COAL gets smaller when chambering


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SpentCasing
March 30, 2013, 07:31 PM
hey guys im loading up dummy rounds to try to get my press setup properly. im loading 9mm 124gr XTP/JHP. no matter what COAL i use (1.100, 1.090, 1.075, 1.060) my COAL shrinks ~0.010 when chambering. Why is this? Im using Hornady dies on a LnL press with Lee FCD in the last station. Any ideas?:banghead:

ETA: crimp is set by turning die 1/4 turn until bullet stops moving when pressed by hand against the bench. even after that it still shrinks 10 thou when chambering. pistol being used is a G17. i loaded 5 bullets with COAL of 1.090 and everything fed and cycled fine but when testing with dummy rounds (no primer or powder) I get setback upon chambering.

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tightgroup tiger
March 30, 2013, 07:40 PM
Take one of your loads out of the press before you run it through the factory crimp die and try to push the bullet into the case with your fingers or push it against your loading bench for more leverage.

You shouldn't be able to move it.

I'm betting you have no neck tension on your case holding the bullet and it's slipping going into the chamber.

You may be running the flaring die in the case to deep, over expanding the mouth. The neck tension is what holds the bullet still, not the crimp die.

SpentCasing
March 30, 2013, 07:44 PM
You may be running the flaring die in the case to deep, over expanding the mouth.

hmmm, im just barely opening the mouth just enough for the bullet to sit. ill double check that though. thanks.

Blue68f100
March 30, 2013, 07:45 PM
Loose the LCFD, should not need it.

I do not how your measuring OAL but on HP the length (tip to bottom) is not consistent. your variation could just be the where your contacting the bullet. Take your calipers and measure some and see for your self.

bds
March 30, 2013, 07:47 PM
You should determine the OAL by using the barrel drop test - Start with OAL that won't fully chamber the round in the chamber, incrementally decrease the OAL until the round drops in freely with a "plonk" and spin without hitting the start of rifling. Next, determine the working OAL by feeding the round from the magazine and releasing the slide. If the round won't reliably feed/chamber, incrementally decrease OAL until it does.

As Blue suggested, try leaving the FCD out and see if that makes a difference. That means adjusting your 3rd die to seat and crimp in the same step but that's how I reload. I only use FCD with jacketed bullets if the bullets are out of round or have other problems.

As to the amount of taper crimp, I use .020"-.021" added to the diameter of the jacketed bullet so for .355" diameter bullet, I use .375"-.376" taper crimp.

SpentCasing
March 30, 2013, 08:03 PM
i think tiger nailed it. i seemed to have been over-expanding the mouth. bullet easily moved after seating. tuned it up a bit and it seemed to do the trick. now im only losing ~.001 when chambering.

as for everyone else who responded, thanks for the help and info on tuning the dies.

kingmt
March 30, 2013, 08:09 PM
You said crimp until the bullet won't move. The bullet shouldn't move with no crimp. Your sizing die doesn't sound like it is doing it's job. What is the head stamp on the brass.

tightgroup tiger
March 30, 2013, 08:21 PM
hmmm, im just barely opening the mouth just enough for the bullet to sit. ill double check that though. thanks

If that's the case there's not much left But the FCD.

The only other thing I can think of that hasn't been mentioned is I've had a problem with XTP's in deforming the hollow point with the seating die with tight cases and/or the wrong seating stem. That messed with my OAL and drove me crazy with my press until I figured out what was happening.

But that doesn't sound like your problem.

Lost Sheep
March 30, 2013, 09:04 PM
One problem with the Lee FCD (of which I am a fan, but there are limits to my fandom) is that of the post-sizing function.

To ensure reliable chambering, the Lee FCD has a sizing ring in it. This swages (sizes) the assembled round as it leaves (incidentally, as it enters, too) the FCD. This ensures the size of the round is within SAAMI specifications.

When you swage brass, it springs back a little.

When you swage lead, it springs back a lot less than brass does. This loosens the brass' grip on the bullet.

You are using jacketed bullets, so this SHOULD not be a problem, but it might be. It is a concern, usually, only with lead bullets and possibly plated, but not jacketed.

Load up a couple of dummy rounds without using the FCD. Use the third die without the seating stem to remove the flare (the third die is fully capable of applying a crimp if you just adjust it down). Do you chambering tests and measure OAL.

The brass, after the initial sizing by your decapping/sizing die should be smaller (inside diameter) than the bullet diameter. You flare just the case mouth so you can start a bullet. The seating die presses the bullet into the case, which is elastic and grips the bullet hard enough to prevent setback. You should be able to push on the nose of the bullet with about 50 pounds without it moving deeper into the case.

Brass, when it has been fired and reloaded many times, loses some of its elasticity and may not grip the bullet as tightly as when it was new. This can be cured by annealing, but if you anneal too much the brass becomes TOO soft and elastic. At the current price of brass, it is more reasonable for most of us to crush the offending cases and sell them to a metals recycler. They will be melted down and eventually find their way back to us as fresh cartridge cases, or boat fittings, etc.

Lost Sheep.

Fatelvis
March 30, 2013, 09:26 PM
Make sure your expander ball in your sizing die is clean, if it builds up with crud it will open up your cases to the point where there is less bullet grip/pull. You can slways chuck up the expander in a drill and polish it down a little and it will give your finished rounds more pull also. It also makes the passage of the ball through the brass smoother. Good luck -

david_r
March 30, 2013, 10:53 PM
here we go with the pistol expander balls again.

gamestalker
March 31, 2013, 06:15 AM
The first problem you have is misunderstanding the purpose of the crimp on a 9mm cartridge, or rimless cartridge as it were.
Allow me to explain as follows:

9mm and other same type cartridges head space off the case mouth, so over crimping significantly effects head space. What happens when one of these cases is over crimped, is the mouth gets pinched in the throat of the chamber. Because the mouth diameter is now smaller in diameter than the head space ridge in the chamber, the bullet becomes restricted, which delays or stops it from leaving the case / barrel, not a good condition. Also caused by over crimping is the firing pin impact will either be too shallow, or the FP impact gets cushioned, because the case is allowed to move forward into the chamber when struck by the FP.

Also, on these type cases, the taper crimp is not intended to produce neck tension, at all. And by over crimping, all you are doing is decreasing neck tension, the more crimp, the less neck tension. So when crimping these cases, only use as much crimp as is necessary to close the mouth belling used during seating, no more. I completely stopped belling and crimping all of my rimless pistol cartridges many years ago when using jacketed bullets. I simply put an even chamfer on the inside of the mouths, this provides the maximum degree of neck tension obtainable on these type cases.

For rimmed cases like 38 spcl, 44 mag. and so on, a roll crimped is used, and it is intended to hold the bullet. Those type cases head space off the rim.

I would pick up a good instructional reloading book and do some reading about what the crimps' job is on the various types of cases. This is critical information and can get you in trouble if not properly understood. There is more to crimping than what I've described here, while some cases rely on the crimp for increased neck tension, others do not utilize the crimp for neck tension all.

GS

tightgroup tiger
March 31, 2013, 08:14 AM
Sorry Spent case, I missed post 6, to many grandchildren jumping on me.

918v
March 31, 2013, 05:56 PM
Get an expander die that only flares the case mouth. Lee makes one for $15, called the Universal Expander cuz it works in all calibers.

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