Long range load development at 100 yards.
- Thread starter Erik Cortina
- Start date
I asked about pressure because of the Palma brass which has more powder capacity than standard Lapua brass. I have always shot juggs at 2750 to 2775 fps. However I have never shot them in Palma brass.
If there is nothing up there, i would go with what you got.
If there is nothing up there, i would go with what you got.
memilanuk said:
Powder capacity might not be the correct way to state the difference. I haven't measured H20 capacity. To get a 200 hybrid to run the same speed, it seems to take about 1/2gr more powder in Palma brass than in Lapua .308 standard / large primer brass.
[br]Dos XX said:
I have measured capacity and Palma brass has ~.5 grain more capacity than Lapua standard .308, across several lots of each. In my chambers, Palma averages 55.7 and Palma 56.2. YMMV
Right for me as well. According my chamber my Palma brasses are 56.15 gr. of H2O.Steve Blair said:
I found my accuracy node with 200 Hybrids at 2800 fps
potatoe said:
??? Whats the load and how many firing do you get on your brass?
[/quote]
From 46.4 to 47.0 gr. of Reload Swiss 52 (it depends on temperature)
QL says 62.500 psi - The rifle is brand new, brass at third reload with still tight primer's pocket
memilanuk
Gold $$ Contributor
Huh. I've measured several lots @ 55.7-55.8gr... same as I got for large primer brass a few years ago. The really interesting bit was that one lot of Palma brass weighed ~173 gn... and another weighed ~175 gn.
I managed to reach a QL node @ ~2715, but lost >50% of the cases. Only people I know that are getting those kind of speeds without using new brass every match are doing some advanced coating processes.... moly + Hbn....
.308 lar-8 varmint. Seating test; 110 vmax, 49.5 gr xbr 8208. Groups start top left and go to the right
This target was charge weights, velocities are off due to not having screens over the chrono. These were also shot on a much warmer day, two days prior to the seating test. The vertical offset for 48.5=.229, 49=.263, 50=.265. For some reason I did not load up a 49.5 for this go round, but that is what looked to be the one to go with. I had no pressure signs but i was running out of case capacity, 50.5 is over listed maximum.
Any thoughts? Thanks.
This target was charge weights, velocities are off due to not having screens over the chrono. These were also shot on a much warmer day, two days prior to the seating test. The vertical offset for 48.5=.229, 49=.263, 50=.265. For some reason I did not load up a 49.5 for this go round, but that is what looked to be the one to go with. I had no pressure signs but i was running out of case capacity, 50.5 is over listed maximum.
Any thoughts? Thanks.
Erik Cortina
Team Lapua Brux Borden Captain
On first target, I would probably test load #6 further.
On second target, 49.0 gr. looks promising (it gets confusing after that).
On second target, 49.0 gr. looks promising (it gets confusing after that).
Erik, you like that sub 2 fps spread. The first target is seating depth of 49.5 from the second target. I did not upload them In the correct order.
The second target, with the scratched out bullsey was 50gr but i totally pulled the second shot and did not get back comfortable for the last shot, I walked away for a bit and finished the 50.5 (bottom right) then i reshot 50 gr (bottom right) 2 days later when the downpour subsided. I then chose the in between (49.5) due to the very slight vertical difference between 49 and 50.
Clear as mud?
With that attempt of explanation what do you reccomend?
Yes, since you asked, I do have some thoughts. You're on the right track using a scoring program to measure your targets. You can't make good decisions if you measure group size with a coin or carpenters tape, so congratulations on doing a good job measuring.
Unfortunately, you're trying to find meaningful answers from a pile of data which is so "noisy" (as they say) that it's hiding what you're looking for.
For example, I'm certainly no hot-shot and I'm older than dirt, but when I conduct a charge weight test at 100 yards with ammunition loaded at 5 or 6 slightly different charge weights, I expect to see ALL the 5-shot groups better than .700 MOA (or about .733" at 100 yards) and the good ones down around .300 MOA or better. The ATC numbers should be below .200 generally speaking and most closer to .100.
If you shoot 3 shot groups, these numbers should be even tighter. Unfortunately, your groups are so large that you will have difficulty deciding which seating depth or charge weight is the best.
In other words, you are searching for relatively small differences between the group size of a good load (or good seating depth) and a bad load, lets say a tenth of an inch or two for arguments sake. But if your test groups vary by more than an inch, you'll never be able to pick the fly s**t out of the pepper.
In my opinion, you're experiencing too much inconsistency for your test results to return any meaningful data. Unfortunately, there a plenty of potential reasons for this. Take a look at every aspect of your reloading technique, your equipment, and your shooting technique. Don't be afraid to ask for help at your local range. It could be something as simple as how you place your finger on the trigger.
And don't slack off on reloading. For instance, when I test seating depth, I weigh my powder to closer tolerances than when I load my competition rounds just so I can be SURE I'm not contaminating the results by introducing another variable.
I'd also recommend shooting 5 shot groups. The data you'll gather will be more meaningful.
Do what it takes to improve your consistency, which is more important than actually shooting small groups. Once you can shoot five or six 5-shot groups with good consistency using identical ammo, (even if the group sizes aren't real small), then you have a basis for testing variations in charge weight and/or seating depth.
Said another way, there is a valid reason NFL officials use a chain on their 10 yard down measuring sticks, rather than a bungee cord.
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