Larry Medler has devised a smart little invention — a simple, inexpensive Empty Chamber Indicator for rimfire rifles. It is made from a section of plastic “weed-wacker” line and a wooden ball from a hobby shop. Larry says he was inspired by Juniors who used something similar for their 17-Caliber Air Rifles.
How to Make the Empty Chamber Indicator
Construction Method: First, drill a 7/64″ diameter hole all the way through the 1″-diameter wooden ball. Then enlarge half of that 1″-long hole using a 13/64” diameter drill. Next insert an 8″ piece of heavy duty (0.095″ diameter) weed wacker line through the ball, leaving about 2″ on the side with the bigger-diameter hole. Then, with the short end of the line, fold over the last half-inch so the line is doubled-over on itself. Then slide the line into the ball, stuffing the doubled-over section through the 13/64″ (large) hole. Finally, pull the longer end of the line until the doubled-over section is flush with the outside of the ball. This gives you a sturdy line attachment without messy adhesives. When the assembly’s complete, hold the ECI by the tail and dip the ball in yellow paint. If you’re making more than one ECI, you can drill horizontal holes in a spare block of wood and use that as a drying rack.
At a Rimfire Sporter match like this, all shooters must have an Empty Chamber Indicator.
The Empty Chamber Indicator for Smallbore Rifles
Larry explains: “At all Highpower rifle matches, silhouette matches, and other shooting events I have attended, Open Bore Indicators (OBI), or what are now called Empty Chamber Indicators (ECI) have been mandatory. The NRA’s yellow ECI for Highpower rifles is easy to use and has been well-received by the shooters. However, I had not seen a truly workable ECI for 22 rimfire rifles — until I visited Michigan’s Washtenaw Sportsman’s Club where I saw juniors using ECIs for their 17 Caliber Air Rifles. Someone at the club made the empty chamber indicators by attaching an 8″ piece of weed wacker line to a 1″-diameter wooden ball, painted bright yellow. I now make similar ECIs for the 22 rimfire silhouette matches I run.”
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In this article we cover a better barrel cooler you can build yourself for under $15. This uses a high-speed inflator fan sold on Amazon, along with a piece of temp-stable tubing. Forum member (and popular YouTube host) F-Class John devised this system. He found it cools his barrels in less than half the time of some other products. And the system can also serve as an Empty Chamber Indicator (ECI).
Barrel coolers perform an important function — reducing barrel operating temperatures. This can definitely help preserve barrel life and help maintain good accuracy in competition. In addition, keeping barrels cool can reduce the chances of excess chamber pressure, an important safety concern.
There are a variety of commercially-available barrel cooling systems. There are external fans, as well as internal, slip-in systems than can do double duty as an Empty Chamber Indicator (ECI). You can get the original yellow $39.99 BarrelCool or the red $59.99 RifleKuhl from Magnetospeeed. Both are good products. But F-Class John came up with a system that works even better — one you can build for a fraction of the cost of those yellow or red fans.
Build Your Own Barrel Cooler for Under $15
This system is easy to put together. Order a $11.99 YIVAR pump from Amazon. This is a small, high-output pump designed to inflate air mattresses. Then get some high-temp-rated tubing from a local supply shop. Then trim the case-head off an old piece of brass. Taper the end of the tube a bit and fit it in the case. NOTE: Use of the fitted case is optional. Having the case provides a nice fit in your chamber. But the system works pretty well just with the tubing and Yivar air pump.
In his .284 Win barrel, the Yivar pump system blows air at 10+ mph out the muzzle. F-Class John says that is “about three times the velocity of other systems”. The Yivar pump “holds about 45 minutes of charge” so he can use it for 15 minutes after each of three strings in a match. And then it can be recharged from a USB-compatible battery pack at the range. John notes the fan continues to blow about the same speed for the full 45-minute charge duration.
Key Benefits of this system
1. Faster Cooling
2. Low Cost (under $15)
3. Longer run time on battery
4. Fan battery is USB rechargeable
5. Finally a use for that worn-out brass
John confirmed the effectiveness of his barrel cooler using a stick-on temperature tape placed on the barrel. This showed that his fan system cooled the barreled in less than HALF the time as the plastic commercial fan systems. In addition, his run time was excellent, and the Yivar’s built-in Lithium-Ion battery is fully rechargeable so he never has to buy expensive batteries.
What are the downsides? Not many. The fan IS somewhat noisy — watch video at 4:04-4:28 time mark to hear the fan. F-Class John notes, however, that the Yivar fan is about 4 decibels (dB) quieter than a Magnetospeed RifleKuhl, so the Yivar’s noise is not that bad.
Here are comments from YouTube viewers who like F-Class John’s invention:
Finally something affordable! It’s compact and can be recharged at the range. I have room for this but not all the other gadgets you show. And a poor pensioner like my self can afford it! Thanks for the tip.
Ingenious and awesome idea! I bought one as soon as I saw this. I’ve been thinking about getting a cooler when I’m testing my loads. Thanks!
Brilliant… Brilliant… Brilliant! I have been deferring buying a barrel cooler for years now on account of wanting to spend my toy fund budget on other things. Considering how cheap it is to build, there is no excuse to not make one now.
Fan with Plain Hose Also Works Well (No Brass Case Cutting/Fitting Required)
F-Class John likes the custom fit he achieves with the hose inserted into a piece of modified brass. However he notes that the system also works well with no brass at all — i.e. just hose and fan. If you have a small diameter chamber, this may actually work better. Simply put the hose on the fan, trim/taper the forward hose end to fit and you are good to go.
F-Class John explains: “The heavy duty tubing and the motor works just fine without a brass case. The hose can sit in the chamber by itself. Obviously not every brass case will easily allow for you to put it on the end of the tube. For many people simply using the tube (without brass) may be the simpler option.”
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Here’s a new safety device that should prove useful for firearms, particularly pistols. The patented ShotBlock is a hi-viz orange foam chamber plug mated to an orange brush extension that goes in the barrel. This serves the same purpose as a Chamber Flag or Empty Chamber Indicator (ECI), but is more compact (and multi-purpose). With the Shot Block in place a round cannot be chambered. That should, with most firearms, render the gun safe, and unable to fire.*
Currently, the bright orange ShotBlock safety plugs are available for .380 ACP, 9mm Luger, .40 SW, and .223 Remington. Soon versions will be offered for .45 ACP and .308 Winchester as well. Watch the Video to see how this works:
The ShotBlock works by blocking the ability to chamber a round. The ShotBlock is attached to an “extended protection indicator” (i.e. an orange nylon brush). The plug and brush are placed into the barrel with the wide end of the plug on the breech lip. The extended protection indicator (orange brush) can be trimmed to fit the barrel length. Having the tip of brush visible at the end of the gun barrel confirms the Shot Block is in the chamber. As an added benefit, you can spray an anti-corrosion product on the brush for long-term storage.
The inventors state: “Once the ShotBlock is in the barrel of the gun you can easily manipulate the weapon safely, and any attempt to load the firearm will cause the bullet to be wedged inside the Shot Block, and prevent the [cartridge] from going inside the breach.”
Shot Block is Patented
The inventor of the ShotBlock, Bill Masters, has been awarded two U.S. Patents for this product: Nos. 9,448,024 and 9,310,149, both for “Firearm Safety and Chamber Block Indicator”. Bill explains why he invented the ShotBlock: “I had the idea for the ShotBlock after visiting a shooting range with my wife. The owner brought it out of the case and held it facing my wife without clearing it. He finally handed it to me and I cleared it. I left there telling myself there should be an easy way to let the customer know it was safe … to prevent someone quickly loading the weapon and doing bad things with it.”
Bill Masters is an engineer, inventor, designer, entrepreneur, and business advisor. He holds the first 3D printing patent, along with patents for other 3D printing technologies and CAD. He founded Perception Kayaks, which revolutionized the industry through by using molded plastics instead of fiberglass.
Alternative Product Available Soon from Chamber-View
Chamber-View will soon offer a chamber plug for pistols. Like the ShotBlock, Chamber-View’s Universal Empty Chamber Indicator (ECI) prevents a round from chambering. Unlike the ShotBlock, there is no barrel brush, but a large bright orange extension wing serves as an Empty Chamber Indicator:
* We are concerned however, that with some type of floating firing pins in semi-auto systems, it still might be possible to get a primer strike. This might happen if a round is stripped from the magazine and the firing pin moves forward from inertia as the pistol slide or bolt carrier moves forward rapidly and then stops. It’s unlikely a light strike could cause a round to fire, but check your firearm with dummy rounds before assuming it is 100% safe.
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Larry Medler has come up with a smart little invention — a simple, inexpensive Empty Chamber Indicator for rimfire rifles. It is made from a section of plastic “weed-wacker” line and a wooden ball from a hobby shop. Larry says he was inspired by Juniors who used something similar for their 17-Caliber Air Rifles.
At a Rimfire Sporter match like this, all shooters must have an Empty Chamber Indicator.
Construction Method: First, drill a 7/64″ diameter hole all the way through the 1″-diameter wooden ball. Then enlarge half of that 1″-long hole using a 13/64” diameter drill. Next insert an 8″ piece of heavy duty (0.095″ diameter) weed wacker line through the ball, leaving about 2″ on the side with the bigger-diameter hole. Then, with the short end of the line, fold over the last half-inch so the line is doubled-over on itself. Then slide the line into the ball, stuffing the doubled-over section through the 13/64″ (large) hole. Finally, pull the longer end of the line until the doubled-over section is flush with the outside of the ball. This gives you a sturdy line attachment without messy adhesives. When the assembly’s complete, hold the ECI by the tail and dip the ball in yellow paint. If you’re making more than one ECI, you can drill horizontal holes in a spare block of wood and use that as a drying rack.
The Empty Chamber Indicator for Smallbore Rifles
Larry explains: “At all Highpower rifle matches, silhouette matches, and other shooting events I have attended, Open Bore Indicators (OBI), or what are now called Empty Chamber Indicators (ECI) have been mandatory. The NRA’s yellow ECI for Highpower rifles is easy to use and has been well-received by the shooters. However, I had not seen a truly workable ECI for 22 rimfire rifles — until I visited Michigan’s Washtenaw Sportsman’s Club where I saw juniors using ECIs for their 17 Caliber Air Rifles. Someone at the club made the empty chamber indicators by attaching an 8″ piece of weed wacker line to a 1″-diameter wooden ball, painted bright yellow. I now make similar ECIs for the 22 rimfire silhouette matches I run.”
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Our buddy Eric Kennard of Harbour Arms is offering a “Christmas in July” special on his high-quality metal SnapCaps. These are precision machined aluminum SnapCaps with internal springs. Now, through the end of July, you can purchase two sets of SnapCaps (two units per set), along with two Empty Chamber Indicators (ECIs) — all for just $23.95. Eric offers SnapCaps in a wide variety of calibers including .308 Winchester, 6 PPC, 6mmBR, 6BRX, 6mm Dasher, 6XC, .243 Win, 6.5 Creedmoor, 6.5×47, .260 Rem, 6.5-284 and dozens more.
With Eric’s SnapCaps, you can dry-fire to your hearts content without harming your gun’s firing pin or fire control system. Veteran high-power shooters know the importance of dry-fire practice — one former National Champion told us he would dry-fire at least six hours for every hour he spent on the firing line. Even benchrest shooters can benefit. By using Eric’s SnapCaps, you can improve your gun-handling and trigger-pulling techniques. This Editor found his rimfire benchrest scores improved after dry-fire practice. I learned to pull the trigger straight back and I learned the hold that produced the minimal disturbance on the bags.
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Key Benefits of this system
Our buddy Eric Kennard of 
