Minimum-Maximum between cartridge base & recoil plate

[kywoodwrkr]

What would be your proposed optimum tolerances between cartridge head and recoil plate for these rimmed cases?
(Have SAAMI data)
32H&R/ ?
38/357?
45AR/Colt?
Not considering doing any others right now.
I can measure my 45 Colt and determine what it is, but what do you consider the optimum value(s)?
What correlation is there between SAAMI headspace dimensions and reality in your experience?
I'm tinkering with an old 45ACP cylinder and converting to AR and it is the base of this question.
This will be put in a mill and recesses milled individually.
If you have performed this operation, I'd appreciate any gotchas you discovered.
Thanks.

 

[DGW1949]

Not sure what you mean by "correlation between SAAMI headspace deminsions and reality".
I'd stick with the SAAMI headspace spec.
Some carefull measuring will tell ya how deep to cut the rim recess so's you'll end-up with the correct headspace.

DGW

 

[kywoodwrkr]

"correlation between SAAMI headspace deminsions and reality"
What I mean is the rim thickness per SAAMI can be .079" to .089".
Headspace per SAAMI is .090" Min to .104" Max.
The minimum rim thickness(.079) with max headspace(.104) results in a .025 value.
My question is merely what do those who have worked in rechambering and rechambering find to be best and most forgiving?(This I consider reality)
Now I realize the Ruger was not built to be a traget grade weapon.
I just want to minimize any negative variables,(speaking of headspace only here) I can while reworking a cylinder. I will attack other variables later as I come to them.
For instance the next process on this project will be the cylinder latch guide block described by another member here.
These are things which are entirely to expensive to facilitate on a mass production item.
I do have the time and equipement available, so why not try them.
I appreciate your response and clarifying question.
Thank you.

 

[DGW1949]

OK, yes...now I see what you're getting at.
On paper, that's a lot of possible-variance between one cartridge rim and the next. On the other hand though...in reality, it may not be...meaning that I'd want to measure the actual rim thickness on a couple of different brands before I jumped to any conclusions.

But.......Just for the sake of discussion, let's say that yeah, any/all available 45AR brass does display a .010 variance. Striving for the SAAMI minimum headspace would cut your ".025 value" down to .010, which should still work fine with any brass. Also bear in mind that a revolver's headspace increases as the gun wears, and that the rim-thickness of brass decreases with use.....which to me, is reason enough to always start with the minimum headspace spec......which BTW, should be measured individualy, on each individual chamber. Reason is, it aint uncommon to find that you're working with a cylinder that has enough run-out to make a .001 (or so) difference in headspace, depending on which chamber is being measured. I've run into that quite-often while maching BH cylinders for a replacement bushing (aka collar).
There's also firing-pin protrusion to consider....meaning that the amount which was "right" for your 45LC or 45ACP cylinder might not be right for your rechambered 45AR cylinder....which to me, is yet another reason to strive for minimum headspace. You can make a FP-tip shorter but ya can't make it longer, and sometimes .010 matters.

Them's my thoughts on the matter.....hope it's helped.

DGW

 

[Carry_Up]

What would be your proposed optimum tolerances between cartridge head and recoil plate for these rimmed cases?

???
The whole point of headspace recommendations is to prevent case bulging or blowout due to unsupported brass. Varying rim dimensions will result in small variations in dynamic headspace (from cartridge to cartridge). Your actual question has to do with what is the 1) safe and 2) reliable gap between case head and recoil plate. There has to be a minimum clearance there - measure with a feeler gauge using new unfired cases. For a GP style frame about .006" to .008" minimum will allow the cylinder to rotate without binding on the case heads. As this measurement gets larger, your cases will have more unsupported brass exposed during firing and eventually could bulge or blow out depending upon the charge. As the measurement gets smaller, the cylinder will start binding because there is no room between the case head and the recoil surface. Headspace isn't really an "adjustment"; it is a safety and reliability check. And it is not an indicator of how accurately a gun will shoot.

-CU

 

[kywoodwrkr]

Thanks for the answers.
Accuracy is not a problem that I am trying to solve.
I'm not even at the point where I have all the parts working together to my satisfaction yet.
In this situation I have a older Vaguero which had a 45 ACP cylinder with it when bought used(2007 time frame).
Just now getting around to trying it out.
Good news is I have two cylinders.
Bad news is neither one is worth a tinkers dam, as bought.
With the factory cylinder, the hammer would not cock on three consecutive chambers.
Have since stoned the proper ratchet teeth so all now result in hammer catching on the sear. But it locks up too tight to suit me.
45 ACP cylinder had headspace problems resulting in excessive pressure on three cylinders.
My resolution to this was to mill recesses in the chambers for 45 AR brass.
Have two chambers done and looks like my math worked out.
I'm starting with .004 space between head and recoil plate. I can always remove more in binding occurs.
Each chamber also has different ofset from ratchet end plane.
.074,.072 and .073.
I'm centering mill on chamber and then milling a circle about .025 deep.
Am going to load some loads(identical to ACP) and see what they do.
Cylinder does not lock up as tight as the orginal cylinder, so this points to one of those things that can be wrong when you, or whoever, who 'just picks up another cylinder and puts'er in'.
Whe the chambers are as I want them, i"ll flip the cylinder over and work on the chamber mouths.
I have no animosity towards either condition, as this was to be a learning platform for me.
Have stock(4140) for a bunch on new cylinders-just not sure of time available. But do any of us know that for sure?
From a production view point the original cylinder is probably with in their parameters.
But when analyzed on a co-ordinate measuring machine the variance seems astronomical.
Thanks again for the responses.