By Kevin Newberry
This is the companion article to Important Steps to 9 x 19mm +P Defense Load Success. It is a separate article because of the carry over to other autoloading cartridges as well.
The Editor
One thing that the editor and I both strongly agree on is the importance of a good and proper taper crimp and I hope to enlighten as many as possible on a subject that I believe is far too misunderstood by even handloaders considered to be giving expert opinions.
I’m going to start off with a question. Its simplicity may have you wondering why I ask, but in my time in various reloading sections of gun forums, there a few topics appearing to be as misunderstood. Here we go.
- Have you ever cut soft copper tubing with a tubing cutter? As the cutting wheel cuts deeper into the tubing, the pressure from the cutting wheel reduces the diameter of the tubing at the cut. 2. What is a taper crimp?
The handloaders that also happen to work as professional plumbers might see where I’m going with this, but go to the reloading section of your favorite gun forum and ask if your autoloading cartridge needs to be taper crimped, and by how much?
Types of Crimps.
If the answer is just enough to remove the flare left from the expanding die, you might want to ask the respondent question #1. Ladies and gentlemen, when you simply remove the flare caused by the expander to a neutral position where the case angle from head to case-mouth is the same, pardon me for saying this, BUT, you haven’t crimped anything!
The fact is, if you simply want to remove the flare added by the expander, that can easily be done while you seat the bullet without any detriment to OACL, OverAll Cartridge Length. I am one of those you will see recommending that you should seat the bullet and taper crimp the case in two separate operations, and I’m going to explain a very easy method for applying the correct amount of taper crimp as we discuss its benefits.
Most likely, you have seen or will see the statement that the taper crimp does nothing to prevent bullet setback into the case and that the only sure method for preventing setback is through adequate case-neck tension. So, again, ask the respondent how much case-neck tension is enough case-neck tension. While you’re waiting for a reply, maybe ask question #2!
It has been my unfortunate experience to see the automatic response of “just enough to remove the flare” by folks who have very little useful information to accompany their statement. Different load manuals make different statements on the subject, but universally it is accepted that a proper taper crimp can aid in reliable feeding of the autopistol cartridge. The better explanations, as is the case of the excellent little manual included in the latest Western Powders Load Guide’s Getting Started is that it can be an aid to preventing bullet setback. At this point I’d like to quote a former mentor, a WWII veteran with nothing more than a high school education who helped develop a formula to calculate friction losses in various types of pipe to four place decimal accuracy using a handheld scientific calculator while many or most engineers were still referring to charts and graphs in reference books. His axiom, “If a man tells you that he has 30 years of experience at something, but has been doing it wrong for 29, he actually has 1 year of useful experience! We don’t want to be that guy.
Case-neck tension is indeed a very important step in preventing the very dangerous possibility of bullet setback, but, it is not the only step! How much is enough. Well, in my load manuals that go back 30 years or more and reading expert opinions in the various reloading articles from beyond then, the author will explain what many of us refer to as the “push test.” That is taking the finished round and with the nose of the bullet pressed squarely into the wooden table top of your reloading bench, or a block of wood if your bench is constructed from steel. Measure OACL before the “push test” and after. Did it shorten? If so, there is not enough case-neck tension and we’re gonna discuss remedies.
While at your favorite gun forum, if they have a separate section for factory ammunition, you will or have seen recommendations for rotating rounds that you chamber in your defense pistol. The reason being that with multiple impacts with the feed-ramp, OACL is decreased. Sometimes it can shorten to dangerous conditions. In my SPEER #11 load manual from 1986, they mention taking a 9 x 19mm round that they pressure tested at 28,000 CUP, and when shortened by only .030”, pressure jumped up to 62,000 CUP which is beyond the proof testing pressure level for the cartridge and 9 x 19mm pistols. According to what I read about the European CIP test method, proof pressure is tested at 30% above Maximum Average Pressure, or MAP. Obviously, this is a very serious potential problem that can result in injury to the shooter, and/or damage to the pistol.
So, how do we prevent bullet setback? Giving credit where credit is due, I believe I first saw this recommendation given by Layne Simpson of Shooting Times years ago. He stated that what we call the expander button should be .002” smaller in diameter than the jacketed bullet you are loading. For 9mm die sets, that would mean a diameter of .353” for the nominal bullet diameter of .355”. When you perform the “push test” and find that OACL has shortened, think about the effect of that same round impacting the feed ramp during the feed cycle. That is what is occurring with factory loads being discussed in regard to rotating the top round in the magazine that gets fed into the chamber. The first thing a handloader should do is to remove the expander button from the expanding die and measure its diameter. If it is .354” but the bullet moves rearward during the “push test” then obviously it needs to be smaller in diameter. There is no magic or voodoo required to correct it. If you perceive it in that way, contact the die manufacturer and they’ll likely replace it. With confidence and a light touch with machine paper or very fine grit sandpaper, lightly tape any threads that might come into contact with the chuck of your turning machine. You could also have this done at a local machine shop where most of us don’t have milling machines in our personal shops. A high speed drill press will work and if you’re confident enough in your ability, a hand drill/driver can be used locked at its highest speed. As the expander button is rotating, just lightly touch the machine paper to the area that goes into the cartridge case. Stop at that point and measure its diameter to see if you’ve removed any metal. You should not need to reduce the expander button’s diameter to less than .002” of the jacketed bullet diameter. The next push test will demonstrate the level of your success. Other factors can be involved such as cartridge cases that have thinner case walls but we’ll get to that in a moment.
When performing the “push test” and let me just say that I’m a fairly large guy and that there’s no lack of push, if your bullet is setting back by only .001” or .002”, you may be able to correct that with additional taper crimp.
So, how much taper crimp is enough taper crimp? Usually around .002”+/-. If it’s a .45 ACP cartridge .003” of taper crimp is not going to hurt anything in the slightest way. Obviously the 9 x19mm cartridge is a good bit smaller and what I look for is at least .0015”, fifteen ten-thousandths of an inch or what a machinist might refer to as 15 tenths. Okay, your dial caliper only reads in increments of .001”, so in this case the indicator should be midway between a .001” and .002” reduction in diameter. Again though, if you use .002” you’re not going to hurt a thing. I cringe when people start talking about improperly over-taper crimping to the point of bullet deformation. I also cringe when the topic of Factory Crimp dies come into the discussion. Many are not aware that a Factory Crimp die is a post sizing die first. If one is out of spec by one thousandth to the smaller diameter, guess what diameter your .355” bullet will be after running it through that die. Learning to use a taper crimp die is not magic or voodoo, either. Most bullet seating dies incorporate a crimp function. Roll crimp for revolver rounds and taper crimp for autoloading rounds, but that was not always the case.
In this case I will tell you that I use and recommend REDDING’s separate taper crimp and their Profile Crimp dies for revolver loads. In both cases they work to perfection. Most guys that run progressive presses will have a separate taper crimp die installed in the station after the bullet seating die. If you load on a single stage press and have only the 3 die set it means that after you seat your bullets you’ll need to remove the seating stem and adjust the die to taper crimp. I have made enough measurements over the years to conclude that if you seat and crimp in one single operation you’re going to get larger variations in OACL. If it’s just blasting ammo and you’re comfortable with that, well, that’s entirely up to you. Most of my autoloading rounds have some defense application, or the practice thereof. Like my powder charges I don’t want any more variation than necessary. Unlike my hunting rifle rounds I’m not going to weigh each individual powder charge thrown because it isn’t necessary with a good powder measure like the RCBS Uniflow or another brand’s equivalent. And particularly not when using fine grained spherical powders with high bulk density like Accurate #5, #7, #9 and 4100 or Ramshot True Blue and Enforcer. Silhouette is not quite so dense at 800 grams/liter (.8 grams/cc) but it too drops very consistently.
It’s the little things like consistency of the powder-drops and OACL combined with one of these excellent powders that will help you get those single digit standard deviations from your defense loads. I use Silhouette quite often because of it being treated to yield very low flash.
Lee Turret Press
In the case of REDDING’s stand alone taper crimp die you’d really have to work hard at screwing up. First you have the inner wall of the die that is angled slightly more than the case’s taper. Many taper crimp dies operate on that principle alone. But if you look up into the internals of the REDDING taper crimp die you notice a second smaller and more severe taper angle that works directly on the case-mouth. So, with your seating die that also has a taper crimp function, raise the ram and cartridge to full height then turn the seating die without the seating stem installed until you feel the die come into contact with the case-mouth of the cartridge. Then, depending on your hand strength, you may be able to turn the die enough to remove most or even all of the flare from the expanding operation. Than set your seating-stem to get the desired OACL. As an example, with my 20 something year-old REDDING Boss that uses top-dead-center as all REDDING presses do, I can keep OACL tolerances to +/- .002” with most JHPs and those that are very uniform under +/- .001”. The LEE Classic Turret I use a lot these days also has a form of top-dead-center and I was quite surprised to find that it allows minimal OACL variations.
Now to the perfect taper crimp. If you remove the flare during the seating operation as I mentioned in my own method, the case-mouth will be at or near what I call a neutral position, or in line with the case-wall. Hey, I’m old, so I’m not ashamed to put on some reading glasses to get a good look, or you can just use a magnifying glass. There is no assurance that the case-mouth diameter will be a SAAMI spec of .380”. More than likely it will be less to say .377”. So once the case-mouth appears to be in alignment with the case-body, measure the diameter of the case-mouth. I do this with a dial caliper and in a moment we’ll discuss how much taper crimp will need and what the measurement should be when just removing the flare. You’ll need some degree of manual dexterity but if you place your off-hand in a position to support and index the caliper you should be able to get right on the case-mouth and naturally, it’s easy to find out if you are above the case-mouth. Happens to me all the time. I’m not perfect either, so I just proceed on until I get it right. Once you know the case-mouth diameter it’s time to apply the crimp. Raise the ram and cartridge again then turn the die down until it makes contact with the case-mouth. Give the die about ¼ turn then remove the cartridge and measure case-mouth diameter again. It probably won’t be exactly as much crimp as you want to apply, but it will give you a feel for how much you apply with each rotation of the die. And, each manufacturer will have their own recommendation for how much you should make that first turn of the die. Take it slow and easy and you’re gonna wonder what all of the fuss is about. Perfection is fairly easy to achieve, IMO, and I am speaking from my experience using the REDDING stand-alone taper crimp die. Back when I used 3 die sets and a single-stage press I seated the bullet while just having the crimp set to remove the flare, then I removed the seating stem and adjusted the die for the separate taper crimp, the 4th operation. If I measured .377” before the crimp I’m going to be looking for .3755” or even .375” will only be .002” of taper crimp. Another thing the taper crimp die does, although you might need a microscope to see it, is to apply uniformity of the crimp and case-neck tension about the circumference of the case around the bullet.
Cannelure shows above belled case neck.
Now let’s talk about that bullet deformation thing. Has anyone ever seen a JHP for a revolver load? Of course you have. You know that the bullet has a cannelure for the case-mouth to be rolled into, hence roll crimp. Is the bullet deformed? Is that area of smaller diameter going to be a detriment to accuracy? Okay, then, what’s so different about an autoloading pistol bullet other than there being no cannelure. If you deform a bullet by taper crimping you obviously needed some help well before you attempted to do it! We know that many straight walled cases are not technically straight and that the 9 x 19mm has what we refer to as a tapered case. The reality is that most all autoloader cases have some taper regardless of how slight. Only .003” in the case of .45 ACP. We also know that these cartridges headspace on the case-mouth where most bottle-necked pistol cartridges headspace on the shoulder of the cartridge just like bottle-necked rifle rounds. That’s why we have a SAAMI spec for Max. Diameter at the case-mouth. If your case-mouth is too large in diameter it may not fully seat in the chamber which can not be allowed to occur either. The taper crimp dies help there as well and if you weren’t using a taper crimp, an out of spec cartridge with an oversized case-mouth could cause an out-of-battery event you might not catch otherwise. Again, potentially dangerous. The truth is, taper crimp dies have not always been around. They were coming into vogue just as I was starting out, but still, some die makers did not offer them. Hornady, as an example was the last manufacturer I can remember that didn’t offer a taper crimp die about 20 years ago, maybe less. The seating die, in fact, did remove the flare but did not reduce the case-mouth diameter. So, how did the older generation survive without taper crimp dies? Well, think about all of the different pistols you have knowledge of and think about what type of feed-ramp they have. This is funny because I have seen more misconceptions by 1911 shooters regarding taper crimp than by any other pistol type. And if I were to rate things in relation to the barrels feed-ramp I’d say that no pistol benefited more from taper crimping than John Browning’s 1911. So what did the old-timers do? They learned something we refer to as finesse! They applied a very light amount of crimp on the case-mouth using a ROLL-CRIMP die to aid feeding reliability without crimping so much as to remove the case-mouth’s ability to properly headspace.
Now onward with that cannelure/deformation thing. Even with a perfect taper crimp of say .002”, if for some reason you have to pull a bullet you’re gonna see a micro-ring on the bullet caused by taper crimping the case-mouth into the bullet. You gotta really screw the pooch to use so much taper that the case-mouth would be reduced in diameter enough that it wouldn’t properly headspace, not that you want to do that for any reason other than experimenting. The micro-groove is what I consider a mini-cannelure, so when the case-mouth is folded into the bullet causing the micro-groove, it also acts as a locking mechanism to a degree while presenting a smaller case-mouth diameter to the chamber. If you taper crimped by .005” the cartridge will still properly headspace, you just created a slightly larger groove into the bullet. There are differences of course as in the case of dies that only use the singular taper angle. The case-neck below the case-mouth will be affected to a greater degree and that distance will be determined by the difference in angles between the case and the dies internal taper angle.
Now let’s talk about lead bullets for a moment and cast bullets specifically. If you remember how I set up my dies, or you want to glance back you’ll probably understand this better. The accepted rule for loading cast bullets is that they should be at least .001” larger in diameter than your barrels groove diameter. And if you don’t know how or haven’t done it yet, familiarize yourself with the process of slugging the bore of your pistol barrel. Even if you don’t load cast or poly-coated bullets it is still beneficial to know the groove diameter of your pistols barrel as it will have some effect on pressure. Another reason we work up loads at lower levels rather than start with the Max Charge of powder. Different manufacturers have different standards for tolerances. You may find that the groove diameter in your 9 x 19mm pistol barrel is not .355”. The tighter the bore, the greater constriction on the bullet so there can be no one size fits all. Your cast bullets may need to be greater than .356” for your 9 x 19mm pistol. All of the bullet hardness in the world will not prevent leading of the bore caused by an undersized bullet and even a cast bullet of groove diameter may not completely seal in the bore. Luckily for all of us and particularly the next generation of handloaders, poly-coated bullets are here to stay! We just need to persuade the poly-coated bullet makers to give us hollow points with the proper alloy for expansion. Some of you may remember when Smith & Wesson, not Federal, originally introduced the Nyclad bullet. We might even get the jacketed bullet-makers to take notice and get some kind of reality check on JHP prices if supply and demand issues get straightened out.
The fact of the matter is that when you load an oversized cast or poly-coated bullet, you don’t have to taper crimp if you’ve removed all of the flare during the seating operation. You’ll have plenty of case-neck tension without taper crimping because the bullet is larger than nominal diameter. As an example, with my seating die set down far enough for the taper crimp function to only remove flare, I never change the depth of my die for jacketed or cast lead bullets. You’re not applying any crimp to the lead bullets so I just remove the taper crimp die from the turret when loading cast or poly-coated bullets. Jacketed bullets will go on to get taper crimped as the final operation.
Then we get to another area I that alluded to earlier: case-wall thickness. Not so much in 9 x 19mm or .40 S&W, but far too often with .45 ACP cases. I have not and will not buy dies for problems that shouldn’t exist in the first place and this is one such example. Remington brass is as thin as I’ve run across in .45 ACP. Very few are as thin. The solution? You can run out and buy a U-Die, as in undersized, but I’m not an advocate of that either. Some people do not consider the entire mechanical process. Yes, the U-die will reduce the case-neck diameter below that of a standard resizing die. But at what price? With higher pressure rounds the brass will work harden faster and reduce case life. We’re actually lucky that this is mainly a .45 ACP issue. Even still, I do not own a U-die, M-die, etc. Separate taper crimp dies are the limit for me. The .45 ACP’s lower operating pressure of 21,000 PSI/19,900 CUP is a bonus here vs. the 35,000 PSI rating for the 9 x 19mm and .40 S&W. And if you use them, the .38 Super +P, 10mm, 9 x 19mm +P, and .357 SIG are even higher in pressure in that respective order. Another bonus I’ve found with REDDING Titanium Carbide sizing dies is that when I’m resizing cases I can tell without looking at the headstamp if something is amiss. In the case of Remington .45 ACP brass, I just toss them into a separate bin and use them or other thin wall brands for cast or poly-coated bullet loads. My rule of thumb is that if a .45 ACP’s case-wall thickness (measured within about 1mm of the case-mouth) isn’t .010” or thicker it goes into the bin for cast bullet loads. Concerning 9 x 19mm brass, you’re more likely to come across cases that are thicker rather than thinner.
Silhouette by Ramshot, features a flash-reducing compound that greatly decreases muzzle signature.
Now for that simple method I mentioned. Several load manuals recommend something similar but may not get into specific dimensions. Some of us may have to do some case segregation by hand at first, but over time you’ll have a greater knowledge of what to expect from the different brands of cases. Since variations are more common with .45 ACP I’ll use it in this example. As I said, for my JHP loads, I like to see case-wall thickness near the case-mouth at .0105”. That’s between .010” and .011” on your dial caliper. The diameter of your JHP should be .451” but you should confirm that. The SIERRA manual recommends it like this. Measure case-wall thickness and double it and then add the bullet diameter to find the case-mouth diameter with no crimp applied. In my case using Winchester brass, that’s .0105” X 2 = .021”. Now add the bullet diameter of .451” and your finished case-mouth diameter with no crimp should be .472”. Remember, the dimension listed in your manual is a SAAMI Max. recommendation and the brass you use is likely to be different. In the case of the .45 ACP, SAAMI recommends .453” as the maximum case-mouth diameter, so with our example of .452” we know that we are below that. But now you know what the finished case-mouth diameter should be after removing the flare with no taper crimp. That is what I referred to earlier as the “neutral” position and the case-mouth is in line with the case body. I want .002” of taper crimp on my .45 ACP loads, so it’s a simple matter of subtracting .002” from the case-mouth diameter with no taper crimp. .472” – .002” = .470” that is the case-mouth diameter after applying .002” of taper crimp and like I said, if .003” of taper crimp is applied, your loads are far from out-of-spec in terms of proper headspace. There is no reason why should go beyond that for reliable defense loads, but still, perform the “push” test to confirm that the bullets do not setback.
Now let’s do an example for a 9 x 19mm load. My Winchester brass typically measures .011” thick. Those brands that go over .012” are going to get set aside because the amount of crimp is going to increase with thicker walled cases. Use them for plinking loads if you don’t want to readjust the taper crimp die. Here we go; .011” x 2 = .022” + .355” (bullet dia.) = .377”. So what I’m looking for is .0015” of taper crimp to get a finished case-mouth diameter of .3755” and those that measure .375” only have .002” of taper crimp and inconsequential as I mentioned above. So, the method is as simple as this. Case-wall thickness X 2 + bullet diameter = case-mouth diameter with no crimp applied. For .0015” of taper crimp you simply deduct that from the “neutral” diameter of .377” with no crimp applied .377” – .0015” = .3755”. There will be thickness variations within the same brands of brass. So if there are +/- .0005” variations, your loads after taper crimping will vary from .375” to .376” and that’s as good as you need them to be provided the cases you are using measure .011” in case-wall thickness. When any dimensions change like bullet diameter or case-wall thickness just alter the formula accordingly. I can chamber, eject and re-chamber a round many times without it shortening by even .001”.
And, to give credit where credit is due, I did not come up with this formula. A relatively new reloader posted it a good many years ago at CZ Forum and all I could think was, it don’t get anymore simple than that, and why hadn’t I thought of it before then! See, you can teach an old-dog new tricks. Good luck guys and happy taper crimping!
Kevin Newberry
Firearms expert, Kevin Newberry is also the author of Kilroy, Kilroy Was Here, which may be found on Amazon at http://www.amazon.com/Kilroy-Here-Kevin-L-Newberry/dp/1508511454