223 Remington/5.56 NATO, velocity versus barrel length: A man, his chop box and his friend’s rifle

Hey man, can I cut up your rifle?

I knew that our 300 Winchester Magnum: How Does Barrel Length Change Velocity- A 16″ 300 Win Mag? article would be popular, but it has really exceeded my expectations.  Quite a few readers asked for a similar experiment with the 223 Remington and/or 5.56 NATO cartridges as well.  So after some careful negotiations with my buddy, he volunteered his Remington 700, chambered in 223 Remington for this experiment.

If you search the web, you can find quite a bit of data on 223 Remington and 5.56 NATO ballistics from 20″, 16″ and 14.5″ barrel lengths.  This makes sense since these are the most commonly used in the AR style rifles.  Intermediate barrel length data is somewhat less common.  In this article, we are starting with a 26″ barrel and cutting it back, one inch at a time to 16.5″ and measuring the average velocity with four different cartridges.

For this experiment, we used four different factory loaded cartridges; Remington UMC 223 Remington 55-grain U223R3, Federal XM193 5.56 M193 55-grain ball (the box is labeled both XM193 and M193 and has an 02 head stamp), Winchester M855 (08 head stamp) and Black Hills 223 68-grain Heavy Match ammunition.

A quick note on chambers and ammunition, 223 Remington and 5.56 NATO chambers and ammunition are not the same or necessarily interchangeable.  223 Remington is a SAMMI specification and 5.56 NATO is a NATO specification.  Without getting overly involved, chamber dimensions are different with 5.56 NATO dimensions being more generous and the 5.56 ammunition running hotter than its 223 counterpart.  In our case, our 223 rifle fired 5.56 safely, however, this may not be the case with your particular firearm.  Remember, only use ammunition that the manufacturer of your firearm recommends.

The rifle is a stock, left-handed Remington 700 with a chrome moly varmint contoured barrel.  The bolt has been fluted and the bolt knob replaced by Kampfeld Custom. The rate of twist is 1:12″. We recognize this is the wrong twist for stabilizing heavier bullets, however, feel the velocity information gathered would be worth the effort of firing the heavier bullets.   It should be noted, prior to testing we were able to shoot some 2 MOA groups with the M855.  The 68-grain Black Hills load opened up to approximately 6 MOA.

The rifle’s headspace was measured at 1.4676+ and firing pin protrusion was .053″.

We ordered the following products from Brownells for this experiment:

• Spuhr scope mount (100-011-207)
• Magnetospeed V3 chronograph (100-014-631)
• Nightforce 3-15 F1 rifle scope (100-012-583)

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What was our test protocol?

Ballistic data was gathered using a Magnetospeed barrel mounted ballistic chronograph.  At each barrel length, the rifle was fired from a front rest with rear bags, with five rounds of each type of ammunition.  Average velocity and standard deviation was logged for each round.  Since we would be gathering data on 44 different barrel length and ammunition combinations and would not be crowning the barrel after each cut; we decided to eliminate gathering data on group sizes.  Note: we did fire one test group at the end of the experiment with the barrel at 16.5″, you’ll see our results at the bottom of the page.

Once data was gathered for each cartridge at a given barrel length, the rifle was cleared and the bolt was removed.  The barrel was cut off using a cold saw.  The test protocol was repeated for the next length. Temperature was 45.7F.

 

Results

Our results are posted below.

Barrel length in inches versus Muzzle velocity in feet-per-second Rifleshooter.com
Barrel length in inches	UMC 223/55	Federal M193/55	Winchester M855/62	Black Hills 223/68
26	3182	3431	3280	2849
25	3221	3426	3229	2828
24	3211	3409	3188	2804
23	3132	3350	3169	2775
22	3111	3366	3158	2774
21	3090	3305	3117	2762
20	3071	3306	3097	2740
19	3028	3259	3060	2699
18	3006	3202	3052	2679
17	2922	3151	2972	2652
16.5	2968	3187	2992	2632
AVG velocity loss per inch	22.5	25.7	30.3	22.8

Here is the above information presented as a line graph:

 

Cartridge specific data:

Effects of barrel length on Remington UMC 223 55 grain FMJ
Barrel length in inches	UMC 223/55	SD	Change ft/sec velocity	Change ft/sec velocity from 26″
26	3182	28
25	3221	30	39	39
24	3211	16	-10	29
23	3132	28	-79	-50
22	3111	24	-21	-71
21	3090	20	-21	-92
20	3071	35	-19	-111
19	3028	30	-43	-154
18	3006	31	-22	-176
17	2922	38	-84	-260
16.5	2968	33	46	-214

 

Effects of barrel length on Federal M193 55 grain FMJ
Barrel length in inches	Federal M193/55	SD	Change ft/sec velocity	Change ft/sec velocity from 26″
26	3431	21
25	3426	31	-5	-5
24	3409	39	-17	-22
23	3350	19	-59	-81
22	3366	42	16	-65
21	3305	47	-61	-126
20	3306	24	1	-125
19	3259	39	-47	-172
18	3202	25	-57	-229
17	3151	16	-51	-280
16.5	3187	44	36	-244

 

Effects of barrel length on Winchester M855 62 grain FMJ
Barrel length in inches	Win M855/62	SD	Change ft/sec velocity	Change ft/sec velocity from 26″
26	3280	17
25	3229	24	-51	-51
24	3188	14	-41	-92
23	3169	19	-19	-111
22	3158	27	-11	-122
21	3117	11	-41	-163
20	3097	14	-20	-183
19	3060	14	-37	-220
18	3052	43	-8	-228
17	2972	19	-80	-308
16.5	2992	14	20	-288

 

Effects of barrel length on Black Hills 223 68 grain heavy match
Barrel length in inches	Black Hills 223/68	SD	Change ft/sec velocity	Change ft/sec velocity from 26″
26	2849	15
25	2828	24	-21	-21
24	2804	36	-24	-45
23	2775	40	-29	-74
22	2774	27	-1	-75
21	2762	18	-12	-87
20	2740	14	-22	-109
19	2699	27	-41	-150
18	2679	37	-20	-170
17	2652	19	-27	-197
16.5	2632	18	-20	-217

 

So, what did we find out?

1. Cutting the barrel from 26″ to 16.5 ” resulted in a velocity reduction of 214 ft/sec with the UMC 223 55 grain cartridge, 244 ft/sec with the Federal M-193 cartridge, 288 ft/sec with the Winchester M855 cartridge and 217 ft/sec with the Back hills 223 68 grain match cartridge.  It should be noted that the 17″ barrel length provided the slowest velocities in for the UMC 223 55 grain cartridge, Federal M-193 and Winchester M855 with velocity reductions of 260 ft/sec, 280 ft/sec and 308 ft/sec with each cartridge respectively.
2. Utilizing the data from the 16.5″ barrel, average velocity loss per inch of barrel length was 22.5  ft/sec for the UMC 223 55-grain cartridge, 25.7 ft/sec for the Federal M-193 cartridge, 30.3 ft/sec for the Winchester M855 cartridge, and 22.8 ft/sec for the Black Hills 68-grain heavy match cartridge.
3.  The UMC 223 55-grain cartridge experienced a fairly significant velocity loss when the barrel was cut from 24″ to 23″ of 79 ft/sec, and 18″ to 17″ with a reduction of 84 ft/sec.
4. The Federal M-193 experienced a significant velocity loss between 24″ and 23″ of 59 ft/sec, 22″ and 21″ of 61 ft/sec, 19″ and 18″ of 57 ft/sec, and 18″ and 17″ of 51 ft/sec.
5.  The Winchester M855 experienced fairly significant velocity loss as its barrel was cut from 26″ to 25″ of 51 ft/sec, and 18″ and 17″ of 80 ft/sec.
6. The Black Hills 223 68-grain heavy match was lost velocity at a fairly consistent rate.  The largest decrease in velocity resulted from the barrel being cut from 20″ to 19″ with a loss of 41 ft/sec.
7. Of the 220 test rounds fired, we logged 6 light primer strikes on the Federal M193 and 1 on the Winchester M855.  All of these cartridges fired on the second attempt.  Firing pin protrusion was adequate, .053″.  My guess is these light hits were related to the strength of the firing pin spring.

How did barrel length affect exterior ballistics?

We ran each load for 26″, 23″, 20″ and 16.5″ barrel lengths out to 600 yards, a reasonable distance for this cartridge.  These figures assume a 1.75″ height of the optic over the bore and weather conditions of 59F.

 

You’ll notice minimal difference in external ballistics out to 300 yards, but approximately 20″ of additional drop in the shorter barrel at 600 yards.

How did barrel length affect Maximum Point Blank Range (MPBR)?

Since the 223 Remington is a popular hunting cartridge, we also worked out the maximum point-blank range (sometimes referred to as maximum point blank zero) for each barrel length with the given load assuming a 8″ vital area.  We selected an 8″ MPBR for comparison purposes, since this was the same size vital area we used for the 300 Winchester Magnum barrel length article.

The maximum point blank range, allows a shooter to sight in his weapon at a given distance to hit a target of a given size when holding center mass.  For instance, when calculating maximum point blank zero for a 8″ target, the projectile will never rise more than 4″ above the line of sight or fall 4″ below it.  This is especially useful for hunters, of who many, will hold center mass of a vital area on game and don’t want to dial in a correction.  Our calculations assume a 1.75″ sight over bore height.

223/5.56 Maximum Point Blank Range (MPBR) on 8” Target
Barrel length	UMC 223 55	Federal M193	Winchester M855	Black Hills 223 68 HM
26”	322 yds	343 yds	340 yds	305 yds
16.5”	302 yds	322 yds	313 yds	284 yds
Change in MPBR	20 yds	21 yds	27 yds	21 yds

You’ll notice the change in MPBR averages 22 yards across the cartridges.

Closing

What are the possible sources of error in our experiment?  You’ll notice an increase in velocity despite a decrease in barrel length in a few instances in the data above.  I would attribute this to a relatively small sample size. Most of the other experiments I have read about, use three rounds of each combination.  Only one used ten, but they did not provide data and the claims seem to be dubious in nature.  We shot five rounds for each combination. We had certain time constraints, budget limitations, etc.  Gathering the data takes two guys and an entire day. Processing and writing about it takes much longer.

How did we improve this experiment over the last one we did? Compared to the 300 Winchester Magnum: How Does Barrel Length Change Velocity- A 16″ 300 Win Mag?  experiment, we did do a few things differently.   First, we used a chop box that didn’t beat up the gun nearly as much as a reciprocating saw or hacksaw.  The cut was more precise than the previous methods we had tried.   While it required us to drag the saw and the generator to the range, it was certainly worth it. We also introduced four different types and weights of ammunition.  Finally, we placed the chronograph at the same point, 2″ from the muzzle at each barrel length to ensure our data was recorded at the same spot.

Why didn’t we cut and crown the barrel at each length?  Short answer is that it takes too much time.  For the long answer, read on.  I’ve read about this criticism a few times in the 300 Win Mag article, and while I think this would be beneficial for accuracy testing (which was outside the scope of this experiment), professionally re-cutting the crown would have added a tremendous amount of time to the experiment.  My lathe is in my basement; a 2-hour round trip from the range.  Counting set up time at the range, this would have added a minimum of 30 hours to the overall time required to complete this experiment.

Do you think you lose a lot with a short barrel in a 223?  In most applications, I think the shorter barrel has a lot going for it: easier maneuverability, quicker handling and a lighter rifle; all at a fairly small velocity loss. For special applications, like building a 600 or 1,000 yard F-class T/R rig, I would certainly go long (like most guys do), but for your average rifle and rifleman, shorter seems to work well.

In some of your other short barreled rifle articles you mention that shorter barrels look cooler, do you still believe this?  Yes, I do.  Short barrels look much cooler.  This is a fact, proven again and again.  A friend commented that you should enjoy the way your short barreled rifle looks, because your hearing will be gone and your sight will be your only sense left.  Maybe he is right.

Have you seen similar experiments with a 223 Remington?  Yes, three that are noteworthy.  Posted in 2001, Accuratereloading.com used handloads and documented barrel length from 22 to 10″ long, you can find it here.  Ballisticsbytheinch.com used 45, 50 and 55-grain factory ammunition from 18″ to 3″ in length, you can find that article here.  A friend sent me a link to this article using four different guns, 3 bolt action and 1 gas gun.

Did you shoot any groups?  Yes, a few.  We did shoot a couple of sub MOA groups with the 16.5″ barrel.  I posted a pic of the group and crown below.  Pretty interesting, huh?

Why didn’t you use a 1:7 or 1:9 twist barrel?  We would have liked too, but didn’t have one available.  I don’t believe this would have had an impact on velocity figures.

Why didn’t you spend more time discussing the differences between 223 Remington and 5.56mm NATO?  Dude, it’s been discussed ad nauseam in every internet forum and blog in the gun industry.  I’ll pass.  I will take a wild guess that in the comments following a link to this article on any forum or blog, someone will mention that they are different and wonder why I didn’t use a 1:7 twist.

Did the rifle get noticeably louder? Yes, especially with the M193 at 17″ and M855 at 16.5″.   The other two loads weren’t as obnoxious at the shorter lengths.

Whats next?  I am considering a 338 Lapua and a 308 Winchester article.  If I do, I will post a link here.

I hope that the data presented here was helpful.  Until next time, stay safe.