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MID-MAY column: Velocity of Factory Ammo #13824372 05/16/19
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VELOCITY OF FACTORY RIFLE AMMUNITION

Rifle shooters often complain about low velocities in factory ammunition. This does occur frequently, but obviously they don't understand why--and there are several reasons.

The major problem with producing factory ammunition that lives up to its so-called "advertised" velocity is that rifles vary so much. In fact, the organization commonly known as SAAMI (the Sporting Arms and Ammunition Manufacturers Institute) was started in the 1920's because of that very reason. So many companies made ammunition and rifles that not all ammo worked safely, or even reasonably well, in rifles chambered for the same cartridge. SAAMI was started companies could get together and set reasonable standards for cartridge dimensions, pressures and velocities, so somebody could buy a box of, say, .30-30 ammo and have it work reasonably well in any factory .30-30 rifle.

One of the problems with such a project is that any mass-machined product will vary slightly in dimensions, partly because of tooling wear--exactly why SAAMI lists both maximum and minimum dimensions for rifle chambers and bores. Factories start with slightly over-sized (maximum SAAMI dimension) barrel and chamber reamers, then run the reamers until bores and chambers meet SAAMI minimum standards. (The same principle applies to ammunition factories, which start with maximum-dimension case-forming and bullet dies.)

Minimum chambers and bores result in higher pressures, and hence velocities. The head tech at one of the major piezo-electronic pressure labs in the U.S. told me a few years ago that with the centerfire rifle cartridges most of us use up to .30 caliber, a difference of .0001 (one ten-thousandth) inch in bore diameter results in a difference of about 1000 pounds per square per square inch (PSI) in pressure. One general rule of interior rifle ballistics is that any change in pressure results in about half as much change in muzzle velocity, and factory bores can and do vary as much as one-thousandth (.001) inch diameter. Obviously this can result in considerable differences in both pressure and velocity.

The same thing can occur to a much greater extent with chamber throats. A shorter throat can raise pressures enormously, and can occur even in chambers for very common cartridges.

About 20 years ago I bought a used factory .30-06 produced by a major European company. These days there's considerable agreement between SAAMI and the C.I.P. (Commission Internationale Permanente), the European organization that performs the same industry standardization over there, but the .30-06 was apparently made before that cooperation began.

When I bought the rifle, a major American ammunition company had recently introduced rifle ammunition specially loaded to produce higher-than-normal velocities, yet with pressures at standard SAAMI levels. After mounting a scope and sighting-in the rifle, I tried some of the high-velocity 180-grain .30-06 ammo. Muzzle velocities from the 22-inch ran a little over 3000 fps, and the third round blew a primer.

I contacted the ammo company and they asked me to send the rest of the box back for testing. A few days later they reported pressures averaged 58,000 PSI, right in the correct SAAMI range for .30-06 ammo. I then measured the throat length in the Euro-rifle, through the simple but effective technique of seating a flat-based bullet backwards in a resized case, then chambering the round. It took some effort to close the bolt, and the shank of the bullet in front of the case mouth revealed a considerably shorter throat than SAAMI standard.

This is also why many custom rifles show higher velocities with factory ammo than many factory rifles: Many custom gunsmiths use "minimum" dimension reamers to enhance accuracy. Such rifles often get more velocity than SAAMI standards with factory ammo.

A good example is my NULA Model 24 .30-06. With the same 180-grain ammunition that turned my Euro-rifle into an unsafe .300 magnum, got 2950 fps from its 24" barrel. There weren't any evident pressure problems, but I would bet 100 pieces of Lapua .30-06 brass the pressures averaged over 58,000 PSI. All of which is why SAAMI allows their member companies 90 fps either way from their factory-ammo muzzle velocity standards.

Many companies seem to be happier with 90 fps less, no doubt due to safety considerations, but that's when fired at 70 degrees, the standard temperature for SAAMI test-firing, the reason modern pressure labs are air-conditioned. While today's rifles are very strong, there's no way an ammo company can predict what temperature a shooter in the Great Outdoors will encounter, whether when hunting or on a target range. And even the most temperature-stable modern powders will gain noticeable velocity (meaning higher pressure) at much above 70 degrees.

Ammo companies also can't predict the condition of an individual rifle's bore. It may be very dusty or damp, or even rusty. All three condition can raise pressures considerably.

Another factor is barrel length. Well into the 1980's most ammo companies quoted velocity figures from 26-inch test barrels, but by then relatively few factory rifles had 26-inch barrels, with most running 22-24 inches. The general rule-of-thumb is a loss of 25-30 fps per inch of barrel, but that can also vary considerably, due to the powder used or bore dimensions. Eventually SAAMI standardized most rifle test barrels at 24 inches, with some exceptions for rounds often fired in carbines. The standard for the .30-30, for instance, is 20 inches.

[Linked Image]
Whether factory ammunition chronographs the same in your rifle as the test barrel depends on many factors. The 100-grain Remington factory ammo turned out to be slightly faster than the listed 3230 fps from the 24-inch barrel of this Ruger No. 1 .25-06.


SAAMI also allows member factories to produce (and list) ammo with somewhat lower velocities than their standard for a given bullet weight, if the particular bullet results in higher than "normal" pressures. Fifty years ago almost all rifle bullets were cup-and-cores with very similar construction, so resulted in very similar pressures. Today lead-cored rifle bullets vary enormously in construction, anything from very thin-jacketed cup-and-cores to bonded bullets with much thicker jackets, often made of pure copper, which results in more friction than the gilding metal (a mild brass) used in most jackets.

Plus there are several brands of "monolithic" bullets, made of copper, gilding metal, harder brass or even bronze. These not only tend to be harder than lead-core jacketed bullets but can produce widely different pressures, due to the widely varying numbers and sizes of grooves in their shanks to reduce pressures.

As a result, not all rifle ammunition will be loaded up to the velocity standards suggested by SAAMI. Because of the maximum diameter of many factory rifle bores, it will tend to result in even lower velocities in those rifles.

Another factor often resulting in lower velocities is temperature, plus the chronograph used. While most shooters probably prefer going to the range at 70 degrees, obviously they can't control outdoor temperature, and often can only go on a certain day. In much of the country, range-testing gets done during winter, because summers are for family vacations or too damn hot. Fall is hunting season and spring frequently too windy for decent group-testing.

Typical winter days are usually cooler than 70 degrees over much of the country. While a bunch of cold-resistant powders are now available to handloaders, most factory ammo doesn't use them. Instead they load powders that we often wouldn't even recognize by their designation, though most at least resemble some handloading powders, because they come out of the same factories. At cooler temperatures many will lose around two fps per degree Fahrenheit, which means about 60 fps at 40 degrees.

[Linked Image]
Factory ammo will usually chronograph slower in cooler conditions. This isn't a winter day, but since I'm wearing a jacket it probably isn't 70 degrees.

Then there's the shooter's chronograph, which may or may not provide accurate results. While "personal" chronographs have improved considerably over the past couple of decades, partly through using something other than ambient light to trip their sensors, most shooters still buy inexpensive light-screen chronographs. While most are accurate, one of the most popular brands can vary considerably, as I found out while testing three of 'em over the years.

Right now I own five chronographs costing from $100 to over $500, including non-light-screen models, and test them for accuracy against each other. At least one of the inexpensive brands is consistently accurate, but even accurate chronographs can provide varying results when their batteries are low.

All these reasons are why factory ammo may not chronograph within 200 fps of the listed velocity in YOUR rifle--and will normally chronograph slower than listed, and rarely even slightly faster. But the major reason, again, is because ammo factories have to design ammo to be safe in minimum dimension chambers and barrels. If they "worked up" ammo in barrels with maximum chambers and barrels, their ammo could cause problems in minimum-dimension barrels, as we've seen.

The reamers used in factories aren't made of the same sort of steel used in custom reamers, so wear quicker As a result, the odds of any particular factory rifle having a minimum-dimension chamber and bore are pretty small, probably around 15-20%. As a result, your particular factory rifle probably won't shoot factory ammo to the listed velocity, though part of the reason may be a 22-inch barrel, rather than the 24 used in most factory testing.

Whether this makes any difference in most hunting is another question. My wife cleanly killed one of her first deer on a cold Montana day with 130-grain .270 factory ammo that only got around 2700 fps when I finally ran it over a chronograph that winter. Despite the low velocity, the deer flopped right over, because Eileen shot it in the right place at around 75 yards. Since her .270 was sighted-in two inches high at 100 yards, the same hold would have worked fine out to 250 yards, which includes over 90% of the big game killed every year.

Factory ammo that didn't meet listed velocity specifications was common even before we started buying our own chronographs. That .270 load was chronographed in the winter of 1984-5, but the very first handloading manual I purchased, Speer's #6, was published in 1964. It includes a list of factory ammo chronographed in their indoor lab, almost all rifle ammo or handgun ammo shot in rifles, like .44 Magnum in a Ruger semiauto carbine.

The 47 cartridges ranged from the .22 Hornet up, and included a total of 126 loads. Only 41 of those loads (32.5%) came within 50 fps of the listed velocity. Of those a mere 15 exceeded the listed velocity, and never by more than a few fps. Among the big losers were ALL of the five .243 Winchester loads chronographed, none of which came within 100 fps of listed velocity, with most more like 200-250 fps, partly because the test rifle was a 22-inch barreled Winchester 88, and the factory-listed velocities came from a 26-inch test barrel. The only cartridge where all ammo came within 50 fps was the .44 Magnums in the Ruger carbine.

My guess, based on considerable chronographing of factory ammo in various rifles over the past 40 years, is the same sort of test would provide similar results today, because even back then factories were obviously loading on the premise of never exceeding listed velocities in minimum-dimension rifles. If this upsets some shooters, perhaps they should heed Colonel Jessup's famous line from the movie A FEW GOOD MEN, delivered so memorably by Jack Nicholson: "You can't handle the truth!"


“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck
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Re: MID-MAY column: Velocity of Factory Ammo [Re: Mule Deer] #13824467 05/16/19
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Another good write up that helps explain the real world. Well written and well done!
In my limited experience, I have often found factory ammo that was slower than advertised, tended to be quite accurate.
On the other hand, I tend to regard as genius, those whose opinions agree with mine. smile


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It's been 50 since a visitor last paused at your tombstone.....
Now explain why you're in a pissy mood today.
Re: MID-MAY column: Velocity of Factory Ammo [Re: Mule Deer] #13825071 05/16/19
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Great read, John. The only ammo I have used that’s all that is advertised and a bag of chips is Weatherby factory stuff.


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Re: MID-MAY column: Velocity of Factory Ammo [Re: Mule Deer] #13825120 05/16/19
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Very interesting piece. Over the years whenever I began loading for something new or just out of curiosity for some new factory load I'd chrono some of that factory load and also see how well it shot in my own rifle. Just as a sort of benchmark, or if it was very accurate I'd see if that particular velocity range was a sweet spot for a hand load with that bullet weight. Never did trust advertised velocity figures, anyway and it's interesting to know what it does in YOUR gun, with YOUR barrel length in real world temperatures and not in another gun set up in a controlled condition ballistics lab. Besides; I gotta justify spending that money on the chronograph.

Re: MID-MAY column: Velocity of Factory Ammo [Re: WAM] #13825128 05/16/19
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WAM,

Have chronographed some Weatherby stuff that was slower than listed--and in Weatherby rifles. Usually it is right up there, though!

Generally, it's due to more to the rifle than the ammo. Have chronographed batches of the same case-lot of ammo in various rifles, and gotten widely differing results. In fact, just chronographed some the other day that was basically right at specs in a new-to-me factory rifle, though it never has been that fast in other factory rifles, though in one other it was close.


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John Steinbeck
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Re: MID-MAY column: Velocity of Factory Ammo [Re: Mule Deer] #13825334 05/16/19
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MD,
Mine was a small sample of Wby ammo in Wby rifles. 7mm Wby 175 and 139 gr factory loads averaged less than 10 FPS differences from spec. Some .300 Wby factory 180 gr Norma Spitzer (the cheap stuff) actually chrono’d a couple FPS faster. I just bought that for the brass. My previous statement was a bit of a generalization. Happy Trails

PS: I don’t use factory ammo in any of my Wby caliber rifles. Too expensive. I handload TTSX bullets for hunting use with good results.

Last edited by WAM; 05/16/19. Reason: PS

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Re: MID-MAY column: Velocity of Factory Ammo [Re: Mule Deer] #13825530 05/16/19
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Good write!! Interesting to me what's on the chronograph I have noticed my chronograph when I use batteries as the battery weekend it would read higher velocities. I now have it set with a 110-120 conversion so it's consistent at all times.
And I can agree on the 243 also very few of I ever reached book velocities even considering the barrel length. That's even with handloads.

Re: MID-MAY column: Velocity of Factory Ammo [Re: Mule Deer] #13840893 05/22/19
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That's basically the point of the article: The major reason most factory ammo (or handloads) are "slow" is the rifle, not the ammo. The factories and handloading manuals aren't lying. They got their results.

But the average factory rifle has a larger chamber, longer throat and looser barrel than the average factory rifle.

A good example is the same batch of factory Hornady Precision Hunter 6.5 Creedmoor ammo I recently chronographed in three different rifles. Hornday lists it at 2700 fps from a 24" barrel. Here are the results, all on the same chronograph:

22" barreled T/C Compass:: 2608 fps
24" barreled Franchi Momentum: 2619 fps
24" Bergara B-14 Ridge: 2694 fps

So which one is "correct"?


“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck
Re: MID-MAY column: Velocity of Factory Ammo [Re: Mule Deer] #13840941 05/22/19
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D. None of the above.


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Re: MID-MAY column: Velocity of Factory Ammo [Re: Mule Deer] #13840977 05/22/19
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In this day and time, I'm amazed that most don't understand all the correlations.

In years past we played with lots of combos to try to find a bit faster speed, at safe pressures, and its amazing how many things change MV and pressure.

I know you say you can't get more speed without more pressure and its true, but some stuff we did, that was roughly pressure tested after the fact showed above "expected" speeds while showing same pressure signs as factory ammo. Per a Chris F whatever those tests were where you glued a testing gadget to the barrel etc...

But so many things can change pressure... hence the safe disclaimer RE start LOW.. below max.

Good read.


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Bravo

Re: MID-MAY column: Velocity of Factory Ammo [Re: Mule Deer] #13849437 05/26/19
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John,

Thanks for the write up and posting it for we minions...

Informative as always....

cheers and best regards.




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Re: MID-MAY column: Velocity of Factory Ammo [Re: Mule Deer] #13853916 05/27/19
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Thanks for the good article, John.

Occasionally when I am at the range shooting through my chronograph I am approached by another shooter curious about the chronograph. It is frequently obvious that they are curious about the factory ammo that they are shooting. I usually offer to let them take a couple of shots through the chronograph, but I warn them that the result will almost certainly be lower than they expect.

The 243 Winchester rifles have been the most deficient in velocity of the various factory loads that have been tested over the years, for some reason (frequently 200 to 250 fps slower than factory claim). The owners of the rifles at first believe they have purchased a bad box of factory ammo, until I run through some of the points covered in the article. I even tell them ahead of time, "don't shoot it through the chronograph if you aren't prepared to be disappointed".


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Re: MID-MAY column: Velocity of Factory Ammo [Re: nifty-two-fifty] #13854355 05/28/19
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Yep!

I bought my first chronograph in 1979, when they were pretty rare. In fact mine was the only one seen at local ranges for several years. As a result, quite a few people asked if they could try a few shots--and shooters using both factory and handloaded ammo were ALWAYS disappointed, even if they'd been using the ammo effectively for years. I can't remember any where the ammo wasn't at least 100 fps slower than they expected, and often it was 200-250 fps.


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John Steinbeck
Re: MID-MAY column: Velocity of Factory Ammo [Re: Mule Deer] #13867837 06/02/19
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navlav8r Offline
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Originally Posted by Mule Deer
That's basically the point of the article: The major reason most factory ammo (or handloads) are "slow" is the rifle, not the ammo. The factories and handloading manuals aren't lying. They got their results.

But the average factory rifle has a larger chamber, longer throat and looser barrel than the average factory rifle.

A good example is the same batch of factory Hornady Precision Hunter 6.5 Creedmoor ammo I recently chronographed in three different rifles. Hornday lists it at 2700 fps from a 24" barrel. Here are the results, all on the same chronograph:

22" barreled T/C Compass:: 2608 fps
24" barreled Franchi Momentum: 2619 fps
24" Bergara B-14 Ridge: 2694 fps

So which one is "correct"?



So JB with your second paragiraffe 😀 in mind, do the factories attempt to go with minimum dimension bores, chambers, throat, etc. for their test barrels so they get a worst case scenario?


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Re: MID-MAY column: Velocity of Factory Ammo [Re: navlav8r] #13867911 06/02/19
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From what I understand, to a certain extent. But I haven't visited every ammo factory, or had the opportunity to talk to the techs of every factory pressure lab.


“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck
Re: MID-MAY column: Velocity of Factory Ammo [Re: Mule Deer] #13867931 06/02/19
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I found this out with a Sauer 101 in 7X64, first time I had a reloading book that gave a load I could EXACTLEY match. Rifle, Powder, Case, Bullet, Primer, COL etc. It was about 200fps slower than what the manual said. Funny thing was some factory Barnes ammo was only about 50fps from what they advertised. Perhaps my chrono was having a bad day, I have see it vary before. I have pretty much given up on getting the most I can from a rifle/cartridge, if the load is in the ballpark and accurate, I figure I am go to go.

Last edited by smithrjd; 06/02/19.
Re: MID-MAY column: Velocity of Factory Ammo [Re: Mule Deer] #13868136 06/02/19
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Nice write up John! Thanks.


~Molɔ̀ːn Labé Skýla~
Re: MID-MAY column: Velocity of Factory Ammo [Re: smithrjd] #13868206 06/02/19
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smithrjd,

What kind of chronograph?


“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck
Re: MID-MAY column: Velocity of Factory Ammo [Re: Mule Deer] #13868210 06/02/19
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A Master Chrony. Been looking at a Labradar, but the dog needed a Vet trip and that blew the budget.

Re: MID-MAY column: Velocity of Factory Ammo [Re: smithrjd] #13868716 06/02/19
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I trust any Shooting Chrony about as far as I'd trust a crack addict.

Just got a Labradar and so far it's impressive. For an inexpensive light-screen chronograph, would recommend the ProChrono Pal. For a really not schict chronograph would recommend the Oheler 35P, partly because it works very well, and partly because it provides a double-check of every velocity--which is appatrently why Bryan Litz now uses TWO Labradars.


“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck
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