Baerlks

The Hellsing 13.7mm 'BAERLKS (バルクス,)' was the weapon of Seras Victoria before she received the Hallconnen from Walter C. Dornez.

Profile
In the original anime, the rifle had a more black polymer finish and stock, but in the OVA, it was switched to wood. This weapon is clearly manufactured by the Hellsing Organisation for anti-vampire combat, though it is uncertain who was intended to wield it before Seras joined, though it is possible it was strictly a mounted support weapon, or that it was designed (presumably by Walter) in between the time Seras joined and her first deployment.

The rifle was made by Hellsing Arms, the "Anti-Midians" engraving and the drum magazine that's loaded into the weapon. It is uncertain why a one-off specialty piece designed by a top-secret organization would have such detailed rollmarks which bear the organization's name; this would presumably become a problem if the weapon was lost. The actual design is based on the Mauser 1918 T-Gewehr a 13.2mm bolt action anti-tank rifle used by Germany in World War I. In the first anime series, this rifle was fully automatic, as it appeared to be self-loading. However, in the OVA, Seras fires it exclusively in a semi-automatic manner. Later on in its usage in the anime and OVA, it is used with a drum magazine.

Ammunition
She also used it with a drum magazine later on in the Anime and OVA. The stock engraving reads "Anti-Midians" and gives the caliber of the round as a massive 13.7mm, unusually large for a rifle. It was able to easily penetrate multiple ghouls head. It typically fires from a box magazine (which would appear to be able to hold around 10-15 rounds if real-world physics applied).

Usage
When Seras first joins the Hellsing Organisation Special Military Forces, she receives this rifle as a sniper. It was the main weapon for Seras before Walter created the Hallconnen canon, and presumably, made by Walter too. This weapon was never used or mentioned again after its last appearance during the battle with Tubalcain Alhambra. Seras received this rifle, which is assumed to be standard issue for Hellsing soldiers, in the first few episodes of the anime. This was before Walter decided that she needed a sidearm that complemented her superhuman vampire strength.

Name
Throughout the series, the stock engraving on the weapon changes many times and had never been consistent; the stock engraving reads "Anti-Midians" in the anime, in the manga however, the stock engraving instead reads "Hellsing 13.7mm BAERLKS", and in the OVA, it reads out "Hallconnen". Chapter 20 of the manga, the weapon again makes an appearance; this time however, the stock engraving on the weapon reads out "HELLSING 13.7mm BLADING", and "LONG HORN WATTERS".

Trivia

 * In the anime, this weapon is written as "Hellsing Anti-Midians 13.7mm", which is not what it was named in the manga. Despite this, both the anime and manga series has clearly said that this weapon uses 13.7mm rounds. The OVA however, has Hallconnen written in the same place as "BAERLKS".