A STUDY OF FACTORS AFFECTING PRESSURE AND IMPACT OF BOLT IN RIFLE

Bolt was an important part for rifles which must be able to withstand pressure and
shock from using firearms. Therefore, material and hardness after plating must be able to
withstand both forces very well. This research had the objective to study joint influence of
variables that affected the bearing value for pressure and force of bolts in rifles and studied the influence of variables that affected the load of pressure and shock and compared the
difference of the load value of pressure and shock from the variables that affected the load
value of pressure and shock of bolts in rifles. The independent variable used in the comparison
study consisted of 3 types of materials including iron grade of SKD61, SKD11 and SCM440 and
variables after plating in 3 levels including 51 HRC, 54 HRC and 57 HRC. The test was according
to the test plan of Full factorial design by using the method of firing test by a rifle with 20-
inch barrel and ammunition of 5.56 mm for 30 rounds each and gathered the result of pressure
and shock value in every condition of test repeating number and then the results were
analyzed. From the test result, it was found that the variable of material type and hardness
after plating had not joint influence and there was only the influence of hardness after plating
that affected different load value of pressure and shock with statistical significance at the level
of 0.05. It was found that iron material grade SKD 61a the hardness value after plating of 57
HRC was the condition in producing bolts that could take the maximum pressure and shock.
From the research, it could be used as reference data in producing bolts to reduce the cost
and time for production from importing materials from another country and the test plan and
result analysis could be used with study and test of bolts in other types of firearms.