OAL and TTL IMPoRTANCE??

[jcooper1389]

im fairly new to reloading and i have a few questions

How important is the Overall Length of a fully completed round?

How important in the Trim to Length?

Can there be a .001" variation between brass?

EX> .243 should be 2.025"OAL with HDY 65gr Vmax and sometimes i mess up and seat the bullet to 2.024 or 2.023..i also shave .001" too much sometimes while trimming.

Long Question

I had 10 rounds all perfect TTL and when i seat one bullet perfect my logic tells me that i shouldnt have to adjust the seating die and just push em through but sometimes its off and the bullet is seated too far already.why is this happening?

How Precise does all the measurement have to be to keep consistency..obviously if theyre all the same itll be consistant but if i have the .001-.002 difference does that have an effect??

 

[boomtube]

How important is the Overall Length of a fully completed round?

Not much, if any, if the load is well developed. There's a window of good shooting OAL that's often as much as 15 thou wide. Seat in the middle and most common variations will have no effect.


"How important in the Trim to Length?"

It isn't. All that's important is the chamber length and that is usually 20 thou or more than the max case length.


"Can there be a .001" variation between brass?"

Easily.


"EX> .243 should be 2.025"OAL with HDY 65gr Vmax and sometimes i mess up and seat the bullet to 2.024 or 2.023..i also shave .001" too much sometimes while trimming."

There is no "should be" about it, all a book OAL gives is the length the testers used to develop the listed data in their own rigs. It's no more a rule for us to blindly follow than their listed powder charges.


"I had 10 rounds all perfect TTL ..."

I've been doing this since '65 and have to guess what your definition of a TTL is.


"...when i seat one bullet perfect my logic tells me that i shouldnt have to adjust the seating die and just push em through but sometimes its off and the bullet is seated too far already.why is this happening?"

Irrelivant variations in bullet construction can easily cause 10 thou or more OAL variation to the meplat but no rifle cares where a bullet point hangs in space, all they care about is the jump to rifling contact. That's why many of us use some kind of 'bullet comparitor' to measure length from head to ogive.


"How Precise does all the measurement have to be to keep consistency..obviously if theyre all the same itll be consistant but if i have the .001-.002 difference does that have an effect??"

Such tiny variations rarely mean anything at all unless you and your rig and your load are highly accurate and even then not unless you're right on the ragged edge of the good shooting window.

 

[jcooper1389]

I've been doing this since '65 and have to guess what your definition of a TTL is.
.

Trim to length

That's why many of us use some kind of 'bullet comparitor' to measure length from head to ogive.


.

might be a dumb question but whats is a bullet comparitor and what is the ogive?

So if my trim to length is 2.035 and my just fired rounds are at 2.040 or as long as 2.045 do i have to trim them?

 

[boomtube]

A "comparitor" is short for the tool or device we use to (comparitively) measure fired/sized CASE length from head to shoulder OR for bullet seating from head to (or very near) the bore diameter. Examples are RCBS' Precision Case Mics, Hornady and Sinclair's "case headspace" tools made to be mounted on the jaws of a precision caliper, and Innovative Technologies excellant diameter adjustable tool that uses a digital dial indicator mounted on a small stand; do a web search for the company sites to see examples. They all do the same thing and are equally accurate in what they do but they vary a bit in cost and how easy/fast they are to use.

"Ogive" (pronounced "OH-jive") is the entire tapered bullet surface from body diameter to the meplat (point). Most of us loosely refer to ogive in seating as that point at which the bullet first contacts the rifling, ie, a .308" bullet is supposed to make contact on the ogive where the diameter is .300".

I thought maybe your TTL was trim-to length but that's not a standardized term and I hate guessing when dealing with a specific issue.

 

[Bart B]

Irrelivant variations in bullet construction can easily cause 10 thou or more OAL variation to the meplat but no rifle cares where a bullet point hangs in space, all they care about is the jump to rifling contact. That's why many of us use some kind of 'bullet comparitor' to measure length from head to ogive.

Note that with rimless bottleneck cases (and some belted bottleneck ones) that chamber easily, the spread in head to shoulder measurement will also be imparted to the bullet's jump to rifling contact. Shorter ones have less bullet jump, longer ones less. Such cases have their shoulders pressed hard into the chamber shoulder when the round fires.

And, depending on how much shoulder setback there is from firing pin impact slamming the case shoulder into the chamber shoulder, that dimension will be subtracted from the bullet jump to rifling distance. The case head's off the bolt face a few thousandths when this happens.

It's an absolute mishmash of things that's impossible to control to very small tolerances. But in the most accurate rifles, it doesn't seem to matter one bit.

 

[boomtube]

"Note that with rimless bottleneck cases (and some belted bottleneck ones) that chamber easily, the spread in head to shoulder measurement will also be imparted to the bullet's jump to rifling contact. Shorter ones have less bullet jump, longer ones less." Etc....

Not real sure I understand all of what you're saying but I think I agree. ?? Anyway, all that seems like pretty esoteric info for a guy just getting started; I just wanted help Cooper understand the basic answers to his questions.

 

[jcooper1389]

lol yea...no idea what any of that is...am i ok reloading the way i am by just slammin em in my dies and making sure the measurements are close?? im trying to make a .243 load that gives at most 1" GROUPS at 200...havent found that yet...any suggestions

 

[boomtube]

"im trying to make a .243 load that gives at most 1" GROUPS at 200...havent found that yet...any suggestions "

No suggestions here. I fact I've tried to find that myself for some 40 years with a Weatherby Vangard in .243 but haven't made it yet, not even close. You will find that sub .5 MOA rifles - and reloads and scopes and shooters - are a lot more common on the net than on the range. But I can guarantee you that it won't be found by anyone "...reloading the way i am by just slammin em in my dies..." no matter how precisely you cut your case lengths and seat your bullets.

Good luck!

 

[Red hunter]

what you are doing will eventually get you there IF you and the rifle are capable of it.
Consistency is the game. This is basically what they are trying to tell you. Small variations from the book data are fine as long as every piece of brass you use are ideally identical to one another.
The OAL diferencences you are seeing are due to the way your seater die applies pressure to the bullet face and the inherent differences in the shape of the bullet from manufacturing. A bullet comparator is a tool that will measure all of your bullets to the exact same place where a set diameter is. With this tool you measure all your bullets and seperate them into groups that are the same. After doing this you will notice very little to no OAL difference.
A bullet's shape is pointed and tapers to your bore dia. and it is very consistant but not exact and this is where your seater die pushes the bullet into the case not at the tip. If you take your die apart you will see how this works and will understand it a little better.
1/2 moa is good goal but a few more tools and and a few different powders and bullets will prob be needed.
Start with what you have, work up a load in 1/2 grain increments till you see pressure signs. take your best group and try a few different seating depths to try for an improvement.

Hope this helps.

 

[jcooper1389]

LOL Boomtube..when i said slammin them in my dies i was simply referring to reloading not actual procedure

and thanks red helped out alot

 

[Bart B]

The OAL diferencences you are seeing are due to the way your seater die applies pressure to the bullet face and the inherent differences in the shape of the bullet from manufacturing. A bullet comparator is a tool that will measure all of your bullets to the exact same place where a set diameter is. With this tool you measure all your bullets and seperate them into groups that are the same. After doing this you will notice very little to no OAL difference.

A bullet's shape is pointed and tapers to your bore dia. and it is very consistant but not exact and this is where your seater die pushes the bullet into the case not at the tip. If you take your die apart you will see how this works and will understand it a little better.

I've never heard of a bullet having a face. Their surface from their maximum diameter to their tip's commonly (and properly) called the ogive. And it goes from the point to the barrel's groove diameter, not the bore diameter.

As the metalurgy of both the bullet jacket and core determine their exact dimensions when formed by the ogive pointing die when they're made, there will be small tolerances. A few thousandths spread in over all length of a loaded round caused by these tolerances are added to the tolerances in shoulder position I mentioned earlier. Sierra Bullets tests their bullets for accuracy with several thousandths spread in the combined effects of both. And they have no problems getting 1/4 MOA accuracy at 200 yards with their best bullets. They're not alone in this regard; other reloaders do as well. Good commercial 30 caliber match ammo has ever greater tolerances in these area and it'll shoot about 1/2 MOA at 300 yards in good rifles.

 

[Red hunter]

Sometimes an answer is given with terms that may be over a persons understanding and a little simplification helps. I am about positive if I broke down a BTU of energy into Jules and explained how this effects the latent heat of cooling you would be lost as a ball in high weeds. I fully understand this subject since it has been my business for almost 30 years. When I explain it to someone new in the field more basic terms can bring about enlightenment. This was my intentiontions. Face /surface, if you want to nit pic technicalities of termonology fine show us all how big your brain is and confound us with your intelligence and always always point out how much inferior I am to you.

 

[Bart B]

I fully understand this subject since it has been my business for almost 30 years. When I explain it to someone new in the field more basic terms can bring about enlightenment. This was my intentiontions.

If you use words like intentiontions. with two "shuns" at its end instead of one like the rest of us (and later in your post, two always back to back), you're showing us how much bigger by a factor of 2 your brain is and enlighten us with your intelligence and always point out how much inferior we are to you. (I'm winking.......)

 

[Red hunter]

Well I am glad I could help you with your Napolean complex. I will gladly help in any way I can. Please check all of my posts I am sure there are other things I have mis spelled or stated. Please proof for propper punctuation I am sure there are plenty of mistakes there also.