Bel Air gets new spring and guide rod - Kimber Forum

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Old 07-20-2016, 01:35 PM   #1
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Bel Air gets new spring and guide rod

I am giddy with delight today.

I just received and installed my Kimber revised flat wound spring and new guide rod. From the photos one can tell this a completely newly designed spring over the old round wire spring. The oem is 8lbs. But the new version (on the right) is much more stout and, I am guessing, is closer to 12lbs.

The new rod (on the right) has a larger butt plate and is dished and shaped to saddle closely under the barrel, unlike the older oem design that was positioned further away.

I am trusting this revised design will eliminate those occasional FTbattery and FTL issues that I had experienced since the purchase of the Micro. Granted with time and about 500 rounds down the pipe, the failures diminished greatly, but I am looking for the Kimber quality and reliability as with their bigger 1911 brothers. We’ll see if I can now experience perfection.
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Old 07-20-2016, 02:06 PM   #2
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...now for the range report Donald, hope you'll get a chance to try it out sooner rather than later. I think you'll be happy :-)
...one thing I noticed is that one end of the new spring is a hair smaller in diameter. I've been positioning the smaller end towards the barrel lug. Not certain if it actually matters as they're so close but generally the smaller side goes on that end of the rod so...
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Old 07-20-2016, 04:01 PM   #3
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Old 07-21-2016, 03:24 AM   #4
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I too received the updated kit and once installed the pistol quickly gobbled up two boxes of Blaser Gold without a burp. My pistol had not experienced the problems Donald has but the new spring and guide gives me an extra amount of confidence in my every day carry.
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Old 07-21-2016, 10:10 AM   #5
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Lightbulb

Thanks for the positive comments.

I hope I can get to the range this weekend and enjoy the "new" Micro. I have been so busy this summer with other projects and time demands that I might have to wait until later.

I'll report back when I do. Also, when I get a chance I plan to compare the Sig P238 guide rod and the new Kimber guide rod and share photos together. They are now very similar with the dished butt plate (to no one's surprise) and may be interchangeable.
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Old 07-21-2016, 10:42 AM   #6
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How much does the new spring kit affect the slide pull back? The reason we decided on getting the Micro Carry was the how easy the slide pull was. My wife has arthritis in her hands so we had to find one she could pull back. Hers has been shooting okay so far.
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Old 07-21-2016, 12:12 PM   #7
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It's a "little firmer" I doubt mrs Markie will have a problem. Seems to be a legitimate improvement.
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Old 07-22-2016, 09:07 AM   #8
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Originally Posted by Markie View Post
How much does the new spring kit affect the slide pull back? The reason we decided on getting the Micro Carry was the how easy the slide pull was. My wife has arthritis in her hands so we had to find one she could pull back. Hers has been shooting okay so far.
Just how much is subjective, but I am going to guess about 50% stronger racking effort. The reason is that the oem spring is 8# and the replacement is, to my estimate, about 11-12#, ergo, a possible 50% increase in effort.

It doesn't cost you anything to install and trial the new spring and guide rod. So test and she how it works for her. If it is too strong go back to the oem set up.
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Old 07-24-2016, 03:11 AM   #9
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I have not utilized a scale to determine difficulty with pull however i would suggest a slight increase in effort but the Micro has and always has had the slickest movement going.
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Old 07-24-2016, 02:25 PM   #10
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Originally Posted by Donald View Post
I just received and installed my Kimber revised flat wound spring and new guide rod.
Wow! That's a colossal difference. Springs are fascinating devices, so your picture caught my attention.

I don't have the gun or springs in front of me. I don't have measurements or specs. The following are just some thoughts as they flow from brain to fingers, so feel free to correct my thoughts where I go astray.

These are linear rate springs. They'd be measured in (x pounds/inch) of compression. Let's assume that the old spring is 3.5 pounds per inch. Slide movement compresses the spring 2 inches. When you install that short spring, you're compressing it .5 inch.

(2"+0.5")x(3.5lbs/inch)=8.75 pounds.

But the initial pressure holding the slide into battery is
(0.5")x(3.5lbs/inch)=1.75 pounds.

That's less than two pounds pushing that round into the chamber and locking up the mechanism. If any of the conditions are less than optimum, then 1.75 pounds might not be enough to overcome the problem.

Now lets look at the new spring. Let's assume it's a 2 pound per inch spring. How much do we have to compress that spring when we initially install it? Maybe 3.5 inches? Let's do some math.

(2"+3.5")x(2lbs/inch)=11 pounds

That's close to your guesstimate, Donald, and the same as the recoil spring in the Colt Mustang. But the big difference is the initial pressure holding the slide closed:

(3.5")x(2lbs/inch)=7 pounds

That's FOUR TIMES the force of the original spring, pushing that new round into battery.

Granted, the vast majority of the force stripping a new round from the magazine and chambering it, is the momentum of the slide. And that's affected by the friction of the rails, friction from excessive lubricant, excessively strong magazine springs, and a myriad of other variables.

These numbers are just made up, but you can see where I'm going with this, and probably why the boys and girls at Kimber decided to to make such drastic changes.
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