Point of impact going up and left

[bluesj]

Hi all I've just started reloading for my 243, I made up some loads using 58grain V max and Hodgdon H4895. As today was the first day for ages there hasn't been a 30mph cross wind I thought it would be a good day to try them out, I fired 2 factory rounds to check zero then 4 of each load with cooling time in between.

As the load increased each group went up maybe 11/2" and left 3", is this normal or should I be looking for something else? I would have expected them to go up or down but wasn't expecting them to move so far to the left. I never had any more factory loads to check the zero.

[Dougy]

More work on load development I think.

[figgy]

As the loads get faster hold is becoming more of an issue at to you poi. When you work up to a load your happy with just re zero to that load and enjoy.

[Vince Green]

Its often the case that a different load will shift the POI to the left or right as well as up and down, that's just one of the mysteries of reloading. As long as its consistent that's the main thing then you can adjust it out. Its group size that matters.

 

You sound like you took reasonable precautions against the hot barrel 'syndrome'. Hot thin walled barrels most typically shift POI up at 45 degrees to the left or right progressively as the barrel gets hotter. You soon start to recognise that if it happens

Edited May 9, 2016 by Vince Green

[kent]

Could be so many things but it's not at all uncommon

In theory a barrel whips up and down in a vertical plain - but you know what a lot depends on a lot an inch is 1/60 of a single degree at 100 yards only

Don't fret over it. Pick the best and re- zero accordingly

[bluesj]

Cheers guys, that was what I was hoping to here just that the loads I did when being show what to the poi never changed much just the group size. Just fine tune the best now and see what happens

[kent]

Just an aside I don't pick off a few groups any longer

I look more to velocity variation over the chrono and consistent tight groups at the limits of range

[Walker570]

I must admit that these days if I reload some new shells and if they give me around a 1 moa result I don't play around too much but 25 -30yrs ago I went through a phase where I would load five sets of four a couple of grains apart or less and then set up a sheet with five targets. I would fire one shot from each set at it's specific target. Let the rifle sit a while, then the next five until I had worked them all down range. The exercise did show some incredible differences in points of impact and groupings. I never shot all four of each set in one go and never looked at the results until all had been fired. The climb effect I would have said was the barrel warming up, but you had this in mind. I had a very light barrelled 7x57 30yrs ago which would put the first two through the same hole but then began to climb up and left in one inch increments. Didn't worry me as the first one was the important one.

Pick the best group and go look for something soft and furry:-)

[Bangbangman]

Or try the OCW method.

[maxwell]

Or try the OCW method.

Works for me,

QL as a rough guide,

Run a few singles up to check primers,

OCW

Then fine tune with seating

Check throat wear every 100 rounds.

[Graham M]

Shoot low and right

 

G

[bluesj]

Shoot low and right

 

G

:-)

[bluesj]

I had heard of the ocw system but didn't really understand it so I've had a bit of a read up now all is clear, I'll be trying that over the week end

[Savhmr]

There's no great mystery to the OCW system. Someone recently asked me if I used it, and besides wanting to reply "how my wife and I conduct our family planning is our business! " I realised afterwards that I do use it, but just hadn't heard the terminology before.

 

Some say that load dev' is a black art, but I don't agree. There's a heck of a lot of variables and a lot that can (and does) go wrong, but once you start up that learning curve, it becomes addictive .

 

Taking the basics and starting with the desired terminal ballistic properties is where I normally start (ie what am I loading for and what are the characteristics I want from that bullet at that range, including accuracy, precision, penetration, expansion etc etc blah blah).

 

I then look to a powder that matches a selected bullet in that calibre that can deliver without excessive chamber pressure. One good way of spotting a marginal powder choice (which the Lee manual explains very well by the way) is to look at the sensitivity of pressure and velocity for a change of 1gr of powder. If the pressure becomes very peaky (some will increase 10% pressure per grain, cumulative) compared with velocity then that's a sure sign that there's a better alternative. Some powders you'll note from load data tables, give higher velocities for lower chamber pressures...this is a good thing.

 

Having said that, you sometimes have to go with what's readily available so it starts off as a compromise from the get-go. It requires then that great care should be applied to every step to maximise safety and precision. I know some that don't really care, and was told of one old fella, an old dear stalker, who for years just filled his cases with whatever he had to hand using a Lee Loader, until the powder reached the neck....surprised he's still with us!

 

The OCW system is simply one of finding the nodes for your rifle which correspond to the combination of a specific bullet and powder to give a specific "barrel time". The latter is simply the time taken from detonation of the round for the bullet to travel the length of the barrel and exit. You want this point to coincide with the node of minimum barrel deviation from on-axis for the most consistent approach, and for every round, there's usually a handful of those nodes achievable by varying seating depth and powder charge.

 

So what affects "barrel time" and barrel harmonics (especially the magnitude of barrel whip?). Well, the peak pressure/time curve will do that as will the seating depth for each bullet you use. There will usually be one or two optimum seating depths, and despite what's written on Tu't interweb, loading jammed onto the lands or 10 thou off is not a recipe for success every time...it just depends for that powder charge and bullet where it leaves the bullet exiting the rifle compared with the barrel node for that load.

 

Easiest and safest way is I've found (for those of us without "Quick Load") is to scour the load data tables and pick the highest suggested starting charge, and the lowest suggested max' charge, divide that number of grains by 5 and load a couple of bullets at each of those points.

 

Eg, if the max is 24g and the starting min is 22g, you have a 2g variance so a good place to start would be at 22gr and work up in 0.4gr intervals, ladder testing a single bullet at each load to check for pressure signs (stop if you get them and load up top the next node below). Then simply load a few at each of those weights and shoot each weight at a start of 10 thou off, then in jumps of 30 thou back to 130 thou off (but stopping where you start to compress the loads as few really compressed loads are a good idea or shoot as well as a nearly or just over full case).

 

You'll find for each load that the barrel time will become evident where it's on a node as when you get close, the bullets should be close to touching (providing your bore is in good nick and you can shoot straight!), and they spread very obviously as you move away. I do that for each weight and pick the best.

 

Quite often, in my 223 rifle, this equates to between medium low (say 40% the way up the load ladder) and perhaps 75% to 80% of max load at close on 100 thou off. It will be different for every rifle though. I'm not as obsessed as some about velocity. Loading hot seldom achieves the best results for me and my most accurate loads are well short of probably what I could achieve. Accuracy is what matters to me at the distance I want to be shooting at. better to be able to hit what you're aiming at and have confidence that you'll be precise, than have a so-so grouping but have the bullets skipping along at some hyper velocity, which will also help burn out the barrel a lot sooner.

 

Hopefully this helps rather than confuses...I'm still on that steep learning curve myself myself so happy to be corrected on anything above by those with more experience!

Edited May 13, 2016 by Savhmr

[lord_seagrave]

Pick the best group and go look for something soft and furry:-)

Walker, that is an important rule for life. You've got to have a system!

 

 

LS