300 Winchester Magnum: How Does Barrel Length Change Velocity- A 16″ 300 Win Mag?

What happens when we cut down our 300 Winchester Magnum from 24.25" to 16.25"?

Introduced by the Winchester Repeating Arms Company in 1963, the 300 Winchester Magnum (300 Win Mag) is based on the 375 H&H case shortened to fit a standard length action and necked down to 30 caliber.  Long popular with big game hunters, the 300 Winchester Magnum has also been adopted by the US military as part of the M24 Sniper Weapons System and Mk 13.

A commonly asked question on hunting, long range shooting and Mil/LE forums is, “how long should the barrel on a 300 Winchester Magnum be?”   I’ve been coming up short of any objective analysis of barrel length based off of actual data- i.e., cutting back the same barrel and publishing actual velocities.  Most, while well informed, are based off of data extrapolation and comparing a few different barrel lengths on dissimilar rifles.

223 Remington (left), 308 Winchester (center), 300 Winchester Magnum (right).
223 Remington (left), 308 Winchester (center), 300 Winchester Magnum (right).  Note belt at base of cartridge case.

We headed to the range with a 300 Winchester Magnum, a chronograph and my hacksaw.  It’s time to see what happens to the same gun, under the same conditions, as the barrel is set back one inch at a time.

Remington 700 in 300 Winchester Magnum on the firing line. This is the 24.25" barrel I started with.
Remington 700 in 300 Winchester Magnum on the firing line. This is the 24.25″ barrel we started with.

Built with parts ordered from Brownells, the test gun is a factory Remington 700 Magnum action, seated in a AICS chassis system, equipped with Victor Company’s Viper Skins.  A Shilen #8 contour chrome-moly barrel had been threaded and chambered on the gun.  No other accurizing work has been performed.  This is the first day the gun will be fired.

Here is a list of the parts, as well as the Brownells part number:

  1. Remington 700 Magnum Action (767-000-867)
  2. Shilen #8 1:10 barrel blank (787-308-107)
  3. AICS chassis system (100-005-929)
  4. 34mm Spuhr Mount (100-011-208)
  5. Leupold Mark 6, 3-18 scope with TMR reticle (526-000-204)
  6. Federal Gold Medal 300 Winchester Magnum Ammunition 190 SMK (105-200-479)
A Leupold Mark 6, 3-18X44mm front focal plane scope secured on a Spuhr Ideal scope mount.
A Leupold Mark 6, 3-18X44mm front focal plane scope secured on a Spuhr Ideal scope mount.
A belted magnum (left) go gauge compared to a rimless bottle neck cartridge go gauge (right). The belt magnum is headspaced with the rim, while the rimless cartridge is headspaced off a datum point on the shoulder. Most agree, headspacing off of the shoulder provides superior accuracy.
A belted magnum (left) go gauge compared to a rimless bottle neck cartridge go gauge (right). The belt magnum is headspaced with the rim, while the rimless cartridge is headspaced off a datum point on the shoulder. Most agree, headspacing off of the shoulder provides superior accuracy.


Test Protocol

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The test protocol was simple.  The rifle is fired at 100 yards, from a bipod with a rear bag, for 5-rounds.  The velocity and standard deviation are recorded.  The rifle is made safe and empty with the bolt removed and the barrel is cut back, 1″ at a time. 

I selected Federal 190 grain Gold Medal ammunition for this test.  While it wouldn’t be your first choice for hunting ammunition, Federal Gold Medal works well, is widely available, and serves as a good standard for comparison.

After bore sighting the rifle and confirming zero at 50-yards.  The rifle was zeroed at 100-yards and the testing began. The initial barrel length was 24.25 inches.  We cut it back at 1-inch intervals ending up with a 16.25 inch barrel.  The crown was not re-cut, burrs were not removed and the gun was shot with the saw cut, as-is.  Initially we (it’s always good to bring a friend with this much cutting) used a cordless Sawzall to make the cuts, after the battery died, we switched to a hacksaw.  There was no power at the range so a chop box was out of the question.

Chronograph data was recorded using a MagnettoSpeed V2 barrel mounted ballistic chronograph.  Range conditions were good for a December day in the Northeastern USA.   That means it was 55 F, heavy rain, and overcast with mild 5 to 10 mile per hour winds.  Ambient lighting was poor, we were barely able to read printed material from the firing line beneath overhead cover and it was 11 o’clock in the morning.

The bayonet mount from the MagnettoSPeed Ballistic Chronograph.
The bayonet mount from the MagnettoSpeed Ballistic Chronograph.
I marked the barrel ahead of time.
I marked the barrel ahead of time.
The reciprocating saw worked but it vibrated the heck out of the rifle and optic.
The reciprocating saw worked but it vibrated the heck out of the rifle and optic.
A representative crown. Shockingly, this crown produced a .744" 5 shot group at 100 yards!
A representative crown. Shockingly, this crown produced a .744″ 5 shot group at 100 yards!
After 3 cuts, we switched to the hacksaw.
After 3 cuts, we switched to the hacksaw.
It took a lot of elbow grease to make this many cuts.
It took a lot of elbow grease to make this many cuts.
19.25" and 20.25" barrel length groups.
19.25″ and 20.25″ barrel length groups.
This 5 shot groups was fired from the 17.25" hacksaw cut barrel!
This 5-shot group was fired from the 17.25″ hacksaw cut barrel!
The rifle, hacksaw and barrel sections.
The rifle, hacksaw and barrel sections.

Data is posted below:

Barrel length Velocity ft/sec SD Change ft/sec in velocity Change ft/sec in velocity from 24” barrel AVG in velocity change in ft/sec per inch Group size: note hacksaw crown
24.25” 2892 26  0  0  0  .947”
23.25” 2851 31 -41 -41 -41.0  .725”
22.25” 2786 60 -65 -106 -53.0  .744”
21.25” 2789 17 +3 -103 -34.3 1.799”
20.25” 2752 14 -37 -140 -35.0  .930”
19.25” 2727 11 -25 -165 -33.0 1.372”
18.25” 2696 11 -31 -196 -32.7 1.337”
17.25” 2640 25 -56 -252 -36.0  .874”
16.25” 2575 6 -65 -317 -39.6 1.353”
AVG 22 -39.6 1.120”

Each reduction in barrel length averaged 39.6 ft/sec in velocity loss.  Significant jumps in velocity reduction occurred between 18.25 and 16.25 inches (56, 65 ft/sec) and between 23.25 and 22.25 inches (65 ft/sec).  Standard deviation generally decreased as the barrel got shorter.

A 3 ft/sec increase in muzzle velocity was recorded between the 22.25 and 21.25 inch barrels.  This was unexpected, but the target confirms these similarities with all 10-rounds landing within a 1.799″ inch group (the one fired by the 21.25″ barrel).

300 win bbl length line

So, what does this mean downrange?  Lets take a look at drop and drift at 1,000 yards (the internet’s favorite distance) for each length barrel.  The table below assumes a 100 yard zero and a full value, 10 mph crosswind for wind drift.

Barrel length Path (inches) Path(mils) Drift(inches) Drift(mils) Velocity ft/sec @ 1,000 yards
24.25” -306.5 U8.5 -56.8 R1.6 1,393
23.25” -317.3 U8.8 -58.2 R1.6 1,365
22.25” -335.5 U9.3 -60.5 R1.7 1,320
21.25” -334.6 U9.3 -60.3 R1.7 1,322
20.25” -345.8 U9.6 -61.8 R1.7 1,297
19.25” -353.5 U9.8 -62.7 R1.7 1,280
18.25” -362.5 U10.1 -63.9 R1.8 1,259
17.25” -382.6 U10.6 -66.3 R1.8 1,221
16.25” -406.6 U11.3 -69.1 R1.9 1,178

While the Federal Gold Medal 190 grain ammunition from the 16.25 inch barrel has a flight path 100 inches lower then the 24.25 inch barrel, the effects of a full value wind are less significant.  The 16.25 inch barrel only having 12.3 inches more of drift at that distance.

Comparative trajectories of the different barrel lengths in 2" increments.
Comparative trajectories of the different barrel lengths in 2″ increments.

Since the 300 Winchester Magnum is a popular hunting cartridge, I also worked out the maximum point-blank zero for each barrel length with the given load assuming a 8″ vital area on deer sized game.

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

300 win mag point blank zero

While there may be differences in the effects on the quarry from the velocity, the difference in maximum point- blank range is relatively small  (34 yards) between the 24.25 (327 yards) and 16.25 inch (293 yards) barrels.

Did recoil, muzzle flip, or muzzle blast change?

Firing the rifle with the 24.25 inch barrel was pleasant (for a belted magnum) with minimal muzzle rise.  Recoil and muzzle blast increased significantly when the barrel reached 20.25 inches in length and again below 18.25 inches.  The 16.25 inch made my shooting buddy laugh.  He said the ground 15 feet in front of the muzzle was blowing around.  I developed a mild headache from the 50 rounds of ammunition I shot, despite wearing both ear plugs and muffs.

Did the point of impact shift as the barrel was cut?

Yes, it did, but less then expected.  I did periodically make scope adjustments to utilize different parts of the target, but in general, groups were within 1 inch of the group fired with the previous barrel length.  In some cases, the point of impact was unchanged.

How much did weight change as the barrel was cut?

Weight of the rifle, including bipod, optic and mount was 18.28 pounds with a 24.25 inch barrel.  Weight decreased 1.82 pounds to 16.46 pounds with the 16.25 inch barrel.  Keep in mind almost two pounds came off the muzzle end.  The rifle became easier to handle at the expense of decreased ballistic performance and increased recoil, muzzle flip and blast.

What are the possible sources of error?

Possible sources of error include:

  1. Small sample size.  We only chronographed 5-rounds at each barrel length, a greater number of rounds would provide more reliable results.
  2. Heavy trigger.  The factory 700 trigger was turned all the way down to 4 pounds, 12 ounces.  A few of the larger groups contained one flyer (see some samples in the photos above).  While this wasn’t an accuracy test (hacksaw cut crown), I personally feel the larger groups would have been smaller with a lighter trigger.
  3. Sawzall induced stress and vibration.  If you haven’t used a reciprocating saw to cut a barrel off, you haven’t lived.  That said, it shook the rifle violently for extended periods of time.  I don’t see how that can be good for accuracy.  The screws holding the Viper Skins actually fell out onto the shooting bench.  One of us sat on the rifle other while the other cut the barrel.  The hacksaw was far less violent, but still required one of us to sit on the rifle while we cut it.  I should note that the scope held it zero and worked well despite the harsh conditions we caused.
  4. Only one type of ammunition was used.  While the Gold Medal 190 grain ammunition is a good standard for testing, it doesn’t represent heavier bullets and slower burning powders which will show greater benefit from longer barrels.

So what did we learn?

  1. What was the average velocity loss per inch?  39.6 ft/sec.  See the table above for specifics.
  2. Longer may not necessarily be better.  While the longer barrel has a milder recoil, and less muzzle rise with superior ballistics, the short barrels aren’t as wanting as you would think.  This is especially true for typical big game hunting applications where the maximum point-blank zero may be used.  This doesn’t mean I don’t think a 16 inch 300 Winchester Magnum is silly, because it is, I just think there may be some merit to moderate barrel lengths for this cartridge.
  3. Are short barrel magnums a good idea?  I don’t think so.  I am unsure what a short barrel 300 Winchester Magnum gives you that a long barrel 308 or 30-06 won’t.  A mid length barrel, say 22 inches, offers better external ballistics, terminal ballistics, less muzzle flip and a reduced blast.  I think my next 300 Winchester Magnum will be at least 22 or 23 inches.
  4. Isn’t a 16″ 300 Winchester Magnum basically a 24″ 308 Winchester?  Basically, yes.  While my personal experience loading the 190 SMK in a 24-inch 308 provided slower then published results, according to the reloading manuals I referenced, 190 grain projectiles from a 308 with a 24 inch barrel will have a similar velocity.  The 17-inch 300 is similar to a 30-06.  Keep in mind, the 308 or 30-06 would be far more pleasant to shoot, use cheaper brass, less powder and have a shorter powder column and are theoretically more accurate since they do not headspace off of a rim.
  5. A small change in barrel length may or may not have much effect on velocity.  Some cuts reduced muzzle velocity significantly, while some did not, and in one case, a small (3 ft/sec) increase was noted.  Personally, I would prefer a shorter barrel IF velocity and accuracy were identical.  This is an instance where I wish I had shot 10 rounds per barrel length to increase the reliability of my results.
  6. Does a rifle’s crown affect accuracy?  This was the million dollar question today.  I’ve read a series of similar experiments where the shooter intentionally damaged his crown to see how it affected group size.  This wasn’t the primary purpose of this experiment, however.  But, I was able to shoot a series of sub MOA groups with a hacksaw cut crown.  I would say in those cases, the crown didn’t matter; but in the larger, over 1 MOA groups, the crown clearly had a negative impact on accuracy.
  7. What about a 26″ 300 Winchester Magnum? I don’t know.  Looking back, I wish I had a 26 inch barrel to start with.  Published velocities seem to have a 26 inch barrel pushing 190 Gold Medal at 2900 ft/sec, which, doesn’t seem to be much of a gain.  However, with some of the newer, slower burning powders, there may be some benefit to the 2 additional inches of barrel length especially with heavier projectiles.  The 190 is old hat for the many 300 Winchester Magnum shooters.  Heavier projectiles and slow powders offer promising long range potential, filling the gap between the 308 Winchester and 338 Lapua/338 Norma.
  8. Do short rifles look cooler?  Yep, they sure do.  The rifle looked cooler the shorter you cut it.

What’s next?

This was an experiment I kicked around for the past year or so.  Finally, the lure of potential internet greatness set in and I decided to pull the trigger.  Discussing the methodology with friends, I originally envisioned stopping around 20″, cutting off the chamber end of the barrel and using it for a 308.  At the range I looked at my shooting buddy and we decided to go all in and cut it to 16.25″.

If (and that’s big if) I do it again for another cartridge I’ll probably fire more rounds at each interval, shoot a slow and fast powder at each length, and use a light contour barrel since it would be easier to cut.

UPDATE: 1/1/15, see below for 308 Winchester and 223 Remington

308 Winchester / 7.62x51mm NATO: Barrel Length versus Velocity (28″ to 16.5″)

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

I’m going to install a brake, crown the barrel the right way and be the proud owner of a 16.25 inch 300 Winchester Magnum barrel… I’m unsure I’ll shoot it much, if at all, but at least I can definitively tell someone what happens when you cut your 300 Winchester Magnum to 16.25 inches.

My follow up article is here Does size matter? Custom Remington 700 16.5″ 300 Winchester Magnum follow up

You can read about our far more practical 16.5″ 308 here: Short Rifle, Long Range: Testing our 16.5″ 308 Remington 700 out to 635 yards

If you are interested in more formal analysis of how barrel length affects velocity, take a look at Ballistics by the Inch.  They have amassed a lot of data on various cartridges (mostly handgun).

Visit Brownells to accessorize your 300 Winchester Magnum.

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