problem with 9mm setback

[9miller]

Hey all, I'm in the midst of working up a load with 115gr xtp and unique using FC stamped brass and CCI 500 primers. I tested my chamber and the max OAL for this bullet is 1.14 so I seat to 1.135 and used a light crimp. I loaded a dummy round and upon chambering I am getting setback no matter how light or extremely excessive the crimp was. The first chambering dropped me to an OAL of 1.132 and after 5 chamberings it was reduced to 1.118, after ten down to 1.109. I checked my powder through expander die and it is only belling enough for the bullet.
These are set to a long OAL because I'm want to load up hot loads with 115gr bullets for summer carry for maximum expansion due to assailants not wearing as much clothes, and I have 124gr gold dots to arrive tomorrow to load for winter carry for more penetration during the colder months.
So my question is, does anyone know what could be causing the problem with the setback? I cannot have this as these loads will be at or around max data most likely and need to find a remedy. Thank you all for any help you can toss my way.

[Unclenick]

Pre-emptive strike: PLEASE DO NOT POST ON THE LEGAL ADVISABILITY OF HANDLOADS VERSES COMMERCIAL LOADS IN THIS THREAD. It has been done to DEATH on the forum. Everyone who reads this and wants to know the pro's and cons can simply search on the topic. Inevitably, and despite this request, somone will bring it up anyway. I am inclined to delete posts that bring it up. Stick to the technical side, PLEASE.

The cause of the setback is that the gun is smacking the bullet nose hard on feed. Check this out with a dummy round. You may find spots that can be smoothed up to reduce resistance.

If your crimp is truly solid, that setback may result in bulging the case underneath after awhile. You can tell by taking micrometer readings of the outside of the case. If that is not occurring, I suspect you are using a taper crimp. You may well need a roll crimp to prevent this, so you may need a different crimp die.

OTH: A hundredth of an inch of setback is perfectly acceptable from a pressure standpoint. The truth is that most pistol rounds with short powder spaces have their primers unseat the bullets before the powder gets burning fully. For power loads, using a slower powder than Unique will tend to encourage this happening, so the pressure, at that point, is not so directly related to seating depth as it would otherwise be.

Dip your bullets in brake or carburetor cleaner or other solvent to remove oil. Some makers leave a thin oil coating on bullets to prevent corrosion or tarnish. That makes it harder for friction of their hold by the case.

Cleaning your cases shiny on the inside with a rotary tumbler and steel pins will increase its surface friction with the copper, improving case grip.

Try getting some military brass (usually headstamp with maker initials plus two numbers to show year of manufacture). Military spec is 70:30 brass which is generally formed harder and has a more elasticity for bullet grip than the 80:20 low brass used by Federal.

[Swampman1]

Sounds like your COL is a bit long. I seat my 115 gr XTPs to 1.075 as per Hornady manual, and have no issues.

[9miller]

I was using the Lee FCD to crimp, and even crimped the dummy round so excessive to cause the bullet to have a groove from the crimp, that was just an experiment to see how much I needed but went to no prevail.

[MtnCreek]

IMHO, a roll crimp could reduce reliability of the ammo and should not be used, especially for carry ammo.

I use a very slight bell and only enough taper crimp to remove any bell. If you un-chamber daily, when you re-chamber place the cartridge into the chamber by hand, not through the mag.

[Unclenick]

I just added a few more thoughts to my first post. Sounds like your crimp is adequate.

It is also possible to weaken a crimp by overdoing it. The mechanism is the case mouth turns inward at a sharp enough angle that the brass just beneath it is lifted away from the surface of the bullet. Again, a micrometer will tell you. The brass over the bullet is wider just below the crimp than near the base of the bullet.

I need to add that since auto pistol round is supposed to headspace on the case mouth, the 9 mm crimped mouth is not normally supposed to be crimped narrower than 0.373". This is why a taper crimp is normal for these rounds. However, if you seat the bullet out far enough to headspace on the bullet (a round dropped into the barrel has the case head just flush with the back edge of the barrel extension), then roll crimping is OK. In the 50's and 60's it was a common practice among conventional pistol competitors shooting cast bullets who swore by it for producing maximum accuracy by increasing start pressure. It does shorten case life, however.

Edit: Forgot to add minus tolerance to mouth diameter; corrected above.

[g.willikers]

It might be the cases you are using.
Not all of them have the same thickness of material.
If yours are kind of thin walled, then the bullets could tend to be a little loose.
And as Unclenick has pointed out, the set back with the first chambering is not excessive.
It's the repeated chamberings that are aggravating the issue.
Not what ammo is supposed to experience.

[swmike]

You may want to make sure that the sizing die is still in contact with the shell holder when the ram is at the top of it's stroke. Many presses have some flex that will require some extra "pre-load" when adjusting the die.

The 9mm is a tapered case and unless it's pushed as far as possible into the sizing die then the case mouth isn't reduced in diameter enough to give enough neck tension.

Taper crimping isn't always the answer. When the crimp is applied the jacket is compressed along with the core material. The jacket can spring back slightly, leaving a void between the jacket and core. This can result in LESS neck tension under certain conditions.

Take a fired case and run it up into the sizing die. Then see if you can insert a thin feeler gauge between the die and shell holder. If you can, this is a starting point. Tighten the die and repeat to the point where you can't even see light between the surfaces. Some people will mix a little graphite in a thin oil (like 3-in-1), apply a thin amount to the bottom surface of the die where it should contact the shell holder, then size a case. When the case is removed there should be a black ring of oil marking the shell holder. If not, screw er down some more.

Also, make sure you aren't over flaring the case when you add the powder. Only enough at the case mouth to allow a flat based bullet to sit on the case with a very, very, small amount of case extending above the radius at the bullet base edge. The flare is only there to allow the bullet to enter the case and not shave lead or brass as it's seated. You want the pullet "PRESSED" in, not just "Slid" in and relying on the crimp to hold it.

[WESHOOT2]

1) use new sized cases ONLY for "SD" ammo

2) ensure your sizing die is juuust kissing the shellholder/plate

3) ensure your sizing die is resizing to proper dimensions

4) ensure, using accurate measuring devices, the diameter of your bullets (I use a ten-thou mike)

[44 AMP]

If you get the neck tension "right" you do not get setback, even with repeated chamberings.

But to get it right, you need the correct relationship between the bullet diameter, and inside neck diameter (actual, not nominal) when the bullet is seated.

Actual diameter of the bullet
Actual diameter of the case

Not what it should be/is listed as, but what it really is

I'm surprised that no one mentioned checking the diameter of your expander.

You mentioned checking it for how much flare it is giving the case mouth, and that a point as well, but the diameter of the lower part of the expander (which does the actual expansion of the case to hold the bullet after rezising) is important, too.

ALSO, what is the right combination of factors for a good tight fit can change with a different brand (or even lot#) of case, or bullet. And this assumes that all the cases or bullets in the batch you have are consistently the same actual size.

Everything made, even things made to a specific size (such as .355" diameter) may vary slightly from the listed spec. They can do this and still be within "standard" tolerances, or they might be outside the acceptable range, and still be in your hands to use, anyway.

[zeke]

.03 inch would not be bad for a low pressure practice round. It is not that easy to to eliminate all setback, or the factories could do it on a consistent basis. No semi auto rounds should be subjected to repeated chambering. The LFC can't be relied on to crimp so heavy as to eliminate setback.

1-at that col, how much of the bullets shank is outside the case? First possibility is to maximize the interference fit by seating the bullet deeper. Adjust your powder charge accordingly. Currently am seating 124 xtp's at 1.113, and there is still considerable shank outside the case. While a "plunk" test is important, so is feeding and other considerations, like setback in this instance.

2-Another possibility is to use a expanding plug that only produces a short bell, without expanding the case.

3-another option is to use a Lee undersize die, and not expand the case, just bell it. Lee's universal belling die is one die capable of this. However this may result in difficulty seating the bullet straight.

Currently am using the undersize die, lee expander and redding comp seater. Yes it is a lot of steps, but allows me to seat 115 fmj out closer to max length, and gives me confidence in hotter jhp rounds.

[WESHOOT2]

I have also used specialized compressed charges in 9x19 that fill the case so completely setback is virtually impossible.

[9miller]

Take a fired case and run it up into the sizing die. Then see if you can insert a thin feeler gauge between the die and shell holder. If you can, this is a starting point. Tighten the die and repeat to the point where you can't even see light between the surfaces.

Just able to get back to my press and tried this, voilà! I was able to insert an index card between the shellholder and die and tightened down accordingly. Made a dummy with 124gr gold dots and setback after 5 chamberings was a whopping .0025 inches, I can live with that. Only turned the crimp die adjuster in a half turn as well. Thank you all for your help in assisting me to create the best possible rounds for my carry gun that I can 110% trust mine and others lives to.

9miller