Reading OAL measurements

[richardca99]

I've often wondered how others do this -- particularly those who are building precision ammo. When I measure loaded ammo with my Starrett calipers, clamp-on comparator, and comparator base, my setup allows for very repeatable, precise readings. I use Redding competition micrometer seating dies for all bullet seating. Nevertheless, I will often get variance from round to round in terms of the OAL to ogive after seating. I attribute this (perhaps incorrectly) to variance in the bullet dimensions. In an effort to deal with the variance, I wind up seating all of my rounds to something greater than what I'm shooting for, and then "walking" down the OAL a thousandth at a time on each round until I get the reading I'm looking for. To say that this is painstaking is an understatement.

I'd love to just set the seating die, confirm the first round, and then load 30 rounds. However, when I do that, I invaribly wind up with a few that our out of spec by a couple of thousandths. For normal shooting, who cares. When I'm doing OAL testing, however, it matters. (And yes, I do have a rifle that allows me to see the variance on paper).

How do the rest of you tackle this issue. Most importantly, what's causing the variance? Is it bullet dimensions, or is it undulations in the case head causing it to sit less than level on the comparator base? Is it errors in measurement, and am I just not thinking about it correctly? I've fine tuned my measuring technique enough that I'm pretty confident it's not me, but I've been wrong before. Those of you who nitpick like I do, what are your thoughts, and how do you deal with this issue in your ammo?

 

[jonbearman]

It might be worth buying a bullet stand from sinclair and sorting by ogive. Then you would be able to just load.I myself dont get that picky when you are talking a thou or so.Have you tried targeting your results in groups to see if it matters?

 

[blastit37]

Try measuring from the base to ogive of the bullet. Some vary a great deal, others very little.

 

[wapiti25]

You are probably measuring on tip of the bullet. The tips vary as the bullet is formed. The tips are not a good place to measure for seating. There are tools to go with your calipers to measure on the ogive. One that I have found usefull is sold by Sinclair and looks like a large six sided nut, others clamp on your calipers. Start measuring from the ogive as that is where the bullet will first touch the barrel rifling.

 

[savageshooter86]

I think the OP is measuring to ogive using comparator.

I experienced the same situation and still trying to work it out. I did anneal my brass and size then I did over 50 rounds that were withing 001 to ogive of each other. Do the bullets feel the same when seating all of them? Neck tension the same on all the cases?

 

[richardca99]

I think the OP is measuring to ogive using comparator.

I experienced the same situation and still trying to work it out. I did anneal my brass and size then I did over 50 rounds that were withing 001 to ogive of each other. Do the bullets feel the same when seating all of them? Neck tension the same on all the cases?

I am definitely measuring to ogive, not to tip.

I anneal on every loading...every other at the most. Neck tension is identical, as I use a Lee Collet to size. As for the bullet seating...here's where I get confused. Even if the ogive occurs at a different place on each bullet, wouldn't the variance just be pushed into the case? In other words, if the seating die contacts each bullet at the same diameter point, then if the bullet were longer or shorter, it would just protrude more or less into the case as a result of the seating process. Why am I seeing the variance at the top of the bullet? This leads me to believe that it's actually variance at the case head.

 

[savageshooter86]

Why am I seeing the variance at the top of the bullet?

Lost me here. I thought you were measuring at ogive? If ogive vary to begin with the comparator will be off from bullet to bullet, then when you seat and measure off the ogive again for the reading it should still be off I believe?

How off are your seating depths?

Is the seater plug making good contact on bullet? Are you trimming the brass at all and chamferring after? How consistent can you measure using the tools(if you measure same round 15 times do you get same reading or does it vary a lot?)

 

[bheadboy]

three possibilities here, if you are mesuring to the ojive as indicated

The brass can be the problem as it will often spring back on the shoulder/neck area after seating causes it to collapse slightly at that area - so the brass is the "problem" -- anneal

2nd i have seen situations where the necks have been turned and there is low neck tension - that the air pressure compressed inside the case, on bullet seating will push the bullet out a few thousands - this is most more often the case when there is not a "full" case of powder or with stick powder - allowing more air inside the case.

3rd, the pressure you use "bumping" the ram when seating can easily cause the length to vary as much as you are seeing. it is very difficult to be exact in each stroke of the press and .001-2 is not out of reason to expect.

bob

 

[Shynloco]

You cannot regulate what a manufacturers of bullets produces hence you are relying on the accurate measurement of each bullet produced. That won't happened in a million years so you could measure every bullet's length and separate them which I believe is a total waste of time as there is an alternative...forget OAL measurement period because it'll drive you nuts. I measure each completed cartridge (using the comparator attached to my caliper) at the ojive and don't even waste my time with AOL. My casings are also carefully and closely trimmed to the same length so any slight variation in my measurement are negligable and have no affect on the consistency, repeatability and accuracy of my loads.

 

[Lapua40X]

Can't be sure but, based on your post and keen interest in consistency, I'm assuming you're a bench rest shooter. One of those who like to see one hole groups on the target. Welcome aboard.....
I have found that, unless I spend the bucks on match grade quality controlled production bullets, the ogive OAL varies .001 - .002 on the loaded round. Problem is that, if you try measuring each bullet from base to ogive, you end up with a number that doesn't help much because when seating the bullet the seater die doesn't care where the base of the bullet is. Then, if you try to measure from bullet tip to ogive, the bullet tip will inevitably be just slightly more rounded or pointed from round to round so you have another measurement that has little or no value.
I make certain that my seater die is impeccably clean and totally free of any lube. If it's match ammo I'm loading, I weigh each bullet and sort them. After loading each round I do very much what you're doing and cull any round that is out of ogive OAL tolerances by more than .001. Those above that mark get tweaked with another pass through the die, those under that mark are used as foulers or "just for fun" practice where I spend time on consistent physical hold and rest positioning of the rifle.
I've come to realize that spending too much time at the loading bench takes away from the time I can spend on the range so I'm not nearly as persnickety as I used to be.

 

[richardca99]

You cannot regulate what a manufacturers of bullets produces hence you are relying on the accurate measurement of each bullet produced. That won't happened in a million years so you could measure every bullet's length and separate them which I believe is a total waste of time as there is an alternative...forget OAL measurement period because it'll drive you nuts. I measure each completed cartridge (using the comparator attached to my caliper) at the ojive and don't even waste my time with AOL. My casings are also carefully and closely trimmed to the same length so any slight variation in my measurement are negligable and have no affect on the consistency, repeatability and accuracy of my loads.

I am measuring to ogive. I mentioned that, and I stated that I was using a comparator.

 

[richardca99]

I'm not a BR shooter...just a reloader who enjoys seeing the fruits of my labor on paper. I have a rifle that will cut one neat hole if I do my part, and I use it to experiment with technique -- it's my "control," as I know it'll shoot the same way every time.

Thanks. I was afraid that there wasn't much I could do other than measure each round. Fortunately, I'm not a high volume shooter.

 

[Old Navy]

Make sure the primers are fully seated. Later! Frank

 

[wapiti25]

One thing I thought of if using high BC bullets some times the tip of the bullet touches first in the seating plunger. Make sure that the bullet is touching on the ogive and not the tip, I had heard that Redding has plungers for the VLD bullets that are drilled deeper.

 

[Joe O]

I believe the answer has been pointed out.solution is 1.sort bullets by ogive.I found match bullets over .015 difference.
2.Using VLD bullets insure the seating stem is not contacting the tip of the bullet(drill deaper if necessary,and keep cavity clean) 3.Insure bullets aren't being pushed out by air pressure in the case(may need more neck tension).4,High primer could give false reading.The seating stem usually contacts the bullet a good ways above the ogive,so premeasured by ogive is not an absolute to OAL or COAL.Keeps the custom bullet makers in bussiness.LOL

 

[1holeaddict]

three possibilities here, if you are mesuring to the ojive as indicated

The brass can be the problem as it will often spring back on the shoulder/neck area after seating causes it to collapse slightly at that area - so the brass is the "problem" -- anneal

2nd i have seen situations where the necks have been turned and there is low neck tension - that the air pressure compressed inside the case, on bullet seating will push the bullet out a few thousands - this is most more often the case when there is not a "full" case of powder or with stick powder - allowing more air inside the case.

3rd, the pressure you use "bumping" the ram when seating can easily cause the length to vary as much as you are seeing. it is very difficult to be exact in each stroke of the press and .001-2 is not out of reason to expect.

bob

A+ on # 3

 

[Martin52]

I have been trying to minimise the variance in seating depth and have recently made some progress after using a new comparator (yes.....something else to buy, but in my view. this one is a good investment).

For background, I have a Forster BR seater die and a Wilson inline seater both with micrometer tops.

Whichever seater I use, the results are typically the same, a variance of 0.001 - 0.003 across the seated projectiles. I use both Sierra's 2156 and the Berger FB 155.5 grainer.

I recently bought one of Bob Greens comparators (www.greensrifles.com). This tool measures the distance between the point on the bullet nose where the seater stem makes contact, to the point on the bullet that contacts the leade/lands of the barrel using a tenth (.0001”) indicator.

This distance will vary from projectile to projectile and I think is the distance that German Salazar said in one of his excellent articles was an important measurement (but uncertain how it could be measured at that time). The article is "Measuring Bullets" (9/24/10) www.riflemansjournal.com

I now batch my projectiles based on the comparator measurement and load for each string using projectiles that have the same comparator measurement.

Whilst I have not eliminated the seating depth variance, I have reduced it but I have been more surprised how my groups have tightened up after reloading with projectiles sorted by comparator measurement.


Martin

 

[richardca99]

Bingo. I read the same article by German Salazar yesterday, and that cleared it up. I do agree that pressure on the ram can contribute to variance as well.

The variance that we care about is the variance in the distance from the SEATING PLUG contact point to the COMPARATOR contact point (ogive theoretically). Salazar says that measuring base-to-ogive, base-to-tip, or any other dimension isn't going to tell you squat about this measurement. You'd have to measure seating-plug-contact-point-to-ogive on every bullet, and there isn't a tool to do this. But, apparentlly there is now.

http://riflemansjournal.blogspot.com/2010/09/reloading-measuring-bullets.html

 

[richardca99]

I have been trying to minimise the variance in seating depth and have recently made some progress after using a new comparator (yes.....something else to buy, but in my view. this one is a good investment).

For background, I have a Forster BR seater die and a Wilson inline seater both with micrometer tops.

Whichever seater I use, the results are typically the same, a variance of 0.001 - 0.003 across the seated projectiles. I use both Sierra's 2156 and the Berger FB 155.5 grainer.

I recently bought one of Bob Greens comparators (www.greensrifles.com). This tool measures the distance between the point on the bullet nose where the seater stem makes contact, to the point on the bullet that contacts the leade/lands of the barrel using a tenth (.0001”) indicator.

This distance will vary from projectile to projectile and I think is the distance that German Salazar said in one of his excellent articles was an important measurement (but uncertain how it could be measured at that time). The article is "Measuring Bullets" (9/24/10) www.riflemansjournal.com

I now batch my projectiles based on the comparator measurement and load for each string using projectiles that have the same comparator measurement.

Whilst I have not eliminated the seating depth variance, I have reduced it but I have been more surprised how my groups have tightened up after reloading with projectiles sorted by comparator measurement.


Martin

Martin, I'm intrigued by the BGC tool. How do you account for the fact that every seating stem/plug varies by manufacturer? Or, does this thing just give you one more tool to sort bullets by consistency? Have you seen a marked difference in sorting by this spec alone?

 

[Martin52]

[/quote]

Martin, I'm intrigued by the BGC tool. How do you account for the fact that every seating stem/plug varies by manufacturer? Or, does this thing just give you one more tool to sort bullets by consistency? Have you seen a marked difference in sorting by this spec alone?
[/quote]

Good question and yes, I agree, seating stems do vary when compared to each other.

Furthermore, there will be a variance in whatever stem is used and the stem in the Green comparator.

My Forster stem is different to my Wilson stem and both are different to the Green stem.

However, it is the variance described above that the Green comparator measures, this is independant of whether you're using for example a Redding, a Forster or a Wilson stem.

I find the Green comparator demonstrates that my Sierra's vary by approximately 0.004/5 and I batch the projectiles accordingly. Whilst this has helped reduce seating variance, the most noticeable and more important effect has been on the target.

I would say that I have seen a marked difference sorting this way compared to other methods of sorting projectiles.