JimGnitecki
Member
- Joined
- Mar 28, 2010
- Messages
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This posting will describe how How I improved my rifle shooting from a bench via carefully considered ergonomic changes.
Why
This ergonomic development program started with a simple objective: I am a reasonably capable handgun shooter, and also a “casual” rifle shooter, but only a few months ago, spurred on by a close friend who shoots F-Class competition matches, I bought a PGW rifle in 6.5 Creedmoor, and a Vortex Golden Eagle 15-60x52 scope, plus all the associated required reloading equipment and supplies, to be able to shoot at long distances.
“Long distances” in my case is defined as “300 yards and potentially beyond”, simply because the only range within reasonable driving distance goes out to only 300 yards! To shoot at longer ranges regularly will ultimately require me to “commute” to ranges with longer yardages, and that means an almost 2-hour drive each way, so basically, a “day” outing to make it worthwhile! But, I’ll cross that bridge when I get to it!
I started the process of developing a suitable load, and soon realized that I was incapable of REALLY being able to properly evaluate the effects of changes in a load, because I simply could not consistently shoot proper groups that would be good enough to SEE the actual changes being produced.
This prompted me to start researching what it takes to shoot consistently enough to actually properly evaluate changes in loads, and realized that using Benchrest techniques, to some reasonable extent, might be the best way to minimize the human factor and highlight the ammunition factor.
That turned out to be a smart decision, because it improved my overall shooting accuracy and consistency rather immensely, as you will see below.
What I started with
I started with a very accurate rifle, a PGW M15 XRS in 6.5 Creedmoor. This rifle is the least costly model available from the Canadian firm PGW Defence, which primarily builds more costly very accurate sniper rifles for International military customers. It is a Remington 700 type bolt action mounted to an MDT XRS chassis.
The rifle, coming from a company used to equipping military snipers for battlefield shooting, came with a Harris bipod, and a muzzle brake. Its XRS coated-alloy chassis came with an adjustable comb and removable spacers that enable changing its 13” length of pull. There was also of course a 6 inch long 25 MOA Picatinny rail for mounting a scope. The trigger is a TriggerTech Primary 1.5 set by the factory to 4.0 lbs. This trigger is so good that I have never felt the need to adjust it lighter.
I chose to buy and mount a Vortex Golden Eagle 15-60x52 scope, which I figured would work fine at up to 1000 yards or more, and would make it easy for me to spot my shots immediately after firing them even at extended ranges, without needing to lose my position to look through a spotting scope. I mounted the scope using a one-piece mount for strong rigidity and the best chance of perfect axial alignment.
My rifle has a 24” fluted IBI 24" button rifled R5 match stainless barrel with 1:8 rifling. The factory test target showed a 0.58” 5-shot group at 101 yards (0.55 MOA). One of my first test groups, with my first self-loaded cartridges, which was only 4 shots as that was the number of test rounds I had left that day, measured 0.31” at 100 yards (0.30 MOA).
So, the rifle is clearly very accurate, but it is important to note that this did NOT represent MY accuracy at that time, as my 3-shot group sizes VARIED a LOT, with the worst being over an inch at 100 yards (i.e. over 1 MOA). So, I strongly suspected that my techniques, and specifically my personal and equipment ergonomics, needed improvement.
This is how the rifle looked upon initial commissioning:
Of course, I had already applied the few things I knew already about what it takes to shoot a rifle accurately, for example:
Still, the inconsistency of my group sizes, ranging from over 1 MOA to occasionally as good as 0.25 MOA, all shot at 100 yards, made it clear that I was shooting with an inadequate degree of control.
What reading about F-Class and Benchrest taught me
I don’t plan on becoming a benchrest shooter, but in reading everything I could find on Benchrest shooting, including two complete books dedicated to Benchrest, and authored by Benchrest champions, I could see that I had a LOT to learn that could be helpful to my shooting in general and my load development especially. And I also found that F-Class, often called “Belly Benchrest” because it is fired from a prone position using front and rear rifle supports, applies a LOT of Benchrest techniques to non-Benchrest competition.
Doing the research showed me that for the best accuracy under controlled, not necessarily field, conditions:
- You should not just accept the first shooting bench that happens to be near you or available. The height, width, depth, shape, stability, material, and surface friction of the bench make a world of difference in how comfortably, controllably, and consistently you can shoot, and how long you can keep setting up your shots, and how long you can keep firing before fatigue starts ti affect your groups.
- You cannot just randomly use whatever donated stool or chair happens to be near the shooting bench that you choose to shoot from. You need a reliably stable platform of your own that can be adjusted to the exact height that minimizes discomfort, muscle tension, and fatigue.
- It is not enough to control the front end of the rifle with a field bipod like the Harris; You want a front support that can be easily and reliably adjusted for at least height (via smooth and predictable crank), or for both height and windage (via “joystick” type control), and has as wide a base as practical.
- It is not enough to support the rear of the rifle, and also aim it, with your body, because that requires precise and strong muscle input which tires too quickly, and which transmits heart rate and even breathing pulses to the rifle, destabilizing the sight picture on the aim point. Sure, bodily supporting the rifle works when hunting, but its far too imprecise and requires too much sustained energy when attempting to discern small differences in precision grade ammunition performance. You need a rear support system that enables you to support the rifle without muscle input, that allows you to make windage adjustments that are easy and durable, and that guides the rifle straight back through its recoil cycle and enables you to return to exact POA with minimized human input required.
- You need to be able to control the comb height and length of pull rather precisely to achieve reliable and durable positioning without muscle input
- Scope height above the stock is pretty critical in order to minimize muscle and eye fatigue
- Wind management is critical (but I had (and still have) much to learn before I ever do THAT well, and fortunately, the wind is usually quite calm in the mornings when I generally like to shoot, so learning proper wind management can be delayed a bit longer).
The Changes I have made
As a result of all of the above, I have already made the following changes that I now apply to all my ammunition testing shooting sessions:
Pick the right shooting bench
I have checked to see which of the benches at our local range are solid, and now consistently use one of them. I have learned that I need the “T-shape” of a proper shooting bench to accommodate my new front bipod.I make sure that any piece of carpet left on it is removed, and replaced for my shooting session by my own rubber mat which fits under my front bipod, giving the bipod a CONSISTENT surface to slide on during recoil. And, for my setup, that rubber mat does NOT extend to under the rear support i now use, as I have found that the plain painted surface of the wood benchtop makes it far easier to adjust that rear support while setting up my shot.
Rigid adjustable height stool
I found and bought a strong, rigid, adjustable height stool that I can adjust to exactly the right height (18.25” for my body dimensions and my specific shooting position), so that I feel no muscle tension at all when setting up each shot.
Lightweight rear bag
I tried using a lightweight rear bag, which works really well for some people in certain types of rifle competition shooting (e.g. PRS), but found that it was not a good enough solution for me for ammunition testing from a bench. It required muscle tension to obtain and hold the right height for each specific shot, so I fatigued too early in my shot setup process. It also made reacquiring the target after each shot too lengthy a process.
Rear monopod
I also tried using an adjustable rear monopod. That enabled fairly rapid, consistent, and stable POA setup with no retentive muscle tension required, and could potentially be a great field solution. But, it could not control rifle recoil well enough to make subsequent shots quickly enough, and I often found myself searching for the target sheet after a shot.
Protektor DR rear bag
A Protektor DR rear bag turned out to be THE solution for me. It has a 1 inch slot (the right width for my XRS stock) between 2 ears to guide the rifle stock. It also has “Slick Silver” layer on its ears that allows the stock to slide very easily without needing a dryer sheet or silicone spray. It’s very heavy, as it is filled from the factory with “heavy” sand that makes it weigh 20 lb versus 13 lb with regular sandbag sand. It supports the rear of the rifle with NO muscle input required. Elevation is controlled by the new Remple front bipod (see below). Windage is easily and reliably controlled by sliding the bag on the wood surface of the shooting bench with very little arm effort required, and once the correct windage is achieved, no muscle inout is required. The rifle slides about 5/8 of an inch on recoil, and by simply pushing the rifle butt forward to its original position (easily indexed off the back of the bag ears), I get right back on the POA with minimized time and effort. This bag is AWESOME.
Remple Bipod
The Remple bipod did for the front of the rifle what the Protektor DR bag did for the rear. It supports the front of the rifle through the sighting and recoil processes with NO muscle input and a very wide stance. And once adjusted and clamped to hold the rifle level from side to side, it holds it very reliably thanks to its Picatinny mount. It enables very fast, easy, and reliably stable elevation changes to get you right onto the POA.
It did require the addition of a Picatinny rail to the bottom of the fore-end of the XRS chassis, as the Harris bipod it replaces (for this shooting role) mounts via s ling mount system:
I installed an aftermarket Picatinny rail to the rear of the sling mount, rather than replacing the sling mount, as I wanted to retain the ability to use the Harris bipod where the Harris might be more appropriate for the type of shooting being done (e.g. PRS):
The Remple bipod attaches and detaches via a quick disconnect built into the Remple itself.
Removed adjustable comb
The combination of above changes improved the ergonomics for me immensely, and improved my group size consistency a lot, but I was still initially consistently experiencing one adverse post-firing effect after each shot: the sight picture was moving about 10 inches to the left of POA, which indicated that the butt of the rifle was being deflected upon recoil about 0.126” to the right when shooting at 100 yards. This meant that the butt and Protektor bag were both moving to the right, with the bag sliding on the wood surface.
I eventually figured out that this was caused by the adjustable comb of the XRS chassis responding to pressure from my cheek, even when set to its lowest position, because of my apparently unusually low cheekbone. My cheekbone was deflecting the XRS chassis despite the very light cheek contact pressure.
The initial partial solution turned out to be to simply remove the adjustable comb entirely from the chassis:
This was possible for me to do because I use basically a “free recoil” hold on my rifle to avoid transmitting heart beat, breathing effects, and unintentional muscle tension to the rifle. The cheek contact is entirely unnecessary with the Protektor bag replacing it.
Moved scope more forward
Note that in the above ergonomic mod, I removed the adjustable comb. But you can see from the above photo of the rifle that the stock of the XRS chassis behind the adjustable comb is still quite high - as high as the lowest position of the adjustable comb, which was already too high for my cheekbone. So, even after removing the adjustable comb, I was still getting some contact with the FIXED portion of the stock.
The remedy was to move the scope mount forward on its Picatinny rail enough to eliminate that issue. If you look at this next photo, and compare it to the first photo in this posting, you will see that the rear scope cap now aligns with the FRONT bottom edge of the pistol grip, versus with the REAR bottom edge of the pistol grip.
This simply allowed me to position my head slightly forward to clear the fixed upper portion of the stock, while retaining the full correct sight picture in the scope.
Altered XRS stock length via removable spacers
Since I had now moved my head forward by about an inch or more, I figured it was now desirable to shorten the length of pull as well. That would allow me to have my right arm slightly more relaxed in my shooting position. So, I removed the 2 butt spacers. However, I then ran into a new problem: When I now wrapped my right arm around the rear of the shortened butt, my right arm was hitting, and MOVING, the Protektor rear bag. I could not simply slide the rifle butt further rearward in the Protektor bag, because the bottom of the stock on the XRS chassis is only level for a short distance forward from the butt and then goes “concave” (look at this photo):
Taking out the butt spacers had made the deeper portion of the stock too short to properly engage the Protektor bag if I moved the rifle rearward. So, I put the spacers back in, and lived with the slightly longer length of pull.
Raised scope via a Picatinny riser rail
I wear eyeglasses with progressive lenses. I realized that I was looking into the scope through the upper most portion of the right eye lens. This was creating 2 subtle issues. The first was that I was looking through the portion of the lens intended to provide the clearest LONG DISTANCE focus, but I was trying to focus on something very close: the reticle. In addition, I realized I was just a bit uncomfortable ergonomically getting my head low enough to get the proper scope sight picture. I realized that it would probably help to get the scope mounted a bit higher.
In theory, that would be “worse” in the sense that it would require even more holding the rifle completely level. But my homemade (laser printed) paper targets that I use for ammunition testing have a crosshair POA that makes it easy for me to ensure I am level by simply aligning my reticle crosshairs with the target crosshairs. So, no problem there.
The easiest way to get the extra height, while retaining the sturdiness and superior alignment of my one piece mount was to buy a Picatinny riser rail that fits between the rifle’s Picatinny rail and the one piece Picatinny mount. I chose the Wheeler Picatinny rail, in a half inch height, and a 6 inch length that matched the length of the rifle’s Picatinny rail, and thus gave me maximized odds of perfect or near perfect axial alignment with the rifle.
You can see the riser rail in this photo:
Recognized that the XRS chassis may not be adjustable enough to be ideal for my usage
The above sequence of diagnostics and ergonomic improvements have shown me that the MDT XRS chassis, while probably a great chassis for most people, is not a great chassis for me, at least when bench testing ammunition, because:
Results of these ergonomic improvements
The results of the above program of ergonomic changes has had a favourable effect on the size of my “best” groups, but more importantly a GREAT effect on the CONSISTENCY of my group sizes (i.e. a great effect on ALL my groups, not just the best ones).
I have been shooting 3-shot groups because until recently I became fatigued enough after 30 rounds fired to stop the session, because I was then testing my endurance, no longer purely the ammunition! But I plan to formally go to 5-shot groups, and 300 yards, starting with my next load testing range session. The results of my last session, still done with 3-shot groups, at 200 yards versus the earlier 100 yards, can therefor be properly compared on an MOA basis to the earlier groups. In fact, since shooting accurately at 200 yards is obviously more difficult than at 100 yards, the improvements that I have now gotten are actually a bit understated.
So, here we go: At my last fully documented and measured ammunition testing shooting session, shot at 200 yards, shooting 3-shot groups:
The average (average, not best) group size was 0.50” (under 0.25 MOA at 200 yards!)
The best group size was 0.25” (0.12 MOA).
The std dev in group size was 0.20” (under 0.1 MOA at 200 yards), which is a big improvement over my previous consistency.
The extreme spread was 0.50” (0.24 MOA)
So, yes, paying attention to ergonomics, and making appropriate personalized improvements that are targeted to the specific type of shooting being done, does make a big difference.
Jim G
Why
This ergonomic development program started with a simple objective: I am a reasonably capable handgun shooter, and also a “casual” rifle shooter, but only a few months ago, spurred on by a close friend who shoots F-Class competition matches, I bought a PGW rifle in 6.5 Creedmoor, and a Vortex Golden Eagle 15-60x52 scope, plus all the associated required reloading equipment and supplies, to be able to shoot at long distances.
“Long distances” in my case is defined as “300 yards and potentially beyond”, simply because the only range within reasonable driving distance goes out to only 300 yards! To shoot at longer ranges regularly will ultimately require me to “commute” to ranges with longer yardages, and that means an almost 2-hour drive each way, so basically, a “day” outing to make it worthwhile! But, I’ll cross that bridge when I get to it!
I started the process of developing a suitable load, and soon realized that I was incapable of REALLY being able to properly evaluate the effects of changes in a load, because I simply could not consistently shoot proper groups that would be good enough to SEE the actual changes being produced.
This prompted me to start researching what it takes to shoot consistently enough to actually properly evaluate changes in loads, and realized that using Benchrest techniques, to some reasonable extent, might be the best way to minimize the human factor and highlight the ammunition factor.
That turned out to be a smart decision, because it improved my overall shooting accuracy and consistency rather immensely, as you will see below.
What I started with
I started with a very accurate rifle, a PGW M15 XRS in 6.5 Creedmoor. This rifle is the least costly model available from the Canadian firm PGW Defence, which primarily builds more costly very accurate sniper rifles for International military customers. It is a Remington 700 type bolt action mounted to an MDT XRS chassis.
The rifle, coming from a company used to equipping military snipers for battlefield shooting, came with a Harris bipod, and a muzzle brake. Its XRS coated-alloy chassis came with an adjustable comb and removable spacers that enable changing its 13” length of pull. There was also of course a 6 inch long 25 MOA Picatinny rail for mounting a scope. The trigger is a TriggerTech Primary 1.5 set by the factory to 4.0 lbs. This trigger is so good that I have never felt the need to adjust it lighter.
I chose to buy and mount a Vortex Golden Eagle 15-60x52 scope, which I figured would work fine at up to 1000 yards or more, and would make it easy for me to spot my shots immediately after firing them even at extended ranges, without needing to lose my position to look through a spotting scope. I mounted the scope using a one-piece mount for strong rigidity and the best chance of perfect axial alignment.
My rifle has a 24” fluted IBI 24" button rifled R5 match stainless barrel with 1:8 rifling. The factory test target showed a 0.58” 5-shot group at 101 yards (0.55 MOA). One of my first test groups, with my first self-loaded cartridges, which was only 4 shots as that was the number of test rounds I had left that day, measured 0.31” at 100 yards (0.30 MOA).
So, the rifle is clearly very accurate, but it is important to note that this did NOT represent MY accuracy at that time, as my 3-shot group sizes VARIED a LOT, with the worst being over an inch at 100 yards (i.e. over 1 MOA). So, I strongly suspected that my techniques, and specifically my personal and equipment ergonomics, needed improvement.
This is how the rifle looked upon initial commissioning:
Of course, I had already applied the few things I knew already about what it takes to shoot a rifle accurately, for example:
- Mount the scope so that when you hold the rifle in your desired shooting position and open your eyes, the sight picture is there without any extra movement being required to get it
- Set the bipod height to keep the rifle positioned level front to rear
- Find a shooting position and posture and hold that work for you
- Optimize your hold and position to minimize transmission of your heart beat to the rifle
- Proper breath control
- Focus on the reticle, not the target
- Proper trigger squeeze
Still, the inconsistency of my group sizes, ranging from over 1 MOA to occasionally as good as 0.25 MOA, all shot at 100 yards, made it clear that I was shooting with an inadequate degree of control.
What reading about F-Class and Benchrest taught me
I don’t plan on becoming a benchrest shooter, but in reading everything I could find on Benchrest shooting, including two complete books dedicated to Benchrest, and authored by Benchrest champions, I could see that I had a LOT to learn that could be helpful to my shooting in general and my load development especially. And I also found that F-Class, often called “Belly Benchrest” because it is fired from a prone position using front and rear rifle supports, applies a LOT of Benchrest techniques to non-Benchrest competition.
Doing the research showed me that for the best accuracy under controlled, not necessarily field, conditions:
- You should not just accept the first shooting bench that happens to be near you or available. The height, width, depth, shape, stability, material, and surface friction of the bench make a world of difference in how comfortably, controllably, and consistently you can shoot, and how long you can keep setting up your shots, and how long you can keep firing before fatigue starts ti affect your groups.
- You cannot just randomly use whatever donated stool or chair happens to be near the shooting bench that you choose to shoot from. You need a reliably stable platform of your own that can be adjusted to the exact height that minimizes discomfort, muscle tension, and fatigue.
- It is not enough to control the front end of the rifle with a field bipod like the Harris; You want a front support that can be easily and reliably adjusted for at least height (via smooth and predictable crank), or for both height and windage (via “joystick” type control), and has as wide a base as practical.
- It is not enough to support the rear of the rifle, and also aim it, with your body, because that requires precise and strong muscle input which tires too quickly, and which transmits heart rate and even breathing pulses to the rifle, destabilizing the sight picture on the aim point. Sure, bodily supporting the rifle works when hunting, but its far too imprecise and requires too much sustained energy when attempting to discern small differences in precision grade ammunition performance. You need a rear support system that enables you to support the rifle without muscle input, that allows you to make windage adjustments that are easy and durable, and that guides the rifle straight back through its recoil cycle and enables you to return to exact POA with minimized human input required.
- You need to be able to control the comb height and length of pull rather precisely to achieve reliable and durable positioning without muscle input
- Scope height above the stock is pretty critical in order to minimize muscle and eye fatigue
- Wind management is critical (but I had (and still have) much to learn before I ever do THAT well, and fortunately, the wind is usually quite calm in the mornings when I generally like to shoot, so learning proper wind management can be delayed a bit longer).
The Changes I have made
As a result of all of the above, I have already made the following changes that I now apply to all my ammunition testing shooting sessions:
Pick the right shooting bench
I have checked to see which of the benches at our local range are solid, and now consistently use one of them. I have learned that I need the “T-shape” of a proper shooting bench to accommodate my new front bipod.I make sure that any piece of carpet left on it is removed, and replaced for my shooting session by my own rubber mat which fits under my front bipod, giving the bipod a CONSISTENT surface to slide on during recoil. And, for my setup, that rubber mat does NOT extend to under the rear support i now use, as I have found that the plain painted surface of the wood benchtop makes it far easier to adjust that rear support while setting up my shot.
Rigid adjustable height stool
I found and bought a strong, rigid, adjustable height stool that I can adjust to exactly the right height (18.25” for my body dimensions and my specific shooting position), so that I feel no muscle tension at all when setting up each shot.
Lightweight rear bag
I tried using a lightweight rear bag, which works really well for some people in certain types of rifle competition shooting (e.g. PRS), but found that it was not a good enough solution for me for ammunition testing from a bench. It required muscle tension to obtain and hold the right height for each specific shot, so I fatigued too early in my shot setup process. It also made reacquiring the target after each shot too lengthy a process.
Rear monopod
I also tried using an adjustable rear monopod. That enabled fairly rapid, consistent, and stable POA setup with no retentive muscle tension required, and could potentially be a great field solution. But, it could not control rifle recoil well enough to make subsequent shots quickly enough, and I often found myself searching for the target sheet after a shot.
Protektor DR rear bag
A Protektor DR rear bag turned out to be THE solution for me. It has a 1 inch slot (the right width for my XRS stock) between 2 ears to guide the rifle stock. It also has “Slick Silver” layer on its ears that allows the stock to slide very easily without needing a dryer sheet or silicone spray. It’s very heavy, as it is filled from the factory with “heavy” sand that makes it weigh 20 lb versus 13 lb with regular sandbag sand. It supports the rear of the rifle with NO muscle input required. Elevation is controlled by the new Remple front bipod (see below). Windage is easily and reliably controlled by sliding the bag on the wood surface of the shooting bench with very little arm effort required, and once the correct windage is achieved, no muscle inout is required. The rifle slides about 5/8 of an inch on recoil, and by simply pushing the rifle butt forward to its original position (easily indexed off the back of the bag ears), I get right back on the POA with minimized time and effort. This bag is AWESOME.
Remple Bipod
The Remple bipod did for the front of the rifle what the Protektor DR bag did for the rear. It supports the front of the rifle through the sighting and recoil processes with NO muscle input and a very wide stance. And once adjusted and clamped to hold the rifle level from side to side, it holds it very reliably thanks to its Picatinny mount. It enables very fast, easy, and reliably stable elevation changes to get you right onto the POA.
It did require the addition of a Picatinny rail to the bottom of the fore-end of the XRS chassis, as the Harris bipod it replaces (for this shooting role) mounts via s ling mount system:
I installed an aftermarket Picatinny rail to the rear of the sling mount, rather than replacing the sling mount, as I wanted to retain the ability to use the Harris bipod where the Harris might be more appropriate for the type of shooting being done (e.g. PRS):
The Remple bipod attaches and detaches via a quick disconnect built into the Remple itself.
Removed adjustable comb
The combination of above changes improved the ergonomics for me immensely, and improved my group size consistency a lot, but I was still initially consistently experiencing one adverse post-firing effect after each shot: the sight picture was moving about 10 inches to the left of POA, which indicated that the butt of the rifle was being deflected upon recoil about 0.126” to the right when shooting at 100 yards. This meant that the butt and Protektor bag were both moving to the right, with the bag sliding on the wood surface.
I eventually figured out that this was caused by the adjustable comb of the XRS chassis responding to pressure from my cheek, even when set to its lowest position, because of my apparently unusually low cheekbone. My cheekbone was deflecting the XRS chassis despite the very light cheek contact pressure.
The initial partial solution turned out to be to simply remove the adjustable comb entirely from the chassis:
This was possible for me to do because I use basically a “free recoil” hold on my rifle to avoid transmitting heart beat, breathing effects, and unintentional muscle tension to the rifle. The cheek contact is entirely unnecessary with the Protektor bag replacing it.
Moved scope more forward
Note that in the above ergonomic mod, I removed the adjustable comb. But you can see from the above photo of the rifle that the stock of the XRS chassis behind the adjustable comb is still quite high - as high as the lowest position of the adjustable comb, which was already too high for my cheekbone. So, even after removing the adjustable comb, I was still getting some contact with the FIXED portion of the stock.
The remedy was to move the scope mount forward on its Picatinny rail enough to eliminate that issue. If you look at this next photo, and compare it to the first photo in this posting, you will see that the rear scope cap now aligns with the FRONT bottom edge of the pistol grip, versus with the REAR bottom edge of the pistol grip.
This simply allowed me to position my head slightly forward to clear the fixed upper portion of the stock, while retaining the full correct sight picture in the scope.
Altered XRS stock length via removable spacers
Since I had now moved my head forward by about an inch or more, I figured it was now desirable to shorten the length of pull as well. That would allow me to have my right arm slightly more relaxed in my shooting position. So, I removed the 2 butt spacers. However, I then ran into a new problem: When I now wrapped my right arm around the rear of the shortened butt, my right arm was hitting, and MOVING, the Protektor rear bag. I could not simply slide the rifle butt further rearward in the Protektor bag, because the bottom of the stock on the XRS chassis is only level for a short distance forward from the butt and then goes “concave” (look at this photo):
Taking out the butt spacers had made the deeper portion of the stock too short to properly engage the Protektor bag if I moved the rifle rearward. So, I put the spacers back in, and lived with the slightly longer length of pull.
Raised scope via a Picatinny riser rail
I wear eyeglasses with progressive lenses. I realized that I was looking into the scope through the upper most portion of the right eye lens. This was creating 2 subtle issues. The first was that I was looking through the portion of the lens intended to provide the clearest LONG DISTANCE focus, but I was trying to focus on something very close: the reticle. In addition, I realized I was just a bit uncomfortable ergonomically getting my head low enough to get the proper scope sight picture. I realized that it would probably help to get the scope mounted a bit higher.
In theory, that would be “worse” in the sense that it would require even more holding the rifle completely level. But my homemade (laser printed) paper targets that I use for ammunition testing have a crosshair POA that makes it easy for me to ensure I am level by simply aligning my reticle crosshairs with the target crosshairs. So, no problem there.
The easiest way to get the extra height, while retaining the sturdiness and superior alignment of my one piece mount was to buy a Picatinny riser rail that fits between the rifle’s Picatinny rail and the one piece Picatinny mount. I chose the Wheeler Picatinny rail, in a half inch height, and a 6 inch length that matched the length of the rifle’s Picatinny rail, and thus gave me maximized odds of perfect or near perfect axial alignment with the rifle.
You can see the riser rail in this photo:
Recognized that the XRS chassis may not be adjustable enough to be ideal for my usage
The above sequence of diagnostics and ergonomic improvements have shown me that the MDT XRS chassis, while probably a great chassis for most people, is not a great chassis for me, at least when bench testing ammunition, because:
- It is apparently designed for people with more typical cheekbone placement and width than I have
- It has limited adjustability for both reducing comb height and for shortening length of pull to adapt to my facial dimensions
- It’s obviously designed for general shooting, versus free recoil precision ammunition test firing
Results of these ergonomic improvements
The results of the above program of ergonomic changes has had a favourable effect on the size of my “best” groups, but more importantly a GREAT effect on the CONSISTENCY of my group sizes (i.e. a great effect on ALL my groups, not just the best ones).
I have been shooting 3-shot groups because until recently I became fatigued enough after 30 rounds fired to stop the session, because I was then testing my endurance, no longer purely the ammunition! But I plan to formally go to 5-shot groups, and 300 yards, starting with my next load testing range session. The results of my last session, still done with 3-shot groups, at 200 yards versus the earlier 100 yards, can therefor be properly compared on an MOA basis to the earlier groups. In fact, since shooting accurately at 200 yards is obviously more difficult than at 100 yards, the improvements that I have now gotten are actually a bit understated.
So, here we go: At my last fully documented and measured ammunition testing shooting session, shot at 200 yards, shooting 3-shot groups:
The average (average, not best) group size was 0.50” (under 0.25 MOA at 200 yards!)
The best group size was 0.25” (0.12 MOA).
The std dev in group size was 0.20” (under 0.1 MOA at 200 yards), which is a big improvement over my previous consistency.
The extreme spread was 0.50” (0.24 MOA)
So, yes, paying attention to ergonomics, and making appropriate personalized improvements that are targeted to the specific type of shooting being done, does make a big difference.
Jim G
Last edited:
