Reload­ing – Part 3

Sporting Gun - - NORTHERN NOTES -

Last month I cov­ered the process of reload­ing the cas­ing. So at this point we have sev­eral rounds com­plete and we have ze­roed the ri­fle at 100m. The next and fi­nal task is to find out the speed of the bul­let through the ri­fle.

With fac­tory am­mu­ni­tion, there is of­ten a bal­lis­tics chart ei­ther printed on the box or in­side. The chart gives the speed (ve­loc­ity) of the bul­let and the en­ergy (force). The in­for­ma­tion will of­ten also give the tra­jec­tory. Tra­jec­tory is the path of the bul­let in flight at var­i­ous dis­tances. This is mea­sured at the fac­tory un­der con­trolled con­di­tions. Dur­ing the flight of the bul­let, both the ve­loc­ity and en­ergy de­crease de­pend­ing on the dis­tance the bul­let has trav­elled.

Both the speed and the en­ergy of the bul­let are im­por­tant. They are usu­ally mea­sured on exit of the muz­zle and for shoot­ing deer in the UK there is a le­gal min­i­mum ve­loc­ity and en­ergy that the bul­let must pro­duce.

In Eng­land and Wales it is 1,700ft/ lb of en­ergy and 2,450ft/ sec ve­loc­ity. In Scot­land the en­ergy is higher at 1,750ft/lb, but the ve­loc­ity is the same. I won’t go into the whys and where­fores here, but in Scot­land the le­gal min­i­mum bul­let weight for deer other than roe is 100 grain. The min­i­mum bul­let weight in Eng­land and Wales is 50 grain for shoot­ing munt­jac and Chi­nese wa­ter deer. I al­ways stick to 100 grain for roe and use heav­ier rounds for the larger species.

Hu­mane despatch is what we are all look­ing to achieve and the en­ergy of your cho­sen round needs to be ad­e­quate enough to en­able that.

To mea­sure the speed of your bul­let ex­it­ing your ri­fle it is nec­es­sary to get hold of a chrono­graph. Many ri­fle clubs have them, if you do not have your own or you may know some­one that is will­ing to help.

Set the chrono­graph up as the in­struc­tions state and fire three rounds through the guides mark­ing the speed of each round af­ter each shot. It is very likely they will be dif­fer­ent, hope­fully you have taken care to load ac­cu­rately and the speeds will not dif­fer by much. Add the to­tal speeds to­gether and di­vide by the num­ber of rounds you have fired to get the av­er­age speed of the bul­let ex­it­ing your cho­sen ri­fle. A word of warn­ing here, en­sure that your line of fire will pass in be­tween the guides and not de­stroy the whole kit!

Once that is done then go to the In­ter­net and check the bul­let man­u­fac­turer’s bal­lis­tic in­for­ma­tion for the bul­let you are us­ing. This will give you a bal­lis­tic co­ef­fi­cient of the bul­let at the speed it is trav­el­ling. From there the tra­jec­tory of your bul­let can be worked out for the vari­able ranges you are fir­ing at.

My re­sults were:

Bul­let speed: 2,740 ft/sec or 836 mps. Bal­lis­tic co­ef­fi­cient = .501

Us­ing the Swarovski Op­tik bal­lis­tic app this gives the fol­low­ing data for the Swarovski Z6i

Ze­roed at 100m:

150m the drop is 3.47cm = 2 clicks high. 200m the drop is 11.35 cm = a fur­ther 4 clicks high.

250m the drop is 23.99 cm = a fur­ther 4 clicks high.

300m the drop is 41.79 cm = a fur­ther 4 clicks high.

This was all achieved us­ing the max­i­mum load for the Hodg­don H414 pow­der, which pro­duced a per­fectly ac­cept­able group­ing on the tar­get.

If I want the group to be even tighter then fur­ther ex­per­i­men­ta­tion will be nec­es­sary with ei­ther the seat­ing depth of the bul­let, the quan­tity or type of pow­der loaded or both.

Hor­nady Lock N Load equip­ment was used through­out this se­ries.

Mea­sur­ing the ve­loc­ity of your bul­let to see if it is le­gal for deer re­quires a chrono­graph

If you’ve done a good job the bul­let speeds will not vary much shot-to-shot

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