The test is the use of el cheapo steel base cases that have started showing up everywhere.
From another string:
(09/03/2017) So I went out and got another 870 Express....
... Tho this time it was as Remington_Express Tactical "A-TAC" Demo model that had seen some reasonable shooting at corporate.
Being a smoothbore/cylinder, I went through about 7 different brands of slug looking for its favorite food. I found that it really liked the old-fashioned/naked Foster slug in both the Remington 1oz "Slugger" (clover-leaf at 50) and Winchester's similar 1oz "Rifled Slug HP (almost clover leaf).
In fact it ate everything so well -- even though all the bases were clearly copper-coated steel --that I said to myself..."Self, they've fixed the extraction jam when using ElCheapo Winchester WhiteBox...."
....That's wrong....
First ElCheapoWhitebox round req'd me to butt-stroke the bench to get it out. Being stupid, I tried it again. (RESULT: What part of stupid did I fail to understand ?)
Irritated (remember, I'd done this before w/ an Express that I bought for I son-in-law)
https://thefiringline.com/forums/showpost.php?p=4368507&postcount=25, I hauled out my old WingMaster and two more of my reeeeally older Model-12s.
Smooth as silk.
Even w/ ElCheapo Steel Basr
Now I'll grant you that this is cheap ammo (Win WhiteBox, Win "USA" and Field & Stream "Game & Target" all appear to be made by the same Federal outfit in Akron). And since it functions just fine in the old guns, I can't particularly blame Federal.... BUT....
But I sure wish Remington would get its act together after all these years of "Express" problems.
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(09/04/2017) Back....
"Improved" Ran a combined box-worth of the Cheapos mentioned above.
Only had two that required table banging; Most shucked reasonably cleanly; and a half-dozen req'd I push the slide
forward before it would release/back cleanly.
Came back and did it again starting with 220 through 600grit
The thing's a doggoned mirror.
Film at Six.....
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(09/05/2017) The problem appears to be (1) badly cut rim clearance opposite the extractor, as well as residual machining ridges in the same area. Both combine to "jam" the ElCheapoExpanded rim against non-existent clearance when the extractor tries to pull [one side of] the opposite side of the rim free.
So after some
veewy, veewy careful dremel tool work with LOTSA cutting oil and moderate speeds on the area opposite the extractor....
Deep Breath...
High Brass Remington Slug. Perfect extraction/ejection
Low brass Double-A.... Perfect extraction/ejection
REALLY HOLD BREATH....
25 continuous rounds (7ea at a whack) of mixed low-brass Godawful ElCheapoGrande thin steel bases mentioned in the OP:
Every one slicker than Nasal Mucus --- (Wow !)