Serious recoil springs for serious recoil.

[1911Tuner]

Sam, I think there's a little confusion between failure to extract and failure to eject. The spring rate can have a bearing on ejection...but not extraction.

 

[Sam1911]

Undertsood. But if the quoted passage is the crux of his question, then that's an extraction problem.

Has it not already been shown that a locked-breech pistol remains locked until well after chamber pressure has fallen off?

Sounds like an extractor failure if it isn't pulling the spent case clear of the chamber at all.

 

[Zoogster]

That's true with a blowback pistol, but not with a locked breech/recoil operated design.
The recoil spring has very little to do with slide delay.

When shooting full power 10mm with a light recoil spring the chronographed velocity spread between shots can easily be 100 fps difference between shots with the same full power ammo. This is due to the breech opening too soon, obviously while the bullet is still in the barrel to impact velocity. A heaver spring and that goes away, with all shots consistently within a much smaller range of one another.
Obviously if brass is being extracted while still subject to higher pressures you will also have more expansion and bulging of brass and more pressure being contained by only the brass as the brass is being pulled from the chamber when the bullet is still in the barrel.
This will put more stress on the brass, wearing it out sooner as well.
It is not during full pressure, but the breech does begin to open sooner based simply on weight of the spring.

 

[Old Fuff]

Not exactly. It depends largely on the pistol's design. Glock's use Browning's original short-recoil, locked breech design with some important modifications.

When a cartridge is fired the barrel and slide are locked together as the slide moves backwards, and at a certain point the barrel tips down at the rear releasing the slide to continue on. The elapsed time is called dwell time.

Browning used a link to actuate the unlocking movement, and as a consequence dwell time can't be adjusted - at least very much.

Glock and others use a cam built into the barrel's lower lug, and by changing the length and shape of the lug they can adjust dwell time to correct for higher pressure loads, at least within reason.

Since when a pistol is fired the recoil spring is largely uncompressed (in relative terms vs. when the slide is in its most rearward position), recoil spring tension will have minimal affect on dwell time.

The principal purpose of the recoil spring in a locked breech pistol is to return the slide to battery. Use as a recoil buffer is secondary.

While some who do not fully understand how and why the system works, advocate substantial increases in a recoil spring to buffer the slide's rearward travel, they forget (or ignore) the fact the heavier spring increases the slide's speed as it cycles forward. This can shorten run-up (the time and distance the slide moves from the most rearward position to the back of the magazine where the breech face hits the next cartridge's rim). If the magazine spring and follower has not fully raised the cartridge when the breech face hits the rim the round may nose down, and as the bullet hits the feed ramp jump sharply up and cause a shove pipe jam. In addition, when the now highly accelerated slide/barrel go into battery both the barrel’s lower lug and the mating surface in the frame can suffer from battering.

Unlike many gun users, professional engineers understand the run-up and dwell time factors, and make adjustments in the design, including but not limited to slide and barrel weight, lower lug cam dimensions, and recoil spring systems - and do not depend on asking the recoil spring itself to do too many things.

As 1911 Tuner as wisely pointed out, if one wants to move to higher pressure limits then what a pistol was designed around, a heavy frame revolver may be a better platform to use, where none of the issues explained above come into play.

 

[1911Tuner]

When shooting full power 10mm with a light recoil spring the chronographed velocity spread between shots can easily be 100 fps difference between shots with the same full power ammo. This is due to the breech opening too soon, obviously while the bullet is still in the barrel to impact velocity

If the breech opens before pressure has dropped, you can expect three things...neither of them good.

One is a face full of hot gas and particulate, and the other is bulged or ruptured cases. The third is damage to the upper barrel lug or lugs.

First, you need to understand exactly how the locked breech/recoil operated pistol locks, and then you can better understand why the barrel can't tilt down until the bullet is gone without damage to the lugs and the other problems noted.

Static/in-battery...it's not locked as we understand locked. It's simply in battery, held there by spring tension, and...in the case of the tightly fitted barrel...a little friction.

When the gun fires, and sends the bullet toward the muzzle, there's a heavy frictional drag on the barrel that exerts a forward force on it. At the same time, the slide/breechblock is being pushed in the opposite direction, pulling the barrel backward with it...against that forward force. The lugs are engaged horizontally, preventing the
barrel and breechblock from separating. This is an opposing lock...much like locking your hands together in front of your chest and pulling.

Under the high forces generated by the pressure in the system...and with the lugs engaged horizontally in opposition...if the barrel was yanked downward, the lugs would suffer damage.

I don't know why the velocity varies with light springs, unless it's simply a variation in ammunition...but I do know that it's not because the breech is opening with the bullet still present.

 

[Zoogster]

I know your description of the locking breech is correct, and it is not a blowback design where the spring is responsible for holding the breech in place alone.

However the velocity spread still dramatically increases with a weaker spring. It is not merely the ammunition, and the spread goes away and comes back just by swapping a lighter and heavier spring in and out.
It certainly would make more sense with a blowback design.
The barrel also has yet to tilt, or accuracy would be thrown off. Yet gas must be escaping while the bullet is in the barrel or the velocity would not be impacted.

 

[1911Tuner]

Okay...One more time.

The slide only moves about a 10th of an inch when the bullet exits. An additional 10th of an inch of spring compression would add very little to the delay. Dropping the spring's load rating to even half that of a standard spring isn't going to make a lot of difference one way or another...

because

The recoil spring has the least delaying effect effect on the slide of anything involved.

And

Even if the pressure has dropped to 10% of the peak just before the bullet exits...if you have a half-square inch of lug area engaged horizontally...under prressure...that means that there's still a thousand pounds of force pressing the lugs together. Even if the link could pull it down under that level of force, it would stretch and/or break fairly quickly.

Finally...I'd really like to see some corroborating evidence of the claim that lighter springs equal lower velocity...especially in the face of evidence that going to lighter springs in straight blowback .22 rifles brings about an increase in velocity and mechanically blocking the bolt from moving produces a decrease...which seems backward, but has been documented.

 

[Zoogster]

Finally...I'd really like to see some corroborating evidence of the claim that lighter springs equal lower velocity..especially in the face of evidence that going to lighter springs in straight blowback .22 rifles

In blowback designs it is very obvious why it can happen. This is especially true in rapid fire, and even more so in high cyclic rate select fire weapons.
If the case is pulled out, even partially decreasing the seal between brass and bore, while there is still pressure in the bore then that pressure gains an additional direction to vent in. So it is venting from the chamber. This reduces the pressure behind the bullet, lowering attained velocity if it has yet to leave the barrel.
In select fire weapons with high cyclic rates you can even see sparks and flash from the chamber area as a result of powder still burning (and creating gas) when the round is being extracted.

For the same reason resizing brass from some machineguns is often more difficult. That brass gets removed while there is still more pressure in the barrel, allowing pressure to continue to bulge it beyond the dimensions of the chamber as it is being extracted.


The only reason it would be different in a .22 rifle (.22 LR/CB?) and certain loads with a long enough barrel is because the total amount of gas being created from some loads is so low that it takes little time for the pressure to drop. If the pressure drops enough and the bullet is still speeding down the bore it would begin to create suction from the breech as the distance between the two increases.
It would still likely be positive pressure in the barrel (negative pressure should take quite a long barrel, but I would have to calculate that) but opening up the breech end would remove the 'suction' being created that was reducing bore pressure. It would also give two places to vent from though.
So that is a narrow rare window for that to principal to apply, requiring very weak rounds and long barrels.
This should not be an effect that would be seen in a centerfire cartridge with a realistic barrel length because the volume of gas created is much higher.
With most cartridges far more total gas is produced than can drop to such low a pressure before the bullet has exited the bore in a realistic barrel length. So a sealed breech will continue to add FPS rather than reduce FPS.

 

[1911Tuner]

Here's what I'm gonna do...in the interest of science.

I have a chronograph and I have locked-breech pistols. As soon as we have a day that's above 35 degrees, I'll go put it to the test. I'll even bias the test to favor the theory and shoot a few rounds without a recoil spring at all. Then, I'll report my findings.

 

[The_woodsman]

<Deleted Insults>
Some notes:

Varying recoil spring rates of a Glock 29 will vary the amount of pressure force that resists the rearward force of the slide - The problem of this of course is that it increases the force in which the slide returns to battery - which is why a variable rate spring system would be preferable in this system. I already found such a system and may purchase it or use the idea to fabricate one myself.

I have already chrono'd loads using various recoil springs - that recoil springs rate (and by this I mean between the stock 17# and the 23# which is currently in the pistol) significantly affect the velocity in a Glock pistol is a myth. My tests showed no discernible difference.

I have my own range and my chrono was calibrated within 2 weeks of those tests.

<More Deleted Insutls>

One big thanks to BluEyes, and others who mentioned sources. I appreciate your help.

Have a nice day.

 

[1911Tuner]

all happy to add their unproven speculative rhetoric of which nothing has to do with where to find springs!

Way back in the beginning, Fuff and a couple others pointed out that you ain't gonna find anybody who makes a 40-pound recoil spring for your pistol...and that, given the space available...you probably ain't gonna find anybody who can make one and make it work within the confines of your recoil system...and that even if you can find somebody who can and will...the cost will be high for something that you won't be happy with...because it won't work. Sorry that wasn't what you wanted to hear.

Call Wolff Gunsprings. You might be able to score a 25-pounder...but that's about the limit.

 

[Sam1911]

Guess I should have left this closed the first time. Mr. "The woodsman" wants no more information on this subject. Sorry guys, to have wasted all your time helping.