Umbrarian
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Posts posted by Umbrarian
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1 minute ago, Wesquire said:
No. That is what you are doing. I'm saying that it should just be f=ma and you use the muzzle velocity, not an arbitrary point inside the barrel where acceleration peaks.
Muzzle velocity is not acceleration.
It is not an arbitrrary point, it is the point where a is greatest, thus f must be greatest since m does not change.
Did you read the paper? It is a peer reviewed journal, I get not believing me, but the reputation of the journal is well established. it supports everything I have written.
Here is the graph again. Note Peak Force occurs early in the cycle. Note it occurs at a specific instant (arbitrary according to you). Note once Peak Force is obtained, Force does not get higher. I am not trying to be argumentative, but you are entirely wrong on this.
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2 hours ago, George16 said:
Actually, force is greater in the second half of the barrel because the acceleration is greater.
In almost every round made, the acceleration is greatest in the first 1/2/3 inches, after that it is declining rapidly.
This is explained well in paper that was posted. He even provided graphs,:
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14 hours ago, Wesquire said:
Force is not instantaneous. Say the 100gr bullet gets to 1000 fps in the first half of the barrel and it takes 1 second. The F would be equal to 100gr x 1000fps^2. However, in the second half of the barrel it accelerates further to 1200 fps and it takes .5 seconds (simplifying). That's an additional F equal to 100gr x 400fps^2.
This is the equation to use f=ma
This is what you are doing f = (100*1000) + (100*400)
which is f = ma1 + ma2 and is incorrect.
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2 hours ago, zzt said:
Not around me. The four clubs I shoot USPSA at have no problem with high round count, complex stages with full squads. Full squads as in if you are not registered within 90 seconds of registration opening, you are wait listed.
Yeah that is what I said. Full squads is what they want.
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52 minutes ago, davsco said:
MD's PLEASE don't reduce round counts! I'd rather skip a match here and there to save ammo vs shooting less at more matches. Between the commute time back and forth and 4-6 hours at a match, i damn sure want to get lots of shooting in!
Problem is, ranges would rather see reduced round counts with full squads, than full round counts with reduced squads.
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15 minutes ago, Wesquire said:
You are misunderstanding this. For example, let's say a 100gr bullet gets up to 750fps when it is half way down the barrel. Then in the other half it still accelerates to 1000fps. The peak happened in the first half, but the TOTAL force is still higher by the time the bullet exits the muzzle than it was at the half way point.
Actually I understand like a PhD.
What you are describing is felt recoil. Actual recoil is an instantaneous component calculated from when a is peak.
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11 minutes ago, superdude said:
Here's the numbers when plugged into a recoil formula. (using 0 for powder weight, but any value could be used as it is simply a constant.) Gun weight values are gun with empty magazine from Glock website.
G34 gun weight 25.93 oz 1024 fps recoil force = 3.16 ft lbs
G17 gun weight 24.87 oz 970 fps recoil force = 2.95 ft lbs
Yes. They are using the fps to get an average acceleration over distance of BBL, since you cannot submit the actual peak acceleration.
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5 minutes ago, Wesquire said:
Except peak force is just one aspect. The total force still goes up after peak force. And again, force isn't even the most relevant metric here, momentum is.
f= ma, m is constant. Thus when a is peak, f is peak. It cannot go up after reaching peak, as that then would be peak.
I do not see how momentum matters. You have Newtons' Second Law -> f=ma, and you have his Third Law -> equal and opposite. So the f number is what it is. Now felt recoil, that is a different and things like gun mass, spring weight, force duration, etc. all factor in.
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15 minutes ago, Wesquire said:
It is just that total force is still higher with a longer barrel (assuming everything else is constant).
Since f=ma, and m is constant, f cannot get any higher then when acceleration is at peak. Since peak acceleration occurs early, Longer BBL lengths after that do not matter wrt to f.
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53 minutes ago, Cuz said:
The bullet has to still be increasing speed during the last half inch of the longer barrel.
Here is an interesting chart showing velocities vs BBL length:
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58 minutes ago, Cuz said:
If the maximum force is applied before the bullet is half way down the barrel, wouldn’t the longer barrel produce lower velocities?
The bullet has to still be increasing speed during the last half inch of the longer barrel.
Sent from my iPhone using TapatalkNo.
Think of it like a car. You slam the g-a-s p-e-d-a-l, you get pinned back in your seat, for most cars, that is when peak acceleration occurs. But the car is still accelerating as you pass 50/75/100/etc, , but not as much as in the first few seconds. Same thing is going on in the barrel.
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17 hours ago, Wesquire said:
Given the same weight, the longer barrel/faster bullet gun will have more recoil because momentum is conserved.
This is not true because the bullet is obviously still accelerating, otherwise the muzzle velocity would be identical. And beyond that, force is not what is relevant here.Yes it is true.
Peak acceleration, and thus peak force, is achieved within the first few centimeters of bullet movement. After that, pressure is dropping fast, and while it is still accelerating, it is accelerating at a decreasing rate.
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25 minutes ago, Cuz said:
Can someone help me wrap my head around this.
I have a 124gr 9mm load that chronos at 1024 FPS from my Glock 34 and produces a 127 power factor. I can reduce the powder charge to get a new load that chronos at 970 FPS for a power factor of 120. This new "reduced power" load would be a softer shooting "lighter" load.
Now, if I took my original load that chrono'd at 1024 FPS in my Glock 34, and shoot it in my Glock 17, it chronos at 970 FPS for a 120 power factor. Would this round then feel "lighter" and be a softer shooting round when shot in the G17?
I've tried shooting them both at the range and I can't really tell the difference, but ultimately, there has to be. The guns are almost the same weight, the G34 is 0.8 oz heavier.
Some of you physics gurus must know how to figure this out...
Thanks,
-Cuz.
No.
From a physics point of view (f=ma), the maximum f has already been achieved before the bullet is halfway down the barrel. So shortening the BBL will lower the PF, but not the force.
As stated above, heavier gun has less felt recoil (also an f=ma situation, because the gun has more mass now.)
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Yes, as a FL resident you cannot directly sell to an IN resident, but you can sell directly to an IN FFL, who can sell to the IN resident.
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If you gotta have them, there is the place to go.
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Looks familiar, cannot ID her.
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On 12/11/2019 at 11:40 PM, 427Cobra said:
the ending is just as it was in 1966, Miles got F—ked, not as hard as Enzo though, Ferrari hasn’t won LeMans since.
The net result was the same, but the ending was nothing like the real ending. Odd since there is so much footage of the actual ending.
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Since it is a free market, it is always fair if they state up front.
Since it is a free market, I buy from someone else who does not charge a re-stocking fee.
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47 minutes ago, zzt said:
Back to back may work for some clubs, but it drastically slows down squads at the clubs I shoot at . Very often on a ten gun squad there are only five shooters. Shooter one shoots both guns, then goes to reload two sets of mags. Shooter two shoots both and does the same. The on-deck shooter is now up and the timing ans scoring ROs are down range painting. Two of the clubs I shoot at forbid it, so it isn't an option. The other clubs don't get anywhere near the number of two gun shooters.
I don't actually see how it could save any time. Shooter one shoots one gun, puts it away, picks up his brass and goes to reload mags. He has cleared the table and the on-deck shooter has his stuff on the table waiting for the Make Ready when the range is clear. So I fail to see how even a second of time is saved. Even if you shot back-to-back you still have to wait for the painters to clear the range.
Rules say you have to paint between shooters, so I don't see how moto gets away with that. The second gun is essentially a new shooter, so you have to paint in between.
Yes back to back only works if the shooter has his mags loaded. If not, then it is not faster. 99% of back to back where I am is different guns/mags, so they are always ready. We are lost brass matches, so that time consuming step is out too.
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My club does back to back. Fastest way to do it, you are already up there and ready to go.
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Were others who missed in a similar way DQ'ed?
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My RTS2 has worked 100% for over a year.
My SRO last 30 days before I sent it back 2 weeks ago.
I have 2 Burris FF3, one is still going, one is dead after 3+ years.
My 3+ year old RMR is working fine.
My Dr. Optic I bought last century is still going strong.
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Yeah it is about .4 inches Overall Diameter, just checked.
36 yard zero - anyone have impact data at other distances?
in Rifle - Technical
Posted
Enter your data into JBM Calculator and it will give you a rough idea.