement.
I'd suggest that you measure the bullet lengths with a "naked' bullet - straight from the box. You'll find some variance, but not .064 or anything close to that.
Sort the bullets into groups and find the average bullet length, then use those bullets to determine the OAL to land contact using the Hornady gauge according to instructions.
When you seat the bullet you want to have the distance from the ogive to the lands consistent. That portion of the bullet that extends beyond the ogive, within reason, isn't critical.
I usually start with .020 jump and work from there.

I think I am applying the same amount of force, very slowly and just as I feel it touch I stop. Maybe I just need to practice. I did measure multiple bullets as you said "Naked" and all were in .002 of each other, either full length or measuring the ogive of just the bullets so it must be my "touch" giving me the headaches.

 

[Lapua40X]

I think I am applying the same amount of force, very slowly and just as I feel it touch I stop. Maybe I just need to practice.

I have found that I sometimes don't apply enough pressure on the stem to maintain proper contact at the shoulder in the chamber. When I fail to do that properly, the stem on the Hornady OAL gauge wants to move to the rear as I seat the bullet into the lands and that messes up the reading.

 

[Erik Cortina]

Try this: Push on the rod pretty hard and lock it while applying pressure. I have found that it's more consistent to apply heavy pressure than light pressure.

 

[amlevin]

To add to the other suggestions ----

Make sure that you've done a very thorough cleaning of the throat area before you start measuring using the Stoney Point/Hornady tool. Any fouling present can cause varying measurements as you insert the bullet each time.

As for keeping the seating pressure the same, I've found that pushing as hard as I can with my index finger held at right angle to the rod. This makes sure the bullet is seated in the lands and the pressure is limited to the muscle strength of my finger. The fact that the end of the rod is small and round also caused discomfort as you increase pressure so that has a limiting factor as well. You aren't going to drive the bullet into the lands any more than what may cause it to stick. Light pressure with a cleaning rod will push it out.

My readings are pretty much uniform, +/- .002" on average. This is within the normal spread of base/ogive measurements for most bullets I use.

 

[Thumb]

Thanks guys, I'll try those suggestions when I get back to it maybe later today. I'm setting up another powder drop I got for rifle only so I don't have to tear down every time I go from pistol to rifle or vice-versa.

 

[spclark]

Try this: Push on the rod pretty hard and lock it while applying pressure. I have found that it's more consistent to apply heavy pressure than light pressure.

Agreed, that's been my practice too. It's easier if you're using the 'bolt-gun' seating gauge tool that's all in a straight line. I started with gas guns & only have the dog-leg one but it works for me if I'm careful.

Thumb, you might try using the same comparator gauge to measure bullets' base-to-ogive length for sorting first. That's said to be critical for performance consistency as variances will affect available case volume when loaded rounds are fired and all rounds are seated by the ogive-to-case head dimension the same.

I haven't shot Sierras in a long time but folks I know who do say there can be several 'groups' of BtO numbers in a box. Bergers seem more consistent, JLK's don't vary more that 0.001" if that much.

 

[Thumb]

I'm using the straight one so what I do is take the upper off of the lower and test that way, it's a lot easier to handle that way at least for me. I'm not going to be loading up hundreds of these, just a box or two for whenever I need to go to that distance of shooting. Since I'm not really into competition(accuracy) shooting at those distances it would be a waste of time for me to load up all kinds of them. But it's always good to have and at least have the data if needed.