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Old December 28, 2018, 09:05 PM   #151
David R
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All I asked is how far does the slide move before the bullet leaves the barrel.

David
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Old December 28, 2018, 10:33 PM   #152
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To answer that, requires knowing the combined weight of the barrel and slide, and, if applicable, the bushing and recoil spring plug.
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Old December 28, 2018, 10:33 PM   #153
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Zero inches for the pistol in question if you're asking about slide movement relative to the frame.
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Old December 28, 2018, 10:38 PM   #154
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Assuming that the slide velocity is about 20fps (which is probably in the right ballpark); and using Unclenick's calculated barrel dwell time, it moves about 0.2" before the bullet leaves the bore.
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Old December 28, 2018, 11:04 PM   #155
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Quote:
Originally Posted by Mal H View Post
Zero inches for the pistol in question if you're asking about slide movement relative to the frame.
High speed video evidence says otherwise.
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Old December 29, 2018, 11:00 AM   #156
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Never thought such a simple question could generate so much interest and it has been a very interesting read with lots of different opinions.
At any rate I bought some .230gr. Hornady HAP bullets and loaded up 3 different boxes of 50. all with an overall length of 1.230 in new Starline brass with a taper crimp of .467.

1. 6.6gr. of power pistol.

2. 6.0gr. of universal clays

3. 5.4gr. of HP-38

All 3 shot to the point of aim elevation wise with the universal load delivering the best overall accuracy at 30ft. Both the Universal and the HP-38 loads seemed a bit hot so I'm going to reduce to 5.8 and 5.2 respectively.
next time out.

Brought 2 .45's with me a 5" with target sights and the commander. I definitely shoot the 5" better with the longer sight radius and sights but that's just old age creeping up on me.

Hope everyone has a happy new year.
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Old December 29, 2018, 11:55 AM   #157
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74A95 - you're probably right, but do you have a slo-mo video of a Commander length 1911? I shouldn't have said "zero", but "imperceptible" instead.
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Old December 29, 2018, 12:29 PM   #158
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Quote:
Originally Posted by Mal H View Post
74A95 - you're probably right, but do you have a slo-mo video of a Commander length 1911? I shouldn't have said "zero", but "imperceptible" instead.
It doesn't matter what gun it is. https://www.recoilweb.com/when-does-...ve-127274.html
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Old December 29, 2018, 07:56 PM   #159
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Am not a video expert, but does it appear the hand holding those pistols is video chopped in place? If they were video chopped, would be interesting to see what was actually holding the guns in place.
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Old December 31, 2018, 04:20 PM   #160
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One more time.
25 yards Light Weight Officers ACP 3.5" barrel.

Center target Remington Ball. 230 grain


Top left 200 swc 1,000 fps
Bottom left 200 SWC 676 fps
Bottom Right 200SWC 900 fps.
Velocities are for a 5" gun.

Evevation looks petty much thesame to me.

David

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Old December 31, 2018, 04:46 PM   #161
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Quote:
Originally Posted by Brutus
All 3 shot to the point of aim elevation wise
That's typically the case with the same bullet weight, even in a revolver. POI doesn't change appreciably with the load—a little, but not a lot. It's because a lighter charge, though it doesn't recoil as hard, will apply that recoil for a longer time before the bullet clears the muzzle. It's not exact compensation, but its close enough for most folks.


Mal,

If the slide didn't move at all, there would be no momentum in it to cycle the gun after the bullet left. Once the bullet was gone it would just sit there. Not moving at all would also mean the slide was locked to the frame, so the muzzle would rise more during the time the bullet is in the barrel, like a revolver does.


David,

On a full-size 1911 the slide and barrel weigh about a pound. At 352 ft-lbs ME, the bore experiences and average recoil force of 977 lbs plus about 3-5% more to overcome friction, so about 1000 lbf (pounds force). The barrel time for the 230 grain ball to produce that ME with that average force at its base is about 0.77 ms, so acceleration will be:

1 lb = 0.0311 slugs and 1000 lbf / 0.0311 slugs = 32,174 ft/s².

So slide velocity at the end of 0.00077 s will be 0.00077 × 32,174 ft/s² = 24.8 ft/s.

Since the slide started at 0 fps, the average velocity will be 12.4 ft/s and the distance traveled will be 0.00077 seconds × 12.4 ft/s will be 0.0095 ft or 0.114 inches.

That assumes no other sources of load on the recoil, but in fact, there is a bit. The cocking of the hammer, the spring-mass compressed in that sub-millisecond period. Friction between slid and frame. Unlocking force will produce some too, so actual motion might be closer to 0.1 inches with that hardball load.
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Old December 31, 2018, 06:59 PM   #162
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Quote:
Since the slide started at 0 fps, the average velocity will be 12.4 ft/s and the distance traveled will be 0.00077 seconds × 12.4 ft/s will be 0.0095 ft or 0.114 inches.
Yup. The bullet and the slide both start at zero fps and by the time the bullet exits the bore, it is going at muzzle velocity and the slide is going about 25fps.

I used a WAG of the max slide velocity (velocity at bullet exit) instead of the average velocity of the slide while the bullet is in the bore. My number will therefore overestimate the slide movement. The 0.114" number should be more accurate than the 0.2" figure I provided.
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Old December 31, 2018, 07:17 PM   #163
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With all this talk about slide speed, folks might find the information at the link below of interest.

http://www.shootingtimes.com/editori...s-timing/99604
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Old December 31, 2018, 07:38 PM   #164
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From the article:

"...it was clear that the recoil phase was not dramatically different between these spring weights when using the same ammunition. The slide moved much slower when going forward..."

Interesting. So while the cycle time was slowed with the weaker spring, the main change occurred during the FORWARD travel of the slide--the portion driven by the recoil spring. The slide speed during the rearward travel of the slide was not changed dramatically by changing the recoil spring strength.
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Old January 1, 2019, 08:19 PM   #165
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I think that makes sense. With an average force of about 1000 lbs during the barrel time that imparts momentum to the slide, whether you have a recoil spring with two or four more pounds of force opposing it is a difference that will be lost in the noise.
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