"Clipping coils" on Airgun Springs

[TwiceHorn]

You see references here and there on this forum and elsewhere to "clipping coils" on a spring to change its length or preload.  With certain springs, like the usual trigger spring, the spring is of light wire and the clipping is easy and the end of the spring is soft enough to be "flat" without further work, or it's easy enough to pinch the last couple of turns to get the "spring end" effect.

On some of the stouter springs, like the valve spring on a 39x, clipping a coil and flattening or "finishing" the resulting spring end doesn't really take care of itself.

Any tips or tricks to "clipping coils" that you folks would be kind enough to pass along?  "Don't do it except on really light springs" is an acceptable answer.   

The reason I ask is that I intend eventually to do the "two-spring" or "ICV" valve mod to a 397, and it has either occurred to me or some instructions say to clip the valve spring to a shorter length.

[WECSOG]

I did that mod to a 392, and just used a cutoff wheel in a Dremel to shorten the spring and flatten the cutoff end. Worked fine.
BTW, a number 10 brass washer works perfectly to separate the modified poppet spring from the new check valve spring. I found those washers at Lowe's.

[B67]

I have found that on heavier springs, heating to red hot and flattening works I have quenched some and not others. I quenched to stop heat transfer. I don't know that it matters in a general sense. After flattening,  grind and polish for a nice bearing surface...

[Motorhead]

Once springs get wound with tight coils either end, cut off and then tempered .... CUTTING COILS done with a cut off disk.  It is not possible to rebend coils into a flat stacked end once again.
The CUT end best fitted onto the guide end and NOT into the piston end where it will CANT when compressed.

[TwiceHorn]

Good point Scott.  I thought about editing to exclude powerplant springs.  I was mostly referring to the various valve, hammer, and trigger springs we encounter doing other mods to our rifles, where occasionally you see "just clip a couple coils."

[hank hill]

sometimes i just put the spring over shank of screwdriver and smush until it at the desired length. go slowly so you don't have to stretch spring back out, increasing fatigue