COL inconsistent with Dillon 550 and Lee Dies

[TargetTerror]

I reloaded 100 rounds of 38 special this afternoon on my Dillon 550, with Lee Dies. The COL varied throughout the entire batch by +-.05 inches. I'm using the Lee seater die backed out so that all the crimping is done by the Lee crimp die. Bullets were Zero 125 gr JSP.

I've also had a problem on the same press with 9mm (Lee dies as well). COL will slowly creep up, and I'll end with a longer COL than I started with. Its done this with various bullets.

So, 1. Why would it be doing this? 2. Should I care? I know pressure can change dramatically with changes in COL with 9mm, but would this really matter with 38 special?

 

[Steve C]

Don't worry about it. There's lots of room in the .38 spl case. You can expect some lack of consistency with a automatic press as there is built in looseness to allow the parts to turn and rotate. All that rattling around of parts movement tend to make things move a bit too. Changes in OAL could be caused by lack of uniformity in the bullets or build up of dirt, lead and lubricant on the seating stem face when using soft point, jhp, plain lead or cast bullets.

 

[SASS#23149]

+1 for what Steve C said.
I gave up trying to hold perfect oal's with my dillon a long time ago.A benchrest shooter would go nutz at such a statemtn,but a tin can shooter like myself can still hit the tin cans,so I"m .

 

[HRT]

Often times part of the problem can be attributed to slightly different ogives from one bullet to the next. The bullet seldom fully seats in the bullet seating punch but bears somewhere on a fixed diameter. SO if the ogive is different, even just a bit, it hits the punch differently and seats to a different length. If I recall Lee can provide a different seating punch if you ask.

 

[Sunray]

1. The cases are different lengths and/or the seating plug is loose. Case length is far more important with the 9mm.
2. Different COL is deterimental to accuracy, but not unsafe.

 

[TargetTerror]

The cases are different lengths and/or the seating plug is loose. Case length is far more important with the 9mm.

I don't think that anything is loose in my rig, but i'm sure the cases are different lengths as this is range brass that I don't bother to trim. How would the different lengths affect the seating?

One other thing I forgot to mention. I originally used these in a Lee Hand Press, and the COL was consistent (definitely with the 38 special, and I don't recall for the 9mm).

 

[jmorris]

If you really meant .050” then you’ve definitely got a problem. You could get closer than that with your eyeball. If you meant .005” then you are only +-.0025 from your OAL and that’s not too shabby for the speed advantage of a progressive press. I have found on progressives you need to have them full, the first and last rounds will be slightly different than ones made with the shell plate full. It’s a tolerance stack of shell plate, die holder, bullet shape, brass thickness, length & tension, primer depth (if you didn’t seat it all the way) and the linkage of the machine + the guy pulling and pushing on the lever. If all of that added up gets you within .0025 you are doing great. But if you’re really off by more than a spark plug gap (.050) you do need to figure that one out.

 

[Car Knocker]

The cases are different lengths

Normal case length variation will not affect OAL of the cartridges. Length is determined by the relationship of the shellholder at top of stroke and the die setting.

I have noted that variation in speed of press operation may cause some small variation in COL. I have also noted that mixed brass and the difference in wall thickness and thus seating resistance may result in some small variations - thinner walls seem to allow the bullet to seat deeper, faster. I tend to pause a moment at the top of the stroke (ram all the way up) to compensate. Many, if not all, progressive press manufacturers recommend that OAL be set when all stations have a case in them. I suspect that a thin-wall case in the sizing position vs a thick-wall case in that position may allow a slight difference in OAL. I certainly can feel the difference in resistance.

Dings in the lead nose of those JSP bullets may allow some slight variation if using a flat seating stem.

EDIT: I seem to recall a couple of posts that stated the use of the Lee FCD resulted in a change of OAL (from the seated length to the crimped length) at times but I don't recall what the circumstances were.

One last thing - can you verify that the variation is on the order of 0.05" rather than 0.005"?

 

[shadowalker]

I was having variation of .004 with Lee dies in 40 S&W, replaced the dies with RCBS and the problem went away, I'm not sure if the seater just didn't like the bullets (165 FP Rainer / Berry / Hornady XTP) or if you just get what you pay for .

I do still use the Lee FCD because measuring before and after FCD has never shown an OAL variance.

 

[RustyFN]

I load 9mm and 223 with Lee dies and have never had a problem with OAL. The farthest anything has been off is .003. I just bought a set of 38/357 dies but haven't used them yet.
Rusty

 

[ranger335v]

I don't see how a seating die would be able to affect OAL. I do see how the "springyness" of a press, especially a turret or progressive press, could do it.

 

[Outlaws]

My 550 will seat bullets about .003-004 less than what I set the seating die for when the loading is in full swing. That is, one round in the press at a time seats further down (shorter OAL) than 4 rounds going at once.

.050 is a huge difference. I would say something else is messed up. Email Dillon about the problem, they might have come across it at some point in time.

 

[wally]

Measure them after the seating and before the FCD. How much the FCD die squeezes depends on the brass thickness which varies. When the diameter is reduced the material has to go somewhere so the OAL changes.

If they are different out of the seating die, as was said look for a loose seater plug or wax/fouling buildup in the seater die -- particularly important if reloading hard cast lead bullets because as the wax builds up the OAL gets shorter.

--wally.

 

[fineredmist]

Give this a try it might help, disassemble the Lee seating die and clean it throughly, when you reassemble put a few turns of teflon tape around the threads of the seat adjuster and that will take out any movement. Next give the locking about 1/2 turn down and put some Blue Locktite on the threads and return it to the original position. Let the Locktite setup, reinstall the die and tighten with a wrench. You have now removed any sloppiness in the die and it should work properly.
The rubber "O" ring on the die must be compressed or it will permit movement when the round is seated.
This has worked well for me and it should work for you.

 

[TargetTerror]

You guys were right. I definitely meant .005 instead of .050" There is a reason I leave math to others

I loaded up some 38 special wadcutters today. I was able to maintain a virtually constant OAL. I suspect that the problem is to slight variations in the 125 gr JSPs.

I'll keep poking aroudn with the 9mm.

 

[Bronson7]

.005 is very good. Nothing to sneer at. Shoot'm up.
Bronson7