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

[lordpaxman]

@JimGnitecki , I understand everything you posted above in #25, but what I was asking was related to your first post:

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).

I read that as you were measuring COL and finding a .010” difference. I view the seating step like an arbor press - it has a fixed distance between the base of the cartridge and where the seating step contacts the bullet, in your case the tip. So if that distance is fixed, is the press flexing, or something else moving during the seating step or something perhaps is “springing back” inconsistently after the seating step?
I get the fact that if the tip deforms the seating depth is less, but the COL should be consistent. ?yes? ?no?

 

[noylj]

Let's deal with history.
Once again, the great COL paranoia began with an article in the 90s. LEOs had reported a few Kabooms at qualification testing.
Investigation showed that these folks would chamber a round at the start of shift, unload at end of shift, and place round back in magazine. This would go on for months if not a year. Some of these rounds had severely shortened COL from all the feed ramp battering.
Thus, one of the ammunition companies reported the danger of repeatedly chambering the same round by testing std ammo and getting about 33ksi and seating bullet 1/4" (0.25") deeper and getting just over 60ksi.
Now, if 0.250" raises pressure ~30ksi, just how much will pressure go up seating 0.007" deeper?
Now, if you interpolate pressure, you will over estimate pressure as pressure goes up in an inverse exponential curve. So, knowing this will grossly over estimate pressure, let's do a quick calculation.
0.25" decrease in COL raises pressure by ~30000 psi, so every mil reduction in COL will increase pressure by 240 psi. So, a 0.007 shorter COL will, at a huge over estimation of pressure, increase pressure by 1680 psi. This is insignificant (not even into +P territory which is 35000 to 38500 psi) and, as stated, is a HUGE over estimation.
It just doesn't matter.
Again, get a Lee seating die, send Lee a few bullets, and ask for a seating stem that only contacts the bullet low on the ogive (this is what I order from die manufacturers).
(As an aside, how do you guarantee seating stem being coaxial with case and press using adhesive and a round with no guarantee of being perfectly seated?)
(As an additional aside, since commercial bullets are made in multiple dies, the ogives may not be any more consistent than the meplat.)
Install the seating die in a cheap single-stage press and turn seating stem all the way up.
On your normal press, seat bullet long.
Move round to secondary press and incrementally turn seating stem in until you get your target COL. Turn seating stem up several turns and keep repeating so all rounds have the same COL.

 

[JimGnitecki]

@JimGnitecki , I understand everything you posted above in #25, but what I was asking was related to your first post:

I read that as you were measuring COL and finding a .010” difference. I view the seating step like an arbor press - it has a fixed distance between the base of the cartridge and where the seating step contacts the bullet, in your case the tip. So if that distance is fixed, is the press flexing, or something else moving during the seating step or something perhaps is “springing back” inconsistently after the seating step?
I get the fact that if the tip deforms the seating depth is less, but the COL should be consistent. ?yes? ?no?

I don't have any answers yet. I have the Redding Compeition seating die on order, and I am trying to find the Hornady Bullet Comparator in stock here in Canada. It is out of stock everywhere I have checked so far. I need that tool to know where I am REALLY on consistency or inconsistency of the seating depth, as measured by base of cartridge to OGIVE, not tip of bullet.

And yes, the bullet tips must be springing back a bit after seating, which I suppose is possible because they are not lead, but rather what Hornady calls "Gilding Metal". I'm not a metalurgist though . . .

Or, maybe there is a bit of vertical play in the head versus the Dillon frame. If so, it is possible, when not all 4 of the stations that experience "pressure" during cycling, are occupied, each exerting upward pressure, that the head might actually "tilt" just a tiny bit. I know that this IS an issue on at least some Dillon setups, because there is a company that sells "clamps" that secure the head to the frame positively.

The investigation continues.

Jim G

 

[Walkalong]

And yes, the bullet tips must be springing back a bit after seating,

The only time I have had this happen in pistol loads is with compressed loads. You get to a point that screwing the seater down more doesn't reduce OAL any more.

 

[JimGnitecki]

The only time I have had this happen in pistol loads is with compressed loads. You get to a point that screwing the seater down more doesn't reduce OAL any more.

I can see that! Right now, I believe I am NOT compressing the load, as both QuickLoad and GRT say I have .148" of bullet seating depth, which QL says is not enough to compress the load, and GRT says it is compressed by 1%. Now if the true seating depth is varying, then maybe it IS compressing, and compressing enough to cause a springback?

Jim G

 

[fxvr5]

I agree that 0.007" difference in OAL is insignificant.

Below is a plot published in older versions of Ramshot's loading manual of pressure changes with changes in OAL using a relatively fast powder (Zip) in a 9mm. A change in OAL of 0.010" produces about 726 psi change. Can't say if 3N38 would act the same.

Also, I'm not sure what the OP's SD and ES numbers are, but they will vary from one string to another up to a factor of 2X even when using the same ammo, as shown in the data at this link:
(https://americanhandgunner.com/handguns/exclusive-consistent-velocity-accuracy/). And group size will vary even more.

On the other hand, what else do we have to do during Covid-19 lockdown?

 

[JimGnitecki]

I agree that 0.007" difference in OAL is insignificant.

Below is a plot published in older versions of Ramshot's loading manual of pressure changes with changes in OAL using a relatively fast powder (Zip) in a 9mm. A change in OAL of 0.010" produces about 726 psi change. Can't say if 3N38 would act the same.

Also, I'm not sure what the OP's SD and ES numbers are, but they will vary from one string to another up to a factor of 2X even when using the same ammo, as shown in the data at this link:
(https://americanhandgunner.com/handguns/exclusive-consistent-velocity-accuracy/). And group size will vary even more.

On the other hand, what else do we have to do during Covid-19 lockdown?

View attachment 980205

This info on pressure changes with changing COAL is actually reassuring to me! Thank-you.

Jim G

 

[fxvr5]

This info on pressure changes with changing COAL is actually reassuring to me! Thank-you.

A couple years back I loaded some 9mm ammo based on the Ramshot plot, with a 115 grain bullet and 4.5 gr of Zip.

The change in velocity going from an OAL of 1.155" down to 1.082" resulted in an increase of a whopping 40 fps. That was about the average ES of the ammo.

Looking at some of my other old data in a 9mm with Silhouette and a 115 grain bullet, the average change in velocity after a 0.015" difference in OAL resulted in a change between 12-16 fps. This is far less than the ES for a given load.

This suggests that a difference in 0.007" OAL will have little if any effect on velocity - an insignificant amount.

 

[JimGnitecki]

A couple years back I loaded some 9mm ammo based on the Ramshot plot, with a 115 grain bullet and 4.5 gr of Zip.

The change in velocity going from an OAL of 1.155" down to 1.082" resulted in an increase of a whopping 40 fps. That was about the average ES of the ammo.

Looking at some of my other old data in a 9mm with Silhouette and a 115 grain bullet, the average change in velocity after a 0.015" difference in OAL resulted in a change between 12-16 fps. This is far less than the ES for a given load.

This suggests that a difference in 0.007" OAL will have little if any effect on velocity - an insignificant amount.

Again, I am very glad to hear that! I am very cautious about pressure.

Jim G

 

[JimGnitecki]

I got a reply from Dillon suggesting one solution:

"
Hi Jim,

No other seating stem is available. What may help is to take an extra stem fill it with epoxy, place a well lube bullet in the epoxy. Let it harden, remove the bullet, and you will have a custom stem for that bullet nose shape. I have done this for several “odd” shape bullets.

Ron"

I see issues with this solution.

First, how do you ensure that the bullet you put into the epoxy that is in the vertically held insert, is itself absolutely vertical?

Then, how do you secure it to be vertical while the epoxy is hardening?

Then, we know that the length of the bullet tips is NOT consistent. But the suggested solution STILL sets the seated height based on the tip!

And finally, you still have no way of knowing the distance from the cartridge base to the ogive, since you cannot control to what depth the bullet you used to make the "mold" will end up in the epoxy!

I think the combination of the Hornady Bullet Comparator with the right size insert in it, and the micrometer adjustable Redding Competition Seating die, is a greatly superior solution. What do you guys think?


Jim G

 

[JimGnitecki]

This article by Berger BUllets does a greta job of explaining the importance of Case-to-ogive versus the UNimportance of COAL (other than to make sure the rounds will chamber):

https://bergerbullets.com/wp-content/uploads/2013/03/COAL.pdf

Jim G

 

[fxvr5]

Honestly, given my results on velocity (and accuracy) and the accuracy results from the linked articles, I doubt you're going to see a difference after all your time, effort and money spent. 0.007" difference in OAL amounts to virtually nothing in differences of pressure and velocity. It's hard to imagine how that small difference will show up on your target.

The only way to really test it would be to put the gun in a Ransom Rest. I would never trust results shot off sandbags. I say this because I test guns in a Ransom Rest, and I see significant differences in group size even when shooting the exact same ammo. If you're not going to test the gun in a Ransom Rest, there will always be doubt about what contributes to group size; the ammo, the gun, the shooter. You want to eliminate the contributions of the shooter. And if you did test it, you'd want 2 types of ammo. One batch of the super-duper consistent OAL, and one batch with using just the Dillon seater.

One thing to watch for is misattribution of group size. A shooter has to account for fliers, by knowing that something went wrong when that round was fired so the blame goes to the shooter. If nothing did go wrong when the round was fired, and they get fliers, then those fliers have to be included in the group size measurement. No exceptions. By the way, I get fliers when using the Ransom Rest. They happen even under the best of conditions. And they reflect the accuracy of the ammo in that gun. It might be a gun issue or it might be a ammo issue, but those are the results and you can't ignore that fact.

Your chosen bullet, the 115 HAP is very good and one of the most accurate 9mm bullets in that weight. Bullseye shooters use it and recommend it (along with the XTP), and that's a strong endorsement. That's been proven. 3N38 is wonderful gunpowder, another proven product. I've shot amazing groups with it in my 38 Super Kart barrel with a variety of bullets. The Sig P210 is an amazingly accurate gun. But that doesn't mean it shoots every load equally, as you've already discovered.

I don't mean to sound negative and I do encourage people to test their ammo to find a load their gun likes. There is satisfaction in load development. I know, I do a lot of it. This post is meant more as a reality check. There are inherent limitations in what guns will do - some love a given load but another might hate it - and limitations in our methods and interpretation of the data. Charge forward but keep these in mind.

 

[lordpaxman]

This article by Berger BUllets does a greta job of explaining the importance of Case-to-ogive versus the UNimportance of COAL (other than to make sure the rounds will chamber):

https://bergerbullets.com/wp-content/uploads/2013/03/COAL.pdf

Jim G

It’s a great article and I recommend the Berger handbook for anyone venturing into PR. I’ve not seen any comparable article dealing with PP (Precision Pistol). I’ve tweaked a few of the reloading variables in 9/40/45 but wasn’t able to reach any conclusions in ones that affect precision the most. I am still interested and look forward to your foray into it.

This suggests that a difference in 0.007" OAL will have little if any effect on velocity - an insignificant amount.

That may be true but it could have a significant affect on peak pressure depending on what powder, bullet, and what part of the curve you’re dealing with. In the OP’s case, I’d agree probably not an issue, but I wouldn’t make it a generalized statement. It’s a good reason to avoid max loads with an unforgiving powder and poor control on COL.

 

[Walkalong]

I'll agree with @fxvr5 that .007 isn't enough to lay awake at night over. Sure, we can reduce that, and so why not, but it isn't going to make or break our accuracy results on paper. I doubt we could even shoot the difference. I doubt the ransom rest could shoot the difference.

 

[jmorris]

Dillon makes a number of different seating inserts, might be worth trying them, if you don’t have the ability to machine one. I’d try a 32 S&W insert first for the narrow Hornady bullets.

Just grabbing a few HAP bullets from the box and measuring them, once again OAL might not be the best way to measure them, as they are more consistent from a datum on the ogive to base than OAL.





I might start by pulling a few I measured before seating and measure them after and see how much seating alone changes the length of the bullet. I’d put a foam ear plug in the puller to not damage the bullet when pulling it.

I would also measure finished rounds using something like the last two above and see how they differ.

After all the tip of a bullet isn’t going to touch anything until it hits the target, consistency to the lands would be much more important.

If you don’t already have a chronograph might be worth investing in one and seeing velocity numbers, using samples that are “off” and “perfect” to you. Would let you know if there is anything down the rabbit hole you are heading down, much less subjectively than judging best 4 out of 5 hand shot group size at 25 yards.

 

[JimGnitecki]

Honestly, given my results on velocity (and accuracy) and the accuracy results from the linked articles, I doubt you're going to see a difference after all your time, effort and money spent. 0.007" difference in OAL amounts to virtually nothing in differences of pressure and velocity. It's hard to imagine how that small difference will show up on your target.

The only way to really test it would be to put the gun in a Ransom Rest. I would never trust results shot off sandbags. I say this because I test guns in a Ransom Rest, and I see significant differences in group size even when shooting the exact same ammo. If you're not going to test the gun in a Ransom Rest, there will always be doubt about what contributes to group size; the ammo, the gun, the shooter. You want to eliminate the contributions of the shooter. And if you did test it, you'd want 2 types of ammo. One batch of the super-duper consistent OAL, and one batch with using just the Dillon seater.

One thing to watch for is misattribution of group size. A shooter has to account for fliers, by knowing that something went wrong when that round was fired so the blame goes to the shooter. If nothing did go wrong when the round was fired, and they get fliers, then those fliers have to be included in the group size measurement. No exceptions. By the way, I get fliers when using the Ransom Rest. They happen even under the best of conditions. And they reflect the accuracy of the ammo in that gun. It might be a gun issue or it might be a ammo issue, but those are the results and you can't ignore that fact.

Your chosen bullet, the 115 HAP is very good and one of the most accurate 9mm bullets in that weight. Bullseye shooters use it and recommend it (along with the XTP), and that's a strong endorsement. That's been proven. 3N38 is wonderful gunpowder, another proven product. I've shot amazing groups with it in my 38 Super Kart barrel with a variety of bullets. The Sig P210 is an amazingly accurate gun. But that doesn't mean it shoots every load equally, as you've already discovered.

I don't mean to sound negative and I do encourage people to test their ammo to find a load their gun likes. There is satisfaction in load development. I know, I do a lot of it. This post is meant more as a reality check. There are inherent limitations in what guns will do - some love a given load but another might hate it - and limitations in our methods and interpretation of the data. Charge forward but keep these in mind.

Yes, I hear you. I am aware of the limitations, but I enjoy the process anyway!

Jim G

 

[JimGnitecki]

Dillon makes a number of different seating inserts, might be worth trying them, if you don’t have the ability to machine one. I’d try a 32 S&W insert first for the narrow Hornady bullets.

Just grabbing a few HAP bullets from the box and measuring them, once again OAL might not be the best way to measure them, as they are more consistent from a datum on the ogive to base than OAL.

View attachment 980297 View attachment 980298

View attachment 980299 View attachment 980300

I might start by pulling a few I measured before seating and measure them after and see how much seating alone changes the length of the bullet. I’d put a foam ear plug in the puller to not damage the bullet when pulling it.

I would also measure finished rounds using something like the last two above and see how they differ.

After all the tip of a bullet isn’t going to touch anything until it hits the target, consistency to the lands would be much more important.

If you don’t already have a chronograph might be worth investing in one and seeing velocity numbers, using samples that are “off” and “perfect” to you. Would let you know if there is anything down the rabbit hole you are heading down, much less subjectively than judging best 4 out of 5 hand shot group size at 25 yards.

THIS was a GREAT and very helpful response! The photos illustrate well why base-to-ogive is what I should be measuring. You might have missed in my postings that I do have a Labradar and so can capture the velocity of each round fired, and I also get the standard deviaiton and extreme spread numbers that way too.

Your use of that "hex shaped" base-to-ogive gage (BTO) also illustrates the point that the Berger article makes about how relatlvely less important the exact dimension of the gage is (You used a .300 gage opening for your photos, but you can actualy use any gage size smaller than the caliber of the bullet you are measuring). When my Hornady Bullet comparaot rkit arrives, I'll be using the .338 gage insert since the next size up insert after that is NOT for "9mm" but rather for the next RIFLE caliber up (since Hornady designed the gage for RIFLE users, not pistol users). It doesn't matter, as long as I use the same exact insert each time, to check the consistency.

Jim G

 

[fxvr5]

.

 

[fxvr5]

I'll agree that .007 isn't enough to lay awake at night over. I doubt we could even shoot the difference. I doubt the ransom rest could shoot the difference.

I don't think a Ransom Rest could shoot the difference either. It's just too small a difference to produce a meaningful result.

Another issue is what we define as a meaningful difference in group size? If load "A" shoots a 1.4" group and load "B" shoots a 1.6" group, is that meaningful? Sure, one is smaller. But it's 0.2" at 25 yards. I suppose it would be useful in Bullseye matches, if the shooter's has the skill to take advantage of it, but not many shooters can.

Real world testing forces us to rethink differences in group size. The link above to the 5-shot article shows there can be a ~3-fold difference between group size even when shooting the same ammo! And that's from a Ransom Rest. And a followup article (link below) shows that even when you increase the number of shots in your group, there is still a big difference in the size of the groups with the same ammo. This is forcing me to rethink how I look at my results. Damnit! I hate really checks! I'll continue testing ammo, but I now have a broader perspective on the limitations of comparing group sizes with different loads.

https://www.ssusa.org/articles/2021/2/17/accuracy-testing-how-many-shots-in-the-group

 

[jmorris]

(You used a .300 gage opening for your photos, but you can actualy use any gage size smaller than the caliber of the bullet you are measuring).

Yes, drill/bore any size hole in something you can get a repeatable measurement using. The more you drill the more “datums” you can use for reference.

Doesn’t have to be Hex this with a height gauge is pretty easy to use.

 

[JimGnitecki]

I did just a tiny bit more experimentation tonight which got me some findings that I want to add to the body of knowledge building here.

I have some Federal 147g JHP FACTORY ammo, with both unfired cartridges and cases that were fired in my SIG P210A Target, I took a close look at both.

The tapered crimp diameter of the unfired factory cartridges at the casemouth is very consistently 0.376". That's .002" larger diameter than my .374" taper crimped loads.

BUT, in measuring the wall thickness of the Federal cases, I see that they are pretty consistently .011", which is almost exactly .001" thicker than the .0101" wall thickness of my Hornady cases. .374" + (2 x .0011") = .3762". So, Federal is crimping those factory cartridges to pretty much exactly the same .001" crimp as I am. This makes me think that maybe I am on the right track with my crimping.

By the way, let's make sure you understand what this means: Since the bullet diameter pof .355 plus TWICE the Federal wall thickness (because the case walls SURROUND the bullet) totals to .355" +(2x.011") = .377". But the taper crimped OD is .376", which means Federal is applying .001" crimp across the total diameter, which means .0005" actual crimp on each arc of the wall. NOT .001" crimp on any arc of the wall. So, this is indeed a pretty mild crimp.

Someone pointed out that the 9mm case tapersto a smaller ID as you travel down the case wall, but when taking the ID measurements on both the Federal cases and my cases, I always make sure that I have the caliper jaws in deep enough to go to the depth that the bullet is seated at. So, no, the actual ID is NOT smaller than what I am measuring.

Next, I tried dropping first several of my completed unfired cartridges down the WRONG end of a 9mm go-nogo cartridge case gage. Interestingly, the cartridges drop in until the CASE, not the ogive of the bullet, catches on the case gage. Same with the Federal cartridges. Tis makes sense when you think about it, because the end of the case gage has to be able to handle bullet ODs on the hIGH end of the SAAMI standard, not just average or smaller OD bullets.

But this raises an important point: If you try to literally measure from base to ogive on any tool that uses a gage opening capable of accepting any in-spec 9mm bullet diameter, your efforts will be futile, becsause just as in my testing, the tested cartridges will drop in until their CASES hit the gage.

So, this implies, if I am correct, that the only practical way to measure consistency of bullet seating, using ANY tool you make or buy, is to measure from the base to some consistent diameter point on the ogive that is slightly smaller than the maximum diameter of the bullet, and just make sure that this measurement is consistent, or darn close to being consistent, for all the cartridges you test.

I emailed Hornady though to ask what the slope of the HAP coned ogive is. If they give me that, I can then calculate what the actual true base-to-ogive measurement would be. That, coupled with an accurate plunk and rotate test, provides guidance for calculating the "jump" in whatever firearm you load the cartridges into.


Jim G

 

[noylj]

What amazes me is, even after proof that COL variations of 0.010" means nothing in terms of pressure, velocity, or accuracy, some folks still come back concerned they are going to blow up their gun.
Even KNOWING almost all the variation is in the bullet, they still want to obsess about the insignificant.
Well, if that is your position, please use the two press seating system I described and stop bothering us. I gave you a cure--use it

 

[JimGnitecki]

What amazes me is, even after proof that COL variations of 0.010" means nothing in terms of pressure, velocity, or accuracy, some folks still come back concerned they are going to blow up their gun.
Even KNOWING almost all the variation is in the bullet, they still want to obsess about the insignificant.
Well, if that is your position, please use the two press seating system I described and stop bothering us. I gave you a cure--use it

If this is bothering you, don't follow the thread! Why subject yourself to the annoyance?

COL is different than base-to-ogive. Maybe it makes no difference onyour pistol, but on a SIG P210A, that with the right shooter (not necessarily me) that MIGHT make a difference. I'm eager to find out.

Jim G

 

[noylj]

Well then, find out.
But either do the tests yourself or only believe data and not opinion.
You've been given data, but you shift the goal posts.

 

[JimGnitecki]

I found some good bullet seating information on the Redding website, that applies to the Redding Competition Bullet Seating die I have ordered:

(the bolding of some of the text is by me, not Redding)

"
There are many factors that can cause bullet seating depth to vary when using our Competition Seating Die. First, make sure you're comparing bullet seating depths correctly. You cannot check bullet seating uniformity by measuring cartridge overall length off the bullet point. You must use a bullet comparator, like our Instant Indicator, to compare bullet seating depths. A comparator contacts the bullet at the bore diameter contact point. This is important, as bullets can vary slightly in overall length.

We have designed the seat stem in our Competition Seating Die to contact the bullet ogive as far down as possible. Our Competition Seating Die features a bullet guide that is only .0005-.001" larger than bullet diameter. This tight fit between the bullet guide and bullet ensures that the bullet is seated straight in the case neck. It also limits how far down the ogive the seat stem can contact the bullet(See also my note below). If the ogive of your bullets aren't uniform, you may notice a slight difference in seating depth. Generally, this isn't a problem as modern bullets are very uniform. In rare instances, when using inexpensive bulk bullets, you may find that the bullets were made on several different machines and then blended.
"

My note: What "It also limits how far down the ogive the seat stem can contact the bullet" means is that the seating insert not only does not contact the tip of the bullet, it actually contacts the bullet at pretty much exactly the point where the the ogive diameter becomes the outer bullet diameter that actually contacts the rifling. This is exactly the point you want to control to create the base-to-ogive length that works best in your firearm's chamber.

Jim G