How do you measure bearing surface ??

[rmist]

Reading thru the 6mmBr page here. It says to sort 95gr VLD bullets by bearing surface. How do you do that ? Sorry if it's a dumb question !! I have only sorted bullets by weight before.
Thanx again,
Dave

 

[timeout]

This is the method I use. It can be an eye opener. Some bullets are very, very good. Others, even some designated as "match", leave a lot to be desired.

http://www.sinclairintl.com/reloading-equipment/measuring-tools/bullet-comparator-inserts/sinclair-bullet-sorting-stand-prod38769.aspx

 

[anri]

Litz says that the most critical measurement in bullet sorting for consistency is in fact the base to ogive measurement. According to Litz, this measurement is in fact sorting the bullets for consistent Ballistic Coefficients (BC). What occurs in the bullet forming process is what determines the bullets physical ballistic qualities. When a bullet is forced into the forming die a few factors come in to place to determine the outcome. These factors include the amount of lubrication used and how it can change the force exerted on the bullet when being formed. If the bullet is forced further than it should into the die, the outcome is a bullet with a short bearing surface, long ogive, and narrow meplat. If not forced far enough, the result is the opposite, long bearing surface, short ogive, and wide meplat. This is why variations are found in bullets, and by sorting them by the base to ogive you are sorting by the best method available. Measuring the bearing surface makes sense, but Litz has found through experimentation more inconsistent results with this method. He explained that if you look at the pressure ring of a bullet under magnification there are inconsistencies that resemble a wavy line. The heel of a bullet is not a repeatable surface like the bullet’s ogive, and these inconsistencies will cause varied measurements. Most would think that the bearing surface variants of a bullets would affect velocity spreads, but Litz claims that that factor is “down on the list”, and in tests showed little if any effect.

 

[rmist]

Thank you all...so when sorting base to ogive...are you just segregating into same lengths and shooting those in the same match ? Or are you culling them out completely and using as a fouler ? How are you determining which ones to keep as "good" bullets ?
Thanx again,
Dave

 

[mac86951]

I can't say for everyone, but usually we determine a 'spec' range and keep those for match while keeping others for foulers, etc... Measure what you have and keep within 1 standard deviation to start with.
-Mac

 

[timeout]

Thank you all...so when sorting base to ogive...are you just segregating into same lengths and shooting those in the same match ? Or are you culling them out completely and using as a fouler ? How are you determining which ones to keep as "good" bullets ?
Thanx again,
Dave

Depends on the quality of bullets you are measuring. I find that with Bergers and Bart's Ultras, the vast majority will be within a thou. Use the few that are not for something besides competition. I have checked some others that you would need to sort into as many as 6 groups. I won't knock any company by name on here. When you find a bullet that shoots like you want, buy a bunch that are all the same lot #. Although the better bullets are uniform within a certain lot #, changing lots can alter the dimension. I am by no means considering my way to be the best. You asked for opinions, mine is just another opinion. Good shooting!

 

[johara1]

What works for me, trim and point. This makes the front of the bullet uniform back to the bearing surface Then i measure the bearing surface +-.0005 on one of Tubbs BSC. All of this is done after it is spun on the Juenke machine, Then they go for a ride,hopefully close together....... jim

 

[Scott Harris]

Not sure anyone actually answered your question. The bearing surface length is the length of the bullet that is the major diameter: i.e. making contact with the barrel. This is the distance between the ogive and the end of the boat tail. You can measure this several ways, but usually with a bullet comparator at both ends of the bullet. Base-to-ogive is only measuring one end of the major diameter and using the base as a proxy for the other end. There is a high correlation between base-to-ogive length and total bearing surface length in my experience. This means either method will give you similar results.

I did an experiment at 1,000 yards and shot 10 shots in a row alternating bullets that varied .010 in total bearing surface length as measured by Tubb's tool: 5 with the short bearing length and 5 at +.010. My elevation alternated between X-ring and 9-ring. So, I am a believer that bearing length has a big impact on long range results. I think you will see a benefit sorting bullets for anything beyond 600 yards.

I also compared bullet brands by sorting 1,000 ea of Hornady, Berger, and Sierra Bullets. I did not find one manufacturer to be better than another. Rather, I found some lots to be better than others. For this reason, I have been shooting more and more Hornady bullets because they are much lower priced than the other two. I've been pleased with how they perform.

 

[johara1]

Go to the home page and and check out gear reviews and you will get review of Tubbs BSC. I don't think he is making them anymore,but I see Mark King has them...jim