racking a slide


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Jeremiah10:23
May 3, 2012, 09:04 AM
Is there a way to measure how much "strength/pressure" it takes to rack a slide? The reason I ask is, last night I rewatched the American Gun episode with the custom 1911 I mentioned in another thread.

Keeping in mind that quality affects price, I was looking for the "quality". I think I spotted some evidence that that pistol was not average. When the slide was racked (overhand) it seemed to be much easier than when I rack my slide in a similar manner.

The things I would like to know are...
1. how to measure the rack strength needed.
2. what affects the amount of strength needed?
3. which pistol requires the least ammount of effort to rack the slide. (I know opinions are like..., so I want data)

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Walt Sherrill
May 3, 2012, 09:16 AM
It all depends on variables, some of which are easily changed. Part of it might be shooter technique.

I don't know of any objective way to measure the thing you want to measure. For a given gun, you just see if you can handle it, when you get it. If it's too hard, you have options.

A new custom pistol might be easier or harder to rack than some older guns because of 1) tolerances or 2) heavier (unused) recoil or hammer springs. It all depends on the gun maker. The "springs" part of that can be changed by the owner. Little things, like cocking the hammer first can make a hard-to-rack gun easier to rack.

You can change springs, going to lighter recoil or hammer springs, or some variation: heavier hammer spring and lighter recoil spring.

A too-light recoil spring might not let the gun function properly (i.e., won't close the slide properly or load the next round); a too-heavy recoil spring might not allow the slide to open fully. A too-light hammer spring might not ignite the round. There are a lot of possibilities between those different options and extremes.

wwace
May 3, 2012, 09:18 AM
I know that a 1911 has some variables with the return spring can be some 8 or 10 pounds of difference depending on models, also they are easier to rack if already cocked. My SR1911 has an 18lb spring so it would take at least that much force plus whatever it is to cock the hammer.

Manson
May 3, 2012, 09:57 AM
I'm not sure that resistance levels when racking the slide is a good measure of quality. it's more a measure of recoil spring weight. A .22 semi with it's lighter recoil spring will be easier to rack than a .45.

You might want to equate a heavy racking with quality due to thinking of it in terms of tighter tolerances. But I'm not sure about that either. Nothing is more reliable than my Glocks. And I can read a book through the gap between the slide and frame.

In the end I don't think there is a method of measuring it. Due to the fact that it probably has little to do with anything.

Greg528iT
May 3, 2012, 10:35 AM
probably what you also notice it the smoothness of the racking motion. A gun that may have tight tolerances, but is fully lapped in and everything is dead smooth on the guides will rack smoother than a gun with minimal fitting that has some grind or friction to it. I say grind, but I mean the not buttery smooth action of high end worked gun. My gun with the most rounds thru it, racks way smoother than the ones with less.

As other have said, the recoil spring rate also has a BIG effect. I shot a guys 2011, .40 cal race gun.. not only was the action buttery smooth, since he's mostly shooting lighter loads his recoil spring was easily under 14 lbs vs the stock 16 lbs in mine.

ku4hx
May 3, 2012, 10:51 AM
Many years ago, I was acquainted with a fellow who owned a small pawn shop; he did a big business in used guns. He made it a practice to have light weight recoil springs in all his center fire semi auto pistols because he said these improved the likelihood of a sale. The OEM spring was always included in the deal and if the shooter had problems he'd swap out the springs.

Did his ploy work? I have no idea. I didn't do business with him and he's deceased now so it really doesn't matter.

But the thing is, you can make slide movement as easy as you're willing to work at. Either by using light weight springs or by cutting off coils. Neither action affects the basic quality of the gun, just how it's "set up".

Manson
May 3, 2012, 11:03 AM
Wow KU I never thought of it as a way for someone to improve sales. Sneaky. Effective, but sneaky.

firesky101
May 3, 2012, 02:48 PM
Reminds me of a gunshow I went to. The guy with the table next to mine traded a guitar for a 3" 1911. I knew the guy, so I thought I might be able to buy it from him for a good deal. I tried to rack the slide and it was close to impossible, I got it but it was the stiffest slide I have ever seen. Two other guys there made fun of me until I handed it to them and they had the same problem. I know it was probably only a recoil spring, but I did not make an offer on that pistol after that, it just was not as appealing.

Certaindeaf
May 3, 2012, 03:02 PM
You could lay hands upon it and rack/attempt to rack it.

9mmepiphany
May 3, 2012, 07:20 PM
The things I would like to know are...
1. how to measure the rack strength needed.
2. what affects the amount of strength needed?
3. which pistol requires the least ammount of effort to rack the slide.

1. I don't know that anyone has even developed or measured the strength required. It is usually just a matter of if you can or can't...if you'd ever racked a Astra 600, you'd understand. Racking a slide is more about technique than muscles

2. This can be affected by the locking mechanism, slide mass, the caliber that needs to be contained.

3. Comparing like sized pistols (service), in like calibers (9x19mm), I'd rank them, from least to most:
i) roller delayed - H&K P9s
ii) falling block - Beretta 92
iii) tilting barrel - Glock 17
iv) blowback - H&K VZ70

Drail
May 3, 2012, 10:43 PM
Cock the hammer first. If the springs are lightened too much the frame can be damaged, the slide can run so fast the magazine cannot get a round up in time and the gun will actually be harder to shoot. Or if you're not physically handicapped do some strengthening.

9mmepiphany
May 4, 2012, 12:20 AM
I don't think the OP said he was having a problem racking the slide or asking for techniques of how to best accomplish it.

I think he is only asking for a comparison of the force required for different platforms and what factors affect the force needed

Walt Sherrill
May 4, 2012, 07:46 AM
I think he is only asking for a comparison of the force required for different platforms and what factors affect the force needed.

Agreed, but the question suggests a certain unfamiliarity with firearms (i.e., what controls function, etc.)

Some of the responses addressed that seeming unfamiliarity. Some of the others said that there is no meaningful way to measure the force required (suggesting, as one respondent wrote, that it wasn't relevant to measure).

Several responded that the force required to move the slide was controlled by a number of different variables, and I would add that most of those variables are not specific to a type or brand of gun.

The original poster did note that one specific gun seemed easier to rack than others, and reasons for that were offered. Given all of the factors involved, there's really no simple answer to what seemed to be a simple question.

Jeremiah10:23
May 4, 2012, 11:19 AM
9mmepiphany,
You are correct. I have no problems racking a slide. I think I understand now why it seemed so easy for the gun to be racked on American Gun. It being a 1911 after he racked it the first time it would have had needed less energy to rack it again. He racked it about 4 times in rapid succession and that was what made me question it. I could never do that as quickly and easily with my KelTec.

I was hoping there was some factor that made it easy to choose an easily racked pistol (for my wife). Basically as a starting point for her shopping.

This is one reason I like to read on here because the responses (even if not directly relevant) still give me as a "learner" an education. I've learned a lot from you guys (and gals). Thanks.

Jackal1
May 4, 2012, 12:47 PM
Might I suggest reading "Shigley's Mechanical Engineering Design, 8th Edition, Ch. 10, Mechanical Springs".

The only outstanding info you would likely need to get a pretty close answer would be friction numbers which would be heavily dependent on your particular lube.

I have a spreadsheet I use to calculate this, but the spring force is the dominant contributor to the force required to rack a slide.

Cheers.

hAkron
May 5, 2012, 07:59 AM
What if you racked the slide by pushing the forward edge of the slide on a bathroom scale? That should show you the amount of force, in lbs, to operate the slide.

If 'smoothness' is what you are talking about, then I would think the math would b a bit more complicated. You would need to measure multiple examples of weapons with the same hammer and recoil spring and the difference in resistance is your result.

PabloJ
May 5, 2012, 08:04 AM
Is there a way to measure how much "strength/pressure" it takes to rack a slide? The reason I ask is, last night I rewatched the American Gun episode with the custom 1911 I mentioned in another thread.

Keeping in mind that quality affects price, I was looking for the "quality". I think I spotted some evidence that that pistol was not average. When the slide was racked (overhand) it seemed to be much easier than when I rack my slide in a similar manner.

The things I would like to know are...
1. how to measure the rack strength needed.
2. what affects the amount of strength needed?
3. which pistol requires the least ammount of effort to rack the slide. (I know opinions are like..., so I want data)
The answer to question number 3 is the COLT 2000.

Walt Sherrill
May 5, 2012, 08:51 AM
re: COLT 2000...

I've shot two of them. I don't remember the slide being all that light, but I do remember the trigger.... (shudder).

Jim K
May 5, 2012, 07:51 PM
Pretty easy to determine the force needed to retract the slide. Simply cut a length of wood dowel; put one end on the front of the slide where neither the barrel or the spring plug will touch it. Put the other end on your bathroom scale. Push down. The figure you read is the force required.

Jim

ladytech777
May 6, 2012, 12:21 AM
I had the same questions when I bought a G19. I talked to a Glock "specialist" in my area, about some work-ie:trigger job, mods etc. He offered me several choices for slide and recommended not to go below 15lbs(?) or most Glocks will have cycling problems. I would say find out what a gunsmith who works a lot with a particular gun would recommend. I'm glad I took his advice! Gun is perfect now.

Grayrock
October 30, 2013, 05:55 PM
I was wondering the same thing about racking force required of different pistols. My wife is looking for a gun and likes the semi-autos. But she may have difficulty pulling the slide back. I was looking for a comparison chart with racking force. One could measure with a string and a fishing scale (or do the dowel & bathroom scale trick.)

snooperman
October 30, 2013, 06:28 PM
Jim K , Gave you the best way to determine the force in pounds that I know. You can also buy a spring device from Brownell's, but Jim's idea is just as good.

JTQ
October 30, 2013, 07:12 PM
Man, this is a year old thread, but anyway…
Grayrock wrote,
My wife is looking for a gun and likes the semi-autos. But she may have difficulty pulling the slide back.

This is really the best place to start…

http://www.corneredcat.com/article/running-the-gun/rack-the-slide/

hentown
October 30, 2013, 07:26 PM
It's a year-old thread, all right. Can't believe some questions that are asked on forums like this. Stronger spring equals harder slide to rack, etc!

If you enjoyed reading about "racking a slide" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!