• Winner! Quick Shot Challenge: What’s the dumbest shooting myth you’ve heard?

    View thread

Measurement to ogive --- need confirmation

Bob 964

Bob 964

Sergeant
Minuteman
Feb 10, 2011
375
1
Tallahassee, Florida
#1
I used my Hornady L-N-L Overall Length Guage and Comparator for the first time today to measure the length to the ogive for the following .308 bullets: SMK 175, SMK 168, Lapua Scenar 155, and Hornady 178 A-Max.

I used a cleaning rod to better "feel" the bullet as it touched the rifling. I selected 5 bullets at random from each box for measurement. Here are my results (inches):

178 A-Max: 2.258, 2.260, 2.257, 2.253, 2.252 (ave. 2.256, median 2.257)

175 SMK: 2.269, 2.274, 2.266, 2.263, 2.263 (ave. 2.267, median 2.266)

168 SMK: 2.268, 2.267, 2.274, 2.274, 2.279 (ave. 2.272, median 2.274)

155 Lapua: 2.261, 2.265, 2.265, 2.258, 2.266 (ave. 2.263, median 2.265)

It felt like I was doing this right, but it's my first time so I don't know. I am hoping that those of you who are familiar with this procedure and these bullets can tell me if these measurements look right.

Thanks.
Bob
 
#2
Re: Measurement to ogive --- need confirmation

Every barrel is different so hard to say that it looks right or wrong. I can tell you on my Remington factory barrel with Sierra 175's my measurement is 2.370. Even though mine is .100+ longer than yours doesn't make yours wrong so just giving example.

Some suggestions, make sure chamber and barrel are clean. Doesn't take much of anything to throw measurement off. Set rifle up in cleaning stand or gun vise so it's very stable. I would do multiple (5 or more) measurement with the same bullet. This will make sure you're doing it the same way and getting repeatable results. My first attempt at using the guage I had a spread of .009. Once I got the feel of it measurements really tightened up. My last check I did 10 measurements with same bullet, 7 measured 2.3700 the other 3 measured 2.3695.
 
#3
Re: Measurement to ogive --- need confirmation

Good advise from Crewchef.

I use a wooden rod from home depot,..it seems to give me a better "feel" as I push on the bullet. I keep a little tension on the little plastic tool rod and move the bullet back and forth with the wooden rod and the tool rod. You can get a decent "feel" when the bullet hits the lands.

I always like to get consistent / repeatable readings,..much of that can depend on your technique. I will usually take 10 or so readings before I lock in own what seems to be the "actual".
 
#4
Re: Measurement to ogive --- need confirmation

I did use the cleaning rod and the plastic rod in the gauge to move the bullet back and forth until I felt the bullet touch the rifling. I will remeasure 10 of each size bullets to see if the range of measurements tightens up any. The instructions that came with the gauge discuss repeated practice to acquire a certain 'touch" or "feel" when the bullet touches the rifling, so... I will keep practicing.


PS - the rifle is a Savage 110FP .308 with 1:10 twist.
 
#5
Re: Measurement to ogive --- need confirmation

I seem to be really struggling to find the "touch", as I am getting a pretty wide range of measurements for the same bullet. Do you push the rod lightly until you make contact with the rifling or do you push lightly until the bullet stops? I ask this because if I continue to push lightly after contact the bullet will continue to move forward until it feels like it is "seating", and then it stops moving.
 
#6
Re: Measurement to ogive --- need confirmation

Hope I am getting the hang of this. Lightly pushed the rod until the bullet stopped. Measured same bullet 10 times. Here are my results:

178 A-Max: 2.262, 2.262, 2.267, 2.262, 2.262, 2.263, 2.262, 2.264, 2.264, 2.264 (ave. 2.263, median 2.263, range 0.005)

175 SMK: 2.296, 2.293, 2.302, 2.298, 2.299, 2.295, 2.298, 2.297, 2.290, 2.296 (ave. 2.297, median 2.297, range 0.013)

168 SMK: 2.290, 2.292, 2.294, 2.291, 2.293, 2.293, 2.290, 2.292, 2.292, 2.290 (ave. 2.292, median 2.292, range 0.004)

155 Lapua: 2.272, 2.278, 2.273, 2.272, 2.273, 2.272, 2.273, 2.271, 2.277, 2.278 (ave. 2.274, median 2.273, range 0.007)

Planning to talk to Sierra and Hornady bulletsmiths tomorrow for validation and further advice.
 
#7
Re: Measurement to ogive --- need confirmation

Take a peice of your older brass and slit the neck with a dremel tool and a diamond cutting wheel. Clean up the cut with a brass brush and polish the inside case neck with a brucsh wrapped with #0000 steel wool.

After you have that done you can control the tension on the bullet you wish to measure by slightly crimping the neck together.

Put a bullet you wish to know the exact dimension to the lands in the neck and chamber the round. Carefully extract the shell from the chamber and measure. This will confirm your numbers.

DSCI0003-6.jpg


Terry
 
#9
Re: Measurement to ogive --- need confirmation

You're getting there, just need to stay with it until you can get the hi/low range to tighten up. Standing to side of rifle I use pad of my index finger to push the plastic rod. When I feel it touch I give the rod a slight tap (very light) to make sure it's making good contact.

One other tip I should have mentioned. Hold the rod in place when tightening the set screw. If you don't it seems like it moves the rod ever so slightly. I just keep a little light forward pressure on it. Doing this is what really tightened my hi/low ranges up.
 
#10
Re: Measurement to ogive --- need confirmation

Thanks Crewchef. I am still unsure whether you push the rod in just until contact is felt, or whether you continue to lightly push the rod until the bullet stops moving. The bullet will continue to move (albeit slightly) after initial contact is made if I continue pushing.

To your point, I do hold the rod in place when tightening the thumb screw.
 
#11
Re: Measurement to ogive --- need confirmation

Reference my mention of the "tap" above. I want to know when it's actually there not just some slight feel of it touching something on way in. Nice steady pace and pressure with slight tap at end. At that point bullet is touching the lands. Not trying to drive it in there just up tight against.
 
You must log in or register to reply here.
Top Bottom
Back
Home
Forums
Merch
Alerts