Load development .243AI

[menial 1]

I chronoed some rounds today to see what they were doing with the load that was most accurate. 44.5gr Viht 140, 70gr Blitzking.

The target was to be around 3600fps so I was quite pleased to find them running at an average of 3680fps, three 3 shot strings shot over the course of an hour to allow cooling between strings.

Then did the same with the deer/fox load that I use in .243 to fireform some brass for the Ackley, a fairly mild one and that was averaging 3300fps with 43.5gr Viht 160 and 85gr Sierra SP.

While I was waiting for the barrel to cool I shot a ccouple of strings of 105 A-max with 30.2gr of Viht 140 in my 6BR recording an average 2875fps with good accuracy, my reason for this was a discussion I'd had about temperatures affecting loads developed in the winter months and the rise in temp. in the summer and continuing with the same load. I deliberately left thre rounds out in the sun for an hour and then shot them, the results were a velocity gain of 70fps, a crap group and stiff bolt lift, so I imagine it goes without saying to keep ammo out of direct sunlight in the warmer months or some top end loads could prove troublesome.

Pete.

[eldon]

Wow 3680fps nice one.

We must be at the opposite ends of the spectrum as you are using 6 grains per shot more than me (non AI but same bullet). That 6 grains equates to 550 fps in these examples.

 

Surely AI the round won't make that much difference will it?

 

Might have to chase the speed up on mine a bit but it seem's pretty consistent and accurate as it is at the moment.

 

On the heat thing I have noticed the same outcome as your observations before. Just shows how many variables we are playing with all the time.

[1967spud]

just to add an alternative im getting 3260 with 46.5 grains of 4831 sc and a 87 g vmax

[menial 1]

Wow 3680fps nice one.

We must be at the opposite ends of the spectrum as you are using 6 grains per shot more than me (non AI but same bullet). That 6 grains equates to 550 fps in these examples.

 

Surely AI the round won't make that much difference will it?

 

Might have to chase the speed up on mine a bit but it seem's pretty consistent and accurate as it is at the moment.

 

On the heat thing I have noticed the same outcome as your observations before. Just shows how many variables we are playing with all the time.

 

I've been finding an extra 300fps over standard loads with the Ackley cartridge and the extra 5gr of powder used. Yes the Ackley is well worth the effort.

Pete.

[Grouse]

I chronoed some rounds today to see what they were doing with the load that was most accurate. 44.5gr Viht 140, 70gr Blitzking.

The target was to be around 3600fps so I was quite pleased to find them running at an average of 3680fps, three 3 shot strings shot over the course of an hour to allow cooling between strings.

Then did the same with the deer/fox load that I use in .243 to fireform some brass for the Ackley, a fairly mild one and that was averaging 3300fps with 43.5gr Viht 160 and 85gr Sierra SP.

While I was waiting for the barrel to cool I shot a ccouple of strings of 105 A-max with 30.2gr of Viht 140 in my 6BR recording an average 2875fps with good accuracy, my reason for this was a discussion I'd had about temperatures affecting loads developed in the winter months and the rise in temp. in the summer and continuing with the same load. I deliberately left thre rounds out in the sun for an hour and then shot them, the results were a velocity gain of 70fps, a crap group and stiff bolt lift, so I imagine it goes without saying to keep ammo out of direct sunlight in the warmer months or some top end loads could prove troublesome.

Pete.

 

What temperature day was this Pete? Also what length barrel you using with your 6mmbr?

 

With 105 Amax and 30.1gr N140 I am getting 2733fps out of 24" barrel on a 10 degree C day.

Most accurate load with N140 was 29.8gr getting 2714fps and 0.494" groups.

 

However to up the velocity went to Re15, 30.4gr gets me 2816fps and a 0.139" group this was shot at 20 degree C day (we do get warm days up here too!!!)

[eldon]

Edited, as I was talking crap when I re-read the posts.

[shrek]

Funny how your getting pressure signs with 30.2gr of N140 in your 6BR pete, im shooting the same bullet with 30.3 gr just now and 30.5 during the winter none of which show any signs of pressure, and im 10 tho into the lands! wierd stuff! I also chrony'd mine doing 2940fps which is alot quicker than what you and Nightwalker are gettin???? May need to set the chrony up again?

 

Didnt know you'd got an Ackley mate, im just in the process of thinking about getting mine built, was going to do it myself, but just havent got the time, so i may be askin you for load data in the near future

[menial 1]

What temperature day was this Pete? Also what length barrel you using with your 6mmbr?

 

With 105 Amax and 30.1gr N140 I am getting 2733fps out of 24" barrel on a 10 degree C day.

Most accurate load with N140 was 29.8gr getting 2714fps and 0.494" groups.

 

However to up the velocity went to Re15, 30.4gr gets me 2816fps and a 0.139" group this was shot at 20 degree C day (we do get warm days up here too!!!)

 

Hi Rich, the barrel is Pacnor 1in8 at 23". Temperature was around 80 degrees Fahrenheit the day I chronoed these loads, also found a similar accuracy node at 29.2gr Viht 140. I sometimes wonder if the cases expand a thou or two at these higher temps. and with the 105's seated into the lands does this create a little more pressure and velocity. Quite happy to be told I'm talking cobblers, it's just something I've noticed at this time of year.

Have checked the chrono (CED Millenium) against another and everything seems okay in that department.

Pete.

[menial 1]

Funny how your getting pressure signs with 30.2gr of N140 in your 6BR pete, im shooting the same bullet with 30.3 gr just now and 30.5 during the winter none of which show any signs of pressure, and im 10 tho into the lands! wierd stuff! I also chrony'd mine doing 2940fps which is alot quicker than what you and Nightwalker are gettin???? May need to set the chrony up again?

 

Didnt know you'd got an Ackley mate, im just in the process of thinking about getting mine built, was going to do it myself, but just havent got the time, so i may be askin you for load data in the near future

 

Hi William, I'm sure that on more temperate days the pressure signs will disappear. Don't do an Ackley, it's costing me a fortune fire forming brass.

There's nothing safe on the estate at the moment I'm that keen to have a decent amount of brass fire formed to avoid shooting the same cases over and over.

I should have done this years ago, 70gr 6mm bullets at 3680fps, definitely the way to go.

Pete.

[Berger]

my 243 AI runs at 3770 with a 68gr pill Ive had it up to 3825 but a litle too hot

[menial 1]

Ran it a bit hotter and the groups opened up, so settled for 3680fps average with 44.5gr Viht 140. Pressure signs at 45 and 45.5gr. My barrel is only 22" so I think I've reached a reasonable velocity with sub 1/2moa accuracy.

Pete.

[devilishdave]

menial 1

 

Have you worked any heavier loads for your Ackley? Mine is also 22 inch so would be interested to here what results you got.

 

Dave

[menial 1]

I have some 105 A-max, 85 Sierra SP and 90 Bergers to play with. Now I've got a hundred plus cases fire formed it will allow me to have a tinker with some heavier rounds. I'll post the results as and when they happen Dave, shouldn't be long, I'm a curious child at heart.

 

To be honest the 70gr Blitzking has been demolishing everything it's made contact with and I'm going to stick with this as a working load at the moment.

No holdover out to 250yds makes it very tempting not to bother with further experiments, but I'm going to anyway, you just can't help yourself when you get new toys.

My problem is that my 6BR is the dogs during daylight dialling with 105 A-max on long range crows and bunnies and the .243AI does exactly what I had in mind for it, tipping over fox at night with 70 gr bullets, tempted to run lighter bullets for even flatter trajectory but barrel longevity becomes a concern.

Should have some of the heavier rounds loaded and tested before the weekend as I'm off work at the moment, just need a little improvement in the weather to make testing a worthwhile excercise, and keep my plaster dry or suffer the wrath of her indoors, I knackered the last one putting nets on some runs for the pheasant poults, so I'm under scrutiny at the moment, (she's a ward sister so I can't easily pull the wool over eyes on medical matters).

Pete.

[1967spud]

have you tried the 87 vmax yet

[menial 1]

I haven't got any Mark, they're reckoned to go really well in 6BR so when I see some I'll try a box in both rounds to see if all the hype is true.

I've run two 6mm rifles in tandem for a long while now and with 500 rounds allowance for expanding on each you tend to accumulate a fair number of bullets to trial without having to buy anymore, if you see what I mean.

Accuracy wise, any of the 6mm rifles I've had have always performed best with Bergers when shooting groups, but not always giving the best downrange results on fur or feather.

Pete.