1911 owners, we are doing it wrong!

[sqlbullet]

(too long, won't read:  We should be using 18 lb recoil springs with flat bottom firing pin stops and 25 lb mainsprings in our 10mm 1911's)

This probably belongs in the gunsmithing section, but for broader reach I am posting in general discussion.  We will move this in a few days.

The conventional wisdom is that we should amp up the recoil spring in our 1911's to reduce frame battering when the slide reaches it's full rearward travel.  The idea is the extra power recoil spring will slow down the slide, reducing the impact velocity, and saving undue wear on the frame slide.

A few weeks back, Yondering made a post here about recoil springs not impacting unlock timing in 1911's at all, which got me thinking and reading more.  In addition, I am in the midst of a 10mm P12 conversion, which also has me researching.

Those of you who are serious 1911 guys have probably heard of 1911Tuner.  You see him at a number of websites, most notably The High Road and m1911.org.  He is a literal encyclopedia of 1911 knowledge, especially when it comes to exactly how the gun works and wears out.  I have spent a fair bit of time in the evenings over the last few days/weeks reading any and every post I can find at m1911.org where he talks about the 10mm.

He isn't a huge fan of 10mm in the 1911 platform.  That isn't to say he hates it either.  He is just blunt that the platform was engineered for the standard pressure 45 ACP, not for a cartridge with almost twice the MAP rating.  He is straightforward that you will crack slides eventually on a 1911.  The are not meant to last forever.  And that they will crack faster running 45 ACP +P and faster still with high pressure rounds like 38 super or 10mm.  We are still talking a service life of 10,000+ rounds in most cases though, more if you don't run full bore 10mm all the time.

In my reading 1911tuner sites some interesting research done by Ned Christensen of Michiguns.  Ned is another serious 1911 guy, making his living tuning and beautifying the platform.  Ned did some research many years back on specifically how to tame the 10mm as much as possible in the 1911 platform.  His method was to fire a 45 acp 1911 in stock configuration without a recoil spring installed, but with a shock buff in place.  After a specified number of rounds the shock buff would be replaced and the test repeated.  The shock buffs were then examined and damage detailed.  This gave a baseline indicator of the force with which the slide hit the frame.

Ned found that a flat bottom firing pin stop with a 1/16" radius and a 25 lb mainspring resulted in the same approximate damage to the shock buff when firing full power 10mm loads as occured in 45 acp with a stock firing pin stop and mainspring tension.

Based on these findings he recommends the above set-up be coupled with an 18 lb recoil spring, not the heavier 20, 22, and 24 lb springs most of us here are running.  Both he and 1911tuner further warn that running heavy recoil springs places undue stress on the slide stop pin and slide stop pin holes in the frame.  Stress that they are not designed to handle.  Whereas the slide and recoil abutment in the frame were designed to handle the stress if impacts from firing.  1911 tuner has fired literally hundreds of rounds of 45 acp through a commander with no recoil spring just to prove that it will not damage the frame/slide.  Please note he did leave the recoil spring plug in place.

Next range outing I am putting the 18 lbs spring back in my Para P16 in place of the 24 lb spring I currently am running. Once the gun passes a 100 round function test with that spring it will be my standard strength based on this information.

I have not linked the articles, as they are many.  If you want to read all about it, go to forum.m1911.org/forums.php and run an advanced search for "10mm" and the author 1911tuner.

--Mitch

[EdMc]

I'd seen this mentioned in a few places before, but never with an in-depth explanation. Thanks for posting.

[The_Shadow]

Good info...The 1911 is a different action (barrel link) than others like Glocks and S&W's for the way things work and the recoil systems.

[Yondering]

Good stuff sqlbullet! I'd read that stuff as well, but it's been a few years so I wasn't able to explain the details well enough in our earlier thread.

One other warning I want to mention is about the 10mm in Para guns - it works, for a while, but is likely to crack the frame and/or slide sooner or later. Been there, done that. Their cast parts just aren't as good for long term durability.

[Intercooler]

So since my Razorback is stock I should up the mainspring. What's stock?

[sqlbullet]

Stock on a standard Gov't model is 23 lbs.  I run a 25 lb with my flat bottom firing pin stop.

[Deadguy]

quite a few experts on the 1911 platform suggest this with the 10

[harrygunner]

Internet has allowed me to see much more of the human experience. I've learned a lot about people. For example, once a "fact" gets out, it won't die. Repetition of "facts" can become the basis for their "truth".

Phrases like "batter the frame" and "delay barrel unlocking" are accepted concepts that are completely unsupported by facts.

'tuner' knows 1911's and apparently some physics. A few years ago, I grabbed some paper and a pencil and did some calculations (with reasonable approximations) on the 1911 mechanism. Here's the interpretation of those calculations.

1) "delay barrel unlocking": When the bullet leaves the barrel, the relationship among the slide, barrel and barrel link are independent of the speed of the bullet. At the point where a slow 200gr bullet or a fast 200gr bullet leaves the barrel, the barrel is no more or less likely to be unlocked from the slide.

2) "batter the frame": Recoil springs slow slides by about 22% by time the lower lug hits the recoil abutment. So, the slide is still moving along pretty fast. The frame abutment is designed to handle its job of stopping the slide.

Recoil springs are meant to return the slide to battery. Slowing the slide is a secondary effect. When it comes to using heavier springs, slide speed reduction is to the square root of the spring strength. So, a heavier spring will slow the slide more, but not nearly as much as people seem to imagine. The slide is still moving along. In fact, to reduce the slide speed by half would require a recoil spring so strong, a human could not rack the slide.

The square cut on a 'firing pin stop' alters the shape of the curve of work the slide does as it pushes the hammer back, forcing the slide to transfer more energy into the mainspring at the beginning of the slide's motion.

The 10mm does test the overall 1911 design more. It applies 56% more force on the slide breech face. That's why a well built slide is important. And faster slide movement can challenge magazines to present the next round properly. Personally, that's the only reason I can think of to increase recoil spring rates. The secondary effect of slowing the slide a bit can be used to tweak magazine feed reliability, especially for lighter Commander length slides.

'sqlbullet' thanks for putting that out there.

[iceburg]

Not sure how true it is, but I've also read that putting in a stronger recoil spring instead of square bottom firing pin stops and stronger mainspring can cause the slide to spring forward more forcefully and can put additional stress on the locking lugs and the link / link pins.

[REDLINE]

Internet has allowed me to see much more of the human experience. I've learned a lot about people. For example, once a "fact" gets out, it won't die. Repetition of "facts" can become the basis for their "truth".

Phrases like "batter the frame" and "delay barrel unlocking" are accepted concepts that are completely unsupported by facts.

'tuner' knows 1911's and apparently some physics. A few years ago, I grabbed some paper and a pencil and did some calculations (with reasonable approximations) on the 1911 mechanism. Here's the interpretation of those calculations.

1) "delay barrel unlocking": When the bullet leaves the barrel, the relationship among the slide, barrel and barrel link are independent of the speed of the bullet. At the point where a slow 200gr bullet or a fast 200gr bullet leaves the barrel, the barrel is no more or less likely to be unlocked from the slide.

2) "batter the frame": Recoil springs slow slides by about 22% by time the lower lug hits the recoil abutment. So, the slide is still moving along pretty fast. The frame abutment is designed to handle its job of stopping the slide.

Recoil springs are meant to return the slide to battery. Slowing the slide is a secondary effect. When it comes to using heavier springs, slide speed reduction is to the square root of the spring strength. So, a heavier spring will slow the slide more, but not nearly as much as people seem to imagine. The slide is still moving along. In fact, to reduce the slide speed by half would require a recoil spring so strong, a human could not rack the slide.

The square cut on a 'firing pin stop' alters the shape of the curve of work the slide does as it pushes the hammer back, forcing the slide to transfer more energy into the mainspring at the beginning of the slide's motion.

The 10mm does test the overall 1911 design more. It applies 56% more force on the slide breech face. That's why a well built slide is important. And faster slide movement can challenge magazines to present the next round properly. Personally, that's the only reason I can think of to increase recoil spring rates. The secondary effect of slowing the slide a bit can be used to tweak magazine feed reliability, especially for lighter Commander length slides.

'sqlbullet' thanks for putting that out there.

Excellent read.  I personally question everything.  Even what I think I know.  I'm surprised so many just take this and that for granted.  Not that there isn't some plain hard fact out there, but sometimes even then it can depend on certain senarios we don't always realize either.  And yeah, chambering 1911s in 10mm Auto doesn't make things any easier either.  The 10mm breaks into a lot of new ground other lesser rounds just never gave us reason to put thought into.

[Intercooler]

23 to 25lb isn't a huge jump. It sounds almost like my Dan Wesson is about perfect right out of the box. Guess I will just wait for the crack to occur. I would like to see some picture evidence when these things happen.

[sqlbullet]

They have pictures in various threads on the m1911.org site.  Most are of 45 ACP 1911's that have cracked.  It will eventually happen even to them after enough rounds.

Keep in mind, we aren't talking about cracks in the first 1,000 or even 5,000 rounds.  We are talking for a 45 about 30,000-50,000 rounds.  For a 10mm I would guess 10,000-20,000.  The cost of a new slide against the cost of 20,000 rounds of Underwood is nothing.

[Intercooler]

Maybe a Shock Buffer would do the trick?

[REDLINE]

For a 10mm I would guess 10,000-20,000.

I wonder if it would be less rounds than that with a steady diet of all premium Underwood loads.

[sqlbullet]

Maybe a Shock Buffer would do the trick?

By the time anything moves at all, the forces that cause the slide to eventually crack are long over.  The slide cracks in question are caused by the stress of keeping the breech locked, not by the momentum of the slide during cycling.