Interesting bullet sorting conundrum

[Ghengisahn175]

Gentlemen,

I have a bit of a problem with bullet sorting my 220gr SMK's. Heres the backstory:

I received a mixed lot of 220gr SMK's (which have tangent ogives--unsure if its relevant at this time) and I am unsure how I should go about sorting them. I have tried several methods ALL with great consistency. They are :

1. Erik Cortina's method via bob green or seating long method: to sort bullets where the seating stem makes contact with the bullet on the ogive.

2. bryan litz' method: This would be sorting based on bullet base to ogive (using a hornady comparator for this).

3. bullet base to tip method

I know everyone has their opinion with sorting bullets this way (and I am not advocating one method or another) but the where I'm having the problem is where each bullet touches the lands. No matter how I sort these bullets, they all come into contact with the lands at different lengths.
I'm using the hornady OAL gauge and I can get the same bullet with readings that vary +/- 5 thousands (depending on force i input with my hands and fingers). However, these differences are overshadowed by the huge margin that each bullet makes into contact with the lands.

For example:

bullet A: reaches the lands at 3.865"
bullet B: reaches lands at 3.880"
bullet C: reaches lands at 3.890"
bullet D: reaches lands at 3.900"
bullet E: reaches lands at 3910"

To be fair, I am rounding to the nearest hundredth but it was very close measurements (other than bullet A, the measurements were at most 2 thousdanths off from the nearest whole hundreth). And again, all these bullets measured the same via any method of measurement for bullet sorting.

I suppose my problem here is two fold: If I go with either end of the spectrum, I'll either have them all jumping and reaching the lands at different points OR I'll have some jump and some jammed into the lands. I'm not exactly sure how I should be sorting my bullets now other than weight at this point or I can painstakingly sort bullets by touching each one to the lands.

Anyone have any suggestions?

 

[Ghengisahn175]

Dmoran,

I think you're misunderstanding the issue but I acknowledge I may have written it confusingly.

I mentioned that the only variation I have at this time is my measurements to the lands with the hornady OAL gauge between several bullets.

HOWEVER when I measure by base to ogive, bullet OAL, and seating die test they all are very consistent and close to each other.

I find this odd because with any bullet sorting method the end result is that the carteisges themselves as a whole will be consistent but when the cartridge is in the chamber and they're fired, they'll all have different jump times to the lands and in the worst case scenario I believe them to be jumping only to have them jammed inside creating a pressure spike.

 

[spclark]

What disciplines do you intend to use these bullets for?

By that I mean what kind of competition (F-TR comes to mind with that weight) or maybe hunting?

(I had a whole other response written out then read your reply to dmoran & deleted it.)

So your 220 SMK's gauge BTO to your satisfaction, it's the difficulty getting any consistency using several bullets to determine just where it is they first encounter the lands?

Use just one bullet out of a given batch. Use that one consistently to monitor land contact changes as your chamber wears. When measuring land contact try to be as consistent as possible with your seating technique (diddling with the spring wire on the Hornady tool) time after time. Measure several times (I use ten unless pressed for time or they don't change after four or five more than 0.001") then discard the two outliers at either end & average the rest.

Bullets are mass-produced products that will vary slightly in dimensions. You can buy monolithic, CNC-machine bullets now that won't show as much variation, but you'll pay DEARLY for the consistency.

Anther trick is to use a brass rod (mine's 3/16" diameter) inserted into the muzzle so that you can work the bullet into the lands multiple times by pushing first on the rod then on the spring wire in the Hornady tool. This will help you "feel" where first land contact actually occurs.

 

[Ghengisahn175]

Spclark,

These are just bullets to use for training instead of using more expensive Berger
Bullets.

The problem I'll have with the suggestion of use 1 bullet
In the batch is if I load close to the lands (in my case even a 30 thousandth jump) I can still have some that are touching or slightly jammed into the lands.

Not only will it throw off load development but also down range results.

With bergers or hornady AMAX I can measure several bullets in s bunch and they'll all be very consistent with measurement to the lands, just not these so I'm not sure how to go about this issue.

 

[Sheldon N]

So are the differences you're describing what you see when you are measuring your chamber/rifling with the Hornady OAL tool with the plunger?

Ie., you get consistent measurements from one bullet when you repeatedly test it over and over again? Then you get consistent measurements from a different bullet, when you repeatedly measure its depth to the lands, but those measurements aren't the same as the first bullet?

I found that the primary variability I experienced had to do with the pressure I exerted when seating the bullet with the OAL tool. This variability was far more than any difference between bullets - I'd actually be hard pressed to quantify the difference between bullets without comparing an average of 5 or 10 measurements.

When I measured my chamber, I grabbed several bullets at random, did multiple readings of each (using the brass rod trick to feel when the bullet contacted the lands), then averaged the whole lot. I measured cartidge base to ogive using a Hornady comparator. If you are measuring bullet/cartridge OAL to the tip then that's why you are seeing so much variability. Bullet length to tip was much more variable than ogive, in my measurements.

If there's wild variability in the shape of the bullet such that you are seeing swings of 0.03 in ogive measurements between bullets, something isn't right. When I seat my rounds I am consistent down to 0.001 in cartridge base to ogive measurement and I measure every loaded round.

 

[DT]

Sounds like it could be an issue with the seater plug being a mismatch for the bullet shape.

 

[Ghengisahn175]

For clarification,

The bob green sorting method would be sorting by where the seater stem makes contact with the bullet. Therefore when you seat the bullet into the case, you'll end up with consistent measurements when measuring the final cartridge. The way to check this would be seat a bullet long, measure with a bullet comparator and seat to the desired depth from there.
Again, across the bullets no more than a thousandth or two variation

For the base to ogive method that's just checking the bullets themselves with a comparator and sorting them that way. I sort the piles by 2 thousandths variation here.

For Bullet OAL that's just measuring with calipers from base to meplat. (I don't sort bullets this way but the reason below is why I checked it anyways )

The issue again comes with the measurement to the lands. No matter which method of bullet sorting I do above, when I check several bullets to get a general idea of how much to jump to the lands, I'm getting huge variations.
I'm using the straight gauge not te curved. I understand and said that the amount of pressure appllied will effect the readings.
I also said that I checked the same bullet several times and am normally within a few thousandths per measurement so I can round that # up to the nearest whole #.

This is where I was saying that bullet A averaged 3.000, bullet b averaged 3.020, etc.
where I'm confused is if I sorted the bullets in any way, does that still not matter in determining your jump?

With another type of bullet (hornady AMAX) I grab several bullets from the pile and when I measure them to the lands I'm getting the exact same fee thousandth variations (based on amount of pressure applied) but they're very much the same numbers across several bullets, therefore I can apply the same seat depth to all of them for the same amount of jump to the lands.

With the SMK's I have I cannot. This is where I am confused about

 

[calgarycanada]

IMHO base to ogive is the best method because that's where the bullet makes contact with the rifling. If you have lots sorted that way and your bullet seater's seating stem matches the shape of the bullet your jump or jam should be within 5 thou from each other. If seating stem does not match the bullet shape, you can send it back to manufacturer and have them reshape it for you(I know Forster offers that service not sure about others). As German Salazar mentioned in his blog don't shoot just touching, either jump 8 thou or more or jam 8 thou or more, that way you eliminate possibility of some jumping and others touching etc. I hope this helps

 

[Sheldon N]

If your comparator tool hits the ogive in a different place than the rifling (ie different diameter), that could be a cause for variation in the measurements. You'd be measuring the variability in the angle/slope of the nose of the bullet, resulting in differential measurements from the comparator contact point to the lands contact point.

If your seating die contact point matches your rifling then the resulting seating depth would be consistent for the bullet to lands contact, even if the comparator tool says otherwise.

The advice to either jump all the way or jam all the way sounds like a good approach.

Not much else you can do to fix bullet to bullet shape variations, other than test seating depths and see what shoots well. If things work well in practice, then I'd not worry about what variations the comparator shows.

 

[Brians356]

I'm using the hornady OAL gauge and I can get the same bullet with readings that vary +/- 5 thousands (depending on force i input with my hands and fingers).

That statement stopped me abruptly. If you can't repeatedly measure the base-to-ogive of a single bullet (did I misunderstand you?) using the Hornady comparator, to less than .001", I don't see how you are going to proceed with this witch hunt. You simply must have a repeatable method of measuring off the ogive, to within a reasonable tolerance. It's hard to imagine the comparator can settle at such widely disparate places on the ogive, even a fairly long tapered one.

What kind of indicator are you using with the Hornady rig?

If I misunderstood you, it does still serve to illustrate the need to work up from basics: You need to be able to get repeatable comparator measurements of just a single bullet (forget about the chamber, lands, seated bullet, etc. for the moment) just to prove you have a reliable measurement tool and technique, and that the bullet ogive can be reliably measured (i.e. comparator settles repeatedly at the same diameter, within a reasonable tolerance.)

 

[Ghengisahn175]

Brian,

when I mentioned all my measurements in relation to the bullet alone, my measurements are exact and repeatable. When I measure base to ogive, my tools are a mitutoyo calipers, hornady bullet comparator (one for base to ogive and two for bearing surface). all these measurements are exact.

The only one where I get +/- 5 thousandths variance (and thats at worst) is my measurements to the lands with the OAL gauge and obviously thats from applied pressure with fingers. I gave myself leeway when posting that but I'm almost always getting several measurements exact but I input in due to human error.


I called Sierra today and the best they could tell me at the moment was that it could be an obstruction in the bore or a carbon ring thats throwing off my lands measurements from bullet to bullet. I scrubbed and cleaned out my barrel but im still getting these huge variances from bullet to bullet. I'm literally at a loss and don't know why I cant find consistent measurements to the lands from bullet to bullet.

 

[hogpatrol]

Are you using a Hornady manufactured case or one that was shot in your rifle and modified? What's your chamber neck diameter? Whats the o.d. of the modded case? What is the length? Maybe the case neck is hanging up somewhere.

 

[Ghengisahn175]

I am using the hornady modified cases they made and one not fireformed

But when I measure bergers or hornady bullets I don't get this huge variation, if any.
As I stated this is a mixed lot of Sierra bullets but I didn't think I'd get upwards of 60 thousandths + variations.

 

[hogpatrol]

In that case, ditch the Sierras and stick with the Bergers & Hornadys.

 

[Ghengisahn175]

In that case, ditch the Sierras and stick with the Bergers & Hornadys.

Shit I'm about to if I can't figure this out. Never buying mixed lots again

 

[lrgoodger]

That's the exact reason I quit buying Sierras. Never mind cartridge measurements. Just measuring the bullets from a box of 500 resulted in five distinct lots of bullets. Bullet lengths within each lot were quite consistent, but it was obvious that five different lots of bullets had been dumped into that box of 500.

 

[Brians356]

The only one where I get +/- 5 thousandths variance (and thats at worst) is my measurements to the lands with the OAL gauge and obviously thats from applied pressure with fingers. I gave myself leeway when posting that but I'm almost always getting several measurements exact but I input in due to human error.

Ok, got that.

Now (and this is important): When you use the Hornady "OAL" [sic] gauge to push a bullet to the lands, lock it, and measure using the comparator, are you getting up to 0.005" variance for the same bullet, retested several times?

 

[Sheldon N]

Now (and this is important): When you use the Hornady "OAL" [sic] gauge to push a bullet to the lands, lock it, and measure using the comparator, are you getting up to 0.005" variance for the same bullet, retested several times?

I get that kind of variation when I use the Hornady OAL tool. It's incredibly hard to be precise to the thousandth, because the depth of how far the bullet goes into the rifling is entirely dependent on how much pressure you apply when pushing in the bullet. If I use the brass rod/dowel trick I can reduce the variation a bit, but it's still not perfect. Hence the reason why you take multiple readings and average them.

 

[Brians356]

Now (and this is important): When you use the Hornady "OAL" [sic] gauge to push a bullet to the lands, lock it, and measure using the comparator, are you getting up to 0.005" variance for the same bullet, retested several times?

I get that kind of variation when I use the Hornady OAL tool. It's incredibly hard to be precise to the thousandth, because the depth of how far the bullet goes into the rifling is entirely dependent on how much pressure you apply when pushing in the bullet. If I use the brass rod/dowel trick I can reduce the variation a bit, but it's still not perfect. Hence the reason why you take multiple readings and average them.

Yep, it's tough, especially with bullets w/ long ogives. But what I do is measure one bullet up to 10 times, trying hard to use the same pressure, and if out of 10 samples, I get the same figure repeated several times, like maybe 6 out of 10 I get the same figure to the .001" tolerance, then I will use that figure. If I were to measure 10 times and got 10 different figures, that would be untenable, but normally I can repeat the same figure often enough to settle on that one.

The consistent technique is not limited to pressure on the bullet, it's also important to avoid moving the stem while locking the set screw. I try to gently snug down the set screw while maintaining the position of the stem, then tighten it more after that initial snugging down.

One thing I did to mine was round off and polish the end of the set screw, so it won't want to gouge up the inside of the aluminum stem channel. And I also smoothed out any gouges which might have been already produced. If there are gouges or bumpiness in the stem channel, when you tighten the set screw it can tend to slip off the top of any slight ridge it's contacting, likely moving the stem slightly.. One shouldn't use too much force when tightening the screw, anyway, since the stem is aluminum. Just enough to make sure it won't budge when taking the caliper measurement. No need to mash the stem unnecessarily.

 

[Martin52]

A quick comment, not wanting to hijack the thread - the Lee Collet die can be adjusted to re-size the neck just enough to hold a bullet. Seat it long in an unprimed case, then chamber, extract gently and measure with your comparator. This might assist get your variance reduced.

Martin