I recently bought an AR15 Ruger 556. And I know I can shoot 5.56 NATO. But...I see ammo that says 5.56x45...... Is the 5.56x45 safe to shoot in my AR15? What's the difference between the two bullets? I don't wanna buy the 5.56x45 and it messes up my rifle.
qtrojas1
- Status
You and your new rifle are good to go with 5.56 x 45 mm ammo.
5.56 x 45 mm is another name for 5.56 NATO.
Welcome to the forum. There are lots of folks with good info hanging out here.
Be sure to check out the various forums (New Users is just one of many).
Asking a question under the correct heading / forum gets a lot more folk's attention. And gives you a better chance to get an answer.
5.56 x 45 mm is another name for 5.56 NATO.
Welcome to the forum. There are lots of folks with good info hanging out here.
Be sure to check out the various forums (New Users is just one of many).
Asking a question under the correct heading / forum gets a lot more folk's attention. And gives you a better chance to get an answer.
The 5.56x45 denotes a whole family of cartridges with identical case dimensions. Strictly speaking, only a few 5.56x45 cartridges have been adopted for use by NATO.
The standard full metal jacket 5.56x45 NATO cartridge is the SS109 penetrator or "green tip" which is loaded with a 62 grain bimetallic projectile with a steel core at the tip and a lead core at the base. The US Army designates the same cartridge the M855.
There are a huge variety of other 5.56x45 cartridges with various projectile types and weights which are not used by NATO, but it is not uncommon for all 5.56x45 cartridges to have the "NATO" moniker applied. A very common example is the US Army M193 designated cartridge with a 55 grain projectile, which was the original projectile weight around which the M16 rifle was developed. The M193 round was actually rejected by NATO because its tendency to fragment was considered to be "inhumane". There are other 5.56x45 cartridges used by the US military that have not been adapted by NATO such as the MK262 which has a 77 grain "match" projectile.
It is my understanding that the outer case dimensions of the .223 Remington and 5.56x45 cartridges are identical. At one time, the 5.56 cartridge case was a bit thicker near the case head than that of the .223 Rem so that the interior volume was a bit less, so that a given powder charge in a 5.56x45 case would develop a bit higher maximum pressure than the identical charge would in a .223 Rem case. I don't know if this is still the case, and if it is whether the difference applies to all 5.56 and .223 Rem cases.
The chamber dimensions for the 5.56x45 and .223 Rem barrels are distinctly different. This came about because of the need for the US Armed Forces and NATO to be able to use tracer rounds which required a longer, thicker projectile. With these tracer projectiles the ogive (the point at which the projectile became thick enough to contact the rifling in the barrel) was farther forward away from the case head. Use of these required chambering with a longer leade or freebore that had a less steep angle. The .223 Rem chamber has a shorter leade with a steeper angle. This means that the 5.56x45 chamber has a bit more overall volume.
The problem with using some 5.56x45 cartridges in a barrel chambered for .223 Rem is that some heavier, longer projectiles may have an ogive that contacts the rifling before the cartridge is fully chambered which can cause a bit of projectile set back into the case resulting in over-pressure. The other issue is that since the .223 Rem chamber has a bit less volume, for any given powder load chamber pressure will be a bit higher. With some 5.56x45 loads that have acceptable maximum case pressures in a 5.56 chamber, the case pressure in a .223 Rem chamber might be somewhat over maximum pressure limits.
If you want to read about a wide variety of 5.56x45 cartridges used by the US military and other military services around the world, a few of which are used by NATO, you might find this interesting, or perhaps tedious:
http://ammunitionstore.com/content/5.56Ă—45mm NATO.pdf
The standard full metal jacket 5.56x45 NATO cartridge is the SS109 penetrator or "green tip" which is loaded with a 62 grain bimetallic projectile with a steel core at the tip and a lead core at the base. The US Army designates the same cartridge the M855.
There are a huge variety of other 5.56x45 cartridges with various projectile types and weights which are not used by NATO, but it is not uncommon for all 5.56x45 cartridges to have the "NATO" moniker applied. A very common example is the US Army M193 designated cartridge with a 55 grain projectile, which was the original projectile weight around which the M16 rifle was developed. The M193 round was actually rejected by NATO because its tendency to fragment was considered to be "inhumane". There are other 5.56x45 cartridges used by the US military that have not been adapted by NATO such as the MK262 which has a 77 grain "match" projectile.
It is my understanding that the outer case dimensions of the .223 Remington and 5.56x45 cartridges are identical. At one time, the 5.56 cartridge case was a bit thicker near the case head than that of the .223 Rem so that the interior volume was a bit less, so that a given powder charge in a 5.56x45 case would develop a bit higher maximum pressure than the identical charge would in a .223 Rem case. I don't know if this is still the case, and if it is whether the difference applies to all 5.56 and .223 Rem cases.
The chamber dimensions for the 5.56x45 and .223 Rem barrels are distinctly different. This came about because of the need for the US Armed Forces and NATO to be able to use tracer rounds which required a longer, thicker projectile. With these tracer projectiles the ogive (the point at which the projectile became thick enough to contact the rifling in the barrel) was farther forward away from the case head. Use of these required chambering with a longer leade or freebore that had a less steep angle. The .223 Rem chamber has a shorter leade with a steeper angle. This means that the 5.56x45 chamber has a bit more overall volume.
The problem with using some 5.56x45 cartridges in a barrel chambered for .223 Rem is that some heavier, longer projectiles may have an ogive that contacts the rifling before the cartridge is fully chambered which can cause a bit of projectile set back into the case resulting in over-pressure. The other issue is that since the .223 Rem chamber has a bit less volume, for any given powder load chamber pressure will be a bit higher. With some 5.56x45 loads that have acceptable maximum case pressures in a 5.56 chamber, the case pressure in a .223 Rem chamber might be somewhat over maximum pressure limits.
If you want to read about a wide variety of 5.56x45 cartridges used by the US military and other military services around the world, a few of which are used by NATO, you might find this interesting, or perhaps tedious:
http://ammunitionstore.com/content/5.56Ă—45mm NATO.pdf
There are way too many rumors and misinformation being spread around the Internet about this topic. As an example, in pblanc's post
While external 5.56 NATO and 5.56x45 case dimesions are the same as a 223 Rem, internally they can vary from manufacturer to manufacturer, just like 223 Rems so there is really no NATO, military, or SAAMI specification for internal dimensions. There are specifications for chamber pressure and because SAAMI and EPVAT (military standard) are measured differently, they appear to have different pressure standards when indeed they would be about the same if cartridges were tested with the same method.
I posted an article in the Forum Library titled "223 Rem / 5.56 NATO ammo and Chambers" It has all the information about compatibility and even dimensions for both. Here's a link for members with 10 or more posts: https://rugerforum.net/librar/135584-223-rem-5-56-nato-ammo-chambers.html
All 5.56x45 cartridges with the NATO headstamp (a two digit year code, the code for the armory that made them, and a symbol that looks like a view through a scope (plus sign inside a circle) have been approved for NATO use. Example: LC 07 with a plus sign inside a circle indicates the manufacture was Lake City Army Ammunition Plant in Independence, Missouri, and the cartridge was loaded to NATO specs in 2007. Many of the NATO nations produce 5.56 NATO ammo and it is supposed to be loaded to the same specs no matter where the ammo was made. 5,56x45 is the military designation that was used before 5.56 NATO and is still used today. It resembles a 5.56 NATO headstamp except it does not have the plus sign inside a circle and can be made by a variety of domestic and foreign manufacturers.
While external 5.56 NATO and 5.56x45 case dimesions are the same as a 223 Rem, internally they can vary from manufacturer to manufacturer, just like 223 Rems so there is really no NATO, military, or SAAMI specification for internal dimensions. There are specifications for chamber pressure and because SAAMI and EPVAT (military standard) are measured differently, they appear to have different pressure standards when indeed they would be about the same if cartridges were tested with the same method.
I posted an article in the Forum Library titled "223 Rem / 5.56 NATO ammo and Chambers" It has all the information about compatibility and even dimensions for both. Here's a link for members with 10 or more posts: https://rugerforum.net/librar/135584-223-rem-5-56-nato-ammo-chambers.html
I have and H&R heavy barrel single shot that has a hang tag stating to shoot .223 only not the 5.56 NATO.
JohnnyDollar, Not true. Please read the article in this link: 223 Rem / 5.56 NATO Ammo and chambers
Everyone read Iowegan's link. It's not that hard. Toooooooo many internet BS posts about this subject.
And to further muddy the water there's the recommended twist rates:
www.gunsandammo.com
You can find twist rate vs. bullet weight charts and info all over but I figured this source most would find trustworthy.
I am 90% done building a new AR15 with 18" barrel with 1:7 twist and see how it handles 62 and higher grain bullets vs. my 1:9 16" AR.
Pairing Barrel Twist Rates with Bullet Weights for .223 and 5.56 NATO - Guns and Ammo
A guide on how to pair .223 and 5.56 NATO rifle barrel twist rates with bullet weights. Conventional wisdom says slower twist rates wouldn't properly stabilize a heavy bullet. On the other hand, faster rates could over-stabilize lighter bullets. This is correct in theory, however, modern ballist
www.gunsandammo.com
You can find twist rate vs. bullet weight charts and info all over but I figured this source most would find trustworthy.
I am 90% done building a new AR15 with 18" barrel with 1:7 twist and see how it handles 62 and higher grain bullets vs. my 1:9 16" AR.
Geo001, "over stabilization" is like saying something is 110% good, which is not possible. It's just not the right term but it is used by many people in the shooting industry. Here's what happens when a bullet is spun by the rifling ..... it leaves the muzzle with two different forces. The first is bullet spin rate, based on the bore's twist rate and the bullet's exit velocity. Shorter barrels don't develop as much velocity so the twist rate has to be a little faster to keep the bullet stabilized downrange. The formula for bullet spin in RPM is: 12 divided by twist rate, times velocity in fps, times 60. As an example: a bullet exiting the muzzle at 3000 fps in a bore with a 1:8 twist rate ...... 12/8=1.5*3000= 4500*60=270,000 RPM bullet spin rate.
The second effect is centrifugal force. It is based on the length of the bullet versus the bullet's diameter and spin rate where the longer the bullet, the larger the diameter of the spiral will be. What happens is the bullet will immediately go into a spiral once it leaves the muzzle. If you could see the bullet path from behind the shooter, the spiral gets smaller and smaller as the bullet travels down range and looks much like a corkscrew. At some point, centrifugal force will dissipate, leaving only the bullet's remaining velocity, spin rate, air friction, and gravity to determine trajectory. Long range shooters call this point of centrifugal force dissipation "going to sleep". Mean time, at distances between the muzzle and the point of going to sleep, the bullet's spiral path will spread the groups but as the bullet travels past the sleep point, the group will actually tighten. So, short range accuracy suffers from centrifugal force ( AKA over stabilization) especially with longer (usually heavier) bullets but longer range accuracy will recover.
So what's missing from the reference you quoted is the bullet's velocity as affected by barrel length .224" bullets are pretty short so they don't develop a large spiral, which in turn dissipates at distances under 100 yards. Long bullets like a .270 can develop a 3" spiral and can take at least 200 yards for the spiral to dissipate. This spiral effect often spoofs shooters, making them think their rifles are not accurate when indeed it means the bullet has not yet gone to sleep. As an example, when I had a 6.5x55 Swede rifle, my best groups at 100 yards were about 2", however at 200 yards, groups were under an inch. This is opposite of what you would expect, all because of centrifugal force.
The second effect is centrifugal force. It is based on the length of the bullet versus the bullet's diameter and spin rate where the longer the bullet, the larger the diameter of the spiral will be. What happens is the bullet will immediately go into a spiral once it leaves the muzzle. If you could see the bullet path from behind the shooter, the spiral gets smaller and smaller as the bullet travels down range and looks much like a corkscrew. At some point, centrifugal force will dissipate, leaving only the bullet's remaining velocity, spin rate, air friction, and gravity to determine trajectory. Long range shooters call this point of centrifugal force dissipation "going to sleep". Mean time, at distances between the muzzle and the point of going to sleep, the bullet's spiral path will spread the groups but as the bullet travels past the sleep point, the group will actually tighten. So, short range accuracy suffers from centrifugal force ( AKA over stabilization) especially with longer (usually heavier) bullets but longer range accuracy will recover.
So what's missing from the reference you quoted is the bullet's velocity as affected by barrel length .224" bullets are pretty short so they don't develop a large spiral, which in turn dissipates at distances under 100 yards. Long bullets like a .270 can develop a 3" spiral and can take at least 200 yards for the spiral to dissipate. This spiral effect often spoofs shooters, making them think their rifles are not accurate when indeed it means the bullet has not yet gone to sleep. As an example, when I had a 6.5x55 Swede rifle, my best groups at 100 yards were about 2", however at 200 yards, groups were under an inch. This is opposite of what you would expect, all because of centrifugal force.
When a football is thrown (good spiral), the spin axis follows the trajectory, or path, of the football itself. In other words, nose up when thrown and nose down when caught if it’s a long throw. This would seem to be most efficient, as the point leads the direction of travel. So, does a bullet’s spin axis follow it’s parabolic trajectory, or does it remain nose up due to the more extreme gyroscopic effect (which would hinder it’s aerodynamics). To my point… does “over spinning” a bullet vs. the ideal spin rate affect it’s spin axis during the course of it’s flight?
Also, I read somewhere that if a bullet has inconsistent construction/jacket thickness, that the faster it’s spun (above what’s needed for stabilization) the more it disrupts it’s flight.
Also, I read somewhere that if a bullet has inconsistent construction/jacket thickness, that the faster it’s spun (above what’s needed for stabilization) the more it disrupts it’s flight.
Colt Carson,
As bullets travel down range, air friction causes their spin rate to decay, much like the bullet's velocity and almost proportional. This means if the bullet's velocity drops by 50%, spin rate will also drop by a similar rate. As long as the bullet's spin rate is faster than it's point of gyro stability, imperfections will be overcome and the bullet will fly true. Once the spin rate drops, any imperfection in the bullet that affects balance (such as non-uniform jacket thickness) will cause the bullet to start to yaw. Soon after, the bullet will begin to tumble and lose all semblance of accuracy. So .... it's almost the opposite of what you stated about inconsistencies in bullet balance because they require a higher spin rate to maintain stability. It is very common for an inconsistent bullet to lose stability downrange much sooner than a "perfect" bullet. Because an excessive spin rate causes a larger diameter spiral to develop, I suspect (but do not know for sure) that inconsistencies in bullets will cause an even larger diameter spiral???
Back when the 5.56x45mm was being developed by Remington, 55gr FMJ bullets that were used in M-193 cartridges fell below the point of gyro stability at about 250 yards with the original 1:12 twist rate 20" barrel (3100 fps). Coincidentally, 250 yards also happened to be where the bullet's velocity went subsonic so this is where the subsonic theory was born. As it turned out, the same M-193 cartridge was used with rifles that had a 1:10 twist rate and chronographed the same 3100 fps as a 1:12 twist rate barrel. The bullets launched from 1:10 twist rate barrels maintained gyro stability to well past 350 yards so that blew the "sonic transition theory", however to this day, many people still believe it. The fact is .... the 55gr FMJ bullets have a low ballistic coefficient so they don't deal well with air friction. The newer 62gr bullets used in 5.56 NATO cartridges have a much better ballistic coefficient combined with a faster twist rate barrel so they maintain gyro stability to at least 500 yards.
Using high speed photography, it was discovered rifle bullets tend to maintain the same attitude angle as when they exit the muzzle. Why? Bullets are spun very fast so they develop a huge gyroscopic force. Anything that disrupts that force will cause the bullet to lose stability and begin to yaw. This could be an inconsistency in the bullet itself, a gust of wind, or the bullet striking a twig or a blade of grass. Yaw means the bullet's nose is pointed somewhere other than straight forward.
As bullets travel down range, air friction causes their spin rate to decay, much like the bullet's velocity and almost proportional. This means if the bullet's velocity drops by 50%, spin rate will also drop by a similar rate. As long as the bullet's spin rate is faster than it's point of gyro stability, imperfections will be overcome and the bullet will fly true. Once the spin rate drops, any imperfection in the bullet that affects balance (such as non-uniform jacket thickness) will cause the bullet to start to yaw. Soon after, the bullet will begin to tumble and lose all semblance of accuracy. So .... it's almost the opposite of what you stated about inconsistencies in bullet balance because they require a higher spin rate to maintain stability. It is very common for an inconsistent bullet to lose stability downrange much sooner than a "perfect" bullet. Because an excessive spin rate causes a larger diameter spiral to develop, I suspect (but do not know for sure) that inconsistencies in bullets will cause an even larger diameter spiral???
Back when the 5.56x45mm was being developed by Remington, 55gr FMJ bullets that were used in M-193 cartridges fell below the point of gyro stability at about 250 yards with the original 1:12 twist rate 20" barrel (3100 fps). Coincidentally, 250 yards also happened to be where the bullet's velocity went subsonic so this is where the subsonic theory was born. As it turned out, the same M-193 cartridge was used with rifles that had a 1:10 twist rate and chronographed the same 3100 fps as a 1:12 twist rate barrel. The bullets launched from 1:10 twist rate barrels maintained gyro stability to well past 350 yards so that blew the "sonic transition theory", however to this day, many people still believe it. The fact is .... the 55gr FMJ bullets have a low ballistic coefficient so they don't deal well with air friction. The newer 62gr bullets used in 5.56 NATO cartridges have a much better ballistic coefficient combined with a faster twist rate barrel so they maintain gyro stability to at least 500 yards.
C.Carson, The speed of sound is about 1155 fps at sea level with 30% humidity. As elevation increases, the speed of sound decreases.
As you probably know, the bullet's ballistic coefficient makes a huge difference on air friction and retained velocity. The 55 gr FMJ used in M-193 ammo has a grim B/C .... about .101 so it transitions through the sound barrier at 250~320 yards, depending on barrel length. 62gr M-855 bullets have a much higher B/C so they will stay supersonic until about 550~700 yards, again depending on barrel length. This data was derived from Oehler's Ballistic Explorer.
As you probably know, the bullet's ballistic coefficient makes a huge difference on air friction and retained velocity. The 55 gr FMJ used in M-193 ammo has a grim B/C .... about .101 so it transitions through the sound barrier at 250~320 yards, depending on barrel length. 62gr M-855 bullets have a much higher B/C so they will stay supersonic until about 550~700 yards, again depending on barrel length. This data was derived from Oehler's Ballistic Explorer.
The issue is .... Milspec M193 ammo doesn't use Hornady or Winchester bullets ..... GI bullets have the aerodynamics of a brick. I have chronographed M-193s many times and found they were hard pressed to stay supersonic at 250 yards from a 20" AR-15 barrel.
BTW, the B/C ratings for bullets is not what you might think because they are B/C tested without any rifling marks. I don't view it as "dishonest" because bullet manufacturers have no idea what rifle you will use. Rifling grooves on bullets act like an impeller that increases air friction and slows bullets down, almost like shooting a fan blade.
I use the procedure outlined in Ballistic Explorer to determine actual B/C in my own guns. Chronograph a 10 shot string of ammo at 4 yards then repeat at 100 yards. Plug the average velocities from these two distances into Ballistic Explorer and it will tell you exactly what your B/C is. Once you determine the actual B/C, the charts generated by Ballistic Explorer are dead nuts accurate. These charts include: Bullet path, bullet drop, retained velocity, wind drift, and a few more. BTW, I've never seen a bullet's actual, B/C come close to the factory published B/C.
If your rifle's accuracy is good enough, you can chronograph at 250 yards and see for yourself what the retained velocity is, however this method has the potential to ruin sky screens. Ask me how I know.
BTW, the B/C ratings for bullets is not what you might think because they are B/C tested without any rifling marks. I don't view it as "dishonest" because bullet manufacturers have no idea what rifle you will use. Rifling grooves on bullets act like an impeller that increases air friction and slows bullets down, almost like shooting a fan blade.
I use the procedure outlined in Ballistic Explorer to determine actual B/C in my own guns. Chronograph a 10 shot string of ammo at 4 yards then repeat at 100 yards. Plug the average velocities from these two distances into Ballistic Explorer and it will tell you exactly what your B/C is. Once you determine the actual B/C, the charts generated by Ballistic Explorer are dead nuts accurate. These charts include: Bullet path, bullet drop, retained velocity, wind drift, and a few more. BTW, I've never seen a bullet's actual, B/C come close to the factory published B/C.
If your rifle's accuracy is good enough, you can chronograph at 250 yards and see for yourself what the retained velocity is, however this method has the potential to ruin sky screens. Ask me how I know.
Also, I have a bunch of the ballistic tip cartridges that they say melts away after a few hundred yards, so who knows what your BC is after that. I believe it was Hornady who came up with that, and then revised the plastic formula in their ballistic tips to keep the tip intact and preserve the BC.
Mark204, I wonder how those manufacturers deal with their bullets being fired from different rifles? As you know, not all rifles in the same caliber have the same twist rate nor is the rifling the same depth in all guns. Further, many different cartridges use the same diameter bullets, which are launched at different velocities. Rifling engraving on the bullet has a very significant influence on its ballistic coefficient because it works like an impeller and increases air friction. The deeper the engraving and the faster the twist rate, the more it lowers its ballistic coefficient. Depending on the bullet's intended use, there are multiple ballistic coefficients for rifle bullets. Handgun bullet's are BC tested at 1000 fps, which is accurate enough to get reasonable statistics at handgun shooting distances. Rifle bullets have multiple BCs depending on both muzzle velocity and the distance downrange. As an example, a .224" bullet fired from a 223 Rem @ 3240 fps will perform quite differently in the first 100 yards (lower BC) and as velocity decays down range, that same bullet will have a higher BC. If you shoot the same bullet from a 22-250 @ 4000 fps, it will have a notably lower BC at all distances.
If bullet manufacturers use an actual rifle and no sabot for BC tests, the bullet will have a lower and more truthful BC but it still won't be accurate for every possible gun at all possible shooting distances or velocities.
So, the end result is an approximate factory ballistic coefficient. Point being, published factory ballistic coefficients are always higher than actual BCs. As I noted previously, I use the features in Ballistic Explorer to find the true BC and it is always notably lower than the manufacturer's published BC. How do I know Ballistic Explorer is accurate? Because the charts developed in the software track exceptionally close to actual groups fired in a real rifle. If you use the factory BC, the charts will not track well for bullet path or any of the other parameters.
Here's an accurate example: A few years ago, I did tests on Hornady 60gr V-Max bullets that had a published factory BC of .265. I started with an AR-15 using a 1:9 twist rate. My 100 yard test chronographed a 10 shot string at 6 yards and another 10 shot string at 100 yards, then I plugged the average velocities into Ballistic Explorer, which indicated an actual BC of .220. This was very notably lower than published specs. I chronographed another 10 shot string at 250 yards and came up with a BC of .242 . This meant the BC actually improved as velocity decayed from air friction. I also tested the same bullets in my Remington 700 bolt gun with a 24" barrel and a 1:12 twist rate, which shot about 90 fps faster than the 20" AR-15. The 100 yard BC was .232 ...... higher than with the AR-15's 1:9 twist rate but still much lower than advertised by the manufacture. I did not do a 250 yard test with my 700 because it grouped poorly at 250 yards with these 60gr bullets and I was afraid I would hit my chronograph's sky screen. That said, my tests with .224" Hornady V-Max 55gr bullets grouped exceptionally well at 250 yards and tracked just about perfect with the 250 yard charts I printed from Ballistic Explorer. This bullet has an advertised BC of .235 and an actual BC of .203 at 100 yards and .222 at 250 yards (only in my Rem 700). BTW, Ballistic Explorer can accommodate up to 5 different BCs at different velocities.
Very Low Drag (VLD) bullets are typically tested with at least three and as many as 5 different BCs .... one at 100 yards, one at 250 yards, one at 500 yards, another at 750 yards and finally one at 1000 yards. The longer shooting distances will test with higher BCs. This means air friction on a bullet is not proportional at different velocities .... always favoring lower velocities. This is why different drag tables are used .... G1 for normal sporting bullets and G5 for VLD bullets.
If bullet manufacturers use an actual rifle and no sabot for BC tests, the bullet will have a lower and more truthful BC but it still won't be accurate for every possible gun at all possible shooting distances or velocities.
So, the end result is an approximate factory ballistic coefficient. Point being, published factory ballistic coefficients are always higher than actual BCs. As I noted previously, I use the features in Ballistic Explorer to find the true BC and it is always notably lower than the manufacturer's published BC. How do I know Ballistic Explorer is accurate? Because the charts developed in the software track exceptionally close to actual groups fired in a real rifle. If you use the factory BC, the charts will not track well for bullet path or any of the other parameters.
Here's an accurate example: A few years ago, I did tests on Hornady 60gr V-Max bullets that had a published factory BC of .265. I started with an AR-15 using a 1:9 twist rate. My 100 yard test chronographed a 10 shot string at 6 yards and another 10 shot string at 100 yards, then I plugged the average velocities into Ballistic Explorer, which indicated an actual BC of .220. This was very notably lower than published specs. I chronographed another 10 shot string at 250 yards and came up with a BC of .242 . This meant the BC actually improved as velocity decayed from air friction. I also tested the same bullets in my Remington 700 bolt gun with a 24" barrel and a 1:12 twist rate, which shot about 90 fps faster than the 20" AR-15. The 100 yard BC was .232 ...... higher than with the AR-15's 1:9 twist rate but still much lower than advertised by the manufacture. I did not do a 250 yard test with my 700 because it grouped poorly at 250 yards with these 60gr bullets and I was afraid I would hit my chronograph's sky screen. That said, my tests with .224" Hornady V-Max 55gr bullets grouped exceptionally well at 250 yards and tracked just about perfect with the 250 yard charts I printed from Ballistic Explorer. This bullet has an advertised BC of .235 and an actual BC of .203 at 100 yards and .222 at 250 yards (only in my Rem 700). BTW, Ballistic Explorer can accommodate up to 5 different BCs at different velocities.
Very Low Drag (VLD) bullets are typically tested with at least three and as many as 5 different BCs .... one at 100 yards, one at 250 yards, one at 500 yards, another at 750 yards and finally one at 1000 yards. The longer shooting distances will test with higher BCs. This means air friction on a bullet is not proportional at different velocities .... always favoring lower velocities. This is why different drag tables are used .... G1 for normal sporting bullets and G5 for VLD bullets.
Iowegan, I agree with with you’re saying, but I don’t believe that the engraving on the bullet is as big an issue as you state. I do think it will have more effect on a bullet as it enters the transonic zone. If it was a big factor there'd be more discussions about it but I don’t see it.
Did you purposely cite G5 or did you mean G7? The G5 drag model wouldn’t be the best choice for VLD’s, G7 on the other hand would.
Did you purposely cite G5 or did you mean G7? The G5 drag model wouldn’t be the best choice for VLD’s, G7 on the other hand would.
With a muzzle velocity of 3000 fps and sound at 1000 fps, my math says the bullet arrives before the sound at 500 yards. I think the bullets trajectory would deteriorate to ground level before the sound arrives as well, given a level target.
This may be flawed thinking, but I look at the BC numbers of bullets like tread wear rating numbers on tires. I don’t care so much what the actual number is, but use it to compare one bullet to another. I will say when I sighted in an AR15, I plugged the published BC number into my very simple ballistic calculator app and got pretty good results. Using the app, I sighted in at 50 yards. Then at 200 yards, only had to make some minor adjustments to the scope to be center of paper target. Then held over the suggested amount, and was getting hits on steel at 300 yards. I do enjoy learning all I can about ballistics though.
Mark204, Chronographs don't lie. The tests I conducted revealed the true BC in my gun. I have also tested other guns and got similar results so unless you have positive proof and not just Internet speculation, I will believe my results.
This sonic transition thing has come up many times and continues to be more of a myth than a fact. I like to use a mere 22 LR high velocity cartridge as an example because it is a marginally stable bullet and a worst case example. Most everyone knows about CCI Minimags, so I'll use them for the following example.
Using CCI's factory specs, when fired from a 18.5" barrel, a 38 gr High Velocity Minimag develops a velocity of about 1260 fps from a 18.5" barrel, which is well above the speed of sound (about 1150 fps). Minimags have a poor BC .... .125 and by the time the bullet travels 35 yards, velocity has dropped to 1154 fps, right at the speed of sound. I think we all know .... Minimags can develop one hole accuracy at 50 yards and sub-inch accuracy at 100 yards with the right rifle. So my question is .... Where's the big hairy transonic loss of accuracy from sonic transition?
There are many different drag tables used for various bullets. The difference between a G7 and a G5 is negligible for all but very long range shooters. So if it makes you feel better, use G7.
This sonic transition thing has come up many times and continues to be more of a myth than a fact. I like to use a mere 22 LR high velocity cartridge as an example because it is a marginally stable bullet and a worst case example. Most everyone knows about CCI Minimags, so I'll use them for the following example.
Using CCI's factory specs, when fired from a 18.5" barrel, a 38 gr High Velocity Minimag develops a velocity of about 1260 fps from a 18.5" barrel, which is well above the speed of sound (about 1150 fps). Minimags have a poor BC .... .125 and by the time the bullet travels 35 yards, velocity has dropped to 1154 fps, right at the speed of sound. I think we all know .... Minimags can develop one hole accuracy at 50 yards and sub-inch accuracy at 100 yards with the right rifle. So my question is .... Where's the big hairy transonic loss of accuracy from sonic transition?
There are many different drag tables used for various bullets. The difference between a G7 and a G5 is negligible for all but very long range shooters. So if it makes you feel better, use G7.
Mark, Here's a few charts from Ballistic Explorer. As you can see, this is not just something I made up .... sonic transition occurs at about 35 yards where the bullet's velocity drops to 1154 fps. The specifications for CCI Minimags came from Ballistic Explorer's internal data base as noted in the upper right window. If you use Windows, you can hit CTRL and + to enlarge the charts.
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