Bearing Surface

[bdale]

I'm giving up on the Bullet base to ogive measurement and going to start measuring the Bullet bearing surface and was curious how much variation you guys are separating your respective lots by. ???

 

[dkhunt14]

Happy veteran's day BDale. I don't think plus or minus 1 would hurt you. Matt

 

[Joe R]

You know I thought about doing that kind of measurement, but then I asked myself: "How can I buy my way out of another useless detail?" The answer was pretty obvious, buy better bullets.

Labor specialization is what has enables us to advance as a species. It is the cornerstone of human progress.

Kindest regards,

Joe

 

[Scott Harris]

Base to ogive provides similar data to total bearing surface measurement in my experience. Either one gives good info. I've seen huge differences between lots of bullets regardless of brand: .040"+ with some Berger lots for example. Within the same lot, some have been really good and only varied by .004-.005" total over several thousand samples. Other lots have varied by .010"-.015". I think measuring is useful for 1K shooting....not so much for 600 yards and in. We shoot a lot of bullets in a year and have measured tens of thousands from Sierra, Hornady, and Berger. Based on my experience, each manufacturer has good lots and bad lots, that's why we measure. Once sorted, the bad lots get turned into good lots

I believe variance within a lot occurs when multiple different machines are used to produce bullets but they are still considered the same lot. Seem to recall someone talking to Berger about this and not sure whether Berger is going to change how they label lots.

 

[bdale]

I was measuring bullet base to ogive and getting 2 to 4 thousands variation and then measured the true bearing surface of the same bullets and got 10 to 15 thousands variation so i think measuring the bearing surface will be the best way to sort, was just curious how much variation those with more experience doing this found exceptable for their respective lots ???

 

[bdale]

Happy veteran's day BDale. I don't think plus or minus 1 would hurt you. Matt
[/quote





Thanks dkhunt14

 

[noload]

I've never spent much time on measuring bearing surface, When I did give it a try I measured from the bottom of the boat tail to the ogive. When I come up with a different measurement, I did not know if the actual bearing surface was different or maybe the boat tail itself was the problem. I've tried 2 ogive gages and measured between them eliminating the boat tail. I just couldn't trust that either cause the diameter difference at the BT shank. Just a little out of round in that area will skew the results.. I guess you could get an approximate idea of the bearing surface, enough to workup some lots. I think a good load could go to hell quick if you got hold of a lot of bullets that were considerably different surface wise. May have to tweak something to get it to shoot again.

 

[MrMajestic]

bdale, I was the Crew Chief on an F4E, 68-429, in the late 70's. Any chance you hung anything on her? ;D

 

[ShootDots]

The bearing surface is not "Base to Ogive"... The "bearing surface" is the entirety of the bullet that actually engages the rifling. The L-O-N-G-E-R the bearing surface of a given weight bullet, the more pressure it creates. Example: if you have a 180 Berger Hybrid, it has, arguably the shortest bearing surface of any 7mm 180gr bullet I know of. On the other hand the Lapua 180 Scenar may very well have the longest. As best as I could measure them (and t-rust me, it is NOT the most accurate) there is "about" 68K MORE bearing surface than the Hybrid. If you were running 57.0gr of H4831SC out of a .284 Shehane and interchanged the bullets, undoubtedly the Scenar is going to generate considerably more pressure. So, I use "Bearing Surface" as a way to tell me HOW I should approach loading that bullet. Taking the example above, going from the Hybrid to the Shehane, you would want to drop starting loads by AT LEAST 1 FULL GRAIN and maybe more.. I do not "separate bullets according to Bearing Surface. I do, however, separate them according to "base to ogive and base to tip"..

 

[ShootDots]

It is doubtful that 1 to 3 thousandths would make very much, if any, difference at all.

 

[bdale]

Yes I understand what bearing surface is just thought it would be a better way to measure variations in bullets to sort into lots so the pressure generated would be more consistent shot to shot.

The bearing surface is not "Base to Ogive"... The "bearing surface" is the entirety of the bullet that actually engages the rifling. The L-O-N-G-E-R the bearing surface of a given weight bullet, the more pressure it creates. Example: if you have a 180 Berger Hybrid, it has, arguably the shortest bearing surface of any 7mm 180gr bullet I know of. On the other hand the Lapua 180 Scenar may very well have the longest. As best as I could measure them (and t-rust me, it is NOT the most accurate) there is "about" 68K MORE bearing surface than the Hybrid. If you were running 57.0gr of H4831SC out of a .284 Shehane and interchanged the bullets, undoubtedly the Scenar is going to generate considerably more pressure. So, I use "Bearing Surface" as a way to tell me HOW I should approach loading that bullet. Taking the example above, going from the Hybrid to the Shehane, you would want to drop starting loads by AT LEAST 1 FULL GRAIN and maybe more.. I do not "separate bullets according to Bearing Surface. I do, however, separate them according to "base to ogive and base to tip"..

 

[bdale]

bdale, I was the Crew Chief on an F4E, 68-429, in the late 70's. Any chance you hung anything on her? ;D

I was a 461 done mostly bomb building and transport to and from aircraft, did however work on the flight line with aircraft for awhile running the fuze wagon and coordinating getting the loads to F4D's mostly and getting trailers out and back to bomb dump. We did however experiment with hanging the bombs on the racks so when we got them to the flight line they could be hung on the craft faster, but they felt like it was to dangerous transporting them that way



I was there for the Easter offensive 71-72 when we painted the bombs like Easter eggs :

 

[dixieppc]

bdale, I was the Crew Chief on an F4E, 68-429, in the late 70's. Any chance you hung anything on her? ;D

I was a 461 done mostly bomb building and transport to and from aircraft, did however work on the flight line with aircraft for awhile running the fuze wagon and coordinating getting the loads to F4D's mostly and getting trailers out and back to bomb dump. We did however experiment with hanging the bombs on the racks so when we got them to the flight line they could be hung on the craft faster, but they felt like it was to dangerous transporting them that way



I was there for the Easter offensive 71-72 when we painted the bombs like Easter eggs :

Thank you for you service and all others on here that served.

Dixieppc, 38th AR&RS, Air Combat Command, 347th ARG, Vietnam 1967-1969. "That Orher's May Live." From one end of Rt 9 to the other.

 

[DennisH]

John Hoover definitely believes in measuring by bearing surface, For what it's worth, I have talked to him about it and in his 6.5x284 he states it a must!

Just my .02 worth.

 

[MrMajestic]

bdale, I was the Crew Chief on an F4E, 68-429, in the late 70's. Any chance you hung anything on her? ;D

I was a 461 done mostly bomb building and transport to and from aircraft, did however work on the flight line with aircraft for awhile running the fuze wagon and coordinating getting the loads to F4D's mostly and getting trailers out and back to bomb dump. We did however experiment with hanging the bombs on the racks so when we got them to the flight line they could be hung on the craft faster, but they felt like it was to dangerous transporting them that way



I was there for the Easter offensive 71-72 when we painted the bombs like Easter eggs :

Thank you for you service and all others on here that served.

Dixieppc, 38th AR&RS, Air Combat Command, 347th ARG, Vietnam 1967-1969. "That Orher's May Live." From one end of Rt 9 to the other.

And I thank you...

 

[johara1]

Bearing surface measurement i use is 0 for nationals, +-.0005 for records and +- .001 local matches, but haven't noticed a lot of difference but all were trimmed and pointed. ……Jim

 

[Jet]

Of the few tools/techniques available to measure bearing surface, which is used or recommended most.

Good Shooting.

Rich

 

[johara1]

Of the few tools/techniques available to measure bearing surface, which is used or recommended most.

Good Shooting.

Rich
[/quote


The one Mark King sells……… jim

 

[zipollini]

I get 2 of these in the same size - http://www.hornady.com/store/Bullet-Comparator-Inserts/

and 2 of these - http://www.hornady.com/store/Lock-N-Load-Comparator-Body-1-Each/

and use them with my digital calipers.

I own both the Sinclair and Tubb comparators and the calipers work the best by far.

 

[dkhunt14]

I have never seen any caliper attachment work as good as Mark Kings comparator. Most of the caliper ones I saw when you did it 3 times you had 3 different measurements. Matt