bullets hitting low??

hey guys
i have a problem that happens every now and then
i get one or 2 rounds that hit low see pic


was trying to do some load testing at 200m to find seating depth on 108gr berger BTs , wind coming from behind and from left to right but it was only light, no mirage done in the late arvo

the .021 off the land it was the 2nd and 4th round that hit low , the .024 off the 4th round was the one that hit low
is the problem me or is it the loads , the  group of 4 at .024 measures half an inch

should i redo and shoot again  

Hi mate i suspect that the difference in bullet impact can be attributed to two possibilities.

One- you said that the wind was coming from behind you which pushes the bullet up so if you fire in a "pocket" of no wind the bullet will be low this can happen at varying times. Wind follows a wind cycle so this event can happen multiple times.

Best to do load development with no wind or a constant wind from one direction right to left as you are looking for vertical dispersion not how wide it is.

Two- you may be gripping the rifle or the rear bag is moving from it's original position in some time in your string of shots.


When i do a load development i shoot four shots fast then discount the one shot out of the group and measure three for vertical only that is the load i choose.

cheers hope this helps
Les

cheers Les
yeah wind this time of year is bad our way .. lucky to get a windless day and when it happens I'm working or the Mrs has me doing stuff haha
I'm only using my finger on trigger and thumb behind my pistol grip
more than likely it is my bag moving now that you mention it as I had to adjust it about that time (was getting close to 50 shots fired and if I let my gun free recoil to much the pistol grip pushes my bag back)  
might just load some up at .021 and .024 and do them again, might even go .027 also

actually I might even take the pistol grip off and shoot a few rounds like that and see how it goes, why didn't I think of that earlier

cheers
pethy

Glad to help mate, just be careful changing to much like taking your pistol grip of of adding taking things off and on.

Rifles have a harmonic and the accuracy Node you are achieving is based on the whole rifle package so when you change things your loads may or may not be effected but in any event you have to shoot them exactly how you have tuned your rifles.

I see so many people have a scope on their rifle tune it up then when they can afford it they buy a new one and the weight is different or the centre of balance is out and they are lucky to hit the ten ring once  a day. Then i hear them say there is something wrong with my rifle and yes there is they have changed the rifles harmonics.

Anyway keep at it i shoot all my rifles 5" off the lands and achieve better results by adjusting neck tension and length of crimp from the die button. A lot of really good rifles have been claimed to have been shot out only to be purchased by another hand loaded and redone the the brass and different neck tensions then all of a sudden it is shooting again. Bore scopes are the real test if rifle barrels are finished or the group centre starts to release.

cheers Les

ahh yes didn't think that would change it much but you are right there, will leave pistol grip on for now
I do know my rifle is front heavy with the 30inch barrel on it
might try adjusting neck tension . im running .001 atm (will try .002)  and I have never really played with the how much of the neck gets tension by my bushing die , its set up to adjust nearly all of the neck, say 3/4 for it maybe a touch more
might try only sizing half the neck and see if that makes any difference

I also took it to Dave Kerr the other day and he check it with the bore scope and said its showing signs of wear in the throat , there were a few cracks but nothing really bad yet , it has now done 1900 rounds and I'm tossing up whether to get the Hart blank I have chambered for it and make the 6BR barrel on it rechamberd into 243 for my hunting barrel.
that way I will have a new barrel for the national
Daves words were if it was me I'd would replace it, but then he said its my job to sell barrels ..haha

cheers
pethy

In relation to neck tension i use 3 thou and size just over half way and all of my rifles. Remember that neck tension drops about a 1 thou per week. So in theory if you have only 1 thou and you shoot that day then all is reasonably Ok however i wouldn't leave them in the sun or you will have NO neck tension.

As far as barrel wear goes yep a bore scope is the way to go as for barrel life i use the group to identify how things are going such as the group starting to hollow or become unstable with throwing shoots out with little explanation over a couple of shoots.

Reloading is a challenging element but very rewarding at the same time, you really do get out of it what you put in....

Cheers Les

G'day Stuart,
Got to agree with all that Les advises….you did say you might go out to .o27 off & I'd be doing that 1st as it looks to me like you have a pattern developing.
 .o18 was everywhere,
.021 was 3 & 2 out,
 .o24 was 4 & 1 out.
 I'd gamble that .027 or even .03 off  will cluster them up providing (as Les says) that everything else remains the same!

Regards,
Belly

cheers Belly
will make some loads up and test
thanks