aluminum or steel?

[Texashogman]

So-- I love to tinker in the garage and make things-- have machined 80% polymer ar lowers (won't do those again as the buffer tower breaks too easy)--- and also 80% aluminum ar lowers

I do them just to challenge myself and to be able to say I have done them---fun, rewarding, not to save $ though, not hiding from the gooberment either as I'm on their nfa list already.

a buddy of mine is looking into buying the matrix 1911/2011 rail cutter, decking jig, and barrel seat cutter for doing 1911's--if he does I would be able to borrow the tooling from him.

I have always toyed with doing at least 1, but never felt comfortable cutting the slide rails or barrel seat until I saw this tool

there are plenty of options for calibers (9mm,38 souper,357sig,40s&W,45acp, and of course the 10mm), I saw that RIA has a FS 5" 40/10 builders kit and thought this might be a good way to get my feet wet

now for my question--- there are steel and aluminum lowers, obviously the aluminum would be easier to cut and fit for a first time build, but the steel would outlast an aluminum lower

what would you recommend for a 10mm 5" 1911 build lower?? aluminum or steel any other pro's or con's to think about with the 2 lowers??

[dred]

Steel will result in a pistol that is enjoyable to shoot.  For a example, get some +P 45ACP, and borrow one each of a steel frame 45 and a lightweight frame 45 1911.  Shoot them back to back; then decide which you prefer to finish your range session with.  The lightweight makes for a fine defensive tool and it is capable and controllable; the steel brings FUN to the party.

[sqlbullet]

Steel, all the way.

1.  Longevity.  Aluminum is questionable for a 10mm gun frame to begin with.  I know of no other gun in 10mm with an aluminum frame.  Gotta be a reason no major mfg is picking aluminum.  This could be overcome with an all new design, but a 1911 was designed in steel for 45 ACP.  Aluminum works for 45 ACP because the frame was over-built for the army.  But 10mm + aluminum seems like a recipe for a frame fail around 10-15K rounds.

2.  Shootability.  The extra weight will be appreciated.  Dred nailed this one.

3.  Nostalgia.  This isn't what you think.  I am not saying make it outta steel cause 1911's should be steel.  I am saying a gun that YOU are going to build should last.  Lotta sweat, tears and possibly blood will go into this build, so make it outta somthing your grandkids -> grandkids can enjoy.

If you wanna work with aluminum first, go nuts.  But build up a 9mm 1911 on that frame, or a 45 acp.  But 10mm will want steel.

[Texashogman]

My thought on aluminum was that if glock can make a poly lowered 10mm, then an aluminum lower should be sufficient--- but honestly I'm kinda leaning towards steel

[sqlbullet]

Fatigue limit.  Poly and steel don't have one, but aluminum does.

Poly and steel can flex an indefinite number of times, but as long as the elastic fatigue limit is not exceeded, strength remains as good as new.

Aluminum gets weaker each time it cycles and will eventually crack where it cycles.

[Texashogman]

I did some more searching and did find a few other tidbits on aluminum frames

found one guy that said he has an aluminum frame commander 10mm with 70,000 rounds through it with no issues, but he has it scanned for internal cracks every 25,000 rounds ( not totally sure I believe him)
also found 2 possible issues with aluminum lowers in general--- 1 is the slide stop hole tends to elongate, 2nd is the steel magazine followers tend to chew up feed ramps if not careful
I could not find any manufacture that has ever made a 10mm semi auto with an aluminum lower
I have a sig p224 that has an aluminum lower (40 cal)--- but sig only sells their 10mm guns in steel or ss lowers
also found 2 grades of aluminum 80% lowers --7075, and 6061--most of the more reputable companies use the 7075
like you guys said--- gotta be a reason that no manufacture has ever made a 10mm with an aluminum lower--I'm sure they would work for a while, but don't want to deal with split rails or other issues down the line
for my own piece of mind I will leave the aluminum lowers to the 9mm guns, steel for me for sure
thanks for the graph sql--I have never seen that exact info before--nice to know

[cgreth]

I have an 1989'ish P220 in .45 acp.   Aluminum frame and steel slide.

After approximately 18K rounds, the frame rails had developed a sliver of aluminum that was being extruded out of them on both sides of the frame.  Not a lot, it was a thin sliver going about 2 inches down each rail on the frame.

I simply took a sharp pocket knife and scraped/sliced the metal off the rails.   Now at approximately 23K rounds, the frame is still looking fine with no extruded metal that i can see.

Before, during and after this the pistol never had any trouble.   Has always run like a top.

Only bringing this up since;
If .45 acp can do this, I imagine 10mm can do it a lot faster or at least more aggressively.
None of my steel framed pistols or my polymer pistols with steel inserts have done this.

[SHOOT1SAM]

...gotta be a reason that no manufacture has ever made a 10mm with an aluminum lower...

I had a 10mm CCO built, and I wish I had insisted on an aluminum frame...simply for ease of carry.  I believe it something that is unproven, that an aluminum frame will not hold up to the 10mm.  100,000 rounds?  Maybe not, but for a gun that is carried a lot, and practiced with...enough, I think it would be fine.  If I could find an aluminum framed .40 that could be reamed out to 10mm, I would get it and roll the dice.

Sam