Interesting unexpected COAL issue due to Dillon 9mm bullet seating die

[JimGnitecki]

I am experiencing an interesting unexpected COAL issue due to the Dillon 9mm bullet seating die bought with my Dillon XL750.

I have been finding that despite all my efforts to consistently apply the same stroke with the same pressure on every stroke of the press handle, I am getting some variation in cartridge overall length, when I measure from base of cartridge to tip of the bullet hollowpoint (I have no tool to measure from base of cartridge to ogive for this 9mm pistol cartridge). In extreme cases, the difference between longest and shortest COAL hits 0.010". Yet, the actual performance of the cartridges i am loading, with 5 shot groups at 25 yards, is as good as 0.81 inches.

I have examined the fit of the 115g Hornady HAP 0.355" 9mm bullet with the reversible seating insert inside the Dillon die, and see the problem: Neither end of the insert can control the bullet via its ogive. Rather, each end seats the bullet via controlling the TIP of the bullet. This is because the only contact between the insert and the bullet occurs right at the tip of the hollowpoint. i.e. the "recess", at either end of the reversible insert, is too wide, so the bullet "bottoms" onto the flat END of the recess. And, I suspect, each hollowpoint bullet tip "crushes" slightly by a differing amount, because the hollowpoint is indeed "hollow" and therefore malleable.

The ogive of the jacketed hollowpoint HAP bullet is basically a straight (i.e. non-curved) truncated cone shaped ogive topped by a hollowpoint. So, a seating insert that can capture and control the ogive could create a very consistent "Overall Length" if measured from the base of the cartridge to the point of ogive contact, and any variation in the TIP of the bullet height would basically be of no consequence since the tip portion does not contact the chamber lead or rifling, so it does not affect pressure produced and therefore will have no impact on bullet speed.

But since the Dillon insert grabs the tip, my theory is that the COAL I get by measuring with my digital caliper, which can only measure from base to tip (not to ogive), varies with the varying OAL length of each bullet tip and by the degree of deformative "crushing" of the tip during seating.

I did a sample analysis of the bullet OAL, and got these results:
Average OAL = 0.5393"
Std Dev = .0019"
Max height = .5445"
Min height = .5375"
Extreme spread = .007"

This explains the up to .010" extreme spread i am getting on the digital caliper. Only .003" is due to my setup and / or inconsistency of pressure. Most of it is due the variation in bullet OAL.

So, I think I need to measure base to ogive, but I don't know where i could get such a gage to sue with my caliper.

A more practical solution seems to be to simply buy a seating die that does capture the ogive versus the tip of the bullet. This solution would not enable me to measure more accurately with my caliper, BUT it would actually make the TRUE COAL (i.e. base to ogive) significantly more consistent, since the deformable and variable height tip of the bullet would no longer be controlling the actual bullet placement within the case.

Dillon does not appear to offer such a seating insert or complete die.

I have ordered a 9mm Redding Competition bullet seating die. That die has a couple of nice features:
- Its shape, at least the one I saw being used in .45 ACP, works properly with a straight cone shaped ogive hollowpoint bullet, capturing the ogive versus the tip
- It has a self-retracting "sleeve" that guides the combination of case and unseated bullet perfectly coaxially aligned into the seating insert
- Its seating height is controlled by a micrometer knob that allows accurate adjustment to a precision of .001"
- It is designed to work in progressive presses as well as single stage presses.

I am hoping this will make the true COAL of my cartridges more consistent.

Jim G

 

[dcloco]

Your investigation has lead you to both items responsible for the variation.

 

[jmorris]

Have you tried both sides of the seating insert or are you using the RN side for the JHP?

 

[JimGnitecki]

Have you tried both sides of the seating insert or are you using the RN side for the JHP?

View attachment 979921

I have tried both ends of the reversible insert. Neither one will grab the ogive. That's why I am resorting to the expensive Redding die. I watched 2 videos of it being explained and installed, and the one video used a 45 acp bullet that looks exactly like my 9mm HAP bullet, justa different caliber, and the Redding insert correctly controls via ogive versus tip.

Jim G

 

[rfwobbly]

>> Unfortunately, Dillon does not make an anvil that's really appropriate for that bullet. XTP, HAP, Precision Delta JHP, and several others have a similar ogive that's simply not served well by the stock Dillon offerings. Luckily the anvil is replaceable. To answer that need, I've made about 20 or so new anvils for myself and other members of my "home forum". If you'd like one please contact me via PM.






>> As far as root cause of OAL variations, I encourage you to also look at case lubrication and mixed brass in your search.
1) Things simply go better with lubrication. People think that because lubrication not absolutely required that it's not needed at all. No one ever said that. Everything is ALWAYS better with lubrication.
2) Mixed brass means wild variations in brass thickness, hardness and finish. That can't help but effect your finished OAL.

Hope this helps.

 

[fxvr5]

I guess the question is, does it matter if there are differences in the distance to the ogive?

 

[JimGnitecki]

>> Unfortunately, Dillon does not make an anvil that's really appropriate for that bullet. XTP, HAP, Precision Delta JHP, and several others have a similar ogive that's simply not served well by the stock Dillon offerings. Luckily the anvil is replaceable. To answer that need, I've made about 20 or so new anvils for myself and other members of my "home forum". If you'd like one please contact me via PM.

View attachment 979938

View attachment 979939


>> As far as root cause of OAL variations, I encourage you to also look at case lubrication and mixed brass in your search.
1) Things simply go better with lubrication. People think that because lubrication not absolutely required that it's not needed at all. No one ever said that. Everything is ALWAYS better with lubrication.
2) Mixed brass means wild variations in brass thickness, hardness and finish. That can't help but effect your finished OAL.

Hope this helps.

Thanks for the offer on the anvil! I PMed you about it. I do use exclusively Hornady 9mm brass, so no mixed brass. I have not lubricated because I have not felt any real friction, but you got me thinking that perhaps lubing the brass might reduce the inevitable "jerking" that sizing the brass on the progressive press creates, which would reduce the already small, but still present, powder spillage when the press indexes.

Jim G

 

[JimGnitecki]

I guess the question is, does it matter if there are differences in the distance to the ogive?

Yes it does matter! First, the ogive shape does not deform unless you apply ridiculous amounts of pressure to the press handle. More importantly, since the bullet ogive is much more consistent than the height of the bullet tip, the actual amount of bullet residing within the case is much more consistent, which means the combustion volume space is much more consistent, which means the combustion pressure produced is more consistent. That means more consistent bullet launch from the case and muzzle velocity. And that means smaller 5-shot groups.

Jim G

 

[mrawesome22-250]

Rough up inside of seating stem, degrease with acetone, fill plug with JB Weld epoxy. Enough that it "humps over" a little. Let it fully cure.

Once cured lay a piece of sandpaper on some glass and sand until flat.

 

[noylj]

Why not stop worrying about something that doesn't matter?
You would be better off concentrating on range time and not picking nits

 

[JimGnitecki]

Rough up inside of seating stem, degrease with acetone, fill plug with JB Weld epoxy. Enough that it "humps over" a little. Let it fully cure.

Once cured lay a piece of sandpaper on some glass and sand until flat.

I don't think this solves the problem. If I understand your posting correctly, you are proposing to "fill in" the recess in the seating insert (or 'anvil") as used above) so that the bottom surface of it that bears on the bullet is flat. This will still continue to seat the bullet by encountering the bullet's TIP versus its ogive.

There are 2 ways I can think of to force the insert to control the bullet height via its ogive versus its tip:

1. Make a machined insert whose recessed head cavity matches and "holsters" the bullet ogive precisely but has a large hole in its upper surface that lets the tip of the bullet go "as far as it wants to" (i..e you don't care about the varying length of the bullet tip)

or

2. Make a machined insert whose recessed head cavity is a hollow cylinder whose inside diameter is larger enough than the inner diameter of the firearm's RIFLING (a spec you can get off a SAAMI diagram) to prevent the bullet from being "forced" into the seating insert while seating the bullet

1. is much harder to make than 2., has no real advantage over 2., and has the disadvantage of requiring regular cleaning if you use unjacketed bullets.

2. is much easier to make, is as accurate or more accurate (since you only need to keep the end of the insert clean to get an exactly consistent bullet seating), and has the distinct advantage of enabling you to measure the actual base to ogive dimension if you make an identical 2nd insert to use as a bullet comparator AND measurement tool to tell you how far off the rifling you are actually seating.

When using 2. as a comparator, you would simply insert each bullet you want to measure into the 2nd insert (not mounted in the press), and measure the OAL of the 2nd insert plus the amount of bullet that is protruding from the insert. If your bullets are consistent in dimensioning, all such measurements should produce the same number.

When using 2. to tell you how far off the rifling you are actually seating, you would measure the distance form the base of a loaded cartridge to the bottom of the insert. Compare that measurement to the measurement you get from a cartridge that you have determined (via plunk and rotate test or other means) just touches the rifling when inserted into your chamber.

Just an idea . . .

Jim G

 

[fxvr5]

Yes it does matter! First, the ogive shape does not deform unless you apply ridiculous amounts of pressure to the press handle. More importantly, since the bullet ogive is much more consistent than the height of the bullet tip, the actual amount of bullet residing within the case is much more consistent, which means the combustion volume space is much more consistent, which means the combustion pressure produced is more consistent. That means more consistent bullet launch from the case and muzzle velocity. And that means smaller 5-shot groups.

Jim G

Do you have evidence this will make a difference in 9mm, or did you make that up?


This article found no difference in accuracy using Dillon and Redding seating dies in 9mm (this article looked at the concept of crooked bullets).
https://americanhandgunner.com/gear/crooked-seated-bullets-and-accuracy/


This article found no correlation between consistent velocity and accuracy in a 9mm.
https://americanhandgunner.com/handguns/exclusive-consistent-velocity-accuracy/


Oh, and 5-shot groups are of little value. See this article:
https://www.ssusa.org/articles/2019/9/25/accuracy-testing-shortcomings-of-the-five-shot-group/

 

[JimGnitecki]

Why not stop worrying about something that doesn't matter?
You would be better off concentrating on range time and not picking nits

Because it's TIME to be nitpicky:



The above target was shot off a sandbag at 25 yards, looking through 70 year old eyes with progressive bifocals.

Since the height of the bullet within the case affects chamber pressure, and can in fact create overpressure if the bullet is too deep in the case, OR contacts the rifling when chambered, this is NOT nitpicking. It is BASIC SAFETY.

Yes, you could load conservatively enough that the variations in COAL and pressures and muzzle velocity aren't large enough to be dangerous or wildly inaccurate, but then you'll never experience really tight groups, and the satisfaction of knowing that "you did it".

Jim G

 

[Walkalong]

Extreme spread = .007"

Not real bad actually, although you should be able to get it under .005 with a better seating stem to bullet fit.

I doubt the slight differences in bullet ogive to the lands is making a difference you can see on paper, a different bullet or powder might be the answer.

 

[JimGnitecki]

Do you have evidence this will make a difference in 9mm, or did you make that up?


This article found no difference in accuracy using Dillon and Redding seating dies in 9mm (this article looked at the concept of crooked bullets).
https://americanhandgunner.com/gear/crooked-seated-bullets-and-accuracy/


This article found no correlation between consistent velocity and accuracy in a 9mm.
https://americanhandgunner.com/handguns/exclusive-consistent-velocity-accuracy/


Oh, and 5-shot groups are of little value. See this article:
https://www.ssusa.org/articles/2019/9/25/accuracy-testing-shortcomings-of-the-five-shot-group/

Your item 1: The article was, as you said, looking for concentricity improvements. That's entirely different. COAL is PROVEN by decades of testing by numerous shooters and ammunition companies to have profound effects.

Your item 2: With 9mm, being shot at only 25 yards or less, the differences in group size might well be modest. But try at 50 yards or 75 yards, and yes, some people do shoot 9mm handguns at those distances, because their combinations of firearm, ammunition, and technique CAN allow that.

Your item 3: That page won't load for me, but i assume it is likely Brad MIller's article from Shooting Times magazine. Brad is a very knowledgeable shooter, both theoretically (he has a PhD) and practically - I read his articles in Shooting Times every time, especially his recent series on high velocity SAAMI, SAAMI +P, and 9 Major pistol loads. He is statistically correct, BUT no psitol or ammo tester I know is willing to shoot 500 rounds or more of every factory or handload he wants to test. The accepted and easily comparable testing that 99% of testers do is based on shooting a few multiples of 5-shot groups for each load, picking the most promising, and then working hard on the DETAILS to see how good that load can be made in that firearm. For me, that works well.

Jim G

 

[JimGnitecki]

Not real bad actually, although you should be able to get it under .005 with a better seating stem to bullet fit.

I doubt the slight differences in bullet ogive to the lands is making a difference you can see on paper, a different bullet or powder might be the answer.

It's not optimizing the "jump" that I am concerned about right now. That will come later. Right now my concern is making sure I am not short enough on COAL to raise the peak pressure. 8.0 grains of VV 3N38, while only midway through the loading range that VV recommends for this bullet (7.2g minium and 8.7g maximum) is right on the verge of becoming a compressed load (That's with my current 1.142" COAL target and my measured 0.76 load density which differs from the default that both QL and GRT use). Having a full case (but with a safe load) is of course ideal for a uniform and predictable burn, but Vihtavuori, QuickLOAD, and Gordon's Reloading Tool all point out how the peak pressure is raised if some of your cartridges come out of the pres at a shorter COAL than intended. That's why the extreme spread of 0.010" bothers me. because that spread is based on TIP measurements versus ogive measurements, I don't know what my REAL base to ogive measurement is.

Issues like this are why I always load to far enough below maximum recommended charge to ensure that an undetected variance does not accidentally create an over pressure. In decades of reloading on Dillon progressives, I had not previously run into this issue. But then I had never before loaded a coned versus rounded JHP bullet with exactly the "right" (wrong) dimensions to create this issue with the Dillon seating insert.

Jim G

 

[fxvr5]

Your item 1: The article was, as you said, looking for concentricity improvements. That's entirely different. COAL is PROVEN by decades of testing by numerous shooters and ammunition companies to have profound effects.

Your item 2: With 9mm, being shot at only 25 yards or less, the differences in group size might well be modest. But try at 50 yards or 75 yards, and yes, some people do shoot 9mm handguns at those distances, because their combinations of firearm, ammunition, and technique CAN allow that.

Your item 3: That page won't load for me, but i assume it is likely Brad MIller's article from Shooting Times magazine. Brad is a very knowledgeable shooter, both theoretically (he has a PhD) and practically - I read his articles in Shooting Times every time, especially his recent series on high velocity SAAMI, SAAMI +P, and 9 Major pistol loads. He is statistically correct, BUT no psitol or ammo tester I know is willing to shoot 500 rounds or more of every factory or handload he wants to test. The accepted and easily comparable testing that 99% of testers do is based on shooting a few multiples of 5-shot groups for each load, picking the most promising, and then working hard on the DETAILS to see how good that load can be made in that firearm. For me, that works well.

Jim G

By all means, please share the data that minor differences in OAL in 9mm affects group size. I'd love to read it. Thanks.

That 3rd link works for me. Try it again. That article is not from Shooting Times. It's in SSUSA.

 

[JimGnitecki]

By all means, please share the data that minor differences in OAL in 9mm affects group size. I'd love to read it. Thanks.

That 3rd link works for me. Try it again. That article is not from Shooting Times. It's in SSUSA.

I'm not going to do a Google search to find the obvious! Any change in COAL affects either peak pressure or jump, and both of those affect velocity and accuracy, so a variation in COAL IS significant by definition. See what Sinclair, Vihtavuori, Hornady, and many others say about it.

I got the link to the SSUSA to work. But, it is indeed Brad mIller's article first published in Shooting Times (where I read it), and I already said that I agree with Brad Miller's article but no one else will even try to do 500 round grouping tests, so I do the same practical 5-shot grouping tests as everyone else does. I'm not trying to imply that all my groups are wonderful either. The 5-shot protocol is merely my practical way of separting the good loads which should be investigated further from the bad loads which should not.

Jim G

 

[fxvr5]

Because it's TIME to be nitpicky:

View attachment 979980

The above target was shot off a sandbag at 25 yards, looking through 70 year old eyes with progressive bifocals.
Jim G

I can see why you like the results from this load. That's a great group.

I'm curious, at what group size do you consider it to be so big that it does not warrant further exploration?

And this can go out to other forum members, too. Do y'all have a clear criteria for what group size is too big to pursue further. Is there a size criteria for good versus bad loads? I'm not sure I have a clear criteria for my own data. Thanks.

 

[JimGnitecki]

I can see why you like the results from this load. That's a great group.

I'm curious, at what group size do you consider it to be so big that it does not warrant further exploration?

And this can go out to other forum members, too. Do y'all have a clear criteria for what group size is too big to pursue further. Is there a size criteria for good versus bad loads? I'm not sure I have a clear criteria for my own data. Thanks.

The size of a group that looks promising depends on the known accuracy or inaccuracy of a given firearm.

For a normal "combat accuracy" pistol, you might have to be satisfied with a 2" or even 3" group at 25 yards.

But with an insanely accurate pistol like the SIG P210A Target model I have, multiple reputable reviewers have achieved 5-shot groups at 25 yards, using a Ransom Rest or good sandbag expertise, in the 2/3 of an inch category.

My personal limitation is my eyesight. I am 70 years of age, had cataract laser surgery 5 years ago that replaced my natural lens with plastic ones, and I still need progressive bifocal eyeglasses for close up focusing (like a set of pistol sights!). So for me, now, I am sort of thrilled with the group I posted, but irritated by the flyer caused by my eyesight or other as-yet unidentified shortcoming!

For this load, I tried 7.2 gr (the minimum recommended by Vihtavouri for this loading, 7.4 gr, 7.6 gr, 7.8 gr, 8.0gr, and 8.1 gr. I looked at the absolute sizes of each group for each powder weight , but also looked for patterns in those group sizes. I noticed that
7.2 was awful (for THIS pistol) at about 3", and the muzzle velcoity was 100 fps lower than with 7.4 grains! Not a happy configuration.
7.4 was better
7.6 not as good as 7.4
7.8 was not good
8.0 was the best
8.1 was not only not as good as 8.0, but also had much worse SD and ES and only about the same muzzle velocity as 8.0, indicating that it was not a "happy" configuration. 8.1 grains was also above the midpoint of the 7.2 to 8.7 grain range recommended by VV, and I wanted to stay close to the mid range if I could get decent accuracy there, as the 1324 fps at 8.0 grains was good enough for me, and I had plenty of safe pressure headroom compared to the 8.7 grain max in the table, which I assume came close to SAAMI's 35,000 psi limit. I think the 8.0 logically is at about 29,000 psi, based on rules of thumb from Vihtavouri on how pressure reduces much faster than powder reduced.

The standard deviation and Extreme spread were not impressive for any of the powder loads EXCEPT the 8.0 load. That load has an SD of 10 and an ES of 36. The next best SD (15) and ES (49) were for 7.4 grains.

All the above showed me that there were 2 good nodes to pursue, around 7.4 and 8.0, but 8.0 was way better and 7.4 was too slow a velocity for me., so I have focused on 8.0 grain load development.

There are I'm sure much more scientific ways to "cull the possibilities", but this works for me, and I am enjoying the process and am encouraged by the results so far.

Jim G

 

[fxvr5]

I am sort of thrilled with the group I posted, but irritated by the flyer caused by my eyesight or other as-yet unidentified shortcoming!

For this load, I tried 7.2 gr (the minimum recommended by Vihtavouri for this loading, 7.4 gr, 7.6 gr, 7.8 gr, 8.0gr, and 8.1 gr. I looked at the absolute sizes of each group for each powder weight , but also looked for patterns in those group sizes.

The standard deviation and Extreme spread were not impressive for any of the powder loads EXCEPT the 8.0 load. That load has an SD of 10 and an ES of 36. The next best SD (15) and ES (49) were for 7.4 grains.

How many rounds do you load/shoot for each powder charge tested? I might have missed that in my read-through of your method.

With respect to the target you posted, if you shot additional 5-shot groups with that same 8.0 grain charge weight, what were the sizes of those groups? Thanks.

 

[JimGnitecki]

How many rounds do you load/shoot for each powder charge tested? I might have missed that in my read-through of your method.

With respect to the target you posted, if you shot additional 5-shot groups with that same 8.0 grain charge weight, what were the sizes of those groups? Thanks.

Depends on how the first shots with each powder load perform. If the velocity is too low versus my target velocity, or the velocity is too low or too high compared to the loads just below or just above in terms of powder content, or there are other troubling manifestations, e.g. sharper recoil then expected, or primers that look different than I expect to see, or the extreme spread evident in even just a few shots is too high to accept, I'll stop shooting those loads and disassemble them later back at home. I won't risk me, or the firearm, or waste the time and components, by shooting any more of them.

I should mention that I do NOT just blindly try "a bunch" of potential loadings. I research a LOT before I actually decide on a preliminary loading via the loading press, followed by range testing. I do enough research that I will not be "surprised" by the results at the range (although this particular load development has gone surprisingly well with its initial results).

If I am testing a broad range of loads, say 5 or 6 different loadings, the first range session will only include 10 to maybe 15 at most of each different load, as I don't want to make a bunch of cartridges that I may have to disassemble via inertia hammer if they prove to be useless to test further. It takes me 3 good hits with the hammer to free up the bullet in a cartridge, and that gets old after doing just even a few cartridges! If I choose a day that I am feeling good, take my time setting up and firing each shot, I can usually know within that 10 to 15 rounds, or sometimes after just a very few rounds, if the load is "promising" or " a loser not worth spending time or money on".

That first broad range session gives me sufficient clues via the attributes and trends noted above and in earlier posts in this thread, to know which loads I should then focus on more closely.

For the next range session, I often load 25 cartridges for each "contender" load, as by then I know none of them has troubling attributes, and I want to see how much their 5-shot group size varies with more groups fired.

With this particular program, I knew from the first session that the best potential load lay either at 8.0 grains or somewhere close to that. So, I loaded 40 rounds each of 7.9 and 8.1 loads. Both were better than the 7.2 to 7.8 loads, but not as good as the 8.0 load. And the 8.1 grain load, as I mentioned earlier, stalled out at a velocity no better than the 8.0 which means it is not a happy load, and both the 7.9 and 8.1 loads had worse SD and ES than the 8.0 load.

So yesterday, I loaded 50 of the 8.0 grain load to do some extended testing of it. It's rainining too much right now to allow a rnage session, but first chance I get, I'll be out at the range, and I'll be concentrating on shooting each shot as well as I can, to see how well the 8.0 load can shoot when I really concentrate.

None of the few 8.0 groups from the first session were quite as good as the one I posted, but they were not dramatically different.

I should mention that one of the things I do when testing is I fire 5-shots of one load, and then 5 shots of a different load, and so on, so that the last load tested is not penalized by my - or just even my eyes - getting tired, or by other shooters coming or going around me or affecting my firing pace via firing line ceasefires. So I often will run through the first 5 shots for each laod, and then do the next 5 shots for each load, and so on. This makes it a bit of a mental gymnastics and recordkeeping hassle with the chronographing, and with matching the right target to each chronograph string from the Labradar, but it does help minimize the otherwise unavoidable distortions of performance due to the factors I mentioned.

It's also important to RECORD the fact whenever you know YOU, not the load, screwed up. I do this by marking the actual atrget right away if I am alone at the range, or I record a note on my daily calendar that on Target "x" I was responsible for the flyer. This ensures that i am measuring the performance of the load, in my pistol, and not MY performance.

Right now, I need to get accurate measurements of the base to ogive distance. That requires that I wait until I get the Redding Competition Seating Die, or the homemade machined insert for the Dillon die that another reloader has offered to send me, that will properly seat via the bullet via its ogive, not the tip. I also want to get the Hornady Lock and Load Bullet comparator + 9mm cartridge holder, so that I can measure my actual base to ogive measurement, and gage its consistency or lack thereof. THEN I can move forward with more refinements.

Jim G

 

[lordpaxman]

But since the Dillon insert grabs the tip, my theory is that the COAL I get by measuring with my digital caliper, which can only measure from base to tip (not to ogive), varies with the varying OAL length of each bullet tip and by the degree of deformative "crushing" of the tip during seating.

I use the Dillon dies as well, and use Hornady one shot case lube just to smooth out the whole process. My question to you and the forum is this:
If the seating die hits the tip of the hollow point, and deforms it, but the COL is the same (the press doesn’t flex), why doesn’t this set the COL as the same. Sure, if you pulled the bullet, the bullet OAL would be less (it’s deformed) but that would just mean you reduced the seating depth.
Also, I laud your efforts, even though I’d be quite happy with your current groups. But unless the ogive to tip measurement doesn’t change, might you be right back in to the variations you’re currently getting if you’re seating on the ogive? I know XTPs are supposed to be consistent, but I don’t know by how much.
Finally, would love to see how far you take this! My last 3K run was with 147 Blue Bullets RN so I do get a bit of deformation on the tip, and bit of spread +/- .005 on seating depth but it’s a long bullet and mixed HS cases so I know I have different wall thicknesses and neck tension. They still group well in the A zone, if only I could hit it faster.... Good luck.

 

[fxvr5]

And the 8.1 grain load, as I mentioned earlier, stalled out at a velocity no better than the 8.0 which means it is not a happy load, and both the 7.9 and 8.1 loads had worse SD and ES than the 8.0 load.

What does 'not a happy load' mean? Are you saying that you've reached the max speed this powder will produce because it showed no increase from 8.0 to 8.1 grains?

My personal limitation is my eyesight. I am 70 years of age, had cataract laser surgery 5 years ago that replaced my natural lens with plastic ones, and I still need progressive bifocal eyeglasses for close up focusing (like a set of pistol sights!). So for me, now, I am sort of thrilled with the group I posted, but irritated by the flyer caused by my eyesight or other as-yet unidentified shortcoming!

Have you considered that the reason for the flyer might be that it is the actual accuracy of that load, and not because you did something wrong?

 

[JimGnitecki]

I use the Dillon dies as well, and use Hornady one shot case lube just to smooth out the whole process. My question to you and the forum is this:
If the seating die hits the tip of the hollow point, and deforms it, but the COL is the same (the press doesn’t flex), why doesn’t this set the COL as the same. Sure, if you pulled the bullet, the bullet OAL would be less (it’s deformed) but that would just mean you reduced the seating depth.
Also, I laud your efforts, even though I’d be quite happy with your current groups. But unless the ogive to tip measurement doesn’t change, might you be right back in to the variations you’re currently getting if you’re seating on the ogive? I know XTPs are supposed to be consistent, but I don’t know by how much.
Finally, would love to see how far you take this! My last 3K run was with 147 Blue Bullets RN so I do get a bit of deformation on the tip, and bit of spread +/- .005 on seating depth but it’s a long bullet and mixed HS cases so I know I have different wall thicknesses and neck tension. They still group well in the A zone, if only I could hit it faster.... Good luck.

Yes, when the tips get deformed, you can have consistent overall base-to-tip measurements, but that measurement is not what you should be seeking, because as you have already agreed with me, the raw bullets themselves typically vary by up to .010" in THEIR OAL. IF they are all seating with consistent TIP measurement, then your base-to-OGIVE measurements will be varying. That means the length of bullet that is inside the case is varying, which means the combustion chamber volume for the powder is varying, which means peak pressure is varying, which is not good.

The only way to get consistent combustion chamber size is to make sure that cartridge base-to-ogive measurement is consistent. Since ogive shape on a bullet does NOT vary (unlike the tip length!), that will give you consistent combustion chamber size.

The HAP bullets I am using are exactly like XTPs (per Hornady website) but lack the cuts in the hollowpoint head, which the XTP needs to promote expansion on impact. The HAP does not need those cuts since it is intended for Action Pistol competition, where the cuts create a jamming potential (even if rare). So I would think that the variance in HAP and XTP bullet length is the same. My actual ES on HAP bullet lengths is 0.010". So, even with high quality bullets, tip length varies by as much as 0.010".

In a "typical" "combat grade" 2 or 3 inch group size pistol, at 15 or 25 yards, the variation in accuracy and velocity might not be very apparent. But on a SIG P210, where actual published test results show 5-shot groups as small as 2/3 of an inch, yes, the variation in combustion space volume, and the variation in ogive to rifling distance (the "jump") can make a noticeable difference. And especially so at 50 yards or more.

Jim G