Hey, guys. A ton of readers and buddies have requested for an replace on my underground vary. A few years in the past, I printed an article that shared all the small print of a 100-yard rifle vary that I used to be constructing at my new home. I used to be already beneath building, however I additionally requested my readers for enter on methods to end it out. And wow, you guys have been useful! I truly modified fairly a bit based mostly on feedback from that put up. Because of all of you who weighed in!
The preliminary building was full, and the tunnel first went into use in December 2022, though I’ve nonetheless been working to instrument and outfit it. I prefer to tinker, so I’ll proceed to enhance it endlessly, however I’ll go forward and share a walk-through of the tunnel because it sits at the moment and briefly share what I’m contemplating including sooner or later.
The unique article shared why I used to be constructing this, drawings, building photographs, and extra. I gained’t repeat that content material right here. I would counsel beginning with that article or not less than referencing it in case you are questioning about one thing that wasn’t lined. Unique Article: https://precisionrifleblog.com/2021/12/27/100-yard-underground-range/
Here’s a fast walk-through video:
Now, I’ll stroll by a couple of specifics that I modified because the plans I shared within the authentic article.
Skilled Air flow Design
There have been plenty of feedback concerning the air air flow in my authentic put up. I felt like I’d learn quite a bit about vary air flow design and had already talked to a number of consultants – however it grew to become obvious that it was a really specialised subject. Lead poisoning is a severe well being concern for indoor ranges, so I made a decision to rent Carey’s Small Arms Vary Air flow to totally engineer/design a variety air flow resolution for this setup. Carey’s has accomplished over 1,000 indoor vary air flow techniques! They offered full drawings, specified all the vital tools, and coordinated with my native HVAC installer. Additionally they assured the system would meet all present EPA, OSHA, and NIOSH requirements for air high quality.
The primary design they got here up with was extraordinarily complicated and would have required that I drop the ceiling top within the shooter’s room from 9 ft all the way down to 7.5’ – which might have dramatically modified the texture of the area. It additionally required $25,000+ price of apparatus! The airflow that this method was able to transferring was drastically over-engineered for my challenge, however listed here are the plans for that authentic design they offered, in case it’s useful for others who is likely to be contemplating a bigger area.
I requested the engineer I used to be working with if he might talk about this challenge with different engineers to see if there have been alternate options. By some collaboration, the Carey’s workforce was in a position to dramatically simplify the design and nonetheless accomplish the airflow necessities we have been focusing on. So listed here are the plans that I ended up implementing in my underground vary: Last HVAC Design & Tools from Carey’s Small Arms Vary Air flow.
Listed below are a couple of keys I realized about vary air flow:
I initially thought an excessive amount of airflow couldn’t be a nasty factor, proper? However, an excessive amount of airflow typically creates air turbulence and backflow of contaminated air – that means dangerous air might find yourself again by the shooter. What you truly need is “laminar airflow,” which suggests a easy and steady airflow that could be very uniform in a single route. That’s how air flow techniques are designed to work in labs and surgical procedure rooms. For an indoor vary, you need the air to move from behind the shooter all the best way all the way down to the goal after which exhaust out – all in a really regular, uniform manner.
To get that regular airflow, you at all times need to pull air from the goal – and never push air from the shooter’s place.
I’m proud of how the air flow system works at the moment. It turned out that I didn’t want to maneuver close to as a lot air as I had initially deliberate. There was so little air that we have been in a position to eliminate the recent air consumption, and the air flow system merely pulled conditioned air from my store that’s instantly above it. The HVAC models we used to warmth/cool my store have been sufficiently big that they’re in a position to sustain even when the vary exhaust fan is on. That was an enormous simplification for this complete challenge.
The exhaust fan is put in instantly above the goal (proven above) and is completely aligned with the tunnel so it doesn’t create turbulent air. The velocity of the exhaust fan is adjustable by turning a dial on the wall contained in the shooter’s room. I nearly at all times shoot by the 12” x 12” porthole with the blast doorways closed, which suggests I actually solely want to maneuver round 1 mph of air by that small 1 sq. foot space and may run the fan at a low velocity to attain that.
There’s not less than 3 ft of grime above the roof of the tunnel, and I insulated the shooter and goal room – so the temperature stays surprisingly steady in them year-round. Nevertheless, I can open the blast door to the shooter room and switch the exhaust fan velocity all the best way up if I ever have to flush out the tunnel to verify the air temperature is completely uniform all through.
Measuring Velocities: The EVO Ballistix EB-MK ONE
The most important delay in posting this replace on my tunnel was associated to discovering a dependable and correct technique to file velocities. I used to be initially hoping that my Lab Radar would be capable of file velocities within the tunnel. I used to be lucky to get linked with Man Desbiens, the president of Infinition (the corporate that makes the Lab Radar and likewise makes high-end military-grade radars), and he thought it is likely to be a problem to get the Lab Radar to get readings in my vary. He did give me a couple of ideas for methods to configure and place the Lab Radar to present it the very best shot, and he was genuinely curious to see if it labored. I examined it within the tunnel earlier than we enclosed the basement, and it did give me readings – however as soon as the area was completed out, I attempted it once more. After attempting it in a number of positions, I discovered a manner I might often get readings, however they have been off by 1000 fps. The signal-to-noise ratio within the radar knowledge was just too excessive to provide correct velocities.
I additionally tried the brand new Garmin Xero C1 Professional Chronograph in my tunnel, and it additionally wasn’t in a position to present any velocity measurements. I might suspect that the radars might not be capable of kind out the sign from the noise, which can be associated to the enclosed area and/or the corrugated pipe.
So, the one manner I might file bullet velocities in my tunnel for a couple of months was if I used a MagnetoSpeed v3 Chronograph. I actually didn’t like that as my resolution as a result of it’s important to dangle that gadget from the barrel – which impacts barrel harmonics and modifications your level of impression. So while you use that gadget, you’ll be able to’t shoot teams or verify your zero and file velocities on the similar time.
My objective is to discover a very correct and dependable technique to measure velocities with out having to connect something to the rifle. Man stated that Infinition makes a 35GHz radar, the BR-3503, that might for positive work – however it’s across the $50,000 value level. That’s fairly the soar from the consumer-grade units I’ve been utilizing, so I wished to discover different choices earlier than I went in that route.
After I printed that authentic article, Marc Erneke from Germany reached out to me and stated they have been within the early levels of growing a brand new Doppler radar. I had a Zoom name with them, they usually confirmed me the product and talked by the capabilities. On the time, I used to be nonetheless hoping my Lab Radar may be capable of get correct readings, however as soon as I spotted it wouldn’t, I reached again out to them.
Marc was supremely assured that their radar would get correct readings in my tunnel. The truth is, he informed me they’d efficiently measured velocities in tunnels as slender as 2 ft in diameter! Their radar doesn’t operate just like the Lab Radar or different consumer-grade Doppler radars. The usage of the fixed wave Doppler radar expertise permits for dramatically extra measurements of the returning radar sign. It additionally takes most of its measurements inside 30 meters of the rifle, that means there would theoretically be much less interference from the tunnel.
So, I ended up buying an EVO Ballistix EB-MK ONE Doppler radar, which is made in Germany. This radar is certainly a professional-grade gadget, and I paid $17,200 for the unit. The EB-MK ONE radar is at the moment being utilized by the German navy, HK, CZ, and others. It took a couple of months for me to truly obtain the unit because it needed to ship from Germany and be imported by US Customs. As soon as I acquired it, Marc helped me get all of it up and working, and positive sufficient, we have been in a position to get correct measurements!
I haven’t used the EB-MK ONE a lot at this level, so I don’t really feel like I may give an trustworthy overview of it but. It does a lot greater than merely measure velocity. It has a TON of superior analytics capabilities, together with entry to the uncooked radar knowledge, spectral evaluation of shot exit occasions, the flexibility to construct customized drag fashions, and far more. They even say that as a result of the unit makes use of fixed wave Doppler radar expertise and has a excessive measuring charge, it’s even attainable to detect even smaller particles together with the bullet, like tiny kernels of unburnt powder leaving the muzzle. The unit takes as much as 20 million measurements per second, which suggests the EB-MK ONE is able to detecting the slightest modifications within the sign, which lets you analyze the spin and tumble (pitch/yaw) of a bullet.
I hope to get to spend a while exploring the EB-MK ONE superior capabilities sooner or later and will do a full overview sooner or later.
Bullet Lure & Goal Room
My authentic plan for a bullet entice was to construct a wall of ballistic rubber blocks, like Vary Techniques Dura-Bloc. I researched plenty of choices, and in a type of conversations, I bought some useful recommendation from an trade professional that as these ballistic rubber blocks soak up bullets, they’ll bloat. After absorbing hundreds of rounds, they’ll develop into so rounded that the wall would not be steady. That is sensible when you consider it. These are dense rubber blocks to start with, so these bullets have to extend the scale of the block over time.
I nonetheless preferred the thought of a bullet entice that fully encapsulates the bullet. Conventional indoor bullet traps are often typically only a massive pile of items of free rubber. When a bullet hits that, it tumbles and comes aside, exposing the lead core – and lead publicity is a really severe well being concern. When an indoor vary has to do upkeep on a conventional bullet entice, they usually have to rent a specialty service to do it with Hazmat fits on. I wished to have the ability to go downrange to do upkeep or verify the goal with out a excessive threat of lead publicity.
What I landed on is The Bullet Bunker Goliath 4’ x 4’ bullet entice, which is rated from .22 rimfire as much as 375 RUM. I verified with the producer that it might take a 300 Norma Magazine and 338 Lapua Magazine as a result of these are the biggest cartridges I plan to make use of at this level. I do personal a 375 CheyTac and 50 BMG, however I’m fairly positive I’d slightly shoot these open air than in an enclosed area.
The Bullet Bunker design is type of a combination between the ballistic rubber blocks and a conventional bullet entice with free rubber. The unit nonetheless totally encapsulates a bullet (that means no lead publicity in my goal room), however contained in the field are small items of rubber. The bullet entice can take over 10,000 rounds earlier than any service is required – and doubtlessly much more, relying on the calibers and the way concentrated the pictures are. The hinged collar design makes the upkeep very easy. I purchased a alternative panel for $300, which could not be wanted for 10,000-50,000, they usually threw in two 50-pound containers of ballistic media, which they stated needs to be all I want for not less than 50,000 rounds. That feels like a lifetime!
I purchased the bottom and casters for the Goliath bullet entice, which completely centered the bullet entice in my 8-foot diameter tunnel. The inexperienced deflector across the outdoors is 48” x 48”, with the shootable rubber space measuring 42” x 42”. The totally assembled unit weighs over 2,000 lbs. (View drawing with dimensions)
Because the tunnel diameter is bigger than the bullet entice, I continued with my authentic plan so as to add a 1/2” thick AR500 metal plate on the wall behind it – simply in case a bullet ever misses the 4’x4’ inexperienced sq.. I truthfully can’t bear in mind a time I used to be firing at a paper goal at 100 yards and missed it by ft – however simply in case. On high of the metal plate, I added 20 Vary System Dura-Panels. These are 24” x 24” panels of ballistic rubber which can be 2” thick, and I glued them onto the plate with the 3M 550 adhesive that Vary Techniques recommends. These panels can soak up and encapsulate bullets and fragments, however additionally they scale back the echo/sound reflection dramatically.
I did get an additional giant 36” x 96” roof hatch within the goal room in case I ever need to change the bullet entice. The truth is, we used a crane to decrease the Goliath bullet entice by the roof hatch to set it in place, which labored nicely. The roof hatch serves as a 2nd exit to the tunnel because the tunnel additionally serves as a twister shelter for my household and as much as 500 buddies. 😉 I maintain an extension ladder within the goal room for such an event.
I wished very flat/even lighting on the goal, so I used LED mild strips and mounted these across the mouth of the tunnel. They’re all linked to particular plugs that may be switched on/off from the shooter’s room. The lights alongside the within of the tunnel are additionally on a devoted swap within the shooter’s room.
For now, I’ve merely hooked up a corrugated plastic sheet and paper goal instantly onto the bullet entice. My plan is to construct a free-standing metal goal stand in entrance of the bullet entice, however I haven’t fairly determined how the goal system will work. I’d like an digital goal system that may show the pictures on a display screen subsequent to the shooter, and likewise run analytics on the teams (like common distance to heart) and save the goal digitally together with meta-data like date, rifle, ammo, and so forth..
I’ve researched a number of techniques, and it seems that the Kongsberg Goal System is the gold commonplace. It’s utilized by the US Military Marksmanship Unit, Lapua, and in a number of of probably the most prestigious competitions on this planet. Nevertheless, it’s not with out its flaws. It doesn’t seem to do all the things I’m hoping for, and I’ve heard that Lapua isn’t actually proud of it. I would like the goal stand to have the ability to seamlessly combine and accommodate no matter digital goal system I find yourself going with, so I’m simply utilizing paper and strolling downrange till I decide on the system.
The most important concern is discovering one thing that works indoors and permits a number of aiming factors. Should you hearth hundreds of pictures within the very heart of a goal, you’ll destroy the middle of the bullet entice. Additionally, since I’m capturing precision rifles right into a 42” x 42” capturing space at 100 yards, it solely is sensible to make use of a number of aiming factors, just like all of the little aiming dots I’ve on the goal now. Discovering an answer that may do this and performance in an indoor vary could also be tough.
If nothing else, I even have a level in Pc Science, and I might use a distant digicam to seize the pictures and write my very own software program to do the evaluation and save the output. I’m hoping to not resort to that. Actually, utilizing paper targets simply isn’t that inconvenient for me for the time being, both.
Should you guys know of a superb system that may meet my wants, please let me know within the feedback!
Blast Doorways & Acoustic Panels
I personally designed the blast doorways, that are the 2 doorways between the shooter and the tunnel. The concept is that you simply stick the muzzle by a porthole, and the majority of the concussion occurs within the “enlargement chamber,” which is what I name the room between the shooter and tunnel. It is a design {that a} good friend at Accuracy Worldwide advised, and it really works amazingly! I believe it was a recreation changer when it comes to decreasing the concussion the shooter experiences.
The blast doorways are constructed from 80/20 components, which is sort of a professional-grade erector set that many labs use for customized fixtures, tools, customized benches, or different makes use of. It’s based mostly round T-slot profiles constructed from aluminum, however they appear to make something you could possibly dream up! They’ve all types of equipment, like mounting brackets, hinges, the ¼” clear polycarbonate panels I added, door handles, gaskets, and all types of stuff. It’s a rabbit gap for an engineer!
What I like concerning the 80/20 is that it’s not solely modular but in addition extraordinarily extensible. I can mainly instantly mount something to those doorways. If I ever need to instantly mount a radar, show monitor, gradual movement digicam, or different tools, I might connect these just about anyplace on these doorways – and in quite a lot of methods.
This was one other half I hadn’t ever seen achieved, so it felt dangerous – however the doorways labored nice and have been all the things I hoped they’d be. I labored with Shepherd Controls (a accomplice with 80/20) to determine precisely what components and portions I wanted to tug off my design, after which I assembled all of it. Right here is an itemized order with all of the components for my blast doorways.
I hung two acoustic blankets on either side of the blast chamber room. I sized the room so these 4’ large x 8’ tall blankets dangle freely with out touching the flooring or partitions, however they solely had a few inches of clearance. I purchased AlphaSorb Twin-Sided Absorptive Sound Blanket in 4’x8’ panels from Acoustical Options, which is constructed utilizing two layers of 1 in. thick specialised acoustical fiberglass batting and contains a sturdy vinyl-coated fiberglass fabric going through. These blankets have an NRC score of 0.85, which suggests they’ve been examined in a lab and proven to soak up 85% of the sound over all frequencies the human ear can hear! Should you evaluate that to different merchandise you usually see in indoor ranges, you’ll see that’s ridiculous efficiency. The vinyl coating is very good so to simply wipe them down as wanted.
I used to be initially planning so as to add acoustic panels to the ceiling above the shooter and within the blast chamber, and I additionally thought I might probably add some on the partitions on both facet of the shooter. However, after capturing within the area for some time (even with a lot of the rifles being outfitted with a muzzle brake), I believe the blast chamber and acoustic blankets do a surprisingly nice job at decreasing concussion. Don’t get me fallacious – it’s nonetheless loud while you’re capturing a muzzle brake, however there isn’t a lot concussion. I could decide so as to add panels on the partitions and ceiling sooner or later – however I doubt it.
Customized Taking pictures Bench/Desk
I designed a customized capturing bench that I can both sit at or lie down susceptible on high of. I fabricated and welded the bottom myself out of thick metal tubing. Many of the metal is 3.5” sq. tubing that’s 3/16” thick. The highest is a 2-inch thick, onerous maple butcherblock that’s 10 ft lengthy and 4 ft large. The full weight of the desk could be very near 900 lbs! The desk is sitting on leveling machine casters with retractable anti-vibration pads. I wished it to be stable and never budge a fraction of an inch beneath recoil. I nailed that objective! This desk is superior!
The peak of the desk is 34 inches from the ground to the highest of the bench, which is good for me. I debated on the bench top for some time! After a bunch of analysis, it looks as if 32-36” bench top is the commonest. I truly did all of the calculations and design for the bench top earlier than the pipe for the tunnel was even set within the floor, so I dropped the pipe a couple of inches beneath the ground of the shooter’s room in order that when a rifle with a bipod is on the 34” tall bench, it will be completely centered contained in the tunnel.
Dropping the tunnel a couple of inches beneath the basement ground appeared like a good suggestion in case it ever flooded, that might assist maintain the water from going into my basement. The goal room is one more few inches decrease than the tunnel, that means the water would pool in that room. So, if I ever did get water inside it, I might drop a pump within the goal room and get all the water out from that facet. Fortunately, the factor appears sealed very nicely as a result of I haven’t bought any water in even when it rained for days.
I discussed that I can lay susceptible on the desk. After I minimize out the realm for the seated place, I used to be cautious to take it out in a single piece. So I can slip that again on the highest and have an angle iron beneath the butcherblock high to help it within the entrance, and the backrest helps it within the rear. It mainly makes it like one giant flat desk once more. I designed it the place I might minimize out the opposite facet for a left-handed shooter, however for now, they’ll need to go susceptible. Actually, this complete underground vary is primarily for me to shoot in to do load improvement, experiments, and verify my zero. I don’t plan to ask buddies over to shoot in it. I’ll say that it was an additional lengthy desk, so I had loads of area to unfold out susceptible, however having the additional area on the finish offers me a spot to set rifles, gear, or I can use it as a workbench with out something being in my technique to shoot. I didn’t plan that, however it’s good!
Listed below are my plans for the desk with dimensions:
How does it really feel? What would I modify if I did it once more?
I truthfully had by no means seen or heard of an underground vary that was designed like this, so it felt like I used to be taking a couple of important dangers – and I wasn’t positive how they’d end up. However I’m very proud of the outcomes. I want to make use of muzzle brakes after I compete in rifle matches, and firing an enormous rifle with a muzzle brake in an enclosed area doesn’t sound nice – however it truthfully isn’t unhealthy. I believe the thought of the porthole by the “blast doorways” into the “enlargement chamber” was an enormous a part of that. Because of Scott Seigmund for that concept! The specialised acoustic blankets that soak up power additionally appear to actually assist.
I like the scale of the area and the way all the things got here collectively. Just about all the underground rifle ranges I’ve heard about have 2’ to 4’ diameter pipe, and the 8’ diameter pipe positive appears to be helpful. With that a lot area, I do know for positive that it isn’t affecting the bullet’s flight or including mirage results (extra on that within the authentic article).
I’m very glad that I opted for knowledgeable engineering firm to design the HVAC. That might have been a spot that I might’ve tousled if I hadn’t achieved that, so due to all my readers who chimed in on the primary put up and educated me.
I do assume making the first bullet entice out of ballistic rubber blocks would have been a mistake, however I’m glad somebody educated me earlier than I positioned the order. I just like the bullet entice I ended up with.
The one shock I can consider was how costly it was to get correct muzzle velocities within the tunnel. I knew it would find yourself being complicated, however I used to be hopeful I might nonetheless use a lower-priced gadget. Nevertheless, the professional-grade radar has plenty of superior options that I hope to get worth from sooner or later.
What experiments ought to I run?
Okay, in my first put up concerning the tunnel, I requested my readers for concepts on how I might make it higher. I’d nonetheless be up for listening to any concepts you guys may need. However right here is the place I’d actually like your assist:
Now that I’ve a very managed surroundings the place the wind by no means blows, and the mirage isn’t a difficulty, what experiments ought to I run? Please depart your concepts within the feedback!
I have already got a bunch of concepts I’d prefer to attempt as I get time, however I’m keen on listening to what concepts you guys have. I definitely can’t promise that I’ll do all of them, however I’d be very to take heed to all the concepts!
Extra Plans & Particulars
If you’re left questioning what I did on one thing particular, I wager it’s lined in my authentic article right here: https://precisionrifleblog.com/2021/12/27/100-yard-underground-range/
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