Kimber Ultra Carry II Recoil Spring.

Organic · March 3, 2010, 11:44 AM

I’ve read here and there that one should consider using a heavier recoil spring if the intention is to shoot +P ammunition. The spec sheet for my Kimber UC II states that my stock recoil spring is rated at 18 lbs. To avoid a wall of text I’ll enumerate my questions below.

1) Is 18 lbs sufficient for very occasional use of .45 +P ammunition, or should I go ahead and step up to a heavier spring?

2) The recoil spring assembly incorporates two separate springs, but I have only seen outer springs for sale. Am I correct in my assumption that the outer spring is the only one that needs replacing, or have I simply missed something?

3) If I do change to a heavier spring, be it just the outer or both inner and outer, would there be any necessity to revert to a lighter spring when firing standard pressure rounds?

Thank you in advance for suffering my ignorance. Handguns are a new beast to me and I clearly have much to learn.

88KEYS · March 4, 2010, 01:45 AM

I know people have different views, just will say have been shooting for many years, loading over 25, and do minor gun work. I carry the Kimber CDP 4”, it has the Officer Size grips makes a good carry gun.

I tend to load even practice stuff on the warm side and run a spring with more then stock weight. I use shock buffs for practice not carry with +p that is if the gun functions properly. I have a 1911 9mm Springfield with a 9lb spring, put in 12, and it runs fine.

I have not owned a gun with the dual springs but my answer would be, if you shoot stiff ammo, add some weight. That is that as long as it feeds fine.

My 2 cents

Organic · March 4, 2010, 09:39 AM

Thank you for your input, Keys. I suppose there will be some trial and error on my part, figuring out how the weapon functions with a new spring and various loads.

orionengnr · March 6, 2010, 10:09 PM

Someone will correct me if I'm wrong, but I believe a Gov't Model uses a 16-18 lb spring.
A Commander size maybe 20 or so, and the 3"ers use (IIRC) a 24 lb spring.

Check with Wolff springs as they sell springs for everything.

Clark · March 7, 2010, 12:02 AM

The ejected cases should land ~ 5 feet from the shooter.
There may be some competition shooters that want lighter springs than that, but 5 feet balances reliability with reducing felt recoil and reducing wear on the pistol.

What I wrote in 2003
http://groups.google.com/group/rec.g...556962794e57bd

Quote:

1) For a semi-automatic case fired 5 feet form the floor, the time to
reach the floor is
t= square root ((2)distance / acceleration )= root (5'/32'/sec/sec)= .54 seconds

2) In a Colt .45 the ejector contacts the case when the slide is back
1.3". The farthest the slide can travel is 1.8" where it hits a stop. If

the spring is perfectly sized for the gun and the round, then the slide
will just run out of energy at the stop. Assume Vslide = 0 at 1.8".

3) Energy Slide at 1.3 inches = (force) (distance)= (16lb
spring)(1.8-1.3=.5")=.66 foot pounds of kinetic energy left in slide
when it hits the case

4) Energy is also = 1/2 mass velocity squared = .5 (mass of slide=
weight of slide/ grav accel=12 oz/32 ft/sec/sec)(V squared)

5) Combining equations 3) and 4): Vslide at 1.3" = square
root(E/(.5mass)) = root(.66 ft lb/((.5)(.023 lb sec sec /ft)) = 7.6
feet/sec

6)Center of gravity [this should be moment of inertia, but that would be
work] is .25" from extractor claw and ejector hits the case at .35" from the extractor claw.
Velocity of case = (.25"/.35") velocity of slide at 1.3" = (.25/.35)7.6
feet/sec = 5.4 feet per sec = 3.6 miles per hour

7) Combining 1) and 6): Distance case travels=
(Velocity)(time)=(5.4ft/sec)(.54 sec)=2.9 feet horizontally from the
gun

And Wolff FAQ wants your empties to land from 3 to 6 feet. They must
want the slide to barely hit the stop.
http://www.gunsprings.com/1ndex.html

45Gunner · March 7, 2010, 08:07 AM

Most full sized 1911's are designed to use a 16# spring. However, whenever I order springs, I always order both the 16# and 18.5# springs and try the heavier spring in my gun first. In most cases I find the gun to cycle snappier and feel better. There are those that would say I am accelerating the wear on the pistol. One of my Kimbers has well over 60,000 rounds fired with the heavier spring and the gun looks like new. And...if something did break, I would replace/repair it. I'm very happy with the performance.

Organic · March 9, 2010, 11:05 AM

Thank you all for bringing great advice to my ears (metaphorically, of course). As suggested I have searched out a Wolf spring set that will, hopefully, do the trick.

As a new member to the forum I must say I am delighted to find such a receptive and knowledgeable community.

March 3, 2010, 11:44 AM	#1
Organic Junior Member Join Date: February 10, 2010 Posts: 12	Kimber Ultra Carry II Recoil Spring. I’ve read here and there that one should consider using a heavier recoil spring if the intention is to shoot +P ammunition. The spec sheet for my Kimber UC II states that my stock recoil spring is rated at 18 lbs. To avoid a wall of text I’ll enumerate my questions below. 1) Is 18 lbs sufficient for very occasional use of .45 +P ammunition, or should I go ahead and step up to a heavier spring? 2) The recoil spring assembly incorporates two separate springs, but I have only seen outer springs for sale. Am I correct in my assumption that the outer spring is the only one that needs replacing, or have I simply missed something? 3) If I do change to a heavier spring, be it just the outer or both inner and outer, would there be any necessity to revert to a lighter spring when firing standard pressure rounds? Thank you in advance for suffering my ignorance. Handguns are a new beast to me and I clearly have much to learn.

March 7, 2010, 08:07 AM	#6
45Gunner Senior Member Join Date: August 8, 2009 Location: Boca Raton, FL Posts: 1,557	Most full sized 1911's are designed to use a 16# spring. However, whenever I order springs, I always order both the 16# and 18.5# springs and try the heavier spring in my gun first. In most cases I find the gun to cycle snappier and feel better. There are those that would say I am accelerating the wear on the pistol. One of my Kimbers has well over 60,000 rounds fired with the heavier spring and the gun looks like new. And...if something did break, I would replace/repair it. I'm very happy with the performance. __________________ May the Schwartz Be With You. NRA Instructor 45Gunner

March 4, 2010, 01:45 AM	#2
88KEYS Senior Member Join Date: January 21, 2010 Posts: 145	I know people have different views, just will say have been shooting for many years, loading over 25, and do minor gun work. I carry the Kimber CDP 4”, it has the Officer Size grips makes a good carry gun. I tend to load even practice stuff on the warm side and run a spring with more then stock weight. I use shock buffs for practice not carry with +p that is if the gun functions properly. I have a 1911 9mm Springfield with a 9lb spring, put in 12, and it runs fine. I have not owned a gun with the dual springs but my answer would be, if you shoot stiff ammo, add some weight. That is that as long as it feeds fine. My 2 cents

March 4, 2010, 09:39 AM	#3
Organic Junior Member Join Date: February 10, 2010 Posts: 12	Thank you for your input, Keys. I suppose there will be some trial and error on my part, figuring out how the weapon functions with a new spring and various loads.

March 6, 2010, 10:09 PM	#4
orionengnr Senior Member Join Date: July 9, 2004 Posts: 4,865	Someone will correct me if I'm wrong, but I believe a Gov't Model uses a 16-18 lb spring. A Commander size maybe 20 or so, and the 3"ers use (IIRC) a 24 lb spring. Check with Wolff springs as they sell springs for everything.

March 9, 2010, 11:05 AM	#7
Organic Junior Member Join Date: February 10, 2010 Posts: 12	Thank you all for bringing great advice to my ears (metaphorically, of course). As suggested I have searched out a Wolf spring set that will, hopefully, do the trick. As a new member to the forum I must say I am delighted to find such a receptive and knowledgeable community.