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Thread: Why is my COAL varying so much?

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    Member danattherock's Avatar
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    Default Why is my COAL varying so much?

    I am using Redding Deluxe 223 dies. Lapua match brass all trimmed to same (+\- 0.001) length on my Forster trimmer. Flash holes deburred, which seemed pointless on this brass, champher/deburred case mouths, full length sized, etc.. Mica and case mouth brush inside all cases before sizing. All brass being used was weight sorted and found to be within 94.5-95.5 grains, heavier and lighter brass was bagged and labeled. FYI, of 100 Lapua 'match' cases, only 67 were within 94.5-95.5 grains. Press is the rock chucker. Made 25 rounds last week for my Barnes Precision AR15, my first reloading efforts. Shot them today, got 25 more cases and repeated the same recipe for retesting.

    COAL on all twenty five 223 rounds are +\- 0.002 except for 6 rounds which were -0.007, -0.004, -0.003, -0.003, -0.005, and +0.006. Nineteen rounds were within 2.268 and 2.272, which I consider acceptable. I set my seating die up for a COAL of 2.270, which comfortably fits in my AR Stoner 10 round AR15 mags. Nineteen out of twenty five are acceptable, but the other six are further off than I want. How can I make all my reloads within +\- 0.002? Could the out of tolerance rounds account for flyers?

    Am I overthinking things that won't matter much in reality? What bugs me is two of my 5 shot groups today with 69 SMK and Varget would have been 0.5 MOA without a flyer in each group, which opened things up to a hair over MOA. My goal for this particular weapon is 1/2 MOA, so I am eager to see what role (if any) this variance in COAL may have had. My intention is to get the load dialed in then start varying seating depth in 0.010 increments searching for a sweet spot. I just started relaoding last week, but having so much disparity from round to round just seems wrong. Would appreciate any insight into the effects of said variances on accuracy, and of course would be interested in suggestions to remedy the issue. Case comparator needed, suggestions on which one? Bullet comparator needed? These are things I know very little about if applicable. I have only loaded 50 rounds and appreciate any input.



    Dan

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    One thing to keep in mind is that even though the overall length is varying a bit, the case volume is likely much more consistent. I believe it is slight variation in the ogive location of the bullets, or variations in the lead tips of some bullets that will change the measured COAL. IMO, it is not enough variation to be worried about. If you measured the OAL to the ogive point, I'd bet they are really close.

    just my opinion as a relatively new reloader myself. I'm sure if I am off base Andy or Murphy or someone else with a lot of experience will chime in.

    Just out of curiosity, are you checking bullet runout on your reloaded ammo? With all of the care you are taking in you reloads, I think that is as or more important than some other stuff..

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    COL is most critical at the ogive when concerning accuracy. Obviously OAL is critical for function, but for accuracy I don't worry about the odd few thousandths runout due to meplat differences. The ogive on most match bullets is such that normal bullet seaters will often rest on the tip/meplat of the bullet, not the ogive. That is always bad juju. I'd check the seating stem for contact and procure a proper stem if that is the issue. Redding is easy to deal with for such things and ogive seating bliss is but a phone call away.
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    Thanks for the info on the dies. Hadn't thought about that yet.


    As for bullet run out, not sure what the best tool is, but have heard enough about it it want to learn more. Any suggestions on tools. For that matter, what kind if runout is acceptable. What amount effects accuracy.



    Dan

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    I had a similar issue, and I noticed a significant variation from bullet to bullet. I now sort them all and measure from the ogive using a bullet comparator. I also sent Forester a couple bullets and they cut me a custom seater.
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    Quote Originally Posted by 1Cor15:19 View Post
    COL is most critical at the ogive when concerning accuracy. Obviously OAL is critical for function, but for accuracy I don't worry about the odd few thousandths runout due to meplat differences. The ogive on most match bullets is such that normal bullet seaters will often rest on the tip/meplat of the bullet, not the ogive. That is always bad juju. I'd check the seating stem for contact and procure a proper stem if that is the issue. Redding is easy to deal with for such things and ogive seating bliss is but a phone call away.
    Yes what he said but a more direct answer to your question “why is my COAL varying” is that bullets very in shape. Just using calipers on the nose will give you quite a variation in numbers because the seating plug doesn’t care where the nose is, it’s a cone contacting farther down the bullet.
     
    Measuring COAL off the nose is fine but expect variations of something like +/-.005" and that's not an issue for most reloading. But if are hunting MOA decimal points you want X” off the lands to be truly known and repeatable, then you need to be both seating and measuring at the ogive.
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    Quote Originally Posted by danattherock View Post
    Thanks for the info on the dies. Hadn't thought about that yet.


    As for bullet run out, not sure what the best tool is, but have heard enough about it it want to learn more. Any suggestions on tools. For that matter, what kind if runout is acceptable. What amount effects accuracy.



    Dan
    Look at Sinclair's online catalog for bullet runout tools. Sinclair has all the tools for accuracy you'll need.

    http://www.sinclairintl.com/reloadin...ools/index.htm

    Frankly, shooting an AR platform, if you're getting less than 1 MOA, I'd be happy. Keep playing with all the tools of bench rest accuracy - for fun. At the accuracy levels you're looking for, you should be shooting a bolt action. It would give you more consistent feedback.

    Look around the http://www.6mmbr.com/index.html website. You'll find tons of good reloading/shooting tips. In particular, register and post questions on the forum section:

    http://forum.accurateshooter.com

    Like everyone else has said, your COAL isn't as important as the ogive to lands measurement, because the "bullet jump" to the lands should be consistent and it is a better measure of position of the bullet in the case, i.e. to ensure consistent case volume below the bullet base.

    There have been tests done where the bullet tip is deformed and then shot for accuracy. At 100 yards, there were only negligible increases in group size. At much longer distances, it does open up significantly. There are devices sold to uniform bullet tips for long range shooting (say at 600 yards and greater):

    http://www.6mmbr.com/bulletpointer.html

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    Moderator stid2677's Avatar
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    Here is a video of my 325wsm in a runout jig.

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    A cheap and easy way to check for run out is to stand all your loaded rounds as tight as you can neatly, then take a picture with a digital camera, get the image up on your monitor and look at it "magnified".

    Typically I can't "see" runout with naked eyes until I have a bullet .005 or .006 off center. They say .001 and .002 are fine, at .003 you need to look at your process.

    I have the RCBS case master gauging tool that can measure bullet runout, but I am not especially fond of it.

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    I use the Hornady tool Stid is using in the video, I like it because you can find the run-out then fix it and re-check right on the same tool.
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    Thanks for the insights and video. Looks like I need to buy another reloading accessory. Dayum

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    Quote Originally Posted by 1Cor15:19 View Post
    COL is most critical at the ogive when concerning accuracy. Obviously OAL is critical for function, but for accuracy I don't worry about the odd few thousandths runout due to meplat differences. The ogive on most match bullets is such that normal bullet seaters will often rest on the tip/meplat of the bullet, not the ogive. That is always bad juju. I'd check the seating stem for contact and procure a proper stem if that is the issue. Redding is easy to deal with for such things and ogive seating bliss is but a phone call away.

    I think this guy makes some good points……. You first step is that you need to look to see if your die is seating properly by the ogive of your chosen bullets…..
    All this Match type prep is great and well worth the education you will get out of it…..however it is currently a inflated market for componants and I am afraid you will see high prices and a limited selection for such things. Especially considering your chosen platform

    I agree with others that consistent Sub MOA groups with any semi auto platform is hard to achieve… you might get a good 3 or 5 shot 0.5 group (here and there) but doing it consistantly with that platform is going to be difficult….

    In my experience with a AR style platform you are usually limited by magazine length long before fine tuning the COAL really starts making a notable difference in accuracy. With this style rifle your never going to push up close to the lands and maintain Mag length. Therefore you're never going to achieve the consistent Pressures, velocity and bullet stabilizing effect that bench rest shooters are seeking when they do this. If your rounds won't fit in the Mag…. this defeats the purpose of having a semi auto.

    I would recomend trying a multitude of match grade factory ammo in this rifle …just make sure its the same bullet weight your interested in reloading. Then be sure to shoot over a chronograph. when you find a round your rifle likes and groups to your expectations you now have a benchmark for your hand-loads.

    Just some food for thought….. All reloader's and especially (hand-loaders) have their own opinions. All rifles have their own personalities. Thus my experiences will never be more then generic to you... its fun to see who's methods and combanations work best…. and this is the reason we have competition.

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    Any trimmer that holds the case at the base will not give you as excellent results as trimmers that hold the case in a chamber-like die because the bases aren't perfectly perpendicular to bore. See CH4D.com for their trimmers.

    As has been said, the base to ogive length is what is important. See Wilson seater dies.
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    Quote Originally Posted by Nitroman View Post
    Any trimmer that holds the case at the base will not give you as excellent results as trimmers that hold the case in a chamber-like die because the bases aren't perfectly perpendicular to bore. See CH4D.com for their trimmers.

    As has been said, the base to ogive length is what is important. See Wilson seater dies.
    And you would think this same school of thought hold true for run out gauges like the hornady model in that video….. Its a strange design I haven't seen before the way it rotates the bottom of the case to keep the bullet square and measure the run out……..Im sure some engineer at hornady has this figured out…..im just having trouble wrapping my head around it right now.

    I was always of the school of thought the best way to fix run out was prevention……… seems to me to push the bullet square in the case neck like that (after the bullet is seated) is treating a symptom more then curing anything…….. doing this seems like it would certainly affect neck tension to me… don't bother turning the necks i guess.

    Id need to shoot some groups and experiment before i was sold on it…….proof is in the pudding

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    Just because a trimmer holds the case head in no way means it’s inaccurate. My RCBS holds the head by the rim but indexes the case at two points as far apart as possible, basic machining principles. X-axis is indexed from theend of the case head while both Y/Z-axis are indexed on the pilot bushing inside the neck. It would be better if Y/Z were picked up on both ends for concentricity but just by letting it turn in the holder as I let the lever clamp it gets pretty dang close. Yea you can get a case in there out of whack, non concentric, indexing points can’t have burs/bumps/extractor dings sticking out . . . any tool is only as good as the operator but I can hold as close as calipers will measure all day with even a cheap Lee trimmer.
     
     
    Bullet concentricity.
    They never seat that way consistently no matter what dies you use or how you set them up, you just don‘t see it unless you have a way to measure a couple thousandths. Roll them on the bench all you want and you will never see .005” out, heck a plywood bench is at least .03” pre foot out and I can’t see it on my garnet inspection block that is certified .0005” per foot flat. Yes large dings on a case rim can effect your measurement in the Hornady tool but a .001” misalignment of a 30-06 case head would only be something around .0002” out of concentric way out at the neck. Of coarse correcting the concentricity will effect neck tension but correcting .005 to .001 means moving the bullet .002 at most. ½ the distance due to measuring a diameter. You’d need some very sophisticated equipment to measure the minuscule change in bullet tension, I bet there would be a lot more variation in pull tension case to case than correcting .005” would cause.
     
    Does all this stuff matter to accuracy? Yup but I doubt very much individually in reality however cumulatively the little stuff sure adds up. The value of it all though is reducing the variables so that we spend less time chasing our tails figuring out if this load is truly better than that. Keeping things as consistent as possible except for the thing you intend to change helps us believe what we intended to change was the cause of the effect we got
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    Thanks for the thought provoking dialogue guys. Good stuff and my gears are turning. Finally got a few days off and looking forward to honing my 69 SMK load tomm. Got 5 powder weights to shoot of Varget. Hope to find a clear favorite of the 5 loads I made. Would be nice if the wind lays down for a change. Picked up a pound of CFE223 at a gun show last week. Also had my buddy buy me an 8 pound jug of H335 at the LGS today as I was working and he ran across it. With just a few bullets and powders on hand, I can already see that load development could take a while. But I am really enjoying the process. Something about it is very appealing, thinking, strategerizing, what ever it is, sure is fun.

    One thing I could use a bit of insight on, of all the variables, what role does bullet seating depth have on accuracy. Curious when to interject experimentation with this aspect. My thought now is to use Lapua brass, trimmed to within 0.001, weight sorted to within a grain, then vary powder to cover Varget range on 69 SMK (23.5-25.5). Find a clear favorite tomm with luck. Hypothetically if 24 grains is best group, then do 23.7, 24 again just to verify, and 24.3. Then on the best grouping go to 0.1 grains of powder on either side to select final load of powder. After that I planned on varying seating depth to fine tune the load. My 10 round AR Stoner mags will accept 2.285 (or so) COAL. Folks say 2.250 is the norm. So I figured I could do three batches of like charged loads and vary seating depth by 0.010" (2.250-2.280) in hopes one might outperform the others.

    Then I read recently that changing brand of primer could change things. Using Winchester but have some CCI 400's and LGS has Federal in stock. So much to consider with my limited insights. Is my approach towards load development sound or am I going about things wrong. Pretty significant investment in time and dough. Wondering how you guys go about working up a load. Thanks for any input you may offer.


    Dan

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    Quote Originally Posted by ADfields View Post
    Just because a trimmer holds the case head in no way means it’s inaccurate. My RCBS holds the head by the rim but indexes the case at two points as far apart as possible, basic machining principles. X-axis is indexed from theend of the case head while both Y/Z-axis are indexed on the pilot bushing inside the neck. It would be better if Y/Z were picked up on both ends for concentricity but just by letting it turn in the holder as I let the lever clamp it gets pretty dang close. Yea you can get a case in there out of whack, non concentric, indexing points can’t have burs/bumps/extractor dings sticking out . . . any tool is only as good as the operator but I can hold as close as calipers will measure all day with even a cheap Lee trimmer.

    If i were to play devils advocate….I would argue that all these points are fine and dandy ones….However how does that same brass sit square in your rifles chamber? is it supported by the same axis points as your trimmer? Because if not theres no way to prove that its square in your trimmer the exact way it is in your chamber……..
     
     
    Bullet concentricity.
    They never seat that way consistently no matter what dies you use or how you set them up, you just don‘t see it unless you have a way to measure a couple thousandths. Roll them on the bench all you want and you will never see .005” out, heck a plywood bench is at least .03” pre foot out and I can’t see it on my garnet inspection block that is certified .0005” per foot flat. Yes large dings on a case rim can effect your measurement in the Hornady tool but a .001” misalignment of a 30-06 case head would only be something around .0002” out of concentric way out at the neck. Of coarse correcting the concentricity will effect neck tension but correcting .005 to .001 means moving the bullet .002 at most. ½ the distance due to measuring a diameter. You’d need some very sophisticated equipment to measure the minuscule change in bullet tension, I bet there would be a lot more variation in pull tension case to case than correcting .005” would cause.
     
    Once again i find it a bit interesting that you find the need to push the bullet square in the case neck to alleviate 2 thousands of run … yet your quick to write off this same exact effect is going to have on neck tension…. You have no way of measuring how great this effect is…..not anymore then you can measure any effect your run out is going to have for accuracy ... so saying minuscule is at best an assumption….


    Does all this stuff matter to accuracy? Yup but I doubt very much individually in reality however cumulatively the little stuff sure adds up.

    Yes it does…. However without a way to measure how much each variable is effecting your results….nor a way to check the results of your theoretical fix …all your doing is just adding another variable to an already lengthy equation.

    The value of it all though is reducing the variables so that we spend less time chasing our tails figuring out if this load is truly better than that. Keeping things as consistent as possible except for the thing you intend to change helps us believe what we intended to change was the cause of the effect we got
    I agree with that 100 percent…..


    you know as well as i do…..there is no way for me to argue with you rather or not your right or wrong….nor do I want to. The only real world Tangible results I can see is to shoot groups over a crony….and see if any of those variables seem to make a notable and repeatable difference.
    Im not saying that hornady tool is bad nor am I saying your methods or flawed……But I am saying I have reloaded a lot of high quality SUB-MOA Ammo without that tool.
    Years and Years before that hornady tool was on the market a lot of guys just used a board with a hole drilled into it to bend the bullet in the case neck… trying to fix the runout. so this Idea is not new…..
    Nor is my school of thought that the most important factor is neck tension….My reasoning is that run-out can be prevented with quality seating dies good press operating technique and quality components..
    Most of my careful reloads don't have enough runout for me to worry with to begin with……and if they do I start checking my technique.

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    Seating depth is always a factor, and it can always show tangible results…..however in my experience with any semi auto platform these results are not as profound as they are when you are fine tuning up next to the lands on a bolt gun. Theres nothing wrong with playing with your AR15 to see what works best….However there is a reason bench rest shooters and trained snipers us bolt guns and not AR15's. if your looking for real world repeatable results for SUB-MOA accuracy theres no substitute for a custom bolt gun shooting fine tuned reloads.

    In my experience theres no such thing as a true Sub-MOA AR15 rifle…..sure you can get good groups here and there…but repeating these results on demand with 100 percent confidence is another story….

    In my opinion I would enjoy my rifle…. shoot the hell out of it and concentrate on the basics of marksmanship….don't concentrate on trying to make a platform that was engineered to be 2-3 MOA fighting rifle into something it was never intended to be…especially in this market.

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    More so than my posts reflect, I agree. Just trying to squeeze all the accuracy I can out of this gun, which is capable of sub MOA results. Mostly doing this as an exercise of sorts to learn good reloading practices. Just using it on an AR15 as it is the new toy so to speak. Already shot a 0.826 ten shot group. Curious what the potential is, but again, mostly just enjoying learning about reloading accurate ammo. Plan to buy a Savage long range precision model 12 in 260 Remington next. A good 500-1000 yard gun for some long range practical rifle competitions (bipod only) up in the mountains of Virginia. Trying to develop some accurate reloading techniques as it will matter more with the next venture than my AR. Sure do appreciate the input here.



    Dan

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    Quote Originally Posted by stid2677 View Post
    Here is a video of my 325wsm in a runout jig.

    That's some nice, tight ammo!


    BTW, Dantherock, I forgot if you've said before, what type of chamber do you have? Is it the Wylde chamber, 223, or 5.56 NATO? If you have one of the longer chambers, definitely load up some longer bullets and seat them close to the lands to really see what your gun can do. I'd start with the Sierra 80 and if you can stand the price, try some Bergers. Obviously these will be single loaded, but generally you'll see noticeable increases in accuracy. I think you said you have a faster twist barrel (7.7 or 8?) so the longer bullets will stabilize well.

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