Q I’ve had my Zastava Mauser rebarrelled in .284 Winchester and asked the gunsmith to lengthen the throat, like your BSA Royal’s chamber. I used a Stoney Point/Hornady overall-length (OAL) gauge to check maximum length with a given bullet and found the distance to the rifling to be about .050 inch (1.3mm) longer than the listed maximum OAL in my reloading manual, but this is not a problem with my rifle which has a .30-06 length magazine.
My queries are: can I use heavier than maximum loads because of the additional case capacity I gain by seating bullets farther out? Will being free-bored affect accuracy much?
Paul Michaels
A Reloading for my old BSA, the maximum cartridge OAL was 3.1 inches (78.7mm) and my favourite deer load was a 140gn Barnes X and 62gn of WMR for 3003fps (915m/s).
My load for ferals was the 130gn Speer over 59gn of IMR 4831 for 3130fps (954m/s) and that load took a record-book tahr in NZ.
As a rule, you can increase powder charges by a couple of grains in a long-throated rifle, but it pays to always approach maximum loads listed in manuals with caution. Problems can arise if you happen to have a ‘tight’ barrel, one that was reamed, rifled and chambered to minimum SAAMI specifications.
Your Mauser magazine and long chamber will allow you to seat to longer than specified OAL, but use your Stoney Point/Hornady gauge and try seating bullets to just miss touching the lands; don’t seat them so far out that they engage the rifling.
If your rifle is happy with bullets seated long, work up the powder charge carefully.
That said, I’ve owned and still own three long-throated rifles that produce an extra 100fps (30m/s) together with excellent accuracy.
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