Runnout and Bullet sorting

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akinswi

New member
I recently picked up a Hornady bullet compartor. And I noticed I get pretty inconsistent readings measuring the ogive on my 168 grain SMKs. I noticed they do vary from .601 upto .605. But If I remeasure the same projectile twice it may read .604 when before it read .602. Also is this deviation enough for me to even worry about?

Before I commit the time to measure 500 of these. Is this normal? Do I just go with the first reading? I used to sort my bullets by weight but I thought I would try sorting by the ogive instead. I will be shooting these out of M1 Garand. I got very good results by sorting by weight.

I was also wondering if there is any correlation to the ogive being different +- 4 thousandths and runnout on the OAL.

Thanks
 
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Bart B.

New member
Those bullets are from a lot that Sierra tested under a half MOA at 200 yards as far as I know. That's the specs they have to meet. When they tested at 100 yards, 3/8 MOA was the limit and some tested under .2 MOA

The tolerances in your measurements are normal.

Get the lot number off the box then ask Sierra what they tested at.
 
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hounddawg

New member
For SMK's the + or - .004 is not unusual. It's not really worth measuring though. All it means is another .001 - .004 of the bullet is in inside the neck.

It's the cartridge base to ogive measurements that matter. When seating the shellholder and the stem of the seating die will be at the same point when the ram is at full stroke every time. Base to meplat may vary but base to ogive will be the same unless you vary the stroke or move the seating die adjustment
 
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milboltnut

Moderator
Separate ones that measure the same and load them. I have seen that most of them compare the same, the ones that don't you just have to adjust your bullet seater to compensate to keep your COAL that suits your rifle. I write the one that are the same inside the box, when I use them up, then adjust seater that's all
 
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Bart B.

New member
hounddawg said:
For SMK's the + or - .004 is not unusual. It's not really worth measuring though. All it means is another .001 - .004 of the bullet is in inside the neck.
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I disagree. That's another myth in the reloading process.

Bullet seating depth is very consistent because the seater stem doesn't touch the tip of the bullet tip. It's a circular touch point about midpoint on the ogive.

That spread is caused by the bullet jacket irregular shape at its tip caused by the pointing die. Measure several hollow point bullets from the base to tip then see the spread in thousandths.

It doesn't prevent their best match bullets from testing quarter MOA extreme spread at 200 yards.
 
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akinswi

New member
You are Correct Bart B,

This is One reason why Iam measuring by the ogive because thats How my Redding Competition seater die seats them. It will make my OAL more consistent.

I also believe the Redding seater stem is reamed to fit the ogive of 168 SmK in paticular. I could be mistaken on that.

Will
 
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Bart B.

New member
Remember the throat's bullet touch point erodes down the barrel .001 inch every few dozen shots.
 
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hounddawg

New member
Bullet seating depth is very consistent because the seater stem doesn't touch the tip of the bullet tip. It's a circular touch point about midpoint on the ogive.
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Base to meplat may vary but[/b] base to ogive will be the same[/B] unless you vary the stroke or move the seating die adjustment
Click to expand...

read my post(quote) and actually analyze what I said

if you measure 2 bullets from the base of the bullet to the ogive of the bullet and bullet 2 is .004 longer than bullet 1 when seated bullet 2 will have .004 more bullet inside the neck, however the base of the cartridge to the ogive of the bullet will still be the same. I know some have issues with spatial relationships but think about it a second
 
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milboltnut

Moderator
It appears that some have measured throat erosion down to the amount of rounds down the barrel. IDK, but some do.

Comparators no matter of manufacture, are not a throat/ogive mimic. I always thought about that. And the seater stem isn't one either. But I would say it's probably close enough when bullets are grouped with a comparator. Throat erosion does increase and the ogive to throat contact changes not only to where it contacts the ogive but positional, more forward or more aft.... no one can tell. Maybe that's one reason some guys seat the bullet touching the rifling.
 
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milboltnut

Moderator
Cortina is great, good vids. I started with making a dummy round, even with a smoked round. Best way to go. The mistake is a comparator isn't the way to measure off the lands, and its not the way to go to segregate bullet ogives. Part 2 vid essentially you are chasing the lands, as the throat wears so does the OAL.
 
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akinswi

New member
@ milboltnut,

Then what would be the best way to sort / segregate bullets? I want to make sure each Round I make has a consistent OAL.

Thanks
 
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milboltnut

Moderator
Akinswi

At this point segregating bullets, I have a Horandy comparator. I guess if you really wanted to get it right, Is to buy a positional tool, and a extra long dial indicator, and drop each bullet in the chamber, and make sure that are set relatively straight. LOL
dial indicator extensions
PITTSBURGH Multi-Position Magnetic Base
dial indicator

I think I found a way to get consistency for COAL. I lightly neck sized with a Lee Collet neck sizer, just enough to grip the bullet and use my OAL gauge. Once I have the OAL I unthread the case from to tool, place it in the shell holder and raise it into seater. I bought a multi-positional magnetic base tool from harbor freight today. Mounted it on my Lyman turret press to dial indicate the stem rod.
 
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hounddawg

New member
I want to make sure each Round I make has a consistent OAL.
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consistent overall length (OAL) or consistent base to ogive (BTO) ? Your seating die is hitting somewhere on the ogive so you will always get the same BTO at the point where the stem contacts your bullets. To get a consistent OAL you would have to modify the seating stem so it is hitting on the meplat of the bullet. To get consistent BTO measured by the comparator the seating stem would have to contact the bullet exactly at the same point on the ogive where the comparator is contacting the bullet or the bullets would have to have perfectly uniform same ogive measurements.

This is where reloaders drive themselves nuts. Unless the bullet ogives are perfectly uniform the seating stem will not be hitting the same spot on the ogive as the comparator will and the base of the bullet to the meplat will vary also. Therefore any variation in the ogive will result in a variation of BTO measurements when measured with a comparator and any variation in base to meplat on the bullet will result in base of the bullet to meplat differences unless the seating stem is contacting the meplat instead of the ogive which would result in BTO differences on the seated rounds. (OAL).

Now we measure each unseated bullet with our comparator and make sure the seating stem does not contact the meplat. Problem solved right ? Nope becasue unless the ogives are perfectly uniform or the comparator is contacting the bullet exactly where the seating stem contacts the bullet any differences in the ogives will translate into slightly different measurements on the finished rounds


What will always be consistent is the base of the finished round to the point on the ogive where the seating stem contacts the bullet which is why measuring the base of the bullet to the point on the ogive contacted by the comparator is a waste of time. That is unless your bullets are exactly the same which you have already stated is not true.

Simple right? I really need a whiteboard and a lectern to explain this:confused:


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imagine this exaggerated example

you have two bullets one has a VLD ogive the other a round nose. Both have the same base to meplat or overall length. The seating stem will contact both bullets at the same place on the ogive's diameter however that will not be the same point measuring from the base of the bullet. The VLD's meplat will will be extending farther into into the concave portion of the seating stem

The good news is most real world tests show a variance of .003 jump to have a minimal affect on accuracy
 
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milboltnut

Moderator
I believe Sierra was the only bullets that were consistent and didn't have to be different ogive measurements that I have.

Hounddawg

Simple right? I really need a whiteboard and a lecher to explain this
Click to expand...

I needed a reminder, however, I trusted the comparator completely but now believe a I have a different way and will try that. I think it'll work.
 
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hounddawg

New member
Just me but I stopped sweating the minutia of reloading. I do try and make good ammo and ammo that is a consistent as possible but I don't lose my mind over .01 gns of difference on powder weight or a primer that is .004 below flush instead of .003. Now I concentrate on my shooting skills such as cheek placement, consistent trigger pull, and working on my wind reading skills. I get a lot more return from my effort. I let the benchrest crowd worry about making the absolute perfect round, I just want sub MOA ammo out to 1000 yards and I get that with the ammo I make
 
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Rimfire5

New member
Bart B.

I think you might be off at least a decimal point.
But it could depend upon how close to Pmax the rounds were.

I have recorded some average measurements of wear on a .308 and 6.5mm CM.
.308 = 0.00036 inches per 2 dozen rounds based upon 6,000 rounds down the barrel.
6.5mm = 0.00029 inches per 2 dozen rounds based upon 3,000 rounds down the barrel.

The .308 had some number of rounds shot near Pmax early in its life, but the 6.5mm had all rounds shot in the middle of the load table.
That might account for some of the difference in our numbers.
 
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