• This Forum is for adults 18 years of age or over. By continuing to use this Forum you are confirming that you are 18 or older. No content shall be viewed by any person under 18 in California.

CPS just beat the Sinclair primer seater?

6BRA

6BRA

Gold $$ Contributor
FULL RIM CONTAINMENT....KNOWN AS RIMLOCK.
Although at a much higher price with Tube feed, the CPS now has the ability to seat without Rim thickness making a difference.
Rim deflection as with a shell holder Sinclair style tool, where as 30 percent or more of the rim is unsupported, has been eliminated.
Appears to be brand new, anybody got their hands on this yet? Only video I have seen is on Instagram.


If you already have the the CPS, this may be the bottom of this rabbit hole.
 
6BRA said:
FULL RIM CONTAINMENT....KNOWN AS RIMLOCK.
Although at a much higher price with Tube feed, the CPS now has the ability to seat without Rim thickness making a difference.
Rim deflection as with a shell holder Sinclair style tool, where as 30 percent or more of the rim is unsupported, has been eliminated.
Appears to be brand new, anybody got their hands on this yet? Only video I have seen is on Instagram.


If you already have the the CPS, this may be the bottom of this rabbit hole.
Click to expand...

You Sir just made me spend $210....Ty :mad::mad:
 
Evan said:
If you’re going for the ultimate solution, I would expect it to index off the shoulder and not the rim or base of the case at all. The shoulder defines the position of the case in the chamber and the distance to the firing pin tip.
Click to expand...
Isn't this a headspace control function?
 
6BRA said:
CPS now has the ability to seat without Rim thickness making a difference.
Click to expand...
A Forster Co-Ax press does the same thing, at dramatically lower price - aka "free" once you have the press - and likely greater speed. The only thing is it seats to a non-adjustable depth. But it is a fixed depth indexed from the bottom of the case, which ought to be the ultimate arbiter.

Having said that, I seat by feel on a Lee bench primer.
 
6BRA said:
Isn't this a headspace control function?
Click to expand...
Sure, but no one hits 0.000” on all their brass. We don’t even have instruments to measure it any better than calipers at 0.001”. I think since we’re spending $800 on bespoke equipment, we should not stack tolerances and should instead index off the datum that actually controls position so the firing pin travels the same distance to the primer every time. Can’t even make the convenience argument now because the rimlock is a threaded assembly that has to be unthreaded for every case. I have a couple ideas in mind for how to conveniently index off the shoulder when priming but I haven’t had the gumption to spend the money building a prototype.
 
Last edited:
Evan said:
Sure, but no one hits 0.000” on all their brass. We don’t even have instruments to measure it any better than calipers at 0.001”. I think since we’re spending $800 on bespoke equipment, we should not stack tolerances and should instead index off the datum that actually controls position so the firing pin travels the same distance to the primer every time. Can’t even make the convenience argument now because the rimlock is a threaded assembly that has to be unthreaded for every case. I have a couple ideas in mind for how to conveniently index off the shoulder when priming but I haven’t had the gumption to spend the money building a prototype.
Click to expand...
I think you will find most competition shooters control their headspace to .0005 or less for record rounds.
Just a guess on my part.
 
6BRA said:
I think you will find most competition shooters control their headspace to .0005 or less for record rounds.
Just a guess on my part.
Click to expand...
How do they know? Even high quality Mititoyo calipers only resolve to 0.0005” and their accuracy is worse then that. I think I honestly hold around 0.0005 to 0.001” and every piece is also checked with a stripped bolt in my chamber for feel.

Really the whole point of everything we do is to eliminate unknown variables and the base of the case was only ever a convenient measuring point; it doesn’t actually control anything in a bolt action rifle so bespoke tools should endeavor to control from the correct datums.
 
Having the anvil compressed exactly the same across all cases. Will keep the firing pin travel the same if pockets are uniformed. Lock time. Ignition. Plenty were doing this by measuring rim thickness and sorting brass. I can tell you people can turn necks to within .0002 and measure it. Don't take my word for it though. My pockets are all uniformed to .1235 and I can measure it. The tools are out there. Don't just run a uniformer in and when the brass stops coming out think you are there. It doesn't work like that. And after each firing the web will move. The outside edges of the pocket will remove brass if you run the uniformer in again. Measuring anything to .0005 isnt much of a problem in my opinion. We know what opinions are like though. These will sell to anyone that already has a CPS.
 
6BRA said:
Having the anvil compressed exactly the same across all cases. Will keep the firing pin travel the same if pockets are uniformed. Lock time. Ignition. Plenty were doing this by measuring rim thickness and sorting brass. I can tell you people can turn necks to within .0002 and measure it. Don't take my word for it though. My pockets are all uniformed to .1235 and I can measure it. The tools are out there. Don't just run a uniformer in and when the brass stops coming out think you are there. It doesn't work like that. And after each firing the web will move. The outside edges of the pocket will remove brass if you run the uniformer in again. Measuring anything to .0005 isnt much of a problem in my opinion. We know what opinions are like though. These will sell to anyone that already has a CPS.
Click to expand...
I understand where you’re coming from. Primer pockets and necks can be measured with indicators and micrometers capable of tenths or better. Calipers with a comparator are not capable of that. Ultimately you control each dimension the best you can and because your calipers measure 0.000 difference, and your pocket depth measures 0.0000 difference and you crush your primers to 0.000 difference, you think that every case is now the same, but there are tolerances in every measurement, and the most precise measurements we make are all one big caliper measurement removed from the actual controlling datum in the rifle: the shoulder.
 
Evan said:
I understand where you’re coming from. Primer pockets and necks can be measured with indicators and micrometers capable of tenths or better. Calipers with a comparator are not capable of that. Ultimately you control each dimension the best you can and because your calipers measure 0.000 difference, and your pocket depth measures 0.0000 difference and you crush your primers to 0.000 difference, you think that every case is now the same, but there are tolerances in every measurement, and the most precise measurements we make are all one big caliper measurement removed from the actual controlling datum in the rifle: the shoulder.
Click to expand...
I'd suggest you control your shoulder bump then. And then you can go down the other rabbit holes. How are you going to.measure anvil compression from a shoulder datum?
 
6BRA said:
I'd suggest you control your shoulder bump then. And then you can go down the other rabbit holes. How are you going to.measure anvil compression from a shoulder datum?
Click to expand...
My shoulder bump is controlled to the degree that I can measure it with calipers. Can’t do better without a better measuring tool. This is analogous to saying my powder charge is the exact same shot to shot, but if I am only using a chargemaster I can’t know any closer than to within 0.1gns, if we’re generous. A better scale is required to know it’s the same down to the kernel.

We should hold the case by the shoulder and not the rim when we press the primer in. But we also need to cut and measure our pockets relative to the shoulder first so that we can get the primer crushed correctly. Well, thats why it was convenient to just index off the base instead and concede the stack up of tolerances it induces.

I am not arguing that this will show up on target - I am skeptical that it would, but it is a stone left unturned by commercial offerings to-date. A thorough attempt to eliminate variation would also attempt to eliminating fundamental problems with tolerance stacking.
 
Evan said:
Can’t do better without a better measuring tool.
Click to expand...

I'm not saying using these is necessary, but they will assess your shoulder bump to .0001" if used properly.

And if one is using a setup with a dial indicator, like https://www.pmatool.com/products/pma-quick-case-checker-case-gage-complete.html , then .0001" is easily within reach with the right dial gauge and perhaps some tool modification - used properly.
 
Last edited:
You must log in or register to reply here.

Similar threads

orkan
Introducing the BASE CPS - Competition Primer Seater
Replies
2
Views
2,368
orkan
orkan
Flash hole runout?
Replies
6
Views
1,749
nheninger
concentricity issues
2 3
Replies
45
Views
6,459
krprice84

Upgrades & Donations

This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.


Click Upgrade Membership Button ABOVE to get Gold or Silver Status.

You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.


To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.

Classified Ads

Forum statistics

Threads
168,532
Messages
2,257,344
Members
81,372
Latest member
MRW

Share This Page

Back
Top