Frustrated - I need help with my OAL measurements!

[ace of hearts]

I have been trying to up my reloading game for 6.5 Creedmoor, generally following the recommendations in the reloading for long range stickies above. I am having trouble getting repeatable measurements from the Hornady OAL gauge.
People talk about seating bullets ".001 in. off the lans", but my measurements of each trial seating using the Hornady OAL gauge with Hornady comparator insert frequently vary by 3 - 5 thou. On top of that when I test seat different bullets from the same box (or even just reseat the same bullet) I get an additional 5 thou spread. It seems to me that measuring overall length using comparators leaves some room for play with the angle at which the bullet and case align in the micrometer, and that in turn affects to OAL measurement. Also the slight pressure differences and alignment used while seating the bullet in the lans with the gauge cause some variability in OAL. I have read some posts where people simply average the discrepancies to find their theoretic OAL, however averaging a spread of 8 thousandths makes a claim like "I am seating .001 off the lands" statistically silly.
I have a nice Mitutoyo micrometer and have checked the zero.
I am using the 140 amax
I work in a field demands a high level of manual dexterity and precision, and I do not think that I am "ham fisting" these measurements.
I am using the 6.5 modified case from Copper Creek (Hornadys are backordered)
So what do you think, is a measurement spread of say 8 thousandths (3-4 between measurements, and an additional 4-5 between different bullet seatings) typical, or have I screwed something up?

Thanks for any advice

 

[Grizzdude]

It might be the bullets themselves, I use the same Hornady ogive comparator for berger bullets and they are pretty dead on from base to ogive, but the tips vary by a lot. They all seat to within .001"

 

[Nate O.]

Are your loads compressed? Is your chamfer right on the mouth? Consistent neck tension?

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[ace of hearts]

Are your loads compressed? Is your chamfer right on the mouth? Consistent neck tension?

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Thanks for your reply, but just to clarify...

I am just referring to the measurement of OAL using the Hornady OAL gauge. I can seat the bullets just fine to any length I want, I just am not sure what OA length to target. The Hornady system that I am using has a "modified case" that is caliber specific and does not accept powder nor is it made to be chamfered etc.

Thanks to all

 

[pmclaine]

Okay you are using your desired bullet in the Hornady case drilled and tapped for use with the OAL gauge. You are not measuring actual rounds produced from your press.

Using that tool there are variables - how hard did you seat the bullet to the lands, how wacky was your seat into the comparator to measure ogive length. You are measuring ogive length? COAL really doesn't mean anything.

Try this.

1. Using the prepared case with your bullet take 5 measurements pushing the bullets into the lands. Try to duplicate the force used to jam the bullet. The force should be light but equal each time you do it. Hornady recommends a finger flick to the back of the push rod. I just kind of lightly seat by feel. Average the 5 measurements and call it good. If you want to be more anal take 10 measurements. If you want to be OCD take 20. This average will be the max length to Ogive for your chamber.

The Hornady tool is good. I like it better than an RCBS precision mic.

When you actually seat your rounds in a case that has the proper neck tension you will find that your length to Ogive will be consistent and you can set your seater up to achieve that perfect .10 or whatever you want off the lands. There is no law that says .10 will be the best. Your rifle will tell you where you should be at.

 

[Nate O.]

Yup sorry..just scanned your post too quickly and thought you were getting inconsistent seating depth.. i know little about the system you're using, but you could sacrifice a piece of brass and try this. With a dremel or similar, make 2 cuts down the neck, 180 apart, to the shoulder. Then insert the bullet of choice, making sure there's just enough neck tension to hold the bullet. Then carefully chamber,extract and measure. I've had very consistent results this way.

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[svxwilson]

Push hard enough so there is enough pressure to get it stuck in the rifling when you remove the tool. I use the brass end of the bore snake to pop the bullet out. That is the deepest measurement. I then give a slightly smaller amount of pressure just under the getting stuck. This measurement is usually .001 less.
I was having the same results as you until I figured my method out. I measures hundreds of times till I found this consistency.

 

[Nate O.]

Since we're talking about measurements down to the .001, wouldn't it be better to index the measurement off of the bolt face, rather than shoving a piece of brass in up to the shoulder and indexing off of it? I'm probably wrong, but I think when I chamber a live round, the shoulder should be clear from contacting the chamber, if FL sized and not just necked.

 

[briscoetab]

I am by no means an expert on this subject and have not found a need to use the oal tool to get my seating depth measurement, so I have no experience with this tool. I do have a method to get head to ogive but I don't use the oal tool.

As far as the inconsistent measurements I think for the purpose you are talking about taking an average would be ok. To me this measurement is just a starting point for seating your bullets. As long as your measurements are within a .002-.004 I think you would be ok with taking an average. To me the important measurement is your actual seating depth, which should consistently be within .001. As long as you have a starting point that you can refer to as your bullet touching the lans I think you are good.

 

[Fuzzball]

"I have read some posts where people simply average the discrepancies to find their theoretic OAL, however averaging a spread of 8 thousandths makes a claim like "I am seating .001 off the lands" statistically silly."

Agreed, seating/jump gets more thoughtful web BS than most subjects. I get lots of chuckles when people quote their seating depths to ANY specific depth in thousanths from the lands. Few skilled machinists can detect that kind of precision on things like copper jacket spitzer bullets going into a tapered rifling lead.

My experience leads me to believe any decent rifle and properly developed loads will tolerate individual round to round jump variation from 5 to as much as 10 thou with no visible efect on targets. MOST rifles and common bullets will shoot best with jumps in the range of 20 to 50 thou (and sometimes more than that) so striving to obtain 1 thou of jump is not only hopeless, it's pointless.

All "averaging" any measurements can do is pretend the samples aren't so poorly done. Averaging poor work does not improve it. Keep trying to develop your bullet-to-lands contact feel until you can get your range of variations smaller. Then work on the shortest OAL/deepest seating data point, it's probably going to be the closest to "kissing" correct. All you really need is a decent fixed point to start seating experiments by slowly seating to longer jumps anyway. Then, when you KNOW what shoots best, you will be measuring from head to ogive of the ammo so it hardly matters if your best shooting depth is exactly 26 or 27 thou off the lands, does it?

(Apoligise if I've offended any precision seating experts here. I guess.)

 

[briscoetab]

Fuzzball, pretty much agree with what you were saying, but I think taking an average for this purpose would be ok.

I don't agree with taking averages for most precision measurements but in this case it would seem ok for the exact reasons you mention. Many of us don't have the skill or tools to determine what the actual measurement to the lands is. On top of that you are usually just looking for a jump that best works in your rifle like you said. So if you are not getting the real measurement anyways as long as the measuments you are getting are close you would be ok.

To the op I understand what you are saying about the bullet comparator but once you start taking all your measuments with it in the same way you should not have any variations. I always align the one jaw just below the primer pocket, since the hornaday comparator is slightly offset when installed. I always apply pressure till the dial stops moving then release pressure. I do this 3 times and make sure I get same measurement, if not I realign bullet and start over.

So if you have a measurement that is close to the right measurement to start from you would be ok.

The way I get my starting measurement is to take a empty case and seat a bullet a little long and color the bullet with a black sharpie, then chamber the round. If it is hard at all to close remove round and seat bullet a little further. You should see where the coloring touched the lands. I keep seating the bullet till you can barely tell the bullet touched the lands, then make very small seating adjustments. The measurement before all marking on bullet disappear is what I call kissing the lands. I do this 2 maybe 3 times and typically am within .002. I do not know if this is the most accurate method, it certainly is not the fastest but it works for me. You have to recoil or the bullet between each time you chamber it and pay close attention to any markings.

I think you could use this method in combination with the oal gauge to double check yourself. If you already have the measurement with oal gauge it should be pretty quick since you should not have to seat the bullet but a couple of times to tell if the oal gauge measurement is correct.

 

[Rattler56]

Thanks for your reply, but just to clarify...

I am just referring to the measurement of OAL using the Hornady OAL gauge. I can seat the bullets just fine to any length I want, I just am not sure what OA length to target. The Hornady system that I am using has a "modified case" that is caliber specific and does not accept powder nor is it made to be chamfered etc.

Thanks to all

It takes a little time to get the feel of the OAL gauge to get it just right, try 10 times and through out the longest and shortest, add the eight up
and divide the total by eight.
This gives you a starting point, now seat a bullet in a case, take a marker and mark the bullet, this will show you if your touching the lands.

 

[briscoetab]

Rattler 56, that's what I was trying to say, you made that sound so much simpler than I did.

 

[damoncali]

Seating exactly .001" off the lands *is* statistically silly. Try that, and you'll get some stuck. Bullets aren't that consistent. You're thinking straight. It's a tough measurement to get.

This is one reason benchest shooters order a chamber stub with a new barrel (a short piece of barrel that the gunsmith runs the reamer into - it contains just the shoulder and the beginning of the rifling. With that setup, when the barrel is newish, using very consistent bullets, you can gut the variance down quite a bit because measurement is quite a bit easier using dykem or smoke or a microscope or whatever. But fiddling with gages and whatnot with an assembled rifle has it's limitations.

 

[MDF99]

I grew frustrated with the Hornady tool as well; too much movement and unwieldy when combined with Sinclair "nut" to get consistent ogive measurements

I went to the Tresmon setup but used a piece of brass rod and rod stops from McMaster Carr. Also using the Davidson from Sinclair holder/comparator setup that attaches firmly to calipers.

It's a superior setup IMO.

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[briscoetab]

MDF99 I am going to get me one of those comparators, it definitely looks easier to use. Been planning on getting something like it but keep forgetting.

 

[MDF99]

I was going to buy Sinclair brand comparator but they were out of stock at time in my size so I went with Davidson setup. Later I bought a pair of the Sinclair comparators and holders to use for measuring bullet bearing length per Tresmon. The Sinclair had burrs at entrance and I had to sand and polish them a bit so they wouldn't scratch bullets. Davidson was good to go out of package. Here's pic of Sinclair (7mm) after polish.

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[ace of hearts]

I grew frustrated with the Hornady tool as well; too much movement and unwieldy when combined with Sinclair "nut" to get consistent ogive measurements

I went to the Tresmon setup but used a piece of brass rod and rod stops from McMaster Carr. Also using the Davidson from Sinclair holder/comparator setup that attaches firmly to calipers.

It's a superior setup IMO.

Sent from my iPhone using Tapatalk

That holder/comparator looks awesome, thanks for the tip.