Today, June 20, 2024 is Summer Solstice, the longest day of the year. And right now the Northeast USA is undergoing a major heatwave. That means “peak heat” summer conditions have arrived already. It’s vitally important to keep your ammo at “normal” temps during the hot summer months. Even if you use “temp-insensitive” powders, studies suggest that pressures can still rise dramatically when the entire cartridge gets hot, possibly because of primer heating.
It’s smart to keep your loaded ammo in an insulated storage unit, possibly with a Blue Ice Cool Pak if you expect it to get quite hot. Don’t leave your ammo in the car or truck — temps can exceed 140° in a vehicle parked in the sun.
The way ambient temperatures, barrel heating, and powder warming can affect cartridge pressures (and hence velocities) was covered in a study Pressure Factors: How Temperature, Powder, and Primer Affect Pressure by Denton Bramwell. In that article, the author used a pressure trace instrument to analyze how temperature affects ammo performance. Bramwell’s tests yielded some fascinating results.
For example, barrel temperature was a key factor: “Both barrel temperature and powder temperature are important variables, and they are not the same variable. If you fail to take barrel temperature into account while doing pressure testing, your test results will be very significantly affected. The effect of barrel temperature is around 204 PSI per F° for the Varget load. If you’re not controlling barrel temperature, you about as well might not bother controlling powder temperature, either. In the cases investigated, barrel temperature is a much stronger variable than powder temperature.”
This Editor had the personal experience of 6mmBR hand-loaded ammo that was allowed to sit in the hot sun for 45 minutes while steel targets were reset. The brass became quite warm to the touch, meaning the casings were well over 120° on the outside. When I then shot this ammo, the bullets impacted well high at 600 yards (compared to earlier in the day). Using a Magnetospeed, I then chron-tested the sun-heated ammo. The hot ammo’s velocity FPS had increased very significantly — all because I had left the ammo out in the hot sun uncovered for 3/4 of an hour.
LESSON: Keep your ammo cool! Keep loaded ammo in the shade, preferably under cover or in an insulated container. You can use a SEALED cool pack inside the container, but we do NOT recommend H20 ice packs. And don’t have the container do double duty for food and beverages.
Powder Heat Sensitivity Comparison Test
Our friend Cal Zant of the Precision Rifle Blog has published a fascinating comparison test of four powders: Hodgdon H4350, Hodgdon Varget, IMR 4451, and IMR 4166. The first two are Hodgdon Extreme powders, while the latter two are part of IMR’s Enduron line of propellants.
The testers measured the velocity of the powders over a wide temperature range, from 25° F to 140° F. Hodgdon H4350 proved to be the most temp stable of the four powders tested. [NOTE: New Alliant Reloder TS 15.5 has also proved very temp stable in AccurateShooter’s range tests.]
Over the past 12 months, this article was one of the TOP 20 most-read Daily Bulletin features. We’re reprising it today for those who may have missed it the first time. The above diagram comes from a TiborasurasRex YouTube Video comparing G1 and G7 BC models. CLICK HERE to watch the video.
The better, up-to-date ballistics programs let you select either G1 or G7 Ballistic Coefficient (BC) values when calculating a trajectory. The ballistic coefficient (BC) of a body is a measure of its ability to overcome air resistance in flight. You’ve probably seen that G7 values are numerically lower than G1 values for the same bullet (typically). But that doesn’t mean you should select a G1 value simply because it is higher.
Some readers are not quite sure about the difference between G1 and G7 models. One forum member wrote us: “I went on the JBM Ballistics website to use the web-based Trajectory Calculator and when I got to the part that gives you a choice to choose between G1 and G7 BC, I was stumped. What determines how, or which one to use?”
The simple answer is the G1 value normally works better for shorter flat-based bullets, while the G7 value should work better for longer, boat-tailed bullets.
G1 vs. G7 Ballistic Coefficients — Which Is Right for You?
G1 and G7 refer both refer to aerodynamic drag models based on particular “standard projectile” shapes. The G1 shape looks like a flat-based bullet. The G7 shape is quite different, and better approximates the geometry of a modern long-range bullet. So, when choosing your drag model, G1 is preferable for flat-based bullets, while G7 is ordinarily a “better fit” for longer, boat-tailed bullets.
Drag Models — G7 is better than G1 for Long-Range Bullets
Many ballistics programs still offer only the default G1 drag model. Bryan Litz, author of Applied Ballistics for Long Range Shooting, believes the G7 standard is preferrable for long-range, low-drag bullets: “Part of the reason there is so much ‘slop’ in advertised BCs is because they’re referenced to the G1 standard which is very speed sensitive. The G7 standard is more appropriate for long range bullets. Here’s the results of my testing on two low-drag, long-range boat-tail bullets, so you can see how the G1 and G7 Ballistic coefficients compare:
G1 BCs, averaged between 1500 fps and 3000 fps:
Berger 180 VLD: 0.659 lb/in²
JLK 180: 0.645 lb/in²
The reason the BC for the JLK is less is mostly because the meplat was significantly larger on the particular lot that I tested (0.075″ vs 0.059″; see attached drawings).
For bullets like these, it’s much better to use the G7 standard. The following BCs are referenced to the G7 standard, and are constant for all speeds.
Many modern ballistics programs, including the free online JBM Ballistics Program, are able to use BCs referenced to G7 standards. When available, these BCs are more appropriate for long range bullets, according to Bryan.
[Editor’s NOTE: BCs are normally reported simply as an 0.XXX number. The lb/in² tag applies to all BCs, but is commonly left off for simplicity.]
This article is copyright 2023 AccurateShooter.com. No 3rd Party republication of this article is allowed without advance approval and payment of licensing fees.
Protect Your Hearing — Wear Protection Whenever You Shoot
Noise-induced hearing loss and tinnitus are two of the most common afflictions for recreational shooters and hunters. Everyone knows that gunfire is loud, but very few people understand the repercussions that shooting can have on their hearing until it’s too late.
The better quality suppressors can reduce the noise of a gunshot by 20 to 35 decibels (dB). Good muffs or plugs will reduce sound by 23 to 33 dB. By decreasing the overall sound signature, suppressors help to preserve the hearing of recreational shooters and hunters. Even the most effective suppressors, on the smallest and quietest calibers (.22 LR) reduce the peak sound level of a gunshot to between 110 to 120 dB. To put that in perspective, according to the National Institute for Occupational Safety and Health (NIOSH), that is as loud as a jackhammer (110 dB) or an ambulance siren (120 dB). For normal caliber handguns and rifles, suppressed sound levels routinely exceed 130 dB, just shy of OSHA’s “hearing safe” threshold of 140 dB.
According to Dr. William W. Clark, the current Director of the Washington Univ. School of Medicine’s Audiology/Communication Sciences Program, a “serious threat to hearing comes from recreational hunting or target shooting”. This is in large part due to the fact that many people choose not to use traditional hearing protection devices like earplugs and earmuffs because they want to be able to hear their surroundings. Multiple studies have found that between 70 to 80% of hunters never wear earplugs or earmuffs, and nearly half of all target shooters don’t consistently wear traditional hearing protection. Thus, it should come as no surprise that for every five years of hunting, hunters become seven percent more likely to experience high frequency hearing loss.
This article is based on information from the American Suppressor Association (ASA). Since the ASA’s formation in 2011, three additional states have legalized suppressor ownership and 18 states have legalized suppressor hunting. For more information, visit www.AmericanSuppressorAssociation.com.
Among AccurateShooter.com’s most-visited web pages have been powder burn rate reference guides ranking powders from fastest to slowest. Here is a new, updated version of the Powder Burn Rate Table. Compiled by Hodgdon Powder Co., this Burn Rate Chart displays the relative burn rates of 176 different powders. Shown below is the latest table, released by Hodgdon in July 2024.
You’ll want to download this Powder Burn Rate Chart PDF. This 176-entry comparison table provides vital information for hand-loaders — with tested burn-rates. Note — this invaluable chart is not limited to Hodgdon and IMR propellants. This burn rate chart includes powders from eight major powder-makers: Accurate, Alliant, Hodgdon, IMR, Norma, Ramshot (Western), Vihtavuori, and Winchester.
This chart (July 2024 version) provides useful information for all hand-loaders. When doing load development, and testing one powder versus another, it’s generally wise to choose propellants that share the same relative burn rate, as least for starters.
NOTE: Hodgdon powders are red, IMR powders are yellow, Winchester powders are blue, Accurate powders are gray, and Ramshot powders are orange. Powders from Alliant, Norma, and Vihtavuori appear on the chart with white background. DOWNLOAD Burn Rate Chart HERE as PDF.
Ace tactical shooter and gunsmith Jim See of Elite Accuracy LLC has tested a Frankford Arsenal rotary brass tumbler. Like the older Thumbler’s Tumblers, this can tumble your cases in a liquid solution. The wet-tumbling process worked very well Jim reports. Posting on Facebook, Jim noted: “I was super impressed with the Frankford Arsenal rotary tumbler and cleaning packs they sent me. I ran 350 pieces of brass for one hour. They now look great.” Jim appreciated not having to deal with dry tumbling media, such as crushed walnut shells. Dry media produces dust and can leave residues or clog flash-holes.
Interestingly, Jim recommends you try wet-tumbling WITHOUT using stainless media. At least give it a try. Tumbling without media simplifies the process and you don’t have to worry about pins stuck in flash-holes or case-necks*. Jim reports: “Stainless steel pins come with the Frankford kit, but mine hit the trash right out of the box. There is no need to clean the inside of your cases 100% and that’s all the pins add to the equation. The brass bumping brass with hot water and Frankford’s liquid cleaner works great all by itself.” One wag stated: “That’s great to hear. Stainless steel pins are a PITA.”
Other Facebook posters concurred with Jim’s evaluation of the Frankford Arsenal Rotary Tumbler:
“I’ve had one for a couple years, and it works well. I usually run about 250-300 Dasher cases at once in it. But I use the pins because I’m OCD about clean brass.” — David W.
“I’ve had one for a year and a half and it definitely works with or without pins.” — Luke C.
“I got one about six months ago and have yet to use any stainless steel media [pins]. I just use some dawn, distilled water, and Lemi Shine®. Turns nasty 5.56 range brass bright and shiny.” — Brian D.
“I don’t use the pins either and use a combination of Dawn soap and Lemi Shine.” — Jon N.G.
This video shows how to assemble and operate the Frankford rotary tumbler. But note, Jim See does NOT feel that it is necessary to use stainless media.
How to Dry Your Brass — Hair Dryer Vs. Machine
The downside of wet tumbling is that you end up with a pile of wet brass at the end of the cleaning cycle. There are many ways to dry brass, from drying in the sun to using a kitchen oven (be careful not to “overcook” your brass). One Facebook poster asked Jim: “What is your drying method for wet brass, and how long does it take?”
Jim See replied: “To start I just drain off the dirty water, and rinse the brass with clean hot water. Then I roll the brass on a towel for 30 seconds and put the brass in a one-gallon bucket. Next I insert a hair dryer in the bucket (with the brass) and let it run for about 5 minutes. With this procedure, the drying process for me is done in less than 10 minutes.”
Jack Lanhart has another method: “I use a food dehydrator. It takes 30 to 45 minutes.”
For those who don’t want to mess with towels and hair dryers, Frankford Arsenal offers a matching Platinum Series Case Dryer that simplifies the process of drying brass. Lyman also makes an excellent Cyclone Case Dryer. These drying machines each cost about $65.00 and both have multiple levels so you can separate different types of cartridge brass. Lyman states that “The forced heated air circulation of the Cyclone will dry your brass inside and out within an hour or two, with no unsightly water spots.” The Lyman dryer can also be used for ultrasonically-cleaned gun parts.
*The Frankford Rotary tumbler does include media separators if you choose to use the provided pins or other media. CLICK HERE for diagram showing how to use media separators.
Assembly Diagram: Here are all the components of the target frame. The overall maximum assembled dimensions are roughly 26″ wide, 41″ deep, and 66″ tall (the cardboard is 2 x 3 feet).
One of the easiest ways to build a portable target stand is to use PVC pipe and connectors. Utah .308 Shooter “Cheese” has created a simple yet sturdy target frame, and he’s shared his design so you can build a similar frame easily and at low cost. The components are wood furring strips, 2″-diameter PVC pipes (and connections), and a 2’x3′ sheet of cardboard. The PVC base can be glued together, or, for easier transport and storage, you can leave some or all of the connections free. “Cheese” tells us: “I didn’t glue any of it together so I could disassemble it, shove it in a bag and take it anywhere.”
“All the parts are just pushed together and not glued. That way I can break it down and carry it all in a bag. Also, if a buddy (not me!) happens to shoot the stand, I can easily replace just the damaged piece. The last 6 inches of the furring strips are wittled-down a bit so they can be pushed into the upright pipes with a little friction. The cardboard is 2 x 3 feet, and I use a staple gun to attach it to the furring strips. Then I just staple the target onto the cardboard and go at it.
Of course you can modify the dimensions as desired. I chose the black ABS pipe over white PVC simply for cost — black ABS is a little cheaper. You can also glue some or all of the parts together, it’ll just be larger for transporting. In windy conditions, the thing likes to come apart. Duct tape might work well.
For weight, I thought about filling the two end pipes with sand and gluing test caps on each of their ends. The test caps still allow the pipes to slip into the elbows.”
Add Anchors or Internal Weight for Stability
On a very windy day, a PVC stand can shake or even topple over. There are a couple solutions to this. Some people fill the PVC pipe sections with sand to add weight, or you can put short sections of Re-BAR inside the long legs. One GlockTalk forum member noted: “I built [a frame] almost identical to this. I also take four pieces of wire coathanger bent into an inverted “U” shape to anchor the frame to the ground. It is so light that wind will knock the stand over [without anchors].”
You can find photos of a similar home-made PVC target stand (with a slightly different rear section) on the Box of Truth website. This also employs a PVC tubing base with wood uprights. We’ve also seen all-PVC target stands, but we’ve found that it is easier to attach the cardboard to wood strips than to PVC pipe. Also, if the upper section is wood, you can fit different height targets, while using the same base.
Forum member F-Class John is an avid F-Class competitor and expert handloader. John reviews reloading hardware and shooting-related products for his popular F-Class John YouTube Channel, which now boasts 500+ videos. John also does important product testing for AccurateShooter.com. Through his YouTube channel, John has reviewed many of the latest and greatest reloading tools and accessories. For today’s Video Showcase, we selected eight F-Class John product reviews. Products tested include front rests, AMP Annealer, Flavio Fare triggers, AutoDod IDOD power neck-turner, Henderson and Giraud case trimmers, Zero turret press, 21st Century arbor press, and Accuracy One concentricity checker.
If you like these informative videos, consider joining F-Class John’s Patreon Channel for live video meetings, more in-depth videos, and detailed explanations. Join Patreon via Patreon.com/fclassjohn for full length videos, live chats, and more.
SEB NEO-X and Rodzilla Raptor Front Rests
This video covers two outstanding front joystick rests, the SEB Neo-X and the Rodzilla Raptor. Both of these rests work great for both benchrest and F-Class shooters, centerfire and rimfire. Build quality is outstanding for both rests. Tester F-Class John observes: “Both are great units and user preference will really dictate which to get. I own both and find they give me consistent target acquisition.” To learn more about these two excellent front rests, visit TheRodzilla.com and/or SEB Rests USA.
Flavio Fare Triggers Tested
The Flavio Fare triggers are some of the best on the market. These are offered for various action types including Remington clones and custom actions. CLICK HERE for a discussion of these triggers on our Forum. The Flavio Fare Veloce Hunting Trigger (with safety) adjusts from 5 to 25 ounces pull weight and retails for $439.95. The Flavio Fare Whisper 2.1 BenchRest Trigger (no safety) adjusts from 0.7 to 2.8 ounces, and costs $449.95. Reviewer F-Class John says these Flavio Fare triggers are “smooth, crisp, with a wide range of trigger pull weights … I love these things.”
Annealing Made Perfect AMP Mark II DB Annealer
This detailed 9.7 minute review outlines the features of the latest AMP electronic annealing machine, the AMP Mark II DB. This uses a computer control to deliver precise annealing times and temperatures with a profile for your specific lot and brand of brass. One user praised this new AMP machine: “The touch screen is much more intuitive than the old one.” Another stated: “If you want to anneal the best way possible this is it. Does a torch work? Sure it does. The AMP does it far better and far more consistently.” A buyer confirmed this sophisticated new AMP is fast and efficient: “Just got one, a few days ago and it’s so easy to use. Without even trying, I easily anneal eight rounds per minute”.
Bryan Blake, a very clever machinist and gunsmith, has created an ultra-precise and speedy neck-turning machine. Bryan, who runs Blake Machine, Blake Barrel, and F-Class Products has created a system that uses twin precision cutter tips to turn case necks inside and out quickly and efficiently, with superior precision. This advanced IDOD Neck Turning Machine holds cases securely in a precision-machined spindle attached to an electric motor. Twin blades move precisely during the cutting process, milling the necks inside and out. The turned necks come out perfect every time, with the shoulders trimmed exactly (with doughnut removed) as well.
Henderson vs. Giraud Case Powered Case Trimmers
After adding the impressive Henderson Gen 3 Powered Trimmer to his inventory of tools. F-Class John became is a Henderson fan. He likes the speed, precision, and repeatability of the $779.00 Henderson machine, which trims-to-length and chamfers the case mouth all in one pass. Unlike some other trimming tools, the Henderson indexes off the overall case length NOT the shoulder. The Giraud trimmer is a very different design which indexes off the case shoulder, but it is also very precise. When set up correctly, it can trim brass with amazing consistency. As long as you have fire-formed brass with consistent base-to-shoulder dimensions, you should get very consistent trim lengths.
Zero Turret Press with Whidden Sizing Die
The Zero Press from Area 419 is arguably the best turret press ever crafted. It offers unrivaled precision, along with the highest-capacity turret head with NINE die/tool stations. Milled from billet aluminum and stainless steel, this press moves with the help of 14 bearings. In this video, F-Class John shows how to use a Whidden Gunworks full-length sizing die on the Zero Press. And John has two other video reviews of the $1275 Zero Press: 1. Zero Press First Thoughts Video; 2. Loading on a Zero Press.
21st Century Hydro Press and Standard Arbor Press
John notes: “You can’t really talk about precision reloading without taking about inline dies and arbor presses. For my money there’s nothing better than the lineup from 21st Century Shooting. They offer the Hydro Seater which is hands-down the best manual seater out there as well as their standard arbor press which is great for taking on the road to push back bullets as needed.”
Concentricity Checking with Accuracy One Gauge
Every serious hand-loader needs a quality concentricity gauge. The Accuracy One Concentricity Gauge boasts a smart design that delivers precise, repeatable results. We like the unit’s easy adjustability and its ability to work in a variety of configurations. The Accuracy One Gauge measures internal and external neck runout of cartridge cases as well as seated bullet runout. It can also measure the runout of the ogive, bearing surface, and boat-tail of individual bullets. And it can even measure your primer pocket runout. Reviewer F-Class John notes: “I think this is the best concentricity tool on the market. Such a tool is a necessity for new loaders or those who are always setting up new dies.”
Yes, folks, it’s officially summer now. This year’s Solstice, considered the official start of summer, transpired Friday, June 20, at 7:42 PM PT. We hope you have fun this summer with friends and family. To help ensure those summer adventures remain safe and trouble-free, the CTD Shooters’ Log has prepared a helpful Essential Summer Survival Guide. This is worth reading before you venture away from civilization.
Here are some highlights of the article with links for MORE INFO:
First Aid Kits for Campers
You should never venture outside without a first aid kit close at hand. While exploring the outdoors, all types of accidents can occur—from cuts, scrapes, and burns to broken limbs and severe allergic reactions.
Basic Survival Skills
Basic survival skills are a necessity if you plan to spend any amount of time outdoors. These five tips, plus a how-to on what to pack in a lightweight, basic survival kit will help if you are ever stuck, lost, stranded or injured in the field.
How to Treat Burns
Fireworks, barbeques and campfires — in the summer we are frequently around fire, which increases our chance of getting burned. A first-degree burn is most likely home treatable, while a third degree burn requires immediate medical attention. Learn how to spot the differences between minor and severe burns.
Probably the most popular centerfire rifle round in the Western Hemisphere is the .223 Remington and its metric match, the 5.56x45mm. Though many folks use “.223 Rem” and “5.56×45″ interchangeably, there are some meaningful differences in specifications for the original .223 Rem and the 5.56x45mm cartridge, as adopted by the U.S. military and NATO armies. The default chamber throats are slightly different and the .223 Rem is rated at 55,000 PSI vs. 62,366 PSI for the 5.56x45mm.*
.223 Rem vs 5.56x45mm — Key Differences
There is a truly outstanding, very thorough article on the subject, published by LuckyGunner.com.** This involved extensive testing, with pressure monitors, of 5.56x45mm ammo in .223 Rem chambers. Those tests revealed the peak pressures. Here is one of the ammo test charts:
NOTE: “The observed chamber pressure for Federal XM855 5.56mm ammunition in a .223 Rem chamber exceeded .223 maximum pressures, but not by a massive amount. The ninth shot (the red line) was an underpowered cartridge which exhibited significantly lower velocity and pressure than the other rounds, so it was excluded from the average velocity and pressure numbers for this chamber.”
And if you’re curious, LuckyGunner also fired .223 Rem ammo in a 5.56x45mm NATO-chambered AR15 rifle. As you would expect, the peak pressures were significantly lower, but the .223 Rem ammo still cycled the semi-auto AR-platform rifle perfectly well:
UltimateReloader.com Explains .223 Rem vs. 5.56x45mm
To explain the key differences between the .223 Rem and 5.56x45mm cartridges our friend Gavin Gear of UltimateReloader.com has created a very thorough 12-minute video. This covers the cartridge specifications and explains key considerations for hand-loaders. Gavin also addresses the oft-asked question “Can I shoot 5.56x45mm ammo in my .223 Rem chamber?” Gavin’s video is definitely worth watching. In fact, this is one of the most popular videos Gavin has ever created — it has been watched nearly 4.5 million times on YouTube.
What Exactly Is the 5.56x45mm NATO Cartridge?
The 5.56×45mm NATO is a rimless bottle-necked intermediate cartridge family standardized by NATO with development work by FN Herstal. It consists of the SS109, SS110, and SS111 cartridges. Under STANAG 4172, it is a standard cartridge for NATO forces as well as many non-NATO countries.
Bullet diameter: 5.70 mm (0.224 in)
Maximum pressure (EPVAT): 430.00 MPa (62,366 psi)
Maximum pressure (SCATP 5.56): 380.00 MPa (55,114 psi)
Case length: 44.70 mm (1.760 in)
Rifling twist: 178 mm or 229 mm (1 in 7 in)
Parent case: .223 Remington (M193)
Ammo-Maker Federal Premium Compares .223 Rem and 5.56x45mm
Here is a video from ammo-maker Federal Premium explaining the difference between .223 Remington and 5.56x45mm NATO. Federal states that you may experience excessive pressures when firing a 5.56x45mm in a standard .223 Remington chamber:
One leading gunwriter has addressed the question of shooting 5.56x45mm ammo in .223 Rem chambers. He advocates caution (for more info, SEE pressure tests by LuckyGunner.com):
“I have received a slew of questions — many from first time AR-type rifle buyers — about the .223 Rem and the 5.56×45 mm NATO cartridges. Can I shoot 5.56×45 mm NATO in my .223 and vice-versa? Are these the same cartridge?
Externally, the two cartridge cases are identical. The main differences are that 5.56×45 mm NATO operates at a higher chamber pressure (about 60,000 PSI versus 55,000 PSI on the .223 Rem.) and the 5.56’s chamber is slightly larger than that of the .223 Rem. Also, the throat or leade is longer in the 5.56×45 mm chamber. What does this mean? You should not shoot 5.56×45 mm NATO out of a rifle that is chambered in .223 Rem [with a standard short throat]. And be aware that some .223 Rem ammunition will not reliably cycle through some AR-style .223 Rem rifles, but it usually does. As a matter of fact, I have not encountered any difficulty with current .223 Rem. loads cycling through a 5.56 mm AR-style rifle.” — Mark Keefe, Editor, American Rifleman
* According to the official NATO proofing guidelines, the 5.56×45mm NATO case can handle up to 430.0 MPa (62,366 psi) piezo service pressure. The U.S. SAAMI lists Maximum Average Pressure (MAP) for the .223 Remington cartridge as 55,000 psi (379.2 MPa) piezo pressure with deviation of up to 58,000 psi (399.9 MPa). The chamber for military 5.56×45mm NATO has a longer throat prior to the bullet contacting the rifling which results in lower pressures when firing 5.56×45mm NATO ammunition. If 5.56×45mm NATO is used in rifles chambered for .223 Remington the bullet will be engraving the rifling when chambered. which can increase pressures past SAAMI Max levels. NOTE: The C.I.P. standards for the C.I.P. civilian .223 Remington chamber are much closer to the military 5.56×45mm NATO chamber.
** The full-length LuckyGunner article is well worth reading. It even provides specifications for a number of .223 Rem reamer types, and compares the original .223 Rem, the 5.56x45mm NATO, and the modern .223 Wylde chamberings.
Readers often ask “What’s the difference between a Weaver scope rail and a Picatinny Rail?” The answer is not as simple as it seems. The dimensions of a Picatinny Rail should be consistent (from one rail-maker to another), since there IS a government spec. Conversely, there is some variance in “Weaver-style” rails. The width of the groove is the most important difference between Picatinny Rails and Weaver-type rails. “Mil-spec” Picatinny rails will have a grove width of 0.206″ while Weaver rails typically have a narrower, 0.180″ groove width.
Does your rifle have a Weaver Rail or Picatinny Rail? Check the dimensions to be sure.
A while back, Brownells had a helpful GunTech™ Article that discussed the Picatinny Rail vs. Weaver Rail. That article explained:
What are the differences between the ‘Picatinny’ and the ‘Weaver’ systems? The profile of the two systems is virtually identical. Depending on the quality of the machining done by the manufacturer, the two systems should be indistinguishable from the profile. The key difference lies in the placement of the recoil grooves and with width of the grooves. MIL-STD-1913 (Picatinny) grooves are .206″ wide and have a center-to-center width of .394”. The placement of these grooves has to be consistent in order for it to be a true Picatinny MIL-STD system. Weaver systems have a .180” width of recoil groove and are not necessarily consistent in a center-to-center measurement from one groove to the next.
In many instances, a Weaver system has a specific application that it is machined for, so interchangeability is not necessarily an issue. A MIL-STD-1913 system must adhere to the specifications listed above in order for it to be considered MIL-STD, since the military desires uniformity in the recoil grooves to allow for different systems to be mounted on the weapon with no concern for compatibility.
Now, what does this mean? Boiled down, it means that accessories designed for a Weaver system will, in most cases, fit on a Picatinny system. The reverse, however, is probably not the case. Due to the larger recoil groove, Picatinny accessories will not fit a Weaver system. There are, of course, exceptions to every rule, but for a good rule-of-thumb, [full-width] Picatinny won’t fit Weaver, but Weaver accessories WILL fit Picatinny.
The way ambient temperatures, barrel heating, and powder warming can affect cartridge pressures (and hence velocities) was covered in a study Pressure Factors: How Temperature, Powder, and Primer Affect Pressure by Denton Bramwell. In that article, the author used a pressure trace instrument to analyze how temperature affects ammo performance. Bramwell’s tests yielded some fascinating results.
The better, up-to-date ballistics programs let you select either G1 or G7 Ballistic Coefficient (BC) values when calculating a trajectory. The ballistic coefficient (BC) of a body is a measure of its ability to overcome air resistance in flight. You’ve probably seen that G7 values are numerically lower than G1 values for the same bullet (typically). But that doesn’t mean you should select a G1 value simply because it is higher.
Drag Models — G7 is better than G1 for Long-Range Bullets
One of the easiest ways to build a portable target stand is to use PVC pipe and connectors. Utah .308 Shooter “Cheese” has created a simple yet sturdy target frame, and he’s shared his design so you can build a similar frame easily and at low cost. The components are wood furring strips, 2″-diameter PVC pipes (and connections), and a 2’x3′ sheet of cardboard. The PVC base can be glued together, or, for easier transport and storage, you can leave some or all of the connections free. “Cheese” tells us: “I didn’t glue any of it together so I could disassemble it, shove it in a bag and take it anywhere.”
Yes, folks, it’s officially summer now. This year’s Solstice, considered the official start of summer, transpired Friday, June 20, at 7:42 PM PT. We hope you have fun this summer with friends and family. To help ensure those summer adventures remain safe and trouble-free, the CTD Shooters’ Log has prepared a helpful 
