bullet bear surface,ogive and seating depth....

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12-14-2014, 07:33 PM
LongRange

bullet bear surface,ogive and seating depth....

Friday night i started thinking about the thread that hafejd30 started "140g amax scare"was the title i think...anyway i grabbed a hand full of 142g smk and started measuring random bullets touching the lands and was very supprised by what i found. The measurements were all over the place from 2.275 all the way up to 2.285 over 25 bullet. I took the same bullets and measured the bearing surfaces and separated them and came up with 3 sizes .580 .590 and .593. I then remeasured the length of each bullet touching the lands twice using the hornady tool and heres the results from the 142g SMKs...
Bullets with .580-.582 bearing surface measured 2.276 off ogive
Bullets with .589-.591 bearing surface measured 2.278 off ogive
Bullets with .593-.595 bearing surface measured 2.284 off ogive

I also took 25 139g lapua bullets and was surprised again when all 25 measured .634 bearing surface and all 25 measured 2.307 + or - .001 which ill chalk up to me and the hornady tool which we all know is not perfect.

Its almost like the ogives are different on the smks...im going to call sierra in the morning and ask them about this and see what they say.
Ive also got a few 140g hornady im going to check this week. I always sort bullets by bearing surface and check every round i load off the ogive but ive never check the sorted bullets ogive to lands but i guess im going to start now.

So whats your guys thoughts on this?
12-15-2014, 01:36 PM
gotcha

Not unusual measurements for the SMK's. If you think that's a big spread try measuring another box from a different lot #. Lately, with the huge back-log in bullet making I've seen Bergers that don't measure consistently either. I've switched to Scenars and have had the same experience as you. In my experience the Lapua Scenars don't have the best B.C.'s but, man do they shoot :)
12-15-2014, 05:59 PM
LongRange

Quote:

Originally Posted by gotcha

Not unusual measurements for the SMK's. If you think that's a big spread try measuring another box from a different lot #. Lately, with the huge back-log in bullet making I've seen Bergers that don't measure consistently either. I've switched to Scenars and have had the same experience as you. In my experience the Lapua Scenars don't have the best B.C.'s but, man do they shoot :)

yes they do...as far as BC goes the 139g has a advertised BC of 578..the 142smk say 595 above 2850fps and 580 at 2850 and below..the 140 beger hybrid claims 618 the 140 berger vld claims 612 and the 140 berger LR target claims 592...personally i can give up a little BC for a more consistent bullet and besides i will most likely never shoot well enough to tell the difference between a 578BC and a 618BC bullet anyway LOL!

also i just got off the phone with sierra's tech dept...at first i played stupid...well maybe not played...anyway after a few minutes i started asking how the difference would effect accuracy and why are the bullets so off..he said its just part of the process...which i understand we dont live in a perfect world..but what is causing the bullets to be so off...is the ogive in a different place from bullet to bullet? at which point he corrected me saying its pronounced ojive...then said its part of the process and that everyone should sort bullets.anyway long story short he didnt have an answer to any of my questions...he was polite as was i but leaves me wondering how many new reloaders chase their tails trying to figure out why they cant find a consistent load due to small things like this...IMHO it should say on their site and/or on the box some thing like "bearing surfaces vary and may effect seating depth,we recommend sorting by bearing surface for best accuracy".
12-15-2014, 06:39 PM
yobuck

Quote:

Originally Posted by LongRange

yes they do...as far as BC goes the 139g has a advertised BC of 578..the 142smk say 595 above 2850fps and 580 at 2850 and below..the 140 beger hybrid claims 618 the 140 berger vld claims 612 and the 140 berger LR target claims 592...personally i can give up a little BC for a more consistent bullet and besides i will most likely never shoot well enough to tell the difference between a 578BC and a 618BC bullet anyway LOL!

also i just got off the phone with sierra's tech dept...at first i played stupid...well maybe not played...anyway after a few minutes i started asking how the difference would effect accuracy and why are the bullets so off..he said its just part of the process...which i understand we dont live in a perfect world..but what is causing the bullets to be so off...is the ogive in a different place from bullet to bullet? at which point he corrected me saying its pronounced ojive...then said its part of the process and that everyone should sort bullets.anyway long story short he didnt have an answer to any of my questions...he was polite as was i but leaves me wondering how many new reloaders chase their tails trying to figure out why they cant find a consistent load due to small things like this...IMHO it should say on their site and/or on the box some thing like "bearing surfaces vary and may effect seating depth,we recommend sorting by bearing surface for best accuracy".

Yes and it should also say weight may/will vary so while your at it check that also. Then theres the tips, ever notice how lousey those tips are? Well theres help for that also in that
a special tool is available called a (megplate trimmer). Im gonna spring for one of those right after i recover from having my barrel frozen for proper molecule alignment.
12-15-2014, 07:24 PM
JTCrl

Quote:

Originally Posted by yobuck

Im gonna spring for one of those right after i recover from having my barrel frozen for proper molecule alignment.

Don't forget that only works during the Vernal Equinox in a leap year and on right hand twist barrels it must be done in the southern hemisphere.:bolt:
12-15-2014, 07:30 PM
BillPa

Go back and read my post on the batch of 6.5 Nosler BTs where about half of the box measured .570" and the rest between . 583"-.586" ogive to heel like so....
http://i43.tinypic.com/6nxn4n.jpg

You can't measure from the base, they can vary as much as the tips at times. You may also notice I make my own inserts or steel sleeve the aluminum ones, both bored .002" under the shank diameter. I check the lengths of the cartridges the same way.
http://i43.tinypic.com/f0zsrp.jpg

The insert on the casehead is bored exactly .100" deep and square. It eliminates any casehead runout in the measurement and insures a consistent placement in the calipers without twisting and turning and adjusting to get the number I want to see.

Bill
12-15-2014, 10:45 PM
LongRange

Quote:

Originally Posted by yobuck

Yes and it should also say weight may/will vary so while your at it check that also. Then theres the tips, ever notice how lousey those tips are? Well theres help for that also in that
a special tool is available called a (megplate trimmer). Im gonna spring for one of those right after i recover from having my barrel frozen for proper molecule alignment.

Yeah i have noticed the tips and do own a meplat trimmer and i also weigh my macth bullets...let us all know how your cryogenic barrel freezing works out for you.
12-15-2014, 10:51 PM
LongRange

Quote:

Originally Posted by BillPa

Go back and read my post on the batch of 6.5 Nosler BTs where about half of the box measured .570" and the rest between . 583"-.586" ogive to heel like so....
http://i43.tinypic.com/6nxn4n.jpg

You can't measure from the base, they can vary as much as the tips at times. You may also notice I make my own inserts or steel sleeve the aluminum ones, both bored .002" under the shank diameter. I check the lengths of the cartridges the same way.
http://i43.tinypic.com/f0zsrp.jpg

The insert on the casehead is bored exactly .100" deep and square. It eliminates any casehead runout in the measurement and insures a consistent placement in the calipers without twisting and turning and adjusting to get the number I want to see.

Bill

Ive read your post and i measure my bullets the exact same way you do but with the 26 inserts....and id be interested in a couple of those case head inserts if you sell them.
12-15-2014, 11:32 PM
Steelhead

Quote:

Originally Posted by LongRange

Ive read your post and i measure my bullets the exact same way you do but with the 26 inserts....and id be interested in a couple of those case head inserts if you sell them.

As would I.
12-16-2014, 10:56 AM
yobuck

Quote:

Originally Posted by LongRange

Yeah i have noticed the tips and do own a meplat trimmer and i also weigh my macth bullets...let us all know how your cryogenic barrel freezing works out for you.

Well i was joking of coarse but the fact is that was all the rage also about 20 years back. And yes i had the barrel on my 30x378 done back then.
Didnt make any difference at all as far as i could tell. Who knows, maybe the barrel sat in a corner and then got shipped back if it was ever even sent.
All this stuff is fine and depending on individual mindset can be very important. But for a hunter shooting ridge to ridge across a wide windy valley
into a tree covered sidehill it means very little. The ones who wont agree are also the ones whove never tried it. Out of box good bullets in the right
hands will win every time.
12-16-2014, 04:02 PM
LongRange

Quote:

Originally Posted by yobuck

Well i was joking of coarse but the fact is that was all the rage also about 20 years back. And yes i had the barrel on my 30x378 done back then.
Didnt make any difference at all as far as i could tell. Who knows, maybe the barrel sat in a corner and then got shipped back if it was ever even sent.
All this stuff is fine and depending on individual mindset can be very important. But for a hunter shooting ridge to ridge across a wide windy valley
into a tree covered sidehill it means very little. The ones who wont agree are also the ones whove never tried it. Out of box good bullets in the right
hands will win every time.

LOL yeah i figured you was.