Can a recoil spring be too light?

[srf]

When a 1911 is in battery the breech is locked. The slide and barrel are one. When the gun is fired it stays locked until enough energy is bled off to allow the slide and barrel to unlock. The recoil spring does little to retard this unlocking. The fit of the barrel feet is way more important to locking and unlocking. Damage that occurs in pistols with light recoil springs can usually be attributed to a misfit barrel and/or misfit at the impact bridge of the frame . I run a 9lb spring in STI 40. The pistol has well over 100k rounds through it, mostly with 9-11 lb recoil springs. I've had it re-barreled three time by the different reputable 'smiths and replaced three or four sets of sights. It's a little looser now but it still chews 'em up and spits 'em out 100% of the time. I've had the opportunity to pick the brain of a big-time GM about recoil spring voodoo. He runs his recoils as light as feeding the next round in the mag will allow. If your barrel if fit properly - I say run 'em as light as you like the feel of the pistol, and as 100% function allows.

Edited January 9, 2009 by srf

[JD45]

That is a point I've been wanting to bring up. I'm not a gunsmith and know very little about the firing cycle of a 1911, but I do know that it fires from a locked breech. Most of the talk about guns getting beat to pieces seems to be assuming that the pistol is a blow-back design, like the frame is being hit with 100 percent full force.

Maybe a good gunsmith could explain what actually happens during the firing cycle of a 1911 and we will see things more clearly.

[HSMITH]

The 1911 never locks until the pressure in the case pushes the barrel forward and the slide back locking them together, a MINOR detail, but technically correct.

Each impact does some damage, but I related it to tapping an anvil with a small hammer. Yes, it will wreck the anvil, eventually......

Think about it this way, say I took a frame and welded a block of steel on top that was the same approximate weight and balance as the upper assembly. I put it in your hands and you take your firing grip. The first impulse of the recoil when the slide starts to move and cock the hammer is the initial sight lift, when the slide bottoms out on the frame you see the second impulse (high speed video shows this well). Now, if I took a hammer that was the same weight as the reciprocating mass in a normal gun, how hard would I have to hit the block of steel to move the gun the same amount as you see in the second impulse compared to what it does when firing normally? Given the mass involved and the amount of movement I will barely be able to tap it without creating more movement than what happens in actual firing.

If the recoil surface in the frame is square and flat, the slide dustcover is square and flat, and the guide rod head is square, flat and fitted correctly you will not be beating the frame or the slide up. It is not uncommon at all to have a decently built gun run 100K rounds on the same frame and slide, not even with light springs. Lighten the slide and you lighten the 'hammer', so you can hit even faster with the same amount of energy when it impacts. Put in a bull barrel and you increase the mass that must be moved to start the slide motion robbing energy from the slide, so it hits softer again. Given that we can run light springs without hurting anything in a well built gun, if we take energy from the slide by one or more of these other methods we can go really light with the springs and not have problems.

Cracked slides are the result of: Bad slide (heat treat, material, etc, poor fitting, improper lightening, or combination of the others and I am sure some other defects that I am not thinking of at the moment. Same goes for frames, frames and slides just don't fail when everything is of good quality and correctly put together.

[Patrick Sweeney]

Close, Duane, but you've mixed up two tests Ned did. The long-term one was a rig to "Bubba-load" an extractor. You know, drop a round in, then drop the slide closed. The totals were 60,000 mechanical test rig cycles on an extractor (Wilson, if anyone cares, in a CQB) that I'd already shot 30,000 times.

The other was test-firing a 1911 sans recoil spring. No damage, no measurable change in the slide.

For those who care to know, the cycle goes something like this:

Gun fires, bullet exits the muzzle, and the ejected bullet and gases load the slide and parts with potential energy. The slide and barrel move back, delayed by the hammer. The system has an appreciable amount of energy bled off by the act of dragging the barrel down out of battery, and pivoting the hammer. (Both poor-leverage events, from the slides point of view)

Once the barrel unlocks, the major work the system has had to do is done, and the rest is miniscule: friction of the slide and rails, friction of the case in the chamber and the disconnector drag.

If we assume 32 fps is the max, then I'd estimate that the slide without recoil spring hits the frame in a government model at about 15 fps. (Based on my estimate of slide movement from high-speed movie footage.)

I wouldn't want to make a habit of it, but if all I had was a 1911 lacking a recoil spring, and an excess of bad guys swarming over the wall (or through the wire) I'd certainly let them have it with great gusto.

Shoot what feels good to you.

[Raudi]

BTW, does anybody know, how long a recoil cycle takes on a 1911? That information might lead as closer to a realistic slide speed...

[Tom S.]

Close, Duane, but you've mixed up two tests Ned did. The long-term one was a rig to "Bubba-load" an extractor. You know, drop a round in, then drop the slide closed. The totals were 60,000 mechanical test rig cycles on an extractor (Wilson, if anyone cares, in a CQB) that I'd already shot 30,000 times.

The other was test-firing a 1911 sans recoil spring. No damage, no measurable change in the slide.

For those who care to know, the cycle goes something like this:

Gun fires, bullet exits the muzzle, and the ejected bullet and gases load the slide and parts with potential energy. The slide and barrel move back, delayed by the hammer. The system has an appreciable amount of energy bled off by the act of dragging the barrel down out of battery, and pivoting the hammer. (Both poor-leverage events, from the slides point of view)

Once the barrel unlocks, the major work the system has had to do is done, and the rest is miniscule: friction of the slide and rails, friction of the case in the chamber and the disconnector drag.

If we assume 32 fps is the max, then I'd estimate that the slide without recoil spring hits the frame in a government model at about 15 fps. (Based on my estimate of slide movement from high-speed movie footage.)

I wouldn't want to make a habit of it, but if all I had was a 1911 lacking a recoil spring, and an excess of bad guys swarming over the wall (or through the wire) I'd certainly let them have it with great gusto.

Shoot what feels good to you.

Excellent post and description of what takes place when firing. I'm curious though, is the energy enough to cause the slide to rebound, chamber the next round and return the barrel/slide to lock up without a recoil spring?

[HSMITH]

Not even close, if it does rebound at all it is a VERY short distance.

[Tom S.]

Not even close, if it does rebound at all it is a VERY short distance.

So how can people claim to be running guns with no recoil spring? Or am I missing something (not the first time!)?

[HSMITH]

The test was reportedly done with something that pushed the slide back into battery.

[Patrick Sweeney]

Yes, Ned's thumb.

I've had occasions to listen to a bunch of machineguns over the years. And a couple of 1911s that were runaways. I'd put the 1911s in the same category as a hot-running MG-34 or a new and tight MG-42 with soft ammo: 1100 rpm.

Anyone who wants to calculate slide speed using those is free to crunch the numbers.

[HSMITH]

The 1100 rpm figure you put forward is right on with the cyclic numbers I have observed in my testing of 1911's also.

[BSeevers]

Mine cycles at 1111.

I use 7 or 8lb in Open guns, 9 or 10 in Limited and have shot 100's and 100's of thousands of rds and no cracks. Assuming you use "the good stuff" the pistolsmith makes all the difference. I have seen slides/frames crack, lugs break off, top and bottom, and its because of the improper fit.

Or spring weight doesn't matter if everything else is correct.

Shok buffs are optional and I like the feel of them. Its a good gauge to see if you have a problem. Shredded buff means problem.

[Raudi]

1100 rpm would mean approx. 6fps average slide speed over the recoil cycle. I assume that the slide opens faster, than it closes and further assuming that the speed of the slide is relatively uniformt ,hat gives us a good minimum. Anyway, given that 6fps is walking speed, the slide can't be that fast at the time of impact.

[ebg3]

I shoot an STI Eagle in 40 with a bull barrel and a round top slide. The gun has close to 200,000rds through the original slide, barrel and frame. The heaviest spring I've run is a 14lb variable(few years ago) and I currently use a 12lb progressive. Never used a shock buff. I shot a 13lb progressive for years and I think I'm going back to it. I'd be very upset not to get at least 100K out of a new limited gun before having to rebuild, regardless of recoil spring weight.

[XRe]

If you watch high speed vid, the slide is only moving for a part of the cycle time - it dwells to the rear for quite some time, relatively speaking.

In terms of slowing the slide's rearward motion, the radius on the bottom corner of the firing pin stop, the hammer geometry, the strut geometry, and the mainspring (all acting in concert) have more of an effect on rearward slide velocity than the recoil spring (who's name is somewhat misleading - the recoil spring's real job is to close the slide, not slow down its opening...). It obviously has some effect - and it definitely has an effect on how much energy is transmitted to the frame and when - but for slide velocity, its not the only (and probably not the first) thing to look at.

Another thing is - the configuration of the FP stop, mainspring, hammer, and strut will also affect how the recoil spring factors into the feel and tracking of the gun What works in one guy's setup may work differently in another (that is, my 12# spring in my Trojan may feel entirely different in some other gun, because of those other factors... actually, there's even more to it than that, but...)

[Raudi]

If you watch high speed vid, the slide is only moving for a part of the cycle time - it dwells to the rear for quite some time, relatively speaking.

In terms of slowing the slide's rearward motion, the radius on the bottom corner of the firing pin stop, the hammer geometry, the strut geometry, and the mainspring (all acting in concert) have more of an effect on rearward slide velocity than the recoil spring (who's name is somewhat misleading - the recoil spring's real job is to close the slide, not slow down its opening...). It obviously has some effect - and it definitely has an effect on how much energy is transmitted to the frame and when - but for slide velocity, its not the only (and probably not the first) thing to look at.

Another thing is - the configuration of the FP stop, mainspring, hammer, and strut will also affect how the recoil spring factors into the feel and tracking of the gun What works in one guy's setup may work differently in another (that is, my 12# spring in my Trojan may feel entirely different in some other gun, because of those other factors... actually, there's even more to it than that, but...)

You are right about the dwelling time of the slide of course, this is why I quoted the figure as a minimum, not as an approximation.

But as to geometry: The geometry of the FP stop, hammaer, strut, etc can't change the amount of momentum that is transferred. The only difference from one geometry to another is friction, and I dare say, that the difference in friction is minuscule. Of course the geometry changes the feel, i.e. the moment and the timespan at which the momentum is transferred into the springs (in our case the mainspring). It's very much like using a pulley. The only thing that can really change the amount of momentum transferred into the mainspring is the strength of the mainspring itself.

So basically we only have 3 variables to get momentum/speed out of the slide before it is stopped by the frame:

- friction

- mainspring weight

- recoil spring weight

Geometry is not a factor, IMHO.

[rvb]

If you watch high speed vid, the slide is only moving for a part of the cycle time - it dwells to the rear for quite some time, relatively speaking.

In terms of slowing the slide's rearward motion, the radius on the bottom corner of the firing pin stop, the hammer geometry, the strut geometry, and the mainspring (all acting in concert) have more of an effect on rearward slide velocity than the recoil spring (who's name is somewhat misleading - the recoil spring's real job is to close the slide, not slow down its opening...). It obviously has some effect - and it definitely has an effect on how much energy is transmitted to the frame and when - but for slide velocity, its not the only (and probably not the first) thing to look at.

Another thing is - the configuration of the FP stop, mainspring, hammer, and strut will also affect how the recoil spring factors into the feel and tracking of the gun What works in one guy's setup may work differently in another (that is, my 12# spring in my Trojan may feel entirely different in some other gun, because of those other factors... actually, there's even more to it than that, but...)

You are right about the dwelling time of the slide of course, this is why I quoted the figure as a minimum, not as an approximation.

But as to geometry: The geometry of the FP stop, hammaer, strut, etc can't change the amount of momentum that is transferred. The only difference from one geometry to another is friction, and I dare say, that the difference in friction is minuscule. Of course the geometry changes the feel, i.e. the moment and the timespan at which the momentum is transferred into the springs (in our case the mainspring). It's very much like using a pulley. The only thing that can really change the amount of momentum transferred into the mainspring is the strength of the mainspring itself.

So basically we only have 3 variables to get momentum/speed out of the slide before it is stopped by the frame:

- friction

- mainspring weight

- recoil spring weight

Geometry is not a factor, IMHO.

It's a torque-arm relationship to cam the hammer. Shorter leverage arm (as in how far up on the hammer the slide pushes) results in less torque applied to cam the hammer and the slide will be somewhat slower. Change the geometry and you get a longer lever arm applied to the hammer which means the same force w/ a longer lever arm is more torque and the hammer cams easier and the slide retains more velocity. A bigger diameter on the bottom of the firing pin stop makes it easier to cock the hammer than a small diameter since that changes where the slide leverages on the hammer.

Your right that total energy/momentum is conserved in the springs, hammer, etc, but that doesn't necessarily mean final slide velocity is the same, either.

Just like a lug wrench on your car tire. You can put all your weight into it very close to the nut. Your momentum is conserved but that doesn't mean the wrench moves as fast or easy as if you hold it out as far from the lug nut as you can. So in a similar way, the geometries can effect how fast the slide move. How significantly? I dunno. I do know I could tell a big difference in dot tracking when I put a more square FP-stop in my open gun.

-rvb

Edited January 10, 2009 by rvb

[MLE-ShootingSports]

The recoil spring on my wife's 1911 had to be replaced and I decided to go with a lighter spring. This gun had a 17# spring and it worked fine but the boss wanted something that produced less perceived recoil with. I bought a 14# and a 12.5# and tried them both yesterday at the range. The 12.5# feels really nice and the sights track nicely but I could hear a metal "clang" with each shot. I then tried the 14# hoping that this would be the answer but I can still hear that metal "clang" when the slide recycles. I looked at the frame and slide and I was unable to see any marks on either of them (but then again, I only shot about 20 rounds total). (Pistol info: Springfield 1911 .40S&W shooting Major).

Is this noise normal with lighter springs or will it eventually cause damage to the gun?

My two cents: When in doubt, take the gun to a good gunsmith that will test fire your gun and advise you on the proper spring. Guns cost too much, to play around if you're not comfortable with the way it performs/sounds.

[Raudi]

If you watch high speed vid, the slide is only moving for a part of the cycle time - it dwells to the rear for quite some time, relatively speaking.

In terms of slowing the slide's rearward motion, the radius on the bottom corner of the firing pin stop, the hammer geometry, the strut geometry, and the mainspring (all acting in concert) have more of an effect on rearward slide velocity than the recoil spring (who's name is somewhat misleading - the recoil spring's real job is to close the slide, not slow down its opening...). It obviously has some effect - and it definitely has an effect on how much energy is transmitted to the frame and when - but for slide velocity, its not the only (and probably not the first) thing to look at.

Another thing is - the configuration of the FP stop, mainspring, hammer, and strut will also affect how the recoil spring factors into the feel and tracking of the gun What works in one guy's setup may work differently in another (that is, my 12# spring in my Trojan may feel entirely different in some other gun, because of those other factors... actually, there's even more to it than that, but...)

You are right about the dwelling time of the slide of course, this is why I quoted the figure as a minimum, not as an approximation.

But as to geometry: The geometry of the FP stop, hammaer, strut, etc can't change the amount of momentum that is transferred. The only difference from one geometry to another is friction, and I dare say, that the difference in friction is minuscule. Of course the geometry changes the feel, i.e. the moment and the timespan at which the momentum is transferred into the springs (in our case the mainspring). It's very much like using a pulley. The only thing that can really change the amount of momentum transferred into the mainspring is the strength of the mainspring itself.

So basically we only have 3 variables to get momentum/speed out of the slide before it is stopped by the frame:

- friction

- mainspring weight

- recoil spring weight

Geometry is not a factor, IMHO.

It's a torque-arm relationship to cam the hammer. Shorter leverage arm (as in how far up on the hammer the slide pushes) results in less torque applied to cam the hammer and the slide will be somewhat slower. Change the geometry and you get a longer lever arm applied to the hammer which means the same force w/ a longer lever arm is more torque and the hammer cams easier and the slide retains more velocity. A bigger diameter on the bottom of the firing pin stop makes it easier to cock the hammer than a small diameter since that changes where the slide leverages on the hammer.

Your right that total energy/momentum is conserved in the springs, hammer, etc, but that doesn't necessarily mean final slide velocity is the same, either.

Just like a lug wrench on your car tire. You can put all your weight into it very close to the nut. Your momentum is conserved but that doesn't mean the wrench moves as fast or easy as if you hold it out as far from the lug nut as you can. So in a similar way, the geometries can effect how fast the slide move. How significantly? I dunno. I do know I could tell a big difference in dot tracking when I put a more square FP-stop in my open gun.

-rvb

I disagree. There is a difference between a can move - can't move scenario, and a scenario, where it will move, no matter what leverage you have. The main difference is, that you overcome the same amount of resistance, every time the slide cycles, i.e. the resistance the springs supply. The only difference is, for how long you have to overcome the resistance. Of you have a better leverage, the resistance is spread over more time/a longer part of the cycle. With less leverage, the resistance is overcome in less time.

So while the slide will lose the same amount of momentum to the springs, no matter what the leverage, the geometry decides, whether it is a short part of the cycle, where the slide will be stopped more abruptly, or whether it is a longer part of the cycle, where the slide will be decelerated smoothly. Momentum can't vanish. The momentum (and thus speed) taken out of the slide is stored in the springs. No matter, how or when you transfer the momentum, it always stays the same. Thus, the slides speed after the momentum transfer into the mainspring is completed will always be the same, i.e. momentum of the slide (which is the same as the momentum of the bullet+gases) to begin with minus momentum stored in the mainspring minus friction. If you could find a scenario, where that ceases to apply, I see a Nobel Prize in your future.

[rvb]

There is also more than one type of momentum. Linear momentum can also be conserved into angular momentum in the hammer which relates, as you mentioned, to how fast it is cammed. So you are right that the geometries affect the speed at which the hammer is cocked which brings us back to what XRe was saying.....

-rvb

[Duane Thomas]

The other was test-firing a 1911 sans recoil spring. No damage, no measurable change in the slide.

How many times (shots) did he do that?

[Patrick Sweeney]

I'll ask. As I recall, it was more than once, but not thousands.

OK, he got back to me. He fired 10-12 rounds, looking for obvious signs of problems: bulged cases, ripped rims from extractors, etc. He got none of that. Afterwards, the slide showed no signs of its traumatic experience.

[Duane Thomas]

Interesting....

[Patrick Sweeney]

Ned is like that. "Out of the box" doesn't begin to describe him. To him, boxes are for shipping guns.

[Cy Soto]

Hello Folks,

I thought I'd let everyone know that, after cutting the springs and taking them to the range to try them out, I found out that the pistol works best with the 14# spring. I followed CHA-LEE's advice and did some Burkett Timing Drills to find out which recoil spring brought the gun back to where it was after firing the first shot. Even though I like the more nimble recoil feel produced by the 12# spring, I think the 14# is a better choice for this particular gun and load combination.

Thank you CHA-LEE and all the other posters that helped me figure this out!!