308 / 200.20X load results question

[Linko]

Hi,

working the 200.20x loads on my 30" 1/10 bartelin F TR rifle. chambered for 200.20x and 185 jug.

Varget / GM205M / Lapua @ .015 off . ES @ 43.6 is better but groups are better at 43.4

velocity for these is between 2620 & 2660 aprox I understand this is a good window for this bullet.

I will say mirage was bad at 200, so my aim was a little off.

could use some advice

 

[Acyr]

I would be trying 43.2 and see if 43.4 repeats.

 

[Zero333]

43.4 is great.

Try 43.2 to see if it's also as good. If 43.2 and 43.4 are equally as accurate then load 43.3 and be done.

 

[memilanuk]

I will say mirage was bad at 200, so my aim was a little off.

could use some advice

Here's my advice: if the conditions are crap, stop testing.

Find a different time of day when the conditions are better, and plan another trip to the range. Otherwise, you'll spend a lot of time and money chasing your tail.

 

[Linko]

Here's my advice: if the conditions are crap, stop testing.

Find a different time of day when the conditions are better, and plan another trip to the range. Otherwise, you'll spend a lot of time and money chasing your tail.

Yes conditions need to be good.

My underlying question is the ES and the relationship to the group size.

43.6 has the lowest ES but 43.4 is the best group at 100 and 200.

I have been told the 200.20x bullets sweet spot is 2230 to 2260. 43.6 hits that range right in the middle, I had 2642 with ES of 10.

should I chase seating depths at 43.6 or loads around the 43.4(43.2 - 43.3)

 

[Bc'z]

43.4 is great.

Try 43.2 to see if it's also as good. If 43.2 and 43.4 are equally as accurate then load 43.3 and be done.

 

[Linko]

Thanks

 

[dcali]

A few things: only the 43.4 groups are competitive. You can safely rule out the higher charges. 43.4 looks good, but it's awfully close to a not very good 43.6. I would check 43.0 and 43.2 before doing seating depth tests near -.015. Check jammed if you're so inclined.

As for your actual question, never develop a load based on velocity variation. It's simply not a reliable indicator of accuracy. It's rare that a 100 yard load won't shoot well at 600/1000. If it doesn't, try a ladder test at that range. In my opinion, there isn't a good reason to even look at velocity unless your'e seeing a problem at 600/1000 that isn't showing up at 100. Also, your velocity SDs aren't going to get any tighter. They're all plenty good, although to get a better picture you should combine the shots from the two groups.

Edit: I'm assuming conditions did not materially impact your group size. As others said, don't waste ammo testing on crap days.

 

[memilanuk]

My underlying question is the ES and the relationship to the group size.

...and my point was that if the conditions are crap to the point where your ability to hold is compromised, the group sizes are irrelevant.

You're trying to read tea leaves, divining some meaning out of random noise. Don't.

 

[Down South]

...and my point was that if the conditions are crap to the point where your ability to hold is compromised, the group sizes are irrelevant.

You're trying to read tea leaves, divining some meaning out of random noise. Don't.

This^^^^^^^^^^

 

[ballisticdaddy]

IMO the seating depth testing is just as important, you might want to factor that in as well

 

[Ned Ludd]

Charge weight testing is primarily to optimize combustion and minimize ES/SD, not necessarily to find the smallest group. That is what seating depth testing is for. My load with the 200.20Xs tuned in pretty much exactly where Linko's appears to. I settled on 43.5 gr Varget at ~2640 fps. My groups at .015" off were not spectacular. However, they tightened up to one ragged hole at .009" off, and to a lesser extent at .012" off. Trying to use group size or position (OCW testing) to distinguish a difference between a tenth grain or two of powder in a charge weight is not easy, although there is nothing wrong with using it as a secondary factor to decide between different charge weights.

For an F-TR load, minimal ES/SD is desirable to help minimize velocity excursions over the long strings (20+ shots) of fire. The groups can be tuned in tight afterwards using seating depth. Alternatively, a coarse seating depth test can be carried out initially using a charge weight at the lower end of the expected test range, in order to find a seating depth region the bullet/rifle likes before going to charge weight testing. But it is still a good idea to carry out an additional fine increment seating depth test after the optimal charge weight has been chosen. In my hands, that's when I see the groups really tighten up...not so much during initial charge weight testing.

 

[B Nettesheim]

Your target and your score sheet do not care about sd or es numbers, chase that nice round group as that will be the most beneficial when the center of the target decides not to hold still!!!

 

[davidjoe]

Hi,

working the 200.20x loads on my 30" 1/10 bartelin F TR rifle. chambered for 200.20x and 185 jug.

velocity for these is between 2620 & 2660 aprox I understand this is a good window for this bullet.

I wonder if the results would differ if you reversed the testing order of the loads, or if you shot loads 1 through 3, in 5 separate strings of three shots each, so as to take mirage or barrel heat differences out of the comparisons.

You cite a great target window for brass life but the bullet itself is not going to have an inherent best-accurate speed down in that 2,600-something area, only the barrel’s harmonics will, as your .308 rifle is simply snipping about the first 400 yards off the trajectory line of the exact same bullet from a 300 win mag., 600 yards from a much bigger mag, and so forth.

 

[rardoin]

Here's my advice: if the conditions are crap, stop testing.

Find a different time of day when the conditions are better, and plan another trip to the range. Otherwise, you'll spend a lot of time and money chasing your tail.

Some people have found out the hard way...like me. But, it has kept FrankG in business.... Nothing like having expended 600 rounds to find a great load and that the barrel is a real shooter....on a chambering/bullet/speed with about 1800rd barrel life. Guilty as charged.

 

[D-4297]

My summer load for the Berger 200 Hybrid , and the 200.20x is 43.3 and winter ( below 70F ) is somewhat higher . Quite a bit higher , in fact . You're in the ball-park , but I wouldn't obsess over SD/ES numbers to much . I've gotten some of my best scores with totally ugly numbers , and some of my worst scores with single-digit SD/ES . As Ned Ludd said , they are a guide to establish consistency . Not the Holy Grail . Re-read all the posts here regarding group sizes and consistency . Lots of solid information and direction in those posts .