Checking the extractor tension requires the use of a force dial gauge (with appropriate hook attachment to use on extractor hook). The tension on the .40/10 guns is listed as being within 4-8 lbs, but that's just the bench testing.
Getting any particular .40 to feed & extract properly might require some fine tuning, meaning running the tension more at the lower or higher end of the recommended range, or filing the extractor so it "blocks" tighter or looser.
The dimension of the hook edge to the opposite breech face shoulder is checked using a Go/No-Go bar (block) gauge. Armorers also used to use a Go/No-Go "flag" gauge, to check the dimension between the inside of the hook and the breech face behind it, but as time passed the company decided we didn't really need that tool.
Also, a trick I learned from a much more experienced armorer some years ago, who worked for an agency who issued older 4006's and newer 4006TSW's, was that when fitting the extractors for the .40's it was sometimes best to file the extractor's adjustment pad so the Go end of the gauge fit tightly, instead of even a little bit loosely. It did solve an issue with a 4006 that was exhibiting some FTE's even with a new extractor and spring. (We're talking about the difference of a single file stroke, at times.)
I also had a new production 4006TSW that was exhibiting FTE's with duty ammo. When I pulled the gun and got out the force dial gauge I discovered the extractor tension was too light, falling about half a pound below the recommended range.
I replaced the stock spring with a new "standard" extractor spring of the same tension (thinking the original spring might just have been bad), and got the same too-light tension reading on the force dial gauge. Apparently, the spring hole was slightly "off" on the generous end of the tolerance range (too deep?) The next heaviest spring was tried, which put the tension up within the desired range, and the gun ran as designed and expected.
I had a Value Line 411 brought to me that had a chipped extractor and a light spring tension. (I suspected someone had tried to "polish" it and had damaged the hook.) It had a color-coded extractor spring I'd not seen, so I called the factory. They asked for the serial number (?), explaining that the slide mass for that particular model had been changed during a run of those older guns, and based upon the serial number they told me which spring that particular .40 would probably require. That was the only extractor spring I
didn't have in my parts drawer, of course, so I ordered a couple of them. (While waiting for the springs to arrive I fitted a new extractor and tried some of my other springs, none of which got the gun extracting normally, so they were obviously right about using the specific spring for that gun.) The "stock" spring they recommended for that particular .40, with the newly fitted extractor, got the gun back up & running.
Bottom line? Sometimes even with the right tools and parts the hard-recoiling .40's can be a bit of a balancing act when it comes to fitting an extractor (filing the adjustment pad) and selecting the right spring needed for
that particular gun.
If you look at the parts lists for the different .40's (older 3rd gen and then the TSW's) you'll see that some guns have a couple of extractor springs, and the TSW's can have 3 springs listed. I've been told that the first spring listed is the standard production spring, but the next 1-2 springs might be required for any particular gun. Also, sometimes changing ammo (going from 180gr loads to some of the harder recoiling 155gr loads, for example) might require a change in extractor tension. Depends.
Then, they've also revised the .40 extractor over the years. Looking at them in 3rd gen guns of different production vintage might fool someone into thinking something's "wrong" with an extractor because of the shape of the hook and how it may appear compared to one of a different vintage. The current extractors have a very nicely beveled angle underneath the hook. This pic shows how the hook is beveled. (This is also the extractor used in the standard SW1911's, BTW.)
I wouldn't bother replacing an older designed extractor with a new one as long as a particular gun was running normally. If it works, it works.
It's pretty uncommon to find an extractor that "drops in" when you're talking about 3rd gen guns. The extractors were made to have extra metal at the adjustment pad and have to be filed and fitted. The older slides had looser tolerances in the extractor recess, so the extra "meat" on the adjustment pad gave an armorer more room for fitting an extractor among guns with older tolerances.
In my last 3rd gen pistol armorer recert we had a roomful of armorers using newer production 5906TSW's and new parts. In ONE of the guns (mine) a new extractor dropped in and gauged within proper tolerance. The instructor said he'd seen that happen a couple times in recent classes, and opined the newer tolerances in the latest guns and parts was responsible. Said it was still an unusual thing to see happen, and extractors still typically required filing & gauging.
In my previous classes over the years the extractors had always required anywhere from a little to a lot of filing in order to get them to fit in guns within normal spec. Fitting extractors isn't often a "favorite" activity of the average armorer, and some would rather leave it to other armorers or the factory.
