Measuring to Ogive

biffa

Well-Known Member
Hopefully this is a simple one - I have some load data which gives a measurement to the ogive. I am looking to load some heavier and longer match bullets to the usual soft points and am assuming my measurement to the ogive should remain constant even though the cartridge OAL then exceeds that in the manual. Can anyone provide confirmation that this is ok.
 
Nope. Different bullets will have different ogival form and a different measurement. Where are you getting that load data from? I'm curious. It's a fairly non-standard bit of data to hand out. From a private individual?~Muir
 
Last edited:
If this is printed data I am also interested.

To measure the difference on the bullets you will need a set of calipers and an overall length guage and bullet comparator with caliber specific inserts. This isn't as complicated as it sounds.
 
Nope. Different bullets will have different ogival form and a different measurement. Where are you getting that load data from? I'm curious. It's a fairly non-standard bit of data to hand out. From a private individual?~Muir

Muir Im not looking to pick an argument here, but.. Whilst I understand that different bullets have different profiles etc. Surley for an AOL they will be the same? Albeit they mey protude further into the barrell...


Nutty
 
Hopefully this is a simple one - I have some load data which gives a measurement to the ogive. I am looking to load some heavier and longer match bullets to the usual soft points and am assuming my measurement to the ogive should remain constant even though the cartridge OAL then exceeds that in the manual. Can anyone provide confirmation that this is ok.

My thoughts are yes the AOL will be the same but the bullet will protude into the barrell further.

Nutty
 
Nope the Ogive will be different on different bullet shapes, so you need a dimension to ogive for each different bullet.
It's not easy for me (of limited experience) to explain, but I shall try.........
The calibre specific insert is not calibre size, it is smaller and does not measure the true ogive, but a smaller than bore portion of the bullet.
That specific dimension it measures will then move in relation to to the true ogive dependant on the taper of the bullet.
Here are a list of the actual inserts for a few different calibres, these are Hornady (stony point) inserts measured using a vernier.
Calibre Actual
.240" .232"
.220" .213"
.30" .297"

So from that you can see the only one that would be anything like close to true reading would be the .30 cal one.
To put it in engineering terms, it is not a device for measuring anything, it is only a comparator, it accurately compares two identical items, and that is all.

Neil. :)
 
I agree. Ogives are different between makes and styles. A Hornady and a Sierra, f'rinstance. Any ogival measurement from the face of the cartridge head would result in a different OAL with each bullet. I was thinking the OP was asking if the measurement to the ogive on one would be the same as a different bullet giving the same OAL. Does that make sense?? (I'm doubting myself!)

With all this emphasis on "distance to the lands" these days, it is odd that measurement to the ogive would hold any water as the relationship between one rifle's chamber and a different rifle's chamber is bound to be different. It is though, when referenced to a specific bullet, a better measurement than "distance to the lands" or Over All Length. More akin to Seating Depth, which is my favorite reference for length -regardless of the bullet.~Muir
 
Thanks to all for your replies. I suppose I was thinking that it was only the length above of the ogive (not sure of the terminology so I'm meaning ogive to tip) that would be different for the longer bullets but, as posted, of course the bullet length below the ogive could also be longer. To my mind if I was doing what I'd originally planned which was to keep the same cartridge base to ogive measurement then I may (or probably it would seem) have both a deeper seated bullet and a longer OAL. The load data was from Mike Norris for a 139 gn Hornady soft point and I was going to load some 168gn Bergers for some paper punching. This is for a 7mm-08 which Mike has made for me so I know he has worked up the hunting load carefully and I was originally thinking I would replicate these with the longer match bullet.

I'm now thinking I should just keep the OAL at the standard 2.8" for starting with.
 
Surely if you have a comparator to measure head to ogive why don't you use or get a modified case. You can then find how far off the lands you custom ammo from Mike is and possibly replicate this with the match stuff. However I would suspect you may have to seat it further into the case if the berger is a boat tail.
 
Biffa,

instead of using a different weight bullet for paper punching, why not just carry on with your normal rounds? Unless you have a mil dot or graduated reticle on your scope and a good memory, your going to have to re zero your rifle in between targets and live quarry. As far as OAL and base to ogive length, in both my 243 and 270 I know what measurement I need to get the ogive 5 thou of the lands and load various weight bullets to the same base to ogive length. The only thing you must check is the max and min overal length given in the bullet data. As long as it is within the manufacturers limits, including the load data everything is OK.


The comparitor I have is made by sinclair. It looks like a 30mm nut with different sized and marked holes in each face. Simply slide onto a seated bullet until it seats and then measure with a caliper/ veriner etc,etc. I have at least one bullet of every weight/calibre I use seated to the required depth in empty unprimed cases.When it comes to setting my seating die, all I have to do is place the dummy round in the shell holder, screw the seating die till it touches the bullet and lock it in the press. I check the very first round I load, then check evry third round as I load a batch with calipers.


Ade

Biffa

I'll take a photo and stick it on the thread for you

As promised, some photos

Sinclair Comparitor on a 87gr Hornady hollow point and some dummy rounds I use for setting the seating die. Left to right 58gr v-max, 87gr vmax, 87gr hp, 90gr nosler balistic tip and 100gr hornady interlock

View attachment 23004 View attachment 23003
 
Last edited:
Then how were you going to measure to the ogive ?

Neil. :)

I have the Hornady inserts which go on the vernier, hadn't realised that was called a comparator. Mike advised that I am better using a measurement to ogive when reloading due to it being a more accurate measurement than to the bullet tip.I don't have the other bits so I'm just going to keep the OAL to 2.8" to begin with.

Bisley don't like expanding ammo hence the switch - I know I could get some match bullets of the same weight but just thought I'd try something else.
 
If you have the hornady inserts for your comparator you will find it far more precise to set the seating depth. I would suggest you buy a modified case. They are only about £2-3 and will allow you to know exactly your rifle chamber length. From this you can then try starting say 20thou (0.5mm) off the lands then try 5 thou either way and see which brings the group together. There is little point in spending so much time developing loads that are not specific to your rifle. IMO.
All the best.
 
If you have the hornady inserts for your comparator you will find it far more precise to set the seating depth. I would suggest you buy a modified case. They are only about £2-3 and will allow you to know exactly your rifle chamber length. From this you can then try starting say 20thou (0.5mm) off the lands then try 5 thou either way and see which brings the group together. There is little point in spending so much time developing loads that are not specific to your rifle. IMO.
All the best.

John,

If I have read the orriginal post correctly, Biffa knows the optimum jump to the lands, as the gunsmith who made his rifle developed the load for it and gave him the dimensions in the load data, so all he has to do is make sure that he maintains the same base to ogive length. If he's got hornady comparitor inserts for his vernier, then all biffa has to do is measure one of his present rounds and then repeat the dimensions with the new heads. Simples!!!!

Also, don't bother wasting money on a modified case, just get a used case, either one that will still slightly grip a head, or partially resized, push a head a couple of mil into the case, put it in the rifle and close the bolt( might be a bit stiff) this will seat the head against the lands and push any excess into the case. Eject the case, measure the oal or base to ogive, whatever floats your boat and then subtract 5thou off the lenghth. Hey presto you've got ypour optimun length.

Remember the head has to move a few thou before contacting the lands, otherwise you start to have pressure problems with hotter loads and stuck cases.

Ade
 
Last edited:
Back
Top