.17 hmr Accuracy

[Wasabi]

A few weeks ago I bought a batch of 400 rounds of .17 hmr. I re zeroed and got a 1.5" group at 100 metres. Normally I get .7" or so. I also missed some total sitters when out lamping. 

I therefore decided to measure the overall length of each cartridge (I've got a bit of time on my hands)! Anyway, turns out they ranged from 1.355 to 1.342 inches. 

Basically anything over 1.349 groups well, the shot er the length the wider tge group. Thankfully 356 out of the 380 left were over 1.350. It's now grouping back at .8 of an inch at 100 metres. 

Thought this might be of use to anyone having similar problems. Ammo is hornady 17 grain and the rifle is a cz 455 16 inch varmint. 

Edited April 17, 2019 by Wasabi

[Walker570]

Same set up/ammo and have not had any problems similar but purchased my shells twelve months ago.  ...Batch no ?????  mine says E24U01 on the bottom of the box which I am asuming is a batch number.  I have two boxes purchased at the same time and they have the same number.  Would be interesting to see if your boxes have the same number.

22RF used to give the same problems and still will. You needed to keep batches separate nd buy in bulk.  Had a friend who tipped about five boxes into a leather pouch and then wondered why he kept missing every other shot.

Just measured mine one out of each box at random both at 1.355  

 

If I might suggest 3/4 inch on a rabbit at 100 is not going to make his day.

Edited April 17, 2019 by Walker570

[Davetyler]

I noticed a few weeks ago that batch numbers make a big difference. Bought 500 with my gun happy with zero and a few rabbits later bought another 200 a couple of weeks later and couldnt hit a barn door, zero in again and perfect, after a lot of head scratching and a lot of swearing i realised that i was picking up different bullets each time i was out. 

Buy a batch and check zero 

I am confident in the rifle and myself now to hit a 10p at 100 yards