Can't get the same damn oal depth! (ogive)

[taseal]

I just used an expander plug to get the neck to open up a bit on my lapua brass, and then put some light lube on the inside of neck.

I got 3 readings... (this is 175SMK on Lapua .30-06 virgin brass)

1st was 2.800
2nd was 2.815
3rd was 2.830

I rechecked the oal with the calipers and I got same readings, so I know it's not the calipers or me. I also used the hornady ogive comparator.

what the hell can cause this to be off? I'm just trying to get a seating depth so I can set my mic seater to get the same depth!

Thanks, this is frustrating

 

[Leaddog]

Re: Can't get the same damn oal depth! (ogive)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: taseal</div><div class="ubbcode-body">I just used an expander plug to get the neck to open up a bit on my lapua brass, and then put some light lube on the inside of neck.

I got 3 readings... (this is 175SMK on Lapua .30-06 virgin brass)

1st was 2.800
2nd was 2.815
3rd was 2.830

I rechecked the oal with the calipers and I got same readings, so I know it's not the calipers or me. I also used the hornady ogive comparator.

what the hell can cause this to be off? I'm just trying to get a seating depth so I can set my mic seater to get the same depth!

Thanks, this is frustrating

</div></div>

Sierra's are not all that consistent. I gave up on them and went to Bergers a long time ago. Even with Bergers, there is some deviation. You'll have to use an average and go with it. This is not an exact science, sorry to say.

 

[shoot4fun]

Re: Can't get the same damn oal depth! (ogive)

I understand the COAL being off. The best way to measure is to the ogive with the comparator you have. What were the measurements there? Closer, I would think.
I have a buddy that seats all his bullets twice, so to speak. He seats the bullet, backs it out of the die, rotates the entire cartridge about 90 degrees and runs thru the seater again. He swears it gives him more consistency but I just think he is OCD.

 

[BBeyer]

Re: Can't get the same damn oal depth! (ogive)

Try seating with no lube on inside of neck. Sierras may not be consistant but they are a lot more consistant then the numbers you are getting.

 

[taseal]

Re: Can't get the same damn oal depth! (ogive)

just for clarification, this is in my chamber. not the seater die.

I can't get a good OAL from the chamber. and that being said, I don't even know my or care for my COAL. I use ogive only.

 

[Charlie Papa]

Re: Can't get the same damn oal depth! (ogive)

I use this tool from Sinclair. The picture here doesn't show the whole tool, and you have to read the directions a couple of times before it makes sense, but once you get it, you should get consistent results.

Sorry, I know this won't help you in the immediate future, but I hope it does help.

CP

 

[SPAK]

Re: Can't get the same damn oal depth! (ogive)

Are you just trying to find the distance to the lands in your rifle??

 

[taseal]

Re: Can't get the same damn oal depth! (ogive)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Frogman77</div><div class="ubbcode-body">Are you just trying to find the distance to the lands in your rifle?? </div></div>

yes sir.

 

[taseal]

Re: Can't get the same damn oal depth! (ogive)

Here is a picture. the last time I tried to get a number was the 2.795

 

[SPAK]

Re: Can't get the same damn oal depth! (ogive)

Use thE same bullet and same brass and measure five or six times. Too much neck tension and the bullet will just jam in the lands giving you a false reading long. Too little tension and the bullet may get pulled out also giving you a false reading long. Either way I'd go by the shortest reading you have. But just use one bullet and case and measure several times.

It will get you close enough to start your load development.

A proper load development should yield a charge weight where small variances in seating depth shouldn't matter that much anyway.

 

[thespecialist]

Re: Can't get the same damn oal depth! (ogive)

I always take a piece of sized brass and split the neck down to the shoulder with my dremel. I had much more consistent measurements doing it that way. Splitting the neck on the brass will allow it to keep enough tension to hold the bullet without it having so much it jams the bullet into the lands.

 

[Headgear]

Re: Can't get the same damn oal depth! (ogive)

Have you tried a Hornady OAL gauge to find your chamber depth? It gives you great feel of the bullet going into the throat and seating against the lands. Then you lock it down and measure with your comparator and you have the your exact chamber depth. Then seat to that depth or back it off to gt whatever jump you are after.

 

[taseal]

Re: Can't get the same damn oal depth! (ogive)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: thespecialist</div><div class="ubbcode-body">I always take a piece of sized brass and split the neck down to the shoulder with my dremel. I had much more consistent measurements doing it that way. Splitting the neck on the brass will allow it to keep enough tension to hold the bullet without it having so much it jams the bullet into the lands.
</div></div>

I might do that are you splitting both the sides of the brass, or just one side? and how long of a cut are you giving?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Headgear</div><div class="ubbcode-body">Have you tried a Hornady OAL gauge to find your chamber depth? It gives you great feel of the bullet going into the throat and seating against the lands. Then you lock it down and measure with your comparator and you have the your exact chamber depth. Then seat to that depth or back it off to gt whatever jump you are after. </div></div>

I thought about that, but since they're not the same length as my lapua brass, I'll get a diff reading? I know it's off of the ogive, but you are still measuring from the head to the ogive, so shorter case will have a diff reading. I have a nice brass that it fit snug, but the brass was longer, so I was getting way diff readings then with the lapua brass

 

[The Mechanic]

Re: Can't get the same damn oal depth! (ogive)

I am sure it is obvious but are you sure you don't have any very slight deformity on the rim, primer pocket, or extractor mark that may be giving some measuring inconsistency? I have a solid machined chunk of steel that I have a sticky sided piece of sandpaper stuck to and a light little twist makes sure I don't have anything that would give me an area of error.

 

[Tomekeuro85]

Re: Can't get the same damn oal depth! (ogive)

+1 on using the same bullet repeated 5 or 6 times.

I did this and saw that my measurement was within .001 nearly every time.


Using a second bullet may throw you way off.


I seated it long, chambered it, and then moved it to my micrometer seating die and screwed that down until it met resistance. So now my seating die is set perfectly to a "zero" aka just touching the lands. This way I back it off .005 or move it up .005 and i know exactly where I am in relation to the lands. The die is permanent in that particular press so I never have to worry again as long as i use the same bullets.


Obviously the ogive varies, but this is about the best you can do unless you measure each bullet to exactly touch the lands. You can also sort the bullets themselves by length from base to ogive and this will be less of an issue when it comes to seating. But that just depends how far you're willing to go.

 

[shoot4fun]

Re: Can't get the same damn oal depth! (ogive)

For length to the lands I use the single case/bullet and black marker too. I seat very long, so long the round will not chamber and then just back it in a little at a time until I can see small square marks from the rifling appear in the black. That is unless I already have a Stoney Point modified case for that caliber.
As stated above, for best results, use the same bullet for all measuring.

 

[Heman]

Re: Can't get the same damn oal depth! (ogive)

Below is somthing I noticed over time and wanted to share.

The issue with the stoney point comporators is that they are not bored at a dimension to actually measure from the ogive. For example if you measure a 142 SMK and a 123 SMK you'll get 2 different measurements, you shouldn't becasue the ogive should measure the same however the stoney point tool measures up farther on the nose and with different nose shapes you get different measurements. I never pinned them to check diameter but if you check them on a tangent ogive bullet you will see they don't hit the ogive.

Sinclair's comporators are better I believe they are 0.002" under (ie. 7mm is bored at a diameter of .282" not .284") so they give you a more consistant measurement from bullet to bullet.

I went ahead and made my own that are about 0.0006" under (so 7mm is bored at .2834) that measures about as close to the ogive as you can get I found between the bullets I have. If I go any closer some bullets will slip through. With these now my ogive measurements are the same for the different loads I have for the rifle.

 

[9H_Cracka]

Re: Can't get the same damn oal depth! (ogive)

Do the test multiple times and use the mode for your value.

The bullet does change shape when jamming it in the lands over and over, so change the bullet out from time to time.

Generally I go through the bullet box and measure the base to ogive dimension of the bullets, find a mode for this, then set aside a pair for this type of work.

Once you get it pretty well dialed with bullet one, switch to bullet 2 to verify a few more times, then save this dummy round in the box/lot of bullets you are working with.

Do the base to ogive mode measuring on the next lot you use, adjust the micrometer die accordingly, and skip the jam in the lands test.

Also remember when setting your seating die up that the loaded rounds with a compressed load of powder under the bullet will have about .002" longer OAL than the dummy round with no powder.

 

[ubet]

Re: Can't get the same damn oal depth! (ogive)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: shoot4fun</div><div class="ubbcode-body">I understand the COAL being off. The best way to measure is to the ogive with the comparator you have. What were the measurements there? Closer, I would think.
I have a buddy that seats all his bullets twice, so to speak. He seats the bullet, backs it out of the die, rotates the entire cartridge about 90 degrees and runs thru the seater again. He swears it gives him more consistency but I just think he is OCD. </div></div>

Nope, I do the samething, it will seat them more consistently.

Op, I use steel 0000 steel wool instead of the marker (guys at sierra tech hotline told me that). Works for me.

good luck

 

[thespecialist]

Re: Can't get the same damn oal depth! (ogive)

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: taseal</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: thespecialist</div><div class="ubbcode-body">I always take a piece of sized brass and split the neck down to the shoulder with my dremel. I had much more consistent measurements doing it that way. Splitting the neck on the brass will allow it to keep enough tension to hold the bullet without it having so much it jams the bullet into the lands.
</div></div>

I might do that are you splitting both the sides of the brass, or just one side? and how long of a cut are you giving?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Headgear</div><div class="ubbcode-body">Have you tried a Hornady OAL gauge to find your chamber depth? It gives you great feel of the bullet going into the throat and seating against the lands. Then you lock it down and measure with your comparator and you have the your exact chamber depth. Then seat to that depth or back it off to gt whatever jump you are after. </div></div>

I thought about that, but since they're not the same length as my lapua brass, I'll get a diff reading? I know it's off of the ogive, but you are still measuring from the head to the ogive, so shorter case will have a diff reading. I have a nice brass that it fit snug, but the brass was longer, so I was getting way diff readings then with the lapua brass </div></div>


I only split one side. It gives it enough tension to hold the bullet, but you can pull the bullet back out by hand to remeasure several times. Just split the neck all the way down to the top of the shoulder, don't go any further than that. Using that method and the same bullet should give you results that are within .001" each time.

 

[softcock]

Re: Can't get the same damn oal depth! (ogive)

when Chambering a Round & getting a good reading on where to get a average on where the Lands are riding on your OAL .
I, 'Always' remove the ( Plunger & Spring ) out the Bolt for this purpose when slowly pushing & closing the Round in Chamber .
You don't need it's ' Influence ' involved @ all & I get better & more consistent without it .
.

 

[taseal]

Re: Can't get the same damn oal depth! (ogive)

Alright guys, I gave this another go...

I measured with 2 bullets. both get consistent 2.830.

then I take the 3rd bullet, and I get consistent 2.800!

I checked, both bullets are .307-.308 same exact ogive lengths for the bullets too...

I don't wanna go through a bunch of fricking bullets and see what's more common...

I mean I can pick 2.815, but then again, they say about .015 off the lands, and with that much difference, it won't make any sense!!!