55gr vs 62gr

[thegoat273]

I was wondering, what is the difference between 55gr and 62gr? I was on gun deals.com and checking prices and came across some deals, but it was 62gr. Other than being a heavier round. I have a 1:7 twist rifle. Thanks

[wahoo95]

55gr weighs 55 grains and the 62gr weighs 62 grains....the is the difference. Your barrel should shoot either just fine.

[TehLlama]

A 1:7 barrel will shoot both just fine.

Accuracy and terminal effectiveness are determined more by bullet construction, and POI are going to be different even amongst bullets of the same weight.

That said, don't be dissuaded on an ammo purchase just from the bullet weight if it's just for range and training use. The quality of the brass, a pressure of the load itself will make a much bigger difference in how it runs through your rifle(s)

[Molon]

clone: one that appears to be a copy of an original form.

Genuine 55 grain M193 must be tested for and pass all of the specifications laid out in the mil-spec, MIL-C-9963. The required areas of testing included in MIL-C-9963 range from velocity, accuracy, chamber pressure and port pressure to waterproofing, temperature stability, bullet extraction, case hardness, fouling and more.

Genuine US Military M193 can no longer be sold to civilians, thanks to the Clinton Administration. The ammunition that is sold on the commercial market with some form of “M193” in its nomenclature is often referred to as an “M193 clone” because it “appears to be a copy” of genuine M193, but we generally have no idea what specifications of MIL-C-9963 that this ammunition has passed, or has even been tested for.

M193 is loaded with a 55 grain FMJ bullet with a cannelure. The bullet itself, must meet required specifications to be used in genuine M193. For example, the specification for the thickness of the gilding metal jacket of the bullet is 0.021" with a tolerance of - 0.002". For comparison, the jacket of Hornady’s 55 grain FMJ bullet has a thickness of approximately 0.028”. Jacket thickness can have a significant effect on terminal ballistic properties, particularly that of fragmentation. Even the composition of the copper alloy used for the jacket and the lead used for the slug must meet mil-spec requirements for genuine M193.

Genuine US Military M193 can only be charged with powder that has been specifically approved by the US Military for use in this cartridge. If the ammunition in question is not loaded with one of the approved powders, it is not genuine M193 and naturally we have no way of determining what powder was used in a load simply by visual inspection.

Genuine M193 will have the annealing iris visible on the shoulder and neck portion of the case. It will also will have crimped and sealed primers. Genuine M193 has a crimped case mouth along with sealant at the case mouth.


The velocity specification for M193 as cited in MIL-C-9963F states:

The average velocity of the sample cartridges, conditioned at 72 degrees, plus or minus 2 degrees Fahrenheit (F), shall be 3165 feet per second (ft/sec), plus or minus 40 ft/sec, at 78 feet from the muzzle of the weapon. The standard deviation of the velocities shall not exceed 40 ft/sec.

The specification is for a 20” barrel. Depending on multiple variables, this velocity specification equates to a muzzle velocity of approximately 3270 ft/sec, plus or minus 40 ft/sec.

I chronographed four different M193 clones back-to-back for comparison. All four of these loads are currently available on the commercial market (at the time of this writing). These loads were fired from a semi-automatic AR-15 with a chrome-lined, NATO chambered 20” Colt M16A2 barrel. The four loads are listed below:

IMI M193
American Eagle Tactical M193
Privi Partizan (PPU) M193
Winchester Q3131A1.











M16A2 barrel.



Chronographing of the M193 clones was conducted using an Oehler 35-P chronograph with “proof screen” technology. All velocities listed below are muzzle velocities as calculated from the instrumental velocities using Oehler’s Ballistic Explorer software program. All strings of fire consisted of 10 rounds each.









Each round was single-loaded and cycled into the chamber from a magazine fitted with a single-load follower. The bolt locked-back after each shot allowing the chamber to cool in between each shot. This technique was used to mitigate the possible influence of “chamber-soak” on velocity data. Each new shot was fired in a consistent manner after hitting the bolt release. Atmospheric conditions were monitored and recorded using a Kestrel 4000 Pocket Weather Tracker.





Atmospheric conditions.

Temperature: 79 degrees F
Humidity: 42%
Barometric pressure: 30.19 inches of Hg
Elevation: 950 feet above sea level





Continued in the next post . . .

[Molon]

The accuracy specification for M193 cited in MIL-C-9963F is as follows:

The average of the mean radii of all targets of the sample cartridges, fired at 200 yards, shall not exceed 2.0 inches.

These averages are from 10-shot groups fired from machine rested, bolt-actioned test barrels, such as the ones pictured below. All things being equal (which of course they seldom are) this specification equates to a mean radius of 1 inch at 100 yards.

(For those of you not familiar with the mean radius, see post #4 below.)








I conducted an accuracy (technically, precision) evaluation of the same four M193 clones that were chronographed above, following my usual protocols. This accuracy evaluation used statistically significant shot-group sizes and every single shot in a fired group was included in the measurements. There was absolutely no use of any Group Reduction Techniques (e.g. fliers, target movement, Butterfly Shots). The shooting set-up will be described in detail below. As many of the significant variables as was practicable were controlled for. Pictures of the fired shot-groups will be posted for documentation.


All shooting was conducted from a concrete bench-rest from a distance of 100 yards (confirmed with a laser rangefinder.) The barrel used in the evaluation was free-floated. The free-float handguards of the rifle rested in a Sinclair Windage Benchrest, while the stock of the rifle rested in a Protektor bunny-ear rear bag. Sighting was accomplished via a Leupold VARI-X III set at 25X magnification and adjusted to be parallax-free at 100 yards. A mirage shade was attached to the objective-bell of the scope. Wind conditions on the shooting range were continuously monitored using a Wind Probe. The set-up was very similar to that pictured below.






The Wind Probe.





The test vehicle for this evaluation was a 16” Colt HBAR with chrome lining, a NATO chamber and a 1:9” twist. This is the barrel found on the Colt 6721 carbine. This barrel was free-floated with a 10” LaRue free-float handguard. I specifically choose to evaluate the accuracy of this ammunition using an AR-15 with a chrome-lined, NATO chambered barrel, as this is the type of barrel that is most commonly used to fire this type of ammunition.

It is possible to obtain better accuracy with mil-spec/NATO pressure loads when fired from an AR-15 that has a stainless steel match-grade barrel with a hybrid chamber such as the Noveske NMmod0 chamber or the Wylde chamber for examples. You're not going to make a silk purse out of a sow’s ear doing this, but I’ve previously experienced up to a 20% improvement in accuracy by doing so.












The 16” Colt HBAR is one of the most accurate “off the shelf” chrome-lined, NATO chambered AR-15 barrels that I’ve evaluated. Three 10-shot groups fired from this barrel from a distance of 100 yards using match-grade hand-loads topped with Sierra 52 grain MatchKings had extreme spreads of:


0.85”
1.14”
0.88”

for a 10-shot group average extreme spread of 0.96”. Over-laying the three 10-shot groups on each other using RSI Shooting Lab software produced a 30-shot composite target with a mean radius of 0.32”.




IMI M193





Three 10-shot groups of the IMI M193 were fired in a row from a distance of 100 yards from the Colt 16” HBAR. Those three groups had extreme spreads of:

2.83”
2.77”
2.80”

for a 10-shot group average extreme spread of 2.80”. The three 10-shot groups were over-layed on each other using RSI Shooting Lab to form a 30-shot composite group. The composite group had a mean radius of 0.97”.


The smallest 10-shot group.






The 30-shot composite group.







American Eagle Tactical XM193




Three 10-shot groups of the American Eagle Tactical XM193 fired in a row had extreme spreads of:

3.01”
3.25”
3.57”

For a 10-shot group average of 3.27”. The 30-shot composite group had a mean radius of 0.98”.


The smallest 10-shot group.





The 30-shot composite group.







Prvi Partizan M193



Three 10-shot groups of the Priv Partizan M193 were fired in a row from a distance of 100 yards. The groups had extreme spreads of:

2.72”
3.89”
3.74”

for a 10-shot group average extreme spread of 3.45”. All three of these groups were over-layed on each other using RSI Shooting Lab to form a 30-shot composite group. The mean radius for the composite group was 1.01”.


The smallest 10-shot group of PPU M193





The 30-shot composite group.






Winchester Q3131A1





Three 10-shot groups of the Winchester Q3131A1 load were fired in a row. The extreme spreads of those groups measured:

2.95”
3.73”
3.35”

for a 10-shot average extreme spread of 3.34”. The three 10-shot groups were over-layed on each other using RSI Shooting Lab to form a 30-shot composite group. The mean radius for the composite group was 1.05”.


The smallest 10-shot group.





The 30-shot composite group.







Here is a summary of the results of the accuracy evaluation of the four M193 clones.










1:7" twist versus 1:9" twist with 55 grain FMJ Ammunition

Using the Prvi M193 ammunition, I did an accuracy comparison firing the 55 grain FMJ load from both a 1:9” twist Colt HBAR and a 1:7” twist Colt HBAR. Four 10-shot groups were fired from each barrel from a bench-rest at a distance of 100 yards. The groups from each barrel were over-layed to form 40-shot composite groups. The mean radii of the composite groups were nearly identical.

[Molon]

Attack of the (M193) Clones, Part Two: M855 Comparison






In the first installment of Attack of the (M193) Clones, we examined the velocity and accuracy (technically precision) of four different M193 clones currently available on the commercial market. In part two, we’ll be examining the velocity and accuracy of four different 62 grain M855 clones currently available on the commercial market. The M855 clones examined for this article are shown below.

IMI M855





Winchester Ranger M855






Prvi Partizan M855





American Eagle XM855






The obvious difference between the projectiles used in M855 and M193 clones is the weight difference of 7 grains, 62 grains versus 55 grains. The M855 projectile has a FMJ construction but also has a steel “penetrator” in the ogive section of the bullet. This makes the projectile unusually long for its weight, as well as giving it a lower specific gravity. Most, but not all, of the M855 clones have the tip of the bullet painted green.

62 grain M855 projectile versus 55 grain M193 projectile.





The 62 grain M855 projectile is actually longer than the heavier 69 grain Sierra MatchKing.





Note the steel penetrator in the sectioned projectile below.





Chronographing of the M855 clones was conducted as described in part one, using the same 20” M16A2 barrel. The results are shown in the table below.





Accuracy testing of the M855 clones was also conducted exactly as described in part one, using the same free-floated 16” Colt HBAR fired from my bench-rest set-up at 100 yards. As previously stated, I chose a chrome lined, NATO chambered barrel as the accuracy test vehicle as this is the type of barrel that these clone loads are most likely to be fired from. It is possible to obtain better accuracy from mil-spec/NATO pressure loads by firing them from an AR-15 that has a stainless steel match-grade barrel with a hybrid chamber such as the Noveske NMmod0 chamber or the Wylde chamber for examples. You're not going to make a silk purse out of a sow’s ear doing this, but I’ve previously experienced up to a 20% improvement in accuracy by doing so.

Three 10-shot groups of each load were fired in a row with the results shown in the table below.






Here are the previous accuracy results of the M193 clones along with the M855 clone results for comparison.






…..

[hotrodder636]

Not replying for the sake of argument, but if you are saying that "clones" are the only thing that can be sold to civilians, then what kind of Ammo is Palmetto State Armory selling? To my understanding Lake City 5.56 was true .mil?
I believe this to be true for both the M855 and XM193...

[wahoo95]

Not replying for the sake of argument, but if you are saying that "clones" are the only thing that can be sold to civilians, then what kind of Ammo is Palmetto State Armory selling? To my understanding Lake City 5.56 was true .mil?
I believe this to be true for both the M855 and XM193...

There is M193 and then there is XM193(clone).

[Pappabear]

Hey Molon, if you don't have anything signifigant
to offer, no need to respond. Just kidding obviously. Outstanding post as usual.

Pretty interesting to see how most of that 5.56 opens up pretty good at 100 yards. That sure makes those 500 yard shots for the boys in uniform, pretty challenging.

Thanks for sharing.

[900ss]

Great post. I have been shooting the IMI lately - it is good stuff.