Causes for variable OAL in Dillon 550b press (9mm)

[DarkRayz]

I'm loading 9mm Luger, 124 gr Berry plated RN, 3.8 gr of Titegroup, at OAL of 1.125.

I had been doing 115 gr Berrys at 1.160 OAL with 5.0 gr of Unique.

When I went to the 124 gr Berry, I noted a bit of difficulty placing the bullet into the case mouth at the bullet-seating stage of the press. It didn't want to position well atop the case. I DO keep my fingers on it all the way as I raise the turret up to the die, just until the die envelopes the top of the bullet. So I dropped the die down ever so slightly to bell the case more at the second stage (powder drop stage) of the process, thinking it needed more of a bell to accept this longer bullet. And of course to get a shorter OAL I dropped the bullet-seating die down a hair also.

First, was this the right maneuver to address this issue? It did seem to make the case accept the bullet better...

Second, now I'm getting variable OAL as I run rounds through it. While many are in the 1.123-1.127 range, I'll get some from 1.111 up to 1.137, and I did NOT notice this variation when loading the other (above) rounds.

Thanks for the help

DR

[Dillonhelp]

When setting up the seat die, also have a fired case in station one to apply consistant upward pressure on the toolhead, the same as you will have when actually reloading. Doing this, the variation will be from bullet to bullet. Up to
.015" is typical for RN bullets, but I have measured up to .025" out of a hundred name brand projectiles.

[Unclenick]

DarkRayz,

I'm a little confused. Why did you want to shorten the OAL?

As to depth, if you know someone who has a lathe with a toolpost grinder you can get your powder drop tube re-contoured to give you a Lyman M dies type profile. That's what I do with mine. You want the rounded nose shorted to match the step, then the powder die has to be moved down a little to compensate. The result is it is much easier to seat bullets straight.



As to the irregularity, it is perhaps that the bullet is tipping until it catches on the edge of the seater or is running into dirt or lube build-up in the extremely short example. Also, make sure your seater isn't clogged up with lube or dirt. Just run a Q-tip wet with some mineral spirits up into it and wipe it around and see what comes out?

P.S. Don't overdo the length of the step or it will not get fully flattened by the taper crimp. Keep it short.

[DarkRayz]

Thanks for info.

I forgot to mention that I'm using once-fired cases that I've collected and they are from a variety of manufacturers, so might that have some influence?

I wanted to shorten the OAL a bit b/c I note that I'm at the long end of the range for 9mm Luger, according to what I'm seeing others load. And I wanted to see the effects on accuracy of a slightly shorter OAL, from 1.160 down to 1.150 and now to 1.125 inches.

Good to hear that this OAL variation that I'm finding isn't necessarily a sign of a problem in the press or my technique, but I had wondered about this 'tipping' of the bullet as I seat it. That's why my instructor months back said I should get into the habit of holding the bullet with my fingers as I raise it into the seating die so it wouldn't tilt. With the short 115 gr bullets it wasn't really a problem, but with the 124 grainers, holding it is almost necessary or it might fall off as I raise the case up!

I hesitate to make any permanent modifications to the components being so new to the art of reloading. I will keep a case on the first stage while testing my seat depth...that variation I mention was noted when I had only one case in the press at a time, so perhaps that's a factor there, thank you!

How can I tell if I'm crimping too little or too much, by the way?

DR

[Unclenick]

Plated bullets don't like much crimp or you crack the plating. Use your caliper to keep the case mouth within the specified 3.793"-3.800" range and you should be good to go.

[demigod]

You shouldn't need to hold the bullet in place all the way up into the die.

Are you getting enough belling at the case mouth?

Also, I've never had a "bullet tip" issue. I can set my bullets in quite crooked and the die straighens them out when it contacts the bullet's ogive. (I'm just running Dillon pistol die sets for 9mm and 45acp)

[jepp2]

"And I wanted to see the effects on accuracy of a slightly shorter OAL, from 1.160 down to 1.150 and now to 1.125 inches."

Are you adjusting your powder charge as you shorten the OAL? Depending upon your load, that could result in a significant increase in pressure.

[Unclenick]

Demigod,

Pick up several reloaded rounds. Take a look at the slight bulge in the brass where it comes up over the base of the bullet, then rotate the rounds. If that bulge is even all the way around, then your bullets are in straight. If not, if, for example, you see the bulge on one side but not the other, which is pretty common, they are slightly angled into the case. This is target shooter level of picky, looking to help keep a match gun within a couple of inches at 50 yards.

He is belling the cases just fine. Some bullet bases don't stay upright very well on the smooth convex radius of the bell.

[DarkRayz]

I have checked my primers for pressure signs, but at 3.8 gr of Titegroup at an OAL of 1.125 I'm still well within loading manual guidelines insofar as I can tell. another fellow CZ loader is using the same recipe and reports no pressure issues based on primer changes, also.

thanks for all the input. Seems like I'm more or less doing okay at this point.....

DR

[demigod]

I'll check that out, Unclenick.

I was reading my most recent issue of handloader magazine yesterday. And the pic of a correct belling (according to the author) was almost NO belling at all. He showed a case next to his idea of the correct belling and it looked maybe a little excessive... but that was his example of over belling.

The reason for the minimal belling was that it works the brass too much and can lead to splits in the cases. I can't remember EVER having a split case mouth on a semi auto pistol case...

[alfack]

I saw that article in HL. too. The authors idea of belling is no bell at all. That is just not correct. It may work for him, but does not jibe with Dillons' own manual.

I have checked my rounds for uneven bulges (concentricity), after seating them while they were crooked going into the die. They are even. I think it would depend largely on the shapes of the bullet and seating die, but mine straightens them out perfectly, if they go in a little crooked.

[demigod]

I saw that article in HL. too. The authors idea of belling is no bell at all. That is just not correct. It may work for him, but does not jibe with Dillons' own manual.

I agree. His belling looked like straight wall to me.

[alfack]

I agree. His belling looked like straight wall to me.

And his idea of excessive belling looked about right to me

[Unclenick]

It makes sense to minimize it, but you don't want to see the case mouth shaving metal off the bullet. As small as you can go without doing that will probably give the best brass life economy. A bevel base will line itself up a bit better in that circumstance than a square base.

How fast it work hardens and splits varies by brand. When I was loading a lot of .45 ACP for matches, I tracked one batch of brass through 50 reloads. It was Winchester, and about a third of it was lost to attrition (either split or unintended alms for the range gods) when I retired the batch because it had shortened about 0.025" by then and was starting to fail to cover the top lube groove on one of the bullets I used. These were very low pressure target loads put together on a Dillon Square Deal. Low pressure doesn't wear brass much.