I decided to try the ISMI springs in my 1911 guns. I have an SDM fabricating spring tester(can be bought thru Brownells) that I use to test my 1911 springs. I tested about 4 new ISMI springs and found them to be very inconsistent with respect to spring tension at normal compressed length and also at full compressed length. The ISMI springs also needed to be shortened slightly because they were all about one or two coils too long at full compression.If you use a shock buffer, they most always need to be shortened. Springs rated at 18 lbs. actually tested more like 11 and 12 lbs. I returned them and got ISMI 20 lbs. springs. I tested these and they barely tested at 18 lbs. I decided to not use ISMI any more based on the fact that you just have no idea what the spring rate of the spring actually is straight out of the bag unless you test it, and there is also no way of knowing if the spring is too long unless you test for this as well.
On the other hand, I have done the same test with dozens of Wolff springs and they all tested very uniform and they come in the correct length without having to be shortened. This I feel I can count on without checking them every time I buy one.
Wow, now we have 2 opposing opinions. FWIW, a well known pistolsmith reported the same thing about testing them and finding they were not nearly the poundage? they were supposed to be. At least I think thats what he said. I was hoping it was an isolated incident. This is puzzleing because I have the ISMI springs in 2 Glocks and really love them. In the Glocks, I would not go back to Wolffs, even if they were free. Been there, done that. Of course, in fairness, I should say the ISMI Glock springs are flat wire, and the Wolff Glock springs are round wire, and they are different animals. Back to the 1911 springs, I don't have a spring tester, so it's a crap shoot if I buy one. Wolff or ISMI,,,,,,,,Wolff or ISMI,,,,,, Oh, crap I just can't decide. They are cheap, so I'll get 1 of each.
ISMI will warranty their recoil springs for 1 year no matter how many rounds you have fired with them installed.I have been trying one out in a Gunsite Pistol built on a Caspian slide and frame.I have 3000 rounds on the spring and it still measures almost the same length as a new spring.Contact Marc at ISMI he will answer all of your questions.BILLG.
I too use ISMI springs in Glocks, but I believe the Glock springs are a different deal because they are a flat wire spring. After my experience with the ISMI 1911 springs, I personally don't feel I can trust them in a 1911.
I used Wolff 17# springs for a couple of years, was completely satisfied with them, but changed to an ISMI 16# last year. I use a Shok-Buff, and had to shorten the spring by two coils to get proper fit. I have no way of testing the rate, but the gun has operated perfectly for ~3000 rounds. I spoke with Marc on more than one occasion, and was convinced that his theories on spring design, etc. had some merit. I tried his product, and I'm happy with it.