The effects of vegetation as an intermediate barrier on accuracy and precision is a concept that I have wondered about since my youth reading about brush busting guns and loads in the various hunting magazines. Living out West in the vast openness the ideas seemed quite foreign to me. Several decades later with many years of hunting big and small game, 16 years as a wildlife manager/LE officer/firearms instructor later, these types of situations have become a reality for me more so than I would have expected. So, for some time I have wanted to test this concept and see what I would find.
My daughter recently needed to come up with a science fair project so the two needs came together to make this happen. I've talked to both Frank and Jacob and have gotten some great feedback and encouragement to do this project.
Last weekend my daughter and I went out to the range to run some preliminary trials. We made some interesting observations and were able to refine our study design.
We decided that we wanted to test shooting through a brush barrier that was placed close to the target (5 yards), midway to the target (50 yards) and very close to the muzzle (12").
Together, we built a frame and stand to hold the brush that would allow us to shoot through it in a fashion that would randomize contact with the obstructions just like would happen in real life. The size of the obstructions ranged from leaves and small green twigs to woody branches the size of a finger.
Our targets consisted of an 11"x17" piece of paper with 10 red 1" circles distributed evenly over the paper. This also helped with randomizing the portion of the brush barrier penetrated by the bullet.
We attempted to keep all variables the same, except for whether or not there was a brush barrier and the location of the brush barrier in the bullet path. We even addressed natural point of aim variations by standing up and rebuilding the position after 5 shots.
I did all the shooting while my daughter plotted impacts on her data sheet. This really helped us keep track once the bullets started doing strange things.
We took digital photos of each target up close and used the On Target application to measure the deviation of the POI from the POA. On Target is for analyzing groups. Since I fired only one shot per dot, I had to place a second shot exactly on top of the POA for the application to calculate. This was done for all shots so that variable should also be constant across all shots. Here are few images of what we did.
Brush Barrier
Conrol Group
Barrier 5 Yards from Target
Barrier 50 Yards From Target
Muzzle Barrier
Sorry, I can't get the following to display very well.
Firearm .308 Winchester 100 yards
Measured Deviation by Target
Control 5 yard 50 yard Muzzle
0.575 0.656 1.411 1.372
0.096 0.537 0.509 1.651
0.028 0.702 0.981 2.57
0.541 1.025 1.523 1.431
0.09 0.288 0.925 1.179
0.735 0.891 0.566 0.759
0.338 0.353 0.519 2.591
0.759 0.647 0.491 1.553
0.209 1.059 0.777 3.94
0.431 0.551 0.403 1.369
Max Dev
0.759 1.059 1.523 3.94
Min Dev
0.028 0.288 0.403 0.759
Dev Range
0.731 0.771 1.12 3.181
Mean
0.3802 0.6709 0.8105 1.8415
Median
0.3845 0.6515 0.6715 1.492
Mode
#N/A #N/A #N/A #N/A
Std Dev
0.269 0.259 0.396 0.933
Variance
0.0728 0.0673 0.157 0.870
T Test
N/A 0.0122 0.005 0.0003
I am not statistician. That being said, I think that we can draw some conclusions from this data. We're still working on it, but if we did this right, there is a statistically significant difference between each treatment series and the control series. But what does that mean?
I think it is safe to say that the control is well within the limits of precision needed by law enforcement, military and sport shooting for precision applications.
The 5 yard barrier data doesn't look significant, but it is and bears noting. One might get away with a shot such as this, but when an innocent life is on the line this is not necessarily an automatic shoot situation. The totality of the circumstances and agency policy will or should dictate the course of action or inaction. In a hunting context, the distance of the target and the effect of going through the barrier on bullet energy loss and orientation should be weighed heavily before taking this shot. Those considerations likely change drastically between an elk at 150 yards vs an elk at 500 with a barrier 0 to 5 yards in front of it.
In trials we did shoot with the barrier at 7 and 25 yards also. The deviation didn't seem to us at the time to be significant enough to include in the actual trials. I would wager now that they too would have been significant. We really started to visualize deviations at 50 yards. Deviations are starting to stack up and these situations should be avoided in all circumstances. Paraphrasing Jacob and what he said in the online training section, once the bullet goes through a barrier it has entered its terminal phase. Beginning the terminal phase 50 yards before reaching a target seems to me to be an unreasonable risk if the shot you are taking matters in either a law enforcement or sportsman's context.
The deviations witnessed by even tiny obstructions at the muzzle are significant enough that the firing position should be analyzed carefully for any sort of obstruction as it has the potential to completely ruin the shot. We measured only the deviations noted at 100 yards. Being an angular phenomenon, these deviations will only grow as distance increases. As Frank put it, this is the very reason snipers carry clippers to clear their line of fire of all such obstructions.
If there are any statisticians out there who would like to help us out with this data, I would appreciate it.
Any and all questions or comments are welcome as I don't think we can learn too much from these sorts of things.
I make no representations of what we saw other than this raw data and my own opinions. We all know what opinions are worth. I do hope that someone will find it useful in some way and can help contribute to us all learning more.
RB
My daughter recently needed to come up with a science fair project so the two needs came together to make this happen. I've talked to both Frank and Jacob and have gotten some great feedback and encouragement to do this project.
Last weekend my daughter and I went out to the range to run some preliminary trials. We made some interesting observations and were able to refine our study design.
We decided that we wanted to test shooting through a brush barrier that was placed close to the target (5 yards), midway to the target (50 yards) and very close to the muzzle (12").
Together, we built a frame and stand to hold the brush that would allow us to shoot through it in a fashion that would randomize contact with the obstructions just like would happen in real life. The size of the obstructions ranged from leaves and small green twigs to woody branches the size of a finger.
Our targets consisted of an 11"x17" piece of paper with 10 red 1" circles distributed evenly over the paper. This also helped with randomizing the portion of the brush barrier penetrated by the bullet.
We attempted to keep all variables the same, except for whether or not there was a brush barrier and the location of the brush barrier in the bullet path. We even addressed natural point of aim variations by standing up and rebuilding the position after 5 shots.
I did all the shooting while my daughter plotted impacts on her data sheet. This really helped us keep track once the bullets started doing strange things.
We took digital photos of each target up close and used the On Target application to measure the deviation of the POI from the POA. On Target is for analyzing groups. Since I fired only one shot per dot, I had to place a second shot exactly on top of the POA for the application to calculate. This was done for all shots so that variable should also be constant across all shots. Here are few images of what we did.
Brush Barrier
Conrol Group
Barrier 5 Yards from Target
Barrier 50 Yards From Target
Muzzle Barrier
Sorry, I can't get the following to display very well.
Firearm .308 Winchester 100 yards
Measured Deviation by Target
Control 5 yard 50 yard Muzzle
0.575 0.656 1.411 1.372
0.096 0.537 0.509 1.651
0.028 0.702 0.981 2.57
0.541 1.025 1.523 1.431
0.09 0.288 0.925 1.179
0.735 0.891 0.566 0.759
0.338 0.353 0.519 2.591
0.759 0.647 0.491 1.553
0.209 1.059 0.777 3.94
0.431 0.551 0.403 1.369
Max Dev
0.759 1.059 1.523 3.94
Min Dev
0.028 0.288 0.403 0.759
Dev Range
0.731 0.771 1.12 3.181
Mean
0.3802 0.6709 0.8105 1.8415
Median
0.3845 0.6515 0.6715 1.492
Mode
#N/A #N/A #N/A #N/A
Std Dev
0.269 0.259 0.396 0.933
Variance
0.0728 0.0673 0.157 0.870
T Test
N/A 0.0122 0.005 0.0003
I am not statistician. That being said, I think that we can draw some conclusions from this data. We're still working on it, but if we did this right, there is a statistically significant difference between each treatment series and the control series. But what does that mean?
I think it is safe to say that the control is well within the limits of precision needed by law enforcement, military and sport shooting for precision applications.
The 5 yard barrier data doesn't look significant, but it is and bears noting. One might get away with a shot such as this, but when an innocent life is on the line this is not necessarily an automatic shoot situation. The totality of the circumstances and agency policy will or should dictate the course of action or inaction. In a hunting context, the distance of the target and the effect of going through the barrier on bullet energy loss and orientation should be weighed heavily before taking this shot. Those considerations likely change drastically between an elk at 150 yards vs an elk at 500 with a barrier 0 to 5 yards in front of it.
In trials we did shoot with the barrier at 7 and 25 yards also. The deviation didn't seem to us at the time to be significant enough to include in the actual trials. I would wager now that they too would have been significant. We really started to visualize deviations at 50 yards. Deviations are starting to stack up and these situations should be avoided in all circumstances. Paraphrasing Jacob and what he said in the online training section, once the bullet goes through a barrier it has entered its terminal phase. Beginning the terminal phase 50 yards before reaching a target seems to me to be an unreasonable risk if the shot you are taking matters in either a law enforcement or sportsman's context.
The deviations witnessed by even tiny obstructions at the muzzle are significant enough that the firing position should be analyzed carefully for any sort of obstruction as it has the potential to completely ruin the shot. We measured only the deviations noted at 100 yards. Being an angular phenomenon, these deviations will only grow as distance increases. As Frank put it, this is the very reason snipers carry clippers to clear their line of fire of all such obstructions.
If there are any statisticians out there who would like to help us out with this data, I would appreciate it.
Any and all questions or comments are welcome as I don't think we can learn too much from these sorts of things.
I make no representations of what we saw other than this raw data and my own opinions. We all know what opinions are worth. I do hope that someone will find it useful in some way and can help contribute to us all learning more.
RB
