So Many Seating Depth Questions On Bottle Neck Cases...

SAAMI specifications of 2.260" COAL for .223 Remington,

LINK TO SAAMI: http://www.saami.org/pubresources/cc_drawings/Rifle/223 Remington.pdf

NATO specifications of 57.40mm (2.2598") COAL,
2.550" to throat of barrel,

Source, US Marine Corps.

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With thanks and respect to 'Ammo Oricle',
A link to Ammo Oricle's VERY GOOD page on .223 Rem vs. 5.56 NATO...
http://ammo-oracle.razoreye.net/

556cham.gif


The common 'Short' chamber is now being called 'Wylde'
After a successful service rifle shooter named Bill Wylde.
The 'Wylde' chamber is 2.445",

Source, Bill Wylde and 'Wylde' chamber barrel/reamer makers.

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This is what I'm trying to get across...

THE POINT OF THE BULLET DOES NOT CONTACT THE RIFLING WHEN THE ROUND IS CHAMBERED.

FREE BORE IS THE DISTANCE THE BULLET BETWEEN THE BARREL 'FORCING CONE' AT THE BEGINNING OF THE RIFLING,

AND,
THE POINT ON THE BULLET YOU ARE USING WHERE IT CONTACTS THE FORCING CONE.

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A set back chamber, or lengthened COAL,
CLOSES UP the FREE BORE. PERIOD.

That is what this thread is about,
COAL questions that keep popping up.

The point between the EXPANDING TAPER OF THE BULLET NOSE TO THE CASE,
And where the bullet YOU ARE USING contacts the forcing cone.

It REALLY doesn't have a lot to do with 'SPECIFICATIONS',
It has to do with where your chosen bullet actually IS when the round is chambered,

AND,
How far forward that CHOSEN BULLET PROFILE has to move forward before it hits the forcing cone.

That is FREEBORE, No Rifling, No Restrictions on the bullet before it hits the forcing cone.

Bullet contact point with the throat/forcing cone set too far forward,
The bolt head spacing gets screwed up.

Bullet contact point with the throat/forcing cone, set too far into the case, Excessive Freebore.

THIS IS A THREAD ON SEATING DEPTH, FREEBORE,
And an easy way to determine how much freebore you have...
 
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SAAMI's maximum spec for the .223 Rem cartridge length is 2.260" and minimum cartridge length is 2.215". None of SAAMI's specs for the round's chamber is 2.260" as can be seen in:

http://www.saami.org/PubResources/CC_Drawings/Rifle/223 Remington.pdf

SAAMI's specs/glossary also says freebore is a cylindrical length of bore in a firearm just forward of the chamber in which rifling is not present. It's the same for every round fired in a given chamber as it's part of the barrel, not the round itself. Depending on who made the reamer, it may well be different across all of them.

http://www.saami.org/glossary/display.cfm?letter=F

While freebore is associated with bullet jump, it stays the same for each round chambered. Bullet jump depends on how far back the bullet's ogive contact point with the rifling is from the chamber throat where it contacts it. SAAMI lists "bullet jump" in their glossary:

http://www.saami.org/glossary/display.cfm?letter=B

If I'm claimed to be arguing semantics, so be it. But we all would be better off if we all have the same definition for each term used describing anything about cartridges and/or chambers else that "failure to communicate" will lead to bad ju ju.

I had called that part of the chamber immediately in front of the chamber mouth to where the angled throat (or leade) of the rifling starts the "throat" until I was recently corrected. In the SAAMI drawing above for the .223 Rem, it shows the freebore length to be .025" forward of the chamber mouth; the difference between the 1.812" and 1.787" lengths that are both .224" diameter at those points.

SAAMI's definition of "forcing cone" has nothing to do with rifle barrels; only revolver and shotgun barrels.
 
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ragwd said:
I have read this entire thread three times.

The subject is something I have been trying to wrap my head around. It helped a lot.

What I am taking from this is some people get good results with a jump and some people get better results with less.

It depends on the individual rifle barrel and bullet shape.

After reading the thread I now know how to measure it and find what works best for mine.
No short cuts, just measure and observe results. Thanks to all and keep these informative thread coming.
Click to expand...

YOU HIT THE NAIL ON THE HEAD!

Some barrels are chambered for .223 while stamped 5.56,
Some are the other way around,
Some are a mixture of the two...

Manufacturers have to anticipate the guy buying the rifle is an idiot, and will run what ever he finds laying around that will chamber...
(Including idiots that run .222 Rem through a .223 chamber!)

And guys running weirdly shaped bullet noses, extra long heavy bullets, and anything else they can scrounge up or read about and just 'HAD' to try through a factory made rifle...
The maker HAD to anticipate that kind of 'Use' (I say 'Abuse') and cut the chamber to accommodate the rounds so they don't harm the user...

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So now you have to HUNT DOWN what type of chamber you have,
Short, less freebore,
Or longer with a bunch of freebore.

The guys that HAND BUILD RIFLES know exactly where their chambers are,
Most guys are stuck with what came when they bought the rifle/barrel...

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This was a thread that has gone HORRIBLY SIDEWAYS,

It was simple enough in the beginning,
To answer some of the questions about 'COAL' (Cartridge Over All Length),
And that is determined by your FREEBORE,
And what will fit in your magazine...

By the time you close up 0.250" of freebore by making the Cartridge Over All Length (COAL) long enough to close up freebore,
The round is too long to fit/feed in your magazine,
Then you have a single shot...

Not the 'Optimum' for guys with varmint rifles and auto loaders...

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MY SITUATION is, I have SEVERAL rifles in .308 Win, .223 Rem, ect.
I like to hand load ONE ROUND for every rifle.

So the situation demanded I RE-Chamber all the rifles to shoot my most accurate rounds/favorite hand loads.
(this IS a reloading forum, although we are getting into gun smithing a little here)

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The next demand for MY RIFLES was seating depth changes between Hornady BT FMJ, my 'Plinking' round,

And my V-Max Varimint rounds.

Since the taper to full barrel diameter on the BULLET ITSELF is in a different place (farther back),
To cut down on freebore I had to set up a seating die to close up the freebore.

BULLET NOSE PROFILE is different on EVERY type of bullet,
So freebore changes.

That's why I say use the bullets you like to build/shoot to determine freebore for each round you make.

With me, it's FMJ and V-Max and not much else.
The seating die for V-Max has to have a pusher with a HOLLOW inside, as not to damage the ballistic tip,
So I have a RED strip on that seating die to tell the difference,
Rather than mess around and try to change seating depth, cranking out 'Dummies' or 'Test' rounds each time I switch in the loader...
Saves time and/or components when I make the switch from FMJ to V-Max.

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The situation might be YOU just need to make LONGER cartridges to close up freebore in ONE rifle,
Then just make LONGER cartridges for that ONE rifle,
But you are still subject to what will fit/feed from the magazine.

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The point here is,
You simply won't know what your freebore is unless you check your chambers with the bullets you are loading.

By checking chambers, and building your rounds to fit the chamber 'Better' you might just find out you can make that 2 or 3 MOA rifle into a 1 MOA rifle...

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I didn't intend this to turn into a crap fight between 'One Shot' hand feeding guys,
They are in an entirely different situation, and probably built the rifle from scratch...

I was addressing the guys with 'Unknown' chambers,
And the verity of questions about COAL...
And the guys that want to load a magazine instead of hand loading each round... and still TRY to improve accuracy.

This *SHOULD* have been simple,

With the shoulder seated in the chamber,

How far forward does the bullet travel before it hits the 'Throat' or 'Forcing Cone' of the barrel?

That distance is how much longer the COAL can be before things get dangerous,
So I gave a way to accurately measure it with a simple caliper instead of proprietary (and expensive) precision equipment you are only going to use once to a few times.

This will get you three places behind the decimal point (0.001") instead of 4 or five places,
But it's accurate enough to get you shooting better in most cases, and all it takes is some cases, bullets you like to shoot, and a caliper you should already have as a reloader.
 
SAAMI specifications of 2.260" COAL for .223 Remington,

LINK TO SAAMI: http://www.saami.org/pubresources/cc...0Remington.pdf

NATO specifications of 57.40mm (2.2598") COAL,
2.550" to throat of barrel,

Source, US Marine Corps.
Click to expand...

All through this thread you have been confusing Max OAL (2.260 vs 2.2598) with chamber dimensions, (reamer dimensions).

From you original post.
With that in mind,
Some of us are going back to the 'Short Chamber' and final finishing the chamber on new barrels...

SAAMI specifications of 2.260" for .223 Remington,
NATO specifications of 2.550" for 5.56x45mm
Click to expand...

Now you say max OAL for the 223 is 2.260 and the 5.56 is 2.2598 which ias basically Identical, yet you still toss out the 5.56 "NATO Specs" 2.550 in the same sentence.

Sorry, you are all over the board here and jumping back and forth between OAL (fit the Mag), chamber dimensions and reamer drawings.
 
Now you say max OAL for the 223 is 2.260 and the 5.56 is 2.2598 which ias basically Identical, yet you still toss out the 5.56 "NATO Specs" 2.550 in the same sentence.
Click to expand...

You would be correct about jumping around...
Since the COAL length has very little to do with head space,

And NATO 5.56 specifications have changed since the first 52 Grain bullet was adopted by NATO,
(NATO isn't bound to keep any specific size/length/chamber pressure, they can and do change to accommodate the rounds they want, instead of building to civilian 'Safe' specifications),

Current NATO chambers are now longer, I can't figure out how to scan/upload the scan from my '70s Armors manual to show the difference between older NATO and current NATO.

That is irrelevant anyway...
The entire point was to show how chambers are DIFFERENT,
And how to find headspace in YOUR particular chamber.
Freebore changes with every type of bullet you use,
And every seating depth/COAL you use.

That would be the point, and the source of confusion,
Every chamber is DIFFERENT,
EVERY BULLET IS DIFFERENT,

THERE IS NO 'STANDARD' FREEBORE,
No matter what any chamber reamer manufacture says since they simply don't know what bullet profile you are going to use...

You have to GAUGE freebore for the bullet you are using,
At the seating depth/COAL you are using.

That's why I gave a way to GAUGE your freebore for the BULLETS you are using in YOUR CHAMBER.


Not to argue this or that manufacturers design for chamber, or chamber reamer,
This or that reload manuals specification for COAL...
NOT to argue for this or that bullet profile...

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So as to off point,
The entire intrigue/argument is moot since it's off topic of the intention of the post in the first place,

Which was to figure out how much freebore you have in any particular barrel,
And what COAL you *CAN* safely use.

What the 'Specification' guys seem to miss is the COAL and chamber specifications WILL NOT give you the freebore for all bullet designs/shapes.

They would rather argue semantics in specification drawings rather than clear up any issues I was unclear on...

Then there are the 'Load One, Shoot One, Repeat...' guys that could care less about getting a round to fit in a mag,
Or keeping the bullet from getting pushed back into the case during bolt cycling from mag to chamber...

Then there are the guys that allow the bullet to move in the case,
Build long, crank the bolt to set bullet depth right on the forcing cone, nose of the bullet already in the barrel...

This is a bad idea for a lot of reasons out of bench rifles and single shot competition rifles.
Non-compressed powder charges come to mind right away,
Bullet rattling around in the case from recoil, spilling powder, an inch of freebore, bullet NOT aligned with the bore at all,
And that's all while it's still in the magazine.

Unless you have some VERY precise reloading equipment,
Hand check each and every case neck,
You are asking for bullets in the cases with the powder,
And the powder in the magazine.

The heavier the recoil, and the more aggressive the feed ramp, the more the problem compounds itself.

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Guys that run compressed powder charges go the other way, TOO MUCH compression on the powder charge...

Nothing like a bullet stuck in the rifling and a heavily compressed powder charge to make for inaccuracy and/or a dangerous situation...

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If you want to ignore freebore,
Or since it's been explained in detail over and over again,
Choose to NOT understand the situation,

Then why in the world would you comment at all?...
 
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I do not get tangled up with off the lands. I want to know where the lands are located, I drill the flash hole/primer pocket to a diameter that accommodates a cleaning rod. I seat a bullet with good bullet hold (good bullet hold? is all the bullet hold I can get). I then seat the test case in the open chamber and push the bullet out to the lands, that is it. When I remove the case with the bullet held with good bullet hold I transfer the measurements from the chamber to the seating die.

I then zero the height of the seating stem above the die. Zero is at the lands, then there is throat erosion, I have too many barrels to have throat erosion, then there is taper, when I want to check taper I make a tapered gage. It is possible to purchase throat and muzzle erosion gages.


steve4102, you furnished some good links.


F. Guffey
 
Guffy, I threaded a screw into a case that pushed the bullet out into the throat.

The issue I had was as the bullet hit the throat,
The screw threads would lift the case shoulder off the chamber.
To much mechanical advantage in my case...

For me and bottle neck cases,
I've found from shoulder seated in the chamber,
From seated shoulder back is head space for the bolt,

Shoulder forward to where the bullet meets the throat is the 'Zero' freebore reading.

I use series of the bullets I'm loading for in 0.002" to 0.005" increments from the 'Recommended' COAL,
out to where the bullet hits the throat.

That's freebore I usually want to close up...
Without changing head space, shoulder back to bolt face (or case shell plate)...

A case neck with just enough friction on the bullet you intend to load to hold position while you use the caliper on it is a good way to do it,
But occasionally when I do it that way, I get the bullet lightly wedged in the throat, while the case extracts empty.

That's why I made the incremental cases/bullets to TURN in the chamber.
With a 'Sharpie' coating the case shoulder and bullet,
By turning I can make a VISUAL VERIFICATION the case stayed seated on the shoulder,
Or the bullet hit the throat and kept the case from seating.

By using the cases/bullets I'm actually going to shoot,
I get a 'Go/NoGo' visual verification without taking the chance of pulling the bullet out of the case,
Or having the shoulder of the case NOT seated (Bullet seated too far out)...

Threading a old cleaning rod in these freebore gauges,
And using a 'Sharpie' I can use them over and over again,
And I can reach the most RECESSED chamber without pulling the barrel to get at the gauge.

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I found out that I couldn't reach the throat with the bullet so far out of the case I had to solder it on the case...
That's what I call EXCESSIVE freebore!

No chance at all of ever getting that round into a magazine!
So the ONLY choice to close up the freebore was to set the barrel back into the action,
And cut the chamber for a reasonable freebore...

While I was at it, I just cut all my chambers to shoot a reasonable size/shape bullet,
And re-chambered the rifles to match my rounds instead of the other way around...

This also took care of throat erosion, it was simply cut away by the new chamber/throat.

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Throat erosion...
One thing you will find is the throat won't erode/wear at the same rate all the way around.

By making up a long CONCENTRIC test bullet,
And using the 'Sharpie' or 'Dykem' on it,

(And I STRESS CONCENTRIC TEST BULLET,
If the bullet is in the case at an angle, the readings you get will be moot...)

Then moving the rod only about 1/8 turn, back and forth,
You will find where the throat IS NOT eroded.
It will contact the bullet sooner where it's NOT eroded.

A centered, concentric chamber aligned with the bore will give you a nice round ring on the CONCENTRIC test round, even though you only moved the bullet 1/8 turn or less (back and forth) to produce the visual reference mark.

This also finds POORLY CUT CHAMBERS,
Where the chamber is at an angle to the bore.
MUCH more common than you think!
 
THERE IS NO 'STANDARD' FREEBORE, No matter what any chamber reamer manufacture says since they simply don't know what bullet profile you are going to use...???????

Rediculous. Freebore is a fixed dimension from the chamber mouth forward to where the rifling starts angling down to bore diameter for each cartridge in SAAMI specs. That's the standard for those cartridges listed in SAAMI specs and info.

That said, any chamber reamer can make their chamber's freebore to whatever they want it to be; then it would be a non-standard freebore.
 
You would be correct about jumping around...
Since the COAL length has very little to do with head space,
Click to expand...

Headspace?

What does headspace have to do with your original post pertaining to "Seating Depth" and throat dimensions?

Jump around some more?
 
Jeep Hammer, correct seating depth is whatever shoots best in a particular rifle and if required still fits in the magazine. My 6 PPC is happiest when the case has just enough neck tension to keep the bullet and powder from falling out. I can take my fingers and push the bullet in or pull it out. It is long seated and the rifling pushes the bullet into the case. Should it shoot that way? Many say it should not. I say the rifle forgot to read the book that told it that it could not be accurate that way.;)
 
This also finds POORLY CUT CHAMBERS,
Where the chamber is at an angle to the bore.
MUCH more common than you think!
Click to expand...

"MUCH more common than you think!" I will assume you think I think it is common.

I have reamers for almost everything I shoot, no one does it but it is possible to make tools for determining chamber/bore alignment. Then there is literature/published manuals. One says if not done correctly there is no way the chamber can be straight.

F. Guffey
 
Some guys are entrenched,
Or they fail to realize there isn't a 'Standard' bullet profile, which determines freebore.
The chamber is cut in steel, and set,
So the BULLET profile/seating depth determines freebore,
Unless you do your own chamber/freebore cuts.

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Guffey,
There is a reason I use a chamber cutter/reamer,
And a throat cutter/reamer,
And do them in two separate processes.

This is 'Gun Smithing',
But my PILOTS usually are MUCH longer than what comes on the standard 'Reamers' for semi-finished chambers.
Short pilots suck,
They work OK only if everything else is dead straight to start with...

You would *THINK* there would be a way to keep the barrel chucked up while cutting profile,
AND cutting the rifling,
AND cutting the chamber,
But it seems to be three different processes in a lot of cases which leads to misalignment issues.

Those '$499.95' ARs are PARTICULARLY susceptible,
I have no idea where they get their barrels, most of the 'Cheap' versions don't have a manufacturers mark on the barrel.
And none of those AK clones from China had a chamber aligned with the bore...

When I cut chambers, I take great care to get the barrel chucked up aligned WITH THE BORE,
Not with the outside of the barrel.

Nothing like having a chamber 0.003" off center the bore because they cut the chamber centered with the outside of the barrel instead of the bore!
I'm not the last word expert here, but I think trying to move the bullet SIDEWAYS to get into the rifling is a bad idea!!!

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Semi Finished Chamber...

I always figure I'm starting with a FRESH, SHARP chamber reamer when I finish the chamber in a new barrel,
While I have no idea how old the reamer will be at the factory...

Lined up with the bore, fresh chamber reamer, cut the chamber for the case...
Then use a second to cut for freebore/throat with no case cutting edges...

It costs a second reamer,
The Chamber reamer you grind the throat edges off, then finish the case chamber,

The Freebore/Throat reamer you grind the chamber edges off so it just cuts the freebore/throat.

The cost of the second reamer is small compared to being able to close up freebore for my favorite rounds being accurate.

Personally, I think this is a case where 'One Size Fits Everything' is more like one size fits nothing...
Mostly because every chamber reamer maker has a different idea about what the chamber *Should* be instead of what I want it to be...

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Reynolds,
You are using the throat to set freebore to ZERO.
Not unusual among bolt competition shooters,
And even some semi auto shooters.

If it works for you, then there you go!
 
Jeep H., Reynolds is definitely using the throat to set his bullet jump to zero. The distance from the origin of the rifling at bullet contact point is zero. But his (the barrel's actually) freebore remains the fixed distance from the chamber mouth to the origin of the rifling at freebore diameter.

Call it "freebore" if you insist, but that's the wrong term according to most standards and definitely according to SAAMI's and the industry ones.

I've used bullet jump on 30 caliber bullets in .308 Win. barrels ranging from .010" to .080" and observed insignificant change in accuracy through 300 yards. Freebore length in their chambers were not all the same. Sierra's, Lapuas, Bergers as well as the military 172-gr. FMJBT match bullet; all virtually equal in that regard. Bullet quality was the big difference, not their shape.

Maybe 22 caliber barrels are different, but I doubt it.
 
Now, the INTENTION of this thread was BULLET SEATING DEPTH questions and why there is so many I questions,
To clear up the 'Mystery' in seating depth, which is freebore and/or fitting into the magazine.

I honestly wasn't trying to start a crap fight,
It should have been posted in gun smithing I guess...

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Bart,
If it's not "Bullet Free In Bore" space, then what would you call it?
It's not 'Bullet In Rifling'.
Completely different dynamics going on in the rifling...

I'm not some 'Mall Cop', I'm 54 years old,
I'm not making wild claims here,
I'm not talking about anything that isn't literally carved in steel and you can measure.

The only other thing I've seen it called in the past 40 years is 'Distance To Throat',
And when it was listed as distance to throat, the distance measurement started at the end of the case.

Bart said:
Call it "freebore" if you insist, but that's the wrong term according to most standards and definitely according to SAAMI's and the industry ones.
Click to expand...

SAAMI has a set of mechanical specification drawings.
These are *Supposed* to be "Standards".

I agree with that.

Try and find a chamber reamer with SAAMI specifications in the real world.
Most people never inspect the reamer when it arrives,
They order SAAMI,
Expect SAAMI,...
Never check, just ream until the headspace is correct and run the rifle.

To make things even MORE aggravating,
There is a trend toward just reaming until the bolt closes on a chamber and calling headspace 'Correct'...

Along with that, people are turning the barrel in the receiver so they can put the bolt in to check headspace!

Either way you slice it, that method puts the reamer WAY OUT ON A LONG EXTENSION that can and will wobble,
It will aggravate ANY misalignment between reamer and bore,
All because they are too lazy to thread the receiver on the barrel, check head space, take the receiver off the barrel,
And ream again if necessary...

Nothing like having a chatter marked, over sized chamber because the reamer was on too long of a bar to reach the chamber through the receiver.

REAMERS...
Every one I order is up to +/- 0.005",
And every 'Name Brand' tool makers has their slant on what an 'Updated' chamber looks like.

It *SHOULD* be,
It's either SAAMI or it's NOT SAAMI, nothing in between.
There is no 'Gray Area' or 'Area For Improvement' when you order a SAAMI chamber reamer!

'Updated' or 'Improved' isn't SAAMI, and it's AGGRAVATING as a machinist...

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Someone in a previous post listed about half a dozen versions of .223/5.56,
I suspect, A sales chart from ONE maker or retailer...

The point there is,
You order a ".223 Rem" or "5.56x45mm" chamber reamer,
And you take your chances with that it's actually going to cut when it comes in,
SAAMI,
Close to SAAMI since the specs are SLIGHTLY wrong,
Or some 'Exotic' chamber someone came up with.

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Then we get into 'Lesser' models, which you as a competitor probably don't keep up with,
But walk into a gun smith fairly regularly...

Chambers out of square, out of plumb, out of level,
Freebore of 0.250" or 0.300",
Threads cut on the barrel or receiver at angles,

Scratches and Chatter marks that hold onto the brass like a barnacle on a boat hull...

And finding copper shards from the jacket in the chamber after firing is not a good sign...

That's why I've become of PROPONENT of checking your chamber/freebore/throat when the rifle isn't shooting...

And these are FACTORY OFFERINGS!
(Factory located where with what labor force? I have no idea...)

I don't have any idea how they are making barrels this lousy, but they ARE OUT THERE, in growing numbers...

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Like I posted before,
It's AGGRAVATING to get a reamer that isn't what you ordered...

Having to order TWO, one that has the 'Correct' SAAMI case,
Then another one to cut the freebore/throat.

Nobody likes adding an extra hour and second $50 reamer to something as simple as cutting a chamber,
But sometimes that is what has to be done...
 
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The old saying used to be,
"You buy a good shooting barrel at a premium,
And they throw in the rest of the rifle"...

Not exactly true anymore...
 
Bart,
If it's not "Bullet Free In Bore" space, then what would you call it?
Click to expand...
I'd call it what SAAMI does and thousands of others. Go back and read my links to it.

Freebore's a constant dimension from the chamber mouth to the origin of the rifling. Bullet jump's the distance it jumps from its seated position to the rifling. It grows .001" for every one or few dozen shots fired depending on the powder charge weight ratio to bore capacity; grains of powder to the bore's cross sectional area in square millimeters. The only way to keep the original bullet jump distance what it was without setting the barrel back is to seat bullets shallower at the same rate the throat erodes away. That's often called "chasing the lands."

Interesting info on throat erosion and how far the throat erosion gauge goes into 5.56 NATO barrels for various round counts; bullet jump increases about that same amount:

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA024765
 
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In a more succinct way,
You just made my point...
You freely admit that USEAGE VARIABLES change the freebore!

'Free Bore' is different on every rifle, SINCE IT CHANGES!
You listed density of the bullet hitting the throat, powder charge, and other VARIABLES!
Leaving out metal density/compaction rates which will determine the 'Normal Erosion' rate/amount per round.

It's the VARIABLES, WEAR, HAMMERING, EROSION (both burn/power/friction and natural compression)

AND, If the chamber wasn't cut with excessive freebore in the first place, which a ton of 'Production' rifles are...

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My point ENTIRELY was to give a reasonable way to CHECK freebore, not *ASSUME* it's at SAAMI or some other specification...

USING THE BULLET/SEATING DEPTH YOU SHOOT MOST OF, SINCE 'BULLET JUMP' (Freebore), has a bunch to do with the profile of the BULLET YOU ARE CURRENTLY USING...

Jump from 'Seated' position to throat, FREEBORE...
Bullet MOVING FREELY...,

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This *SHOULD* be a given to anyone that seats LONG and lets the throat reduce freebore to ZERO,
Since they have a working knowledge of the chamber/bullet interaction.

The bullet does not have ANY freebore with the bullet set long, and allowing the bullet to retreat into the case.

This is an ACKNOWLEDGMENT of the FREELY MOVING BULLET, FREE BORE.

And their solution to compensate for that freebore movement...

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Like I said, this WAS a way to check for the FREEBORE, Freely Moving Bullet, NO RIFLING OR THROAT,
And how to check it with your current chosen rounds.

And *IF NEEDED* a way to correct the chamber/freebore, or seating depth to something a little 'Tighter'. (Less Freebore)

Doesn't matter if it's shooting (Erosion/Compaction) that moves the throat,
Or if the chamber was cut with excessive freebore,
It was a simple way to check your freebore and make corrections that *Might* improve accuracy.

Or you can just keep shooting, and ignore it all like most people do...

This was strictly to shed some light on 'Seating Depth' and 'Cartridge Over All Length' questions.

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Cut/Rethread/Rechamber, (all one process while the barrel breech is chucked up in a lathe),
Will give some added life to old barrels that still have good rifling,

And it's not too difficult for the 'Average' gun smith or machinist to do without having a bunch of firearm specific tools in the shop...

Closing up head space/freebore issues as you find them in barrels that still have good rifling.

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This will probably get another argument started,
But super thick lugs on bolt rifles (allowing extra threads on barrels),
And long threads with shims to set headspace used to often be the 'Norm' with a lot of accuracy shooters that built their own rifles, but didn't have a lathe and accurate tail stock...

As throat eroded, less shims or smaller lug could be used to set the barrel back in the reciever,
Closing up both headspace,
A simple chamber reaming would bring the head space/freebore back into tolerance.

Undercut lugs at barrel to reciever assembly point would set the barrel back, without having to start bedding all over again,
Or removing shims between barrel and lug, same results.

I don't know why maintaining a PRECISE freebore was so important back then, might have been the powders that liked to eat away at the barrel material made back then...
Super high velocity was all the rage, and throats/chambers took a beating.

Folks are smarter now, only a few places brag about getting up to 4,000 FPS,
Materials & throat designs are better,
Good barrel materials won't erode nearly as quickly as the used to. (a big plus in my book),

And with the bolts that lock into barrel extensions instead of the receiver,
This is a moot point.

45 pound bolt bench rifles built on surplus Mauser actions have pretty much gone the way of dial telephones since everyone is in some competition club with specific rules...
But it's worth mentioning since it directly applies to freebore.
 
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Whatever............

My freebore rear and front reference points are the same as the chamber's when new. That doesn't change; ever.
 
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I will assume no one has read Weatherby and I will assume no one has a Weatherby catalog. I want to know where the rifling is located, I do not find it necessary to wake up in a new world every morning, starting over everyday is something some find more interesting, I don't.

F. Guffey
 
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