I just gave my new Olympic Arms 9mm upper a good test run yesterday and I am very happy with the performance! I'm sorry this post is a little long but it may help some prospective buyers decide they have to have one too.

Stats:
Oly 9mm upper 16" A2 preban upper on a preban lower with CAR 4 position stock.

Ammo used was UMC 115 gr. FMJ

Magazines were the Oly modified Sten and a SOCOM block with several unmodified Stens

Fit and finish is outstanding and it matched up with my lower tight and secure.

After a good teardown and cleaning to remove a large amount of packing grease and such it was off to my favorite gravel pit for live firing.

Using the A2 Army 25 meter zeroing target it took about 10 rounds to zero the iron sights. One click on front for elevation and couple clicks on back for windage and it was dead on. Then I put on a ProPoint II red dot sight using a simple carry handle adapter and again a couple clicks elevation and windage and it was off to the races!

All the mags fed great with not a single jam!
After cleaning about 20 ea. Sten mags I have come to really hate cosmoline! If I had saved and package all of it I removed I could probally go into business selling it!

I got tired of punching paper pretty quick so I
setup soft drink cans at varying ranges spread out and went to quick fire drills and had a blast. This piece has no recoil and light noise and muzzle blast so you can fire from all sorts of holding positions and stances. Using the red dot with both eyes open you can really swing quick from target to target keep those cans hopping! Ranges from 5 to 100 yards saw little
elevation drop for can size targets. 9mm performance out of rifle length barrel seems better than pistol length.

Only question I have for other 9mm Oly owners is do you notice that the spent brass is really scorched/burnt on the outside of hull and I even picked up a couple cases that were split down sides? Any chance I'm having firing out of battery or bolt not fully closed on chamber?

Also would you recommend buying spare parts such as the ejector assy and extractor, etc?

This unit was a little more expensive than my
.223 AR15 to build but the fun factor is much higher!

Split would not be good. If fired out of battery they should be swelled like a pumkin but not split. Split sounds like ammo reloaded too many times to me or perhaps Blazer aluminum cases.

UMC 115 Grain, doesn't sound like a reloaded case.

Chamber specs would have to be pretty bad for it to be splitting in the chamber.  

I agree with David, Pumpkin type swelling if it was firing out of battery, and I am sure you would notice the odd sound/behavior of an out of battery round.

TRG

Pistol caliber carbines are a blast to shoot.
The lack of recoil makes "pegging" pop cans really easy.

I haven't seen a split case with mine.  The brass is dark, but maybe the chamber is slightly looser SAAMI spec and maybe it gets either dirtier or hotter quicker with the Oly design.

cj