Hornady Comparator vs OGIVE

[bigdawg86]

I made a interesting "discovery" today. I have the Hornady Comparator and OAL gauge which I have been using to TRY and figure out my freebore / lands distance to use as guide while reloading.

I know (Thanks to LynnJr) that your freebore / lands should be the same measurement regardless of bullet profile or brand, which makes sense. I began getting frustrated because I was getting wildly different readings today from measurements I wrote down 1-2 months ago.

I decided to break down by bolt carrier group, soot up the bullet with a lighter, and starting long continued seating deeper until the bolt "locked". This is similar to the method used with bolt action rifles.

Well here is a picture of my results. This also revealed to me that the comparator is nowhere near the actual bullet OGIVE. Using this method, I was able to get a true measurement (much longer than previously thought).

Moral of the story?

The Hornady system provides a better reference point that measuring COAL, but does not provide what I thought it did... a measurement that indexed of bullet OGIVE. I will now soot up the rest of the different bullets in my stable and measure as described to obtain a better reference point that I can use when seating bullets.

I know. Cool story bro.

[dwalker]

I am actually in need of a new OAL tool, I too had the Hornady but I loaned it out to someone who is apparently never going to return it, and I was just wondering what the new hotness OAL/Ogive tool was out there, so maybe this will save me a bunch of snooping around other forums.

[bsumoba]

People have made comparators with their own reamers that way you had a tool that referenced off the point where your bullet would actually touch the lands.

That being said, I do not understand what you mean by "your freebore / lands should be the same measurement regardless of bullet profile or brand, which makes sense". If you have a different bullet, you will most likely get a different CBTO (cartridge-base-to-ogive) measurement. If I use 105 hybrids, the CBTO is vastly different than if I used 108BT.

Also, chances are, your measurement to your lands may not be the actual moment it kisses the lands. This is because you can "jam" a round rather easily, 0.030-0.040" into the lands and not know it. This is easy to do in a semi-auto rifle or when using one of those hornady OAL gauges. The moment you "feel" the round touch the lands, you are more than likely 0.010-0.040" jammed into the lands. How would you know this? Well, if you use the hornady OAL gauge and you push a bullet forward until you feel it stop, then why is that you need a cleaning rod to "pop" the bullet out? It is because it is actually stuck in the lands.

This is the best way to measure actual distance to the lands that I have come across (vid below). Of course, it is only beneficial if you know how to remove the ejector and firing pin assembly off your bolt action rifle. I am not aware of a good way to do the same thing for a semi-auto. My answer to the semi-auto is to not care about the measurement, and to load to max magazine length and develop a load at that length, or to load a round about 0.030" short of max mag length, develop a load for powder charge, then tune the seating depth.

[bigdawg86]

That being said, I do not understand what you mean

[bsumoba]

Well technically speaking, each bullet, regardless of brand or profile would engage the rifling in the same spot... So if you were accurately able to say for example 2.250“ is CTBO, then it will always be 2.250"... If using a 100g bullet then you may not be able to engage the lands and have a huge jump as opposed to a 140g, but the distance from the case neck to the lands, remains the same.

Yes, this is true..unless your throat erosion is bad. I figure about 0.003" of erosion per 100 rounds, but that is in my F-Class rifles, where the barrels take a lot of abuse due to the long strings of fire. Interesting thing is...once I find a load in a new barrel, my load almost never changes. I don't chase lands or anything, and I have shot very well. Of course, a huge part of the game is mental, so if you believe that chasing the lands helps with precision and accuracy, keep doing it. I just have never seen the need to do it, mainly because I will retire a barrel from major competition after about 1,000 rounds. I also have done my fair share of testing and for me, I found no difference. I've tested all the "methods" that claim to increase accuracy and my reloading has actually gotten more simple, but my scores have gotten better...probably because I am shooting more and reading the wind better

Since the Hornady gauge does not hit true ogive, then measument will be different.

Not necessarily true. The comparator is indeed only a reference point and does not match the "ogive" point, but if your bullet is the same, the dies were not changed, etc., then the value on the caliper should also remain the same. You must have had something else change. Change in neck tension, different lot # of the bullet (different lot#'s of the same bullet could actually have different base-to-ogive numbers), changing from wet tumbling to dry tumbling, etc can change your measured value. Also, the quality of the bullet is a big factor. If you are measuring bullets like bulk bullets, do not expect consistent values. If you are using match bullets from Berger or Sierra for example, these will give much more consistent numbers.

[bigdawg86]

With firearms, strictly speaking (my inner sicko is making innuendos as we speak) ... Can one throat be tighter than others?

I feel like that's what it leading to my inconsistent measurements...
I cannot advance my bullet far enough down the throat due to resistance, and was unable to get the measurements I did until I did the soot method. It's a new Lilja barrel with maybe 250 down the pipe

[pacrat]

I think you may be tripping over nomenclature semantics. The chamber remains the same, it's relation to the bolt face remains the same, the leade remains the same.

Ogive: simply stated means "arch or curve". Not all arches are created equal.

The name of the tool is a "comparator". It makes no definitive measurements. It only makes comparisons. That's why in 49 yrs of reloading I never bought one.

What changes is the point on the ogive that the bullet contacts the lands. That is not a constant. It is governed by the lenght of bullet, and whatever the ogive of each style bullet you use is. Which all have a different contact point with the lands.

That ogive "contact point" is best described as a diameter at a set dimension from the bolt face. Since differing bullets have differing ogives, there is no "one size fits all".

[bsumoba]

With firearms, strictly speaking (my inner sicko is making innuendos as we speak) ... Can one throat be tighter than others?

I feel like that's what it leading to my inconsistent measurements...
I cannot advance my bullet far enough down the throat due to resistance, and was unable to get the measurements I did until I did the soot method. It's a new Lilja barrel with maybe 250 down the pipe

Chambers will vary from rifle to rifle. The only way to truly know you have a chamber made by the same reamer is to own that reamer and have the gunsmith chamber your rifle with that reamer. Otherwise, you may see slightly different dimensions in the chamber. Factories use multiple reamers to keep up with demand and production. Those reamers have tolerances and are not all made exactly the same. So, you and your buddy could have the same rifle, made by the same manufacture and the chamberings could vary slightly. Are you trying to compare one rifle's measurements with another? If so, you are wasting time.

What you could be running into is loaded round runout. When you load a bullet into a brass case, there is some amount of runout (how concentric the bullet is relative to the center axis of the case). If you can imagine that you only have 0.0004" of clearance on each side of a bullet in the freebore region of the chamber, That is not a whole lot. Any amount of runout could cause false measurements of your touch point to the lands.

[ar15barrels]

With firearms, strictly speaking (my inner sicko is making innuendos as we speak) ... Can one throat be tighter than others?

5.56 chambers have 0.002" larger diameter freebore than 223 wylde or 223 Saami chambers.

[bigdawg86]

5.56 chambers have 0.002" larger diameter freebore than 223 wylde or 223 Saami chambers.

Good to know... Although I failed to mention this is semiautomatic 6.5 Creedmoor.

I enjoy semi's but the lack of consistency is why I am starting to peak interest and gravitate to bolt actions.

[bsumoba]

Good to know... Although I failed to mention this is semiautomatic 6.5 Creedmoor.

I enjoy semi's but the lack of consistency is why I am starting to peak interest and gravitate to bolt actions.

semi-auto 6.5 creedmoor rifles also eat brass like crazy from what I have seen.

Yes, go to bolt actions and join the dark side.

[jimmykan]

Before I got the Sinclair Hex Style Bullet Comparator, I used the seating plug from the bullet seating die to measure cartridge base to "ogive".

This would be my ideal bullet ogive measurement tool.

[LynnJr]

BSumoba
If I read your post correctly your throat erodes 0.003 per hundred rounds fired and you never change your seating depth for the 1000 shots you fire in your barrels before they are retired?
If that is correct you can have 0.030 variation in your seating depth and still keep your same level of accuracy?
Sound right to you?
And yes a short round nose bullet contacts the lands at the same exact distance as a very long pointy super VLD bullet does.
The OAL is different but the comparator length is the same unless your comparator is broken or your shooting bad tolerance bullets.

[bsumoba]

BSumoba
If I read your post correctly your throat erodes 0.003 per hundred rounds fired and you never change your seating depth for the 1000 shots you fire in your barrels before they are retired?
If that is correct you can have 0.030 variation in your seating depth and still keep your same level of accuracy?
Sound right to you?
And yes a short round nose bullet contacts the lands at the same exact distance as a very long pointy super VLD bullet does.
The OAL is different but the comparator length is the same unless your comparator is broken or your shooting bad tolerance bullets.

Big Dawg's OP was confusing. He said "I know (Thanks to LynnJr) that your freebore / lands should be the same measurement regardless of bullet profile or brand, which makes sense. I began getting frustrated because I was getting wildly different readings today from measurements I wrote down 1-2 months ago." This makes it sound like he's using a comparator of some sort, which means that the measurement will be different, depending on the bullet he is using.

And yes, I do not change my seating depth and seem to be doing just fine. IMO, when shooting LR (and this may apply more to F-Class than LR Benchrest), ones ability to read the wind, the environmental conditions and how you perceive those conditions in the scope and adjust for it are usually bigger factors in whether or not you score well or have smaller groups.

If it was a big wind tunnel with nothing imparting force on the bullet, or if you are shooting shorter ranges (thus, outside factors have less of an impact on your bullet while in flight), then maybe it matters. Isn't that why the best guns in the world (short range BR) are shot by shooters who are loading at the range and changing their load based on the conditions? If you aren't doing that, then maybe that is where tuners can help. But, most of us don't do that either.

How many of us have gone to the range and the gun shot phenomenal, then you go out a different day and it shoots worse with the same load? What changed? Many have gone back to try to find that perfect spot, thus putting more rounds down their barrel, only to "tune" the load for that day, but who's to say that it won't shoot poorly another day? What I am trying to get at is IMO, we overthink load development and trying to tune a gun, when in reality the very thing that can help a shooter the most is simply going out there, shooting and learning to read the wind and the conditions and try to factor that in when pulling the trigger. Load to the middle of a charge weight, play with seating depth in large increments, maybe 0.010 increments and when you get a load that shoots as consistent as you can get it to shoot, don't change it. If it shoots poorly one day, don't think that the gun is out of tune and start messing with the load again. Just chalk it up to a bad day or conditions were just screwy that day. If the load shoots poorly on multiple days, chances are you probably don't have a good load to begin with that can withstand variable conditions. At that point, maybe go back to the drawing board.

[jimmykan]

BSumoba
If I read your post correctly your throat erodes 0.003 per hundred rounds fired and you never change your seating depth for the 1000 shots you fire in your barrels before they are retired?
If that is correct you can have 0.030 variation in your seating depth and still keep your same level of accuracy?
Sound right to you?

And yes, I do not change my seating depth and seem to be doing just fine. IMO, when shooting LR (and this may apply more to F-Class than LR Benchrest), ones ability to read the wind, the environmental conditions and how you perceive those conditions in the scope and adjust for it are usually bigger factors in whether or not you score well or have smaller groups.

It seems that the tangent ogive, hybrid ogive and Lapua Scenar style bullets do not require "chasing" the lands to group well, so the system's grouping ability is maintained as the throat erodes.

bsumoba, do you notice a drop in muzzle velocity as the throat erodes though? Do you increase the powder charge to compensate?