Is it forged T6 alloy like in the lower receivers of AR rifles? Or is it Dural(aircraft aluminum)? Or is there such a thing as alloy casting? Thanks! How does it stand to in durability compared to an all stainless framed P series?

I believe they used to use recycled Hofbrau cans but that may no longer be the case . My guess now would be milled 7075.

T6 is the heat treatment/hardness, not an alloy. Most likely it's 7075.

I will guess and agree it may be 7075. It's definately bar stock as there have been photos of the stock posted in bar form and sawed billits.

I don't know but keep in mind that the alloy frame is anodized and that there is a steel locking insert. Keeping the frame rails well lubricated and changing the recoil spring every 3000-5000 rounds will help insure a long long frame life. On older folded steel slides it is also important to change the breech block pins about every 5000 rounds so that the breech block never becomes loose or it can place a lot of stress on the frame if it starts to move during firing.

Nobody knows but Sig and they are unlikely to tell you. I have been to the factory and as others noted its raw form is bar stock. If I had to guess as have others its 7075T6. But its just a guess.
As for its life versus stainless I guess it depends on what is the issue of durability? It will certainly be worn more by use (mitigated by lube) than stainless. I doubt you will wear out a pseries sig. but if the extra weight doesn't bother you then a stainless one will likely have less potential issues.

Is it from a forged 7075 aluminum blocks or just machined from solid block of aluminum billet....?

again no one can actually know unless SIG were to say. But the odd's its a forging are just low. It would have no real value in this actual application. the stresses on a Sig PSeries lower are incredibly low in alloy terms. I would not pay for it.

quote:

Originally posted by perrinyanna:
Is it from a forged 7075 aluminum blocks or just machined from solid block of aluminum billet....?

Slabbed from bar stock by a saw. Pics were posted maybe a year back.

Here's a pic I took of some P series frame blanks just before going into the CNC machine, at the Exeter plant about 10 years ago. No idea what type of alloy it is.



After machining.

quote:

Originally posted by perrinyanna:
Is it forged T6 alloy like in the lower receivers of AR rifles? Or is it Dural(aircraft aluminum)? Or is there such a thing as alloy casting? Thanks! How does it stand to in durability compared to an all stainless framed P series?

7075-T6 is "aircraft aluminum."

More common "aircraft alloys" are 2024-T3, and 6061-T6. Both are not appropriate for a firearms receiver. 7075 has far better properties, given adequate heat treatment. 7075 is more susceptible to work hardening and intergranular corrosion, however.