"80%" Para?

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Without doing pre-purchase homework, I recently acquired an alloy ParaOrdnance P13 frame. The idea was to replace the P14 frame that has taken up residence ina MechTech CCU that works so well that I'm going to leave it there. I expected to do some machining (allegedly, the typical "80%" 1911 can be completed on a drill press with a the proper jig). My problem is that nearly every other frame comes with the slide release hole drilled. The mag release hole is there but it's cast in with no sign of having been machined. The slide release hole is where the dimensions are reference from on the 1911 and the tolerances are +/-.005 except for a few that are +.002, -.000. I'm not thrilled about attempting to locate remaining holes and surfaces from the unmachined and undersized mag release hole due to the problem of tolerance stacking. Sarco, where I assume this frame came from after Para's demise, knows nothing and has no Para specific prints or jigs. Does anyone have experience or insight into this? At present it appears that I have $100 worth of scrap aluminum.
"Better to die on your feet than to live on your knees" - Emiliano Zapata

Re: "80%" Para?

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What needs to be located in relation to that hole?

Edit to add:

Are you working with a drill press or a mill? What's your tool situation like?

If it was me, I'd take measurements from my other frame to figure out the relationships. That lets me see whether the mag release hole relates correctly to other features that are present. I'd probably look for something else to reference, then locate the mag release hole and ream the hole in the casting.
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Re: "80%" Para?

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Marlene wrote:What needs to be located in relation to that hole?

Edit to add:

Are you working with a drill press or a mill? What's your tool situation like?

If it was me, I'd take measurements from my other frame to figure out the relationships. That lets me see whether the mag release hole relates correctly to other features that are present. I'd probably look for something else to reference, then locate the mag release hole and ream the hole in the casting.
Nearly everything; hammer pivot, grip safety, MSH pin, thumb safety... . This won't be possible on a drill press. I may have access to a CNC mill. The mag release hole is the closest thing to a reference I have. Cast surfaces aren't reliable reference points. If the top of slide rails was already decked I'd chance it but it's cast and far from being flat. That would have been my choice for defining the Y plane.
"Better to die on your feet than to live on your knees" - Emiliano Zapata

Re: "80%" Para?

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nigel wrote:This guy has detailed photo thread of the steps he used.
https://www.calguns.net/calgunforum/sho ... p?t=700987
You may have to register to see the pics if you are not already a member.

Looks like he skimmed the top of the frame flat, and then used the slide catch slot as the second datum.
I've seen it. The story ends before he ever got to a range report. After doing a little research I have a lot more confidence in the dimensional accuracy of the casting (.005in/ft). The top of the dust cover measures out to that spec along its length so I think I can get away with using the using that along with the mag release hole to jig it up square. The plunger hole in the top of the frame is centered between the rails so that'll be useful as a reference. The slide stop slot on the casting is way out of tolerance (by 1911 standards). Thanks for helping me think this one through. It's looking more feasible. I'm still a little skeptical since I've yet to find any accounts of how any of these Sarco P13's came out.
"Better to die on your feet than to live on your knees" - Emiliano Zapata

Re: "80%" Para?

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nigel wrote:Good luck! There are easier projects.
Yeah, I know. I'm getting a complete P14 frame for my P14 slide/barrel but if I manage to get the P13 working I'll get a Commander slide for it. Not like I'm in a hurry. As long as it looks feasible I'll plug away at it.
"Better to die on your feet than to live on your knees" - Emiliano Zapata

Re: "80%" Para?

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I understand your concern about using the cast mag release hole as a reference, but taking a bunch of measurements might make it less worrisome. Modern castings can be pretty accurate.

Decking the top of the rails sure sounds like an excellent approach to start.

If I was doing this, I think I'd prefer a manual mill with DRO to a CNC setup. Measuring by movement and contact is often a lot easier to do well when there's a little physical feel involved.

Good luck on this thing! Please keep us informed of your progress. Would be cool to document the build with photos and such too. Wouldn't you be excited if someone had already posted that somewhere for you to find :)
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