Streetdoctor

New to reloading and I'm using a hornady OAL gauge and comparator.

My load is for 30-06, Nosler 180gr partitions, starting at 43grs IMR4064.

I measured my rifle using the OAL gauge 3 times and got 3.972" each time with the comparator. I subtracted 0.030" to get off the lands a little and came up with 3.942". If I subtract the comparator (1.007") that only gives me 2.935" for an OACL. That doesn't sound right when the Nosler manual says 3.340 is max OAL. Where did I screw up?

Streetdoctor

If I measure the OAL gauge without the comparator the number is 3.557. Subtracting .030" to get off the lands gives me 3.527" which is still 0.187" longer than Nosler recommends for max OAL. Do I just make them nosler max recommended of 3.340"?

Streetdoctor

Some more measurements. I seated them to an OACL of 3.380". There's 0.503" bullet inside the casing. They all cycle fine. Should I roll with this?

Wayspr

Subtracting 1.007 to get your COAL is not correct. The comparator measures off of the ogive, not the tip. You do not have 1.007" of the bullet inside of the comparator.

Do not worry about book max OAL in a bolt or single shot gun. Let your gun and magazine determine that. As a general guideline, most folks like to seat bullets so at least a caliber is in the case. In your case, that would be at least .308 of the bullet in the case. Other than that, stick them out as fasr as you want as long as they fit in your magazine, cycle and fit in your chamber.

Streetdoctor

Excellent thank you! This is where I was getting confused. I will use the numbers from the OAL gauge for my next batch.

Nomercy448

Wayspr, it's been a while since I've used a Hornady OAL gauge and Comparator (since I'm not really convinced this is a valid technique), but isn't the 1.007" a calibrated distance per each comparator that assumes the distance from the end of the comparator to the ogive IN the comparator?

So with this tool, what you actually measured, assuming that your calipers were zeroed on dead close, was the distance from the base of your case to the end of the comparator (or at least to the bottom of the SLOT in the comparator).

Then, if you assume that the comparator bushing ID's match your land ID PERFECTLY, then you can subtract the 'calibrated length' from your measurement and get your distance from the case base to the ogive.

That is why you got something around 2.935" instead of 3.340" as listed in your manual. You measured to the Ogive, not the tip. The 3.3xx number for COAL measures the entire loaded cartridge length, but for different bullet profiles and different rifles, COAL is irrelevant. The 2.935" was not the COAL (not analogous to the 3.340" COAL), but instead is the distance from the case base to where the ogive will touch the lands. So if you measure that 2.935" with the comparator, your COAL might actually be 3.340" with that bullet.

WHY THIS IS IMPORTANT:

Different bullets have different profiles. Bullet jump is typically far more important than COAL, so if you have a damaged tipped vs. a pristine tipped bullet, but seat to the same COAL, you might end up being several thousandths difference in jump, and a rifle will know the difference between an extra 0.015" jump a lot more than it will notice a difference in 0.015" extra tip hanging out front.

So basically, you can measure your bullet seating span with ANY bullet, and it will NEVER CHANGE FOR ANY BULLET. It's matched to your rifle. So if your rifle has 2.935" from the bolt face to the lands minimum ID (i.e. end of your throat), it will be 2.935" for any bullet, no matter what. BUT, for a long profile VLD, that 2.935" chamber span might correspond to 3.57", whereas with a heavy round nose it might only correspond to 3.32" (exaggeration).

There's also a problem with the Hornady OAL gauge, such that it needs to be zeroed and a calibration reference subtracted, but that's an entirely different can of worms.

At any rate: To properly use the Hornady Comparator and OAL gauge. Insert the modified case with a bullet in question, and determine your maximum seating length for that bullet. Pull it out, and measure using the comparator. Subtract the calibration length for the comparator from your measurement, then subtract your desired bullet jump length (the 0.03" you referred to). This number will be your ogive depth for THAT PARTICULAR RIFLE.

Then, without moving the bullet, measure your COAL, and subtract that same bullet jump length. This will be your COAL for THAT PARTICULAR BULLET.

So then when you switch to a new bullet, you can set your dies to seat to that same comparator length and never have to use your Hornady OAL gauge ever again. That WILL correspond to a different COAL, but it will seat your bullet to the same bullet jump that you want.

Clear as mud?

Wayspr

Yep, clear as mud. As always, I had to reread your post to fully understand.

Nomercy448

Well, I'm not quite sure if my last post was quite at the proverbial thousand words mark, but it was close...

This is what I was trying to say:



If you start with a zeroed caliper, then install the bullet comparator, THEN measure the loaded cartridge, you'll get the total length of the cartridge plus the comparator body, minus the tip of the bullet. This is "X". The calibration length for your comparator (the 1.007" you referenced before) is Y. Then X-Y = Z, which is the length from your bolt face to the ogive of your bullet.

Below is how I used to use the hornady comparator and OAL spindle. I've since gone back to using magic marker to 'smoke' my bullets again.

This is what I consider the PROPER WAY to determine seating depth and COAL using a bullet comparator:

This technique is based on a establishing and maintain a desired bullet jump for a given rifle's chamber. I want to hold this bullet jump constant no matter what bullet I use, or if the tip of a bullet is damaged. There's more than one "right way," but this is how I've used it with good results.

The diagram below is an exaggeration comparing the ogive positions and proper COAL/Seating Depth determinations for a long profile spire point and a heavy round nosed bullet. This compares two methods for seating bullets based on two different control lengths. The WRONG path A-->B-->E uses a fixed COAL, but as you can see, it ends up seating the bullet too long and jamming the rifling - which can be dangerous. The CORRECT PATH: A-->D-->F-->C determines the proper seating depth for a given bullet, then determines the proper Ogive position for THAT RIFLE and keeps the OGIVE POSITION CONSTANT, meaning the COAL would change between different bullets.




So this is a bit exaggerated, but this is what I'm talking about.

If a reloader only goes by COAL targets, they can get themselves in trouble. Using a bullet comparator, IN THEORY, will let you properly seat any bullet to match your rifles chamber:



In this image, Cartridges A, B, and C from the caliper graphic are shown. A was properly seated based on smoke testing or Hornady OAL spindle. B was NOT properly seated, because the reloader used the same COAL as A, but with a fatter profile bullet so it's now jammed heavily into the rifling, which may create a dangerous pressure condition. The bullet ogive for Cartridge C was matched to A by using a comparator, so the proper bullet jump was maintained, and the bullet was properly seated to match the rifle in use.

The process:

Determine the proper seating depth for your specific bullet to give the bullet jump that you want - doesn't matter whether you use the Hornady OAL spindle and Modified Case or old fashioned "smoking" technique. This produces the cartridge in Caliper A.

Once you establish your exact COAL appropriate for THAT BULLET IN THAT RIFLE based on its ogive position, you can use the bullet comparator to determine the distance between your bolt face and ogive position to produce your desired bullet jump for THAT RIFLE, that will be consistent for ANY BULLET. Caliper D above.

Then if you ever choose to change bullets, you can seat the new bullet to have the same bullet jump by seating the bullet ogive to the exact same position with the comparator. Caliper F above.

I personally just set my dies based on the comparator, but if your tips aren't deformed, you can then use that properly seated bullet to determine the appropriate COAL for THAT RIFLE with THAT BULLET. Caliper C above.

OR YOU COULD JUST SMOKE THE NEW BULLET THE SAME WAY YOU DID THE ORIGINAL BULLET.

The WRONG PATH: Some guys will fixate on a given COAL, but COAL is 100% irrelevant as you change bullets because the profile changes. Keeping COAL the same but changing bullet profiles would change your ogive position relative to your bolt face, meaning your bullet jump changes, which could create a dangerous pressure condition.

You've determined the proper seating depth and COAL to give you your desired bullet jump with the first bullet. Caliper A.

Then you use the SAME COAL for your new bullet. Caliper B.

But the heavy round nosed bullet obviously has it's ogive further forward than the spire point. When measuring this bullet seated to the same COAL as the original bullet, it's now jamming the rifling, which might over create an over-pressure condition. This is indicated in Caliper E above, the length from the case base to the bullet ogive is much longer.

Nomercy448

I forgot to mention...

Of course all of that has to coincide with having the proper neck tension to hold the bullet in the case. As others mentioned, about 1diameter is plenty to hold securely.

If you try to seat to say, 0.020" off of the lands, but you only have 1/4dia in your neck (VLD type bullets), then your chamber isn't suited for that bullet. New bullets are cheaper than new barrels. (again, an exaggeration).

Big Uncle

Perhaps it would be more helpful if you explained more thoroughly, and maybe include a diagram or two.

Kidding aside, you really put in the effort to be helpful.