Recoil springs: Commander vs Government Model

[1911Tuner]

It's been said that the short slide variants need heavier springs because the slides move faster and hit the frames harder.

And I'm about to shoot holes in that misconception by showing that the Commander slide doesn't hit the frame with any more potential for damage than the 5-inch gun...and probably with less...even with equal springs.

And I'm gonna use physics to do it.

First, let's look at the properties that actually do the damage in an impact event. Mass and momentum. Mass and momentum cause the bullet to penetrate deeper, even at low energy levels.

Think about it. If you had to knock down a brick wall, which would you choose for the task...a framing hammer or a 10-pound sledge?

On to a few physical realities.

At a given velocity, the lower the mass of a moving object, the faster it decelerates when it meets a given outside force.

The faster a given mass is moving...the faster it decelerates when it meets a given outside force. In layman's terms: The harder the bullet hits the target, the harder the target hits the bullet. Newton 3 is always in play.

Momentums on both sides of an action/reaction event are equal...at least in theory. Actually, momentums are only equal in the absence of outside force, or in the presence of equal outside force...but for simplicity, we'll go with equal. It's close enough to be insignificant.

The slide's momentum can be no greater than the bullet's. Momentums are equal.

Thus, assuming equal ammunition, the momentum of the lighter, faster Commander slide can be no greater than the slower, heavier 5-inch slide.

But there's more.

Because momentum is a function of Mass X Velocity...and the shorter barrel of the Commander produces less bullet velocity and momentum with equal ammunition...the Commander slide carries LESS momentum on the way to the impact abutment.

AND...because its velocity is higher and its mass is lower...the Commander slide decelerates at a faster rate when it meets the outside force provided by the spring...even if the two springs are equal.

During one of my workshops, I was privileged to have a bright young man in attendance who had a fresh engineering degree under his belt. As I made these points, he smiled and nodded in agreement. Then the question of impact energy came up. Energy is a factor. No denying that. Everything is something.

And a friendly argument ensued...so he whipped out a pencil and paper and eliminated everything except the respective slide and barrel masses...and worked it out.

As predicted, the momentum was lower and the energy was higher. In this case, he showed that the Commander slide impacted the frame with 27-point-something additional foot pounds of energy. 27 foot pounds. Not exactly Earth-shaking. You'll see about as much variation from one round to another within the same lot of ammunition.

And remember that this was without any outside force factored in. No recoil spring. No hammer mass and mainspring. No slide to frame friction.

Factor in the outside forces provided by those things, and the impact energy would doubtless be less than with the 5-inch slide.

An interesting discussion, no?

 

[Cholo]

I followed your reasoning as far as I'm able. I have 2 simple questions, not a challenge. I do have 3 1911's, a 3", 4.25" and a 5". Let's leave springs out of the equation and figure the slides are of the same material. I'm shooting a Speer 230 gr ball cartridge.

1) Which one will slam rearward the fastest and with the most inertia? In other words, which one could possibly cause more damage over time? If I read your post correctly, you say it's the same; mass and momentum.

2) My 1911's aren't Colts, but they offer 2 different spring weights depending on the load. Does Colt not have it right after all these years? If not, why not?

An interesting discussion, yes! :wink:

 

[1911Tuner]

1) Which one will slam rearward the fastest and with the most inertia?

The one with the lowest mass/weight...but the momentum can't be higher than the bullet's, regardless of the slide's speed. Momentum is a function of Mass X Velocity.

It's not speed and energy that carries the most potential for damage. It's mass and momentum.

Remember the brick wall analogy.

Let's try another one.

If you're faced with a charging 1200 pound Brown Bear at 35 feet, and you only have time for one shot...which rifle/caliber do you want to be holding...a .22-250 with speed and energy, or a .45-70 with mass and momentum?

In other words, which one could possibly cause more damage over time?

In reality, there's very little difference. It would come down to materials, heat-treating, etc.

 

[Snake45]

My own shooting observations support you.

I don't feel a whole lot of difference in recoil between a "normal" 5" 1911 and a lightweight Commander.

A (all-steel) Combat Commander has less felt recoil to me.

And a 5" slide on a lightweight frame has more. Noticeably more. In fact, my lightweight 5" 1911 is the single most unpleasant-to-shoot 1911 I've ever seen.

 

[DGW1949]

I'm looking at the difference in slide weight(s) as being two different values of resistance (to rearward movement). In other words, when ya lighten the slide, ya gotta do something to counteract it's increased rearward velocity or else the barrel might unlock before the bullet gets gone.....hence the need for a heavier spring.
What I'm saying is that me thinks that the heavier spring is there for timing purposes, not so much for controlling how hard the slide smacks backwards.

But I could be wrong about that.
What I aint wrong about though, is that Colt knows more about building a pistol than I do....just sayin'.

DGW

 

[revhigh]

I'm looking at the difference in slide weight(s) as being two different values of resistance (to rearward movement). In other words, when ya lighten the slide, ya gotta do something to counteract it's increased rearward velocity or else the barrel might unlock before the bullet gets gone.....hence the need for a heavier spring.
What I'm saying is that me thinks that the heavier spring is there for timing purposes, not so much for controlling how hard the slide smacks backwards.

But I could be wrong about that.
What I aint wrong about though, is that Colt knows more about building a pistol than I do....just sayin'.

DGW

I'd think no matter the weight of the slide, the bullet is long gone prior to the barrel unlocking, no matter the spring as well.

REV

 

[DGW1949]

I'm looking at the difference in slide weight(s) as being two different values of resistance (to rearward movement). In other words, when ya lighten the slide, ya gotta do something to counteract it's increased rearward velocity or else the barrel might unlock before the bullet gets gone.....hence the need for a heavier spring.
What I'm saying is that me thinks that the heavier spring is there for timing purposes, not so much for controlling how hard the slide smacks backwards.

But I could be wrong about that.
What I aint wrong about though, is that Colt knows more about building a pistol than I do....just sayin'.

DGW

I'd think no matter the weight of the slide, the bullet is long gone prior to the barrel unlocking, no matter the spring as well.

REV

Yeah Rev, I could be plumb-wrong about that.
Still though, there's a reason that a weak spring leads to battered locking lugs. I always took that to be a result of too much residual pressure during the unlocking phase....but I aint an engineer, so heck, I could be wrong about that too.

Just food for thought, that's all it is.

DGW

 

[1911Tuner]

In other words, when ya lighten the slide, ya gotta do something to counteract it's increased rearward velocity or else the barrel might unlock before the bullet gets gone.....hence the need for a heavier spring.

Inertial mass of the slide and barrel are certainly part of the delay. but there's more to it than that. A lot more.

The recoil spring offers the least influence of anything that has the opportunity. In fact, the pistol can be fired without a spring at all without any ill effects other than having to manually return the slide.

Use a FLGR and plug for this exercise, and be sure to check and realign the plug and the bushing between shots. I've used a Colt LW Commander to demonstrate it and have probably fired it in excess of 500 times over the years...with no spring. The pistol is fine.

Rev is correct. The breech can't unlock before the bullet is gone. Can't.

What I'm saying is that me thinks that the heavier spring is there for timing purposes, not so much for controlling how hard the slide smacks backwards.

While a heavy spring is a necessary part of the straight/unlocked blowback operation...this is a locked breech pistol that we're addressing. Completely different animal.

The spring has little influence on the delay, and no influence at all on the barrel's vertical disengagement timing.

Timing is fixed, and the timed function will occur at its appointed place in the cycle...regardless of the speed of the cycle.

Time is a function of speed and distance. The spring can affect that, but not enough to make any real or practical difference during the recoil phase.

A description:

At the point that the bullet base exits the muzzle, the slide/barrel assembly have moved nominally .100 inch...providing 1/10th inch of additional compression of the spring beyind its static preloaded state. With a standard 16-pound spring in a 5-inch pistol, that preload is roughly 7-8 pounds. Compressing the spring another 10th inch just isn't going to add much to that.

Stand by and I'll go find an interesting old photograph.

 

[1911Tuner]

Here is an old fluroscope photo of an early 1911 pistol during the firing and recoil phase. If you look closely, you can see the bones in the shooter's hand.

Take note of the link's position and the alignment of the slide and frame at the rear. Here, the bullet base is approximately an inch from the muzzle, and the slide/barrel assembly has moved roughly .070 inch...and that's just about right relative to the bullet's position.

Also interesting is the horizontal engagement of the upper lugs. There's a strong clue there.

Another point is how little the pistol has rotated upward in recoil at the point that the actual force-induced recoil and acceleration is nearly over. Remember that recoil is only present while the bullet is present. Once the bullet exits the system, recoil is over and all movement of bullet and slide is on conserved momentum.

Also of interest is how little of the recoil spring is unsupported by the guide and the plug...which sorta shoots holes in the belief that the spring can kink or bind with the standard system.

 

[DGW1949]

Wow.....very interesting stuff.

DGW

 

[1911Tuner]

Indeed. That old picture has laid a few myths to rest and settled some heated arguments.

Did you spot the big secret?

Here's another clue.

This barrel was taken out of a Norinco after a low round count. My failing memory says about 200-250, but I can't bet a lot of money on that. It may have been 500.

The root cause for the damage was insufficient vertical engagement of the upper barrel lugs. In this case, it was about .030 inch, which is roughly 60% of the total lug height.

The deformation is straight line and the stresses that caused it are present in all Colt-Browning locked breech/tilting barrel designs.

Look closely at the first lug, and you can see the original lug wall's position, and how much deformation occurred. Headspace increased by a like amount. This pistol was within about 200 rounds of a catastrophic failure of the kaboom variety. The owner found it after stripping the pistol for the first time for cleaning, and immediately brought it to me.

Norinco barrels are made from fairly soft steel with a hard chrome plating, but they're no softer than the original 1911 barrels were, and probably a bit harder.

I've also seem similar lug deformation in old, well-used USGI and early commercial pistols with mirror-image deformation on the slide lugs in some of them. The slides in those days were dead soft, and no heat-treating was done.

A final clue is in a description of the function of the firing/recoil phase.

When the gun fires, force drives bullet and slide in opposite directions. The bullet's passage through the barrel is resisted by high frictional forces. The slide is driven rearward...grabs the barrel by the upper lugs...and hauls it along for the ride. Because whatever frictional forces resists the bullet's forward movement are also imposed on the barrel's rearward movement...whatever resists the barrel resists the slide by default...and here is the mechanism by which the locked breech system is delayed.

Literally, an outside force within the closed system...AND...the most significant resistive/delaying force IN the system. It trumps the slide and barrel mass...the recoil spring...and the hammer and mainspring combined.

This explains why the locked breech pistol can be fired without a recoil spring without incident, and why there can be no early barrel "unlocking" regardless of ammunition power or pressure levels.

Look at this picture and understand what sort of opposing forces and shearing stresses must be involved in order to deform ordnance steel like this.

 

[dakota1911]

Maybe a "return to battery spring" and not a "recoil spring". About the only good use I found for a full length guide rod is shooting a 1911 with out a recoil spring; gives you another little piece of physics to look at. How about the firing pin spring? Fire a 1911 without that? Titanium or steel firing pin? Ruger SR1911s have Titanium firing pins you know. How about the mainspring. Maybe we should call that the "hammer spring"? Try firing a 1911 without that? Hmmm. Maybe that is why it is called the mainspring. If you have a Series 80 system how about the little spring up in the slide under that little plunger.

I have played a lot over the years but these days use the manufactuers suggested spring rates on everything and all mine have all the springs in them. I would hope everyone does the same.