Distance to ogive/lands.
*Please bare with me on this long winded post*
So I finally got a OAL Gauge and the bullet comparator and insert for my .243WIN.
I was curious about bullet seating depth from the lands and how it affects accuracy since I was getting about nickle sized groups at 100 yards. I wanted to see if I can shrink it ya know...who doesn't. :P
So anyways, I have two different bullets. The 65 grain Hornady V-Max, and Speer BTHP....I think they are game king(?) About 85 grain if I recall....I don't have the box its out in the storage shed at the moment.
Now I set up my caliper with the comparator and insert and found it about +.035 from being exactly 1". So I reset calibrated it to read 1.000 (I will be using that extra inch in my measurements here).
So I put the empty cartridge in and it chambers fine. I added teh Hornady 65 Vmax and slowly inserted the plunger thing until I felt the bullet hit the lands very gently.
Measurement on the caliper to the Ogive = 3.249" (so actually 2.249)
I disassembled everything and repeated. New measure was the EXACT same. :P
Now the problem.
The after disassembling and repeating with the Speer, the measurement = 3.268" (2.268)
I disassembled and repeated. New number = 3.268 The same as before.
So I guess the thing is that if this is to measure the Overal length to the lands, how can I get two seperate numbers and they both get repeated? It doesn't seem logical to me at this moment in time. I can see the OAL be different for all bullets, but the length to the Ogive should be the same since its to the lands right????????
So I finally got a OAL Gauge and the bullet comparator and insert for my .243WIN.
I was curious about bullet seating depth from the lands and how it affects accuracy since I was getting about nickle sized groups at 100 yards. I wanted to see if I can shrink it ya know...who doesn't. :P
So anyways, I have two different bullets. The 65 grain Hornady V-Max, and Speer BTHP....I think they are game king(?) About 85 grain if I recall....I don't have the box its out in the storage shed at the moment.
Now I set up my caliper with the comparator and insert and found it about +.035 from being exactly 1". So I reset calibrated it to read 1.000 (I will be using that extra inch in my measurements here).
So I put the empty cartridge in and it chambers fine. I added teh Hornady 65 Vmax and slowly inserted the plunger thing until I felt the bullet hit the lands very gently.
Measurement on the caliper to the Ogive = 3.249" (so actually 2.249)
I disassembled everything and repeated. New measure was the EXACT same. :P
Now the problem.
The after disassembling and repeating with the Speer, the measurement = 3.268" (2.268)
I disassembled and repeated. New number = 3.268 The same as before.
So I guess the thing is that if this is to measure the Overal length to the lands, how can I get two seperate numbers and they both get repeated? It doesn't seem logical to me at this moment in time. I can see the OAL be different for all bullets, but the length to the Ogive should be the same since its to the lands right????????
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So I am researching more on the net....every bullet has a different ogive length even in the same rifle? I thought the ogive is one and the same as the distance to the lands? 0 -
The Ogive measurement will change from bullet type/brand due to the different shapes/lengths of bullets.
Example: A Barnes solid copper bullet( x-bullet, XLC, TSX, etc) will be longer than a bullet that is the same weight & diameter of normal/traditional construction because you can't change the diameter of the caliber, so it has to be longer to weigh the same as a lead jacketed bullet(cup & core) because of the differences in the weight of copper vs lead, etc..
Different types of bullets will measure differently, such as a roundnose vs a Boat Tail Spitzer.
You should be able to expect a box of the same caliber/brand/type and weight to measure very closely from ogive to lands if you do your part and they are of quality construction. Even the best of bullets are not perfectly the same.
In short : If you change bullets you'll have to measure again because the Ogive will probably measure differently.
It's usually best to try and buy bullets of the same lot number in bulk if possible because your odds of them being the same are increased.
Good Luck...........[^]0 -
quote:Originally posted by temblor
The Ogive measurement will change from bullet type/brand due to the different shapes/lengths of bullets.
Example: A Barnes solid copper bullet( x-bullet, XLC, TSX, etc) will be longer than a bullet that is the same weight & diameter of normal/traditional construction because you can't change the diameter of the caliber, so it has to be longer to weigh the same as a lead jacketed bullet(cup & core) because of the differences in the weight of copper vs lead, etc..
Different types of bullets will measure differently, such as a roundnose vs a Boat Tail Spitzer.
You should be able to expect a box of the same caliber/brand/type and weight to measure very closely from ogive to lands if you do your part and they are of quality construction. Even the best of bullets are not perfectly the same.
In short : If you change bullets you'll have to measure again because the Ogive will probably measure differently.
It's usually best to try and buy bullets of the same lot number in bulk if possible because your odds of them being the same are increased.
Good Luck...........[^]
Okay thanks a lot. I still don't get it all the way....I will post a pic of what I am getting at....
See, the area the bullet at the ogive should be the same diamater across on any bullet since a .243 is gonna have a barrel about .24 right? So if you shove a case and a bullet into the chamber and have the ogive of both TOUCH the lands, should the ogive be the exact same?
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It perhaps would be more precise to say "The POINT on the ogive where the bullet contacts the lands"..and using that equipment should give repeatable results, bullet to bullet.
Given a bullet that is shaped like a darning needle, 4 inches long..at some point iT must contact the barrel..and this is where the comparator measures from.
Any chance your calipers jumped .020 ? Perhaps the throut is eroded ?0 -
The distance to the ogive should not change...no matter what kind of bullet you use. The overall cartridge length will change (even with the same bullets), but the length to the ogive will remain the same. I would think that you are having a problem with your calipers...or on setting them up. 0 -
Let me see if I can muddy the waters a bit more. I have a Stoney Point OAL gauge as well. I also get different readings with different bullets. My caliper is digital and very accurate. So, why the different lengths? How about this? We are assuming that the "comparator" is the exact same size as the barrel. In reality the point at which the bullet contacts the rifling is Not the exact same point that the comparator contacts the bullet. Now I have myself even more confused. 0 -
The measurement from casehead to ogive will remain constant for every bullet, no matter the weight or shape. The point at which the bullet reaches full caliber dia needs to be set at the same reading for the same distance. This is not to be confused with OAL which is casehead to tip of projectile.
If you use your seating depth tool (I much prefer the sinclair tool) and you get your OAL, you then seat the dummy round to be EXACTLY that OAL as your measurement indicated it should be. Then use the comparator to determine the casehead to ogive measurement. NOW, when you swith bullets, you simply seat the new pills until the comparator shows the same casehad to ogive measurement, and regardless of OAL, your ogive is now exactly the same distance from the lands as the first bullet was. Write down the casehead to ogive measurement inside the die box, so you can quickly refer to that when switching pills.0 -
quote:Originally posted by steve4102
Let me see if I can muddy the waters a bit more. I have a Stoney Point OAL gauge as well. I also get different readings with different bullets. My caliper is digital and very accurate. So, why the different lengths? How about this? We are assuming that the "comparator" is the exact same size as the barrel. In reality the point at which the bullet contacts the rifling is Not the exact same point that the comparator contacts the bullet. Now I have myself even more confused.
OHHHHHHH! lol. I didn't even think that the caparator would be measuring a different spot on the bullet its slightly different from the barrel diameter. That makes sense now.
Thanks everyone.
It was really bugging me last night because when I tested this stuff I completely disassembled the the StoneyPoint stuff from the caliper and made sure it was always zereo before each of the four measurements. There was no way I screwed up. I did the V-Max, then the Sierra (not Speer, sorry, it was late), then back to the V-Max, and then teh Sierra again.0 -
Sorry Outlaws, I misunderstood your question. I thought you didn't understand the way the measurement for Ogive to lands changed when you varied the overall length of of your cartridges with different bullets( across the tips ).
It was late.....[:D]0 -
As stated..the comparator hole dia. means little. The word "comparator" is sorta self-explanatory...they make no attempt to try and match the jillions of rifle barrels out there...and had no need to.
The OAL gauge sets the bullet to YOUR throat/land configuration..then when the comparator is used, it does NOT give the same exact precise point on the ogive that actually touches first...just a "comparing point".
Having the throat/land area REALLY CLEAN helps in repeatable measuring...and using the same 'touch' on the OAL gauge also.
I am not totally, completely happy with the Stony Point tool..and one day perhaps I will devise something that gives me precise readings. Till then...it works well enough.0 -
highball, try the sinclair oal tool,..it utilizes a fired case from your chamber,...works for me every time[;)] I did not like the stoney point idea of an unfitted "fake" case.
Also, the sinclair comparator is cut with a throating reamer, and is accurate by my measurements as far as groove dia. The stoney points,....I use 2 sets for sorting by bearing surface length when sorting bullets, but not for ogive to land work,..that is reserved for the sinclair.
I could usually get within .002-.003" with the split neck method though[^]0 -
Another tool to buy...[:D]
Ah, well, I guess that makes the world go round.0 -
Outlaws
I agree with Justc that you can't really expect an accurate measurement with the standard Stoneypoint with Case gages. You get close but then have to check each load/bullet and adjust accordingly. It takes several seatings each time you change bullets in a given caliber.
So, not knowing there were other brands names out there I measured the hole/threads and came up with a 5/16's hole using 36TPI I drill a 9/32" hole in a fired case and tap with a 36 TPI tap(not very easy to find). I found that it was actually easier to just do the several checks because it's easy to ruin a case you are converting. The ones that came out do pretty good though.
In short I will add my answer to your question(as everyone else has. It's because there are different ogives on each bullet. And, even though each ogive should hit the lands in a given rilfe at one point the bullet does not come in contact with the seating die in the same place. So each different type/weight of bullet must be measured. WRITING THIS DOWN SAVES CONFUSION AND RE-MEASURING IN THE FUTRE. I only say that as I have done that before and had to re-measure a few times. Not that I mind, because doing something with guns is something that I enjoy. -good luck0 -
quote:different ogives on each bullet. And, even though each ogive should hit the lands in a given rilfe at one point the bullet does not come in contact with the seating die in the same place. So each different type/weight of bullet must be measured
I will agree with the above..at least each different bullet MUST be measured with the Comparator set-up.
Bullet points can vary .020, right out of the same box.0 -
the nose of bullets other than the polycarbonate tips will be varying in lenght. You have to use the ogive measurement to get an accurate measurement. Nose shape and profile mean nothing,..only the relation of the ogive at full caliber to the lands.
The sinlcair tool uses a FIRED case from YOUR chamber to get an accurate value for casehead/boltface matchup to the ogive/lands matchup. The fired case from that chamber is the only correct way to do it in my experience. That fired case will headspace off of the shoulder and will only be maybe a max of .002" short at the casehead due to springback. Therefore, the bullet dropped in your tube+the fired case measurement will put you to a guaranteed measurement with a .002" error for new brass springback. This is the best $50 you will ever spend. I get measurements that MAY vary by .001" when running this measurement with the same bullet and same case several times over.[^]0 -
JustC;
So late we get so smart. You just explained the problem in a way so it even penetrated MY foggy excuse for a brain.
HEADSPACE..and the absolute reason to use a fired case from the rifle.0
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