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Variation on bullet length?

brccd

Hi,

Using 6.5 creedmoore Lapua shell cases, and Lapua scenar 139gr and 140ge...setting coal to 2.790...found variations in length of finished ammo by a sppread of .009. Started checking length of bullets themselves and found that this seems to be where the variation is coming in. I used up my Hornady tipped match king 140's and can't check those at the moment.

Question: Is this the usual delta spread in length in bullets? for real accuracy do you measure each bullet and group them to adjust seating to get an exact length for each finished shell and bullet seating (adjust for each bullet variation?) or is this not worth much?

Thx
 
Hmmm...variations in COAL are probably coming from your dies rather than the bullets. Think about it...assuming the bullets are all long enough to properly contact your seating stem in the first place, the stem setting determines the seating depth and overall length. If a bullet is longer than the rest, it will be seated deeper inside the case (not apparent in finished length since any extra got pushed into the case) than a shorter bullet, but should still have the same COAL since the same amount of bullet is sticking out of the case neck. The seating die, if properly adjusted, sees to that.
 
I can't speak for those bullet in particular, but with 22 cal and 168 gr 30 cal I usually get lengths varying by 0.002" - 0.004", although I've had one batch of Sierra Match Kings that had a 0.0120" length range. All measured by randomly sampling 20 bullets.

But, it's why it's best to measure length to the bullet's ogive - much better consistency. Small almost imperceptible difference in bullet-to-bullet tip ("meplat") will account for most of those length variations. Only measure overall length to ensure they fit your magazine (if applicable).
 
Yes, this makes sense. For 6.5 I have a hornady die, redding, and lee. I have an original Lee press. I will have to try the other dies and compare. I was using the hornady 6.5 match kings, with the hornady dies...seeing variations there too. What is an acceptable variation? Could it really be the press...it all seems to be pretty tight. New press? Which press is most reliable vs price! I know some are more costly than others. And work with dies I have. Using the collars on the dies, with the lee press.
 
jelenko said:
This^.

And, I thought the seater stem contacted the bullet somewhere on the ogive and not on the tip.
Click to expand...
actually I believe that is correct as well...so then the variaion in bullet length (ogive point) might appear in the overall length when completed? does this make sense? So again...one thing might be to try to group the bullets in similar lengths, and see if the legnths match when completed?
 
I just finished sorting 500 bullets by length. I will not mention the brand, but the results are typical. From shortest to longest was .019”. I was trying to get 200 the same for a match. The 200 I got ranged from 1.247” to 1.249”. The best I could do from 500 lot that I had. Those who sort bullets know that there is no perfection, and there are variations no matter what method is used. If this were not true, it would not be necessary to sort. I have discovered that, just like all other points of measurement on bullets, there can be variation on the bullet where it contacts the seating stem. Therefore, if I measure the coal of My loaded rounds, I may very well find that there is a length difference different than the .002” that I started with.

There are lots of ways to challenge Our sanity in this game :(
 
brccd said:
Hi,

Using 6.5 creedmoore Lapua shell cases, and Lapua scenar 139gr and 140ge...setting coal to 2.790...found variations in length of finished ammo by a sppread of .009. Started checking length of bullets themselves and found that this seems to be where the variation is coming in. I used up my Hornady tipped match king 140's and can't check those at the moment.

Question: Is this the usual delta spread in length in bullets? for real accuracy do you measure each bullet and group them to adjust seating to get an exact length for each finished shell and bullet seating (adjust for each bullet variation?) or is this not worth much?

Thx
Click to expand...
Over the years, I've measured various lots of SMK's and found it not unusual to get .010 to .012" variance is OAL's. Sorting them by OAL's would only be important if consistent BC is really important, AND. . . you were going to tip the bullets. If you're going to tip the bullets, you want consistent OAL's so the tipping dies give you consistent results.

When Sierra came out with their 169 SMK, which are factory tipped (well. . . they close the tips), the OAL's tend to be more consistent than SMK's before. Though their 142's I've had were good with low OAL variance.

I find consistent seating depth is more important than a bullet's OAL variation, though for ELR shooting, you really do want consistent BC's for each projectile. To start with, I want cases consistently trimmed so that their OAL's are consistent. Then, what I want from seating depth is having the bullet's base the same distance from the base of the case so that there's the same amount of bearing surface in contact with the neck's surface (at least, that's the objective).

To get consistent seating depth, I do sort my bullets by BTO. But, I do it using a comparator that makes contact on the ogive the same as where the seating stem of my seating die makes contact. I find there's there still can be significant differences in BTO's in a lot (like .006" or more, depending on the quality of the bullets). Sometimes I get a box of bullets where there's less than .003" variance (often with Berger bullets) and therefore won't sort them at all.
 
6.5 Manbun and "real accuracy" should not be used in the same sentence
I wouldn't sweat the small stuff if you shoot 1MOA with 6.5 Creedmoor you're G2G IMHO of course, there are other more accurate calibers out there where you need to pay attention to every minute detail ;)
 
COAL of cartridge measurement should be considered for mag. length.

OAL of bullet should be considered for long range target shooting.

BTO of bullet should be considered to reduce variances of bullet in the case for precision hand loading and long range target shooting.
 
Bill Norris said:
COAL of cartridge measurement should be considered for mag. length.

OAL of bullet should be considered for long range target shooting.

BTO of bullet should be considered to reduce variances of bullet in the case for precision hand loading and long range target shooting.
Click to expand...
Spot on Bill!
For competition I sort bullets by oal then resort BTO, does it make a huge difference?.. No. does it make a difference at all?… yes imo from 600 on out it helps, but will it win the match for ya?… idk! I was competing at Deepcreek maybe around 2013 and a friend of mine brought the wrong ammo for his wife’s rifle “ not uncommon for him” the ammo was so hot he had to beat the bolt open for each shot, 10 shots back then, guess who won the match?… yep not me with my perfect ammo it was Donita with not perfect ammo!
Wayne
 
Well thanks for the inputs!
I've been using these at 200 yds, and fairly consistant, but seem to occausionally have shots that might go a bit off, 1 or 2 moa. So started to wonder why, since being pretty careful trying to get exact loads, and coal measurements. One thing I did not focus on checking, as pointed out here, was the BTO of the bullet, and sorting that way, and the whole sorting thing is something only understood now! I was assuming, sierra and hornady match bullets were going to be pretty exact, but obviously not. There is a little variation on them. At some point I would like to try longer range where this would become a factor I would think.

Where I am, Long Island, I only have access to 200 yd max ranges, and would have to to make special trips like 150 mi away to find somwhere with longer ranges. So, if I can get things more controlled at 200yds, and if I some day get to one of those other places, I might have a chance of doing ok.
 
JEFFPPC said:
As usual things got a bit off base but to answer you question I sort to +or - .001 or less on base to ojive and .0001 on the tip. Made a huge difference as the yardage increases.
Click to expand...
Sorry Jeff I can’t pass up a dig on carburetor cleaning equipment. However my process is similar to yours and as I stated previously on this thread from 600 out I noticed a difference
Wayne
 
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