Hi Ted! Glad you asked!!
Great question! I'll try to give you a rundown on whats occuring during the (sometimes really short!) life cycle on these spring types!
First of all they all start pretty much the same, as far as free length, wire diameter, and number of coils. You generally can change the compression rate by changing the wire dia. or the number of coils over a given length. The original designers have this pretty much nailed down in their specs, and a mint condition original spring is usually correctly matched to the specific purpose it was designed for...
The problem is, many, many, if not most of the original springs have been clipped to try to solve perceived mag. problems, related to feeding and function problems in the Luger pistol over the last 90 years! Also, there is a slight variance between many of the original springs in wire dia.. So some mag's springs are soft on compression, and some are stiff! BUT, They all (original springs) generally exhibit a fairly consistant, high quality material, and here is where the REAL mag. function problems start!
The area in the magazine shell that is designed to contain the spring during it's compression cycle is approx. .450" to .460" in its max. capacity.. The spring design calls for a free length dia. from between .437 min. to around .440" to .445 max.... this allows anywhere form .015" to .020" clearance for the spring dia. gain during the spring cycle.... sounds fair enough... .015" usually is a pretty large tolarance for any moving assembly... Well, heres what happens... when you compress a NEW spring, two thing happen, the spring free length becomes shorter, and the coil diameter becomes larger... this happens in most all, if not all springs that are constantly and repeatedly taken to their design limits, this is called "taking a set"... A high quality spring will take a set, "break in" and then will change very little over its life span, generally, before it digresses much further, it'll break, after thousands, if not tens of thousands, of full compression cycles! In competitive events of all kinds, involving machines that use springs, generally, you use a spring that has already taken a set, shim it to its original starting pressure and compete that way. So your not trying to tune a constantly changing component And, as in the situation concerning ALL after market mag. springs, they continue to grow all the way thru there SHORT life cycle! So every time you fully compress the mag. spring to get your full capacity, it is continually growing in dia, and becoming shorter, and weaker! As the spring wire quality is not up to the task at hand! So... it is usually within 20 to 30 full compressions, that the spring has grown to a overall dia. that totally uses up the designed tolarance designed into the assembly and you have severe spring drag, AND it is still getting worse as the spring continues to digrade! No end to the set!
When I designed my new springs, I took all of these factors into consideration! and I tweaked the original specs to accomplish the design parameters that I felt would be satisfactory...(no small feat in itself! These guys were pretty sharp!) and one of the goals, right from the start, was to eliminate spring drag!
So, I did three very critical things that all the other manufactures have either neglected or ignored... And they are,
1)I designed my springs to come into final spec. as they take a set! After 20 to 30 full cycles, my springs take a full set at approx. .437" THEN, THEY DON'T CHANGE! This is the min. free length dia. design spec,. that the print calls for!
2) I TESTED! I took all the springs and mags that I could get my grubby little paws on, and literally compressed them to failure... I then devoloped my own design parameters...that eliminated all the problems that arise from an inadaquate design....
3) I would ony accept the VERY BEST material available.... The spring company was set to run my springs on three seperate occasions. They would FED X overnight some samples to me, and I would spend all night testing the pre-production samples, with the intention of running the whole lot in the morning... THREE times, I rejectect the samples, which started us on a quest to find an adequate spring material that met with my standards! This cost me a $100 bucks each time they set up! Not to mention each time I made a change, the material cost doubled, as the quality improved!
Thats about it, when the new springs arrived, and after a short test, I was elated!! the springs were exactly as I had hoped! As good as, or better then, original! Now, "build a better mouse trap and the world will beat a path to you door!" Not Hardly! I have had very little interest in my new product! They are the very best, I know they are, and, I appreciate your question, letting me explain the "hows" and "whys" of my design philosophy! Best to you Ted, I look forward to filling your next spring order requirments! til...lat'r....GT <img border="0" alt="[jumper]" title="" src="graemlins/jumper.gif" />