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Reloading: Belt up

Reloading: Belt up

Yup, the answer is of course, Magnum. It first appeared in the English language in the late 18th Century, derived from the Latin word magnus – meaning ‘great’. The first popular application was in the description of double sized wine bottles, such as the magnum of champagne.

The first magnum

Whilst it is popularly believed to be the early 20th Century before Holland & Holland (H&H) adopted the adjective, this is not really true. Although hard to award a design credit, the earliest recorded use of the word goes to the .500/450 3¼” Magnum Express BPE (Black Powder Express). A rimmed big game monster that in original coiled brass form dates to the 1870s. It is from this cartridge that the innovative Henry Holland undoubtedly lifted the description, as he is generally accepted to have re-engineered the later (turn of the century) iteration of the Magnum, the .500/450 3¼” Nitro Express.

The first of his cartridge designs to embrace the term being the legendary .375 H & H Magnum of 1912 – setting as it did, the prime dimensions for magnum cartridge design for decades thereafter. Indeed, it was to be the parent case for many of them. The visually significant rimless, belted design also helping to establish a strong identity for almost all subsequent magnum creations well into the 1960s. Not that the .375 H&H Mag was the first belted case design, but was the second, following the .400/.375 Belted Nitro Express, introduced seven years earlier by Henry Holland. This novel design was not present to impart additional strength but was intended to provide a stable shoulder for head spacing, not unlike a rim, but still feed reliably from the box magazines of repeating rifles. It was a brilliant concept.

Same fate as turbos

So the Magnum, rather like the Turbo in motor cars in the 1970’s (following their adoption in F1 racing), became synonymous with increased power. The Oldsmobile Jetfire and Chevy Monza of the 1960s were the true, if highly unreliable first examples of turbo cars. Sadly, the two have followed the same fate, with the word Magnum now prostituted by many cartridge manufacturers in order to promote a lesser product… and turbos now fitted to almost everything other than strimmers, often as a means of adding badge status and improving the fuel economy of puny little engines.

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Which leads us to the issues and considerations relating to hand loading belted magnums. It is important to remember that their designers did not give any consideration to the re-filling of their creations. After all, they wanted to sell new ammo. The first things to consider are age and infirmity. That is, the age of the arm and the infirmity of the brass. Older rifles chambered for belted ammo may well have chamber dimensions that vary from the standard figures for the calibre and old brass may have age-hardened.

A nasty growth!

Assuming that the arm is in Proof, chambering a factory round should not pose a problem – until it is fired. The newly fire-formed case being the first and easiest means of indicating our chamber size. Use a vernier to compare the fired brass with the published ‘standard’ chamber dimensions or, if not available, with those of an unfired round from the same batch. If you have a chamber gauge, so much the better. Some growth will have inevitably occurred, that’s why we need to at least partially resize, but the extent and location of the growth is what we need to know. Remembering that as the head spacing was on the belt, the key issues surround case growth beyond this point. And on a first firing there may be lots of it! In extreme instances this might well render the case unfit for further safe use due to the risk of head separation. A slightly brighter line around the body just above the belt is a sure tell-tale!

Your measurements may come as a shock, with the case length from head to shoulder increased by as much as a massive 0.75mm (.030”). Our task is to make the case safe to shoot with the minimum level of rework. Start with a thorough inspection then de-prime and neck size before trying it in the chamber. If it is a free fit and the bolt closes cleanly, then we’re good to go. If it won’t fully insert, or the bolt is stiff, then the chances are that the shoulder will need a slight degree of bumping with your FL die. However, make sure that the die is not bottoming out on either the case belt or the shell holder… it happens. Carry out the operation at less than half a turn at a time. A neck trim may well be necessary afterwards.

Minute examination

Whilst there is no hard and fast rule, a belted mag loaded within spec and fired in a chamber that meets SAAMI should give three to six reloads before the shoulder needs attention. Thereafter the case must be minutely examined for signs of separation. If a bulge appears, then there is a proprietary Belted Magnum Collet Resizing Die offered by Larry Willis at Innovative Technologies in Casselberry, Florida and no, I’ve never used one. What I do use for internal inspection of bottle neck cases where the calibre exceeds 5.56mm is a 6 light micro USB camera – it also doubles as a modest bore scope. Remember, whatever you do to re-size a case you will not ‘fill’ stretch damage.

If you’re reloading a straight wall (taper) belted cartridge, such as the .458 Win Mag or .458 Lott, then things are a bit easier, just neck size for the first loading, keeping a careful note of case length and stretch damage above the belt. Thereafter, check the chamber fit, neck size and trim as required. When there is slight chambering resistance from your fired case, check first for damage and bulges above the belt. If there are no issues, then an FL resize and trim are called for. Remember that repeated heavy crimps can induce cracks in the neck. Enjoy your ice cream confection!

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