April 11th, 2019

Velocity Test with Four Different Barrels — Surprising Results

barrel speed testing

Put the same load in a variety of barrels (with the same length and chamberings) and you’ll see a wide variance in muzzle velocity. In fact, it’s not unusual to see up to 100 fps difference from one barrel to the next. We demonstrated this with a comparison test of Lapua factory ammo.

Chron Testing Lapua Factory Ammo
At our Southern California test range some years ago, we chronographed Lapua 105gr 6mmBR factory ammo in three different 8-twist barrels of similar length. The results were fascinating. Lapua specs this ammo at 2790 fps, based on Lapua’s testing with its own 26″ test barrel. We observed a speed variance of 67 fps based on tests with three aftermarket barrels.

Barrel Velocity Variance
Brand ‘S’ and Brand ‘PN’ were pre-fit barrels shot on Savage actions. Brand ‘K’ was fitted to a custom action. All test barrels were throated for the 100-108 grain bullets, though there may have been some slight variances in barrel freebore. With a COAL of 2.330″, the rounds were “jumping” to the rifling in all barrels.

Among the four barrels, Brand ‘PN’ was the fastest at 2824 fps average — 67 fps faster than the slowest barrel. Roughly 10 fps can be attributed to the slightly longer length (27″ vs. 26″), but otherwise this particular barrel was simply faster than the rest. (Click Here for results of 6mmBR Barrel Length Velocity Test).

IMPORTANT: Results Are Barrel-Specific, Not Brand-Specific

These tests demonstrate that the exact same load can perform very differently in different barrels. We aren’t publishing the barrel-makers’ names, because it would be wrong to assume that ‘Brand X’ is always going to be faster than ‘Brand Y’ based on test results from a single barrel. In fact, velocities can vary up to 100 fps with two identical-spec barrels from the SAME manufacturer. That’s right, you can have two 8-twist, 26″ barrels, with the same land-groove configuration and contour, from the same manufacturer, and one can be much faster than another.

Don’t Demand More Than Your Barrel Can Deliver
We often hear guys lament, “I don’t get it… how can you guys get 2900 fps with your 6BRs and I can only get 2840?” The answer may simply be that the barrel is slower than average. If you have a slow barrel, you can try using more powder, but there is a good chance it may never run as fast as an inherently fast barrel. You shouldn’t knock yourself out (and over-stress your brass) trying to duplicate the velocities someone else may be getting. You need to work within the limits of your barrel.

Factory Ammo Provides a Benchmark
If you have a .223 Rem, 6mmBR, .243 Win, 6.5×47 Lapua, 6.5 Creedmoor, 6.5×55, .308 Win, 30-06, or .338 LM Rifle, we recommend you buy a box of Lapua factory-loaded ammo. This stuff will shoot great (typically around half-MOA), and it can give you a baseline to determine how your barrel stacks up speedwise. [Editor’s NOTE: The original test was conducted in 2008. The velocity of current-production Lapua factory ammo might be higher or lower, so your results may vary.]

When you complete a new 6mmBR rifle, it’s definitely smart to get a box of the factory ammo and chronograph it. That will immediately give you a good idea whether you have a slow, average, or fast barrel. Then you can set your velocity goals accordingly. For example, if the factory 6BR ammo runs about 2780-2790 fps in your gun, it has an average barrel. If it runs 2820+ in a 26″ barrel (or 2835 fps in a 28″), you’ve got a fast tube.

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April 11th, 2019

New Vortex Razor Rangefinder Claims Extreme Ranging Ability

vortex razor lrf laser rangefinder 4000 yards range test review

Vortex 4000 Laser Rangefinder under $500.00

Review by Derek for EuroOptic.com
Laser rangefinders are one of the fastest evolving products in the shooting industry. A decade ago, a laser rangefinder capable of 3000+ yard performance would have had the same price tag as a brand new truck and would have been rarely seen outside of a military operation. Even a laser rangefinder capable of 1200-yard performance a decade ago would have come with a hefty price tag. Now in 2019 however, nobody expects to pay more than $450 for a laser rangefinder capable of that rated performance.

vortex razor lrf laser rangefinder 4000 yards range test review

That brings us to today — Vortex Optics just released a brand new laser rangefinder dubbed the Razor HD 4000. The Vortex Razor HD 4000 seems to perfectly fill a void between the economical Ranger LRF 1800 Monocular and the premium Fury HD 5000 Rangefinding Binocular in Vortex’s line-up of rangefinders. Retailing at $499.99, the Vortex Razor HD 4000 is a compact 7x monocular rangefinder. Vortex boasts that the Razor HD 4000 is capable of ranging reflective objects out 4000 yards, trees out to 2500, and deer-sized targets out to 2200 yards. Additionally, the device will deliver measurements as close as 5 yards and can compute angle correction of +/- 70 degrees. The angle correction is a big plus for hunters working in hilly country, where up-angle and down-angle shots are common.

I was able to look over the Razor HD 4000 and get a good feel for the device. This new LRF is now available for $499.99 and will begin shipping to customers on 4/11/2019. The configuration of the device’s controls is fairly ergonomic as you’d expect with most monocular laser rangefinders. I was able to briefly test the ranging capabilities but due to environmental constraints the farthest reading I got was approximately 2400 yards on a reflective target, but I do suspect that the Razor HD 4000 is capable of more. [Editor’s NOTE: In the real world, even a 2400-yard reflection return is outstanding and on a par with some far more expensive 3000-yard rated LRFs.]

Tripod Adaptability and Quality Accessories
We’re please to note the Razor HD 4000 has 1/4×20 female threaded socket on the underside for attachment to a tripod. [Editor: We wish all Laser Rangefinders had this feature.] Another neat but easily missed feature is that the battery cap has a tab that flips out and can be used to unscrew the cap. This makes swapping out the battery easier when you don’t have your multi-tool or are wearing gloves. The unit also comes in a rigid soft case, a wrist lanyard/ tether, and a heavy duty pocket clip.

vortex razor lrf laser rangefinder 4000 yards range test review

Vortex has recently hit home runs with the Razor scopes, Diamondback Tacticals and Viper PSTs just to name a few. I am willing to bet this Razor HD 4000 is going to be a great performer as well.

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April 11th, 2019

FOV, Exit Pupil, Twilight Factor — Optics Lingo Explained

Swarovski Optik exit pupil scope accurateshooter.com

Swarovski Optik exit pupil scope accurateshooter.comWhen shopping for a new riflescope or spotting scope it’s easy to get confused by all the technical terminology. Do you wish you had a better way to compare scopes — beyond just size, weight, and price? Well Swarovski Optik can help. The Swarovski Hunting Blog offers a helpful guide to technical terms used when comparing scope specifications. Here are some important definitions, expressed in layman’s language:

Objective Lens Diameter
The objective lens diameter determines the size of the optical system’s entrance pupil. The bigger the objective lens diameter, the more light the system can capture. However, the size of the objective lens does not determine the size of the field of view.

Exit Pupil
The size of the Exit Pupil is determined by the objective lens diameter and the magnification. If you look at the eyepiece from a distance of around 30 cm (11.8 in), the Exit Pupil appears as a bright disc.

For calculating the Exit Pupil the formula is:

Exit Pupil = objective lens diameter ÷ magnification (expressed in power number).

The larger the Exit Pupil, the more light will reach the eye.

Field of View
The Field of View is the size of the circular section of the area which can be observed when you look through a long-range optical device. In the case of rifle scopes, it is specified at a distance of 100 meters or 100 yards. For example, 42.5 m at 100 m or 127.5″ at 100 yards. As an alternative, the Field of View can also be stated in degrees (e.g. 6.6°).

Swarovski Optik exit pupil scope accurateshooter.com

NOTE: The technically-feasible size for the Field of View is essentially determined by the magnification. The higher the magnification the smaller the Field of View.

Twilight Factor
The Twilight Factor defines the optical system’s performance in poor light. The statement “the greater the twilight factor, the better the suitability for twilight” only applies if the exit pupil is larger than or at least as big as the eye’s pupil. The pupil in the human eye can only open to around 8 mm. As we get older, our eyes become less flexible, which limits our ability to see things in twilight or at night. Therefore [an optic’s] exit pupil cannot always be fully utilized.

For calculating the Twilight Factor the formula is:

Twilight Factor = root of ( magnification x objective lens diameter ).

NOTE: Spotting scopes have extremely high twilight factors because of their high magnification and large objective lens diameter. But [when used at high magnification] their small exit pupil can make them [somewhat difficult] to use in twilight.

CLICK HERE to Read Full Article (with more illustrations).

Photos copyright Swarovski Optik Blog, all rights reserved.

Story Tip by EdLongrange. We welcome reader submissions.
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