Extra-strength recoil springs and return battering

[Candiru]

It's widely popular to replace the recoil springs on semi-autos with a heavier version in order to reduce frame battering during recoil. I've always felt this couldn't hurt, provided the gun still functioned reliably, but preferred standard-strength springs: I don't shoot +P ammo in my semi-autos because High Powers don't thrive on that and 1911s don't need it. Besides, I don't flatter myself that I know better than JMB and/or Dieudonne Saive.

The issue I'm wondering about has been brought up by others: concern about damage to the pistol caused by the slide slamming home with excessive force due to the use of a heavier recoil spring. The way I've always looked at it, if the pistol is to function correctly, the slide will need to move all the way rearward to eject the spent cartridge, so you're going to get slide slap regardless of recoil spring strength. This brings the return force down to being determined by the spring modulo any force imparted by bouncing off the frame. Given two recoil springs with 2.2 lbs. (1 Kg.) difference in weight, the difference in force slamming 4" forward is going to be less than 2.2 Newtons, or about 0.5 pounds, difference. (I'm not sure how much less it's going to be without knowing the spring constant, starting compression, coefficient of friction, and final compression, then doing some calculus. Let's just assume "a smidgen" is a scientific unit.)

This doesn't seem like a whole lot of difference, but all the number crunching in the universe is irrelevant if the numbers don't match up with fact. Has anyone seen much of a difference in wear on a pistol due to increased force in returning to battery because of a heavier recoil spring?

This isn't just a theoretical consideration for me. I've got an FM Detective short-slide Hi-Power that I carry because I have a much easier time concealing it than a full-sized Hi-Power. Hi-Powers don't take well to shortening the slide (the locking lugs end up taking one for the team), so I've replaced the recoil spring with a 20-pounder in the interests of delaying unlocking, but I've noticed some wear on the rear side of the frame's camming lug, where the barrel slides against it while going into battery. I'm not noticing any corresponding wear on the barrel and slide's locking lugs, though, so I'm wondering if the heavier spring may be to blame.

 

[dfariswheel]

One of the import Walther P-38/P1 aluminum pistols that I saw with a broken frame, was broken through the take down lever hole.

The front of the frame was driven FORWARD.

The gun had been fired with hot ammo, it was a well used gun, AND it had "extra power" springs.
Of the other cracked or broken frames I've heard or, most had been using extra power springs.

I've always had a problem with spring changers.
A designer and gun company spends hundreds of thousands, if not millions of dollars developing a firearm, including extensive work "balancing" slide weight to locking systems to spring weight.

Then along comes an owner with NO knowledge at all who just decides to change out the springs because it'll make it "run better".

If a gun won't run with factory spec springs, something is wrong with the gun. Yes, changing the spring might make it run better, but what's really happening is the problem has been masked, but not corrected.
There are additives you can dump in a car engine or transmission to make it "run better", if something is wrong, but this is just a temporary band-aid.

To paraphrase Congressman Fritz Hollings, "There's to much of that springin' goin' on".

 

[1911Tuner]

re:

Howdy Candiru,

Pressed for time, but a little food for thought with a couple of points. Nay...Three!

1...Springs work in both directions.

2...Changing something always changes other things to a large or small degree. No free lunches, I'm afraid.

3...The recoil spring doesn't delay unlocking, and has very little to do with
delaying the slide's initial rearward movement. Unlocking is a timed, mechanical event, controlled by the lower barrel lug and slidestop crosspin.
It occurs where it occurs, regardless of how fast or slow it reaches that point. Bullet exit occurs at about the first 1/8th inch or less of slide travel, and barrel disengagement begins.
An added .125 inch of spring compression past preload isn't going to have very much of an effect.

"Unlocking" is technically misleading, since the gun locks at the instant of firing and unlocks when the bullet exits. The separation of the barrel and slide
occurs after unlock...necessary to get the barrel lugs disengaged from the slide's lugs and slots in time to prevent a crash. Since the lugs are engaged under high pressure, the bullet must be gone to drop the pressure before they CAN disengage.

To better understand that statement, have a large, powerful friend push against a door with all his might...and try to turn the knob, and it'll start to make sense.

 

[Walt Sherrill]

I can't speak with regard to FRAME damage from extra-power recoil springs, but have seen some slide stops broken by what I think were the heavier springs. (Its hard to PROVE the cause of any such damage.)

Frame damage seems to be a bogeyman that many fear but few actually see.

 

[GoRon]

I put a heavier recoil spring in my 1911 due to conventional wisdom. I expected to feel a reduction in recoil, to my surprise it felt like it had more recoil.

Not long after that I put a new 16# spring in it and I am sure it shoots flatter.

 

[1911Tuner]

re:

GoRon said:

>I put a heavier recoil spring in my 1911 due to conventional wisdom. I expected to feel a reduction in recoil, to my surprise it felt like it had more recoil.<
**************

Yep. Recoil in an autopistol comes at us in three separate phases. The first is the true recoil from firing. The second is the slide pushing the frame against our hand through the recoil spring. The third and lightest impulse
comes with the slide impacting the recoil surface in the frame. Of the three,
we "feel"the second one more. It has more effect on us because it lasts longer...and the stonger the recoil spring, the harder the frame pushes our hand and the longer it lasts...and you get a second dose of that push as the slide heads back to battery. The three impulses come so close together and happen so fast that they seem to be one single event...but they're not.

Notice how much faster your hand got tired with the heavier recoil spring?

 

[Candiru]

1...Springs work in both directions.

2...Changing something always changes other things to a large or small degree. No free lunches, I'm afraid.

3...The recoil spring doesn't delay unlocking, and has very little to do with
delaying the slide's initial rearward movement. Unlocking is a timed, mechanical event, controlled by the lower barrel lug and slidestop crosspin.
It occurs where it occurs, regardless of how fast or slow it reaches that point. Bullet exit occurs at about the first 1/8th inch or less of slide travel, and barrel disengagement begins.
An added .125 inch of spring compression past preload isn't going to have very much of an effect.

Thanks for the pointers. In my defense, at the time I got the heavier recoil springs, I was laboring under the assumption that spring weight had some noticeable effect on the length of time it took the slide and barrel to reach the unlocking point. Are you saying that the relationship between the bullet's position in the barrel and the barrel and slide's position relative to the frame is constant? Would a heavier mainspring help reduce the slide's velocity at the point where cam disengagement occurs? My goal with this pistol is to minimize the slide's rearward motion at the point where locking lug disengagement occurs in the interests of preventing premature rounding of the lugs.

dfariswheel, you and I are in complete agreement. I only use standard-strength springs on all my pistols. The only reason I'm monkeying around with this one is because it's already in unknown territory. To the best of my knowledge, the FM Detective is the only production short-slide Hi-Power ever made. It's stock recoil springs are next to impossible to acquire as replacements, so I use CZ-75C springs. (This is not as much of a hack as it may seem, since the CZ-75C is basically a short Czech Hi-Power.) The Hi-Power's elegant design comes at the cost of some durability, which is only exacerbated by shortening the slide, so if a little bit of experimentation can find a way to prolong its lifespan, it's worth the work to me.

My plan at this point is to drop down to 18 pound recoil springs and bump up the mainspring to 36 pounds, provided that stands a chance of helping minimize wear to the locking lugs. I'm going to be upgrading my full-sized Hi-Power's mainspring, anyway; it's a pre-1975 FN, so its mainspring is only 26 pounds. I shot it the other day after shooting the heavier-mainspring FM Detective and was blown away by how snappy it was by comparison. It's amazing what a difference some additional resistance makes when it's applied at the hammer level. Now I'm tempted to try out one of those flat-bottomed firing pin stops for the 1911...

 

[1911Tuner]

re:

The higher rate mainspring will do more to delay initial slide movement than the recoil spring, so you're thinking is spot on here. Haven't looked at a
recent-production High Power, but the older ones had a pretty small radius on the firing pin stops. If the old and new are interchangeable, you might look into getting one of those to see what effect it has on the slide.

Regardless...neither the mainspring nor the recoil spring has anything to do with reducing locking lug wear unless the timing of that event is so early that the barrel is trying to drop while the bullet is still present. A little better understanding of what happens will help.

When the gun fires, the bullet is forced through the barrel under pressure.
This forces the barrel forward hard. At the same instant, the slide is driven rearward under that same pressure. When whatever slack exists between
slide and barrel (fore/aft clearance) the lugs bear against each other, locking the breech. The slide...due to its greater mass...pulls the barrel rearward with it. When they reach the disengagement point at about .125 inch a of travel,(give or take a few thou) the barrel is drawn down out of engagement with the slide. Before this can occur without damage to the locking lugs, slidestop crosspin, and lower barrel lug, the pressure must fall off to zero. (Actually to atmospheric...but that's pickin' nits.) That means that the bullet has to be out of the muzzle and on its way prior to the disengagement point.

Remember the big guy shoving the door analogy. While he's pushing, the bullet is in the barrel, and locking pressure is high...and it's hard to turn the knob. When he lets off, the bullet is gone, and you can turn the knob easily.
As long as he is pushing, the latching plunger (barrel lug) is forced against the striker plate, (slide lug) and the knob won't turn without forcing it...and possibly damaging something. At the very least, the high frictional forces
accelerate wear the plunger and striker plate.

By delaying the slide for a split second longer, you're giving the bullet a tiny bit more time to exit. If the gun's specs are a little off, and the barrel disengagement is occurring too early...while pressure is still up...delaying the slide a little can often bring things into harmony without mechanically delaying the barrel drop with a longer link (1911) or altering the geometry of the lower barrel lug. (linkless designs such as the P-35)

Delaying the slide's move has other benefits. Some report a little better accuracy...less vertical stringing...and reduced felt recoil...due to the mainspring's absorbing more of the slide's energy and reducing the slide to frame impact in phase three.

The small-radius firing pin stops were original design specs in the early 1911s.
This was changed by the Army Ordnance Department in response to complaints over the pistols being too hard to hand-cycle with the hammer down. (Army protocol demanded that the pistols be carried in Condition 3
and chambering a round only when action was iminent...which sometimes
came suddenly.)

 

[1911WB]

Interesting discussion

Tuner, another very interesting discussion. I feel like I learn more from you than I did in college!

 

[Candiru]

Most informative, thank you. Now I understand why messing around with springs is largely misguided when it comes to timing issues. I don't have the time now, but I'm going to do some calculations later to see how likely it is that the disengagement point is reached before the bullet has exited the barrel. I'm pretty sure the equations will reduce down to a relationship between the slide and barrel's mass vs. the slide and barrel's length. If it's not a close thing, I may just leave the mainspring as it is and drop down to a less draconian recoil spring.

I'll post my extremely crude calculations this evening.

 

[1911Tuner]

Calculations

No need to calculate it. If the disengagement point was being reached before bullet exit, you'd have a damaged lower lug or slidestop pin by now...and the barrel lugs would be heavily rounded on the front corners...
or sheared off.

 

[Candiru]

Heh, too late--already ran the numbers. But they confirm what you said.

I used the worst-case scenario, where there's no mainspring, recoil spring, or friction. (This also happens to be the only case I can calculate without getting a headache and probably screwing things up.) Even with a short Hi-Power slide, we're looking at almost an order of magnitude difference in time between when the bullet exits the barrel and when the barrel's lower lug engages the camming surface. Add a mainspring and you've got huge margins of error.

Given these data, there's no reason to have as strong a recoil spring on the gun as I do, so I'll drop down to stock weight. There's also no real reason to beef up the mainspring on the gun, since the fate of the locking lugs is pretty much up to geometry--and thus far they seem to be doing pretty well. However, I will replace the mainspring on my older Hi-Power, since 26 pounds makes for some snappy recoil.

Thanks for your help, Tuner.

 

[Old Fuff]

Remember, unlike the 1911 platform that uses a link, the Browning P-35 is locked and unlocked by a cam on the bottom of the barrel. Thus dwell time can be changed by modifying the shape and length of the cam. It might be interesting to compare the two barrels in your stock Hi-Power vs. the one in the Detective model to see if the lugs on the bottom are different.

 

[carnaby]

Higher power recoil springs are recommended on Beretta 96 Brigadiers, IIRC. Seems for some reason Beretta put underpowered springs on 'em. I got a wolff spring for mine, 2lbs stiffer than stock. Seemed fine.

If you search on www.berettaforum.net you'll find the posts on this.