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I've been loading pistol cartridges for about 6 years now. I've just entered the rifle cartridge world with the .223. I have a question on COAL, particurly what is an acceptable variance.
Details:
[Press] - I have a 550B, but decided to pick up a single stage press as I didn't like that slight movement in the toolhead of the 550 when seating the bullets. So I'm loading on an RCBS R2.

[Die] - RCBS

[Brass] - All once-fired Winchester brass

[Powder] - CFE 223

[Bullet] - Sierra 63gr SP Varminter

First loads developed with OAL at or near 2.250, powder 25.6gr to 26.4gr. Chrono results, if I remember correctly the FPSs were in the 2600 to 2800 range.
Hodgdon's web site listed a COAL at 2.20, so I decided to seat them a little deeper than my first loads of 2.250 and chrono them.
[Side note] - the first batch was loaded on the 550 and I saw varied OAL, thus the reason for the SS purchase.

My target COAL for this batch was 2.235. Shorter than the 2.250, but not quite 2.20. I loaded 10 round batches and would see OAL ranging from 2.225 to 2.236. Is this a normal variance? What would cause this if everything (dies) are locked down? Would the SP lead tip contribute to this?

The rounds would be cycled through an AR magazine. Being that I'm a NYer and that ARs are evil assault weapons, this question is all hypothetical of course as I am a law abiding citizen and would never buck what the loving govt. determines what is in my best interest.
 

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You will get variances due to different bullets. You will also get differences based on the speed you move the press arm down. I can change my COAL just by bringing the ram up faster. That range seems a little high, but not astonishing, to me at least.
 

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.110 is not an acceptable tolerance. something ifs wing with your set up some where. are you seating and crimping with the same die or separately? Fwiw my rifle loads vary very little, about .005
 

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Load it out as far as you magazines and rifle chamber will let you. That has always resulted in the best accuracy for me.
 

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How is your shoulder setback compared to the fired cases?
 

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Kind of depends on what kind of accuracy you want out of the rounds. Better consistency means smaller groups, but if .011 OAL variance produces groups that are good enough, then go with it.

It could be the bullet shape is not well suited to the stem in your seater die which is causing the variance.

If you are coming from the pistol cartridge world where small seating depth changes can cause pressures to jump dramatically, you can relax for the most part. For most bottlenecked rifle rounds, as long as the bullet is not jammed into the lands, seating deeper in the case with a published load will generally not effect pressures nearly as much as a pistol round.
 

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I was just loading 5.56, and I was getting some OAL variance, it was killing me. then I realized something. It was the lead SP tips just chipped away etc compared to the FMJ's.

Don't forget the tip is probably flat, slightly missing etc, so that soft point is going to give skewed results. It's like like a FMJ that can be very close.

At, least that's a theory right?
 

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You might want to use Sierra's information in this case.
Sierra loads their accuracy loads with this bullet at 2.250.

http://accurateshooter.net/Downloads/sierra223ar.pdf

Given that you have everything tight and a decent press and dies with the right seating bushing you should not be getting more tan 5 thousands of a inch spreads. But in the end .010 OAL differences mean very little in this type of load, let me explain why. Bullets are not uniform when measuring from the tip. Specially soft tips with exposed lead have the greatest variances.
When aiming for consistency and accuracy one should use a bullet bushing / comparator tool. Synclair has a nice one. The hornady is also a decent product not too expensive. You can also improvise using a case of the next lower caliber in this case 22 cal and cutting a portion from the neck down to achieve the same relative measure using the lower neck as the taper stop for the bullet, but there is no substitute for the actual bushing. When you use the brand name you can then use published information and take the reference as reliable.

Hornady's system...



Synclair's bullet comparator


In any case another reason soft points are not the greatest for accuracy is because specially in autoloaders the tips can get so deformed that impact the trajectory, and even more so in light bullet calibers.

So for the practice load I would just extract the average from 10 loads and approximate to Sierras recommended 2.250. Then from there adjust +/- if needed for extra accuracy in your specific barrel and write absolutely everything down. If there is a load you love leave a couple of dummy cartridges made to use as reference. I have one reference cartridge for every bullet and barrel combination. Sometimes the same bullet between accuracy load and hunting / hot load.

Another thing that helps A LOT is a soft crimp even w/o canelure. One needs to go very light w/o deforming the bullet but this
is one of the best and easy ways to assure consistent starting pressure and minimize the risk of bullet offset. Not so much w/o the canelure but the starting pressure shows in the spreads, that sometimes, if you follow everything by the book, they are in the single digits.
 

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Remember unless to trim all cases back to minimum there will be case length variation which also can contribute to some oal variation. As long as my cases run below max length and my round is short enough to fit in mag ( I simply seat bullet so oal of cartridge is the same as a usgi 556) will work fine
 

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case lenght after trimming has no impact on COAL. If you have canelure then the COAL has to be reduced to meet the canelure on the right spot.
I order to do that you have to lower the seating bushing in the seating die. That is the only thing that makes the COAL shorter.
 
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