Molon
7 July 2016, 14:36
An Accuracy Comparison
of
Three Different Barrel/Ammunition Combinations
For this article, I compared the accuracy (technically, precision) of three different barrel/ammunition combinations. The three different AR-15 barrel/ammunition combinations tested are as follows:
Lothar Walther barrel / GECO 223 Remington 55 grain FMJ Target
Lothar Walther barrel / GECO 5.56x45mm 55 grain FMJ
Colt 16 HBAR / Wolf Performance 223 Remington 62 grain FMJ
The same 20 Lothar Walther barrel was used to test the two different GECO loads. This stainless-steel barrel has a 223 Wylde chamber and a 1:8 twist.
https://app.box.com/shared/static/54r3ei5eya6fzsli811me0ipfvslbaxk.jpg
The 16 Colt HBAR used to fire the Wolf 62 grain FMJ ammunition is chrome-lined and has a 5.56mm NATO chamber with a 1:9 twist. This is the same barrel found on the Colt 6721.
https://app.box.com/shared/static/ldec74m0sy.jpg
All of the shooting for this article was conducted using my AR-15 bench-rest set-up. The shooting set-up will be described in detail below. As many of the significant variables as was practicable were controlled for.
Shooting was conducted from a concrete bench-rest from a distance of 100 yards (confirmed with a laser rangefinder.) The barrels used in the evaluations are free-floated. The free-float handguard of the rifle rests in a Sinclair Windage Benchrest with the aid of a forend adaptor, while the stock of the rifle rests in a Protektor bunny-ear rear bag.
The same AR-15 lower was used to test all three of the different barrel/ammunition combinations. The lower houses a Geissele Hi-Speed National Match trigger.
Sighting is accomplished via a Leupold VAR-X III set at a magnification of 25X and adjusted to be parallax-free at 100 yards. A mirage shield is attached to the objective-bell of the scope. Wind conditions on the shooting range are continuously monitored using a Wind Probe. The set-up is very similar to that pictured below.
http://www.box.net/shared/static/knb2dg3c2f.jpg
https://app.box.com/shared/static/tvj4g3ak8fvppyw3s4lh85u46eukazqt.jpg
The Wind Probe.
http://www.box.net/shared/static/lkg47ptc04.jpg
Atmospheric conditions on the range are monitored and recorded using a Kestrel 4000 Pocket Weather Tracker.
https://app.box.com/shared/static/rwruh372al3yh9kafscx370ewe74e6el.jpg
Prior to shooting the factory loaded ammunition, control groups were fired using match-grade hand-loads. The radial dispersion of the control groups was significantly smaller than that of the factory loaded ammunition.
...
https://app.box.com/shared/static/g1escg6rhvct33wjd5ygqg2aovexrxc4.jpg
A 3-shot group of the GECO 223 Remington 55 grain FMJ Target ammunition was fired from the Lothar Walther barrel at a distance of 100 yards. This group had an extreme spread of 0.47
https://app.box.com/shared/static/4bva0mnkcyfoiv8gum0d6erhzqpbkffr.jpg
...
https://app.box.com/shared/static/xzk3z5wee95pu0tah3aw03skj87sv55c.jpg
A 3-shot group of the GECO 5.56x45mm 55 grain FMJ ammunition was fired from the Lothar Walther barrel at a distance of 100 yards. This group had an extreme spread of 0.46
https://app.box.com/shared/static/ok6obia5zolm8j88vaf26awragfcutek.jpg
...
https://app.box.com/shared/static/qvb9qst822zadmbucx47x2rfib2iwsh5.jpg
A 3-shot group of the steel-cased, bi-metal jacketed, Wolf Performance 62 grain FMJ ammunition was fired from the Colt 16 HBAR (6721) barrel at a distance of 100 yards. This group had an extreme spread of 0.47
https://app.box.com/shared/static/guq10u19tdwwcecodoc5yabw7n8plzrn.jpg
Part Two
Looking at the 3-shot groups above, you might be misled into believing that the precision of the three different barrel/ammunition combinations is virtually identical. However, according to ballistipedia.com, the use of 3-shot groups for evaluating precision is statistically almost meaningless.
http://ballistipedia.com/index.php?title=Describing_Precision
Now, if instead of using statistically almost meaningless 3-shot groups, we follow the practice of the US Army Marksmanship Unit for evaluating the precision of AR-15 barrel/ammunition combinations and shoot three consecutive 10-shot groups, a much different picture emerges when comparing the precision of the three different barrel/ammunition combinations being evaluated; particularly if we over-lay the three 10-shot groups on each other to form a 30-shot composite group and use the more statistically powerful mean radius to compare the radial dispersion of the three different barrel/ammunition combinations.
Three 10-shot groups of the GECO 223 Remington 55 grain FMJ Target ammunition fired in a row from a distance of 100 yards from the Lothar Walther barrel produced the following extreme spreads:
1.71
1.06
1.52
for a 10-shot group average extreme spread of 1.43. 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 30-shot composite group was 0.47.
Three 10-shot groups of the GECO 5.56x45mm 55 grain FMJ ammunition fired in a row from a distance of 100 yards from the Lothar Walther barrel produced the following extreme spreads:
2.55
2.09
2.19
for a 10-shot group average extreme spread of 2.28. 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 30-shot composite group was 0.79.
Three 10-shot groups of the Wolf 62 grain FMJ ammunition fired in a row from a distance of 100 yards from the Colt 6721 barrel produced the following extreme spread:
4.23
4.29
3.68
for a 10-shot group average extreme spread of 4.07. 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 30-shot composite groups was 1.22.
The 30-shot composite groups . . .
https://app.box.com/shared/static/i9evbzr8ak4jga5isgsos6e43owx5to7.jpg
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The 10-shot control group fired from the Lother Walther barrel for the GECO 223 Remington 55 grain FMJ Target ammunition test . . .
https://app.box.com/shared/static/onjbshrleutycfklxr0xmp4cq56fff75.jpg
The 10-shot control group fired from the Lothar Walther barrel for the GECO 5.56x45mm 55 grain FMJ ammunition test . . .
https://app.box.com/shared/static/yyv78cwx0hyk7kxvgvxwz2c4yvem56o3.jpg
The 10-shot control group fired from the Colt 6721 barrel for the Wolf Performance 62 grain FMJ ammunition testing had an extreme spread of 0.89.
....
of
Three Different Barrel/Ammunition Combinations
For this article, I compared the accuracy (technically, precision) of three different barrel/ammunition combinations. The three different AR-15 barrel/ammunition combinations tested are as follows:
Lothar Walther barrel / GECO 223 Remington 55 grain FMJ Target
Lothar Walther barrel / GECO 5.56x45mm 55 grain FMJ
Colt 16 HBAR / Wolf Performance 223 Remington 62 grain FMJ
The same 20 Lothar Walther barrel was used to test the two different GECO loads. This stainless-steel barrel has a 223 Wylde chamber and a 1:8 twist.
https://app.box.com/shared/static/54r3ei5eya6fzsli811me0ipfvslbaxk.jpg
The 16 Colt HBAR used to fire the Wolf 62 grain FMJ ammunition is chrome-lined and has a 5.56mm NATO chamber with a 1:9 twist. This is the same barrel found on the Colt 6721.
https://app.box.com/shared/static/ldec74m0sy.jpg
All of the shooting for this article was conducted using my AR-15 bench-rest set-up. The shooting set-up will be described in detail below. As many of the significant variables as was practicable were controlled for.
Shooting was conducted from a concrete bench-rest from a distance of 100 yards (confirmed with a laser rangefinder.) The barrels used in the evaluations are free-floated. The free-float handguard of the rifle rests in a Sinclair Windage Benchrest with the aid of a forend adaptor, while the stock of the rifle rests in a Protektor bunny-ear rear bag.
The same AR-15 lower was used to test all three of the different barrel/ammunition combinations. The lower houses a Geissele Hi-Speed National Match trigger.
Sighting is accomplished via a Leupold VAR-X III set at a magnification of 25X and adjusted to be parallax-free at 100 yards. A mirage shield is attached to the objective-bell of the scope. Wind conditions on the shooting range are continuously monitored using a Wind Probe. The set-up is very similar to that pictured below.
http://www.box.net/shared/static/knb2dg3c2f.jpg
https://app.box.com/shared/static/tvj4g3ak8fvppyw3s4lh85u46eukazqt.jpg
The Wind Probe.
http://www.box.net/shared/static/lkg47ptc04.jpg
Atmospheric conditions on the range are monitored and recorded using a Kestrel 4000 Pocket Weather Tracker.
https://app.box.com/shared/static/rwruh372al3yh9kafscx370ewe74e6el.jpg
Prior to shooting the factory loaded ammunition, control groups were fired using match-grade hand-loads. The radial dispersion of the control groups was significantly smaller than that of the factory loaded ammunition.
...
https://app.box.com/shared/static/g1escg6rhvct33wjd5ygqg2aovexrxc4.jpg
A 3-shot group of the GECO 223 Remington 55 grain FMJ Target ammunition was fired from the Lothar Walther barrel at a distance of 100 yards. This group had an extreme spread of 0.47
https://app.box.com/shared/static/4bva0mnkcyfoiv8gum0d6erhzqpbkffr.jpg
...
https://app.box.com/shared/static/xzk3z5wee95pu0tah3aw03skj87sv55c.jpg
A 3-shot group of the GECO 5.56x45mm 55 grain FMJ ammunition was fired from the Lothar Walther barrel at a distance of 100 yards. This group had an extreme spread of 0.46
https://app.box.com/shared/static/ok6obia5zolm8j88vaf26awragfcutek.jpg
...
https://app.box.com/shared/static/qvb9qst822zadmbucx47x2rfib2iwsh5.jpg
A 3-shot group of the steel-cased, bi-metal jacketed, Wolf Performance 62 grain FMJ ammunition was fired from the Colt 16 HBAR (6721) barrel at a distance of 100 yards. This group had an extreme spread of 0.47
https://app.box.com/shared/static/guq10u19tdwwcecodoc5yabw7n8plzrn.jpg
Part Two
Looking at the 3-shot groups above, you might be misled into believing that the precision of the three different barrel/ammunition combinations is virtually identical. However, according to ballistipedia.com, the use of 3-shot groups for evaluating precision is statistically almost meaningless.
http://ballistipedia.com/index.php?title=Describing_Precision
Now, if instead of using statistically almost meaningless 3-shot groups, we follow the practice of the US Army Marksmanship Unit for evaluating the precision of AR-15 barrel/ammunition combinations and shoot three consecutive 10-shot groups, a much different picture emerges when comparing the precision of the three different barrel/ammunition combinations being evaluated; particularly if we over-lay the three 10-shot groups on each other to form a 30-shot composite group and use the more statistically powerful mean radius to compare the radial dispersion of the three different barrel/ammunition combinations.
Three 10-shot groups of the GECO 223 Remington 55 grain FMJ Target ammunition fired in a row from a distance of 100 yards from the Lothar Walther barrel produced the following extreme spreads:
1.71
1.06
1.52
for a 10-shot group average extreme spread of 1.43. 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 30-shot composite group was 0.47.
Three 10-shot groups of the GECO 5.56x45mm 55 grain FMJ ammunition fired in a row from a distance of 100 yards from the Lothar Walther barrel produced the following extreme spreads:
2.55
2.09
2.19
for a 10-shot group average extreme spread of 2.28. 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 30-shot composite group was 0.79.
Three 10-shot groups of the Wolf 62 grain FMJ ammunition fired in a row from a distance of 100 yards from the Colt 6721 barrel produced the following extreme spread:
4.23
4.29
3.68
for a 10-shot group average extreme spread of 4.07. 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 30-shot composite groups was 1.22.
The 30-shot composite groups . . .
https://app.box.com/shared/static/i9evbzr8ak4jga5isgsos6e43owx5to7.jpg
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The 10-shot control group fired from the Lother Walther barrel for the GECO 223 Remington 55 grain FMJ Target ammunition test . . .
https://app.box.com/shared/static/onjbshrleutycfklxr0xmp4cq56fff75.jpg
The 10-shot control group fired from the Lothar Walther barrel for the GECO 5.56x45mm 55 grain FMJ ammunition test . . .
https://app.box.com/shared/static/yyv78cwx0hyk7kxvgvxwz2c4yvem56o3.jpg
The 10-shot control group fired from the Colt 6721 barrel for the Wolf Performance 62 grain FMJ ammunition testing had an extreme spread of 0.89.
....