Thread: ballistic calculator's can be wrong

Originally Posted by grandpamac

I often wondered if the difference came from throat erosion. Measuring the crush length for 174 grain RN was around 6mm longer on a used but in good condition barrel than two near new barrels. I still have to chronograph the same load to see how much difference this makes.
GPM.

one would think it would have been the opposite, Would be interested in your results, gotta love the ol 303

Originally Posted by Hbwanderer

@grandpamac, the load was 44grns of Varget pushing 150grn Winchester powerpoints,Used those because i have heaps of them, Dont get me wrong i was happy with the grouping (2inches @50yrds) 50 yrds will be a long shot for the bush i hunt.
My whole point for the thread was online calculators and real world results sometimes can be complete opposites, and yes the rifle is new to me but was in a sad state when i came across it,it had had a hard life,Made circa 1960, the throat is more than likely worn as i had to cut 2 inches of the barrel (muzzle end) before i found any decernable rifling,

Ballistic calculators make a lot of assumptions and can be well wide of the mark. I prefer to use tested data together with a chronograph for load development. One thing that I have noticed with data for the .303 is that it varies widely with pressure tested data giving considerably higher velocity than that from Lee Enfields. I often wondered if the difference came from throat erosion. Measuring the crush length for 174 grain RN was around 6mm longer on a used but in good condition barrel than two near new barrels. I still have to chronograph the same load to see how much difference this makes.
GPM.

Originally Posted by 6x47

At 50yds with a .308 shooting mid-weight bullets with a sensible load of 2208, they should be shooting way sub-inch. Is the barrel/crown very tired or possibly pitted? Has someone looked down it with a borescope- could well be badly fouled? Is the bedding sus? Ballistic considerations would be waaay down the list for me.

No borescope inspection as posted earlier the barrel was shortened and recrowned,the rifling is worn but present no idea about the throat may do a casting,the grouping is partly due to nutt behind the butt.

ok...find some speer flat base to try..they are softer than most and very good at finding what rifling is left...
the .308w is very good at being easy to get to work.
hornady also make a VERY VERY good 180grn round nose projectile,which is still available around the shops...I just poked some on top of a middle of range load of powder and went hunting...for bush ranges we dont need to get too pedantic.I used that projectile as terminally it was nearest I could find to what the winchester factory stuff does,open up fast and still retain a bit of weight because its big to begin with LOL...
2" at fifty yards is open sight sort of group..and not overly good even then...heck some smooth bores will do that.it will get you your deer alright right up until you see one at 125 yards,when its getting very dodgy.
if you suspect the nut behind the butt...get someone else to try it...
you say youve docked barrel...has crown been tidied up of is it still showing hacksaw marks??? also if not suppressed double up ear protection and give that a go... big loud blasting noise is not conductive to fine shooting.

@Micky Duck the barrel was shortened in a lathe and re crowned, my mate who was with me at the range had no problem hitting a 4inch gong @100yrds hence the nut behind the but remark

oh well that rules that one out....LOL
round nose pills rule supreme for out right smackdown....must be something to do with starting to open faster or pushing more stuff to begin with..but they just work,always have and always will.

Originally Posted by Micky Duck

oh well that rules that one out....LOL
round nose pills rule supreme for out right smackdown....must be something to do with starting to open faster or pushing more stuff to begin with..but they just work,always have and always will.

how will they go with 1;12 twist? only one way to find out cant count on online calculator's

in theory they should be fine...overall length is shorter being round nose.

Originally Posted by Micky Duck

in theory they should be fine...overall length is shorter being round nose.

will source some and report back

if you cant find any...get in touch. still a part box sitting in my reloading stuff.