How much variation in OAL is acceptable?

[CharlieTN]

I've done a good bit of searching but mostly get answers from benchrest shooters which are beyond my ability and equipment at this time.

I'm loading a Hornady 178BTHP in .308 and my C.O.L. measured off of the Ogive is 2.139. However I started loading a box of bullets from the same lot number and with the seating die setup the same I was getting 2.150. Kind of caught me as odd so I checked the overall length measured off of the tip and they both come in at 2.810. I also measured the bullets themselves from the ogive. The bullets that give me C.O.L. of 2.139 measure .687 while the bullets that give me a C.O.L. of 2.150 measure .701 (a difference of .014).

Is this enough of a variance to be concerned? I haven't shot the odballs yet to see how they do but will do that Saturday.

Normally I'm only shooting to 200 yards but was planning on shooting these at an upcoming 1000yd f-class shoot at the end of the month.

Thank you,

Charles

 

[ksthomas]

Charlie,

Need some clarification on the terminolgy here, in re the COL and the ogive measurment. If we're talking COL (or OAL), then .014" is perfectly normal and about what I'd expect. Most bullet makers will have at least this much variation within the same lot, nothing at all unusual about that. Seating these off the ogive, the measurments obtained by checking ogive, should yield a much smaller number. Depending on the compaitibility between ogive and the profile of the seater stem, I'd expect that this should drop down to no more than .002" or .003", regardless of how much variation you're seeing in OAL.

 

[damoncali]

Are you saying the bullets in a a different box of the same lot are measuring 14 thousandths longer as measured from the base to the ogive, and doing so consistently?

 

[ksthomas]

Not base to ogive, base to meplat. That's fairly typical of several types of bullets. Unless there was a serious screw-up by an operator, the base to ogive measurement shoulod be within just a few thou at most.

As far as the OAL of individual bullets, yes, I've seen .015" and more off bullets coming off the press consecutively. Differences in jacket material amounts of lube from one to the next can easily account for that much change.

 

[CharlieTN]

Are you saying the bullets in a a different box of the same lot are measuring 14 thousandths longer as measured from the base to the ogive, and doing so consistently?

Yes, that is what I found. Bought 3 boxes of these bullets, all from the same lot. First box gave me ammo measured off of the ogive of 2.139" oal with a bullet measured from base to ogive (using the Hornady bullet comparator) of .687. Started loading the second box and using the seating die set up the same (had not removed the die from the press) and proceeded to get a oal measurement of 2.150 for the entire box, measured off the ogive.. These bullets measured from the base of the bullet to the ogive at .701. The 3rd box has not been loaded yet but the bullets measure from the base to the ogive the same .687 consistently, the same as the first box. Both loads measured from tip to base a consistent 2.810 which is what caught my attention at first. Made me go back and check my measurements several times to make sure it was stupid operator error.

I just found it funny the difference between the boxes in the same lot. Yet the bullets in each box are consistent for that box.

These measurements were taken using the Hornady electronic calipers which have shown to be accurate and consistent so far and using the bullet comparator to measure off the ogive. I do apologize if my terminology is incorrect. Hope this has clarified.

I'm curious to see how the bullets that measure longer off the ogive shoot any differently than those measured shorter off the ogive.

 

[damoncali]

That's weird. That sounds like a large variance in the bullets. But what's weirder is that your seater managed to produce significantly different OAL's measured off the ogive. You'd think that the longer bullets would just be seated further into the case, since the seating operation defines the distance from bullet ogive (as defined by where the seater contacts the bullet) to case head. You would have to have the seater contact the bullets in very different places for the seating OAL (that is, the OAL as defined by case head to seater-ogive) to be constant, but the measured OAL (Case head to gage ogive) to be off by .014.

 

[SPAK]

I've found up to .012" base to meplat variance in the same box of match bullets.... Base to ogive variance was smaller but was still there. Ill have to go back and remeasure to be sure of the actual variance.. Most of the time, if I've properly selected a good powder charge in the middle of a node, +/- .005" doesn't change anything significantly on the target for me...

I have sorted bullets before by base to tip and base to ogive length and found it a waste of time of my needs..... If I was shooting benchrest that might be a different story....

 

[abizdafuzz]

Yes, that is what I found. Bought 3 boxes of these bullets, all from the same lot. First box gave me ammo measured off of the ogive of 2.139" oal with a bullet measured from base to ogive (using the Hornady bullet comparator) of .687. Started loading the second box and using the seating die set up the same (had not removed the die from the press) and proceeded to get a oal measurement of 2.150 for the entire box, measured off the ogive.. These bullets measured from the base of the bullet to the ogive at .701. The 3rd box has not been loaded yet but the bullets measure from the base to the ogive the same .687 consistently, the same as the first box. Both loads measured from tip to base a consistent 2.810 which is what caught my attention at first. Made me go back and check my measurements several times to make sure it was stupid operator error.

I just found it funny the difference between the boxes in the same lot. Yet the bullets in each box are consistent for that box.

These measurements were taken using the Hornady electronic calipers which have shown to be accurate and consistent so far and using the bullet comparator to measure off the ogive. I do apologize if my terminology is incorrect. Hope this has clarified.

I'm curious to see how the bullets that measure longer off the ogive shoot any differently than those measured shorter off the ogive.

I can believe this if the seating stem is like mine. I have found that my Forster Mic-Seater stem touches the bullet at a different height than my Hornady Comparator bushing does. And if the bullets have different shapes then I have seen big variances between bullets seated w/o touching the die. I think this is because if the 2 different diameters that I'm using are at changing heights then one of the measurements will be off compared to the other bullets.

 

[Jedi]

@1k the biggest variable is wind

IF you can shoot the difference then it may be a concern, realistically very few can

the more you measure the more variance you will see, load em and shoot. Worry more about wind call and driving rifle correctly

Alot of folk weight sort brass/bullets, ck run out etc etc
and cant read wind or drive rig correctly

Learn the wind, learn your rig, follow thru shot correctly
these will have more impact on your shooting than fretting over a couple of thou in bullet measurements

Shoot more, measure less

 

[CharlieTN]

That's weird. That sounds like a large variance in the bullets. But what's weirder is that your seater managed to produce significantly different OAL's measured off the ogive. You'd think that the longer bullets would just be seated further into the case, since the seating operation defines the distance from bullet ogive (as defined by where the seater contacts the bullet) to case head. You would have to have the seater contact the bullets in very different places for the seating OAL (that is, the OAL as defined by case head to seater-ogive) to be constant, but the measured OAL (Case head to gage ogive) to be off by .014.

I'm using the basic RCBS die set and can see a distinct mark well forward of the Ogive where the die is pushing on the bullet so it doesn't surprise me that I'm getting the same oal measured off the tip yet different oal measured off the ogive. What blew me away was how consistent each box was yet how different one box was from the other 2 in the same lot.

 

[CharlieTN]

@1k the biggest variable is wind

IF you can shoot the difference then it may be a concern, realistically very few can

the more you measure the more variance you will see, load em and shoot. Worry more about wind call and driving rifle correctly

Alot of folk weight sort brass/bullets, ck run out etc etc
and cant read wind or drive rig correctly

Learn the wind, learn your rig, follow thru shot correctly
these will have more impact on your shooting than fretting over a couple of thou in bullet measurements

Shoot more, measure less

Thank you. I will be shooting to 1000yards for the first time at the end of the month so was sure if it would make that big of a diffference. I suspected it wouldn't give my lack of stellar ability.

Wind has definitely been my focus as where I shoot now wind is basically a non factor. This match will be a crash course in wind reading.

Thanks to all for the info and responses. As always, a very helpful group.

Charlie

 

[oldfatguy]

I've done a good bit of searching but mostly get answers from benchrest shooters which are beyond my ability and equipment at this time.

I'm loading a Hornady 178BTHP in .308 and my C.O.L. measured off of the Ogive is 2.139. However I started loading a box of bullets from the same lot number and with the seating die setup the same I was getting 2.150. Kind of caught me as odd so I checked the overall length measured off of the tip and they both come in at 2.810. .......

Thank you,

Charles

Measure the same from the tip? Sounds like your seating die is seating on the meplat, not the ogive.

OFG

 

[CharlieTN]

Measure the same from the tip? Sounds like your seating die is seating on the meplat, not the ogive.

OFG

I'm beginning to think the same thing. Might be time to upgrade the seating die a bit.