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## DMR effective ROF

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Tuesday, February 11th 2014, 12:00am

### DMR effective ROF

What limits the effective rate of fire on DMRs? Are you waiting for the spread to decrease or the recoil to settle before you can fire another accurate shot? Both?

Basically I would like to know what shoots the fastest between the SCAR SV, MK11 and SVD. Or how to calculate their effective ROF.

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Wednesday, February 12th 2014, 3:07pm

RPM = rounds per minute (from weapon stats/charts)
Base Rec= Base Recoil (from weapon stats/charts)
FSR = First Shot Recoil (from weapon stats/charts)
Rec after 1st shot = Recoil after you fire 1 round (calculated [ Base Rec * FSR])
rec reco = Recoil Recovery (from weapon stats/charts) for example if your Recoil Recovery was 10º/sec and your recoil is at 5º, it would take you half a second for your weapon to settle back to 0º

Sprd after 1st Shot = Total spread after you have fired 1 round (calculated [Base Spread + Spread Inc Per Shot])
Sprd Reco = Spread Recovery per second (from weapon stats/charts) similar to recoil recovery

eRPMr = Effective Rounds Per Minute based on just the recoil. So in short, if you were using a QBU and you fired 1 round, your gun would recover from the recoil and reset back to your original starting position after only 0.1 seconds. This does not take spread into account.
eRPMs = Effective Rounds Per Minute based on just spread. All except the M39 are limited by their spread recovery. Meaning that your recoil will settle before your spread has, so even though your gun has reset to its original position, the spread has not fully recovered yet. Despite the M39 appearing to be slower, it should be easier to use because instead of needing to develop a "feel" and time your shots, if the recoil has settled you are ready to go.

Full reco time = Full Recovery Time, the amount of time you have to wait in between firing a round if you want your spread and recoil to reset back to their minimum.

"Ain't nothin' soft or sweet, I lift you off your feet
When I cock back the heat, whole crews retreat"

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Wednesday, February 12th 2014, 5:25pm

### Quoted from "Lennox 203"

<snip>

I'm curious how you come to the conclusion recoil settles faster than spread on most of the rifles.

Let's take the QBU:

Recoil settles in 0.8 / 8 = 0.1 second = 100 milliseconds
Spread settles in 0.2 / 15 = 0.013 seconds = 13 milliseconds

Base RoF = 310 RPM = 0.194 sec/round

eRPMr
0.194 + 0.100 = 0.294 ms. 60 / 0.294 = 204 RPM

eRPMs
0.194 + 0.013 = 0.207 ms. 60 / 0.207 = 290 RPM

Seeing as you find an eRPMr of 600 for the QBU, I guess you're assuming that recoil starts settling the moment a round is fired. (As you'd get 60 / 0.1 = 600 RPM)
Even though the exact moment when recoil beings to settle is not 100% sure. I think it's pretty safe to assume it's not the second the bullet is fired.

In the example of these DMRs it would mean that a large portion of the DMRs would have 0 upward recoil when spam clicked (as by your table the eRPMr is much larger than the maximum attainable rate of fire).

In a similar example the M416, would have 0 recoil as well.
As it recovers it's recoil in:
( 0.32 * 2.2 ) / 18 = 0.039 s = 39 milliseconds
Whereas the time between shots is:
60 / 750 = 0.08 s = 80 milliseconds.
That would mean if recoil starts the moment the bullet leaves the barrel, the recoil would have fully settled halfway before the next can theoretically fire. Resulting in a weapon with 0 vertical recoil even on full auto.

----

Just wanna double check stuff, since so far pretty much every DMR topic has assumed that Recoil is the limiting factor for every DMR. Hence why Muzzle Break and Angled Grip are proposed to be good not only to increase stability but also to increase your effective firerate.

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Friday, February 14th 2014, 7:51pm

@nyth
It is true we don't know how recoil full works, but I assumed that recoil settle starts once you stop firing. So if you fire 1 round, it starts working right away. I see it as a 2-step process.
1. Fire (instantaneous recoil)
2. Recoil Settle (known rate)

It is probably something more along the lines of:
1. Fire
2. Recoil Increase (some unknown rate per second or constant)
3. Recoil Settle (known rate)

what you are proposing would mean that for the shot you just fired, the recoil increase takes (60[min/sec]/"X"[rounds/min]) to effect you, before recoil settle starts to kick in. I am sure the recoil increase takes some amount of time, I just don't think it would take the full 60/ROF amount of time.

Let me run with this Shoot, recoil increase, recoil decrease idea. Assuming recoil is the limiting factor, I will assume that RPM = 60/(Recoil increase time+recoil decrease time)
For the Mk11, with a recoil after the first shot of and a recoil recovery of 6°/sec thats 0.1667 seconds for the recoil recovery.
Now the other half of this equation is the recoil increase. First, 60/260 = 0.2307sec. so 0.2307 - 0.1667 = 0.064s for the recoil increase
60/(.064+0.1667)=260RPM
1°/0.064s=15.6°/s. So the recoil increase per second is 15.6°/s, and the recoil decrease is 6°/sec. I don't this whole paragraph is useful, I just did a bunch of math, and wanted to share I guess.

I would love to keep delving into this subject, but I've already spent to much time and I have to get back to actually accomplishing work while I am at work. I hope I can revisit this later

Original:

With time to fire 1 round added:

Resorted:
"Ain't nothin' soft or sweet, I lift you off your feet
When I cock back the heat, whole crews retreat"

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Saturday, February 15th 2014, 2:37pm

Thank You Lennox 203!

Now the most interesting question is:

assuming that we have perfect V recoil compensation:

1. what is effective rpm when we have horizontal recoil reset - and that way we are sure that the follow up shots land on target
2. when we fire with eRPMs what is max horizontal recoil - in one gun after perfect recoil compensation and firing with an eRPMs we can have something like 0.2 - 0.2 (0.4 summed) horizontal recoil but in another we can have something like 0.05 - 0.1 (0.15 summed ) horizontal recoil that is totally random and I believe that this determined true "real fight" accuracy.

My observation is that with almost perfect recoil compensation and firing near eRMPs I am more accurate with with scar SV (0.1 - 0.3 H recoil) than with MK 11 (-0.3 - 0.6 H recoil) but this can be placebo effect

Can You prepare such table?
It will be very interesting

used to be #3 in the World in RAWR Kills

This post has been edited 1 times, last edit by "DarthDevilusALF" (Feb 15th 2014, 2:42pm)

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Tuesday, February 18th 2014, 2:58pm

### Quoted from "Lennox 203"

@nyth
It is true we don't know how recoil full works, but I assumed that recoil settle starts once you stop firing. So if you fire 1 round, it starts working right away. I see it as a 2-step process.
Fire (instantaneous recoil)Recoil Settle (known rate)

It is probably something more along the lines of:
FireRecoil Increase (some unknown rate per second or constant)Recoil Settle (known rate)

what you are proposing would mean that for the shot you just fired, the recoil increase takes (60[min/sec]/"X"[rounds/min]) to effect you, before recoil settle starts to kick in. I am sure the recoil increase takes some amount of time, I just don't think it would take the full 60/ROF amount of time.

Let me run with this Shoot, recoil increase, recoil decrease idea. Assuming recoil is the limiting factor, I will assume that RPM = 60/(Recoil increase time+recoil decrease time)
For the Mk11, with a recoil after the first shot of 1° and a recoil recovery of 6°/sec thats 0.1667 seconds for the recoil recovery.
Now the other half of this equation is the recoil increase. First, 60/260 = 0.2307sec. so 0.2307 - 0.1667 = 0.064s for the recoil increase
60/(.064+0.1667)=260RPM
1°/0.064s=15.6°/s. So the recoil increase per second is 15.6°/s, and the recoil decrease is 6°/sec. I don't this whole paragraph is useful, I just did a bunch of math, and wanted to share I guess.

I would love to keep delving into this subject, but I've already spent to much time and I have to get back to actually accomplishing work while I am at work. I hope I can revisit this later

Original:

With time to fire 1 round added:

Resorted:

Thanks Lennox for answering my question. Guess I'll stick with the muzzle brake after all.

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Tuesday, February 18th 2014, 10:10pm

### Quoted from "DarthDevilusALF"

Thank You Lennox 203!

Now the most interesting question is:

assuming that we have perfect V recoil compensation:

1. what is effective rpm when we have horizontal recoil reset - and that way we are sure that the follow up shots land on target
2. when we fire with eRPMs what is max horizontal recoil - in one gun after perfect recoil compensation and firing with an eRPMs we can have something like 0.2 - 0.2 (0.4 summed) horizontal recoil but in another we can have something like 0.05 - 0.1 (0.15 summed ) horizontal recoil that is totally random and I believe that this determined true "real fight" accuracy.

My observation is that with almost perfect recoil compensation and firing near eRMPs I am more accurate with with scar SV (0.1 - 0.3 H recoil) than with MK 11 (-0.3 - 0.6 H recoil) but this can be placebo effect

Can You prepare such table?
It will be very interesting

I don't think I could because we know less about horizontal recoil than we do vertical recoil. I believe it was Rezal who did a frame by frame analysis of weapons resetting after 1 round fired. That was the closest any of us came to finding out what the "empirical-ly effective" rate of fire was for any weapon. Someone else did a frame by frame overlay of the aimpoint during a magdump, and that was the best representation of how horizontal recoil works. I believe the findings were that weapons recoil to the left and right between the ranges of there stated h-recoil. So if the weapon is 0.2°-0.4°, when it recoils to the left it will recoil between 0.0° and 0.2° and if it recoils to the right it will be between 0.0° and 0.4°. A weapon will recoil to one side at most two times in a row, so if the recoil is Left, Left, the 2rd round will recoil to the Right. Because the recoil values are a range instead of a constant number (like vertical recoil) it is impossible for us to calculate much.
"Ain't nothin' soft or sweet, I lift you off your feet
When I cock back the heat, whole crews retreat"