Measuring cartridge overall lentgh.

[Alpha1]

Is it normal to get different measurements with the same batch of bullets. I measured ten bullets and got seven different measurements am I right in thinking that I should take a average of the ten.
Or should I be batching them by weight and then measuring them.
Or should I just use one bullet and work from that measurement.

[ovenpaa]

It is quite normal to see variations in the same lot of bullets. Depending on the level you wish to shoot at you could end up weighing and sorting cases by volume, sorting bullets by weight and then sub dividing by length and location of bearing surface....

Of course you could just load them out of the box and shoot them...

[John25]

I had measurable variances of a couple of thou. in OAL after measuring my 7mm rounds with a 'Dolphin' last year.

I shot less than 1/4' elevation 1000x a Blair Athol.

I am sure the ammunition was capable of better, I shot to my usual tango zero standard, at least two 'called bad' shots per string.

As OP says, load em' and shoot em', variances of a couple of thou. and a tenth of a grain are not going to throw you off the target.

:cheers:

[The Cupcake Kid]

Different people will have different opinions on this, so these are just my thoughts...

If you have the time and inclination, measure the length of each bullet (from ogive to base) in a box of 100 and sort them using the standard deviation method. This article will help: http://www.castbullet.com/shooting/standard.htm
This will give you a method to batch your bullets by bearing length in a more scientific way than just dividing them up into several lots arbitrarily.

Or, if you don't have so much time, just pick 10 bullets at random and take the average of those and don't worry about the variations in a box.
(You can also sort by weight and sub-divide your different bearing length batches into different weight batches as well, but IMO that's a bit OTT for most people).

Once you've done that, use one of the bullets which has the average measurement and keep that as your reference bullet FOR THAT LOT NUMBER! (bullet shape and length can and does change from lot to lot so make sure you repeat the process when you buy a new batch of bullets with a different lot #).

Using just this bullet, start taking your OAL measurements with your gauge. Now, the reason you don't get the same OAL measurement every time is because the measurement depends on how accurately you can determine at what point the bullet just touches the start of the rifling. This is very difficult to do with just your feel and especially with a stoney point gauge there are other factors which get in the way of that 'feel'.

Try these tips and see if you get a more consistent measurement:

Check the bullet slides smoothly in and out of the case attached to the gauge. If not, debur and chamfer and maybe use some fine sandpaper on the inside of the neck.

When you push the gauge into the chamber, the neck of the case may be constricted very slightly by the chamber, which will then increase friction between the inside of the neck and the bullet. Sometimes this can make it feel like you've hit the rifling with the bullet, but it's actually just the neck gripping the bullet. If you think this may be happening, ease the gauge out of the chamber very slightly and gently push the bullet in again until it touches the lands and then push the case back into the chamber before locking off the set screw.

The whole thing is dependent on how consistent you are with the force you use to push the bullet into the rifling. I've got more consistent results by using gravity as the force... With the rifle horizontal, put the gauge into the chamber and then tip the rifle until the muzzle points down, allowing the bullet to fall by its own weight into the rifling. Then lock off the gauge, tip the rifle back and remove the gauge as normal.

Try these methods and see if it helps. Ultimately, whatever you do, you will not get the same reading every time so you will have to take the average or just eliminate the ones which look wrong.

[EagerNoSkill]

Cheers Dave, I'll PM your PA razz
..anyway, back to the thread (sorry Alpha )....

No worries.
I am not convinced about this measuring from the ogive looking at the numbers I am getting.

http://www.full-bore.co.uk/viewtopic.ph ... e&start=10
OVENPAA referred to me as such "Tim (ENS) has put a lot of time into working with Bergers and checks and batch sorts every single bullet he shoots including weight and bearing surface length, he may even be measuring the location of the bearing surface in relation to the base, certainly I know others are as I have built the comparator systems for them. "

Long distance accuracy shooting is about consistency - BUT and this is important - it is within batches of 15 to 25 shots
Think within strings of shots or matches...

The front ogive is part of overall Bearing Surface measurements you must consider and it does make a massive difference .... in my humble opinion!
All thing being equal even if you loaded your bullets to the identical COAL - base to Ogive you still have some bullets deeper into the case and more pressure for a given powder charge.

I use the Shooting Shed upright system to measure and batch my bullets

Here is a thread with some sorting / batching and pics - it is worth the read
http://www.full-bore.co.uk/viewtopic.ph ... ace#p98712

My findings of the bearing surfaces to date are:
Sierra 2156 : range from 0 to 25 thou : Groups typically clump 0-3 4-6 14-18 21-25
Lapua Scenar : range from 0 to 15 thou : Groups typically clump 0-3 4-6 7-9 10+
Berger 155.5: range from 0 to 6 thou : Groups typically clump 0-2 3-4 5-6
Berger Hybrid 155: range from 0 to 9 thou : Groups typically clump 0-3 4-6 7-9
Berger 185 Jug : range from 0 to 6 thou : Groups typically clump 0-2 3-4 5-6

What does that BS difference mean - well velocity differential that will cause verticals! Considering that 20 fps difference at muzzle can mean .4 to .5 moa at 1000 yards. So all thing being equal what extra muzzle velocity does an extra 10 or 15 thou of bearing surface add!

So if the bulk of your bullets are in say 3-4 group - suddenly you get 1 (group 0-2) - 0.5 low..... so you adjust a little and Murphies law gets you a group 7-9 = 0.5 or 0.6 higher......
So you gave a low 5 and a high 4 or worse a Low 4 and a high 4 - either way 1 or 2 points down and much confusion. :roll:

As John25 will tell you 2 points aren't important at all - that was the margin I won the Euro's by after 112 shots!!
Top competitors like Russell Simmond fight for and cling to every single point! They all count!

[Alpha1]

It is quite normal to see variations in the same lot of bullets. Depending on the level you wish to shoot at you could end up weighing and sorting cases by volume, sorting bullets by weight and then sub dividing by length and location of bearing surface....

Of course you could just load them out of the box and shoot them...

I have been loading and shooting them out of the box for a long time now.

This exercise is a learning curve for me. My aim is to gain a better understanding of how OAL and COAL can influence the size of my groups. (Maybe)
Some interesting information up to now and I thank you guys for taking the time to answer my questions.
My initial stab at it has resulted in a lot of variations in the measurements I need to understand how you interpret this data and put it to use.
I am having another measuring session this evening. Should be fun.

[Alpha1]

Measured a full box of 168grain match kings I am beginning to see a pattern. I can see how one of Ovenpaas made to measure jobs would make a difference.

[ovenpaa]

Two tips to add.

A phosphor bronze brush in a cordless drill passed back and forth inside the neck polishes it quite nicely and reduces friction in your case when checking initial OAL. I prefer to machine mine so they are a smooth fit with no discernible rocking of the bullet in the neck.

Paint the bullet ogive with a black permanent marker pen and then test the OAL, the marks from the land will be clearer and show if you are pressing too hard.

[Alpha1]

Out of a box of 100 .308 bullets I have 43 that measure 0.6180 to the ogive.
To morrow I am going to batch weigh them.
This is fun

[Sim G]

This is fun

There is a fella in our club who is now utterly convinced that he only shoots so that he can reload......