I appreciate your expertise and have read many of your posts especially on recoil spring rates.
My question is this:
I ordered a Wolff 18.5 conventional recoil spring for my brand new Colt NRM 1991. I have yet to shoot it but was a little afraid that shooing Corbon +P 165 gr. ammo at 1250 ft. per sec. would damage the frame. Not that I would shoot a ton of that be enough to get used to it because that's what my defense rounds is. Your formula comes out to be about a 19.5 lb. spring. Then I got worried that 18.5 would be to heavy for the rest of the ammo I shoot which is Winchester white box or other plinking rounds. So, I clipped a full coil off and smoothed the edge up.
Did I mess it up? Now the spring is about a coil or a little more shorter than the stock spring. Is that a problem?
Logic would dictate that each coil is worth the number of coils divided by the spring weight? 32 coils / 18 lbs. = .56 or about a half lb. So I cut off 1 pound and now have a 17.5 lb. spring?
Why would you cut a coil off of a new spring from Wolff? I know they make springs in a zillion weights... What was the thinking there?
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Then I got worried that 18.5 would be to heavy for the rest of the ammo I
shoot which is Winchester white box or other plinking rounds.
The Colts that I have handled that still had the stock spring in them seem a little weak and not a full 16lb recoil spring that I think is spec spring. You have to remember that if you put a heavier recoil spring in your pistol, it will reduce the amount of impact on your slide and frame with heavy loads, but will also speed up your slide going back into battery. As Tune will tell you, there is no free lunch. Higher the slide speed the stronger your mag springs have to be to keep up to feed right. I'd say as long as you got good mag springs, a slightly heavier recoil spring should not be a problem with target loads or WWB, but those Corbons, will give that gun a beating no matter what spring you put in it. I ran a few Triton Quickshock 165gr heart stoppers through a Springfield Champion, and looked like I had a flame thrower, poppin those off. GI mil surplus 230 fmj's is what I carry, and I don't feel under gunned.
Recoil springs were a subject that kept me awake nights for a time. The formula works well for most applications, but every gun... and load... is a law unto itself.
I've clipped a half-coil to a full coil off a spring in a fine-tune exercise... but it's generally not necessary, and I only used it in stubborn cases when I couldn't find the sweet spot with a standard spring. I have strong evidence that Colt has done so... and now it looks like Springfield has followed suit.
You're pretty close in your assumption that each turn of the spring contains an equal amount of tension, and that clipping a coil reduces that tension by a given amount... with a standard rate spring. With a variable, all bets are off. I've never used a variable, and can't comment on how they perform in a given situation or in a given pistol. Rule of thumb is: Use all the coils on a given spring that will let the gun shoot a full magazine to slidelock with the loosest grip that you can manage, regardless of the spring's load and rate.
The problem with shooting such a light, fast bullet in a 1911 is that the dwell time in the barrel is so far removed from design parameters, that you can't bet on how the gun will respond. The timing gets all fugazi, and some guns will do okay, while others won't.
The other part of the puzzle is: Are you sure of the velocity, or are you going by what's written on the box? Until you chronograph the load in question with a calibrated chronograph... you never know.
If I was a bettin' man, I'd lay odds that you'll find function with a stock spring with a 16-18 pound rating. If it turns out to be the lighter one, install a 25 pound mainspring in the gun to help slow the slide a little.
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Why would you cut a coil off of a new spring from Wolff? I know they make
springs in a zillion weights... What was the thinking there?
The 18.5 felt so much stiffer than the stock spring. So I compromised and I did care to spend another $12.00 on a spring.
Sounds like it's far from cut and dry and from an exact science. I'll try this Wolff spring and see what happens. I can always go back to the stock spring.
Not yet. Gonna try to get to the range tomorrow.
I have a real tendency to over-analyze these kind of things. I think I will resist the evil spirit and just shoot the snot out of the gun with the stock spring and solve any problems as they come.
Thanks for bringing me back to reality. I don't know what it was specifically, but something you said somewhere, or posted brought me back to earth on this issue.
There's a reason the phrase "let's cross that bridge when we get to it" has stood the test of time. I should abide by it more often.
We use a Wolff 16 1/2 VP (Variable Power) in our PATRIOTS. I feel this is about right for a variety of loads. I do not care about experimenting with springs, but I can understand the desire to experiment. I had pals who gave me a lot of work by using 22lb recoil springs and beating their 1911's to death. I prayed for these folks to keep up the good work! I have Wollf make me a special spring kit for these guns. So far, so good.
I've never used variable rate recoil springs, but it seems to me that they'd be a good way to control the slide to frame impact and minimize impact shock on the lower barrel lug and slidestop pin... just never got around to givin 'em a try.
Got a couple questions for Dave on variables...
When hand-cycling the slide, does a 16-pound variable feel lighter than a standard 16 pound spring just as the slide starts back? AND... at what point in the travel do you feel the tension start to increase? Mid-point? 2/3rds of the way? Near the end?
Might be time for this old dawg to learn a new trick. Now... what'd I do with that Brownells catalog?
To me, they feel like they are heavier than they are at the start with the slide forward and in battery. They also feel heavier at the end of the slide travel, too. They are easier in the middle, as near as I can tell. I think that the idea of them is to give you extra spring power where you need it and makes the stock spring weight more effective. They do not look any different than the stock 16 1/2 lb to me they they do feel different. Let me know if you want to try one of our custom spring kits and I will mail you one to try. I keep a few of these kits around here just in case.
Ahhhh... I see the concept now. Slow the slide just as it starts back to give the barrel time to drop.... faster in the mid-range, and puts on the brakes near the end. Makes sense. I had it in my mind that they were lighter until the end of compression... and also had a vision of progressively wider distances between coils near the back. Since this isn't the case... does the wire diameter change at different points on the spring?
I would like to see how the cycle speed and feel compares in a back to back test with a standard spring... Probably wouldn't take more than a magazine full per spring, and I'd get it back to ya in 7-10 days, dependin' on when I could arrange a range trip.
Hell... my coil cuttin' days may be over!
I've got 16.5 and 18.5 variables here, but haven't had a chance to do anything except hand-cycle with'em. They do indeed seem to vary, with a lighter than standard (for the rating) pre-load, and get stiffer as the slide moves. I'll probaby get a chance to see how they do next week.
Report comin' soon to a forum near you!
Try the ISMI 16# or 18# springs - you won't be sorry. Because they are made from "real" silicon chrome spring material and properly heatreated, not music wire, they have a longer length and they keep it so the in battery force is higher but the final force is lower. The energy absorption is the same and they stay that way for thousands of rounds. Also, if you really like replacing recoil springs frequently, the Wolff 17# conventional spring is I believe the closest to the original Browning spec.
A word of warning on ISMI springs... They're longer because they have about 3 more turns than Wolff, and they often need to be trimmed to length in some pistols to prevent coil bind... Coils stacking up into a solid before the slide is stopped by the frame and guide rod head... which will destroy the bushing and can damage the slide beyond repair.
Cardinal rule is to always check for coil bind whenever the recoil spring is changed in any gun... ANY recoil spring.
Another thing that I've noticed about ISMI springs is that they vary as much as +/- 2 pounds in their compressed loading, whereas Wolff springs hold the tolerance much closer... about a half-pound in either direction. ISMI springs are very good, and last for a long time... but if you're tuning to a specified preload and compressed loading, sometimes you have to try several before you hit the right one.
Marc at ISMI told me that the "16#" spring is 32 1/2 turns of .044 wire and the "18#" spring is 30 1/2 turns of .0445 wire. I measured mine and they agree with what Marc told me. It is my understanding that the original Browning spring was 32 1/2 turns of either 044 or 045 wire. In either case, if the gun will take a "stock spring" it should take an ISMI spring that is to spec. ISMI makes several other 1911 springs. I don't know anything about them.
Since a music wire spring is usually assumed to have a useful life of 2000- 3000 rounds and since during that lifetime it continually grows shorter, I fail to see how minute tuning of the spring would last long enough in service to be useful (except for adjusting for coil bind).
There is a useful explanation of variable power VS conventional power recoil springs in the last page (FAQ section) of the Wolff catalog.
The catalog is usually free if you ask with a decent order and has a wealth of good info IMHO.
I believe the discusion of variable vs regular springs is also on the Wolff website. One of the original reasons for variable rate springs was for compensated guns that had trouble unlocking properly with standard springs.
DBR said:
Marc at ISMI told me that the "16#" spring is 32 1/2 turns of .044 wire and
the "18#" spring is 30 1/2 turns of .0445 wire.
Ah! They've changed a little. The last ISMI 16-pound spring that I bought had 34.5 turns and the wire diameter was .043 inch... An 18 pound spring had 34 turns and was .045... Interesting. Wonder why they changed recipes...
Thanks for the update... I haven't used ISMI springs in about 3 years or so.