I ordered one of these on 9/11 - received it today.
DSA ZM4 Forged 7075T6 A3 AR15 Upper Receiver - DSZM4CBU-D S Arms
Aesthetics & First Impressions:
The receiver finish under the anodizing isn't anything to brag about.
The M4 ramps have been ground.
I removed the flash hider for an inspection of the crown. Nothing to get excited about, but functional and 90 degrees to the barrel contour.
I set the upper receiver assembly up on my Forster jig to check front sight base alignment - it is right on the money. Picture explanation - machinist square in the foreground, front sight post in the background.
I slugged the bore at .224, dead on the money. Using the slugs again, I checked the barrel twist, which is advertised at 1/9. I measured this one to be 1/8.75 or right thereabouts, nothing unusual for a button rifled barrel.
No gas port burr seen or felt. The bore felt very consistent, no tight or loose spots were noticeable. Interior finish is a little rough, but not enough to feel it when slugging.
The barrel headspaced at GO+.001" using my LMT "test" bolt and PTG gauges.
This barrel is advertised as being "nitrided". Due to my limited investment with this product - I decided to play.
Handguards removed (double heat shields by the way). I cleaned the barrel surfaces using a couple of Clorox wipes, they removed a little bit of oil and residue.
A Nicholson flat file dragged across the finish leaves a shiny spot - no metal removal noticed on the file teeth or barrel.
[ame]http://www.youtube.com/watch?v=JHNgyEjkbzg[/ame]
For verification, I went at it a bit harder with the same file - as if I was trying to remove some stock. No metal removed, just another shiny spot - although it looks like I made it through the finish.
I tried the same thing on a parkerized barrel stub I had laying on the bench, which started filling the file teeth up on the second swipe.
I took some Oxpho Blue to see if it would color the "shiny spot" I made - it wouldn't react.
[ame]http://www.youtube.com/watch?v=rKMMxlW1mVw[/ame]
I then took the same Oxpho Blue and tried it near the muzzle - no difference in reaction or how it colors the patch.
[ame]http://www.youtube.com/watch?v=d4aEMAvmaYA[/ame]
Overall - its a $275 upper. Looks as good or better than what I used to see for roughly the same money before the (1994) frenzy.
I'll likely work over the feed ramps a bit more after test firing, and chances are I'll recrown it as well.
I remain intrigued by the barrel finish - I'll not be treating this one nicely, we'll see how it holds up.
If it shoots well this weekend, I'll likely be ordering another.
DSA ZM4 Forged 7075T6 A3 AR15 Upper Receiver - DSZM4CBU-D S Arms
Aesthetics & First Impressions:
The receiver finish under the anodizing isn't anything to brag about.
The M4 ramps have been ground.
I removed the flash hider for an inspection of the crown. Nothing to get excited about, but functional and 90 degrees to the barrel contour.
I set the upper receiver assembly up on my Forster jig to check front sight base alignment - it is right on the money. Picture explanation - machinist square in the foreground, front sight post in the background.
I slugged the bore at .224, dead on the money. Using the slugs again, I checked the barrel twist, which is advertised at 1/9. I measured this one to be 1/8.75 or right thereabouts, nothing unusual for a button rifled barrel.
No gas port burr seen or felt. The bore felt very consistent, no tight or loose spots were noticeable. Interior finish is a little rough, but not enough to feel it when slugging.
The barrel headspaced at GO+.001" using my LMT "test" bolt and PTG gauges.
This barrel is advertised as being "nitrided". Due to my limited investment with this product - I decided to play.
Handguards removed (double heat shields by the way). I cleaned the barrel surfaces using a couple of Clorox wipes, they removed a little bit of oil and residue.
A Nicholson flat file dragged across the finish leaves a shiny spot - no metal removal noticed on the file teeth or barrel.
[ame]http://www.youtube.com/watch?v=JHNgyEjkbzg[/ame]
For verification, I went at it a bit harder with the same file - as if I was trying to remove some stock. No metal removed, just another shiny spot - although it looks like I made it through the finish.
I tried the same thing on a parkerized barrel stub I had laying on the bench, which started filling the file teeth up on the second swipe.
I took some Oxpho Blue to see if it would color the "shiny spot" I made - it wouldn't react.
[ame]http://www.youtube.com/watch?v=rKMMxlW1mVw[/ame]
I then took the same Oxpho Blue and tried it near the muzzle - no difference in reaction or how it colors the patch.
[ame]http://www.youtube.com/watch?v=d4aEMAvmaYA[/ame]
Overall - its a $275 upper. Looks as good or better than what I used to see for roughly the same money before the (1994) frenzy.
I'll likely work over the feed ramps a bit more after test firing, and chances are I'll recrown it as well.
I remain intrigued by the barrel finish - I'll not be treating this one nicely, we'll see how it holds up.
If it shoots well this weekend, I'll likely be ordering another.
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