IDescribe

Regarding how much shortening OAL increases pressures, I tested it a few years ago. Obviously, I did not measure pressure itself, as I have no access to a piezo device. What I did was measure velocity differences with the same charge weight, bullet, gun, where only OAL changed, with the assumption that a velocity increase with the same charge weight and bullet MUST mean an increase in pressure. I used a Montana Gold 124gr JHP with 3.6gr of N320, OALs of 1.04 through 1.14. Gun was an HK VP9 and all cartridges were with Starline brass. Results: OAL 1.14 Depth .186 | Avg fps - 925 fps | SD-13 | ES-42 OAL 1.12 Depth .206 | Avg fps - 922 fps | SD-19 | ES-59 | -3 OAL 1.10 Depth .226 | Avg fps - 941 fps | SD-15 | ES-51 | +19 OAL 1.08 Depth .246 | Avg fps - 962 fps | SD-11 | ES-34 | +19 OAL 1.06 Depth .266 | Avg fps - 979 fps | SD-12 | ES-34 | +17 OAL 1.04 Depth .286 | Avg fps - 994 fps | SD-12 | ES-32 | +15 The number out on the right is the difference in velocity relative to the load above it. Notice that the first OAL change from 1.14 to 1.12 resulted in a velocity decrease of 3 feet/sec. This is because that bullet hits the rifling in that gun around 1.13. That 1.14 OAL cartridge was loaded into the lands. But from 1.12 down to 1.04 there was a reasonably consistent increase in velocity as OAL got shorter, and that increase in velocity is more or less the same change I get with that bullet and that powder when I keep OAL the same and increase charge weight by a tenth of a grain. With that powder and bullet, a change of .02 in OAL is worth about the same as a change of .1gr in charge weight -- in terms of velocity, and I assume pressure is somewhat correlated. I have never done a full test like I did above with a different bullet/powder combo. I have, however, in load development, seen the results MANY MANY times of changing OAL by .01/.02/.03 without changing charge weight, and the resulting changes in velocity are consistent with the above test. With powders in the burn rate vicinity of N320, loading to 9mm minor velocities, and regardless of bullet weight, a change in OAL of .02 is worth about the same in velocity as a change in charge weight of .1gr. Changes in pressure (observed indirectly through changes in velocity at the same charge weight), are significant enough to be seen even at modest changes in OAL. This does NOT mean such changes are dangerous or likely to cause catastrophic failures -- that would be largely dependent on where the pressure was to begin with. In the above test, I cut the OAL by .1 with no ill results, and was in no way concerned, given that I was operating down in "starting load" territory, but if I'd been up to 4.3gr at max standard pressure and THEN reduced OAL by .100, THAT could be a very bad day. If you're loading WSF with a 124gr bullet for 1040 feet/sec, changes in OAL aren't going to affect pressure too much. But if you're loading a 147gr bullet with Ramshot Comp to 915 feet/sec, already well into +P range, a change in OAL might violently disassemble your pistol for you.

Right. Most action pistol shooters only see this when the bullet is loaded right into the lands. To expand on what noylj described: Smokeless powder burns faster the more pressure it's under, and faster it burns, the faster it generates pressure, so we have a positive feedback loop. Anything done to increase pressure at the beginning of the burn will increase pressure geometrically through to the peak, and anything done to decrease pressure at the beginning of the burn will have the opposite effect. Such is the nature of shortening or lengthening OAL. As that regards shortening OAL in rifle cartridges lowering pressure (to a point) because of giving the bullet more velocity to pass into the rifling: One of the things that will increase pressure at the beginning of the burn is reducing the rate of acceleration or delaying the movement of the bullet. With the bullet at an OAL that keeps it away from the lands, the bullet picks up a little velocity, and that velocity and momentum helps the bullet pass into the rifling more easily (with less of a hitch or studder in the acceleration). But if the bullet is loaded right into the lands, it sits for a moment before pressure builds enough to start the bullet moving. This delay in bullet movement for a bullet loaded into the lands increases pressure significantly more than does the studder in acceleration for a bullet loaded away from the lands. With rifle powders, the powders burn slow enough, and the acceleration of the bullet before hitting the rifling is slow enough, that the hitch/studder in acceleration as the bullet passes into the rifling still has a significant effect on pressure. So with rifle powders, if you look at pressure with the bullet loaded into the lands, then .003 out of the lands, then .006 out of the lands, then .010 out of the lands, and so on, and so on, you see pressure go down because as the OAL gets shorter, the bullet is building more velocity before engaging the rifling, and thus passing into the rifling more easily. This isn't to say shortening the OAL doesn't also have a pressure increasing effect in terms of decreasing the initial size of the combustion chamber, only that the pressure decreasing effect of allowing the bullet to gain more velocity before hitting the rifling outweighs it. Keep in mind, thought, that all of this is tied to how close the bullet is to the rifling, not to the OAL difference itself. If your two OALs are .001 out of the rifling and .011 out of the rifling, that .010 difference will have a measurable impact on pressure, but if you're looking at .051 out of the rifling and .061 out of the rifling, the .010 difference will amount to diddly. And of course, the slower the powder, the further away you can be from the rifling and changes in OAL matter. And conversely, the faster the powder's burn rate, the closer you have to be to the lands for differences in OAL to matter, which brings us to pistol powders: With pistol powders, the powders burn so fast that once you're out of the lands, there's no further reduction in pressure by getting further away from the lands. This is why we talk about not loading into the lands, or loading into the lands causing pressure spikes. Really, it's about delays in acceleration, but with pistol, because of the fast burn rates of the powders, the only significant delays in acceleration come when you load right into the lands.

I have a Starrett micrometer I used to measure 10 bullets of a few different makes some time back: PD .356 124gr RN -- 1 @ .3560 | 1 @ .3561 | 3 @ .3562 | 5 @ .3563 PD .355 124gr JHP -- 2 @ .3550 | 6 @ .3551 | 2 @ .3552 MG .355 124gr JHP -- 1 @ .3551 | 1 @ .3552 | 7 @ .3553 | 1 @ .3554 SNS .356 135gr RN -- 1 @ .3559 | 3 @.3560 | 5 @ .3561 | 1 @ .3562 ACME.356 147gr FP -- 7 @ .3561 | 3 @ .3562 Bayou .356 124 TCG - 1 @ .3565 | 2 @ .3568 | 5@ .3569 | 1 @ .3571 | 1 @ .3572 Blue .355 125gr RN -- 4 @ .3555 | 6 @ .3556 I have also thrown the mic on some SNS 125CN, and those were closer to .3555/.3556, and some ACME bullets other than the 147FP listed above and found them to be closer to .3564, give or take, and although I haven't bought any BBI since having a mic, I know them to be upward closer to .357, which is probably why my Shadow loved them. BBI are like that great ex-girlfriend I can't remember exactly why I moved past. "Maybe I should call her. I wonder how she's doing these days."

Hornady HAPS are fantastic and I think about that price if you want to buy maybe 5000 at a time? Blue Bullets are .001 smaller than standard sizing for lead and coated lead. They work very well in some pistols, but only so-so in others. ACME is standard size or a hair over, which is a good thing.

Any chance of a .356 124gr or 121gr JHP? That might be the proverbial bee's knees. ?

Sanders already answered, but yes, if you go to 38 Super instead of 9mm, there is a .356 124gr FMJ-RN, that shoots notably more accurately in my Shadow than the .355. Zero also has .356 38 Super bullets with a wider variety of profiles and weights, including a 121gr JHP. If I remember correctly, you're a CZ shooter, and I am pretty sure some CZ shooters have had some issues with the Zero .356 125gr JHP needing to be seated a bit too short, but that 121gr JHP is sweet.

Dude, you keep contradicting yourself. If you can't believe a bullet shoots just as good as a more expensive bullet, you ARE saying you believe one bullet is better than another. You keep saying you'll believe something when you see independent testing, but your own beliefs aren't resting on anything of the kind. You asserted that rifle bullet performance was directly tied to price, then when someone offered a contrasting opinion/example, you said rifle bullets shouldn't be part of the conversation. THEN you offered a rebuttal on the rifle bullets -- that was a double self-contradictory whammy. You're trying to use the Equipment Surveys as indicators of performance, but the trends on those surveys often conflict with your higher price being tied to performance assertion. At some point, you ARE just arguing. A good rule of thumb -- when you have two items of similar production cost and similar performance -- like MG and PD -- and one has a higher consumer price, the higher consumer price is usually tied to marketing (and it's usually a good business decision). I've bought plenty of MG and PD both. I'm not paying a price premium for no performance uptick. I have done the testing with my own pistols. Both have been great, but PD has been slightly better when comparing 124gr PD .355 JHP to MG .355 JHP in whatever pistol. AND PD also gives me a choice of 124gr RN sized .356 for pistols that like that sort of thing, which my Shadow does, and PD does it at both sizes for less money. Zero also offers different sizing and does it for a tad less than MG, or about the same, or a tad more, depending on what quantities I want to buy in. There's just no reason to pay the extra $$ for MG over other options.

Case mouth spec for 9mm is .380. Your chamber should be reamed to accommodate that diameter right at the headspacing step. You should not go larger than that and should probably go one thousandth narrower to account for any crimp variation you get from cases of different length (because the taper crimp does taper, and different case lengths will be crimped to different degrees). I use .377 for .355 bullets, .378 for .356, and .379 for .357 when I care, but in truth, I typically use .377 for jacketed and .379 for coated and call it a day. Coating can be scraped on exit when using a kinetic bullet puller if you have crimped before pulling. The inside of the case mouth might not be perfectly smooth. If you are scraping coating on seating, the coating will build up around the bullet, on the lip of the case mouth, as the bullet is being pushed into the case. If you are not seeing coating build up on the upper lip, you have nothing to worry about. While all bullets can scrape if you don't bell enough, I have not seen any do it more than others when all else is equal, and I've loaded bunches of ACME. I'd recommend you drop back down and start over, belling a little more, a little more, until you don't see coating build up on the lip of the case mouth.

Accurate Arms load data does in fact have data for a 124gr plated FP for AA2, AA5, & AA7 - - it's the Berry's 124gr HBFP. That's what you want to use. For Titegroup and Win231, use the data for the Berry's 124gr HBRN, and while I'd personally use the data directly and monitor for the data's max velocity as a ceiling, if I didnt have a chrono or was just feeling extra cautious, I'd just knock .2gr off max load.

Stop. Just buy a regular taper crimp die. Lee FCD is designed to resize all the way down the case, not just taper crimp. With lead bullets, that resizing function can swage the bullet inside the case, killing bullet to barrel fit, leading to... wait for it... tumbling. Others are correct about those charge weights being relatively light for 124/125gr bullets, and if you're going to shoot 9mm minor, you should increase velocity, but ditch the Lee FCD. You should also give us the other load data I mentioned -- specific bullet models, OAL, etc..

Extra powder and velocity can keep the bullet gyro-stabilized a little longer, but that doesn't mean low velocity was THE problem. It can just as well be that more velocity masked the problem. Key-holing is likely poor bullet to barrel fit OR Damage to the bullet Damage to the bullet can be from over-crimping OR from seating a lead bullet too deep in the case, or from using a crimp die ill-suited to lead bullets. Can you give us more info about your loads -- specific bullet models (brand, weight, profile) and the corresponding OALs? And what kind of crimp die are you using? Is it a Lee FCD?

Toby, land and groove rifling will cut coating as well as the thin plating used on normal plated bullets. The polygonal rifling used in Glocks (and others) is far less likely to strip coating or plating.

You can fix that by adjusting bell to somewhere between where you were and where you are.

Calling a bonded JHP or bonded rifle bullet, or something akin to Speer Gold Dots, bullets that equal or outperform traditional jacketed bullets, bullets that compete in the same market as traditional jacketed bullets, calling those TMJ is a different thing entirely, as part of the goal there is to position them properly in the marketplace. But a company making plated bullets with thin electro plating, a company whose products should be competing against other plated plinker bullets, that company marketing those bullets as TMJ misplaces them in the marketplace, and it's dishonest advertising. They know what they're doing.

The above is correct. These are not CMJ. They're plated. Use any 124gr plated RN data you like. AND I personally would not buy bullets from a company that marklets plated bullets as jacketed. If that's what they're doing, you should not trust them for anything.

I just saw on their website -- they're saying their coating is a proprietary liquid polymer blend, not powder coat.

OP, they're going to perform exactly the same, with different OALs. Either will work well in more or less any pistol. And ACME rocks.

I don't follow. Did they change something to stop the smurf fingers?

I wouldn't worry about the smoke from the coating, not because it's safe, but because it's not as unhealthy as the lead styphnate in the primers. Lead styphnate in the primers is where most of your lead exposure comes from when shooting, and if the indoor ventilation systems are so poor that you end up with problems from coating exposure, you're already screwed on lead styphnate anyway. All that said, smoke from coated bullets can be mitigated by using bullets from a company that cures the coating sufficiently. ACME is probably the best.

One of the advantages of reloading is tailoring your cartridges to the pistol. If you set out to load cartridge for all pistols, you end up with a cartridge that is best for none. Moreover, CZs typically require shorter OALs than standard 9mm, and 2011s can employ longer cartridges than standard 9mm. You're trying to come up with a compromise between opposite ends of the spectrum, exacerbating the issue mentioned above. Plated don't have leading issues. Coated don't have leading issues if sized properly for your barrel. FMJ, even with the exposed base, don't have leading issues. None of these should create leading issues if chosen and used properly. Generally speaking, jacketed is more accurate than plated, which is not the same as saying plated can't be accurate, it's just not as easy a path. And generally speaking, jacketed bullets where the jacket is swaged toward the base (JHP) are more accurate than those where the jacket is swaged into the nose (FMJ-RN and FMJ-FP). How much more or less accurate is heavily dependent on distance. There are reloading considerations that matter at 600 yards that don't matter much at 50, and reloading considerations that matter at 50 yards, that don't matter much at 25. If you're having accuracy issues at 25, your bullet is fit poorly to your barrel, or you're over-crimping, or your pistol sucks, or you've tuned for recoil over what shoots most accurately in your pistol, or you're using plated. Precision Delta offers JHP at 8.9 cents per bullet, including shipping, if you buy 2000 or more at a time. It's incredibly difficult to beat that if your are looking for a combination of price, performance, and ease of loading. Same goes for RMR's in-house JHP -- RIGHT there in price and performance. Zero's 124gr JHP are equally as good, maybe even better, though a penny more per bullet. And if you're not on the "Heavy bullets feel so soft!" lingerie tour, Zero 121gr JHP are the proverbial bee's knees. If you're looking for inexpensive and easy, those are your best options.

Bench, best practice is that YOU determine your max OAL with a plunk test with a bullet, start there, then tune it during load development. If you know what your OAL is going to be before you have the bullet in hand, you are leaving out steps and hurting your potential. Load data is NOT a recipe. It's a field report. YOU determine your OAL with evwry new bullet in every gun.

Determine your max OAL for that bullet in that barrel. Then test a ladder from 3.9-4.3gr for accuracy, and use the most accurate load.

Mystery solved. ?

I'm going to go out on a limb and guess that you were using a light charge of a fast burn rate powder with with the IDPA load, where gas mass is low, and the pressure falls off too fast to take advantage of the longer barrel, as opposed to the Gold Dot +P, which uses a slow powder, with considerably more powder, with more gas, and keeps pressure higher longer and continues accelerating the bullet for more of the barrel.

Whatever you used to determine you were making power factor before, use that again. That said, if for some reason that isn't an option, why not just make a ladder from 3.4 up to 3.7, test for accuracy, and choose the most accurate load. I can assure you the difference in the recoil impulse isn't going to affect your splits.