I think it's mainly a strategic brand management decision, driven by the different ownership of the companies.
Rigby is owned by Luke and Ortmeir Group, who are a holding company who deal in firearms. They own Mauser, Rigby, Hammerli, Sig Sauer and a couple others. Rigby is their premium offering in the way that Jaguar is Tata's.
Purdey, by contrast, is owned by the Richemont Group, a holding company for luxury goods and brands. They own Vacheron Constantin, Cartier, and Montblanc, amongst others.
Holland and Holland, until 2021, was owned by Chanel. Although now it's Beretta's.
Westley Richards is a bit more opaque, although the chief financier is Sheikh Sultan Bin Jassim Al Thani of Qatar, so I presume it's mostly a passion / vanity project.
Anyhow, in Luxury brands, brand equity supersedes all other considerations. It's the most valuable part of the product. You keep it exclusive at all costs, because any downmarket stretch damages the IP. If you look at say Purdey as a luxury brand (Richemont clearly does, that's all they deal in), the fact that it's expensive makes it exclusive, which justifies the price, which justifies the exclusivity. A virtuous circle. The fact that doing so doesn't allow you to sell many units is a good thing, because it allows you to charge any price you want, and the more you charge, the more people desire the good. Growth in revenue and profit comes primarily from increasingly high price points, not drastically increasing sales volumes.
If you're primarily interested in making firearms however, a bit of downmarket stretch is no bad thing. More units keeps the lights on. If you can take the Mauser action from one business unit, improve it a bit, give it a nice fit and finish, do some custom work, then sell it under a more impressive name for a significantly higher margin, that's a good plan. I expect Rigby is the most reliably profitable of the big british names as a result, and probably the one posting the most rapid growth.
In the long term, I think Rigby will need to be extremely careful that doing so doesn't dilute their brand equity to a point where their brand is seen as lesser than say Purdey. In 20 odd years I think they might find themselves at a point where they're primarily a 'premium' mid-market brand who see a lot of sales in their bread and butter 'a bit more than a nice Mauser' 7-20k range, and rather less interest in their high end custom work as a result.
But for now, I expect it's proving to be a very profitable business decision.
