In consistent reading on Hornady Headspace comparator

[K22]

I don't use the Hornady tool, but my buddy did and had problems.

We trace it to a couple of areas:

1. The anvil was not cut square and each time he placed in the caliper it aligned differently causing erratic readings. He tossed the anvil.

2. We placed match marks on the insert and holder, so it aligned the same each time. One of the reasons I like the Whidden gauge is that it's caliber group specific and single pieced construction with no inserts.

3. Consistent measurements require some practice with employing consistent technique, consistent pressure and rotating the case in the caliper so it seats square and uniformly. Practice on one case / bullet until you get consistent measurements. When you do, either write down the technique or commit to memory that which gave you consistent readings.

4. If you're measuring bullets, expect some variations in ogive even in quality bullets like Sierra and Nosler.

As others have said, the spent primer must be seated below the case. I like to remove the spent primer using a die specifically made for this purpose to eliminate any chance of it interfering with the measurement process.

 

[SKWERLZ]

Its your bullets. Your seating stem contacts them at a different spot than the comparator. Measure the same one multiple times and see if you get the same measurement so you can rule out your calipers and comparator

I thought he was talking headspace but then OP mentioned sticky bullets?????

 

[GetReal]

Its your bullets. Your seating stem contacts them at a different spot than the comparator. Measure the same one multiple times and see if you get the same measurement so you can rule out your calipers and comparator

When measuring seating depth / lands engagement, that's what I do....take about 5 readings. If done right / consistently, it'll usually give me a range of about 5 thou. Close enuf, I guess. It seems to be giving me good enuf data to get 0.25 - 0.40 groups at 100 yd.

 

[Geezedtee]

OK. So, knowing that even the best bullets have an ogive measurement that can be .002" different. And knowing that the Hornady comparator can give slightly varying readings of Cartridge Base to Ogive (CBTO). My question is: Does one seat the first bullet to the required CBTO, then leave the seating die setting alone and accept the variance in the CBTO? For example if the first bullet seated measures 2.103" in the comparator, then the next 2 measure 2.104"and 2.105", should you adjust the seating die to make those bullets measure 2.103"? Or accept the variance as a workable tolerance and leave the die setting as it is?

 

[Tesoro]

Clean your bore/throat really well before trying to get a cbto measurement before worrying about differences measured in a few thousanths. Use the hornady anvil base adapter instead of trying to center the case base on the anvil.

 

[Ned Ludd]

OK. So, knowing that even the best bullets have an ogive measurement that can be .002" different. And knowing that the Hornady comparator can give slightly varying readings of Cartridge Base to Ogive (CBTO). My question is: Does one seat the first bullet to the required CBTO, then leave the seating die setting alone and accept the variance in the CBTO? For example if the first bullet seated measures 2.103" in the comparator, then the next 2 measure 2.104"and 2.105", should you adjust the seating die to make those bullets measure 2.103"? Or accept the variance as a workable tolerance and leave the die setting as it is?

I would not do this if the best possible precision was my goal. The most common reason for seating depth variance (i.e. CBTO variance) of a magnitude greater than about .003" to .005" between loaded rounds is length variance in the nose region of the bullet. This is why: the seating die stem contacts the bullet out near the meplat to seat it down into the case. However, the caliper insert seats somewhere just above the top of the bearing surface on the bullet ogive. Any length variance between these two points will by necessity cause seating depth variance. This is not a die problem, it is not a press problem, it is a bullet problem, and one that can be solved by length sorting bullets.

In my hands, a typical Lot# of Berger bullets might have between .015" and .020" OAL variance. In contrast, length variance of the bearing surface or base-to-ogive dimensions is less by about one order of magnitude. What that means is that for the bullets I'm using, about 90% of the OAL variance lies in the nose region of the bullet, not the bearing surface or boattail. Now that could easily be different for other caliber Berger bullets than what I'm typically using, or for bullets from different manufacturers. Nonetheless, the easiest way to know that is simply to measure the bullet dimensions for a sample from any Lot of bullets you're using. If you find like I have that the lion's share of bullet OAL variance lies in the nose region, you can then simply sort bullets by OAL and it will improve the consistency of your CBTO measurements. Sorting bullets by OAL is simple, does not require a huge amount of time/effort, and may possibly relieve the uncertainty/mental trauma of inconsistent seating depth, even to the extent of having to adjust the seating die micrometer for every bullet; something I would never attempt. Anyone that owns a decent set of calipers already has everything they need to accomplish it. An alternative to this approach would be the use of a tool such as the Bon Green Comparator that actually allows [length] sorting of bullets based on the distance between the seating die stem contact point and the caliper insert point. However, if you don't own Bob's tool already, you'll have to buy it. Sorting by OAL is kind of a "poor man's" BGC tool, but it will work if the majority of bullet OAL variance lies in the nose region.

A different cause of seating depth inconsistency can be the reloading press itself, but the CBTO variance caused by this source is usually much smaller, let's say </= .001" to .002" or so. Another technique you can try to possibly address this type of seating depth variance lies in how the die micrometer is set. I start with the micrometer set a couple or three thousands longer than I think it should be from prior measurements and then dial down the die micrometer such that about 75% or of the bullets are seated to within .0005" of the desired CBTO value on the first stroke, with none being shorter than that range. If you get one with a CBTO of about .0005" to .0015" longer than desired, you simply put it back in the press and give it another stroke with the ram. It is usually possibly to seat the bullet another .0005" to .0015" deeper in the case using a 2nd, or even 3rd stroke of the ram without ever having to alter the die micrometer setting.

 

[hpshooter]

The Hornady ones are junk. Save yourself the hassle and doubt and invest a few more bucks into SAC, Sinclair, 21st century, Accuracy One, etc

Whidden makes steel inserts that fit the Hornady base. I have one I use on my 6.5x47.

 

[Old Navy]

OK. So, knowing that even the best bullets have an ogive measurement that can be .002" different. And knowing that the Hornady comparator can give slightly varying readings of Cartridge Base to Ogive (CBTO). My question is: Does one seat the first bullet to the required CBTO, then leave the seating die setting alone and accept the variance in the CBTO? For example if the first bullet seated measures 2.103" in the comparator, then the next 2 measure 2.104"and 2.105", should you adjust the seating die to make those bullets measure 2.103"? Or accept the variance as a workable tolerance and leave the die setting as it is?

I do. And I am usually at .001 or less.

 

[Mark W]

I must me extremely lucky! After reading how bad the Hornady tool sucks, I went downstairs and checked a loaded round that just so happened to measure exactly what i had labeled on the box. Just for fun I measured the same loaded round 10 times in a row making sure to completely remove the round from the tool and caliper each time. You guessed it. I got the same measurement 10 times in a row!

I’m confident that when I see base to ogive variations from one round to the next, it’s either the bullets or a neck tension issue and not the Hornady tool.

 

[Geezedtee]

I would not do this if the best possible precision was my goal. The most common reason for seating depth variance (i.e. CBTO variance) of a magnitude greater than about .003" to .005" between loaded rounds is length variance in the nose region of the bullet. This is why: the seating die stem contacts the bullet out near the meplat to seat it down into the case. However, the caliper insert seats somewhere just above the top of the bearing surface on the bullet ogive. Any length variance between these two points will by necessity cause seating depth variance. This is not a die problem, it is not a press problem, it is a bullet problem, and one that can be solved by length sorting bullets.

In my hands, a typical Lot# of Berger bullets might have between .015" and .020" OAL variance. In contrast, length variance of the bearing surface or base-to-ogive dimensions is less by about one order of magnitude. What that means is that for the bullets I'm using, about 90% of the OAL variance lies in the nose region of the bullet, not the bearing surface or boattail. Now that could easily be different for other caliber Berger bullets than what I'm typically using, or for bullets from different manufacturers. Nonetheless, the easiest way to know that is simply to measure the bullet dimensions for a sample from any Lot of bullets you're using. If you find like I have that the lion's share of bullet OAL variance lies in the nose region, you can then simply sort bullets by OAL and it will improve the consistency of your CBTO measurements. Sorting bullets by OAL is simple, does not require a huge amount of time/effort, and may possibly relieve the uncertainty/mental trauma of inconsistent seating depth, even to the extent of having to adjust the seating die micrometer for every bullet; something I would never attempt. Anyone that owns a decent set of calipers already has everything they need to accomplish it. An alternative to this approach would be the use of a tool such as the Bon Green Comparator that actually allows [length] sorting of bullets based on the distance between the seating die stem contact point and the caliper insert point. However, if you don't own Bob's tool already, you'll have to buy it. Sorting by OAL is kind of a "poor man's" BGC tool, but it will work if the majority of bullet OAL variance lies in the nose region.

A different cause of seating depth inconsistency can be the reloading press itself, but the CBTO variance caused by this source is usually much smaller, let's say </= .001" to .002" or so. Another technique you can try to possibly address this type of seating depth variance lies in how the die micrometer is set. I start with the micrometer set a couple or three thousands longer than I think it should be from prior measurements and then dial down the die micrometer such that about 75% or of the bullets are seated to within .0005" of the desired CBTO value on the first stroke, with none being shorter than that range. If you get one with a CBTO of about .0005" to .0015" longer than desired, you simply put it back in the press and give it another stroke with the ram. It is usually possibly to seat the bullet another .0005" to .0015" deeper in the case using a 2nd, or even 3rd stroke of the ram without ever having to alter the die micrometer setting.

Thank you Ned for your comprehensive reply. That all makes sense and will spare me the 'mental trauma' that was verging on OCD.

 

[SKWERLZ]

I must me extremely lucky! After reading how bad the Hornady tool sucks, I went downstairs and checked a loaded round that just so happened to measure exactly what i had labeled on the box. Just for fun I measured the same loaded round 10 times in a row making sure to completely remove the round from the tool and caliper each time. You guessed it. I got the same measurement 10 times in a row!

I’m confident that when I see base to ogive variations from one round to the next, it’s either the bullets or a neck tension issue and not the Hornady tool.

Same.
Once you get a feel for how they work they give good results.

 

[209jones]

Pressure on the caliper can create whacky readings. I use a Forster datum dial, it works well for me, holes are proper size, no searching for the right size insert, it's simple.

 

[Minshooter]

It can be helpful to keep a control round -just case and bullet.
Use as needed to insure your measuring tool settings are consistent.
Some superglue in the case mouth before seating the bullet can't hurt.

 

[rijndael]

It can be helpful to keep a control round -just case and bullet.

Yes!

It's especially handy if you misplace your comparator and have to replace it, or switch brands.

 

[divingin]

I'm thinking maybe the one size for the 7mm is a little off. So, as I square up and turn the cartridge I inducing whatever the variance is where the bullet touched the comparator.

Doesn't matter if it's off or not, as there's no actual "standard" for a comparator. The tool compares one reading to another; it doesn't measure anything.

It sounds to me like you're getting inconsistencies in your technique (though that's just a guess.) Try measuring the same cartridge a few dozen times and see if the variance remains.

 

[Ackman]

I'm pretty new to using a HS Comparator. I have/use the Hornady aluminum head space comparator and can't seem to get a consistent reading. I.e I'm loading a 145LRX 20 thou off so 2.6460. I'm using a clean Redding micrometer Comp die, a MEC press and using a Mitutoya caliper. I measure every few rounds as I seat for consistency. I'm coming up with 2.640, 2.650, 2.630 etc.

What am I missing? I can 'feel' the bullets kinda stick to the comparator. Feels like the copper and aluminum aren't real smooth together. I'm thinking the comparator isn't as accurate as I'd assumed. Any ideas? I'm looking at the Short Action Customs SS comparators.

It's the bullets, at least for me. I use a Davidson ogive gauge and like you check seating depth every several rounds when loading. Using a Redding comp seater and have also experienced some pretty large variations. It's not the die either. I empty bullets from the box into those round pop top rubbermaid plastic food containers, about 5" across and 2+ inches high, labelled and stacked. The problem lies with mixing boxes with different lot numbers together. The variation in ogive length can be substantial, sometimes huge. You can't maintain consistent seating depth with bullets that are all over the place. I've seen this with Nosler, Hornady, and Sierra to more or lesser degree. Even occasionally pretty large variations within the same box. These are noncustom varmint bullets. Now I don't mix lot numbers anymore and measure to a bunch from each box just to satisfy myself they're close to the same. It's not the comparator.