There is not a wide selection of factory ammunition for the 38 Super compared to other cartridges. The 38 Super has only moderate popularity in the United States where the overwhelming majority of 1911s are chambered for the 45ACP, and the 1911 was, until recent years, one of the few platforms to offer the 38 Super. That, and the fact that most medium caliber semiautomatics favor the 9mm Luger cartridge, has delegated the Super to a minor position in the minds of most ammunition manufacturers with a limited choice of bullets and load options.
The major three U.S. ammunition makers Remington, Winchester and Federal all offer the token 130 grain FMJ round. Winchester offers a hollow point bullet – the 125 grain Silver Tip Hollow Point, and Federal has a 115 grain JHP . Speer (CCI) has no 38 Super load. PMC offers a 115 grain hollow point, though the ballistics are the same as the lesser performing 9MM Luger. American Ammunition offers a 115 grain load. Other ammunition makers have stepped into the U.S. 38 Super market. Magtech, Prvi Partizan and Aguila offer the standard 130 grain FMJ load. Fiocchi's version weighs 129 grains and Armscor's weighs 125 grains. Frangible Bullets offers a load with a frangible bullet made from compressed metal powders. Atlanta Arms and Ammo offers a 125 grain hollow point round, including a load in rimless SuperComp brass (see the Brass section of this website). Double Tap, Buffalo Bore and Georgia Arms have added the 38 Super to their lineups. Custom gun maker Wilson Combat has started a line of custom ammunition which includes three loads for the Super.
These three photographs show examples of the typical bullets for the 38 Super with round nose bullets from Remington and Magtech, and the flat nose match bullet used in the CORBON load. The Winchester 130 FMJ FN resembles the CORBON profile. The rounded profile of the Remington bullet is similar to those used by Winchester, PMC, Fiocchi and Aguila. The more pointed bullet profile of the Magtech bullet is similar to the bullets used by Armscor, Federal, Frangible Bullets, Prvi Partizan, and American Ammunition. Photographs of the hollow point and specialty bullets can be found below in the Bullet Performance section.
CORBON offers an astonishing seven loads for the 38 Super. Most are very high performance and demonstrate the Super's full potential (see Tables 1 and 2 below). They offer two traditional jacketed hollow point bullets, both varieties of the Glaser Safety Slug (Blue and Silver), an all copper Barnes bullet, the unique Pow'RBall and a Performance Match load. The Glaser Safety Slugs are prefragmented bullets that consist of a copper jacket filled with birdshot and are designed to break apart quickly on contact to reduce penetration and ricochet hazard. The Blue version is filled with tiny #12 shot, and the Silver version is filled with a larger #6 shot. An appropriately colored polymer round ball seals the front of the bullet and aids in feeding reliability. The Pow'RBall bullet has a hollow-point-like lead core and copper jacket, but the bullet nose is a polymer ball that intends to ensure expansion, prevent plugging, and, like the Safety Slug, enhance feeding reliability. The all copper Barnes bullet is used in CORBON's DPX load, and also by Double Tap and Wilson Combat. This bullet is designed to produce excellent expansion, retain all weight, and penetrate deeply compared to conventional hollow point bullets. The bullet is unusually long for its weight because it is made entirely from copper which is less dense than lead and has a long, cavernous hollow point.
With the exception of the CORBON loads just mentioned, the bullet variety for the Super pales compared to most other cartridges. Bullets in typical factory ammunition range from 115 to 130 grains, with hollow point bullets in 115 and 125 grains. The 130 grain bullet is traditionally a full metal jacket round nose design. But the long case of the Super is capable of handling so much more. The 147 grain bullets in this caliber range are not represented by the major manufacturers but are offered by some smaller companies. Bullets in the more popular 9mm Luger run the range from 90 to 147 grains, and even 158 grain bullets have been loaded in this short case. Bullet weights of 105, 115, 124, 125, 135, 147 and 158 grains can be found for the Luger. For comparison, the Winchester website lists 11 separate loads for their standard 9mm Luger line with bullets weighing 105, 115, 124 and 147 grains. Winchester lists two loads for the 38 Super, 125 and 130 grain bullets. Exotic ammunition, such as the Glaser Safety Slug and Pow’rBall sport 80 and 100 grain bullets, respectively, for the both the 9mm Luger and 38 Super.
A brief note about size: The 38 Super has traditionally employed a .356 inch diameter bullet. By comparison, the 9mm Luger uses a .355 inch diameter bullet, and the 38 Special and 357 Magnum use a .357 bullet. In spite of the fact that the Super’s bullet diameter is traditionally .356, many current factory loads sport .355 inch bullets (see Table 1). You might think that shooting .355 bullets in a .356 bore would result in poor accuracy. This is not necessarily so, and there is more information on this topic in the .355 vs .356 section.
Two tables list information about most of the factory ammunition made by major manufacturers available in the U.S. Table 1 lists some of the specifications of the ammunition including measured bullet weight and diameter. For this data, two bullets were pulled from factory rounds and measured. The weight of both bullets is listed. Interestingly, bullet weight varied as much as 2 grains, although most varied only slightly or not at all.
Most factory loads had bullet diameters of .355 or .356 inches. In most all cases bullet diameter was very consistent. The bullets in the American Ammunition load were not the same diameter and were significantly oversized for a cartridge that normally uses a .356 bullet. The two bullets measured .359 and .361 inches in diameter and would have to be squeezed significantly to go through the typical 38 Super barrel. Their larger than normal diameter might (or might not) be a contributing factor in the elevated pressure signs noted in the primer (see Table 2).
Table 1: 38 Super Factory Ammunition
Cartridge OAL = Cartridge Overall Length. The SAAMI maximum overall length of the 38 Super is 1.280 inches. FMJ = Full Metal Jacket. FN = Flat Nose. HP = Hollow Point. JHP = Jacketed Hollow Point. JPRN = Jacketed Polymer Round Nose. Prefrag = Prefragmented. RN = Round Nose. STHP = Silver Tip Hollow Point. TMJ = Total Metal Jacket (plated). Unk = Unpublished. * Weight in grains. ** Barnes all copper HP bullet. *** CORBON has traditionally used a Sierra bullet for these loads. **** These are Zero bullets.***** Labeled as JHP, but the bullets are Speer's Gold Dot, which are plated. *^ Appears to be a Sierra bullet. ^ Loaded in rimless Starline 38 Super Comp. x Current offering is a flat nosed bullet. xx The bullets were not concentric. † The heel of the first bullet measured .359, and it measured .358 right up to where it was crimped. Just forward of the crimp it measured .355. The second bullet measured .361 at the heel, and .359 up to the crimp. In front of the crimp it measured .357.
Table 2 shows the published and actual ballistics of the rounds tested. All ammunition was fired through a Colt factory 5 inch stainless steel barrel under similar conditions (65-75 ˚F) with noted exceptions. Chronographed velocities in the test gun were close to published values. Some products actually exceeded their published velocity. This is a welcome surprise since most of the time actual velocity falls short of what the manufacturer claims. In most comparisons the differences between published and actual velocity was 1-3%. The rounds that were farthest below their published velocity were the Frangible Bullets, Fiocchi and Winchester 125 grain STHP. Their actual velocity was 5% or more below the published value. The round that was farthest above its published velocity was the Buffalo Bore 147 grain load. Its actual velocity was 5.7% higher than the published speed. The published ballistics and actual ballistics can vary for many reasons, some of which are listed farther down on this web page (go there now).
Table 2: Performance of 38 Super Factory Ammunition
Velocity was measured with a Shooting Chrony Alpha chronograph at 15 feet and is the average of 3-15 rounds. ME = Muzzle Energy. * Weight in grains. ** Ammunition is listed as Minor or Major power factor, which has to be specified when ordered. Their minor load has a velocity of around 1100 fps. *** Velocity tested at 32˚F. ^ The ammo tested was loaded in rimless Starline 38 Super Comp cases and was their Major power factor load. x Current offering is a flat nosed bullet. † Velocity in feet per second. †† Muzzle Energy measured in Foot Pounds and calculated as Bullet Weight times Velocity times Velocity divided by 450436. ∆ Power Factor is calculated as Bullet Weight times Velocity divided by 1000. OK = no elevated pressure signs in primers or cases. Slight = slight cratering of primers. High = cratered primers. Extreme = flattened and/or pierced primers and/or bulged cases.
Power factor is listed here because of the popularity of the Super in some types of competition where power levels distinguish between how the hits are scored. The 38 Super is often the caliber of choice for Open Division in the International Practical Shooting Confederation (IPSC; The U.S. chapter is the United States Practical Shooting Association - USPSA.) A power factor of at least 165 is required (in the U.S.) for Major scoring. Of the factory ammunition tested here, several cartridges made this grade, including loads from Atlanta Arms and Ammo, Buffalo Bore, CORBON, Double Tap, Georga Arms and Wilson Combat. Almost all Super shooters handload their ammunition for these types of competition, and there is more information on this subject in the Major Power Factor Ammo section (here) of this website. The Atlanta Arms and Ammo round tested was loaded specifically with the competitive shooter in mind. They offer ammo in two loads, a Major power factor (tested) and a Minor power factor, which produces about 1100 fps velocity. They also offer the round in rimless Starline 38 Super Comp cases (tested) - which might need extractors tuned to this case (see the Brass page for more information on rimless cases).
Readers should note that several loads from CORBON, Atlanta Arms and Ammo, Armscor and Double Tap loads showed signs of extremely high pressure. This is bad. The examples with an “Extreme” pressure rating exhibited flattened and/or pierced primers and the CORBON loads had a dangerous swelling of the case (see Pressure below). Both of these conditions are warning signs that the load is too hot and there are genuine risks of damage to the gun and injury to the shooter (see below). Also, if metal from the primer plugs the firing pin hole, then the gun won’t fire (which occurred repeatedly during these tests!!), and that would be very bad if you were using the ammunition for self-defense.
These manufacturers make great ammunition, and some certainly bring maximum performance to many cartridges. High performance loads push these rounds to maximum pressure. I purchased other lots of CORBON 38 Super ammo for comparison. I noted that one lot of their 125 grain JHP had reduced pressure signs, and less velocity. I am not trying to dissuade people from buying ammunition from these manufacturers. Some guns show pressure signs with some ammunition while others do not. I do not know the actual pressure of these rounds since this was not tested. They might be within SAAMI specifications. Always test the ammunition that you intend to use for self-defense in your gun to make sure that it is safe and reliable. After all, you don't want a malfunction when you're fighting for your life.
Expanding bullet types (hollow point, Pow'rBall, prefragmented) were fired into water jugs to test expansion and penetration. The jugs were one gallon milk or drinking water plastic jugs made of (what appears to be) the same type of material and relative thickness. The width of the bottom half of the jug measures 6 inches. Because there is an integral handle on the upper half of the jugs that reduced the width on two sides, the lower half was targeted so that the bullet would pass through the full 6 inches of water of each jug. Entry and exit holes were inspected to confirm the bullet's path, and the test was repeated if the bullet coursed through the upper, narrower portion of the jug, but this rarely happened. Tests were conducted at 15-20 feet. A short video demonstrates the test procedure.
The bullets demonstrated expansion/disintegration and variable penetration that was related to their design. The numbers are presented in Table 3. Conventional jacketed bullets (copper jacket around a lead core) passed through at least two jugs and stopped in jug #3 or #4. Expansion varied but all bullets opened up to at least half an inch.
Atlanta Arms and Ammo used a Zero 125 JHP bullet in their loading. It is intended more for competiive shooters who are trying to make Major power factor. And Zero bullets are a commonly used by competitors, as they offer good accuracy at a price that is often lower than more mainstream bullets. The Zero bullet produced reasonable penetration at high velocity but shed a lot of weight.
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The Buffalo Bore 115 JHP load is the same bullet (Sierra) as the CORBON 115 JHP and at similar velocity. It did not show a core/jacket separation in the expansion tests but expanded to a similar size. It did not penetrate as far as the CORBON test (see Table 3). It is an example of the variability that can be seen in bullet performance. Buffalo Bore's 124 grain round showed deep penetration and nearly full weight retention.
Buffalo Bore's 147 grain load showed significant fragmentation in spite of offering good penetration. It's possible that the bullet is being pushed beyond is intended velocity window. The 147 grain Gold Dot bullets are typically run at 9mm Luger velocities of around 1000fps, and this load was 200fps faster, which might explain why the bullet came apart.
The CORBON jacketed hollow point bullets demonstrated dramatic expansion. Their lead cores had lost the most weight of the conventional hollow point bullets. Their high velocity likely contributed to this effect. Bullets are engineered to expand to an optimal degree within a prescribed velocity range. If velocity is less than this range, the hollow point will not expand very well. If velocity is greater than this range, expansion can be excessive and the bullet is more likely to break up. The degree of bullet expansion is determined by the materials used for construction and the bullet's design and velocity. All else being equal, higher velocity generally means more expansion. Expansion becomes "extreme" when the bullet starts to disintegrate, and it can result in less penetration simply because the small parts have less mass and therefore less momentum. It is possible that the velocities achieved in CORBON's 38 Super loads exceeded the designed speed for these bullets. Or not.
The CORBON Pow'RBall bullet had nice expansion and the lead core lost very little weight, though the core did separate from the copper jacket.
Explosive disintegration and low penetration is the intended purpose of the Glaser Safety Slug, and these bullets performed as designed in these tests producing low penetration. The Blue Glaser penetrated one jug and most of the bullet contents (blue tip fragments, copper jacket parts, #12 shot) were found in the second jug. Some #12 shot was found in the first jug. The Silver Glaser penetrated deeper than the Blue. Many of the #6 shot pieces penetrated two jugs. Several pieces of shot were found in the second jug. Twenty holes (or dents with slits) were identified in the back of this jug. No holes were in the front of the third jug.
The CORBON DPX load with the all copper Barnes X bullet penetrated deeper than any of the other bullets tested. It fully penetrated 4 jugs. It expanded completely. In fact, the "petals" of the hex hollow point were bent completely around until they laid along side the body of the bullet.
Federal's light weight and light recoiling 115 grain JHP expanded readily yielding low penetration.
The PMC bullet expanded the least dramatically of all the bullets tested but penetrated more than the other conventional hollow point bullets. The lower velocity of this round might have contributed to its deeper penetration because the lead core did not expand as dramatically as the others and retained much of its weight. The lead core may be harder than some bullets as well, since the Federal 115 grain JHP expanded more and had less penetration.
Wilson Combat's 115 grain all copper TAC-XP showed deep penetration, which is a common feature for the Barnes bullet design, and it looks very similar to the equally similar CORBON125 grain load of the same type. Wilson's loads with conventional bullets, specifically the Hornady XTP hollow points, demonstrated good penetration, expansion and weight retention.
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Table 3: Penetration and Expansion of 38 Super Factory Expanding Bullets
X = complete penetration. S = Stopped inside jug. * Weight in grains. ** The Georgia Arms offering uses the same bullet (Speer Gold Dot) at around the same velocity so the performance should be similar. *** The Double Tap 147 JHP offering uses the same bullet (Speer Gold Dot) at around the same velocity so the performance should be similar. **** The Double Tap 115 TAC-XP offering uses the same bullet at around the same velocity so the performance should be similar. † Velocity in feet per second. Parts refers to the total number of bullet parts recovered. No weight, parts count or core diameter is listed for the Glaser Safety Slugs since they are designed to disintegrate. In some cases the velocity shown in this table varies from that shown in Table 2. In those cases the round fired for this test was individually chronographed.
Disclaimer: For obvious liability reasons I will not make any claims about the generalization of these test results to translate into penetration, expansion or stopping power of these rounds for the purpose of self-defense. Water has a different consistency than actual tissue or ballistic gelatin - the standard media for this type of test. These tests are simply intended to demonstrate general bullet performance. The ultimate selection of any of these cartridges for the purpose of self-defense is left to the reader. My only advice is that the user test the selected ammunition in their gun to make sure that it is safe and will function reliably.
The results of accuracy tests with factory ammunition are listed in Table 4 . First, it's important to make an important point about accuracy tests in general. Accuracy is a product of the gun and the ammunition. Good or bad accuracy can result from the gun itself, the ammunition itself, or a combination of the two. Therefore, the data in Table 4 is, in reality, a reflection of how the specific gun used in the test performed with the ammo tested. The gun was a factory Colt stainless steel Government Model MK IV Series 80 (picture). It has not been accurized. It has the factory Colt barrel. There were no modifications to the gun that would influence accuracy. It's the same gun used for all the information on this page, unless otherwise noted. The gun was tested in a Ransom Rest (picture) that eliminates errors introduced by human factors.
A better way to test accuracy is to use a fully accurized pistol. It is a better test of the ammunition because the gun parts are tightly fit. If the parts critical to accuracy fit close together then they will be in the same position relative to each other every time the gun is fired. This means that the barrel is pointing in the same place every time. Of course, a perfect fit is hard to achieve, and even the tightest gun will loosen up due to normal wear from repeated firing.
The best way to test accuracy is to take the barrel out of the gun and mount the barrel in a special device that holds the barrel in a fixed position. Why is this the best way? Because it gets rid of even the smallest amount of slop that might be in the gun's moving parts that can affect accuracy. Still, even with the barrel all by itself, you're now testing that specific barrel in addition to the ammo. A different barrel might give you different results.
Is this whole accuracy thing a little fuzzy? Yes! And that's how it is in the real world. Different guns (barrels) have preferences. That's why accuracy is a never-ending topic of discussion, and why there is seldom a single correct answer to the question: which is more accurate? That's also why you shouldn't expect the data in Table 4 to be the holy grail of accurate or inaccurate 38 Super ammo.
So, what do the numbers in Table 4 say? The gun did not care for the Armscor, Fiocchi and Frangible Bullets loads very much. And none of the ammunition was super-duper accurate (in that gun!) but some produced groups under 2 inches. By the way, the test gun was not a "tight" gun. It rattled if you shook it. There was slop in the slide to frame fit. The barrel fit reasonably well in the breach region. The bushing fit the barrel well, bit it was loose in the slide. Even with all these minor imperfections the group sizes were a bit better on average than many production pistols reviewed in magazines.
Table 4: Accuracy of 38 Super Factory Ammunition
FMJ = Full Metal Jacket. Fr = Frangible. HP = Hollow Point. JHP = Jacketed Hollow Point. JPRN = Jacketed Polymer Round Nose. Prefrag = Prefragmented. STHP = Silver Tip Hollow Point. TMJ = Total Metal Jacket. XTP = Hornady XTP bullet. * Weight in grains. † Velocity in feet per second. Groups are five shots (§ = 3 shots) fired at a distance of 25 yards from a Ransom Rest. ¥ = Only one group fired due to limited ammunition available at time of testing and the high cost of some of the CORBON specialty loads. Group size measured center-to-center in inches. x Current offering is a flat nosed bullet.
The author has shot a wide range of handloaded ammunition through the test gun and another gun with a Bar-Sto barrel. A clear trend is evident. Both guns (barrels) shoot more accurately with flat nosed bullets than with round nose bullets. Remember, your results may vary.
All fired cases were inspected for signs of pressure. Inspections focused on two factors. Primers and case expansion. First, the primer. Primers are designed to withstand the normal pressures for their intended use. Pistol primers are designed to handle pressures typical of pistol cartridges that run up to 35,000-40,000 psi. Rifle pressures run up to 65,000 psi and rifle primers are made from thicker metal and produce a more intense flame because they have to ignite a larger volume of gunpowder. As you might have guessed, the thinner metal used for pistol primers makes them more sensitive than rifle primers and the firing pin strike in pistols is not as robust as it is in rifles.
The idea behind "reading" the primer is that as pressure exceeds normal limits, the high pressure causes the primer metal itself to flow backwards. Higher pressure produces more primer flow. Inspecting the primer is a common method to watch for signs of “something ain’t right”. That said, watching for pressure signs in the primer is far from an exact science. There can be several reasons for high pressure signs in the primer 1 that don't necessarily mean high pressure. However, it is a reasonable barometer and an indication of something amiss, and if you do see pressure signs here, “something ain’t right” and maybe you shouldn’t be shooting that ammunition, or maybe there’s a problem with the gun.
The results presented here are "readings" of the CORBON ammunition used in the Colt pistol in the velocity, accuracy and expansion tests reported above. Some of this same ammunition was also fired through a Bar-Sto and Nowlin five inch barrel. These same excessive pressure signs were present, suggesting that it was not the gun(s), but the ammo that had the problem.
The Atlanta Arms and Ammo load tested also showed excessive pressure signs. Pierced primers were present in 80% of the rounds fired.
Readers might be interested to know that two test barrels (Colt and Bar-Sto) have a tendency to show different high pressure signs in their primers. In this case, the Bar-Sto barrel shows higher pressure signs than the Colt barrel. In addition, the Bar-Sto barrel produces slightly lower velocity than the Colt barrel (both barrels measure .356). Remember, these pressure signs and velocities apply only to the barrels used in these tests. Your results may vary. There is an important lesson here: different barrels can react differently to pressure with the same ammunition.
Okay, back to the pressure results. The appearance of fired primers under normal pressure conditions looks like a dent in a rounded primer (see examples below). When pressure runs a bit too high, the primer metal starts to flow backward toward the breech face and this affects the appearance of the firing pin strike and surface area of the primer base. These are some of the characteristic appearances of primers when pressure gets high, in order of increasing concern:
The examples shown here of high pressure signs in the primer are all from the high performance CORBON ammo used for the data on this page. The only CORBON loads that did not show high pressure signs were the Match Performance load and the Glaser Silver Safety Slug, the latter having only slight cratering in the primers of half of the rounds fired in spite of amazingly high velocity. But keep in mind that only 5 rounds of the Silver Safety Slugs were fired (and inspected) in these tests and that's a very small sample size for making conclusions about pressure.
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Any abnormal appearance of the primer should be viewed as a danger sign, and the last three signs are warnings of very dangerous pressure levels that can result in damage to the gun, and injury to the shooter and bystanders.
Note: Different brands of primers might start to show pressure signs with less pressure than other brands. I don’t mean to be too fuzzy here, but there is a fuzziness factor involved because of all the issues that affect pressure, such as seating depth, crimp, powder, primer, case capacity, bullet construction, etc. And I should remind readers that using the primer as a guesstimate of pressure is not an exact science. When in doubt, error on the side of caution. If you see high pressure signs, stop using that ammo.
The second test for pressure was to examine the case for an abnormal bulge in the unsupported region. The examples shown below are, once again, from the CORBON ammo used for the data reported above. They were all fired in the standard factory Colt pistol that has a conventional feed ramp. With a conventional feed ramp, not all of the cartridge case is surrounded by the chamber (types of feed ramps and chambers). This is referred to as an unsupported chamber. The cartridge case in this small, exposed (unsupported) region will tolerate only a certain pressure. Cases are made to account for this unsupported region, and as long as pressures do not significantly exceed SAAMI standards, the case should not bulge in the exposed region (at least that’s the working principle). But excessive pressure can result in a significant bulge or rupture of the case where it is not surrounded by the chamber. If the brass has an obvious bulge there, that ammunition is not safe to use in your gun.3 These cases should also not be reloaded.
The Atlanta Arms and Ammo loads were not bulged in this unsupported region, but this is probably due to the fact that they used Starline 38 Super Comp cases, which are well known for their additional strength in this unsupported region.
These figures show examples of case bulge in the unsupported region of 38 Super cases. The cartridges were fired in a factory Colt barrel. The blue arrows in A and B mark the "imprint" of the chamber's feed ramp where the case is not surrounded by the chamber. B' shows a close-up of the bulge in photograph B.
If the unsupported region of the barrel chamber is larger than it should be, either because it came from the factory that way or because of overzealous gunsmithing, the case can bulge or burst even when firing normally safe ammunition. In this situation, the gun (or barrel) is not safe to use. Remember, the 38 Super is a high pressure cartridge (see Technical Specs) and that narrows the margin of error for feed ramp dimensions.
With semi-auto pistols with unsupported chambers, there is a very real risk that the cartridge case can rupture in the unsupported region when the ammunition has extreme pressure. This can cause damage to the gun from fragments of the brass case and hot gases. It’s also possible that the top round(s) in the magazine might go ka-boom since they are sprayed with the case fragments, hot gases and burning gunpowder. The shooter and bystanders risk injury from case fragments, hot gases, burning gunpowder, and any gun parts that go ballistic. If you see excessively bulged cases with your ammunition, its dangerous. Don’t use it. And have a qualified gunsmith check your gun to make sure its not a gun problem.
Note: The author has personally experienced blown cases with high pressure 38 Super ammunition. He was fortunate that he was not hit with any case fragments, but he did have pieces of burnt gunpowder embedding in his face narrowly missing his eyes. This experience is known as "Super Face." The blast of hot gases is very unpleasant, to say the least. Remember To Always Wear Eye Protection When Shooting! No Exceptions!
Published Versus Real Velocity In Your Gun
The velocity that the manufacturer publishes for a given load and what you get from your gun aren’t always the same. If you get higher velocities, you just smile. But if you get lower velocities, then you tend to think that the ammo is not living up to its potential. However, there are many legitimate reasons why your results can vary from what the manufacturer publishes that have nothing to do with faulty ammunition. Some of those are listed here. By the way, the words "velocity" and "pressure" are somewhat interchangeable in the real world of ballistics.
Different Lots of ammo: A different production run (lot) might employ a different gunpowder charge, or different gunpowder. If the manufacturer changes gunpowder, the two powders might not achieve the same velocity at the same pressures. A slight difference in powder charge can exacerbate differences in velocity when combined with other factors listed here.
Some claims of velocity might be exaggerated.
Primers. Changes in primers, by lot or otherwise (standard versus magnum), changes the dynamics of how the gunpowder is ignited and this can change velocity.
Cases. Changes in case volume can also dramatically change velocity and internal pressure.
Crimp. Crimp strength (bullet pull) can change velocity and it could have different effects on different gunpowders.
Ambient Temperature. Generally speaking, warmer temperature translates into higher velocity. I’ve heard rumors of some powders reacting the opposite to this.
Elevation. Elevation might play a role, and some gunpowders might be more prone to this than others. The thought here is that higher elevation results in lower velocity. No doubt some gunpowders will react just the opposite to this just to make things interesting. But I’ve heard some learned people say that elevation doesn’t make a difference.
The bottom line is that you shouldn’t get upset if the velocity reading you get is different from what the manufacturer publishes. Differences happen.
1 Speer Reloading Manual #13. © 1998. Blount Inc. Sporting Equipment Division.
2 The Speer Reloading Manual says that cratered primers are not always a sign of excess pressure. In many cases flattened primers are a gun problem.
3 Sporting Arms and Ammunition Manufacturers Institute, Inc.
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