Belmont Ammunition 250gr Scenar 338LM

Gunslinger PLRS 250gr Scenar .338 Lapua Magnum Ammunition from Belmont Ammunition: Ballistic Data for an AWSM	www.gunslinger.net.nz Gunslinger PLRS Limited © 2010, Gunslinger PLRS Limited, New Zealand. All rights reserved. Contact: shane_cossar@hotmail.com
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A wooden crate containing 400 rounds of .338 Lapua Magnum 250gr Scenar ammunition from Belmont Ammunition - quality components, and consistent loads.
Introduction One of the aspects often overlooked in practical long range shooting is the availability of ammunition for the chosen calibre. The .338 Lapua Magnum has become popular over the last few years, but in New Zealand the supply of imported ammunition tends to fluctuate. Luckily, New Zealand does have an importer of Lapua components, and a manufacturer of .338 LM ammunition - Belmont Ammunition. This article describes a process for determining ballistic data for the Belmont produced 250gr .338LM ammunition - to be used with an Accuracy International AWSM. In the worked example below, there are four steps to confirming the ballistic data for the Belmont Ammunition: Step 1a - Identify Ballistic Coefficients. Using the Lapua data confirm what ranges the ballistic coefficients apply at. I use The Horus Vision ATrag-MX as my ballistic calculator, and that means I need to identify the range the C1 ballistic coefficients apply at, rather than thevelocities in the Lapua data. Step 1b - Confirm Calculated Firing Solutions Using ATrag-MX, and after loading all data as per the Lapua data (not my actual gun eg bore height is different) enter various ranges and check the resulting firing solution against the bullet drop Lapua data. Step 2 - Calculate Muzzle Velocity Head down to the shooting range and chronograph the Belmont Ammunition, at different temperatues. Step 3 - Using Actual Atmospheric Data Confirm Actual Firing Solutions in the field Head out to the field and with ATrag-MX updated with my gun data, and the field atmospheric conditions, shoot at targets at long ranges.	Purchase sporting and hunting ammunition from Belmont Ammunition at: www.belmontammunition.co.nz Other information on this page: Step 1a - identify Ballistic Coefficients Step 1b - Confirm Calculated Firing Solutions Step 2 - Calculate Muzzle Velocity Step 3 - Using Actual Atmospheric Data Confirm Actual Firing Solutions in the Field
Lapua Ballistic Data A big advantage of .338LM is the amount of ballistic data that is available from Lapua. If I had Lapua manufactured ammunition I'd simply go with the stated muzzle velocity and ballistic coefficients.	Download ballistic data from Lapua at: www.lapua.com
Step 1a - Identify Ballistic Coefficients ATrag-MX allows of to seven C1 ballistic coefficients to be recorded. This is because the C1 varies at different velocities (and associated distance), particularly at transonic velocities. The first approach taken has been to reverse calculate the C1 at 300m, 600m, and 1000m from the Lapua stated bullet drop data. The Lapua data states the C1 as applying between one velocity and a second velocity. In this case the distance has been confirmed, by matching the calculated mil hold with the bullet drop information: 300m = 1.12 mils = -336mm, 600m = 3.60 mils = -2164mm, 1000m = -8274mm. The second approach taken has been to simply enter the Lapua stated C1 at 1400m, 1600m, and 2000m - based on the Lapua Downrange velocity graph.	QuickTarget Unlimited Lapua Edition confirms the calculated drop - in this case at 1000m.
Step 1b - Confirm Calculated Firing Solutions So using ATrag-MX, and using the calculated C1 coefficients the firing solution fits the Lapua data - within 1cm at 1000m. Note that Coriolis is shown separately, because the Lapua data doesn't account for it. By including the same variables as the Lapua data eg bore height of 4cm / 1.57", MV of 2970 for a 27" and the ICAO atmospheric data ( temperature 59F, station pressure of 29.92 inHg, and relative humidity of 0%) any calculated range can be confirmed as matching the Lapua data.
Step 2 - Calculate MV This MV data is based on an Accuracy International AWSM, with a 27" barrel with a muzzle brake. The ammunition is from Belmont Ammunition and closely matches Lapua factory ammunition. The specific composition is: Bullet - 250gr Scenar (GB488), .338LM Powder - AR2225, 94g/gr Case - Lapua, factory trim length Primer - Federal GM215M, COL 3.59" During July 2010, muzzle velocities were chronographed at 41F / 5C of 2924 fps and at 50F / 10C of 2935 fps. These were chronographed using a CED M2 using standard screens, set out at 18 feet from the muzzle, and the values have been adjusted to the muzzle velocity. The location was at Lake Tekapo, New Zealand, at an altitude of 735m.	The MV for a 26" barrel is 2914fps (29.92 inHG, and 85F). (Data courtesy of Belmont Ammunition)
Step 3 - Using Actual Atmospheric Data Confirm the Firing Solutions in the Field TBC.

Disclaimer: Shooting is potentially dangerous and damaged equipment can be expensive to fix. You should confirm all changes to be made to your rifle system and shooting practices with your local gunsmith or gunshop owner. The example and data above are provided for information purposes only. No warranty is made for its suitability or use within your rifle.