Sorting bullets by surface length?

L

LorenC

Guest
Could someone expound a bit on this please? I can understand the why but don't think I can think of an effective how? Loren.
 
Check out Bill Shehane at D & B Supply. I have his setup. A bit pricy, but dead on balls accurate and more importantly.....repeatable. Baisicly it uses...well, I can't explain it. But, I can email a picture of the setup. Very simple concept. I segragate my bullets to .001 bearing serface.

Thanks,
Tod
 
I think you actually mean bearing length, which is the length of the bullet in contact with the lands. I measure and sort them with a Davidson base and nose piece attached to my caliper. The Hornady comparator does same thing. You can find both in the Sinclair catalog. Sort them by .001" groups; shoot those that are most consistent in bearing length.
 
I've always Figured if the bearing lenghts were not the same your seating lenght would be different, and if one were longer than the other. What happens in the barrel as far as twist, seeing this is the only part that touches the rifling. I know for a fact that from lot to lot bearing lenght changes 30 thou. they're going to shoot different. I haven't tryed changing seating depth to allow for lenght difference,but its next on my list for thing to try. Different twist different lenght! think about it.

Joe Salt
 
Since no one else mentioned Bob Green bullet comparator (B.G.C.)I thought I would . I have used this tool for several years now and believe it allows the user to sort bullets in a way that other comparators can't. Bullets can vary from the point that the bullet seater stem contacts the tip of the bullet and the place on the bullet that contacts the rifling in a barrel. It allows the user to sort bullets with this comparator into lots that will seat to a more uniform depth (to where the place on the bullet that contacts the rifling will all engage the rifling the same). I'm not sure I explained myself very well but here is a link to Bob's web site that might explain it a little better than I ca.
Bob Greens BGC link: http://greensrifles.com/New_Products.html

Rodney
 
tenring said:
I think you actually mean bearing length, which is the length of the bullet in contact with the lands. I measure and sort them with a Davidson base and nose piece attached to my caliper. The Hornady comparator does same thing. You can find both in the Sinclair catalog. Sort them by .001" groups; shoot those that are most consistent in bearing length.
Click to expand...

I think this is along the same lines as what I was asking about. The bearing surface area in regards to seating pressure and friction passing through the barrel, and the changing in pressures as that area changes. A longer bearing area will produce a higher seating pressure, and resulting release, thus varying the ES most likely? Same and maybe a higher probability of that greater surface area changing the ES as it produces higher resistance traveling down the barrel.
 
Charles E said:
Joe, I have thought about it. R.G. Robinett made up a few test bullets on the 187 BIB, with a very short boattail. Think about it: same lot of jackets, same dies (except a BT punch added), same everything. Of course the bearing length was different.

At 100 yards, they shot into the same hole. Now of course, at 1K, they're different, as the BC of the boattail version is higher.
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Thinking along the lines of my previous post the boattail version had more than just aero as a difference. Wondering how much change in bearing surface, or, actually, friction difference as it made it's way through the barrel?
 
The Bob Green tool description states: "the point on the bullet where the bullet seater makes contact", i.e., the meplat or bullet tip to base. There is no bearing surface between the ogive and meplat. The comparators used with a caliper measure only to the ogive.

I have not noticed any difference in seating pressure with a few thou difference in bearing length. Presumably, there would be some increased friction with longer bearing surface, and maybe differences in ES, but I do not know how you would quantify it.
 
Charles E said:
Or save yourself $250, and make an adaptor that lets you use your meplat trimmer body with a dial gauge...
Click to expand...

The dial gauge Bob uses IS a big chunk of the $250 Bob charges for the comparator. I know I didn't have an extra .0001" dial indicator laying around .

Rodney
 
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Bearing serface has no relationship to jump or jam. Once you have your bullet seater set up for x.xxx lenght, any variance in bullet length or bearing serface will show up INSIDE the case.....if a bullet is .003 longer, or has .003 more bearing serface it is just pushed into the case .003 more.

I am concerned with actual bearing serface....the part of the bullet that actually rides the rifleing......more bearing serface means more friction, which means more psi, which means.....well, you get the point.

Just remember...it does not matter how long your bullet is, after you seat the bullet, the seating die is only going to let the oal be one set number....any variation in actuall bullet length will show up INSIDE the case.
 
Same here. This is the point of my original post.

Tod Soeby said:
Bearing serface has no relationship to jump or jam. Once you have your bullet seater set up for x.xxx lenght, any variance in bullet length or bearing serface will show up INSIDE the case.....if a bullet is .003 longer, or has .003 more bearing serface it is just pushed into the case .003 more.

I am concerned with actual bearing serface....the part of the bullet that actually rides the rifleing......more bearing serface means more friction, which means more psi, which means.....well, you get the point.

Just remember...it does not matter how long your bullet is, after you seat the bullet, the seating die is only going to let the oal be one set number....any variation in actuall bullet length will show up INSIDE the case.
Click to expand...
 
Is there any evidence saying the burn pressure expands the neck and releases its grip before the base of the bullet passes the mouth?
 
Sorry, I was replying to Charles E asking about jump/jam vs bearing serface. Like I also said, I use Bill Shehanes system. I can get through 1000 bullets fairly quickly. Most improtant to me....there is no wondering if I did it right...very confident in my results!!
 
tod....it is useless to try and teach anything to charles e...he knows it all and will tell you so...even if in his post it is quite obvious he does not....and you pointed it out....i was going to, but it is much better when it comes from SOMEONE THAT HAS WON SOMETHING IN THE LAST TEN YEARS.
all ya'all have a nice christmas!
mike in co
Tod Soeby said:
Sorry, I was replying to Charles E asking about jump/jam vs bearing serface. Like I also said, I use Bill Shehanes system. I can get through 1000 bullets fairly quickly. Most improtant to me....there is no wondering if I did it right...very confident in my results!!
Click to expand...
 
Joe Salt said:
I've always Figured if the bearing lenghts were not the same your seating lenght would be different, and if one were longer than the other. What happens in the barrel as far as twist, seeing this is the only part that touches the rifling. I know for a fact that from lot to lot bearing lenght changes 30 thou. they're going to shoot different. I haven't tryed changing seating depth to allow for lenght difference,but its next on my list for thing to try. Different twist different lenght! think about it.

Joe Salt
Click to expand...
Hey Joe are you going to let Kathy shoot so we know the real results?
You and Kathy have a merry Christmas. Matt
 
I believe they seat to the same OAL like Tod says. But i believe the velocity will be different and the shape of the bullet will be different resulting in a different impact at 1000 yards. Matt
 
I don't think you need lots of wire....just sort a box of 1000 bullets...shoot the 10 (or 20, 030, or.....) with the shortest bearing serface and 10 with the longest out to 1k....you will have your answer. You will know if there is a difference in muzzle velocity, and you will know if there is a difference in impact heights at 1K.

Oh, and PS....I do not want to be drug into a pissing match between personalities....not to be confused with getting into MY OWN pissing matches. :eek:
 
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Charles,

You just disproved your own point..."2. Usually, I've found that the (the) greatest variance in the length of the bullet occurs between the ojive and the tip (of the nose). ........Depending on how your seating die sets up, that affects jam/jump."

The jump/ jam is measured FROM the OJIVE, not anywhere else "from that point to the tip" ....the fact that from the ojive to the tip is .00003 or 3.0000 longer has no affect on seating depth if you are measuring from the ojive.

As far as longer bearing serface vs FPS/ PSI increase/decrease...I have no idea.....and the test in my above post might shed some light. But, I guess that I am not willing to take the chance....I will sort my match bullets....you know, the confidence thing.!! ;)
 
Someone explain to me how different bearing surface lengths changes seating depth. Did you figure out a way to seat from the base of the bullet?
 
LorenC,

You are 100 % correct.......bearing serface has 0% effect on catridge OAL when measured from the ojive, provided that your bullet seater uses the ojive of the bullet as its "reference point", for lack of a better term. If a bullet has a longer bearing serface, you will just end up with a little more bullet inside the case.

This may or may not affect velocity and or PSI. I'm just not taking any chances.

Kind of like I read in PS many years ago....." I preform 7 different steps to accurize my brass, only three of which actually have any effect on accuracy. The problem.....I don't know which three steps it is!!!" I may be taking some liberties with the actual verbage, but you get the point.

I feel like I am spinning my wheels a little bit here.:eek:
 
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