Of cannelures, ogives, lands, and OALs

[<SLV>]

I'm getting ready to load my first .30-06 cases for my Tikka T3. I ran an empty case with bullet (150 gr. Hornady FMJ/BT) through the action to determine a length of 3.325" at which the ogive contacts the lands. I have decided to load for an OAL of 3.3", but when I set the bullet at this length the cannelure is significantly above the case neck.

1. What good is a cannelure if I'm not crimping?
2. Is there any problem with leaving the cannelure exposed?
3. How do I know if enough of the bullet is in the case?

 

[rg1]

Hornady Manual 5th Edition lists an overall length with the 150gr bt-fmj at
3.260". Hornady 7th Edition Manual lists an overall length for the same bullet at 3.185" and has this bullet in its 30-06 pages and in its M1 Garand data pages. For the cannelure to be correct for the 30-06 case the 3.185" length is correct. At 3.260" the cannelure is forward of the mouth and your 3.300" will be even further out. I've shot both lengths in M1 Garand rifles and both feed and function ok with little or no change in accuracy. However the general rule for the amount of bullet needed to be inside the case for adequate bullet-case tension is one caliber for the caliber you're shooting. So if that rule is correct you need approx. .308" of the bullet inside the mouth. That would'nt apply to the boat tail, just the major diameter of the bullet. The same would apply to bullets that have no cannelure. I'd test these bullets in your 30-06 bolt rifle at varying lengths from the 3.185" up to your chosen length just to test for what's most accurate. A couple of my hunting rifles prefer bullets seated 30-35 thou off the lands for best accuracy with my components. Seated closer or further off the lands and spread opens a little. No problem leaving the cannelure outside the mouth if you have adequate bullet tension in the case. This Hornady bullet and the cannelure location and their change of o.a.l. is unusual yet they show this bullet with nearly all 30 caliber rifles so I guess the cannelure can't be correct for all.

 

[USSR]

1. What good is a cannelure if I'm not crimping?

It really does no good if you aren't using it. But, that being said, I never crimp rifle bullets and I shoot cannelured bullets without crimping.

2. Is there any problem with leaving the cannelure exposed?

Nope.

3. How do I know if enough of the bullet is in the case?

The rule of thumb, is to leave atleast 1 caliber (.308) of the bullet in the case.

Don

 

[<SLV>]

I've heard that bolt guns will achieve the best accuracy with the bullet 0.025-0.050 off the lands. Does anyone else have a recommendation for tuning the ammunition's AOL to my specific gun?

 

[esheato]

Sure....

Experiment with your rifle. It'll become apparent which direction it likes bullets.

Ed

 

[USSR]

<SLV>,

If you don't already have it, buy the Stoney Point/Hornady OAL Gauge and a modified case, and determine just exactly where your throat is. Having your bullet .010" to .015" off the lands is a good place to be.

Don

 

[azar]

OAL Guage & Bullet comparator

USSR,

Is there a reliable way to measure without using those tools. Maybe something similar to what is talked about in this thread? The main reason I ask is that I've about hit my limit "saving money" reloading. There never seems to be an end of all the neat gizmos you can burn your paycheck on to make your rounds that much more accurate.

Note: I believe the "Stoney Point" brand no longer exists. In the Midsouth Shooters Supply master catalog they show "Hornady Lock-N-Load Bullet Comparator and O.A.L. Gauges (Formerly Stoney Point)". So it looks like Stoney Point my now be owned by Hornady. Or perhaps the bought the rights to those tools, who knows.

 

[birdbustr]

I have a bullet comparator set that I got for about $30. I do know of a cheap way to test how deep the lands/grooves are.

1. Take a empty casing from whatever caliber gun you want to know about, cut 2 or 3 slots in the neck of the case. This will allow the bullet to still hold in the case.
2. Take one of the bullets and a lighter and blacken the bullet (use a larger grain bullet) from the smoke.
3. Insert the blackened bullet into the slotted case, chamber slowly and then carefully eject the round out so you don't disturb the position of the bullet.
4. Measure where the lands and grooves show on the blackened bullet from the bottom of the case to the marks. There you have the depth of your lands and grooves.

 

[USSR]

azar,

Yes, Hornady bought Stoney Point, that why I called it "Stoney Point/Hornady OAL Gauge". Are there other ways? Sure. How precise, reliable and repeatable are they? Not very. Yes, the gizmo's do cost you $$$.

Don

 

[Bitswap]

IMO, you should know your maximum coal and cartridge length should be. The stoney point, or hornady, is pretty good at determing this and very repeatable if you have a light touch.

Consider that these are maximums. The former being dangerous if you don't trim correctly. There are some home-made solutions to obtain these measurements that work well.

Also consider that a bullet 'on the lands' may not be optimum. IMO, finding the harmonic or OCW is the best way to go. For my 308, 0.030 behind the lands is the sweet spot for the powder measure I use. Seating on the lands can really mess things up as well. Ever go over a speed bump when your were on it vs a running start? Same thing happens with a bullet.

Sierra has been very good about their coal and seem to be perfect. That's where I'd start and increase/decrease by either 0.010 or 0.003 depending on how many times you want to go to the range.

Hope this helps,
Bit

 

[azar]

USSR,

Ooops! I hadn't notice the mention of Hornady in your post.

My fear is buying these tools and then not being able to use them correctly or using them correctly but not really being able to tell a difference in accuracy. I guess mainly what I'm getting at is the fear of buyers remorse at having purchased something that I didn't really need.

Plus, I have a kid on the way and my disposable income is no longer disposable.

Oh, and the soot / dry-erase marker on the bullet trick has never worked for me. I'm not sure I have ever seen evidence of the lands... But I have never tried cutting 2 or 3 slots into the case neck. I've just been going off "Does the bolt close easily? This is the starting point." Which may not be the best method. I had to do that on some Sierra 160g round nose loaded in 6.5x55SE. Sierra had the C.O.A.L at 3.050" which wouldn't chamber easily in my gun with that particular round. I decided to simply drop it down to 3.025" (a common length for reloads for this caliber) which chambered nicely and has patterned quite well. But I'm to much of a perfectionist to not know if it could get even better...

 

[ny32182]

Well I've got a strange set of circumstances here... I'm loading the same Hornady 150gr FMJ in .308. I've got the cases trimmed to just over the listed "trim length". I'm seating the bullet and at the recommended 2.78" OAL, the cannelure is fully exposed? Indeed it is.

I thought this bullet would have been made specifically for .308 for the mostpart?

I intend to shoot this ammo in an FAL, should I just Lee factory crimp die it afterward and call it good?

 

[USSR]

ny32182,

Ignore the cannelure. BTW, I load for my FAL with a 2.81" OAL (the longest that will fit the magazine), and most of the bullets I load don't even have cannelures. As long as you have sufficient neck tension, you don't need to crimp. Holding a loaded cartridge upside down with a finger on each side of the case, pressing the bullet tip into a table top, if the bullet doesn't move, you've got enough neck tension.

Don

 

[ny32182]

Thanks..

 

[ny32182]

So I've got another question..

When I was first tearing down and reseating Paki surplus, I was getting varying OAL's, which I thought was fine since the bullets were inconsistent, both visually, and when weighed.

However, I'm having the same thing happen with the new Hornady FMJ bullets. Varying OALs. Nothing that will cause a KB, and I'm running them a little longer than the load data suggestion, but I'd say the extreme spread I'm seeing is nearly .01". These bullets are weighing to within 2/10ths of a grain of each other, and the shape of the forward portion of the bullet "looks" the same to me on each one.

I only mention it because my .223 loads using similar Hornady FMJ's are coming out very consistent (comparatively at least). I seem to recall an extreme spread of .002" or .003".

Could something be wrong with my seating die? There is something I'm not getting here.

 

[USSR]

Could something be wrong with my seating die?

No. Your seating die seats the bullets near the bullet ogive and not the bullet tip. This is as it should be, as the place where your bullets contact the lands is at the ogive, not the tip. Don't worry about the varying OAL, as long as they are not running too long to fit your magazine.

Don

 

[ny32182]

So you'd guess the root cause is just inconsistency in the shape of the ogive that I can't see with the "naked eye"?

 

[ny32182]

double tap

 

[taliv]

no, the ogive is probably pretty consistent. the length of the tip (meplat) is what is most likely varying. general consensus is that deviations in OAL measured from the tip have no measurable impact on accuracy HOWEVER, sinclair and others sell "meplat trimmers" so you can fix it if you wish.

 

[ny32182]

Can I get an exact definition of ogive, meplat, and/or any other dimensions that might be useful to know about? A diagram, maybe?

Thanks for all the info so far...

 

[USSR]

taliv is correct, it's the bullet tip locations that vary. Ogive is the portion of the bullet where it starts to curve away from the .308" part of the bullet and narrow as it progresses towards the tip. The only part of the ogive that concerns us, is the part where it narrows from .308" to .300", since this is the part that contacts the lands. Having your ammo with all the bullet ogives located the same distance from the lands is more important than having all your ammo with the same OAL.

Don

 

[ny32182]

If I'm getting different seating depths though, and the ogive is what is contacted by the seating die, wouldn't that mean that either the ogives have to be inconsistent, or something is going on with my die?

 

[taliv]

no, it means you're measuring from the tip of the bullet.

what you need is a little doohickey that you put on your calipers to measure OAL from the ogive. i'll try tofind a link for you in a moment



edit: try this http://www.sinclairintl.com/cgi-bin/category.cgi?category=RESDTCO&item=09-700&type=store

notice in the picture how the tip of the bullet is poking through the little metal gadget. the bullet is contacting the metal gadget the same as it would a barrel (it has 6 holes for 6 calibers)

 

[ny32182]

Ahh... gotcha. So it is an inconsistency forward of the ogive. I see.

 

[<SLV>]

Cool tool, that comparator, but how do you get an exact measurement of your chamber from boltface to lands? You would have to know this in order to know your ideal measurement on the comparator. I had a friend tell me to seat a bullet by closing the chamber, but that seems somewhat crude.