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Miscellaneous Questions #17

How do  I duplicate US Military ammunition when handloading?
What is a vented test barrel?
What does group placement on a target tell the shooter?
Why does the caliber designation of many cartridges differ from the actual bullet diameter?
Is there issued US military shotgun ammunition?
What is the difference between the "Picatiny" (M1913) mounting rail and the "Weaver" mounts?

Q. How do  I duplicate US Military ammunition when handloading?

A. The following are the specifications for US Small Arms ammunition.  If you have a chronograph you simply load the correct weight bullet to the velocity specified.  If you don't have a chronograph (shame on you!) some suggested loads using military brass and bullets are listed.

ALL LOADS USE MILITARY BRASS (except the 9 mm), AND
  MILITARY BULLETS (OR THEIR COMMERCIAL EQUIVALENT).
REDUCE ALL LOADS BY 10% (EXCEPT THE LOAD MARK BY *) AND WORK UP

Military Ammunition Equivalents

Cartridge

Bullet Weight
(gr)

Velocity
f/s

Suggested load(s)

M41 .38

130

950±45

6.3 gr PowerPistol, 5.2 gr Unique or Universal

M882 9 mm

124

1230±50

6.4 gr Accurate #5, 8 gr BlueDot

M1911 .45ACP

230

820±25

5.2 Bullseye

M193 5.56 mm

55

3250±40

26 gr. of H335, 26.5 gr TAC

M855 5.56 mm [for 5.56 NATO chambers ONLY]

62

3020±40

26 gr of TAC 

MK262 5.56 mm [for 5.56 NATO chambers ONLY]

77

2750±30

24.5 gr TAC

M80 7.62 mm

149

2750±20

42.5 IMR4895, 46 grs. 748 or Ball C2

M118 7.62 mm Special Ball

173

2550±30

43 grs. of RL15 or 748

M118 7.62 mm Special Ball LR (Sierra MK bullet)

175

2580±30

42.5 grs. of Varget,

M852 7.62 mm MATCH (Sierra MK bullet)

168

2550±30

41.5 IMR4895

M2 Cal .30**

150-152

2740±30

49 grs. IMR4895
49 gr 748
50 gr IMR4064

M72 Cal .30 MATCH**

173

2640±30

47 gr IMR 4895
47.5 gr 748
47.5 gr IMR 4064

M1 Cal .30 carbine

110

1900±30

14 gr 2400 or 14 gr H-110*

* Do not reduce H110 more than 3%
** Powders list are the best burning rate for use in the M1 Rifle

One supplier of US surplus components is http://www.gibrass.com

Q. What is a vented test barrel?

A.  Originally ammunition for revolvers was pressure and velocity tested in a solid test barrel just like rifle ammunition but using an 8 7/8" (the longest "common" pistol barrel length) barrel.  This method of testing led to results that showed abnormally high velocities, quite beyond what was usually achievable in an actual revolver with its typical .006" - .008" cylinder gap.  In an attempt to generate more realistic velocity date a vented test barrel is now used for revolver ammunition.  The gap is set to .004" and the barrel length is set to a commonly used length for the caliber under test.  While the .004" gap is a bit unrealistic the results are closer to the real world than with a solid barrel.  Typical differences are shown in the table.

Vented test barrel

 

Test Barrel Differences

 

4" Revolver

4" Vented
test barrel

8.875" Solid
test barrel

158 gr LSWC +P .38Spl

882 f/s

919 f/s

1042 f/s

158 gr JHP .357

1191 f/s

1257 f/s

1453 f/s

Q. What does group placement on a target tell the shooter?

A. The charts below explain the meanings of group placement.  The descriptions given are for right handed shooters.  For left handed shooters flip the drawings left to right.




Q. Why does the caliber designation of many cartridges differ from the actual bullet diameter?

A. The difference comes from the fact that there are two diameters of interest in a barrel.  There is the bore diameter which is measured from the tops of the lands and there is groove diameter which is measures between the deepest part of the grooves.  Depending on the manufacturer's preference the cartridge may be named from either of these dimensions.  In some cases like the .460 Weatherby, which actually used .458" diameter bullets,  the manufacturer my round up the number for advertising purposes.  The actual bullet dimension is based upon the groove measurement.  

In some cartridges (like the ".38 SPL") the designation may refer to an older design of the cartridge.  The common .38 Spl has a bore diameter of .346 and a groove diameter of  .357.  It's designation is based on the original .38 cartridge, the .38 Long Colt (Navy) which used an oversized outside lubricated bullet of about .378" diameter and a slightly larger bore than current cartridges.  And you wonder why the confusion?

The table below gives some common dimensions.

Cartridge

Bore Diameter
(in)

Bore Diameter
(mm)

Groove (Bullet) Diameter
(in)

Groove (Bullet) Diameter
(mm)

.22 RF

.217

5.51

.222

5.64

.22 Centerfire*

.219

5.56

.224

5.68

.243 Win

.237

6.01

.243

6.17

.264 / 6.5 mm

.255

6.47

.264

6.71

.270 Win/6.8

.270

6.85

.277

7.03

7 mm 

.277

7.03

.284

7.21

.30  

.300

7.62

.308

7.82

.32 Win

.315

8.00

.320

8.12

.338 

.330

8.38

.338

8.58

9 mm

.346

8.78

.355

9.01

.38SPL/.357 Mag

.346

8.78

.357

9.06

.40 / 10 mm

.390

9.90

.400

10.16

.41 Mag

.399

10.13

.409

10.38

.44 Magnum

.417

10.59

.429 - .431*

10.90 - 10.94

.45 Colt

.442

11.22

.450 - .454**

11.43 - 11.53

.45 ACP

.442

11.22

.450

11.43

*   Current SAAMI is .429"
** Current SAAMI is .450"
* Includes .22 WMR Rimfire

Q. Is there issued US military shotgun ammunition?

A.  For the most part commercially produced and procured shotgun ammunition is issued.  There are, however, some type classified rounds issued.  The table below lists the one's I am aware of along with the commercial rounds currently listed in the system.

Designation

Identification

M19 

All brass case 00 buckshot

M162

Brass and plastic hi-base 00 buckshot

M257

Brass and plastic hi-base #4 buckshot

M274

Brass and plastic hi-base #4 shot

M1012(AA31)

Finned "less lethal" rubber slug. Clear plastic case marked "Rubber Fin Stabilized Non Lethal."

M1013

18 pellets "less lethal" rubber buck shot   Clear plastic case

AA29

Beanbag round.  Clear plastic case marked "Beanbag-Non Lethal"

AA30

Launcher cartridge.  Clear plastic case marked "Launching cartridge."

M1030

Breaching round.  1.4 oz sintered steel projectile.  Brass hi-base clear plastic case

MK246
Mod 0 (A024)

Breaching round.  Red all plastic cartridge 

M35

.410 21/2 inch commercial loading #6 shot

A023

Brass and plastic hi-base commercial 1 oz Slug

AO14

Brass and plastic low base commercial 71/2 shot

AO17

Brass and plastic low base commercial 9 shot

-

Dummy.  Clear plastic case with blackened hi-base metal.  Marked "Dummy." 

-

10 gauge commercial blank

Currently the US military is issuing Remington 870s, Mossberg 500 & 590s,  Winchester 1100/1200, and the new M1014 HK/Benelli semi-auto

HK/Benelli M1014

Weight:  8.42 lb
Length:  39.8"/34.9'
Barrel length:  18.5"
Sights:  Ghost rings and Stanag M1913 rail
Magazine Capacity (2 3/4"):  7 (plus 1 in chamber and 1 on the carrier)

Q. What is the difference between the "Picatinny" (M1913) mounting rail and the "Weaver" mounts?

A. The so called “Picatinny Rail” is a standardized mounting system for small arms accessories used by NATO and the US military. The term “Picatinny” comes from the Picatinny Arsenal located in New Jersey, who developed the official specification known as MIL-STD-1913 which specifies the dimensions and tolerances required.

The cross sectional profile of the  M1913 and Weaver systems are virtually identical.  

The main difference lies in the placement  and the width of the grooves. M1913 grooves are .206” (5.23 mm) wide and have a center-to-center distance of .394” (10 mm). The placement of these grooves has to be consistent in order for it to be a true “Picatinny” M1913 system. Weaver rails have .180” ( 4.57 mm) recoil grooves and are not necessarily consistent in a center-to-center measurement from one groove to the next.  Frequently, a Weaver system has a specific application that it is machined for, so interchangeability is not necessarily an issue. A MIL-STD-1913 system must adhere to the specifications listed  since the military needs uniformity to allow for different systems to be mounted on the weapon without compatibility concerns. 

Accessories designed for a Weaver system will, in most cases, fit on M1913 rails, but the recoil lug of Weaver type mounts may not fully engage the shoulder of the M1913 rail.  Properly spec'd M1913 accessories probably will not fit most Weaver rails.