Rock Chucker Variability - Is This Normal or Not?

Discussion in 'Reloading Forum (All Calibers)' started by CarlGeorge, Mar 22, 2020.

  1. CarlGeorge

    CarlGeorge Gold $$ Contributor

    Joined:
    Nov 15, 2017
    Messages:
    103
    I have a Rock Chucker that is on the order of 20 yrs old. I bought it used when I got into reloading about 5 1/2 years ago.

    When I first started I was loading "mainstream plinking ammo": 9mm, .223, .38 Spcl, etc. Over the last 2-3 years I started dabbling with higher precision stuff (first with a stock Rem 700 in .243) and now I have a Kelbly/Brux in straight .284.

    As I started paying more attention to jump, CBTO measurements, etc. I noticed I could change seating depth by up to .003-.004 based on how hard I pressed on the press handle after it was bottomed out. I've lived with it - and haven't considered it a big deal. At this point I was using standard RCBS .243 dies with the threaded seating stem rod.) Most recently with the .284 when I seat bullets (Redding Competition die) I've set it up so I just gently let the press handle bottom out. And this provides good repeatability.

    This morning I was trying to figure out why I was getting variability in my sizing operations. Shoulders were being bumped up to .001-.003" more than i wanted in some cases. Then I recalled my bullet seating experiences. I tried sizing while focusing on not pressing down on the handle after the handle initially bottomed out. Doing that resulted in sized cases coming out MUCH more consistently.

    Is this extra ram movement based on handle pressure common in presses like a Rock Chucker? Overall I'm pretty much getting the results I want to have. Between that, and knowing this situation exists, I can very much live with it for the time being. I guess in the larger view I'm wondering if I should start thinking long term about replacing this press.

    Thanks!

    CG
     
    Last edited: Mar 22, 2020
  2. shoot4fun

    shoot4fun Gold $$ Contributor

    Joined:
    Feb 13, 2005
    Messages:
    1,744
    Are you setting the dies up per the manufacturer instructions? If so, you are making a huge mistake and setting up all sorts of issues.
     
    jepp2, Mad_Charlie and bozo699 like this.
  3. CarlGeorge

    CarlGeorge Gold $$ Contributor

    Joined:
    Nov 15, 2017
    Messages:
    103
    Well - generally I'd say "no". I'm not setting up to do the cam-over if that's what you're referring to. My desire has been to do a .002 shoulder bump, and the variability I described means shoulders were coming out of the die being bumped anywhere from .002-.005.

    Is that what you're getting at?
     
  4. Ralph Littlefield

    Ralph Littlefield

    Joined:
    Dec 28, 2019
    Messages:
    105

    Please elaborate.
     
  5. Mikemci

    Mikemci Gold $$ Contributor

    Joined:
    Dec 3, 2016
    Messages:
    446
    Harrel's press, Whidden FL sizing die, Wilson chamber seating die, Bart's bullets and arbor press. Your problems will disappear.
     
    justpassinthru likes this.
  6. 1badgoat

    1badgoat Gold $$ Contributor

    Joined:
    May 4, 2016
    Messages:
    144
    Perhaps you should try setting your dies for some cam over and use the redding competition shell holders to get the appropriate shoulder bump.

    Works well for me.
     
    Texas10, dmoran, dantiff2 and 4 others like this.
  7. dgeesaman

    dgeesaman Gold $$ Contributor

    Joined:
    Sep 3, 2017
    Messages:
    739
    I run my rockchucker handle the full length of its travel for both sizing and seating. I can keep shoulder bump within .001. Seating depth has more variables but I can hold within .004 total using the RC press. (I hold within .002 total now using arbor press and custom bullets).

    When sizing, do you pause for a couple of seconds at the top? That seems to help. Also what bullets are you using?
     
    WyleWD likes this.
  8. CarlGeorge

    CarlGeorge Gold $$ Contributor

    Joined:
    Nov 15, 2017
    Messages:
    103
    For bullet seating everything (now - .284) is going great. Using the Redding Competition Seating Die, along with the handle methods I describe, I get the seating depth I want basically 100% of the time. I'm using Berger 180gr Hybrid Target bullets.

    For sizing I'm using full travel of the press handle. But imagine that point where the case is fully in the die and the press handle is all the way down. If I put additional force on the press handle after it's in the full-down position, I believe I'm getting an additional up to .003 or so of additional ram travel.

    It's this additional "flex" or "ram travel" or whatever I'm trying to figure out is within the realm of normal for a press like a Rock Chucker.

    I'll restate something from the original post: For now I understand this behavior and I'm able to work with this behavior and create the ammo I want. I know how to use the press to improve consistency and reduce substantially the variability. I'm curious if this variability is normal or abnormal......leading to an understanding if this press is heading south in some way.

    Thanks.
     
  9. Gina1

    Gina1

    Joined:
    May 28, 2011
    Messages:
    760
    I've have used my Rock Chucker for 10 years. Last year I noticed a small amount of play in the ram at the top of the stroke. (sort of a slight rotation).
    I took the ram out and found that the ram hole, where the shaft goes through it was worn out (slightly concave) and correspondingly the shaft had a similar
    wear pattern. Called RCBS, talked over the problem and they sent me a replacement ram and shaft. NO CHARGE !!Lets hear it for RCBS.
    Problem fixed.
     
  10. rsmithsr50

    rsmithsr50

    Joined:
    Oct 29, 2019
    Messages:
    968
    you need to fix both of those
     
  11. Uncle Ed

    Uncle Ed

    Joined:
    Aug 1, 2018
    Messages:
    918
    I bought my Rockchucker press in 1973 and the linkage and pivot pins are worn and there is slop in the linkage.

    I use the Redding competition shell holders that allow my dies to make hard contact with the shell holder with press cam over. This removes any slop in the linkage at cam over and more uniformity in shoulder bump.

    I use Forster benchrest seating dies and do not notice any seating variations.
     
    ebb and dogdude like this.
  12. shoot4fun

    shoot4fun Gold $$ Contributor

    Joined:
    Feb 13, 2005
    Messages:
    1,744
    Yes that is what I was getting at. Times, technology and terminology has changed tremendously since I started this reloading thing over 40 years ago.
    BTW @Gina1 has some good advice. I've never been left wanting for anything after a call to RCBS. Over the years they have taken care of any issue I've called them with and even things that my dumb butt broke by misusing their tools.

    Bullet seating variables are many. They include inconsistent neck tension, bullet quality, etc.
    As for shoulder bump, inconsistencies can come from a loose die, poor lubrication of the case and from spring back due to poor or lack of annealing. The reasons you are getting what you're getting can and likely do come from many other issues before you put your Rock Chucker to blame.
     
    kneedtospeed, grovey, rogn and 2 others like this.
  13. bozo699

    bozo699 Gold $$ Contributor

    Joined:
    Mar 2, 2010
    Messages:
    5,625
    The factory instructions are a joke! Turn sizing die in until it hits shell holder the go another half turn!?...... What kinda precision shoulder bump would that get ya? Depending on the die and shell holder you might be getting huge amount of shoulder bump or may be getting none at all!... complete joke!...
    Wayne
     
    kneedtospeed and jepp2 like this.
  14. Don

    Don Gold $$ Contributor

    Joined:
    May 24, 2007
    Messages:
    1,641
    Good Read .
    Having had my Rock Chucker for 30 + years ,time to investigate ? I have other press also.
    It has Loaded 2000 to 3000 Rounds a year for a Long Time. It is my go to for Sizing ?
     
  15. daleboy

    daleboy Gold $$ Contributor

    Joined:
    Mar 27, 2017
    Messages:
    1,915
    Yup,if he just happens to have them sitting around somewhere.
     
    Gary in MD likes this.
  16. daleboy

    daleboy Gold $$ Contributor

    Joined:
    Mar 27, 2017
    Messages:
    1,915
    I would look at the Rock Chucker last .
     
  17. CarlGeorge

    CarlGeorge Gold $$ Contributor

    Joined:
    Nov 15, 2017
    Messages:
    103
    I take the input that a variety of variables can influence inconsistent bullet seating and sizing operations. (Per the points made by @shoot4fun in response #12 above.) Those other things as influencing variables make sense to me.

    However if:
    • For bullet seating operations, bullet seating depths change *only* based on putting no vs additional force on press handle and
    • Shoulder bumps change based *only* on putting no vs additional force on the press handle
    Does that not isolate the variance being the press? In the scenarios described in the above two bullets, the only variable changing results is press handle pressure applied *after* the press handle has initially bottomed out. (i.e. I'm describing scenarios above where bullet seating and shoulder bump are consistent when the handle is bottomed out only. And different bullet seating and shoulder bump results are seen when the handle is bottomed out but then pushed on with additional force.)

    To me, since these inconsistencies are seen in both seating and sizing operations, the variations are consistent, and they're based on press handle pressure or lack thereof, that seems to point to the press as the root cause.
     
    Last edited: Mar 23, 2020
  18. jonbearman

    jonbearman I live in new york state,how unfortunate ! Gold $$ Contributor

    Joined:
    Jan 3, 2010
    Messages:
    8,764
    I have a rockchucker that is 45 years old at least. I can load to my hearts content. In fact I have over the years. I have loaded so many rounds I couldn't put a number on it but conservatively 30,000 rounds at least. I have recently decapped somewhere right around 20,000 cases and sized half that much. These problems are weird to me. when I seat I can do it with one finger in annealed cases. Take it apart and clean it real well and grease it on all wear points and see how she does.
     
    Outrider27 likes this.
  19. Shaggy357

    Shaggy357

    Joined:
    Dec 21, 2015
    Messages:
    428
    Reloading needs to be done with a rhythm. Like dancing, make a false step and stub your toe. I shoot a lot of different stuff. One of the things that I have found to be helpful is setting up one set of dies, for one press, with one shell holder, etc. Set your dies for your gun and your chamber. Check and double check. When things feel out of rhythm ask yourself why.

    Springback in the brass can effect the amount of shoulder sized. Keeping the rhythm and keeping the brass uniform (length, anneal, and other prep) will help reduce variability.
     
  20. justpassinthru

    justpassinthru Silver $$ Contributor

    Joined:
    Jan 26, 2014
    Messages:
    187
    I had a Rockchucker that I bought new back in the 70's. Last time I had it apart for cleaning and lube I noticed so much flop in the ram that I could wiggle it back and forth and hear clunk clunk.
    A local Walmart keeps a few reloading supplies so I went there and looked at a new Rockchucker which seemed fine to me and it had 0 flop in the ram. Anyway, I brought it home and sent my old one back to RCBS. The guy I spoke with said I would most likely be sent a new press. So far I really like the new one, and guess I'll have two now. Time will tell but most likely they will outlast me.
    Did I screw up?
     
    New Gun likes this.

Share This Page