Gauging Recoil Spring Space

[niemi24s]

Conventional wisdom (?) has it that a 1911 recoil spring is compressed to 1 5/8" at full recoil, and this distance is used (at least by Wolff) to establish a springs rating. But, how much room actually exists in an an individual 1911 for the recoil spring? 1.625"? More? Less?

If (for some bizarre reason) you really must know, here's a doo-dad (gauge) that will let you measure it - and do it fairly accurately:

http://i129.photobucket.com/albums/p232/niemi24s/P085070003c.jpg
The telescoping brass tubing is produced by K&S Engineering and is available in most well-stocked hobby shops. Cut the tubing with a fine-toothed (say, 48tpi) razor saw and dress the ends nice and square. Deform one end of the smaller tube like in the pic for a good snug fit - but not so tight it can't be moved back out to reset it.

Set the gauge to maybe 1¾" and replace the recoil spring with it and reassemble the gun. Move the slide back to the full recoil position, remove the gauge and measure it's length - presto, the space for the spring in your gun.

[ElrodCod]

I find it easier to just check that the spring doesn't stack in the gun. Remove the plug, spring & guide; reinstall the slide & pull it all the way to the rear. Make a witness mark on the frame & slide with a soft pencil. Use masking tape if you don't want to mark the gun but a soft pencil won't hurt it & it'll rub right off with your finger. Assemble the gun with the plug, spring & guide; pull slide all the way to the rear. If the witness marks line up you're good to go. If it comes up short , you might have to clip a coil.

[niemi24s]

I find it easier to just check that the spring doesn't stack in the gun.
I also find that easier. But, that doesn't tell me how much room there is in a gun for the recoil spring (i.e., 1.615 inch).

Remember I said "If (for some bizarre reason) you really must know . . .".

I guess you could say I'm a bizarre kind of guy!:)

Cheers

[log man]

I find it easier to just check that the spring doesn't stack in the gun. Remove the plug, spring & guide; reinstall the slide & pull it all the way to the rear. Make a witness mark on the frame & slide with a soft pencil. Use masking tape if you don't want to mark the gun but a soft pencil won't hurt it & it'll rub right off with your finger. Assemble the gun with the plug, spring & guide; pull slide all the way to the rear. If the witness marks line up you're good to go. If it comes up short , you might have to clip a coil.

Elrod, If you don't have the rod in place when you make your witness mark you will not get an accurate comparison as the dust cover hits the rod head.

niemi's is a functional way of determining the actual space that the spring has at full compression during recoil. This space can also be measured with the depth rod on your calipers and is from the back of the dust cover to the shoulder the spring registers on in the plug.

LOG

[ElrodCod]

Elrod, If you don't have the rod in place when you make your witness mark you will not get an accurate comparison as the dust cover hits the rod head.

niemi's is a functional way of determining the actual space that the spring has at full compression during recoil. This space can also be measured with the depth rod on your calipers and is from the back of the dust cover to the shoulder the spring registers on in the plug.

LOG

Yes, you are correct. The spring guide should be in the gun when making the initial witness mark.

[niemi24s]

This space can also be measured with the depth rod on your calipers and is from the back of the dust cover to the shoulder the spring registers on in the plug.
Great idea! :appld: Why didn't I think of that? :butthead:

Another thing I didn't think of was the need for making a notch to clear the little pushed-in tab on the plug. Forgot about it because the gun used for most for this stuff has its plug tab poked back flush with the outer surface.

[Darn tab did nothing but prevent a good vigorous launching of the plug anyway! :)

Cheers

[Hill]

Niemi,
I've got a depth micrometer with rods to measure from 0 to 12" but more often than not I use one of my digital calipers with a foot on the tail end that I bought at Enco for about $10. It turns any cheap dial or digital caliper into a depth mic and you don't have to take it off to use the jaws for other measurements.

Have you seen what I'm talking about? If not I'll go chase down a link to one or phot my own for you.

[niemi24s]

Hi Hill: I do have a depth mike with rods for up to 6". I've seen the caliper adapters for depth measurement, but don't have one.

I tried Log Man's method in Post #4 with some success. The biggest proplem is sensing where the plug wall transitions into the conical end while the plug's in the slide. This is with a Mitutoyo slide caliper with a round wire depth rod that's got a nice sharp edge - just like a depth mike.

It's easier (for me, at least) to sense with the plug removed, but then you have to measure a bunch of other stuff and do a bunch of arithmetic to come up with the answer.

The fly in the ointment in all this is the uncertainty about exactly where the end of the spring is really located inside the plug at full recoil. If the plug end was flat on the inside there'd be no uncertainty. But it's conical, and creates an "iffy" footing for the spring.

This may well be one of those dimensions which is both unknown and unknowable - and an intelligent estimate is the best anybody can do.

Cheers

[log man]

Hi, niemi, it's not iffy to determine the shoulder the spring registers on with a FLGR plug as it has a square corner. :)

LOG

[Hill]

If the spring used is also conical at one end's last coil, that's the end that should be to the rear away from the plug, right? So the other broader coil would have to do unnatural things in order to get any further than the high side of the cone in the plug. I'd doubt many go any further than that.

But, you know what? I'd never looked into one of the plugs until you brought this up and assumed it was flat in there.

Speaking of unnatural things, how is it that you discovered the cone shape in there? Are you, umm, in a medical profession? ;)

[niemi24s]

. . . it's not iffy to determine the shoulder the spring registers on with a FLGR plug as it has a square corner.
Gadzooks! You may be the first one to come up with an advantage for a FLGR!!:lm:

[log man]

There's two actually ,that, and the ability to remove the top end by only removing the slide stop. :D

LOG

[Hill]

Bill Wilson can list some more. In his autobiograhical "The Combat Auto" he claims many virtues of the FLGR.

It's one of the few things he credits to someone beside himself.

[niemi24s]

If the spring used is also conical at one end's last coil, that's the end that should be to the rear away from the plug, right?
That's my understanding, so the closed & crimped end fits nice & tight on the guide rod to prevent launching them.
So the other broader coil would have to do unnatural things in order to get any further than the high side of the cone in the plug. I'd doubt many go any further than that.
Not sure, myself. There's around 0.020" difference between the spring OD at its open end and the plug ID. When the plug's first put over the end of the spring 3 possiblilties exist before the spring's compressed during final assembly:

1. If the tab on the plug's been removed, the end of the coil would most probably find its way down about 0.010" into the conical end.
2. If the tab's intact and the plug and spring are "screwed" together, the end of the coil probably finds its way up against the plug wall and never gets down into the conical end.
3. If the tab's intact but the plug and spring are not "screwed" together, the end of the coil is well short of the conical end and anywhere from 0.020" away from or up against the plug wall.

Then, when compressed during final assembly, I think what might happen in these three situations is:
1. The spring's OD will increase during compression, but whether its end stays put in the cone or moves outward and backs out of the cone - I don't know. Don't even know howto find out!
2. The end of the spring probably stays in that location during assembly and subsequent firings.
3. Don't have any idea what happens here. Don't even have a plug with an intact tab to experiment with and find out. Some folks I know don't even screw them together, but the first slide racking or firing would, I think, pop the spring over the tab - and the end of the coil could end up anyplace from maybe 0.010" into the cone to maybe against the plug wall on the verge of entering the cone.
I'd never looked into one of the plugs until you brought this up and assumed it was flat in there.
Perhaps some are flat. Mine are conical, like in the Army bluprints.
. . .how is it that you discovered the cone shape in there? Are you, umm, in a medical profession? ;)
Umm, nope!:D

Cheers

[1911Tuner]

Measuring...if you must know...is a good thing. You only know what you can measure, or so 'tis said. But...one gun isn't representative of the whole...so each one must be measured precisely in order to determine the dimension. Important only if you're trying to stuff every fraction of a spring that you can get into the system, and still leave enough space to prevent the spring stacking into solid coil bind. Why that would be a desideratum is open to speculation, and the simplest way to do it is to simply get an overlength spring and clip it a quarter-coil at a time until the binding is gone...and clip an extra quarter-coil...just to be on the safe side.

Tough to do with a 5-inch gun, since the operational length and number of active coils is predetermined. Commanders...true to Colt's design Commanders and clones...are more "tuneable" in that aspect. Most will function quite well with a standard 16-pound spring, clipped to 24.5-25 coils. Some seem to like the 14-pound spring and 25-26 coils...or whatever number that an individual pistol will accommodate.

Colt goes with the 16-pound spring, trimmed to 23.5 coils...which is better when a bit more working length is added...even if you have to drop to the 14-pound spring. Going below the 14-pound mark is best left to those who want to use attenuated ammunition. Slide to frame impact stress is still a factor, and there's a limit as with anything else. Many people will switch to the 14 pound spring for carry and the slight reduction in the sharpness of felt recoil...and use the heavier one for range and practice.

At one time, ISMI offered the standard springs with 34 coils. I don't know if that still holds true, because the last ISMI springs that I ordered were 18-pound with 30 coils of .0445 diameter wire. Installing them in identical guns in a side-by-side comparison with Wolff 16/32 coils springs proved difficult to feel any difference in hand-cycling or in live firing. The only real difference noted was a little shorter ejection...maybe a foot...and a slight difference in the felt recoil. Clipping them to 25 coils and installing them in a Commander offered a more telling difference. The advantage is that they last about twice as long as Wolff springs...though at twice the cost, it's 6 of one/half dozen of the other. For Commanders that will only see +P ammunition, that may be the best way to go.