What factory practice ammo will simulate Underwood or Corbon defensive ammo at a better price...?

I've got a Glock 20.3 but seriously considering adding a 10mm 1911 to the safe.

Not sure. I have only shot the PPU thus far out of my G20.4. Shoots great. Also looking at maybe adding the new Ruger SR1911 in 10mm.

Underwood FMJ ammo

Sig 10mm FMJ ammo is full power.

Georgia Arms "Canned Heat"

I think we need to reload.

Underwood FMJ is a bit cheaper.

Given the bullet-weight, Sig's 180gn FMJ is an upper mid-range 10mm load, spec-ed at 1250fps.  So no, it's not full-throttle 10mm ammo.

For a 180gn 10mm bullet, full-power is in the 1300fps-1350+fps range.

That said, Sig's 180 load is "spicy"-level 10mm ammo that's excellent and accurate. It makes for great "practice ammo" which you can actually find and buy off the shelf at, say, Cabelas.  Sig's price-point seemed reasonable to me, as compared to others  -  keeping in mind that the cheaper variants of 10mm "range" or "target" ammo from other makers are almost always .40-duplicating junk.

I've shot up 2 cases of Sig's 180gn ammo now, and the velocity was very consistent, as was accuracy.

Sig.

It's some toasty stuff. They didn't mess around. Very impressed.

Sig 180gr 10mm is full power ammo.  (180gr @ 1250).

The mythical 10mm ammo of old is just a myth.  The original 10mm rounds made by Norma were the standard:  170 gr @ 1300 fps and 200gr @ 1200 fps.

You're correct on the fps/fpe stats of the original Norma loads of the mid-1980s.

Those, however, have been by-passed (and safely) with advent of the new generation of hybrid propellant compounds. These propellants allow for greater velocity with less pressure than back in the Norma era when they didn't exist.  Double Tap and some other commercial ("boutique") makers pioneered the use of hybrid powders to make undiluted 10mm ammo in various bullet-weights, which frankly assisted in its resurgence as a popular pistol cartridge. Thus, you can find 200gn FMJ and 220gn (hardcast) loads approaching 1275fps and 1250fps, respectively, ... and those velocities are safely attainable.

On the 180gn load @ 1250fps -  no, sorry, but you're incorrect. The Sig load is but a recent copy of McNett's (DT's) mid-2000s load that he designed to be a "hot-ish" upper mid-range "practice"  load. It's purpose was to facilitate training with less expensive FMJ ammo that somewhat approximated a full-power 10mm JHP carry load. Obviously, given current pricing, you can make the same level of practice & training ammo by reloading.

For a 180gn 10mm bullet, "full-power" is the 1300-1350fps range. Buffalo Bore, DT, and Underwood have all marketed 180gn JHP loads in that range.

OP was asking for factory full power practice loads.  The Sig 180pr FMJ is a great full power practice load.  I don't care what the "boutique" ammo manufactures can do with modern powders and JHP bullets.  First of all, I have never seen any of the three you mentioned on a store shelf available for sale in person.  And great, a boutique ammo manufacture can safely push a 180 gr bullet at 1300 fps.  So can any reloader.  How does that make a 180 gr fmj bullet at 1250 fps suddenly not "full power"?  

OP, good luck finding some of that "full-power" boutique ammo.  Or you could just get some of that Sig ammo for around $25 a box of 50.

I know what the OP was asking. You never said "practice load."

I was responding to your  earlier unqualified statement that Sig's 180gn 10mm FMJ ammo is "full-power ammo" "@ 1250fps".  That was incorrect, ... and it's still incorrect for the reasons I explained.

Just as I originally posted, yes, Sig's 180gn FMJ ammo is both good practice ammo and reasonably priced if you don't reload. The OP should buy a few boxes to test out at the range.

Wow, you are being obtuse.  

I don't care what McNett did in the 2000's.  You are saying he "designed" the 180 gr loading at 1250 fps?  Is that what you are saying?  Come on man, that is BS.  I've been shooting the 10mm since 1989 and reloading the cartridge since 1990.  My memory isn't good that far back, but the 180 gr bullets started becoming available for reloaders around 1991 I think.  Around the time the 40 S&W cartridge was started.  So yeah, the 180 gr @ 1250 fps has been around for quite awhile.  So there is that.

The Norma 10mm loadings were the first rounds available for the 10mm.  Winchester, PMC and Hornaday began to offer ammo for the 10mm with similar specs  (Remington, Federal and Blazer had "weak" ammo).  The Winchester 175 gr at 1290 fps was considered a "full power" loading.  The PMC had a 170 gr at 1200 fps, was not exactly fast, but wasn't 40S&W either.  I forget what Hornady had back then and am not sure when their 180 gr loading became available.  I do remember they did have 10mm ammo, just not what bullet weights they offered back in the early days.  The 180 gr bullets were not common in the early reloading days.

So, you are saying ALL the 10mm ammo available at the birth of the gun / cartridge was not full power ammo?  And the 10mm round existed for years before McNett invented "full power" ammo in the 2000's?  Come on, man.  

Didn't mean to start a war fellas....

I was just looking for an affordable practice load that would simulate the recoil impulse of my defense ammo which is Corbon DPX

I'll try to grab som Sig ammo

The Sig ammo is also at Academy at decent prices