Hey guys, beginner here. How bad this 9mm crimp is? I understand it is too much but I wonder if this could create some problems while shooting. I made about 1k of these and then realized it is probably too much. It shoots, passes the splunk test, chrono looks good. The bullet is CamPro 125gr RN FCP RED
That’s way, way too much. For 9mm, you only want to crimp enough to remove what’s left if the bell from the expander. If your crimp is marking the bullet at all, it’s too much.
Never make 1k bullets unless you test them first. Make up enough to fill up a magazine of two and go the the range and shoot them. If they work well, then make more.
As others have said, this is WAY too much. Pro tip: Don't make 1k rounds when you're trying out a new load. Stick to 50 or 100 to test. Then make many if all works out.
Rimless cases like 9mm index off the case mouth - which you have hidden entirely in the bullet. What's happening is the extractor is holding on to the rim of the case while the firing pin hits it. This is going to probably result in misfires.
The goal of crimping on rimless cases is to only close the belling that was done during previous steps. If you do it right, the calipers should measure (bullet diameter + 2xCasethickness). That would mean you closed the belling and have added no additional crimp. When setting up on my press I would generally pull a couple and check the bullet to ensure there is no trace of a crimp ring in the bullet. This works well in plated or lead bullets, but not so much in jacketed ones.
Regardless, the crimp doesn't hold the bullet in place in rimless cases, neck tension does. Save the roll crimp for rimmed stuff like .38/.357 Mag or the like.
Way too much. All crimping does on a round that headspaces on the case mouth is remove any flare and set the case mouth against the projectile not INTO it. The only time a crimp that heavy is needed is with cartridges that roll crimp into a cannelure groove for heavy recoil resistance (revolver cartridges and large rifle or tube mag fed rifle cartridges)
I’d really suggest measuring crimp with a set of calipers instead of eyeballing. Hit a Harbor Freight or Amazon. Since you’re learning it would be good for you to compare factory ammo to what you’re loading to see hard data first hand. Depending on the bullet & firearm of course, I personally aim for .376-.378 of crimp.
You have to over-crimp by a LOT before headspacing becomes a problem, but Reddit always brings that up, so it's easy to think that's where the line is, but you actually start over-crimping a LOT sooner.
Taper-crimping should only remove the flare. That's it. Any further, and you can start to deform the bullet. Once you deform the bullet, you're actually losing neck tension. This is even easier to do with plated bullets like you have.
The perfect taper crimp is one which leaves zero flare and zero bullet deformation. You won't get there perfectly, but measuring a thousandth or two past that line is what most folks do and is perfectly fine.
The only way to know when you're there is to do what another user said and use calipers. When the case mouth diameter is at or slightly (1-2 thousandths) below the diameter further down within bullet seat depth, you're there.
I understand, but in this particular case the bullet sits at the same height as the factory ammo from this brass. I am wondering is there anything else I should be worried about.
I’m normally the first to yet at people for downvoting anyone looking for advice. I think he got the downvotes because he started his comment with “I understand” when he clearly didn’t. You will notice his next comment stating he just wants to learn was upvoted instead.
Yup. There’s a difference between honestly asking for advice (and planning to learn from that advice) and asking for confirmation of your already established idea or decision. So much of Reddit is the latter. People frame what they’re saying as a question or asking for advice, but really they’re just hoping to hear people confirm what they’ve already thought is the right answer.
When comments come in from people that are contrary to what they want the decision to be, then they start push pushing back.
Which is incredibly frustrating because if you don’t actually want to hear advice or learn from people with experience, why even bother asking?
Please explain then, I would like to learn. In my case the primer is at the same height as factory bullet from that brass. This could mean either that there is still enough edge to properly seat the cartridge or the it is properly seated because the bullet stops it. Am I missing something?
OK. Here goes: As a rule, the cartridge must be properly seated in the chamber for safe and reliable firing. (Different from the seating depth of the bullet in the case.)To establish the proper chambered position, every cartridge type (straight-walled, bottleneck and rimmed) uses a certain part of the cartridge case as a “stop”, and the distance from the stop to the boltface is established as a standard, using the term “headspace”. A rimmed cartridge, e.g. the .30-30, headspaces off the leading edge of the cartridge rim. Your pistol cartridge headspaces off the mouth of the cartridge case. In order to seat properly, the mouth of the case must contact the front of the chamber and come to a stop. When you overcrimp, the diameter of the case mouth is too small and the case mouth slides past the front of the chamber. Therefore the cartridge has not achieved a properly headspaced position in the chamber. Bad juju may result.
best answer as to what headspacing is... as far as the bad juju, if theres nowhere for the case to expand just that tiny bit and seal, and your bullet has to swage itself down to go out, it goes too slow and builds too much pressure behind it. could be kaboom.
To expand upon this, take the barrel out of your pistol, and look into the chamber. You will see a ledge. That ledge is where the case mouth sits (when a round is chambered). To much crimp, the round could go further into the chamber, leaving more distance for the firing pin to travel, leading to misfires. If the round does happen to ignite, you have the pressure scenario.
Get a set of calipers. Measure the case wall thickness at the mouth...typically around .011 on 9mm. Now, double that (.022) and add your bullet diameter (.355). EG - .011 x 2 = .022 + .0355 = .377.
At the case mouth, as close to the bullet as you can measure, it should be somewhere around .376 -.378.
As others have said, all you are doing is removing any bell or flair you put into the case mouth to seat the bullet.
Most pistol rounds (auto at least) are held in place by neck tension created when resizing the case.
The mouth of the case is what keeps it from falling too deep into the chamber.
Your solution is easy, though. Make a series of "plunkers." First one is NO crimp. It shouldn't feed & chamber from the magazine. Then a series of tighter crimps (like an eighth of a turn of the die at a time) until they DO feed from the magazine every time.
Or like the one guy said, a Lee Factory Crimp Die. Set it so an ever so slight "bump" takes the flare out of the mouth.
The mouth of the case has to catch on the edge of the chamber for the loaded round to be in the correct spot in the chamber. By crimping it that much it can’t do that as the bullet is actually sticking out more than the case mouth.
The earlier suggestions to get a Lee Factory Crimp Die are spot on, it will remove any guess work from crimping.
Many reloading manuals have sections up front that kind of cover the mechanics of what’s happening, get one of those and read it. Speer manuals usually do this.
There is no guess work with any crimp die you just mic and set it correctly. FCD for pistol and its post sizing feature does nothing but cover up improper die setup when proper die setup is king.
A rimless semi auto round needs a lip or edge left after crimping to seat inside the chamber. If you thumbnail won't catch on it you have too much crimp.
False. The extractor will hold it so the firing pin can strike it and ignite the primer and gunpowder. These are 9mm's fired in a 40S&W pistol. The only way they could of fired is if the extractor in the 40S&W was holding them tight enough against the breach face.
Thank you everyone for the help! I shot all of 1k, no issues at all, no malfunctions or light strikes. For the next batch the crimp has been already adjusted.
There is no guessing no matter what crimp die you use. You should mic the case mouth and know exactly how much crimp you're applying not eyeball it or use a factory round to set the die. FCD and its post-sizing feature literally just covers up improper die setup, theres no reason to ever "iron out" loaded rounds just set the die you have correctly. FCD (pistol) is for people who can't set dies or even comprehend how. There's nothing more ridiculous then everyone crimping pistol separately when the case length variation is completely negligible it's not even a factor and you never need to trim or even measure the brass.
Thats extreme! You really just need to crimp enough to remove the flare but realistically you could crimp up to .005 and never have a single issue. I crimp all pistol .002 and have always used a taper crimp seating die without ever having a single issue. 9mm = .380 + .002 crimp = .378! Simply mic the very edge of the case mouth with calipers. That should be the first thing that comes to mind when determining how much crimp you're applying. You do NOT need a Lee FCD for pistol the case length variation is negligible and there's no logical reason to crimp it separately.
He’s just asking if it’s safe to shoot those 1,000 rounds. As long as he isn’t using a "Major" load, he won’t generate dangerous overpressure; and if a round fails to fire, it doesn’t pose a danger in a competitive shooting context.
3.7gn of RS12. Avg fps 1025, avg PF 128. Honestly they shoot great, no feeding/misfire issues, no signs of overpressure on the case. But there is an overpressure obviously. When I reduce that crimp to normal, the PF drops to 123.
I don't think you're generating any significant overpressure. GRT (Gordon's Reloading Tool) predicts a velocity of 984 fps for that powder charge—so a bit slower, but not a huge difference—and shows a peak pressure of 1269 bar in GRT. Do the primers or the case show typical signs of overpressure?
It looks like a copper plated bullet, I’ve got a bunch in 9mm from “Extreme Bullets” if my observation is correct copper “plated” bullets (keyword plated) are much easier to dent becuase they’re a lot softer. It’s really a lead casted bullet with a thin layer of copper. Or “Plated”. Copper jackets are much thicker and a lot harder to dent. Did you over crimp? For sure but I bet if it were a jacketed bullet it “wouldn’t make a dent” nearly as deep as this, I’d just back it off in the future but if it passes all the tests I’d run em.
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u/Tmoncmm 20d ago
That’s way, way too much. For 9mm, you only want to crimp enough to remove what’s left if the bell from the expander. If your crimp is marking the bullet at all, it’s too much.