Bullet Length vs. Freebore

12 April 2008, 23:55

Clif Maloney

It seems I'm always chasing my seating die when attempting to achieve a 2.670" COL for my .243. I've checked headspace and freebore in the rifle I'm using and all is okay except the freebore issue.

- Considering bullet lengths in general without consideration of brands/styles, etc....is the freebore going to be screwed up with bullet lengths varying by as much as +/-.0070"

I'm anal about my reloading and I like everything exacting: case weights, lengths, powder measures, etc...

I set up my press to seat a bullet on one shell at 2.670"....the very next one may seat at 2.659" and the next at 2.725" - it's driving me nuts!

Should I not worry about it and just go on? Is there a generally accepted tolerance for seating depth? Without knowing if the bullet length variance is occuring at the nose or tail....I have no way of knowing if my freebore is changing.

Thanks in advance.

13 April 2008, 00:17

duckboat

Clif,

To answer your first question, it depends on how much margin you left between your goal COL and the lands. If you get a bullet that is seated towards the high end of your margin of error then you run the risk of pushing the bullet into the lands. Just make sure you aren't trying to seat too close to the lands.

I would say the variance you have is on the high side depending on what type of bullets you are using. If you are using plastic tip bullets from Nosler or Hornady, I would say something might need to be adjusted...such as making sure your die isn't loose. If you are using inexpensive soft tipped bullets that normally have more variance, then I would say you might be in the normal range.

For example on my 6mm Remington bullets using nosler plastic tips, my OAL varies from 2.920-2.926. That is using a normal RCBS seating die.

13 April 2008, 01:34

Clif Maloney

RCBS Carbide Dies, Sierra 1535 90gr FMJ BT. Freebore on the rifle checked at .097. Checking an old Speer 1044 SP, COL 2.67" load showed .041 - a gap of .056". The new loads with the FMJ (COL 2.67) checked at .095 - only a .002 tolerance. I'm thinking this might be a little close although a chambered round does not show evidence of touching the lands.

Now I'm really confused.

13 April 2008, 01:53

Clif Maloney

Well, my figures might have been off. I just rechecked the freebore AND the settings for my newly loaded catridges. My standard is a SP round I use for deer hunting. The rifles mics at .094. The deer round mics at .040 - a .054 gap. The new 90gr round mics at .092 - a difference of only .002". I'm using the RCBS precision Mic for the checks. Maybe I should seat a little more for a shorter COL and stop trying to match the Speer book. WAITAMINNIT - the Speer book indocates COl for a Speer bullet - not the Seirra bullet! The Sierra bullet get fatter soner - ergo the wide difference! I should be seating according to an optimum freebore instead....right? Next question....what is the optimum gap for a .243 rifle? Bad question....at what gap should I start from?

13 April 2008, 02:31

303Guy

For what it is worth - someone was saying that free-bore is overrated. They said this came about from bench rest shooters using minimal neck to bullet grip, making the cartridge sensitive to free-bore. ( I use unsized cases and stabilize ignition by using a wad over powder - I have no control over free-bore since my rifle's magazine is way too short. I centralise the bullet with a paper hand towel patch. Accuracy and pressure is better than with neck sizing, but more powder is required - giving a higher velocity).

A trick a gun maker told me about - blacken the bullet with candle smoke to check for contact with the lands.

13 April 2008, 02:45

Hot Core

quote:
Originally posted by Clif Maloney:
...I set up my press to seat a bullet on one shell at 2.670"....the very next one may seat at 2.659" and the next at 2.725" - it's driving me nuts! ...

Hey Clif, If you sit down at a table with a box of Bullets(not Cartridges) and your Calipers, you can get a good idea of what is going on. Measure the "length" of the Bullets and you can see that kind of variance in some brands.

Then take a Socket from your toolbox that is the largest one you have "which will not slip past the Ogive" and repeat the measuring with it slipped over the tip of each Bullet. You will find the readings are much more consistent.

Therefore, the variance is typically from the Ogive to the Tip.
-----

One of the Accuracy Keys is consistent "Ogive Distance" from the Lands, not that the Cartridges have the same Overall Cartridge Length(OCL).

However, there is an easy solution for this issue, simply convert OCL to ODL and you can forget about the issue.

Best of luck to you.

13 April 2008, 03:26

duckboat

Clif,

I'd like to second the earlier recommendation to blacken the bullet with candle smoke to find when the bullet touches the lands. You can also use a black Sharpie pen to color the bullet. Just seat the bullet long in a dummy cartridge and then try to chamber the cartridge. You will see the marks of the lands on the bullet. Then just keep trying different lengths until the marks of the lands don't show up on the bullet anymore.

Then you will know the OAL that will touch the lands. Then just seat the bullet a bit shorter than that...such as .05" shorter for your goal OAL. You need to do this for each brand and weight of bullet you use because it will be different.

Use the OAL listed in the reloading manuals as a reference, but the OAL for your cartridges will differ based your individual chamber and how long your magazine is.

13 April 2008, 09:35

swheeler

quote:
Posted 13 April 2008 02:45 Hide Post
quote:
Originally posted by Clif Maloney:
...I set up my press to seat a bullet on one shell at 2.670"....the very next one may seat at 2.659" and the next at 2.725" - it's driving me nuts! ...
Hey Clif, If you sit down at a table with a box of Bullets(not Cartridges) and your Calipers, you can get a good idea of what is going on. Measure the "length" of the Bullets and you can see that kind of variance in some brands.

Then take a Socket from your toolbox that is the largest one you have "which will not slip past the Ogive" and repeat the measuring with it slipped over the tip of each Bullet. You will find the readings are much more consistent.

Therefore, the variance is typically from the Ogive to the Tip.
-----

One of the Accuracy Keys is consistent "Ogive Distance" from the Lands, not that the Cartridges have the same Overall Cartridge Length(OCL).

However, there is an easy solution for this issue, simply convert OCL to ODL and you can forget about the issue.

Best of luck to you.

Clif; Hot Core has your answer here. If you want to know what jump each bullet is taking to the lands you can buy a comparator to check this measurement, cartridge overall length does not have to be the same for the jump to be identical. I have ammo that has a .002" variation for ogive to case head length, the same ammo has a COAL variation of .011" which I pay no attention too. Several companies make comparators, the one I have has 6 pseudo throats cut in a stainless hexagon, it checks 22,6mm,25,26,7mm and 30 cal bullets and cost less than 20.00 about a dozen years ago.

13 April 2008, 10:58

vapodog

quote:
I'm anal about my reloading and I like everything exacting: case weights, lengths, powder measures, etc...

Loosen up there guy and get over it......this will drive you nuts and you might become a Democrat or some other numbed person!

13 April 2008, 12:25

Winchester 69

quote:
Originally posted by Clif Maloney:
Without knowing if the bullet length variance is occuring at the nose or tail....I have no way of knowing if my freebore is changing.

If you are using a seater die, the variance will always occur at the nose.

Let the target tell you what is important. You will quickly shed yourself of trivial matters.

13 April 2008, 16:52

stillbeeman

As Hotcore pointed out, the variance is not from the base of the bullet to the ogive, it is from the ogive to the tip of the bullet. It is a non-facter.
You can buy yourself yet another thingie to measure stuff with or you can use the tried and true K.I.S.S. system, as posted, of blackening the bullet in a dummy round to adjust your seating die.
Write the bullet name on the side of the dummy round and keep it in case you change bullets and change your seating die and want to change back. That way you don't have to go thru the trial and error again.

13 April 2008, 17:23

Jim C. <><

In an effort to make a valid point, I'll ask, "Why are you chasing an OAL of 2.670" anyway?" What is in the manual is not magic, it's just the length the manual makers used to develop the data in THEIR RIFLE! It's no more a law for any of the rest of us to follow than are the charges they list. It all depends on our own components and rifle and ours are different from theirs.

Seat so your ammo feeds and doesn't jam into the rifleing. Develop your load and then vary the seating depth a bit and see if it helps your own accuracy. OAL variations of a few thousants aren't different, they are effectively the same.

There are no magic or secret seating numbers so it's all up to us to find what works in our gun.

RCBS doesn't make bottle necked dies in carbide.

13 April 2008, 19:13

Ol` Joe

quote:
Originally posted by Jim C. <><:
In an effort to make a valid point, I'll ask, "Why are you chasing an OAL of 2.670" anyway?" What is in the manual is not magic, it's just the length the manual makers used to develop the data in THEIR RIFLE! It's no more a law for any of the rest of us to follow than are the charges they list. It all depends on our own components and rifle and ours are different from theirs.

Seat so your ammo feeds and doesn't jam into the rifleing. Develop your load and then vary the seating depth a bit and see if it helps your own accuracy. OAL variations of a few thousants aren't different, they are effectively the same.

There are no magic or secret seating numbers so it's all up to us to find what works in our gun.

RCBS doesn't make bottle necked dies in carbide.

Yep.........

13 April 2008, 21:48

swheeler

quote:
As Hotcore pointed out, the variance is not from the base of the bullet to the ogive, it is from the ogive to the tip of the bullet. It is a non-facter.
You can buy yourself yet another thingie to measure stuff with or you can use the tried and true K.I.S.S. system, as posted, of blackening the bullet in a dummy round to adjust your seating die.

Beeman; you got something against thingies!

13 April 2008, 22:11

Clif Maloney

Thanks, guys! Your sage advice is much appreciated! Instead of focusing on COL and bullet length, I concerned myself instead with where the bullet was in relation to the lands. I was making some rookie errors in judgement - apologoes. I should have known better - I've only been reloading for 20 years so give an apprentice a break. I tried to stay too close to the Speer book not taking into account that bullet shapes and lengths differ greatly by mfr and type/weight. I must've had my head where the sun doesn't shine. This is the most perfect batch of reloads I've ever put together! Thanks again!!