Bullet Lot variability question

[Zatoichi66]

I realize consistency is the key to precision shooting, and so, buying reloading components by similar lot # is desirable, but our current situation of being limited to 200 projectiles, 100 cases, etc at various online stores means mixed lots of components. I have 3 different lots of Hornady 140 gr OTM 6.5mm and don’t know what to expect regarding precision. I suspect my abilities will be a bigger issue, but all things equal—how much variability can be experienced in practical precision shooting?

can the more experienced reloaders comment on how much lot to lot variability a shooter can experience? Will one see 0.5 MOA between Berger & Hornady OTM? 1 MOA?

or, like reloads in a self defense shooting debate, is lot to lot variability more theoretical than actual/practical?

 

[918v]

No it’s not theoretical. It’s real.

 

[Zatoichi66]

How much in MOA?

 

[918v]

Say your gun is capable of .25 MOA and you work up a .25 MOA load. Then you run out of bullets and you open a different lot. Your groups may triple or more in size. You’ll have to fine tune the load again.

This becomes a pain in the ass if you buy powder by the pound and primers and bullets by the hundred.

 

[hafejd30]

I’ll tell you this from my experience,

Don’t switch brands and expect the same level of precision without load development.

If you’re running say hornady 140 eldm and switch lots. It helps to measure the OAL with the new bullet in reference to the cartridge base to ogive. I’ve seen lots of hornady bullets be a decent amount off from their similar projectiles. But if you run the the same distance off the lands between lots they generally run good

Ex: if your current lot is shooting great .020” off the lands then measure and seat the new lot .020” off the lands for best results

 

[Steel head]

Buy in bulk if you can.
I try to buy enough powder and bullets to kill a barrel.

I’ve seen more times than not that new lots of bullets do just fine, especially if they are Berger or other premium bullets.
But I have gotten bullets that changed thing enough that I had to tune up the load a bit.
Hello Hornandy

Powder can and does vary.
My current lot of H4530 is a speed demon compared to all the other lots of H4350 I’ve had.

 

[Zatoichi66]

So what are you more experienced reloaders/shooters doing in this market?

midway only sells 200 bullets per shot—how do you maintain consistency?

weigh?
OAL?
Tip the projectile?
All the above?

inquiring minds was to know!

 

[spife7980]

So what are you more experienced reloaders/shooters doing in this market?

We bought in lots of 2k before it started.

When I get a new barrel I also get enough of a bullet to shoot it out.

 

[j-dubya]

So what are you more experienced reloaders/shooters doing in this market?

midway only sells 200 bullets per shot—how do you maintain consistency?

weigh?
OAL?
Tip the projectile?
All the above?

inquiring minds was to know!

While it is wisest to buy a single lot to last the life of the barrel, a 308 barrel for example, would be a significant investment in both purchase and storage... For my 762 gas gun, primarily running Sierra 175’s, I would still buy in ~2k quantities as I could afford to (pre-panic). Over the years of shooting these Sierras, I’ve found that while their base to office differences are vast, I can usually put them into three columns. Even when buying from Powder Valley and requesting same lot, even within that, Sierras will vary. Yet they still seem to follow that three-length pattern where they land somewhere around those three point +/- ~.003”...

Interestingly enough, even when getting new lots that measure out the same for my base to ogive categories, their OAL length loaded will be 2.805ish for one lot and 2.820+ for another lot. This is still with maintaining identical seating depth with identical base to ogive measurements. Something to consider if you load long or use pmags for a gas gun..

 

[Zatoichi66]

Will keep in mind if anyone sells more than 200 at a time. That’s actually something I didn’t immediately think of & will in the future

 

[Zatoichi66]

This is a Tikka 6.5CM.

 

[918v]

Find a coal range that produces accuracy and maintain it. Chasing the .020” off the lands thing is not going to work. The lands erode with every shot.

I don’t subscribe to to the prevailing theory that says maintaining a fixed amount of jump to the lands will maintain accuracy. What does work is finding a coal range and sticking to it.

Say you find that 2.810” +\- works for Box of Bullets Lot A. Take one of the bullets and keep it as a reference for throat erosion and for bullet shank centerline dimension. If the old bullet has a .400” long shank but the new bullet is only .380”, set the new coal so that the shank centerline on the new bullet is in the same spot as the old bullet. That way you preserve the same bullet time in the barrel. You will probably have to tweak the coal a small bit, but you won’t be wasting most of the box trying to figure it out.

 

[spife7980]

I don’t subscribe to to the prevailing theory that says maintaining a fixed amount of jump to the lands will maintain accuracy. What does work is finding a coal range and sticking to it.

I dont either. When I start testing I try to start at .020 off the lands but from then on I let testing tell me what to do. In most cases I have found that even as the lands erode that once Ive found that golden depth I rarely have to chase them much to stay in tune, certainly less that the amount of erosion it seems.

Each time I load up the cases for another cycle I do a quick little test to see if longer or shorter or a tenth or two more or less powder show any improvement. They rarely do after that initial stable load is found so there really isnt much deviation required. But its a nice little confidence inducing exercise to make sure my match ammo is as good as I know it can be for the next few hundred rounds.

The new 6 creed barrel I have with the 112 barnes mb I could find in bulk wont even let me find the lands to touch off of. I just went to the old rule of thumb that once cabiler depth into the case neck and Ive had some promising results on the initial ocw. So thats jumping them like .24x"+... Im loading up a depth test now in .1 increments sort of like how the prb article was talking about. Ive never not been able to touch the lands before so Im intrigued to test this waaay off and "stable" theory.

 

[Zatoichi66]

Is COAL or meplat more accurate? Most of my OTM—even Bergers—are crooked. But most reloading goes by COAL.

confusing, it is.....

 

[918v]

Coal is a plus minus thing. Within a box of bullets you might see a .015” length variance. So in my prior example some of your rounds would be 2.803” and some 2.817” but the middle would be 2.810”.

The important thing, though, is the bullet shank and where it sits in relation to the muzzle because it’s all about barrel time.

 

[Zatoichi66]

Is “pointing” or whatever the lingo is to try to standardize OTMs worthwhile?
Precision Rifle Blog suggested no, but I see the irregular OTM effecting COAL with the batch I’m loading.

I was going to file a tad to made the OTM squared, but then was concerned about screwing the bullet weight.

this stuff is killing my OCD!

 

[spife7980]

Is “pointing” or whatever the lingo is to try to standardize OTMs worthwhile?
Precision Rifle Blog suggested no, but I see the irregular OTM effecting COAL with the batch I’m loading.

I was going to file a tad to made the OTM squared, but then was concerned about screwing the bullet weight.

this stuff is killing my OCD!

Thats why we measure down low on the ogive, close to where the bearing surface of the bullet would actually be touching the barrel. Its much more consistent.

 

[Zatoichi66]

Doh! I used the wrong term—ojive, not
Meplat. Bad Zatoichi66!

I respectfully request demotion back to Private vs my current “Sergeant” status—haha!

I have one of the Hornady Comparetors like you show, but other than my own measurements, I don’t see most reloading manuals listing this measurement.

 

[918v]

I don’t bother with the ogjive when seating. I use the micrometer on my seater die to make adjustments and check the coal to see if I’m in range.

 

[spife7980]

Doh! I used the wrong term—ojive, not
Meplat. Bad Zatoichi66!

I respectfully request demotion back to Private vs my current “Sergeant” status—haha!

I have one of the Hornady Comparetors like you show, but other than my own measurements, I don’t see most reloading manuals listing this measurement.

Thats because they lump their bullets together by weight and to the minimum dimension to ensure it works in everything with a saami chamber. If they had to divide it up even more based on other geometry you would have the biggest book in the world with a page devoted to each bullet for each chambering etc.

Books are a rough guide by lawyers, not a matter of fact.

 

[Zatoichi66]

Got it—Thank you!

 

[Raffy]

I have one of the Hornady Comparetors like you show, but other than my own measurements, I don’t see most reloading manuals listing this measurement.

I dont understand why the ogive measurement is not communicated more often in books and load data measurements. It seems to be the most consistent interaction with the bullet to the barrel. I dont think the barrel cares where your meplat is. Just as long as it fits and feeds properly in your magazine and you can extract a live round when needed, its a moot point.

 

[spife7980]

Got it—Thank you!

And in relation to my last comment about lawyers, when you do switch lots watch out for these signs just to be safe https://www.primalrights.com/library/articles/understanding-pressure

 

[918v]

I dont understand why the ogive measurement is not communicated more often in books and load data measurements. It seems to be the most consistent interaction with the bullet to the barrel. I dont think the barrel cares where your meplat is. Just as long as it fits and feeds properly in your magazine and you can extract a live round when needed, its a moot point.

The ogjive varies from lot to lot just like average bullet length. I have seen more than 60 thou BTO difference between different lots of the same bullet. Since load data has to fall within saami specs ogjive measurements would be meaningless.

 

[Raffy]

I dont think load data has to fall to a saami spec measurement that an individual works up for his own rifle. Especially if there is a custom reamer with a custom barrel

 

[918v]

Load data has to fall within saami specs if you intend to publish and sell it.

 

[Raffy]

But not if your going to roll your own and shoot it. Thats all im saying. Its not a one size fits all process if you know how to do it safely. Thats where a lot of saami spec'd cartridges came from. Wildcats that became popular enough to standardize

 

[918v]

Why would a bullet manufacturer publish the bto if it varies from lot to lot and cannot be measured consistently with the tools available to us handloaders?

 

[Raffy]

The total length of each projectile varies from bullet to bullet in the same lot. What is more important?

 

[Raffy]

It seems to me that the reason that coal is published is because of magazine length restrictions. Accuracy of a cartridge with a given projectile is not dictated by how well it fits in the magazine. The magazine length is simply a restriction that we have to work around and deal with sometimes.

 

[918v]

The reason coal is published is to show that the data falls within saami specs.

 

[918v]

The total length of each projectile varies from bullet to bullet in the same lot. What is more important?

The coal is more important. And it can be measured with absolute certainty using cheap instruments.

 

[Raffy]

Ok. Sure, why not

 

[Raffy]

Coal is a plus minus thing. Within a box of bullets you might see a .015” length variance. So in my prior example some of your rounds would be 2.803” and some 2.817” but the middle would be 2.810”.

The important thing, though, is the bullet shank and where it sits in relation to the muzzle because it’s all about barrel time.

If the most important factor is bullet shank due to barrel time, then with each round how do you anticipate consistent barrel time it your seating off of the meplat measurement rather than CBTO. Are you adjusting your dies with every seated round to get consistent shank depth in the case? How long does it take you to seat your bullets? That would take forever

 

[spife7980]

If the most important factor is bullet shank due to barrel time, then with each round how do you anticipate consistent barrel time it your seating off of the meplat measurement rather than CBTO. Are you adjusting your dies with every seated round to get consistent shank depth in the case? How long does it take you to seat your bullets? That would take forever

Cmon dude, read what hes written.

Youre the one thats looking crazy here

 

[Raffy]

No its a serious question. Ive been trying to say that cbto is how its done and thats how I do it. If there is another way that works for someone else I want to understand it. At first I was argumentative but then went back through the thread and saw what he wrote and thought maybe were both saying similar things in a different way. Maybe he has something weird that I haven't heard of before that works. What is with the bullet shank method?

 

[918v]

You’re looking at it the wrong way. Earlier you asked why load data doesn’t include bto info. I tried to explain it to you but you aren’t getting it.

Whenever a business deals with inherently dangerous stuff, they have to take steps to mitigate liability should something go wrong otherwise no one will insure them and they certainly will not put their personal assets on the line.

Load data publishers have to stay within saami specs otherwise they will be negligent. Saami does not publish ogjive specs. That is why factory chambers have long freebores.

If load data publishers included ogjive info it would cause havoc in the industry because people would specify short freebores in their chambers under the stupid belief that shorter jumps are more conducive to accuracy. Then people would take those numbers as gospel and jam their bullets into the rifling thinking they’re actually off the rifling. Here is why:

A comparator does not measure anything. It compares one bullet to another or one loaded round to another. You cannot infer jump length from a comparator reading. You can take two bullets with identical BTO readings per your comparator and they will have completely different jump length numbers. Even from the same manufacturer but different lots. And then there are differences in comparators from one brand to the next. They all hit the ogjive in a different spot.

Can you imagine the clusterfuck this would cause???

 

[Raffy]

Thanks for the reply. Yeah from a legal perspective that makes total sense, especially for companies publishing data. I meant from pet loads and stuff with people who know where their lands are so they know how to not blow up using a good seating depth for someone else's load after working up powder charges.

It seems like bullet A from a given manufacturer tends to like the sameish thing from rifle to rifle. Others could benefit from it. Have you read about the testing done by Mark at Short Action Customs about seating depth?

 

[918v]

About finding a spot far away from the lands and staying there till the barrel is toast?

 

[Raffy]

Yeah basically. The short version is that some bullets prefer a seating depth in the case rather than a specific jump to the lands, and that accuracy was tested to be consistent regardless of freebore length.

 

[zeroverfied]

I’ll tell you this from my experience,

Don’t switch brands and expect the same level of precision without load development.

If you’re running say hornady 140 eldm and switch lots. It helps to measure the OAL with the new bullet in reference to the cartridge base to ogive. I’ve seen lots of hornady bullets be a decent amount off from their similar projectiles. But if you run the the same distance off the lands between lots they generally run good

Ex: if your current lot is shooting great .020” off the lands then measure and seat the new lot .020” off the lands for best results

Can you measure the deviation from 140 eldm old to 140 eldm new? What would the difference be?

 

[hafejd30]

Can you measure the deviation from 140 eldm old to 140 eldm new? What would the difference be?

I used that as an example 2 years ago. But yes you can measure it. I can’t as I don’t have the same bullets. You need to measure difference lot to lot on YOUR bullets. Not the same across the board.

I’ve seen hornady bullets off .017” in base to Ogive measurements in a single box of 100 bullets

You joined 22 minutes ago. Spend some time reading to understand what you’re asking

 

[zeroverfied]

Thank you good data. Appreciate it. I think simple, like a lot to lot variation, it's amazing to have a lot in lot variation. Thank you again!!!

 

[FCS]

Can you measure the deviation from 140 eldm old to 140 eldm new? What would the difference be?

Last post was nearly two years ago.

I’ve seen as much as 0.035” difference in ogive length, bearing surface length between two different lot #s of the same brand of bullet.
Really should check each lot # for OAL to touch lands and then make needed adjustment for same jump. One might need to do a small tweak on powder charge to keep everything same same provided all other components are same lot#.

How far down rabbit hole do you want to go?

 

[zeroverfied]

Brother, you stopped me in my tracks. I am old school FA gunnery instructor. You are never too old to learn. Loving science and
art!!!

 

[OkieMike]

Ammunition/Reloading is a study in tolerance stacking.

I don't know the entire process of how bullets are manufactured, but I was a machinist for 10 years, so I bet I have a general idea...

It's going to involve lots of equipment with lots of tooling...

Every spindle/station is going to have a small amount of variance...

Every die in those spindles/stations is going to have a small amount of variance...

Every setup of those machines is going to involve minor differences from the last run...

When dies wear out and get replaced, the new dies will vary a bit from the old. The alloy the dies are made of will vary... And they'll wear differently

Every lot of raw materials will vary slightly in the alloying...

Different operators will run the equipment differently... Some will say, "It's within spec, run it!" Others will try to run a little closer to nominal dimensions. You may have the Monday morning/Friday afternoon syndrome coming into play.

About the only way to get bullets that are (nearly) "perfectly" consistent is with lathe turned solids... And that's not even perfect. And that level of consistency is expensive.

In the end, you just have to decide what you want to do and do it to the best of your ability with what you have on hand... Or what you can spend.

Final note: I will say certain bullet manufacturers do a hell of a lot better job controlling variance than others.

Mike

 

[zeroverfied]

Ammunition/Reloading is a study in tolerance stacking.

I don't know the entire process of how bullets are manufactured, but I was a machinist for 10 years, so I bet I have a general idea...

It's going to involve lots of equipment with lots of tooling...

Every spindle/station is going to have a small amount of variance...

Every die in those spindles/stations is going to have a small amount of variance...

Every setup of those machines is going to involve minor differences from the last run...

When dies wear out and get replaced, the new dies will vary a bit from the old. The alloy the dies are made of will vary... And they'll wear differently

Every lot of raw materials will vary slightly in the alloying...

Different operators will run the equipment differently... Some will say, "It's within spec, run it!" Others will try to run a little closer to nominal dimensions. You may have the Monday morning/Friday afternoon syndrome coming into play.

About the only way to get bullets that are (nearly) "perfectly" consistent is with lathe turned solids... And that's not even perfect. And that level of consistency is expensive.

In the end, you just have to decide what you want to do and do it to the best of your ability with what you have on hand... Or what you can spend.

Final note: I will say certain bullet manufacturers do a hell of a lot better job controlling variance than others.

Mike

Great Response thanks OkieMike!!!