Measuring Ogive - Results and issues

[Yerman]

I am using the Hornady OAL gauge and bullet comparator set to measure the ogive of my 308. Here are the results...

2.3380
2.3365
2.3380
2.3325
2.3230
2.3280

I am doing my best to apply the same amount of light pressure to touch the lands but I expected much better accuracy using this method. Any thoughts on the large variation and how to get a more consistent measurement? Ho about a different method?

Also, at this depth, my 175gr SMK bullets are barely inside the case. Is this just the nature of a factory barrel?

[baih777]

Is this a new barrel or an old barrel.

[baih777]

Checked my notes for my 5R. I measured it at 2.32. The Remington measured .010 more than my savage and how's.

[pacrat]

Military chambers, most factory chambers, and Marylin Chambers have one thing in common with Linda Loveleace.

[Archon_g24]

I have trouble getting my caliper properly positioned under the modified case. This causes the caliper to be offset which affects my ability to get a consistent measurement.

Are you having this problem too?


Edit:
Check out post #10 if you're experiencing what I described.

http://www.longrangehunting.com/forums/f28/hornady-oal-guage-53793/index2.html

[baih777]

this is what will happen loading to ogive with my 5R. if you load a round to the measured ogive, your OAL will be too long for the magazine assuming you have a AI mag.
your OAL will end up 2.90. my mags will take 2.88. I just load my 5R to 2.85 OAL.
just not ready to modify the mags yet.

you may need to make sure your modified case is flat on the bottom. if not some 400 grit or 600 grit on a flat surface, and sand lightly till smooth. when I use the guage I use my thumb where the calipers fit to the bottom and I can hold the caliper flush to the case and get good measurements.

[Yerman]

Is this a new barrel or an old barrel.

Brand new SPS Varmint 308. 40 rounds down the pipe

[bigdawg86]

I'm having a similar issue... For my Lapua I am choosing to use my brass then I seat the bullet long. Can't close bolt? Seat bullet lower. Once the bullet closes to your liking you are essentially at the lands. I then use a lighter I make the bullet completely black with soot, then try and chamber. You should get a nice ring in the soot which tells you where the lands is on the bullet.Seat a few thousandths deeper. Re-blacken the bullet. Once that "ring" no longer marks the bullet, then I know I am just off the lands. I then use that measurement as my starting point as "x amount off the lands"

So black ring present, bolt closes = on the lands.
No black ring, bolt closes = X amount off the lands.

This won't work as well on a semi I'd imagine

[bsumoba]

This is the best way to do it that I have seen and many top shooters do it this way. This will most accurately represent for your chamber and a specific bullet, where the "touch" is for your case. Once you know this, take a comparator that references off the bullet ogive and measure and write it down for safe keeping, preferably a log book where hopefully you are also taking down notes of your shot count and other pertinent data.

IMO, the hornady OAL gauge is a good start, but it is very hard to control and by the time you feel it touch, chances are you are actually jamming 0.010-0.020" already. So, if you think you are "jumping" 0.010-0.020, you actually might be teetering on jamming/jumping, which may cause variations in pressure, leading to inconsistent groups and velocity...bad for long range or precision shooting.

There are some things the person needs to be able to do though...

* You need to take the firing pin assembly out
* You need to also take out the ejector (held in usually with a roll pin)

The rest of the video explains the rest.

[bigdawg86]

My Savage rifle has that resistance with raising the bolt even without a cartridge in the chamber... So I can't do it by feel like the video. Oh well

[bsumoba]

My Savage rifle has that resistance with raising the bolt even without a cartridge in the chamber... So I can't do it by feel like the video. Oh well

take the whole firing pin assembly out. wait, not sure if u can do that with a savage...

[Pardini]

Check your loaded rounds for concentricity.

[bigdawg86]

Check your loaded rounds for concentricity.

Never done it... Checking is one thing, can you fix it if it's off?

[bsumoba]

Check your loaded rounds for concentricity.

If he is using an ejector, then there is no point in doing this. the round will be canted to one side in the chamber regardless, due to the ejector applying a constant force against the case head.

[LynnJr]

The best and easiest way to measure the ogive length is with a bullet comparator. I don't know of anyone using the Hornady tool and I don't see it's purpose.
When you are using your comparator your primers need to be seated below flush or this will affect your readings if your measuring live rounds.
You mount the comparator to your digital caliper insert the round and close the jaws. You then lightly rock the casehead in the jaw looking for your shortest measurement.
This assures you that you have the casehead centered over the jaw of the caliper correctly.
The variation you see using this method will be the variation in the bullet and is why the top shooters either use custom bullets or sort mass produced bullets.