I can't get enough head space for my M1A unless I screw the die an extra 1/4 turn to cam over the press. How does this change the head space? When you run the die down to the shell holder it's steel on steel, how does screwing the die so the press cams over allow the shell to go further into the die? ???
Camming over the press, how does this change headspace?
- Thread starter ChetS
- Start date
CHetS: If you need to get the die lower in the press you might want to consider taking some metal off the top of the shellholder, they are not all created equal, and some are thicker than others, even with the same manufacturer. I've had several of mine taken down by a friend with his surface grinder, .010" to .015" solved my problems. They are very hard so don't know if you could remove any metal by hand or not, never tried.
Some presses have a little flex in them. So if you preload the die with an extra 1/4-1/2 turn after it touches the shellholder with the ram fully raised it will compensate for this flex.
You can also increase the amount of sizing by doing as fdshuster suggests and take a few thou off the top of the shellholder. You can do this with emery cloth laid on a flat surface by taking the shellholder with the top facing the emery and rubbing it back and forth, keeping it level on the emery. Just be sure not to go too far.
You can also increase the amount of sizing by doing as fdshuster suggests and take a few thou off the top of the shellholder. You can do this with emery cloth laid on a flat surface by taking the shellholder with the top facing the emery and rubbing it back and forth, keeping it level on the emery. Just be sure not to go too far.
Kenny474: I'm personally not comfortable with over camming a press, even my RCBS Rockchucker, one of the older ones, made in the USA. Thought about doing it, but it's gotta be putting a lot of stress on the linkage, pins, etc., and I think simply removing some of the top surface from the shellholder will solve the problem. Just my opinion, and I know others have no second thoughts about over-camming. I have measured as many as 3 shellholders, all by the same manufacturer, same cartridge, and their thickness varied by as little as .008" to as much as .012", and that's why .015" usually works for me.
I agree with camming over the press. My press won't cam over actually. But if you screw the die in further shouldn't that prevent the press from camming over?
When I use my Lee Challenger I need to pre-load the dies with an extra 1/4 turn when FL sizing or the press will flex enough that the die doesn't contact the shell holder. I don't have that issue with my Lee cast iron press. It's actually why I bought the Classic cast.
When I use my Lee Challenger I need to pre-load the dies with an extra 1/4 turn when FL sizing or the press will flex enough that the die doesn't contact the shell holder. I don't have that issue with my Lee cast iron press. It's actually why I bought the Classic cast.
My view is that camming over puts less stress on the press and is less likely to size the case more than if you adjust the die so that the shell holder comes up hard against the die. If you go hard against the die, your strength is the limit as to how much stress you make. If you cam over the stress is limited by the flex of the press, and will be lower. If there is any advantage to cam over it would be that you push the case into the die twice instead of one.
Agree with the comment that the only real way to size more is to take material off the face of the shell holder. I believe some (RCBS?) sell shell holder sets that have incremental amounts trimmed off the shell holder face.
Agree with the comment that the only real way to size more is to take material off the face of the shell holder. I believe some (RCBS?) sell shell holder sets that have incremental amounts trimmed off the shell holder face.
Ron: The RCBS shellholder set has shellholders that are thicker/higher than "standard", as mentioned by Kenny474, so that would not solve the problem of not being able to lower the FL sizing die far enough. I'd like to see someone offer a set of shellholders that are thinner/lower than "standard", and let us make the decision(s) about which we want/need to use. All of this proves the nonsense of the die manufacturers "directions" that the die be screwed down 'til it touches the top of the shellholder, then backed off a quarter or half, or whatever amount. Using that method does nothing to control the very important headspace length/dimension. 
if you talk to the techs at Redding they will tell you their presses are designed to cam over, in fact screwing the die down hard onto the shellholder without camming over can strech the brass and make it longer as you are squashing the case in at the shoulder junction, buy a headspace measuring tool and have a play around with die positioning and you will be amazed at what your brass is actually doing after f/l sizing, I bought the larry willis inovative technologies headspace gauge, it has transformed the way I size my brass and I can now consistently knock the shoulder back 1 thou for my bolt guns and get perfect headspace on fired brass.
NorCalMikie
Gold $$ Contributor
Take 2 or 3 shell holders and chuck them upside down in a drill press. Run them down on a "well oiled" sharpening stone. Measure before and after so you'll know how much you take off. Remove as much or as little as you want. That way you've got a selection of shell holders to work with.
And like UK says: The press "is" made to cam over!
A "very slight" cam over is where you want to be.
Make all your adjustments from "that" position.
And like UK says: The press "is" made to cam over!
A "very slight" cam over is where you want to be.
Make all your adjustments from "that" position.
Chet,
How does this change the head space?
When you run the die down to the shell holder it's steel on steel, how does
screwing the die so the press cams over allow the shell to go further into the die?
I think that touching the shell holder and touching the lands are much alike, i.e. everyone has a different opinion on what is touching. To answer your question:
1. All presses have some flex. Some just flex more that others.
2. Most on this board are using large presses with enormous mechanical advantage and don’t realize how much force, pressure, or energy it actually takes to resize cases. 308 cases out of a gas gun will normally require a little more than others.
3. If the press flexes a few thousands under load than your shell holder is no longer touching the die when the ram is at its top position. So when you set the die to a cam over position at the start, you are just making sure that the die will still be touching under the load required when resizing. Most shell holders are designed so there is a 1/8” or .125” gap between the top of the shell holder and the flat area the base of the cartridge case will rest on. Also most full sizing dies are designed so when used with most shell holders and touching the shell holder at full ram up position (touching under load) will resize the case a few thousands under the go gage dimension.
Here is something for you to try or look at. Take your resizing die and loose the locking nut. Screw the die down until it just touches the shell holder when it’s in the full up position. Now tighten it as hard as you can by hand. Tightening the die by hand is only removing the slop in the press linkage. For every five degrees you turned the die by hand tightening it equals one thousand of an inch.
NOTE - Some shell holders might be actually held up a few thousands by the shell holder retaining clip and this hand tightening should remove that slop.
All cases are a little different and will require a different amount of force to resize. It is brass and brass happens. Each time you resize the force to resize changes some. The best way to account for these changes and differences I feel is a good preload or over cam on the resizing die. Enough over cam to be sure that EVERY time you resize a case the resizing die is touching the shell holder under load at the top of the rams stroke. Just oil and grease the linkage.
I like to preload the sizing die by ether tightening it down hard on the shell holder with channel lock piers and then tighten the locking ring or just screw it down some and test the over cam amount by raising the ram. Again tightening the die locking ring when the die is under the over cam pressure. I feel that this helps square the to the shell holder.
If you start using this type of procedure when setting up your resizing die, you should find that you are actually over resizing the cases. This is where the Redding Competition Shell Holder come it. You can use a plus shell holder and enough preload on the resizing die or over cam that completely removes any linkage slop, press flexing, and case resizing force variation. I have found that this type of resizing die set up using the Redding Competition Shell Holders greatly reduced my resized case head space variation. It also makes repeated resizing die set ups a breeze, just keep a record of which plus shell holder to use with each cartridge-gun combination. The set up is repeatable without any trial and error.
Note – This is not recommended for carbide pistol resizing dies. Preloading a carbide die could cause it to crack.
How does this change the head space?
When you run the die down to the shell holder it's steel on steel, how does
screwing the die so the press cams over allow the shell to go further into the die?
I think that touching the shell holder and touching the lands are much alike, i.e. everyone has a different opinion on what is touching. To answer your question:
1. All presses have some flex. Some just flex more that others.
2. Most on this board are using large presses with enormous mechanical advantage and don’t realize how much force, pressure, or energy it actually takes to resize cases. 308 cases out of a gas gun will normally require a little more than others.
3. If the press flexes a few thousands under load than your shell holder is no longer touching the die when the ram is at its top position. So when you set the die to a cam over position at the start, you are just making sure that the die will still be touching under the load required when resizing. Most shell holders are designed so there is a 1/8” or .125” gap between the top of the shell holder and the flat area the base of the cartridge case will rest on. Also most full sizing dies are designed so when used with most shell holders and touching the shell holder at full ram up position (touching under load) will resize the case a few thousands under the go gage dimension.
Here is something for you to try or look at. Take your resizing die and loose the locking nut. Screw the die down until it just touches the shell holder when it’s in the full up position. Now tighten it as hard as you can by hand. Tightening the die by hand is only removing the slop in the press linkage. For every five degrees you turned the die by hand tightening it equals one thousand of an inch.
NOTE - Some shell holders might be actually held up a few thousands by the shell holder retaining clip and this hand tightening should remove that slop.
All cases are a little different and will require a different amount of force to resize. It is brass and brass happens. Each time you resize the force to resize changes some. The best way to account for these changes and differences I feel is a good preload or over cam on the resizing die. Enough over cam to be sure that EVERY time you resize a case the resizing die is touching the shell holder under load at the top of the rams stroke. Just oil and grease the linkage.
I like to preload the sizing die by ether tightening it down hard on the shell holder with channel lock piers and then tighten the locking ring or just screw it down some and test the over cam amount by raising the ram. Again tightening the die locking ring when the die is under the over cam pressure. I feel that this helps square the to the shell holder.
If you start using this type of procedure when setting up your resizing die, you should find that you are actually over resizing the cases. This is where the Redding Competition Shell Holder come it. You can use a plus shell holder and enough preload on the resizing die or over cam that completely removes any linkage slop, press flexing, and case resizing force variation. I have found that this type of resizing die set up using the Redding Competition Shell Holders greatly reduced my resized case head space variation. It also makes repeated resizing die set ups a breeze, just keep a record of which plus shell holder to use with each cartridge-gun combination. The set up is repeatable without any trial and error.
Note – This is not recommended for carbide pistol resizing dies. Preloading a carbide die could cause it to crack.
I put a Lee Collet neck die in a Rockchucker press, did not follow the die adjustment instructions, and set the die to just cam over with 100 pounds of force at the handle knob.
That broke the Rockchucker ~ 2004.
I sent the parts back to RCBS and they sent me an entire new Rockchucker press.
A year or two later they beefed up the press design.
The way to think about camming over is that, at top dead center, the internal forces in the press are infinite, minus friction.
That broke the Rockchucker ~ 2004.
I sent the parts back to RCBS and they sent me an entire new Rockchucker press.
A year or two later they beefed up the press design.
The way to think about camming over is that, at top dead center, the internal forces in the press are infinite, minus friction.
Shynloco
You can lead a horse to water, but ........
Chet,
I believe CJ6 has the answer. Go get yourself a set of Redding Competition Shell Holders to eliminate the need for "cam-over" by screwing in the Die beyond regular setting. The shellholders (they come in a set of 5- .002, .004. .006, .009, .010) are already "shaved" at .002 increments that eliminate the need for further adjustment. I use my Redding Shellholders on my 22-250 (and several other calibers) primarily to bump the shoulder of the casings due to headspace issues. I know zero about your particular weapon when it comes to it's headpsace, so you might check and see if any of your buddies have a set of those Redding Competition Shellholders and try it out. A set usually runs around $44. Good luck!
I believe CJ6 has the answer. Go get yourself a set of Redding Competition Shell Holders to eliminate the need for "cam-over" by screwing in the Die beyond regular setting. The shellholders (they come in a set of 5- .002, .004. .006, .009, .010) are already "shaved" at .002 increments that eliminate the need for further adjustment. I use my Redding Shellholders on my 22-250 (and several other calibers) primarily to bump the shoulder of the casings due to headspace issues. I know zero about your particular weapon when it comes to it's headpsace, so you might check and see if any of your buddies have a set of those Redding Competition Shellholders and try it out. A set usually runs around $44. Good luck!
Shynloco said:
From the Redding site:The new Redding Competition Shellholders are packaged in five piece sets in .002” increments (+.002”, +.004”. +.006”, +.008” and +.010”). Each shellholder has a distinct black oxide finish and is clearly marked to indicate the amount it will decrease case-to-chamber headspace.
They are thicker and designed to create a tighter case to chamber fit. They would need to increase the headspace to size the case shorter, which is what the OP needs.
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