Cartridge Over ALL Length Tolerances????

[Pete E]

This is a question regarding nomenclature as much as reloading.

What tolerances should I load my .308win ammo to with regards Cartridge Over ALL Length ?

I am using a digital caliper, so so would rounds that had a consistancy in length of + or - 0.005" be considered good or bad? Or should I be looking at + or - 0.0005" which is all my caliper will resolve to...

I hear people talking about "ten thou" or "five thou" and I confess I'm not 100% sure how that translates on the caliper display.. I assume that:

0.01 = "ten thou"
0.005 = "five thou"

Regards,

Peter

 

[Victor N TN]

Re: Cartridge Over ALL Length Tolerances????

Peter,

You numbers on reading the calipers are correct.

"I hear people talking about "ten thou" or "five thou" and I confess I'm not 100% sure how that translates on the caliper display.. I assume that:

0.01 = "ten thou"
0.005 = "five thou"

In the books I have the case length for the 308 Win case is listed as Max length 2.015" and minimum tim to length is 2.005"

If you are shooting a custom chamber you might want to measure your chamber to see what the length was cut to. Different custom reamers cut the case mouth at a different length... sometimes. Cutting the brass too short will speed the erosion of the throat area of the barrel.

 

[Pete E]

Re: Cartridge Over ALL Length Tolerances????

Victor,

Thanks for confirming about the nomenclature..

With regards the Cartridge Over All Length, I didn't explain too well...

Lets say from trial and error that I've deterimined that my bullets need to be seated .005" off the lands and that using a bullet comparitor that measures to the ogive, a round so loaded giving a reading of being 2.505" long..

Obviously even with the best seating dies there will still be a tiny variation in the length of each subsequent round loaded.

What I need to know is what is considered acceptable when it comes to that variation?

Using a Redding Mictomete seating die, the variation of my loaded rounds can be as much as + or - 0.005" (Again measure at the ogive with a comparitor on my Caliper *not* measured to the tip of the bullet)

Is that acceptable? good? bad?

Regards,

Peter

 

[1SMALLJOHNSON]

Re: Cartridge Over ALL Length Tolerances????

Peter,
You're likely getting the variation from either the die, or more likely variation in the ogive on the bullets, bullet to bullet. Don't worry about 0.005". That's about the thickness of a piece of paper. If your system is so finicky, I'd recommend a different system.
The best advice anyone can give you is, "Try it and see". Run some bullets deeper by 0.010" and some longer by the same. See how differently they shoot. Just be mindful: Jambing the ogive into the lands WILL increase your pressure. Be careful.

 

[mattmcg]

Re: Cartridge Over ALL Length Tolerances????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 1SMALLJOHNSON</div><div class="ubbcode-body">Peter,
You're likely getting the variation from either the die, or more likely variation in the ogive on the bullets, bullet to bullet. Don't worry about <span style="font-weight: bold">0.0005"</span>. That's about the thickness of a piece of paper. If your system is so finicky, I'd recommend a different system.
The best advice anyone can give you is, "Try it and see". Run some bullets deeper by 0.010" and some longer by the same. See how differently they shoot. Just be mindful: Jambing the ogive into the lands WILL increase your pressure. Be careful. </div></div>

Corrected that for you.....

 

[mattmcg]

Re: Cartridge Over ALL Length Tolerances????

So to clarify the mathematical nomenclature.

123.4567

^ hundreds
-^ tens
--^ units
---^decimal
----^tenths
-----^hundredths
------^thousandths
-------^ten thousandths

Notice the 's' for integers and 'ths' for decimals. Somebody could easily say "56 thousandths" as they could say "5.6 hundredths".

Was this what you were asking for?

 

[Pete E]

Re: Cartridge Over ALL Length Tolerances????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 1SMALLJOHNSON</div><div class="ubbcode-body">Peter,
You're likely getting the variation from either the die, or more likely variation in the ogive on the bullets, bullet to bullet. Don't worry about 0.005". That's about the thickness of a piece of paper. If your system is so finicky, I'd recommend a different system.
The best advice anyone can give you is, "Try it and see". Run some bullets deeper by 0.010" and some longer by the same. See how differently they shoot. Just be mindful: Jambing the ogive into the lands WILL increase your pressure. Be careful. </div></div>

Thanks for that...I've been reloading hunting ammo for a while now, but I'd like to refine my methods/approach and tailor them for long range shooting..Obviously consistancy is important to get good results, so I'm looking for "yard sticks" to compare my complete ammo to...

Regards,

Peter

 

[mattmcg]

Re: Cartridge Over ALL Length Tolerances????

And as far as variation is concerned, I consider a +/- .001" to be acceptable. BTW, people load anywhere from .005" to into the lands on their bolt actions. Really you have to play with the jump to see what works best for you.

 

[Pete E]

Re: Cartridge Over ALL Length Tolerances????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Hazardus</div><div class="ubbcode-body">So to clarify the mathematical nomenclature.

123.4567

^ hundreds
-^ tens
--^ units
---^decimal
----^tenths
-----^hundredths
------^thousandths
-------^ten thousandths

Notice the 's' for integers and 'ths' for decimals. Somebody could easily say "56 thousandths" as they could say "5.6 hundredths".

Was this what you were asking for?
</div></div>

Yep, partly, that explains it even better...

Edited as you've just answered my other question with another post!

 

[mattmcg]

Re: Cartridge Over ALL Length Tolerances????

Oh, and one last thing in regards to my preferences. I typically start my load development .002" from the lands and go from there. Probably a good place to start for you as well with a bolt gun.

 

[Fuzzball]

Re: Cartridge Over ALL Length Tolerances????

When shooting a factory rifle/barrel and off-the-shelf bullets, a seating variation range of 5 thou means nothing.

 

[Victor N TN]

Re: Cartridge Over ALL Length Tolerances????

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fuzzball</div><div class="ubbcode-body">When shooting a factory rifle/barrel and off-the-shelf bullets, a seating variation range of 5 thou means nothing. </div></div>

Pretty much correct.

 

[1SMALLJOHNSON]

Re: Cartridge Over ALL Length Tolerances????

GUYS!

A piece of paper is between 0.005 and 0.007". No extra zero's! Five thou to seven thou! Not five-ten thousanths!

When setting up a load, if you're using ANYTHING but VLD bullets, go for ~ 0.020" jump. That's twenty thou. It's a really good place to be. Jambing the bullets into the lands is not a good idea for general purpose shooting, sniping or even almost all target shooting. That being said, if you're running VLD's, you'll want them on or into the lands. However, be careful. Push a bullet into the lands, and you'll up the pressure considerably. Back off the charge weight and start working up safely.

Just so you all understand: one ten thousanths is about 1/50 of a sheet of paper! Chances are your mike/comparator/fingers/etc won't come to the same number time and again. If you're measuring to 0.0001, 0.0005, anything less than 0.001 for seating depth, you're jacked up.

Stop worrying and get shooting. Sure it's fun to tinker, but kripe, keep it in perspective! Not even the best bench rest guys bother with measurements on COAL of 0.0001 increments.