I currently do not own a chrono to measure my velocities of my loads- saving up for a new scope, kids college, chrono, new truck, etc......Does anyone know how accurate the velocities listed in load data tables are? I understand that using any component other than what is listed can change things, I’m just curious as to whether anyone has “ground truthed” velocities listed in various tables. I use mostly Hornady bullets, so I usually use their book, among others. Just curious.
Load Data Velocity Accuracy
- Thread starter Wyo82
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mcb
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It can vary widely. Barrel length you're using compared to what was used to work the load up has a big effect but so do some other factors harder to measure like free bore, barrel friction, etc. Most data is reasonably close assuming similar barrel lengths but some of the published data will be way off even with the same barrel length.
NMexJim
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I second mcb on barrel length.
I’m not too surprised to find I’m off 100/200 FPS from book, but it’s a good start. Altitude and internal ballistics will cause things to change. Cross reference is good if you’ve got the books. Decent scales, good loading and seating skills can be as important. Maybe avoid the max/mins until you get a chrono.
rfwobbly
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► The entire premise of your question reveals the root issue. The people generating the data are primarily concerned with chamber pressure. They are trying to answer the question: "Which loads are safe and won't blow up the user's gun ?" But users are more focused on velocity to insure the chamber pressure is within limits. So we have one set of data, used 2 different ways.
► I agree. Barrel length is probably the biggest reason that factory reports seem optimistic. Especially in handgun loads, they typically use a 12 to 16 inch barrel. But many users are trying to replicate the load with less than 4 inches. This can make the data (especially for handgun) look exaggerated.
But those who collect the data have their hands tied. While you can realistically drill and tap a bolt action rifle to give you pressure data, due to the small and complex mechanisms of a handgun, this is nearly impossible. So for handgun calibers, the labs are stuck using the standard length "test barrels".
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► I agree. Barrel length is probably the biggest reason that factory reports seem optimistic. Especially in handgun loads, they typically use a 12 to 16 inch barrel. But many users are trying to replicate the load with less than 4 inches. This can make the data (especially for handgun) look exaggerated.
But those who collect the data have their hands tied. While you can realistically drill and tap a bolt action rifle to give you pressure data, due to the small and complex mechanisms of a handgun, this is nearly impossible. So for handgun calibers, the labs are stuck using the standard length "test barrels".
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edwardware
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They are very accurate, since the labs that develop data have good equipment.
But I think you might be confused about the meaning of the word "accurate". There is no reason to imagine that velocity from your equipment will match the data in the book. You're using a different barrel, with a different chamber, with a different batch of brass, powder, primer, and bullet.
It's not unusual to see a 100fps change in velocity solely for a change in bore/groove dimension and finish between barrel manufacturers. Add chamber and throat dimensions, or barrel length. . . and off we go.
This isn't an indication that the book is inaccurate; it's an indication that you're collecting different data. A chrono is NOT a pressure measurement device, and is not useful for detecting excessive pressure. You can easily be far in excess of peak design pressure, with velocities well below book, simply for normal variation in components and chamber/bore dimensions.
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Typetwelve
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Pretty much 100% of the time, I'm seeing less velocity than what is listed, which is a-ok by me. Like everyone is saying, they often use much longer barrels than I am and in much more controlled environments than I am...so it is my results that are inaccurate, not theirs.
buck460XVR
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Far too many reloaders(especially new reloaders) are far too concerned with velocity as opposed to accuracy. As they get more experienced they find 50-100fps means little compared to 1 inch groups as opposed to 3 inch groups. As others have mentioned, there are also many other variables involved with stated velocities. Many recipes use a test barrel for revolver ammunition which do not have the cylinder gap. Velocities given are also the average of a string of shots fired. Even very accurate ammo can have a ES of 50 fps or more.
AJC1
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This.
You are getting lab grade data from people trying to protect themselves.
Thanks for the replies, I guess I should elaborate a little, I mostly load bottleneck rifle cartridges, and to be quite honest, I load for accuracy more than speed. If I can get a tight half moa group or sub at 200 yards, velocity isn’t much of a concern to me. I don’t think the coyotes/mulies/antelope/elk are going to notice if it’s going faster or slower when they get center punched in the engine room. I was just curious if anyone had any ground truth to the matter, even though as has been said, readings will be varied dependent on if shots are from a 16,20, or 24” barrel, what the twist rate is, etc. This was just a general curiosity question.
My journey was just like that. Chased velocity way too long until a near disaster. I guess I scared that out of my system.
AJC1
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It's not about back to your corner its completely about you understanding and knowing how to be safe.
I don’t know why, but it just dawned on me today that they are just listing their results. Not that it will actually apply to the loader because of al the variables, but just what their results were for reference. Like a lightbulb clicking on at a random moment. Thanks everyone.
NMexJim
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So, the bottom line is that you can go quite a ways w/o a chrono and by just using book.
I find that most of my accurate loads happen in the upper book range - not max but up there. You might think about powder density as well. Gettin a powder that gives you the velocity you’re looking for and fills your case (bullet seated - I’m sure how-to is on this forum) as much as possible helps as well. If your book gives an “most accurate” load that you can duplicate, that might help too.
I was thinking back on the years when I didn’t have one, and hunting loads still worked well. It was when I started needing < moa for varmint shooting and silhouette that I found I had to have one. But, at that point, it won’t only be a chrono. Luckily I had a good job then.
have fun.
I find that most of my accurate loads happen in the upper book range - not max but up there. You might think about powder density as well. Gettin a powder that gives you the velocity you’re looking for and fills your case (bullet seated - I’m sure how-to is on this forum) as much as possible helps as well. If your book gives an “most accurate” load that you can duplicate, that might help too.
I was thinking back on the years when I didn’t have one, and hunting loads still worked well. It was when I started needing < moa for varmint shooting and silhouette that I found I had to have one. But, at that point, it won’t only be a chrono. Luckily I had a good job then.
have fun.
Jim Watson
Member
SAAMI standard rifle barrel length is 24" for most calibers.
Lots of shorter barrels for handiness.
A SAAMI P/V test barrel is held to much closer tolerances than production guns.
-0.0 / +.0005" on diameter, vs -0.0 / +.002".
Since all barrel and chamber tolerances are plus values, the test barrel is probably going to be "tighter" than yours, increasing pressure and velocity.
Lots of shorter barrels for handiness.
A SAAMI P/V test barrel is held to much closer tolerances than production guns.
-0.0 / +.0005" on diameter, vs -0.0 / +.002".
Since all barrel and chamber tolerances are plus values, the test barrel is probably going to be "tighter" than yours, increasing pressure and velocity.
rfwobbly
Member
Sorry, but this statement covers such a wide territory that it is nearly meaningless. Are we talking about rifle, handgun or shotgun ?
I'm not picking on NMexJim because I read and appreciate his usually thoughtful statements. But what we need to guard against most in this hobby is over generalization. Just because a truth may be discovered in your specific area of reloading (say 30 caliber bolt action rifle) doesn't mean is applies equally to sub-30 caliber auto pistols, or over-41 caliber revolvers, or 12ga shotguns.
To imply such a "rule" urges the novice reloaders among us to skip the Starting Load and proceed directly to upper range loads. And that's simply dangerous.
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Just a single data point example of manual velocities and real world velocities.
My first AR style Service Rifle Competition rifle was a stock Colt Match Target with a 20" barrel. The Sierra Bullets load manual that I used at the time used a Colt Match Target rifle with a 20" barrel for their test rifle. For the couple powders and Sierra bullets that I was using, my velocities very closely matched the Sierra data.
I upgraded to a Compass Lake match rifle, similar A2 configuration as the Colt with a 20" barrel. With the same loads as used in the Colt, the velocities were 10% (200+ fps) faster in the Compass Lake.
As a result, ever since, I like to chronograph some factory ammunition with my firearms. It gives me an idea if the gun shoots fast or slow when I'm developing accurate loads.
My first AR style Service Rifle Competition rifle was a stock Colt Match Target with a 20" barrel. The Sierra Bullets load manual that I used at the time used a Colt Match Target rifle with a 20" barrel for their test rifle. For the couple powders and Sierra bullets that I was using, my velocities very closely matched the Sierra data.
I upgraded to a Compass Lake match rifle, similar A2 configuration as the Colt with a 20" barrel. With the same loads as used in the Colt, the velocities were 10% (200+ fps) faster in the Compass Lake.
As a result, ever since, I like to chronograph some factory ammunition with my firearms. It gives me an idea if the gun shoots fast or slow when I'm developing accurate loads.
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Nah, not at all. Look I use a cheap Chrony and do a lot of velocity work. But I think most of us have learned from the precision world. Velocity is only a piece and maybe less than we thought. I look at the whole data set. Accuracy, functionality, then velocity, standard deviation, and extreme spread.
Good question just not the whole question.
jmorris
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Then there is accurate velocity.
I think a number of folks would be happier if they didn’t own a chronograph, same as most people that buy and shoot factory ammunition.
I agree that figures are often optimistic but, as above, you are not comparing apples to apples. If you are trying to get the figures they did, you need a firearm as close to the one they used.
Of course, we then would have to define “accurate” pertaining to velocity as well as what devices we use to collect our data. For example, I can put a number of chronographs in a row and they won’t all agree on a specific velocity of a single round passing over them.
Turns into a “ a man with one clock always knows what time it is, a man with two is never sure.” Just remember it’s just another tool and not the be-all and end-all.
I don’t read anything he wrote as “implying a rule”. He was speaking to HIS findings of HIS loads. Simply stating what he has experienced with his loads. No generalization of max loads = max accuracy. And if a novice/beginner is stupid enough to start a load at max or + max, so be it. Darwinism.
Now I would completely understand your statement if @NMexJim had stated or implied a dangerous rule, but he was only giving his findings.
NMexJim
Member
rf has a point. I read "rifle" somehow into the OP, and on going back over Wyo82s post, I indeed see that the post does not concern strictly rifle calibers. I will admit that I don't happen to employ a chronograph very often when pistol shooting, and I just don't think in terms of a chronograph for that purpose. I have years of notes on pistol that are my base plus I really am not a speed chaser. Mea culpa.
However, Wyo82, if your post is indeed concerning rifles, I'll stand by the statement. I've helped quite a few folks dial in new-to-me cartridges, and we have found best results in the upper range. As I stated earlier, not necessarily max.
Oh, and let me add that I'm an NSCA shooter, and ALL my loads are book.
My post is indeed concerning rifle rounds - the only pistol I load for is 500 S&W Mag. But my original post is concerning rifles. 90% of my time reloading is for rifle rounds. My argument to RF was that you weren’t giving a blanket, written in stone, cover all rule for new reloaders, you were just sharing your experience that you’ve had.
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