7mm-08 headspace measurement

[Savage Bacon]

Does anyone have the printed headspace length measurement for the 7mm-08 case? I bought the hornady headspace comparator and it is not mentioned in my nosler reloading book. Thanks

[Pathfinder76]

What is it you are trying to accomplish?

[warriorboy10]

You have the comparator! Do you have the 7mm-08 modified case and bullet seating depth gauge? That is what is needed, then you figure out your exact headspace using your bullet with the bullet jump that you want.
You want the headspace for that particular chamber and can be different for different types of the bullets ogive.

[Savage Bacon]

I'm fitting my cases so they snug up in my chamber and want to see where I am compared to the specs.

[Pathfinder76]

Just out of curiosity?

[Dick284]

Originally Posted by Savage Bacon

I'm fitting my cases so they snug up in my chamber and want to see where I am compared to the specs.

Its admirable that you are curious as to where your rifles headspace is set, but let’s face it the exercise is pretty much pointless, as the headspace is what it is, unless you want to set your barrel back, and re do the headspace.

After your first firing your brass is set to your rifles headspace.

Determine your headspace and set your dies to manage your brass accordingly.

[303carbine]

Originally Posted by Savage Bacon

I'm fitting my cases so they snug up in my chamber and want to see where I am compared to the specs.

Most chambers are going to be a bit different, fire forming and neck sizing for your rifle is the best way to go.

[Savage Bacon]

So should I now write down my 1.620 and always come back to this measurement? It's hard to tell when the bolt starts to get some resistance because it cocks on bolt close. These cases will only be used in this rifle.

[Pathfinder76]

Originally Posted by 303carbine

Most chambers are going to be a bit different, fire forming and neck sizing for your rifle is the best way to go.

No, it isn’t. FL resizing while in control of headspace is.

[Full Curl Earl]

I agree. But this thread will go sideways if we open that up. Lol
QUOTE=303carbine;3894267]Most chambers are going to be a bit different, fire forming and neck sizing for your rifle is the best way to go.[/QUOTE]

[qwert]

Originally Posted by Savage Bacon

Does anyone have the printed headspace length measurement for the 7mm-08 case? I bought the hornady headspace comparator and it is not mentioned in my nosler reloading book. Thanks

https://saami.org/technical-informat...ami-standards/

https://saami.org/wp-content/uploads...-SAAMI_CFR.pdf
see page 50

The SAAMI 7-08R datum dia is .400", and case base to datum dimension = 1.634 (+.000-.007").
The .007" allowable spec tolerance is a LOT larger than typically recommended case shoulder bump for best accuracy and case life.
Practically, I agree with post #6. as suggested procedure can best manage SAAMI allowable chamber variation.

Headspace comparators are very useful to provide a 'relative' measurement, but IMHE are not accurate enough to properly measure 'absolute' head-space. A proper solid head-space GO gauge is much more accurate, and can be used to calibrate a comparator, and measure an actual chamber.

The Hornady comparator bushings have a square SAAMI datum sized shoulder, and can measure CBTD directly, but they are soft aluminum and can easily lose accuracy.
The Sinclair case bushings have a bevel matching the shoulder angle, and are made of much harder material.
IMHE, both require calibration against a solid GO gauge if an 'absolute' measurement is required, but for reloading purposes a 'relative' measurement is more useful, as we need to fit the resized case to the actual chamber, and not the spec dimension.

Good Luck, YMMV.

[Savage Bacon]

Thanks qwert. My once fired cases all measure between 1.619 and 1.621. With the majority being 1.620. Shorter than the 1.634 - .007 spec. I guess I will leave the shoulders alone and recheck after they are twice fired. I know the saami spec is not perfectly dead on to "my" chamber. I just wanted to see where I am in comparison to that number. Yes just out of curiosity. Thanks again

[qwert]

Originally Posted by Savage Bacon

Thanks qwert. My once fired cases all measure between 1.619 and 1.621. With the majority being 1.620. Shorter than the 1.634 - .007 spec. I guess I will leave the shoulders alone and recheck after they are twice fired. I know the saami spec is not perfectly dead on to "my" chamber. I just wanted to see where I am in comparison to that number. Yes just out of curiosity. Thanks again

IMHO, your ‘curiosity’ is a worthwhile exercise, well worth the time and effort of self-training. All new tools require familiarization to learn their individual peculiarities, accuracy, and usefulness, many tools perform very well in ‘off label’ usage and intended market. Once familiar with the abilities and achievable accuracy, results of other use will be easier to evaluate.

I do suggest you obtain a quality, solid, .08Win head-space GO gauge; it will gauge all the .08Win family.
Use it to calibrate your comparator & bushing, and accurately measure your individual chamber using various thickness tape applied to the base of the gauge. (IMHO, this is more accurate than the 2 gauge GO/NO GO procedure, which is more suitable for a production environment)

Compare your measured chamber with a case before and after fire-forming in your chamber, the difference is (probably) ‘spring-back’ which can vary with case hardness and other factors.
Then use the comparator to set your sizing die adjustment to partially resize the case for desired shoulder bump & fit in your chamber, (expect similar case ‘spring-back’ to occur).
Log your results for future use and comparison.

Good Luck, YMMV.

[Savage Bacon]

The GO gauge is next on my list. Thanks again for your help. I'm loging all of the measurements and will start comparing after they're fired again. I agree that my experience will benefit from doing the extra work now so I definitely don't mind being particular and going the extra mile. It is a learning experience trying to tune this thing in that's for sure.

[qwert]

Originally Posted by Savage Bacon

The GO gauge is next on my list. Thanks again for your help. I'm loging all of the measurements and will start comparing after they're fired again. I agree that my experience will benefit from doing the extra work now so I definitely don't mind being particular and going the extra mile. It is a learning experience trying to tune this thing in that's for sure.

Welcome to the affliction.

IMHO, use of proper measuring tools facilitates consistency & repeat-ability, which are the fundamentals of precision.

Good Luck, YMMV

[qwert]

Originally Posted by Savage Bacon

Thanks qwert. My once fired cases all measure between 1.619 and 1.621. With the majority being 1.620. Shorter than the 1.634 - .007 spec.
snip

Your comparator may be returning a lower than expected result due to the size or shape of the datum contact edge of the bushing.
If it is not perfectly square (or over spec diameter) it will under-report, and illustrates the possible inaccuracy of using an un-calibrated comparator.

Good Luck, YMMV.

[Savage Bacon]

Do I calibrate it with the GO gauge and find my comparators zero from the GO gauges spec?

[qwert]

Originally Posted by Savage Bacon

Do I calibrate it with the GO gauge and find my comparators zero from the GO gauges spec?

There are several possible procedures and methods, but the solid GO gauge provides a way to measure the comparator indicated error, which can then be added to or subtracted from indicated to obtain true value.

Alternatively, it may be possible to zero @ the value of the indicated error and true value read directly, without requiring further calculation.

Caution, it is easy to get + & - values confused.

Good Luck, YMMV.