223 or 5.56??

[Semper Fi 1970]

Hi guys,
Have been doing a little cursory research on .223 Remingtons and 5.56mm. What I have found so far is that they are basically the same with a few variations where the 5.56 is concerned. My question to anyone with the knowledge is;
Do they make 5.56 mm reloading dies or will 223 Remington will work and not cause any chambering or loading problems?

Thx,

Semper Fi 1970

 

[JeepHammer]

External case dimensions are exactly the same.
Sizing dies don't care if you are loading for .223 weights/pressures or 5.56 weights/pressures.
Bullet seating depth will be the difference, along with the powder/pressure.

The line between civilian .223 Rem & 5.56 military are so blurred you have to have a MUCH older rifle to even care.
Older .223 Rem chambered rifles have slower twist rate barrels, they shoot much lighter bullets well but usually have shorter chambers, long/heavy bullets seated long often don't shoot very well.

While MANY disagree, I strongly suggest you get a couple different case gauges.
While cases fired through the same rifle over & over *Might* resize correctly, any ammo made for more than ONE SINGLE chamber must be SAAMI (or NATO) specifications, and case length AND profile gauges are the fast way to figure out if you are making brass/ammo that fits different chambers correctly.

 

[Semper Fi 1970]

Thanks JeepHammer. I have a Ruger MPR in 5.56 and appreciate the info. You have reinforced what I had already discovered but its nice to know from someone that knows what they are talking about.

 

[JeepHammer]

The biggest two differences in .223 Rem & 5.56 NATO take a history lesson, they have pretty well merged as the same round now.
I caution older rifle owners about using NATO length/weight bullets, or any long/heavy bullet in the older rifles.

Some of us grew up shooting 35-45 grain .223 Rem, and when the chamber was cut correctly it was 'Inherently Accurate' with 1:16 to 1:12 twist rate barrels.
With a little load development they were absloute tack drivers, varmints didn't stand a chance!

Then along came the military and long, heavy bullets showed up on the surplus market, and 'Issues' happened.
First 50, then 52, and up in bullet weight, which the older, slower twist rates couldn't stablize, and bullets seated so long they plugged chambers.
Instead of soft lead cores and thin jackets, the military surplus had thick jackets and hard lead, or tin core bullets ('Penetrator').

Then suddenly you got bullets made for the military sold as civilian bullets, so even if you reloaded, you might get hard bullets if you weren't very careful.
There is a reason the 'Varmint Grenade' bullets made now do such a wonderful job on varmints and are highly accurate while FMJ is still just FMJ.
It has to do with the jacket/core being able to conform to the bore when the barrel throat sizes it...

I don't think I own a bullet heavier than 60 grains, and I still shoot mostly 50 grain varmint bullets, since I'm not punching holes in targets @ 100 yards when I'm prairie dog hunting @ 200-300 yards, and the target is the size of your fist.
Amazing how long the bore will last when you aren't stuffing a big, hard, overpressure chunk of metal into it, for it to size under tremendous pressure...

 

[T.Lex]

Amazing how long the bore will last when you aren't stuffing a big, hard, overpressure chunk of metal into it, for it to size under tremendous pressure...

TWSS

 

[natdscott]

I take little issue with your opinions of heavy .224 bullets in 5.56/.223 Remington cases, because hey, to each their own. Although, given that his rifle is an 8" twist with a 5.56 chamber, it seems likely that lighter bullets will not fare as well for him as heavier/longer ones.

That said, this is untrue:

There is a reason the 'Varmint Grenade' bullets made now do such a wonderful job on varmints and are highly accurate while FMJ is still just FMJ.

It has to do with the jacket/core being able to conform to the bore when the barrel throat sizes it...

No, that's not the reason at all. ALL of the conventionally jacketed bullets will 'conform' to the bore quite nicely under 50,000+ psi, regardless of form. This is not a .22LR.

NONE of our bullets, if they had:
core weight inconsistencies,
horrible jacket thickness and concentricity,
heavy cannelures,
open and very inconsistently formed bases,
and/or core voids...

...would shoot well, regardless of weight, copper/lead alloys, etc.

And yet that is what "BALL" 55 grain bullets are. ALL of those things can be present, in various amounts, in a case of ball ammo.

The OPPOSITE of those things--just about diametrically--is how all of our favorite "Match" and "Varmint" and "Target" bullets are constructed, so yeah, they should shoot better.



But it's not because they are heavier or lighter. More on that i a sec.

Amazing how long the bore will last when you aren't stuffing a big, hard, overpressure chunk of metal into it, for it to size under tremendous pressure...

1) It's not 'overpressure' unless you put enough powder behind it to MAKE it overpressure. Same as any other bullets.

2) Barrel life is tied much more closely to bearing surface length and powder temperature than it is to some esoteric lead-core-toughness concept.

Yeah, if you run heavy bullets really hard, it will tear up a throat. I won't argue that at all.

But if it's just a bullet weight issue, then why don't slow-twist/light varmint bullet .220 Swift barrels last longer?

I don't think I own a bullet heavier than 60 grains, and I still shoot mostly 50 grain varmint bullets, since I'm not punching holes in targets @ 100 yards when I'm prairie dog hunting @ 200-300 yards, and the target is the size of your fist.

Your definition of 'big' appears to be anything larger than a 45 grain bullet. I think that is ridiculous, because the 50-52 class flat-base bullets are probably as accurate in BR (the sport) as any other class, and more than most.

For what reason do you think 'big' .224 bullets became popular? It's certainly not for "...punching holes in targets @ 100 yards..."

Now 'bout that 300 yard "fist size target": My X-ring is 2.85 inches. The rifle I use right now...set up for NINETY grain bullets...would clean that 2.85" X-ring with aplomb, even shooting 77's that are jumping almost 1/4". I'd honestly estimate (to myself) that it is shooting well closer to 1" groups out there than it is to 3".

Out to 300 yards,there's not a Pdog on the planet that could live on the difference between your 35's in your rifle and my 77's in mine. Beyond 300, I think you know what would happen in any wind at all.


OP: you're of course free construct a dream .223 rifle as you wish, to shoot what you wish through it. I just think you should know on the front end that heavy-for-class bullets can be as practically accurate as light-for-class, and that the .223 casing has quite enough power to easily run 60-80 grain bullets, should you wish to do so and set up the rifle as such.

-Nate

 

[Hohn]

Great post Nate.

One other thing to highlight is that because light bullets often run so much more powder, at the same peak pressure a light bullet will put more heat into the barrel. It's simply undeniable that 28gr of powder is releasing more heat than 23gr of powder would. About 5gr more, actually.

Powder charge is heat. But so is pressure, because of the higher density increasing thermal conductivity. (heat flux).

Stated differently, the charge weight determines total heat energy. The pressure determines how much of that ends up in your barrel as does the flame temperature. The bearing area of the bullet and its velocity determine how much EXTRA heat from friction is added to the bore. More bearing area also determines how much stress the barrel will incur to obdurate the bullet. Stress is force per unit area, just like pressure. At the same pressure, more area means more force. More bearing area applies more force to the barrel.

Run a high temp (lots of nitroglycerine) double base powder at high pressure and your throat will go pretty fast. Drop the pressure down with a single base powder and the throat lasts much longer. Having a tight-fitting freebore seems like it would really help as it reduces the "torching" effect of blowby gas that leaks around the bullet before the bore is sealed by the obduration.

 

[natdscott]

Thanks, Hohn. I guess I take things too seriously sometimes, but it's a flaw I have to learn to live with at this point.

Run a high temp (lots of nitroglycerine) double base powder at high pressure and your throat will go pretty fast.


Having a tight-fitting freebore seems like it would really help as it reduces the "torching" effect of blowby gas that leaks around the bullet before the bore is sealed by the obduration.

On the first: you betcha it will. I'm looking at 0.0037" average erosion per HUNDRED rounds in my 1,000 yard barrel. That results in a barrel---which is as premium as it gets---lasting roughly HALF of what it would running an otherwise normal diet of 300 and 600 yard loads (as an average for those kinda rounds, think of Mk 262).


On that second comment about free bore, yes, that seems to be the case. Combined with a tight (0.2240") freebore, and having spent the entire life-to-date of the barrel paying VERY close attention to coaxial runout of the loaded rounds, apparently this barrel has had it's lands washed very uniformly. Chrome-moly probably helps as well.

But anyway, the most inexplicable thing to me is that it will still shoot WELL under 1/2 Minute with short-line loads I only "developed" just this year to shoot the Indiana Championships... That's a 77 SMK from an OAL of 2.242" traveling nearly 1/4" before the bearing surface finally reaches the lands...and yet...

Just astonishing groups at 300 and 600 yards.


-Nate

 

[bigedp51]

Hi guys,
Have been doing a little cursory research on .223 Remingtons and 5.56mm. What I have found so far is that they are basically the same with a few variations where the 5.56 is concerned. My question to anyone with the knowledge is;
Do they make 5.56 mm reloading dies or will 223 Remington will work and not cause any chambering or loading problems?

Thx,

Semper Fi 1970

The difference between the .223 and 5.56 is the .223 a decimal designation and the 5.56 is a metric designation.

And the European CIP (their version of the American SAAMI) considers the .223 and 5.56 to be one in the same cartridge.

And the twist rate and throat length varies between the two, example I have a Savage .223 with a 1in9 twist and a throat longer than my AR15 rifles.

So notice the black RCBS die box below on the left, it is marked .223 and 5.56, "BUT" all the dies pictured are for the same cartridge.

 

[Hohn]

Odd that the 77s like less than mag length. Iirc, the black hills mk262 load is also shorter than 2.26”

What’s the CBTO spec for this load with 77s? Do you use the Hornady comparator?

 

[natdscott]

Odd that the 77s like less than mag length. Iirc, the black hills mk262 load is also shorter than 2.26”

What’s the CBTO spec for this load with 77s? Do you use the Hornady comparator?

Nono...that's just this ONE rifle. The other one with the Krieger was always 2.255" and shoots well at that.

It's just "a thing" to find your best charge at 2.255", and then seat that 75 or 77 back further by maybe 0.005-0.010" at a time to 2.235" or so. One of the three or four groups is likely to shrink WAY down.

That's tune.

ETA: No, I am a Sinclair guy. I always thought it was best to buy the product from as close to the original thinker as possible. That certainly warn't always Fred, but it's closer than the globo-companies. Some of it is almost undoubtedly still machined in/around Ft. Wayne also.

 

[Hohn]

I can see that desire to buy from the guy closer to the original idea.

But with Hornady EVERYWHERE it's tough to make that call..

 

[JeepHammer]

Like I wrote, a LOT of people will disagree...

The difference is older or newer rifles, the bore size, the twist rate & the chamber/throat length.
While one guys rants, he's not considering for a second the older rifles shot .223 diameter bullets, while newer rifles shoot .224 diameter bullets.
The bore used to be .218 but has enlarged to accommodate the newer heavier & longer bullets.

Again, it's stuffing an oversize chunk of metal into a bore that's much smaller, the bullet is a cylinder where the bullet contacts the bore and has to be sized.
ANY increase in weight of a cylinder MUST increase length.
What he's calling 'Bearing Surface' starts as oversize metal slug the throat/bore/rifling must size.
(Bearing Surface being short for Load Bearing Surface)...

Now, what the new wave of 'Internet Experts' don't understand, the older rifles have smaller bores, and they have shallower rifling grooves.
There is a much smaller space to stuff all that metal bullet into, so pressures spike trying to stuff all that stupid heavy bullet into the smaller volume of the smaller bore & smaller rifling volume.

This is where the stories about NATO ammunition blowing up .223 chambered ammo comes from.
I was standing 6 feet away when a guy bought a box of 77 grain .224 diameter bullets and stuffed them into a .223 rifle and promptly blew it up.
First round, catastrophic failure. (And I needed clean boxers!)

Now, as to the twist rate, as everyone knows, a slower twist rate shoots lighter bullets just fine.
Since the OP didn't say what rifle, I had to cover the older, lighter bullets shooting well in about everything, while the heavier bullets REQUIRE a faster twist rate to stablize them.
The 77 grain won't shoot worth anything in an older, slower twist rate barrel (if they fit at all seated as long as they have to be).

Overspinning a light weight bullet doesn't hurt a thing, in fact is a patch for bullets that won't stablize any other way.
Under-spin won't stablize, period.

And consider the application discussed...
Here is someone trying to shoot well at 1,000 yards with a .223.
This takes a BUNCH of work and load development.
All the while you can take any of several .30 caliber options off the shelf and do exactly the same thing with little or no extra effort.

This is a disconnect between application & common sense...

The .223 is an EXCELLENT short & medium range varmint rifle, 'Inherently Accurate' and not very difficult to do.
It's fun to shoot, it's fairly easy to take an off the shelf rifle and shoot 500-600 yards.
It's an absloute commitment, you marry the rifle, to reach 1,000 yards, all the while .30 cal rifles are doing 1,000 yards off the shelf...

Now, if that's how he wants to spend his life, it's fine with me!
Personally I've got better things to do that try to punch a knitting needle size hole in a paper target.
Paper targets have never eaten my garden or carried off my chickens, dug holes in pastures that livestock can break a leg in,
I've never tried to cook & eat a paper target, it just doesn't sound appealing...

I shoot for fun & to practice my skills, and to remove varmints or put meat on the table (not being in the military anymore, I don't practice shooting people).
I use the best tool for the given job, when I'm shooting 800-1,000 yards, I use a .30 caliber
When I'm shooting a 2" wide prairie dog at 300 yards, it's a .223 or .22-250
It's not a difficult concept to grasp.

As written before the rants, it depends on the rifle most times, newer rifles will shoot either, the cases are identical, and while really light .223 diameter bullets are hard to find, you can buy .224 diameter loaded rounds off the shelf from about 45 grains up to 99 grains.
I personally think a 77-99 grain bullet is ridiculous in the extreme, but to each their own...

 

[natdscott]

Jeep, ya may as well call me by name, instead of the "one guy" or "he" you're using.

We can agree to disagree on our opinions, but you can be civil about it.

You might be very surprised at what I have and have not taken into consideration with regards to the .22 centerfire.

One thing would be that my Kriegers get ordered at .219, where the Bartlein is .218. Well I'll-be-Huh. For dollars, Wisconsin will do anything I want, won't they?

Second thing is that modern bolt rifles usually don't get blown up because of bore dimension. Many of these barrels could happily swage your littel .224 bullets into a .204 bore if the casing could hold it, and the bullet had some room to get started. But THROAT dimensions you are correct about. THAT is what most likely blew up your buddy's rifle: a 77 grain bullet's bearing surface way out into the lands of a chamber that was throated with maybe as little as 0.000" freebore, intended for short 40-50 grain bullets with little-to-no bearing surface out of the neck. Max loads (which everybody seems to love) + jammed bullet = no bueno.


Nuther thing is that you are either misinformed about the bullet diameter thing, spreading it with too broad a brush, or simply falsifying the story to support your position. I don't know which.

I like to support my 'facts' with expert commentary when possible...seeing as I wasn't born with this knowledge, and they saw fit to write it down so's I could know.

Right now, I am sitting in my easy chair, staring at my dog eared 1957 Lyman manual whose pages pre-date the .223 Remington by over 5 years. Of 44 "22" bullets then-listed in production by 7 manufacturers, only 6 were still made in diameters less than 0.2240". Manufacturers in the 1950's were making decisions based on shooter demand, same as they are now.

The HORNET was originally tried with what amounted to rimfire barrels, and it was indeed found that those barrels shot (and shoot) better with .2225-.2230" bullets. Makes sense. .2175-.218/.222-.223 is pretty small for a thinly jacketed .224 to squeeze into, particularly in light of relatively crude internal finishes in barrels of the time.

But the idea that early "22s" were for .223 bullets--which is what you seem to be saying--is completely false:

1906: Newton developed the .22 Savage Highpower designed for a .228" 70-grainer.

1937: Winchester developed the .219 Zipper to use .224" bullets in the 50 grain range.

By the time Maj. Hatcher publishes his first version of the Notebook in 1947, every single 22 cartridge is listed for use with a 0.2240"+ bullet except the obstinate Hornet, still hanging back at 0.2235".

1950: Mike Walker, one of the greatest firearms engineers of the 20th century, finishes development of THE .222 Remington. This was a completely new casing design, and used the by-then-standard .224" bullet to produce accuracy and velocity levels previously unheard of. This cartridge--the grandfather of the .223 Remington----was to become the dominant force in Benchrest until the 1970's.

Short version: close as my library recalls, by 1950, centerfire "22" cartridges had all standardized on 0.224" bullets with that one noted exception.

The idea that people like Julian Hatcher, Mike Walker, and Eugene Stoner would somehow have chosen to make bore and/or bullet dimension decisions in favor of something other than 0.2240" is absurd.



So I'm not saying you didn't have a tight-bore .223 Remington rifle in the 1960's or sumthin, and I'm not saying that your loads cannot work, and I'm not even going to say that Mr. Semper Fi does not ALSO have such a rare rifle...

...but I AM saying that no factory was sending .223 Remington rifles out the door that'a way, and nobody in those factories ever intended for you to have to shoot 0.223" Hornet-minded bullets in them.

You're gonna have to provide some empirical proof for me--and hopefully others--to believe your statements about bore diameters, pressures, thick-headed bullets, etc. Otherwise, you come across as a ranting Internet expert.


-Nate

 

[JeepHammer]

The HORNET was originally tried with what amounted to rimfire barrels, and it was indeed found that those barrels shot (and shoot) better with .2225-.2230" bullets. Makes sense. .2175-.218/.222-.223 is pretty small for a thinly jacketed .224 to squeeze into, particularly in light of relatively crude internal finishes in barrels of the time.

But the idea that early "22s" were for .223 bullets--which is what you seem to be saying--is completely false:

And right there you directly contradict yourself...
First saying early center fire .22 used .223 bullets, then saying they didn't.
Make up your mind about your version of the 'Truth', which one do you want to tell?

The FACTS are, early .22 center fire was built around a .218" bore, every manufacturer had a different width & depth of rifling cut.
The FACTS are .22 center fire didn't use the stupid fast twist rate barrels until the military started using said stupid fast twist rates to stablize bullets often twice the weight of the early models/configurations.
The FACTS are the military is schizophrenic, reducing barrel length, increasing bullet weight, and still expecting the round to maintain velocity.
The FACTS are the first military M-16 production barrels were 1:14" twist rate, but then again they were shooting a reasonable weight bullet at high velocity...

Since you didn't understand the original post, and still don't,
I had no idea of what ".223" the OP was discussing the particulars of and immedately went on to say the .223/5.56 were virtually the same round at this point.
I can't help it if your 'Version' of history is skewed to support your 'Ideas', the fact of the matter is the grandfather of all this family of rounds is the .218 Bee (which I still shoot, and which does a very good job in it's intended purpose of rodent control.

I always have to count to 10 when someone writes/says, "Well, Kreiger, (or Shileen, or whoever) makes a PRECISE .218" or .219" bore".
That's all well and good, but I know when someone talks in absloutes it's always BS.
I own graduated bore scopes, I own pin gauges, and I've worked with thousands of barrels from every manufacturer (14 years at Marine Corps Special Weapons), and to make an absloute statement about any given bore is an absloute lie since 99 chances out of 100 the bore/rifling isn't what is advertised.
Some can be finessed into a reasonable shooter, but most wind up as common service rifle barrels simply because once material is gone, we can't put it back...

There is a reason the Marine Corps builds it's own special purpose weapons, it's because manufacturers can't be trusted to get things done correctly...

The OP got his answer in the first couple replies, WITHOUT all the 'Internet Expert' gook, clear, plain and simple.
So now, get your last word in with whatever you 'Claim' to be true, try and keep the condesention to a minimum, because I'm calling this thread done.
The OP has his answer...

 

[bwframe]

 

[natdscott]

So now, get your last word in with whatever you 'Claim' to be true, try and keep the condesention to a minimum, because I'm calling this thread done.

Jeep, I've said all that I felt I needed to say academically and then some. I agree with you, the OP has enough answers to the simple question asked, and he can sort out what choices to make...lotta good info in this thread.

I think we can both agree that the internet lends itself too well to a communication style that is abrasive and even aggressive. It also allows for a lot of assumptions to be made about gender, age, experience, religion, economic status, etc. Somebody around here has a humorous sign. line about the internet's ability to artificially increase the size of people's balls, and there's truth to that.

Of the many men and women on various internet forums who know me and have met me in person, I would wager every single one would agree that I can be a horse's-ass with a keyboard. I'm alright with it because I don't 'drive' around looking for a fight, and I don't make idle comments to stir crap and make enemies of people I'd not know passing on the street; we'd probably get along really well on the range or in the squirrel woods.

I think that ego is the basis of 90% of human problems, some of this problem between you and I included, and I try to work on getting better about that as I age. That said, I am still completely willing to to stand face-to-face and tell people they have no factual basis for what they're talking about. I was not raised to back down from a bully, same as you were not.

I own that personality here, and I own it in person.

I hope you own yours:

--While one guys rants, he's not considering...

--Now, what the new wave of 'Internet Experts' don't understand...

--...someone trying to shoot well at 1,000 yards with a .223. ... This is a disconnect between application & common sense...

--I use the best tool for the given job... It's not a difficult concept to grasp.

--As written before the rants...

-Nate

 

[JeepHammer]

In the last 45+ years of doing this professionally, I have found anyone quoting someone else's articles is suspect at the very least.
If YOU don't do the research work YOURSELF, then why in the world would you quote it as ABSLOUTE fact?
Just because you rad it in a magazine or self published booklet doesn't come close to making it 'FACT'.

The second part of that is, what EXACTLY are the qualifications of the author?
Example:
Is he a qualified & certified metalurigic expert, or is he some random guy that calls resistance to forming 'Spring Back'?
The metallurgist version (and correct version) of resistance to forming is 'Rebound'.
A 'Spring' is purpose designed to do work, not something that randomly happens to materials that are NOT intended to be 'Springs'.

Then we get into what's advertised as market names and NOT correct descriptions,
Example:
Calling a tool head with stations a 'Turret' press (Lee 'Turret' press that's actually a tool head press),
Or someone calling a volume (open hole/void) power dropper or charge thrower) a 'Measurer'.
Irregular shaped solids are WEIGHED, not one single granular propellant charge has measurements listed for VOLUME,
And in fact people complain endlessly the throwers/droppers don't produce consistent charge WEIGHTS.

It's either a scale WEIGHING the charge, or it's not, and power dispensers using a VOLUME are just dispensers, not measuring the propellant correctly.

Again, in case forming, everyone calls the head stamp surface to shoulder distance 'Head Space'.
Head Space is the CHAMBER of the firearm, and no place else.
You are talking DATUM LENGTH from head stamp surface to shoulder (Datum line, it's in the SAAMI drawings) that is *Supposed* to be slightly smaller than the head space in the chamber so the case fits the chamber.



Now, I relate what I've found DIRECTLY.
I don't quite some questionable source.
Like I wrote, I don't have an opinion, I have a scientific grade, graduated bore scope that will accurately measure 5 to 6 places behind the decimal point.
Most people think 'Bore Light', not up to 300x magnification with graduations so you can accurately determine the size, and finish of a bore...

Most guys have never heard of an air gauge, which is what we used in the military when I started, and what most barrel manufacturers still use today.
I have one, I know how to use it so I don't just take the word of the sales propaganda from manufacturers.
When I want to get down to the bone on sizing or finish of a barrel, I break out the bore scope.

I don't guess at annealing, trying to judge by 'Color' or 'Glow'.
I cores section the brass, I do hardness testing on a calibrated Rockwell machine, and I do micrographs (chemical staining & etching of brass, graduated microscope to see the chrystals & grain structure) to determine if the brass was property annealed, and to what degree it was annealed.

I say 'I Find', not 'I Read' or 'this guy says'...
I also don't speak in absloutes.
The more you drill down on any given subject, the more you find discrepancy/deviation, so only someone with Dunning-Kruger speaks in absloutes...

Terms like 'Generally', 'Typically' or 'Usually' don't seem to have meaning to 'Internet Experts'.
Their understanding of the language is usually as shaky as the understanding of the science or what they read somewhere and are now quoting in absloute terms... (Again, Dunning-Kruger effect).



Notice that when you get the actual first hand education and do actual research, you never quite get back to 100% confidence?
There is a reason for that...

------

Now, come around to the statement about how much throat erosion you WILL have (absloute) and not what you expect or anticipate from previous experience... (Experience being the key word)...

No one on the planet can be ABSLOUTE about Anticipated erosion. Period.
You have ZERO control over what the alloy mix of the barrel material will be, so getting EXACTLY the same metal alloy in the barrel each & every time is a fools errand.
Made from the same batch of steel, heat treated together, there will be differences in alloy from the top of the pour to the bottom of the pour.
The barrel blanks will not heat treat in EXACTLY the same way.

Same for bullet makers, the jacket or lead composition will have differences, slight *IF* you buy every single bullet you intend to shoot through that barrel all at one time and they all came from EXACTLY the same batch, but again, there will be differences in the batch from top of pour to bottom, and the extrusions of copper will have differences due to cooling rates changing.

Then there are the differences in cleaning, abrasives the burning propellants produce.
The barrel would have to be scientifically inspected for residue in between each shot to 'Absloutely' anticipate an exact erosion rate.

And let's not forget the insane rate of wear quoted in the first place...
If I 'Expected' barrel erosion at that rate, I would drastically change the velocity or bullet I was shooting!
While today's 'Extreme' (read internet expert) shooters scoff & make fun of 'Standard' velocity loads and common bullets, the lifespan of the firearm is a consideration.
When you find a 1935 or 1950 firearm that has thousands of rounds through it, but the erosion is still reasonable and the rifle shoots well, it's because someone didn't beat the living crap out of it, they stuck with 'Standard Velocity' rounds (and common sense) and the rifle still works well 50 or 75 years down the road...

I shoot 1,000 yards with a fairly standard velocity .30 round/rifle, I don't try and make a .20 cal. rat & poodle shooter do that job.
(Don't drive a nail with a wrench... Common sense)
Just because you *Can* cut your own nose off, doesn't mean you *Should* cut your nose off just because you *Can*...
You *Can* shoot a squirrel with a .50 BMG, and you *Can* shoot an elephant with a .22LR, it just doesn't make a lot of sense.

Since us older guys have hunted for meat, and since we have actually been in gunfights, maybe we are more practical in the age of 'Style' over Substance.
In 16 years as a forward combat Marine, i always wanted longer range with heavier bullet.
Much more practical to stop the bad guys with a couple rounds at 600-800 yards than to full auto gunfight with a poodle shooter in a phone booth.
(You have to be old enough to remember phone booth for that to make sense... The cell phone generation will have to Google it...)

-------

What DOESN'T happen anymore, (unless your 'Tactical' barrel is from 'China')
Your bore that is supposed to be .218" doesn't show up with +/- .004" tolerances.
.218" barrel with a .214" choke in it somewhere, or oversized at .222" so the .223" bullet more or less rattles down the barrel.
And yes, it did happen, I used to pick up really nice name brand rifles that just needed the choke worked out (hand lapping) or rebarreled.
For a Marine on a skinny budget, this was a source of income for me. ($435 a month before taxes/draws/allotments when I enlisted)

You don't see many barrels with stright rifling grooves or jagged/zig-zag rifling anymore. The rifling button didn't always start straight, and the lower end barrel makers didn't always chop off the starting/loading end of the blank so they didn't have the waste.

Barrels are getting better about the bore being aligned with the outside profile.
Nothing like crowning a barrel the bore is off center the outside profile... A rounded crown hides it pretty well, but it's still not right.
Nothing like an off center bore heating up and throwing shots off some strange direction!

Anyway, tired of the argument. Take it for exactly what you paid for it, or not...