Dillon 550b press descrepancy

[lilswede1]

The Dillon Progressive reloader seats the bullet between 001 - 004" deeper when using it as a single stage press then it does when using is progressively (shell in each of 4 stations).
Anyone else experience this and do you have an explanation?

 

[alinwa]

OK..... I've got a guess.

My guess is that you're being more consistent on your final stroke when loading singly. And that the priming stroke is out of the picture.

Try this..... single load some rounds but purposely mishandle the seating stroke. Go Hard and Soft and In Between and check for inconsistency.

NOW, do the same thing but stick a round into the priming station. My guess is that you're using fairly light neck tension and that there is a little flex in the press and that the upstroke of the priming ram is giving you a little play....


It's a guess...... might stir the juices anyway.


al

 

[Rustystud]

Dillon 550 Press

There is a cam action at the bottom of the stroke. Once the handle reached the true bottom of the stroke it has passed the top dead center. If you go past top dead center your stoke actually is begun to shorten. I found when I mounted my Dillon 550 the handle bar was actually touching my bench, I notched out the board so the handle could complete its stroke and completly bottom out, and adjusted my dies the stroke length problem went away. you might want to check and see if this may be an issue in your loading situation. I have done quite a bit of experimentation with both a 450B, 550, 650, and a 1050 Dillon press.. I have experimented with both floating dies, and floating shell holders. John Widden sells a floating die holder. I feel it is not needed if one uses a Dillon press as a single stage turrent press.

If your Dillon press is not completing it's stroke (going past top dead center) you will never have any consistency.

Good luck
Nat Lambeth

 

[Asa Yam]

The Dillon Progressive reloader seats the bullet between 001 - 004" deeper when using it as a single stage press then it does when using is progressively (shell in each of 4 stations).
Anyone else experience this and do you have an explanation?

Answer:

The shell plate "tips" differently, depending on how it is loaded. If you have a full length sizing die in Station 1, remove it. Sizing a fired casing requires a considerable amount of force. Do your sizing operations on a seperate pass - again, remember to load the shellplate evenly.

Powder charging can also result in an uneven loading condition. I think it isn't as bad as when you're also sizing, but the effect is still there.

If you want the same result all the time, either keep the shellplate full at all times - or only do one operation at a time.

• The first option gives you ~6 rounds (first and last few rounds) that unevenly load the plate. Segregate these if you choose, use 'em for barrel foulers or sighters.
• The second option gives you fairly uniform product - at a greatly reduced rate of production.

 

[lilswede1]

Phoned Dillon this AM

Described problem to expert and all he said was "only .001 - 004", man that is a tight unit".
The die holding plate is not a very tight fit so the variance on how much pressure it takes to resize a case will affect seating depth as the holding plate is pressed up and the shell holder pressed down.
He suggested using several drops of epoxy on the top part of the die plate where it slides into the machine but I think I will trying shimming up the underside to take out play.
He also let me know that unless I was shooting a BR rifle and was loading for competition the small variance in OAL would not be noticeable.
I know he is right but I keep reading consistency, consistency, consistency is the key to accuracy.
The 223 CZ 527 Bolt with 1-9 24" barrel has gone from a 1" factory group to a 1/4" reloaded group @ 100 yds. by adherring to the consistency thing.
If anyone has a different suggestion for tightening up the 550b I would really appreciate hearing about it.
Thanks guys.

 

[milanuk]

A few things to consider...

A simple thing to try would be what D. Tubb describes in one of his books... skip a station when inserting cases i.e. put a case in station #1, size it, rotate to station #2 for powder but *do not* put a new case in station #1, rotate it to station #3 (which has no die in it) and *now* put a case in station #1 for sizing, then rotate again so you have a case @ #2 (powder die) and at #4 (seater die) but nothing @ #1 and #3. The idea is to isolate the step that requires a lot of force and robs what little sensitivity the press has (sizing) from the more delicate steps (powder charging and bullet seating) that benefit from more feel and don't put much stress on the shell plate. It slows the overall rate down some, but may help with more consistent results.

Another thing that Tubb mentioned (I hesitate to say 'pioneered' as someone else may have came up with the idea, but I and many others first saw it in his book) was to 'float' the dies in the tool head by use of a locator pin btwn the tool head and the lock ring - the dies aren't screwed down tight to the tool head, but instead are allowed to float a bit in the 'slop' of the coarse 7/8-14tpi thread to find their own center. Modern machining is good and all, but the odds of all four holes having coplanar centers is minimal at best. John Whidden (a top-ranked NRA Prone shooter who also runs Whidden Gun Works) offers tool heads all set up with the necessary holes drilled, roll pins, modified Forster die lock rings, and a powder die w/ funnel for those of us who want to use a 550/650 but still weigh our charges first.

Finally... UniqueTek markets a couple goodies that help out as well. One is a replacement star wheel for the shell plate with a bearing plate installed - the idea being you can snug the die plate down a bit more but still be able to turn it. Not sure how much in terms of absolute measurements this actually helps, but in concept it makes sense. The other is their toolhead clamping kit: this is a set of drill bit, thread tap, and heli-coil insertion tool to take up the 'slop' in the toolhead-to-frame fit. The modifications are made to the aluminum toolhead, not to the press frame, and the kit comes with enough helicoils to do multiple tool heads (4-5, IIRC).

So... here's my story: I decided to try the Whidden tool head for my 6x47L tactical rifle. Everything was working fine, except I was getting between -0.004 to +0.006 variation in seating depth. If I was jumping the bullets 40-50 thou that'd be one thing, but I was seating +0.010 into the lands (even with magazine feed) so I wasn't too happy about that. I talked with John via email a bit, and he suggested getting the toolhead clamping kit. I'd previously considered and discarded the idea under the premise of if floating the dies was good, then floating the dies and toolhead must be better. On John's recommendation, I ordered the clamping kit, and set up a tool head with it. With all the dies back in the tool head, I now saw +/- 0.001 seating depth variation over 20 rds, with one exception (0.005) which was opposite a case that sized hard (wasn't using the skip-one strategy mentioned above). So from what I can see, between using the skip-one method, along with floated dies and a clamped tool head, you can reduce the variation considerably.

FWIW, I believe at some point this spring Whidden is planning on offering CNC machined tool heads with a tighter fit, and perhaps selling them through UniqueTek with the helicoils pre-installed. Win-win as far as I'm concerned

YMMV,

Monte

 

[SooStan]

I have seen it too. I added a second seating die in the forth station. It seems to have improved the consistency. I also always size a case while seating as this helps. I will try the skip a station method.

 

[mike in co]

depending on the actual type of match ammo being built, i use all four stations or just one. ammo is measured post production.

i have assembled 308win br ammo on this press.

yes, in four station, some ammo varies more then the rest(first and last 3).
when using it as a single, use only one slot on the shell holder...the same one...number or mark the slot. my match 308 shell plate is numbered 1 thru 4. i have 3 different 308(#1) shell plates.