Calculating True 9mm pistol Base-to-Ogive from measurement taken on Hornady Bullet Comparator
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Jim Watson
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I know you want to keep the volume up but I think single stage loading would reduce the variables in testing.
You are using same lot number brass fired the same number of times, right?
And you have a reason for loading to 1324 fps, I assume.
You are using same lot number brass fired the same number of times, right?
And you have a reason for loading to 1324 fps, I assume.
JimGnitecki
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I get that, and may indeed try different powders in the future, but right now I favour the VV 3N38 because:
- I have decades of very favourable experience with VV powders
- The vV3N38 gives the highest muzzle velocities while staying under SAAMI pressure spec (the "Standard" spec even, not just +P), and I am getting 1324 fps with a load that is only halfway up the VV table for this bullet and powder (i.e. about 8% below max powder load in the VV table)
- My load of 8.0 grains pretty much exactly fills the space wihtin the case under the seated bullet, and that of course is an "ideal" we strive for
- My first tests with this load show outstandingly good accuracy (compared to what I can normally do with 70 year old eyes looking through progressive bifocal eyeglasses, off a less than optimal sandbag)
So, I want to carry the initial testing much further.
Jim G
JimGnitecki
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Yes I know that single staging would produce better results, but I don't want to, at least yet, slow down my ammunition making by that much. If I start chasing truly spectacular results, yeah, I might do it at some point just to "see how good I can make it".
I have so far used only brand new Hornady brass (I bought 600 cases, but had to tolerate 2 lot numbers to get that many).
Yes, I want 1300+ fps, because I believe that if you are going to compete, or just practice, you should compete, and practice, with a load and firearm that is representative of an effective stopper in the real world, not a low powered load that games the rules and depends upon using a pistol you could not conveniently carry in the real world. It's a personal standard thing.
My favorite pistol round is the 357 SIG that the Texas Dept of Safety (The Texas State Police) used as its standard pistol round while I worked there in a non-commissioned role for a time. That round uses a .355" 125g round that perfectly mimics the terminal ballistics of a 357 Mag, and the troopers said that when they hit even a drug-crazed felon with it, he went down "like he was hit with a bolt of lightning", even if the round had to go through a vehicle door. I can't for logistic reasons make that my cartridge here in Canada, but I can come close with a reasonably vigorous 9mm 115 grain load.
Like I said, it's a personal standard.
Jim G
Unfortunately it is just a chamfer, that's why they only refer to them as comparators. They are not designed for direct measurement.
It's really the only practical way to make them, the sharp edge of a precision ground surface would either not last, or dig into the softer material of the bullet. Either way, it would not be suitable for the intended purpose.
It's quite visible, you can verify it for yourself by measuring the I.D. out to the edge. The bullet and "headspace" inserts both have it, the headspace style are more pronounced.
I've heard of some people trying to cheat it by compensating off of headspace gauges for the shoulder versions, but you still never know exactly where on that chamfer you'll be getting a direct measurement from one part to the next. It's still an extremely useful tool, as long as you know its limitations and use it with that in mind.
higgite
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That's precisely why I chose an 11/32" bit. It was the largest I had without going over .355".
But I would not consider a hole of any size simply drilled at home by a drill as being precise enough in its diameter and surface quality to be a great substitute for a gage insert that I hope Hornady took greater pains to make correct!
Have you measured your .338" insert. I'd bet it's not precisely .338". The point being, exact diameter doesn't matter. What does matter is that you use the same insert to compare BTO's from cartridge to cartridge.
I know. I have the Hornady aluminum insert set and the Sinclair steel insert set.
Maybe not a chamfer, but most certainly not a sharp 90 degree edge. A Hornady aluminum insert won't hold a sharp edge anyway. I sanded one down to a sharp edge with a sheet of sandpaper on a flat surface once. Like Warpiece said, that won't work. It wouldn't repeat measurements until the sharp edge "broke in" and reached an equilibrium point. The edge then looked very similar to the factory edges on the other inserts. Not what I would call chamfered, but slightly rounded. The Sinclair steel inserts don't have sharp edges either.
JimGnitecki
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Well the last 2 postings are certainly bad news for me. Looks like the best I can do is compare relative values, not determine absolute values.
Sigh . . .
Jim G
Sigh . . .
Jim G
higgite
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I really don’t see why that’s bad news. The BTO measurement won’t give you a consistent jump to the lands anyway. 9mm headspaces on the case mouth and that’s not reflected in BTO measurements, nor is the seating die adjusted for case mouth to ogive distance. The only way that I’m aware of to do that is to trim every case to the exact same length so that a consistent BTO will yield a consistent case mouth to ogive distance. That’s not easy to accomplish in itself. We won’t go into caliper/user accuracy nor trimmer/user repeatability.Well the last 2 postings are certainly bad news for me. Looks like the best I can do is compare relative values, not determine absolute values.
Sigh . . .
Jim G
What you’re trying to do is what a lot of us do, i.e., get as consistent a jump to the lands as we can with what we have to work with. IMHO, you’re just overthinking it for a very small return, if any. But, I can sympathize. BTDT.lordpaxman
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Have your optician grind the dominant eye lens to focus on the front sight and the other lens to focus at distance. Sounds freaky but the brain figures it out. Far easier and faster than doing the bobble head routine, trust me, I know.
Still interested to read how much better these “seated to CBTO” are going to be. I still think it’d be wise to determine why you’re getting the seating variations you are. I just ran a batch of 500 147gr RN blue bullets in mixed range brass, and COL varied maybe +/- .002, most were +/- .001.
JimGnitecki
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I had laser corrective surgery and have replacement made-in-Germany plastic lenses in my eyes because I had cataracts, and those were optimized for distance, for safety in driving, mountain biking, and motorcycling. Then, the eyes, against the odds, changed some more, and I had to add progressive bifocals to handle close-up focusing. The progressive bifocals were set up by the Opthamologist to optimize my ability to focus on the pistol sights, but it's not like when I was 25 years old!
I THINK the variation in COAL is NOT necessarily due to a variation in BTO, but rather much of it is due to the variaition in bullet TIP length. The HAP bullets, which are very high quality, nevertheless vary by up to .007" in base-to-TIP length when I mike them, as do most other high quality bullets apparently. Every bullet manufacturer tells you to measure BTO instead, as THAT is what controls the actual "Jump". It does not matter where the tip of the bullet is when chambered, as the tip never contacts the rifling. It is the intersection of shank and ogive that contacts the rifling.
Other possibiiities for my variation include the toolhead moving a bit when the press platform is UP (possible since the toolhead needs some clearance to slide in and out to change calibers), a variation in the height of the 5 individual shell holders in the shellplate (extremely unlikely), or primer depth inconsistency (I've checked. It's consistent).
Jim G
My Hornady bullet comparator inserts average about .015" smaller than bullet diameter. It keeps the bullets from getting jammed I presume. You might want to redo the math on that .338 if the precise number is used in your process. Good luck.
JimGnitecki
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Howland937
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I get most of what you said regarding your ammo not being loaded down for softer shooting to improve your ability to shoot it well. But all that about the load and firearms representing a real world combination that would be used in real world situations... Please tell me you're not carrying a P210. Please?
I understand the lack of Ransom Rest to truly gauge accuracy. I know a lot of the people here would scoff at my thought process. Honestly, I may not be anywhere near the most accurate load available, but if it's the load I shoot the best, that's all I'm after. But I'm also not a competition shooter.
I'm doubtful @Walkalong will need to eat his hat, but I am curious what flavors go down better.
JimGnitecki
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The Hornady Bullet Comparator arrived today and has already earned its keep.
Using it, and the .338" insert, I measured the base-to-.338"-on-the-ogive for 20 of my produced cartridges, and discovered that that measurement had an Extreme Spread of only .0025", despite the fact that the COAL measured from base-to-tip of bullet had an ES of .010".
It also uncovered for me a problem I did not know I had, where the first few cartridges and last few cartridges in my produciton run varied much more than .010", likely due to there being empty stations on the Dillon XL750 at both start and finish of the run. I will temporarily not allow those start / finish empty stations to occur. But longer term, I will replace the Dillon toolhead and lockrings with the Armanov bolted-in toolhead and the Armanov free floating lockrings, which for reasons explained in my separate Armanov posting should reduce that .0025" variance notably if Armanov claims, and user testimonials, are true.
The Hornady Comparator was a good investment that paid off on its first use.
Jim G
Using it, and the .338" insert, I measured the base-to-.338"-on-the-ogive for 20 of my produced cartridges, and discovered that that measurement had an Extreme Spread of only .0025", despite the fact that the COAL measured from base-to-tip of bullet had an ES of .010".
It also uncovered for me a problem I did not know I had, where the first few cartridges and last few cartridges in my produciton run varied much more than .010", likely due to there being empty stations on the Dillon XL750 at both start and finish of the run. I will temporarily not allow those start / finish empty stations to occur. But longer term, I will replace the Dillon toolhead and lockrings with the Armanov bolted-in toolhead and the Armanov free floating lockrings, which for reasons explained in my separate Armanov posting should reduce that .0025" variance notably if Armanov claims, and user testimonials, are true.
The Hornady Comparator was a good investment that paid off on its first use.
Jim G
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