455:, are capable of being loaded to far higher levels than was originally possible. Because modern firearms are much stronger than the original black powder era firearms (for example, many guns chambered in .45 Colt are built on the same frame as .41 Magnum and .44 Magnum versions) a combination of modern firearm and specially loaded ammunition can provide performance to rival modern higher pressure cartridges. However, these high-pressure loadings can only be used in modern firearms, because they are produced using higher quality materials and enhanced manufacturing techniques. Because of the potential danger in shooting these "unofficial magnum" cartridges, they are generally only available if
259:"Higher pressure" is not the same as "high pressure"; +P cartridges are generally loaded to pressures far below those typically found in magnum cartridges. The +P standard is designed so that if a shooter were to accidentally use a +P cartridge in a non +P rated firearm, the chance of a one-time explosive failure is minimal as long as the gun was in good physical condition. Repeated firing of +P ammunition in a gun not rated for it will drastically speed mechanical failure of the gun, however, and so it should only be used in firearms designated by the manufacturer as safe for +P use.
207:, along with a significant increase in operating pressure and muzzle energy, making it the most powerful auto pistol cartridge available at the time, in both energy and velocity, until the introduction of the .357 Magnum in 1935. Similar to the "rifle only" loads, the .38 Super could still be chambered in the older .38 ACP guns, therefore producing a dangerous combination. Capable of reaching a muzzle energy of 500 ft⋅lbf (680 J), the .38 Super remains a viable defensive cartridge, though its usage is most commonly found in popular shooting sports such as
248:
not SAAMI standard and may be higher than the +P loading. +P+ ammunition is ammunition that is not held to meet a SAAMI pressure standard. It is usually is loaded to a higher velocity than its +P counterpart and whether that involves a higher peak pressure or not depends on the powder charge used. Some examples have been measured to produce less pressure than +P, while others are be higher than the +P standard pressure. In both cases, pressure is kept below that of a
252:. Proof pressures are established by the SAAMI, as a percentage of the working pressure, so this places an upper bound on the +P+ pressures of 30–40%. By way of comparison, magnum calibers may be loaded to nearly twice the pressure of the rounds from which they were derived. Overpressure rounds are commonly defensive rounds and are loaded by police and others in need of maximum power in a compact firearm. Accordingly, most overpressure rounds are
20:
132:, which is the parent cartridge of lower pressure from which it was derived. +P ammunition, however, is externally identical to standard ammunition of its caliber. It is not an advisable practice to utilize +P ammunition in firearms of questionable quality or in a state of disrepair. In such cases, the margin of safety may be eroded to the extent that hazards or malfunctions will result.
192:; in rifles, such loads provided far more velocity and energy, but in revolvers they were not safe due to the higher chamber pressures that were being generated. These loads were eventually dropped due to a combination of safety concerns, and newer smokeless powder rifle cartridges that offered even higher velocities, such as the
128:, are usually developed by greatly increasing the working pressure of an existing cartridge, and the resulting cartridges are typically different in some small manner to prevent them from being chambered in firearms not specifically designed for them. For example, the .357 Magnum is slightly longer than the
607:
In general, the purpose of a +P cartridge is to get a higher velocity for a given bullet weight than a standard pressure cartridge. However, the pressure rating used to determine if a round is +P is the peak pressure, which is not an accurate indication of the velocity, since it is the area under the
459:
or purchased from low-volume specialty manufacturers. SAAMI specifications may or may not exist for these loads, so extra caution must be used. Generally, the manufacturer or data publisher will specify exactly which makes and/or models of firearm can or cannot be safely used with a given load, such
247:
based on piezoelectric instrumentation. Standard +P pressure limits are established by SAAMI for certain cartridges; in general the +P pressure is approximately 10% higher than the standard pressure (see chart below). SAAMI does not have a +P+ pressure standard, but this indicates a pressure that is
144:
used in early cartridges meant that these cartridges operated at lower chamber pressures, generally under 25,000 psi (170 MPa). These cartridges were limited by their case capacity, and the only way to get more power was to increase the case dimensions to hold more powder; this can be seen
574:
Unless the firearm is explicitly marked as being +P rated or it is clearly stated in the gun's manual, +P ammunition should not be used. If in doubt, a check by a gunsmith or contacting the gun's manufacturer will verify the safety of +P ammunition in a particular firearm. Ammunition that is loaded
483:
In many cases, these loads are not pressure tested, but are tested by firing in particular firearms, then checked for signs of excessive pressure. In some cases, high pressure ammunition is restricted to law enforcement sales, such as
Federal's .38 Special +P+ and 9mm Parabellum +P+ Hydra-Shok
659:
Because of these factors, it is possible to have two loads where each is propelling the same bullet weight at the same velocity, but one is a standard pressure load and one is a +P load. Even in the same firearm, with the same components, cartridges with low powder capacity and high operating
410:
The +P+ designation is not currently used by SAAMI, but is used by some manufacturers to designate loads that exceed the +P SAAMI specifications. One source lists the 9×19mm +P+ loading as having a pressure of 42,000 psi (290 MPa), a 20% increase over the standard pressure of
582:
The use of +P or +P+ ammunition does accelerate wear and reduces the service life on the component parts on any pistol. In addition to questions of safety and durability are issues of reliability and usability. Since +P cartridges may generate a significantly different quality of
595:, the cartridge case may recoil away from the bullet with sufficient force to overcome the crimp, allowing the bullet to move forward in the cylinder and causing the cylinder to bind. The increased velocities and pressures of a +P loading will increase
418:
load from
Buffalo Bore Ammunition. These loads are generally designed to provide maximum performance from older cartridges, when used in newer, stronger firearms. The 14,000 psi (97 MPa) limit for .45 Colt, for example, reflects the original
435:, the pressure can be pushed far higher with no ill effects. However, since these loads, with nearly double the chamber pressure, could destroy a firearm intended for use with black powder level loads, although they are less commonly encountered.
664:, have been shown to have a significant increase in pressure with very minor differences in bullet seating depth. One example in .40 S&W demonstrated a 20% pressure increase with a 0.05 inch (1.2 mm) change in seating depth.
882:
291:
and quality since the first guns in those calibers have been made, with the result that higher pressures are now safe in modern firearms. Many models will specify the degree to which they can use +P ammunition; for example, many
907:
299:
framed .38 Special revolvers should not regularly be used with +P ammunition, for while the cylinder is capable of withstanding the pressures, the added force will increase wear and reduce the service life of the gun.
203:, originally introduced in 1900. This cartridge provided performance similar to other .38 caliber cartridges of the time. However, in 1929 the cartridge was redesigned as the .38 Super Automatic or
889:
914:
411:
35,000 psi (240 MPa), and the .38 Special +P+ as 22,000 psi (150 MPa), a 25.71% increase over the standard pressure of 17,500 psi (121 MPa).
164:, which has a far greater energy density than black powder, it was possible to generate far more power in the large cases of the older black-powder cartridges such as the
865:
236:
839:
188:. The rifle actions could handle much higher pressures, than their revolver counterparts. This led to so-called "machine gun only" loads in these
599:
and recoil, and may prove difficult to handle for many shooters; these problems are exacerbated by compact, lightweight guns with short barrels.
208:
423:
performance of the round, and is safe even in firearms built in 1873, when the cartridge was introduced. Using modern, solid head brass in a
1005:
154:
199:
The first modern smokeless powder cartridge deliberately loaded by a major manufacturer to higher than standard pressure was the
1011:
414:
Small ammunition makers and reloading guides will often include special loads for specific purposes, such as the below listed
683:
287:
which are all cartridges that date from the late 19th and the early 20th century. There has been significant improvement in
862:
484:
cartridges. The following table lists some non-SAAMI +P loads for which the manufacturer publishes pressure information.
931:
219:
High
Velocity, which was manufactured from 1930 to 1966; which eventually lead to the development and production of the
965:
146:
736:
1031:
678:
846:
61:
that has been loaded to produce a higher internal pressure when fired than is standard for ammunition of its
515:
20.83% increase, Garrett
Cartridge, Ruger and Dan Wesson DA revolvers, long-frame single action conversions
753:
673:
703:
463:
121:
240:
591:
firearms may fail to function if the velocity of the recoiling parts is too high; in lightweight
244:
181:
8:
1026:
609:
563:
42.86% increase, Accurate Powder loading manual, Ruger and similar high strength actions
253:
66:
239:(SAAMI), which publishes standard internal pressures of calibers, formerly measured in
185:
732:
193:
177:
173:
169:
165:
110:
981:
547:
25.00% increase, Garrett
Cartridge, modern rifles including lever and break actions
646:
588:
161:
969:
869:
424:
90:
86:
74:
962:
818:
70:
771:
323:
268:
235:, standards related to arms and ammunition are maintained and published by the
106:
82:
612:). A large number of factors can impact the peak pressure of a load, such as:
1020:
938:
232:
78:
792:
608:
pressure curve that determines the total energy imparted to the bullet (see
596:
444:
420:
393:
284:
141:
102:
982:"How do changing various components affect chamber pressure and velocity?"
475:
456:
339:
272:
220:
212:
129:
125:
661:
504:
432:
428:
288:
249:
58:
55:
576:
427:
revolver, a similar design originally chambered in the high pressure
211:. A similar move in creating a high pressure loading was done on the
204:
531:
67.86% increase, Accurate Powder loading manual, Ruger and T/C only
592:
520:
448:
415:
293:
149:, which made rifles with nominal powder capacities from 70 grains (
28:
24:
726:
376:
371:
355:
280:
276:
200:
189:
98:
94:
62:
19:
579:
as such, for example a 9mm would be marked "9mm
Parabellum +P".
438:
267:
Cartridges that are commonly improved with +P pressures are the
584:
552:
536:
452:
216:
150:
97:
purposes. Because of this, +P ammunition is typically found in
470:"Use only in modern Marlin and Winchester lever-action rifles"
303:
SAAMI specifications for common +P cartridges are as follows:
443:
Some older cartridges, especially those that were originally
296:
73:. This is done typically to produce ammunition with higher
262:
237:
Sporting Arms and
Ammunition Manufacturers' Institute
754:".38-44 HV: The Original Magnum - revolver round"
587:, this can affect firearm function. For example,
1018:
69:), but less than the pressures generated by a
602:
439:Custom and handloaded overpressure cartridges
751:
905:
880:
172:. Some black powder cartridges such as the
116:
727:Frank C. Barnes, ed. Stan Skinner (2003).
813:
811:
809:
575:to +P pressures is clearly marked on the
722:
720:
256:or other types of expanding ammunition.
18:
1019:
963:"Titanium Taurus" in Small Arms Review
806:
772:"How are proof pressures determined?"
717:
684:Table of handgun and rifle cartridges
840:"Condensed Load Guide Version 3.2.2"
569:
447:cartridges such as the 1873-vintage
263:Commercially available +P cartridges
13:
147:Sharps Rifle Manufacturing Company
145:in firearms such as those made by
14:
1043:
999:
883:".45 Colt (Ruger & T/C only)"
845:. Accurate Powder. Archived from
101:calibers which might be used for
793:"What is +P and +P+ ammunition?"
729:Cartridges of the World, 10th Ed
974:
956:
924:
899:
560:40,000 psi (280 MPa)
557:28,000 psi (190 MPa)
544:35,000 psi (240 MPa)
541:28,000 psi (190 MPa)
528:23,500 psi (162 MPa)
512:43,500 psi (300 MPa)
509:36,000 psi (250 MPa)
401:58,000 psi (400 MPa)
398:54,000 psi (370 MPa)
385:36,500 psi (252 MPa)
382:26,500 psi (183 MPa)
363:23,000 psi (160 MPa)
360:21,000 psi (140 MPa)
347:20,000 psi (140 MPa)
344:17,000 psi (120 MPa)
331:38,500 psi (265 MPa)
328:35,000 psi (240 MPa)
140:The burning characteristics of
874:
856:
832:
785:
764:
745:
696:
679:List of rebated rim cartridges
525:14,000 psi (97 MPa)
85:, such as ammunition used for
1:
689:
16:Type of small arms ammunition
226:
7:
704:"The Shiloh Sharps .45-110"
667:
462:"Only for use in Ruger and
10:
1048:
674:List of handgun cartridges
603:+P ammunition and velocity
464:Thompson/Center Contenders
135:
932:"HK USP Operators Manual"
752:Chuck Taylor (May 2000).
634:Test barrel chamber shape
38:, commonly designated as
493:Standard pressure (psi)
312:Standard pressure (psi)
241:copper units of pressure
124:cartridges, such as the
117:+P vs. magnum cartridges
1032:Paramilitary cartridges
731:. Krause Publications.
660:pressures, such as the
215:in 1930, producing the
182:single-action revolvers
180:were chambered in both
36:Overpressure ammunition
908:".45-70 High Pressure"
32:
863:Hydra-Shok ballistics
655:Cartridge case volume
22:
1012:SAAMI pressure chart
631:Test barrel diameter
628:Bullet seating depth
480:single-shot rifles.
250:proof test cartridge
1008:, Handguns Magazine
819:"Garrett Cartridge"
610:internal ballistics
186:lever-action rifles
160:With the advent of
103:paramilitary forces
67:internal ballistics
968:2007-01-30 at the
868:2007-02-24 at the
496:+P pressure (psi)
315:+P pressure (psi)
111:defensive purposes
33:
906:Accurate Powder.
881:Accurate Powder.
570:+P ammunition use
567:
566:
408:
407:
243:and currently in
194:.30-30 Winchester
178:.44-40 Winchester
174:.32-20 Winchester
170:.38-55 Winchester
166:.32-40 Winchester
153:) to 110 grains (
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993:
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944:on 13 April 2004
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937:. Archived from
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913:. Archived from
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888:. Archived from
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647:Smokeless powder
640:Friction in bore
487:
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478:and Ruger No. 3"
388:37.74% increase
350:17.65% increase
334:10.00% increase
306:
305:
162:smokeless powder
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1006:Demystifying +P
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970:Wayback Machine
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652:Primer strength
637:Bullet hardness
625:Bullet diameter
619:Bullet material
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589:recoil operated
572:
441:
425:Ruger Blackhawk
404:7.41% increase
366:9.52% increase
265:
229:
138:
119:
75:muzzle velocity
27:124gr 9mm+P in
17:
12:
11:
5:
1045:
1035:
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1001:
1000:External links
998:
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923:
920:on 2007-09-30.
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895:on 2008-11-20.
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852:on 2008-05-16.
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21:
985:. Retrieved
976:
958:
946:. Retrieved
939:the original
926:
915:the original
901:
890:the original
876:
858:
847:the original
834:
822:. Retrieved
796:. Retrieved
787:
775:. Retrieved
766:
757:
747:
728:
707:. Retrieved
698:
658:
622:Bullet shape
606:
597:muzzle blast
581:
573:
482:
473:
469:
461:
445:black-powder
442:
421:black powder
413:
409:
394:.257 Roberts
375:
302:
285:.257 Roberts
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258:
230:
198:
159:
142:black powder
139:
120:
51:
47:
46:(pronounced
43:
39:
35:
34:
662:.40 S&W
476:Ruger No. 1
377:38 Super +P
340:.38 Special
273:.38 Special
221:.357 Magnum
213:.38 Special
130:.38 Special
126:.357 Magnum
71:proof round
52:Plus-P-Plus
1027:Ammunition
1021:Categories
690:References
505:.44 Magnum
490:Cartridge
457:handloaded
433:.44 Magnum
429:.41 Magnum
309:Cartridge
289:metallurgy
59:ammunition
56:small arms
987:2 October
948:2 October
824:2 October
798:2 October
777:2 October
709:2 October
649:burn rate
593:revolvers
577:headstamp
227:Standards
223:in 1935.
205:.38 Super
91:defensive
31:magazines
966:Archived
866:Archived
668:See also
521:.45 Colt
449:.45 Colt
416:.45 Colt
294:aluminum
190:calibers
87:security
29:SIG P226
25:Gold Dot
372:.38 ACP
356:.45 ACP
281:.38 ACP
277:.45 ACP
231:In the
201:.38 ACP
155:.45-110
136:History
99:handgun
95:hunting
63:caliber
735:
585:recoil
553:.45-70
537:.45-70
499:Notes
472:or in
453:.45-70
318:Notes
283:, and
217:.38-44
151:.45-70
122:Magnum
109:, and
81:, and
54:), is
48:Plus-P
23:Speer
942:(PDF)
935:(PDF)
918:(PDF)
911:(PDF)
893:(PDF)
886:(PDF)
850:(PDF)
843:(PDF)
297:alloy
93:, or
65:(see
989:2014
950:2014
826:2014
800:2014
779:2014
733:ISBN
711:2014
451:and
431:and
209:IPSC
184:and
176:and
168:and
460:as
245:psi
157:).
50:or
44:+P+
42:or
1023::
808:^
756:.
719:^
468:,
374:/
279:,
275:,
271:,
196:.
113:.
105:,
89:,
77:,
40:+P
991:.
952:.
828:.
802:.
781:.
760:.
741:.
713:.
474:"
466:"
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