Controlling Shoulder Bump with a CO-AX

[Herd_Bull]

I’m trying to shoulder bump 7mm rem mag cases back .0015 to .002 using a CO-AX press and FL Forster die. Is there a better way to find the perfect die setting for the .0015 to .002 bump rather than messing around with a ton of trial and error screwing the die in and out? I’m tired of going little by little in with the die only to find that I then over bump the should and have to fire form the case again and start over. I’m reloading for more than one rifle here with 1 die so I really can’t just set it and forget it since it changes between rifles.

I love the idea of Redding’s comp shell holders for controlling that last few thousands for the perfect bump, but they won’t work with the S jaws on my press. There must be a more accurate, more effective, and more efficient way to do this than I’m using...???

 

[22DASHER]

Get yourself some die shims. Set your die up with a couple thousands shim under it giving yourself .002" shoulder bump in the rifle with the shortest headspace. Then add die shims to get the desired bump in the next rifle. Write down the details and put in a die box. Problem solved. Also the reason why I put a small shim under initially is just incase you need a little extra bump for some reason down the road.

 

[ireload2]

Just buy multiple sizing dies and set each one for each rifle unless you have 10 of the same caliber. Then you might get lucky and find that some are the same length.

 

[ballison]

This will let you use shell holders on a Co-Ax press. Just an option.

http://www.midwayusa.com/product/144115/forster-co-ax-single-stage-press-shellholder-adapter-plate

 

[coford]

You will drive yourself crazy trying to get it right with any press until you anneal your cases. It seems that cases that are not annealed size differently and spring back differently. I could never keep things as consistent as I wanted until I started annealing. I would do just as you say: adjust, adjust, adjust, think I have it perfect and then I would over bump. I used both my Co-ax and my Rock Crusher. After annealing my results are near perfect.

 

[Herd_Bull]

Thanks for the replies.

22DASHER - Die shims don't work well with a CO-AX. I have never tried them but they would have to go below the lock ring and I'm not sure how well that would work. If it was a screw in die press like a RC, I would have them already.

FTRinPA - I have one of those but haven't tried it yet. I don't want to loose the floating CO-AX stype and then always have to swtich back and forth between shell holder for decapping, sizing, and seating.

ireload2 - I though about that... might be the best option.

Gonzos - I am driving myself crazy!

 

[hotrodlouie]

If you have dial cali. that has a depth rod on the end you can measure off the die to the lock ring and adjust lock ring in thousands until you get the dimension you are looking for.

 

[Dusty Stevens]

You may find it easier to get a regular type press to do these type operations

 

[savagedasher]

We all use co-ax press without out any problem . But we had tight head space and the die had to be short . The cases must be the same hardness. Like with any press. Larry

 

[Dusty Stevens]

You dont use shims on your dies for multiple rifles like hes trying to do tho

 

[ericbc7]

I don't use die shims with my Co-Ax, but it seems clear that the shims would have to go Above the lock ring to change the bump.

 

[ireload2]

If you are having to chase a setting try cycling the press 2 to 4 times while rotating the case between each cycle.
Let the press dwell at the full stroke from 3 to 5 seconds each time so the brass has time to take a set.
I know it sounds involved and tedious but variations in the amount of lube, case hardness and speed of sizing can make your case length from head to shoulder vary about .002. Once you size the case multiple times you will get the same length every time. Without a tool to measure your head to datum length you cannot see the small variations.

Thanks for the replies.

22DASHER - Die shims don't work well with a CO-AX. I have never tried them but they would have to go below the lock ring and I'm not sure how well that would work. If it was a screw in die press like a RC, I would have them already.

FTRinPA - I have one of those but haven't tried it yet. I don't want to loose the floating CO-AX stype and then always have to swtich back and forth between shell holder for decapping, sizing, and seating.

ireload2 - I though about that... might be the best option.

Gonzos - I am driving myself crazy!

 

[hoz53]

If you are having to chase a setting try cycling the press 2 to 4 times while rotating the case between each cycle.
Let the press dwell at the full stroke from 3 to 5 seconds each time so the brass has time to take a set.
I know it sounds involved and tedious but variations in the amount of lube, case hardness and speed of sizing can make your case length from head to shoulder vary about .002. Once you size the case multiple times you will get the same length every time. Without a tool to measure your head to datum length you cannot see the small variations.

Die shims used in a coax would have to go above the lock nut and I just measured the slot in mine. There is very little room for die shims in there. I'd never try to use one sizing die in a coax for multiple rifles. It's difficult enough getting them adjusted for one gun. I mark the die and locknut to give myself a reference when doing this adjusting. Like has been said if I wanted to use one sizer die for multiple rifles I would use the screw in type press and shims.

 

[Herd_Bull]

Thanks guys. Interesting enough, I'm getting about 2 to 3 (.002 to .003) thousandths in shoulder bump variation when using a FL die on once fired brass. The 3 thousandths is about one in every 15 cases so the 1 to 2 thousandths is more common. Is this variation common?

 

[shoot4fun]

Not getting any variation in shoulder bump with my Co-Ax but I do anneal.

 

[BoydAllen]

A friend had the variation issue that you are seeing, we attributed it to variations in factory annealing. He bought a two torch annealing machine, and we did a careful setup using the consistency of shoulder bump as our final measure of proper annealing, starting a little low on time, and working up a little. It worked. The press was a Forster, and the calibers were 7mmWSM and .338 Lapua. I think that the type of press was irreverent. One thing did make an impression on me. Setting to exact bump on the Forster seemed to be harder than with a more conventional press design, but perhaps with more experience I would have gotten better at that. Looking back, I probably should have set the lock ring tension on the die so that there was enough tension so that it would not move in use, while still being able to make adjustments on the die. Tightening and loosening the lock rings introduced another variable that was not helpful, because it changed the setting due to lock ring spread from tightening.

 

[ireload2]

Yes will get that variation due to the variables that I mentioned above.
1. Variations in the amount of lube
2. Variations in the dwell time at the top of the stroke (it takes 3 or 4 seconds for the brass to quit flowing and take a set)
3. Number of strokes used (you will see variation with one stroke and almost no variation with 3 or 4 bumps at the top ) When using multiple bumps rotate the case about 120 degrees between strokes. Pull the expander through only the last time if you use an expander. It goes without saying that a springy C press or other light duty press may vary all over the place. Even so multiple passes in a C press is better than only a single pass.
4. Speed of a single sizing stroke if you only use one cycle
5. Brass temper or amount of work hardening.
6. Finish or surface texture of your die. I can polish a die a bit better than most factories because I just take the extra time and I had a lot of practice on a lathe.
7. The finish of your brass - clean brass with a tan patina has a good bit more drag than jewelery finished brass.
8. A mickey mouse case like a 5.56 should have less variation with a heavy duty press than say a badly expanded 30-06 from an old Browning machine gun.
9. Finally if you are using brass that was fired in multiple different rifles then the case expansion will vary from case to case and the resistance to sizing will vary also. This will give the same results as too little lube or sizing too fast. It just stretches the press a tiny bit until you unload the pressure on the ram.
For years I have been forming cases from a 5 gallon bucket of USGI SL-54 30-06 brass that was machine gun fired. I once put a .0005 dial test indicator on my Rockchucker and found that it makes the frame stretch .002 temporarily. A second pass (just a slight retract and bump with about 3 seconds dwell) does not show any more stretch of the press. It only takes a few seconds. To defeat the extra friction with a second or third pass.

This list covers some of the variables in your technique and your brass and dies. When each and every case gets multiple sizings you will quit seeing variation. If you only use one press stroke and have a good measuring tool you will be able to find the variation in your technique.
I get best results with a FL die that has the neck lapped out so it takes only .0015 to .000 expansion to provide a good neck grip on the bullet.
Sometimes with a large groove diameter, the right brass and the right cast bullet a trim die will work right out of the box since many are larger than a FL die in the neck. I found this out on a case forming project where I formed 100 new .303 cases to a perfect fit for a M95 Dutch Mannlicher. Part of the process development involved sacrificing 15 or so cruddy once fired cases. After every sort of crush and fold and swapping out a number of dies I could form the junk cases easily. Then I started on the new brass. I measured every case as I went. I would get one now and then that was .001 to .002 long. Maybe one out of 10. A long case was immediately recycled and 100% of the time the shoulder moved back that additional ,001 to ,002.
I use this method on my ordinary rifles both hunting and military. The bolt guns get set to .000 clearance. I can feel a slight drag closing my stripped bolt with a pinky finger. Lever, pumps, and autoloaders might need a little clearance. .002 seems to be fine for use at the range. My brass lasts a long time and my ammo seems to be more accurate. I shoot a lot of old rifles with iron sights so I am not talking about 1/4" groups but I get very good iron site groups.
My bench rest rifles have a tight neck chambers and I use an ordinary Wilson neck bushing die to size the case about .002 for those rifles.

Thanks guys. Interesting enough, I'm getting about 2 to 3 (.002 to .003) thousandths in shoulder bump variation when using a FL die on once fired brass. The 3 thousandths is about one in every 15 cases so the 1 to 2 thousandths is more common. Is this variation common?

 

[BoydAllen]

In the case that I mentioned above, everything was done the same except for the annealing, which solved the problem.

 

[iowamike]

I’m trying to shoulder bump 7mm rem mag cases back .0015 to .002 using a CO-AX press and FL Forster die. Is there a better way to find the perfect die setting for the .0015 to .002 bump rather than messing around with a ton of trial and error screwing the die in and out? I’m tired of going little by little in with the die only to find that I then over bump the should and have to fire form the case again and start over. I’m reloading for more than one rifle here with 1 die so I really can’t just set it and forget it since it changes between rifles.

I love the idea of Redding’s comp shell holders for controlling that last few thousands for the perfect bump, but they won’t work with the S jaws on my press. There must be a more accurate, more effective, and more efficient way to do this than I’m using...???

I think this is the one failing of the Co=Ax press. Their optional, standard shell holder plate accessory will allow the use of Redding Competition and other standard shell holders but as stated it does not allow the shell holder to float like the standard S jaws. I wrote to Forster a somewhat tongue in cheek suggestion that they work on milling out the standard shell holder plate slightly and incorporate a spring loaded clip holder. Much like the shell holder on the MEC reloading press. If I were to merged the design elements of the two press it would be the end of the other single stage precision presses. Any way I told them to email me when they had it ready and I would order the Co=Ax and improved shell holder. But I'm not holding my breath.

 

[lawrence97]

I’m trying to shoulder bump 7mm rem mag cases back .0015 to .002 using a CO-AX press and FL Forster die. Is there a better way to find the perfect die setting for the .0015 to .002 bump rather than messing around with a ton of trial and error screwing the die in and out? I’m tired of going little by little in with the die only to find that I then over bump the should and have to fire form the case again and start over. I’m reloading for more than one rifle here with 1 die so I really can’t just set it and forget it since it changes between rifles.

I love the idea of Redding’s comp shell holders for controlling that last few thousands for the perfect bump, but they won’t work with the S jaws on my press. There must be a more accurate, more effective, and more efficient way to do this than I’m using...???

I’ve been using a coax press for a while and it’s just as easy to set up as when I was using my rockchucker. Screw the die in a minimal amount for bump and out for less! If you are seeing inconsistent bump then your brass is not consistent (annealed or same amount of firings) and another factor is the amount of lube.
If you are loading for several rifles in the same caliber buy another die so you can set and forget.
Also bumping exactly -.001-.002 from fired and measuring with a hornady or Stoney point tool does not mean you are bumping that much in relation to the chamber. Look up a video by Alex Wheeler from Wheeler Accuracy on how to setup your die for proper bump.

If everything is consistent, it shouldn’t take more than 2-3 cases to get it setup and consistent.