Achieving OAL Consistency

Originally Posted By: Chris623This is all fascinating to me. With this rifle, I'm loading my first jacketed bullets. 99.9% of the bullets I've loaded in my life were lead.......with flat meplats. No problem setting things to a fixed OAL. But registering that measurement off the ogive is totally new to me. I've a lot to learn, guys.

I'm trying to load my rounds to an OAL of 2.314". Trying to get my rounds as close to the lands as possible............at least for my first tests. Then I'll drop back .005" at a time until I find an OAL that gives good results. The only magazine on the market that will hold that round is an ASC magazine. The longest round they will hold is a 2.316".............but Gred told me to load my rounds to 3.214" because trying to make them closer would be a nightmare. Now I see what he meant.


It would be best to use the right terminology to lessen confusion. COAL or AOL is the distance between the base to the tip. The only reason you care about this is to make sure it fits in your mag or to make sure the bullet has enough neck grab.

The one you are talking about is CBT0 (cartridge base to ogive). This measurement is a comparative measurement to determine how far you want to set your bullet back from the lands. Or forward if you want to jam em in.

I dont know why COAL/OAL is used to replace CBTO but it is by many when referring to rifle data. With pistols its not that important to differentiate. But for rifles with all the vld and other pointy bullets we have now, the only thing COAL is useful for are the 2 things mentioned. And as already noted, alot of plastic tipped bullets vary in length.
 
Originally Posted By: tesoroOriginally Posted By: Chris623This is all fascinating to me. With this rifle, I'm loading my first jacketed bullets. 99.9% of the bullets I've loaded in my life were lead.......with flat meplats. No problem setting things to a fixed OAL. But registering that measurement off the ogive is totally new to me. I've a lot to learn, guys.

I'm trying to load my rounds to an OAL of 2.314". Trying to get my rounds as close to the lands as possible............at least for my first tests. Then I'll drop back .005" at a time until I find an OAL that gives good results. The only magazine on the market that will hold that round is an ASC magazine. The longest round they will hold is a 2.316".............but Gred told me to load my rounds to 3.214" because trying to make them closer would be a nightmare. Now I see what he meant.


It would be best to use the right terminology to lessen confusion. COAL or AOL is the distance between the base to the tip. The only reason you care about this is to make sure it fits in your mag or to make sure the bullet has enough neck grab.

The one you are talking about is CBT0 (cartridge base to ogive). This measurement is a comparative measurement to determine how far you want to set your bullet back from the lands. Or forward if you want to jam em in.

I dont know why COAL/OAL is used to replace CBTO but it is by many when referring to rifle data. With pistols its not that important to differentiate. But for rifles with all the vld and other pointy bullets we have now, the only thing COAL is useful for are the 2 things 7mentioned. And as already noted, alot of plastic tipped bullets vary in length.


I suspect the CBTO can't be measured by the average guy with his tools on the bench because he doesn't know how. Also since loading manuals don't give it any mention most guys might not have a clue to it's importance. I didn't for many many years. Sometimes new loaders over think this and old loaders over sell it. There's been many a dead PD produced and many a sub-MOA group shot without all of our scientific gyrations.

Greg
 
Doesn't a seater set the ogive to the same place each time, assuming technique is the same? If you've found the setting where a particular bullet performs, why would a few thousandths of tip variation matter?
 
Originally Posted By: MerditDoesn't a seater set the ogive to the same place each time, assuming technique is the same? If you've found the setting where a particular bullet performs, why would a few thousandths of tip variation matter?

Yes.

It doesn’t.

*
 
[/quote]
I suspect the CBTO can't be measured by the average guy with his tools on the bench because he doesn't know how. Also since loading manuals don't give it any mention most guys might not have a clue to it's importance. I didn't for many many years. Sometimes new loaders over think this and old loaders over sell it. There's been many a dead PD produced and many a sub-MOA group shot without all of our scientific gyrations.

Greg [/quote]

I hear ya. When I started in the 70's my 'CBTO gauge' was candle smoke!

So its time for Chris to move past the basics as he stated he does have a quest to load for accuracy!

First of all need to get a Hornady bullet seating comparator and casing. Hornady calls it an 'OAL' gauge instead of a CBTO gauge to add to the confusion! 50 bucks max. While at it might as well get a gauge and holder to set the headspace as only 15 bucks.

Here is a good simple video on the how for the bullet seating:

However to build an accurate load for his 223 cal chosen bullet he should first set the bullet setback to ie .020 and then shoot batches at 200yds from max load down in ie: .5gr increments. One range of those batches will shoot the tightest groups as it is in tune with the barrel vibration created by the bullet firing. Once that optimal powder weight (velocity) is determined, then its time to find out what bullet setback in ie: .005 increments will increase or decrease the group size with that velocity. Of course need to monitor pressure signs while doing that. When completed he will have his pet load for the rifle.

There are many other things involved with accuracy reloading but its good to start with the above to optimize the bullet performance for the barrel. And then if one wants to go further then can deal with case uniforming, neck tensions, bullet runouts etc etc!

None of it is that complicated and for some it makes reloading more interesting and rewarding!





















 
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Originally Posted By: tesoro
I suspect the CBTO can't be measured by the average guy with his tools on the bench because he doesn't know how. Also since loading manuals don't give it any mention most guys might not have a clue to it's importance. I didn't for many many years. Sometimes new loaders over think this and old loaders over sell it. There's been many a dead PD produced and many a sub-MOA group shot without all of our scientific gyrations.

Greg [/quote]

I hear ya. When I started in the 70's my 'CBTO gauge' was candle smoke!

So its time for Chris to move past the basics as he stated he does have a quest to load for accuracy!

First of all need to get a Hornady bullet seating comparator and casing. Hornady calls it an 'OAL' gauge instead of a CBTO gauge to add to the confusion! 50 bucks max. While at it might as well get a gauge and holder to set the headspace as only 15 bucks.

Here is a good simple video on the how for the bullet seating:

However to build an accurate load for his 223 cal chosen bullet he should first set the bullet setback to ie .020 and then shoot batches at 200yds from max load down in ie: .5gr increments. One range of those batches will shoot the tightest groups as it is in tune with the barrel vibration created by the bullet firing. Once that optimal powder weight (velocity) is determined, then its time to find out what bullet setback in ie: .005 increments will increase or decrease the group size with that velocity. Of course need to monitor pressure signs while doing that. When completed he will have his pet load for the rifle.

There are many other things involved with accuracy reloading but its good to start with the above to optimize the bullet performance for the barrel. And then if one wants to go further then can deal with case uniforming, neck tensions, bullet runouts etc etc!

None of it is that complicated and for some it makes reloading more interesting and rewarding!
[/quote]

Well said. Chris and I have been conversing for going on three/four months on all these issues. Slowly he's sucking me dry of four decades of my acquired knowledge.
smile.gif


Greg
 
Originally Posted By: fw707Originally Posted By: FirehandOriginally Posted By: Sniper66I'm no expert, and it may not be a big difference, but primer seating depth may also play a role. I uniform all my primer pockets, but still notice variation even with CBTO.

This was an issue i had. Drove me nuts for a hour until I figured it out.

How does primer seating depth affect the length of a round?

If you use a dummy round (no primer) to measure and set your seater then load live rounds, if your primer isn't seated fully your measurements (CBTO or COAL) will now be longer. Like I said, I'm no expert and may be looking at this the wrong way, but I've seen it and have to adjust my seater accordingly.
 
I just grabbed 6 new Hornady 204 brass,using the Hornady .330 headspace comparator, I marked the length on the brass minus primer. With brass marked so I could measure positioned the same,I primed the brass and measured again. I found 0-.003 increases, so at least with this small sample of new brass there are differences in primer pockets. A Lee hand primer was used to seat to firm stop on the cases. If I can free up time I will "uniform" some new brass and see if there is a different result. In the past I have uniformed pockets after a couple firings. Primers were CCI br4.
Just tried a second set of 6 more brass.
Using Rem 7.5 primers 5 out of six were 0-.0015 longer. 1 toggled from .0015 to .002 longer than unprimed brass length.
 
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So... Help me understand. The way I'm reading it, you guys are seating primers, proud of the case head?

That can not be right. NOBODY does that. I would hope not, anyway.

But if the primers are not protruding, and therefore affecting these measurements, how can the measurements be any different regardless of primer present or not? Properly seated primers simply can not effect an OAL or head space measurement. They just can't.

Unless the primers are sticking out?????

Nobody leaves primers sticking out like that. So I'm having a hard time wrapping my head around what you guys are saying.

If, by some crazy chance, both of you actually are seating primers like that - stop it. And go back to square one. You have much more important and basic lessons to learn than worrying about consistent OAL.

Did I just read somebody adjusting a seater to accommodate protruding primers affecting OAL??? I swear to gawd, I think I just read that???????

- DAA
 
Originally Posted By: DAASo... Help me understand. The way I'm reading it, you guys are seating primers, proud of the case head?

That can not be right. NOBODY does that. I would hope not, anyway.

But if the primers are not protruding, and therefore affecting these measurements, how can the measurements be any different regardless of primer present or not? Properly seated primers simply can not effect an OAL or head space measurement. They just can't.

Unless the primers are sticking out?????

Nobody leaves primers sticking out like that. So I'm having a hard time wrapping my head around what you guys are saying.

If, by some crazy chance, both of you actually are seating primers like that - stop it. And go back to square one. You have much more important and basic lessons to learn than worrying about consistent OAL.

Did I just read somebody adjusting a seater to accommodate protruding primers affecting OAL??? I swear to gawd, I think I just read that???????

- DAA


You said it way better than I could!

lol.gif
 
Originally Posted By: fw707Originally Posted By: DAASo... Help me understand. The way I'm reading it, you guys are seating primers, proud of the case head?

That can not be right. NOBODY does that. I would hope not, anyway.

But if the primers are not protruding, and therefore affecting these measurements, how can the measurements be any different regardless of primer present or not? Properly seated primers simply can not effect an OAL or head space measurement. They just can't.

Unless the primers are sticking out?????

Nobody leaves primers sticking out like that. So I'm having a hard time wrapping my head around what you guys are saying.

If, by some crazy chance, both of you actually are seating primers like that - stop it. And go back to square one. You have much more important and basic lessons to learn than worrying about consistent OAL.

Did I just read somebody adjusting a seater to accommodate protruding primers affecting OAL??? I swear to gawd, I think I just read that???????

- DAA


You said it way better than I could!

lol.gif


me too. i have been rolling my eyes and shaking my head through this entire thread.
 
Originally Posted By: DannoBooneI use one of these to get COAL:
https://www.sinclairintl.com/reloading-e...-prod83792.aspx

Like has been said above, the only time I pay any attention to
OAL is to make sure rounds fit in the magazine, or when fire
forming in which case, it doesn't matter that much...not going
for pinpoint accuracy.

I seem to remember a short video on another forum by a nationally known shooter about how inaccurate the holes in that particular comparator are. Of course I can't find it!
 
Originally Posted By: newmexkid
I seem to remember a short video on another forum by a nationally known shooter about how inaccurate the holes in that particular comparator are. Of course I can't find it!

Inaccurate compared to what? And how would it matter?

That's a mighty fine and useful little tool. Works great for measuring shoulder bump/head space too.

- DAA
 
Well I measured primer pockets on more new brass, then the Br4 cups. The cups are minus 3-.004 of the pockets. Now I'm like what the heck is going on, took the Lee hand prime apart,there is a flat spot worn into the connector. I put 2 layers of gorilla tape on the connector. Seated and Re-measured the previously primed brass all measure to unprimed brass measurements. Grabbed a 2nd digital caliper and measured primers, .003-.004 below base. This is a good example how asking and sharing on a good forum can be very helpful. I had never thought to measure stuff that I had checked out years ago, never thought I could have worn out my hand primer.
 
Originally Posted By: fw707Originally Posted By: DAASo... Help me understand. The way I'm reading it, you guys are seating primers, proud of the case head?

That can not be right. NOBODY does that. I would hope not, anyway.

But if the primers are not protruding, and therefore affecting these measurements, how can the measurements be any different regardless of primer present or not? Properly seated primers simply can not effect an OAL or head space measurement. They just can't.

Unless the primers are sticking out?????

Nobody leaves primers sticking out like that. So I'm having a hard time wrapping my head around what you guys are saying.

If, by some crazy chance, both of you actually are seating primers like that - stop it. And go back to square one. You have much more important and basic lessons to learn than worrying about consistent OAL.

Did I just read somebody adjusting a seater to accommodate protruding primers affecting OAL??? I swear to gawd, I think I just read that???????

- DAA


You said it way better than I could!

lol.gif

No disrespect to anyone, but you guys are thinking way too big on this. I'm not talking protruding so much that it affects function, is dangerous, or just doesn't look right. I agree, if anyone is loading that way, its wrong and needs to be corrected asap. My pockets are uniformed and my primers are seated flush, visually and by feel, but there is just enough "protrusion" to give an ever so slightly longer measurement (usually .001-.002) than with a measurement of case minus the primer. Could be my press or hand primer, but it's not something that caused me concern so much that I question shooting the ammo. May not be the problem the OP is experiencing, just adding my $.02. I'll stay out of the conversation now.
 
Originally Posted By: Sniper66Originally Posted By: fw707Originally Posted By: DAASo... Help me understand. The way I'm reading it, you guys are seating primers, proud of the case head?

That can not be right. NOBODY does that. I would hope not, anyway.

But if the primers are not protruding, and therefore affecting these measurements, how can the measurements be any different regardless of primer present or not? Properly seated primers simply can not effect an OAL or head space measurement. They just can't.

Unless the primers are sticking out?????

Nobody leaves primers sticking out like that. So I'm having a hard time wrapping my head around what you guys are saying.

If, by some crazy chance, both of you actually are seating primers like that - stop it. And go back to square one. You have much more important and basic lessons to learn than worrying about consistent OAL.

Did I just read somebody adjusting a seater to accommodate protruding primers affecting OAL??? I swear to gawd, I think I just read that???????

- DAA


You said it way better than I could!

lol.gif

No disrespect to anyone, but you guys are thinking way too big on this. I'm not talking protruding so much that it affects function, is dangerous, or just doesn't look right. I agree, if anyone is loading that way, its wrong and needs to be corrected asap. My pockets are uniformed and my primers are seated flush, visually and by feel, but there is just enough "protrusion" to give an ever so slightly longer measurement (usually .001-.002) than with a measurement of case minus the primer. Could be my press or hand primer, but it's not something that caused me concern so much that I question shooting the ammo. May not be the problem the OP is experiencing, just adding my $.02. I'll stay out of the conversation now.

http://bulletin.accurateshooter.com/2016/01/primer-seating-depth-uniformity-and-accuracy/


“”Primer Seating Depth — Why Uniformity is Important
The first concern is for safety: for that reason, primers should be seated below flush with the case head. One primary cause of “slam fires” (which includes catastrophic failures from firing out of battery) is “high,” or protruding primers. These stand above the case head, are readily felt with simple finger-tip inspection, and may fire when slammed by the bolt face and/or a floating firing pin in feeding.

Here at the USAMU, we ensure our rifle primers generally run -0.003″ to -0.005″ below the case head. Maximum primer depth is -0.006″ and minimum is -0.002″. Upon inspection, any cases with high primers will be corrected before loading. Aside from improving ballistic uniformity, ensuring the primers have proper compression upon seating also helps reduce possible misfires. These can be caused by the firing pin’s expending part of its energy either seating the primer or having to deform the primer cup enough to reach the anvil.“


Whatever works for you!
thumbup1.gif
 
If your primers are affecting case length measurement you are not getting them seated enough. Like said they need to be below flush! Flush is not good enough! Your playing with fire allowing this to continue in your loading practices.
 
My pockets are uniformed and my primers are seated flush, visually and by feel, but there is just enough "protrusion" to give an ever so slightly longer measurement.

PROTRUSION IS NOT FLUSH! THAT IS LIKE SAYING I'M A LITTLE PREGNANT! PRIMERS ARE EITHER FLUSH OR BELOW RIM. IF THEY ARE'NT THEN THERE WILL BE TROUBLE AT ONE TIME OR ANOTHER.
 
^^^^ That's a PITA.

I'd rather track down the source and eliminate it. Than treat the symptom in a hopeful rather than clear and direct manner. Yeah, rotating definitely can help, but eliminating the need to is how I prefer to approach it.

- DAA
 
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