ogive point

[1967spud]

if i set my seating die up for 2.230 to the ogive using 80 g noslers would the ogive be the same on all bullets of that weight i.e. 80 g noslers/ 80 g sierras

 

 

is the ogive pointon the bullet a datum point, i think is waht ia m trying to ask

 

 

as i usually use the measurement in the first part of the post for my noslers but now i am going to try and use some 87g vmax i am getting a meaurement of 2.172 using a oal guage and ogive comparater

 

 

for some reason i thoguht they should have been the same

 

 

 

heeeeeeeeeeelp pleaaaaaaaaaaaase

[eldon]

Yes it is a datum but

Depends what you mean by the same point?

 

You are using a diameter and relating it to a length. The arc of the curve could be different.

 

So if you compared 2 different heads say a round nose and a ballistic tip the OAL would be different but the ogive length would be the same if they had the same curve, a bit unlikely.

[Guest varmartin]

got this off the net...

 

 

Bullet Design–Secant vs. Tangent Ogive

Filed under: Bullets, Brass, Ammo, ▫Articles — Editor @ 8 am

 

Many shooters and hand-loaders lack a clear understanding of certain elements of bullet design. While most serious shooters know that Secant and Tangent Ogive bullets are different, many of us would have trouble explaining the precise nature of the difference. Thankfully, Dan Lilja clarifies this and many other bullet design matters in his excellent article, Calculating Bullet Weights. Here’s the straight scoop on bullet ogive differences, in Dan’s words:

 

“Spitzer bullets all fall into one of several different design types. A bullet’s geometry can be broken down into symmetrical sections. The body (or shank) of the bullet is that part of the bullet that comes into full contact with the barrel rifling. It is the cylindrical portion of the bullet of nominal groove diameter for that caliber. It is also referred to as the Bearing Surface.

 

The term “Ogive” is commonly used to describe that specific point where the curving part of the bullet nose begins–i.e. where the bearing surface ends and the curved part begins. When we talk about “bearing surface length”, this is the distance from the top of the boattail to the point where the bullet starts to curve.

 

bullet shapes secant tanget ogive

 

However, the terms “ogive” or “ogive profile” are also used to describe the entire forward curved section of the bullet, ahead of the bearing surface. The Ogive Profile, or nose of a bullet, can be one of three varieties, two being common*. The ogive can have a tangent radius; that is, the intersection of the body of the bullet and the radius of the ogive blend together at a tangent point. This is the most common type and is typical of most bullets handloaders use. The other common type is the secant ogive. In this case the intersection of the ogive and bullet body does not flow together smoothly. The point of intersection is not tangent, the ogive radius being a secant of the arc circle of the ogive.

 

Dan Lilja Bullet nose ogive tangent secant

 

The radius of the ogive is generally given as a multiple of the bullet diameter. For example, a 30-caliber bullet might have a 7-caliber tangent ogive. That is to say that the radius, in inches, is seven times .308 or 2.156 inches. When a bullet is described as “7 Ogive” this is what is meant–the radius of the bullet’s nose section as a multiple of the bullet diameter. (A “7 Ogive” can be any caliber, not just 30 caliber–it is the ratio of the curve radius to diameter that counts).

 

The point or tip of the ogive is called the Meplat. This can vary in diameter from about .050″ to over 0.125″ for conventional spitzer-type bullets.

 

The base of the bullet can be either a boattail shape or flat base. If a boattail, its shape is determined by the axial length of the boattail and the angle at which the boattail leaves the body of the bullet.”

 

*The third bullet nose type is a cone. Cone-shaped bullets are not common with handloaders, but some experimental work is done with them.

[1967spud]

Yes it is a datum but

Depends what you mean by the same point?

 

You are using a diameter and relating it to a length. The arc of the curve could be different.

 

So if you compared 2 different heads say a round nose and a ballistic tip the OAL would be different but the ogive length would be the same if they had the same curve, a bit unlikely.

 

 

ok eldon i am with you so far on this!

 

 

to seat my bullets i measure every single bullet once it is seated using an aol guage and comparater(which i was led to belive that this comparter measured to the ogive) , so there fore i took that as a length to ogive, as i dont trust col measuring with the balistic tips.

 

 

have i giot this wrong as the ogive is a measuremnent of radius?

[1967spud]

got this off the net...

 

 

Bullet Design–Secant vs. Tangent Ogive

Filed under: Bullets, Brass, Ammo, ▫Articles — Editor @ 8 am

 

Many shooters and hand-loaders lack a clear understanding of certain elements of bullet design. While most serious shooters know that Secant and Tangent Ogive bullets are different, many of us would have trouble explaining the precise nature of the difference. Thankfully, Dan Lilja clarifies this and many other bullet design matters in his excellent article, Calculating Bullet Weights. Here's the straight scoop on bullet ogive differences, in Dan's words:

 

"Spitzer bullets all fall into one of several different design types. A bullet's geometry can be broken down into symmetrical sections. The body (or shank) of the bullet is that part of the bullet that comes into full contact with the barrel rifling. It is the cylindrical portion of the bullet of nominal groove diameter for that caliber. It is also referred to as the Bearing Surface.

 

The term "Ogive" is commonly used to describe that specific point where the curving part of the bullet nose begins–i.e. where the bearing surface ends and the curved part begins. When we talk about "bearing surface length", this is the distance from the top of the boattail to the point where the bullet starts to curve.

 

bullet shapes secant tanget ogive

 

However, the terms "ogive" or "ogive profile" are also used to describe the entire forward curved section of the bullet, ahead of the bearing surface. The Ogive Profile, or nose of a bullet, can be one of three varieties, two being common*. The ogive can have a tangent radius; that is, the intersection of the body of the bullet and the radius of the ogive blend together at a tangent point. This is the most common type and is typical of most bullets handloaders use. The other common type is the secant ogive. In this case the intersection of the ogive and bullet body does not flow together smoothly. The point of intersection is not tangent, the ogive radius being a secant of the arc circle of the ogive.

 

Dan Lilja Bullet nose ogive tangent secant

 

The radius of the ogive is generally given as a multiple of the bullet diameter. For example, a 30-caliber bullet might have a 7-caliber tangent ogive. That is to say that the radius, in inches, is seven times .308 or 2.156 inches. When a bullet is described as "7 Ogive" this is what is meant–the radius of the bullet's nose section as a multiple of the bullet diameter. (A "7 Ogive" can be any caliber, not just 30 caliber–it is the ratio of the curve radius to diameter that counts).

 

The point or tip of the ogive is called the Meplat. This can vary in diameter from about .050″ to over 0.125″ for conventional spitzer-type bullets.

 

The base of the bullet can be either a boattail shape or flat base. If a boattail, its shape is determined by the axial length of the boattail and the angle at which the boattail leaves the body of the bullet."

 

*The third bullet nose type is a cone. Cone-shaped bullets are not common with handloaders, but some experimental work is done with them.

 

 

this is helpfull thanks but i will reread it, as there is a lot of info there thanks

[Redfox]

The ogive measurement is more accurate than an OAL measurement as the tips of bullets of the same make and style can vary by quite a few thou. The measurement you make holds true for that make and model of bullet, no other and can not transfer to another style never mind make of bullet. So your Noslers have absolutely no relationship to the Sierras, as each manufacturer have their own designs with variuos curves for the ogive.

Also you dont need to measure every one , if you set the seater die up to give the length you want, then make half a dozen one after the other, they should be within about 1 thou of each other depending on what you use to measure them and how used you are to measuring, which all affect the consistency of measuring. If they are all very close just get on with making ammo and check the odd one out of a batch to be sure nothing has changed.

I wouldnt get too tied up with all this as in reality it takes a difference of 5 thou or more to significantly change things and if they are all close you will get consistent results.

Redfox

[1967spud]

Does this help Spud?

 

 

YES MORE THAN YOU KNOW

 

 

 

thanks redfox that has put a lot of ghosts to bed

[eldon]

As redfox said don't check every one it just wastes time. I probably check 1 in 10 at random as nothing is moving.

 

The reason I picked a ballistic tip and a round nose was to emphasise the different curves. Using Tikkas picture you can see the length could be miles out if the taper was faster, rounder, compared to a slower more pointy one.

 

Are you fully sorted now?

[1967spud]

As redfox said don't check every one it just wastes time. I probably check 1 in 10 at random as nothing is moving.

 

The reason I picked a ballistic tip and a round nose was to emphasise the different curves. Using Tikkas picture you can see the length could be miles out if the taper was faster, rounder, compared to a slower more pointy one.

 

Are you fully sorted now?

]

 

 

think so thanks mate

 

 

just a side question on this thread

 

is there anybody in norfolk in to reloading/rifle shooting who fancies a meet up some where. or if they have access to land with a bit of range 500 yards + for a exbal afternoon as om my land i can get to about 450 yards but then i am suffering from line of sight issues. i would like to have a play with my loads at range but lack the room for desecent distance.

[eldon]

500 yds in norfolk

 

What you using for a backstop, last time I went there you had no hills or anything of interest

[1967spud]

500 yds in norfolk

 

What you using for a backstop, last time I went there you had no hills or anything of interest

6

 

i am using my old girls fat arse lol

[eldon]

In that case you might get some helpers :lol:

[Ronin]

The ogive is the diameter where the bullet becomes calibre size from the tip moving rearwards.

 

Evey bullet could be seated to the same depth using one measurement (for example 2,850") in the case of 308 and 155g Scenars.

 

 

However, if you go down (or up) in bullet weight, you will end up with more (or less) of the bullet shank in the case neck to attain the same OAL to Ogive.

 

Every bullet needs to be seated to the optimum depth for accuracy rather than use one set depth for all.

 

Just my 2p

[Guest northernchris]

Mark

 

If your coming over this way,you can get out over here with Exbal to do some testing,as i dont think i can now get over to Thetford stalking else i could have come over.

 

Chris

[Redfox]

Ronin

In actual fact with very few exceptions the optimum bullet clearance or jump in a rifle is the same for all bullets used in that rifle e.g. if your rifle works best with .025" clearance that remains true for all but the odd specialised bullet, with that rifle. Other factors like powder, load density, velocity/powder charge all have an effect of course.

I was told this years ago by someone who has loaded a lot of ammo and I must admit didnt fully beleive it, however I have tried the principal in most of my rifles and those of plenty of others and it does work.

Target shooting has some differences as they tend to load down for accuracy and tend to poke the bullet into the throat, in that case it could be said to be still true as zero clearance remains just that.

Redfox

[Ronin]

Hear what you say RF, but,,

 

 

I had in mind a couple of issues with my own rifles:

 

#1 - 6.5x284 stalking rifle - I use 140g SST for deer in that lseated .010" off the lands. I also use the rifle for target work and for that use 142SMK at .005" off and 140 Bergers at +.020" into the lands.

 

#2 - 25-06 stalking rifle - main load is 100g Speer seated .015" off the lands, however for larger beast I use 117g Interlocks, thye shoot exceptionaly well seated .005" off the lands.

 

I have played with the seat depth extensively on both these rifles and these bullets shoot best seated to the dimensions shown.

 

I accept there isnt much difference bettween -.015" and +.020" in terms of seating depth, but the differences are noticable in my own findings.

 

 

Every gun is different, so a generalisation may not apply to all anyway.

[Redfox]

What your saying there pretty well agrees with what Ive said, there are specialist bullets that require minor changes and Target shooting stands very much on its own when it comes to what works in what rifle. Your right .005 isnt much and I said somewhere that less than 005" wouldnt normally make a difference, plus into the rifling is not under discussion in this instance, although it is pretty hard to tell if your going actually into the rifling by whatever amount as it usually pushes an uncrimped bullet back into the case, albeit by a small but uncontrolled amount.

SAAMI length ammo shoots very well these days in all mass produced rifles, the variation being the maker/bullet style which suits your particular rifle but it does very well for 99.9% of all rifles.

The theory was developed across the pond as the result of loading literally millions of rounds of ammo by various makers and their experts/testers and is a very reasonable theory given that you are going each time for that particular point on the ogive whichever the bullet.

There are very few absolutes in anything hence my saying there are exceptions as in all things. Measurement has been a part of my life for many years now from centimetres to parts of a micron and most of the methods used by shooters to measure clearance in their rifles is no where near the accuracy required to definitely state this clearance or that is used ( there is after all a +/- tolerance on all normal measurement anyway) what most acheive is a consistant length ammo and when it works they stick to that which is all that is required.

I have found as I said that it holds up in practice by trying it out on various calibres and rifles and the results have been in line with the theory. I have taken a new bullet of similar type ( hunting or target) and used the same ogive to throat clearnce as has given best results in that rifle and it has immediately given the same level of accuracy ( given that some bullets just dont work in that rifle), subsequent experimenting has not given any real improvement over the original clearance.

The other generality I have mentioned before being that smaller than 25 cal tends to shoot better with more clearance and above tends to shoot better with less clearance, but it again depends on what your doing with it target or hunting.

My 243 even after re-barreling still likes .040" off the rifling whichever bullet I use with it and always has done since new in 1968!

and I have experimented greatly with it ( like you do) .

There have to be some basics in all things but they are that and there is no doubt with particularly hand made rifles and good target bullets that you can fine tune to get the very best out of them, therein lies the interest and challenge for many people.

Redfox

[Andrew]

Well put Red! ~Andrew