Rock Chucker Variability - Is This Normal or Not?

[WyleWD]

Well - I spent much of the afternoon disassembling, cleaning, lubing, and reassembling the press. I will say it is REALLY REALLY smooth now!
CG

When you talked to RCBS, did they tell you specifically what to lube the ram with?? Just curious. WD

 

[Webster]

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

If the die is touching the shell holder you cannot push the case in deeper. If the die is adjusted off the shell holder to get the shoulder bump you want then the limit to how far the case gets pushed into the die has to be related to the press linkage or die movement in the threads? The frame is strong enough you shouldn't be able to bend it. Don't understand how pushing to hard bends something in the press or you get more movement due to clearances in the lever mechanism to allow the case to get pushed in more? If there is wear or loose fit in linkage parts it is the same each time you move the lever? More than likely the variation in bump is caused because each case has a slightly different hardness and springiness and you are measuring to 0.001-0.003" differences. What's the differences for bullet to ogive length? Every case and bullet has variation. I never measured variation in bump or BTO and I get small groups.

 

[CarlGeorge]

When you talked to RCBS, did they tell you specifically what to lube the ram with?? Just curious. WD

No they didn't. (I might have gotten more info - or more info might have come out in conversation - if the interaction had been on the phone. But they were (are?) only taking email Customer Service requests at this time.)

For other folks that have offered perspectives: I don't know why a good cleaning has improved the situation (it is still susceptible to having movement with increased handle pressure), but it has gotten better. Most importantly, IMHO, I now understand it and I can work with it. (Most notably.....by being very consistent in how I finish the press handle stroke.) And I'll replace the parts at some point. I've certainly got enough time on my hands. LOL

CG

 

[DaveTooley]

I haven't read the entire thread but variations in the amount of lube and varying the speed of the stroke will cause different case lengths. Ask any bullet maker about the importance of consistency. Also all presses have some spring in them.

 

[danny]

When seating bullets on your old Rockchucker use the method below.

When the duct tape rips and the string breaks the bullet is fully seated.

It looks like something built by Red Green

Danny

 

[bozo699]

It looks like something built by Red Green

Danny

Or maybe Fguffy..... lol
Wayne

 

[Uncle Ed]

Actually it a old photo from this forum when someone here said he attached a torque wrench to his press to get uniform pressure with his Lee Collet die.

I posted the photo and said "The string and duct tape keeps ripping, so what do I do now?"