I've a Parker Hale, .243. I believe it is the 1200 super. I am rather ignorant of the details of firearms (so please excuse any misuse of terminology), but the cartridges are short relative to the action and when the bolt is cycled, the cartridges tend to creep forward. If they creep forward, then the next cycle will usually cause a jam. It is my understanding that there may be a magazine box or some kind of keeper that can be installed to keep the cartridges snug to the back of the action. Thoughts/ideas/recommendations will be appreciated!