Complex sentence: This allows long barrelled target rifles to use large powder loads with slow burn rates to keep the pressure in the barrel at its maximum capacity while the round accelerates to extreme velocity while maintaining constant angular momentum for stability.
Split into simpler sentences: This allows long barreled target rifles to use large powder loads with slow burn rates to keep the pressure in the barrel at its maximum capacity. This in turn accelerates the round to extreme velocity while maintaining constant angular momentum for stability.