Case length different results

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Gabrile

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I started reloading and i just want to share my thoughts and results. I am looking forward for any feedback, experiences & ideas. I have many loads to be tested, I am heading tomorrow to the range again. Here are three loads, ALL the same with minor changes in case length & primer type, I wanted to see if it will give any difference. And it did! All used hornady SST 150 grain, H380 48 Grains. Case - remington. Distance: 100 yards. Tikka T3: 308



Load one: H380 - 48 GRAINS
Primer- Fedral.
Case length - 2010
OAL- 2740

MAX SPREAD 1.2
MIN SPREAD .153
GROUP DISTANCE TO CENTER .21
AVERAGE DISTANCE TO CENTER .55


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Load Two: H380 - 48 GRAINS
Primer- Fedral Match.
Case length - 2005
OAL- 2735

MAX SPREAD 1.737
MIN SPREAD .779
GROUP DISTANCE TO CENTER .340
AVERAGE DISTANCE TO CENTER .852


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Load Two: H380 - 48 GRAINS
Primer- Fedral.
Case length - 2005
OAL- 2735

MAX SPREAD 1.225
MIN SPREAD .319
GROUP DISTANCE TO CENTER .347
AVERAGE DISTANCE TO CENTER .581

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Maybe it's just me and I'm not trying to be critical but I don't read much into the various groups with the changes you made.

As an example, did the barrel cool down each time before groups, etc. I reload .308 and the biggest difference for me is bullet type (hornady 150 sst work well for me but Sierra match kings are better), exact consistent powder load to the nearest tenth or 100th depending on your scale, and powder type that hits the sweet spot of your rifle (47 grains of your powder may work better, or something else. Varget or IMR4064 is what I use), brass (lapua versus Remington...lapua will be better) and COAL differences not .005 differences but say 2.760 versus 2.735 or measuring 20 thousands off lands to the ogive as an example but that does depend on bullet type, magazine size etc.
I actually never tried doing different case lengths, I keep them all at 2.005 or 2.006 as I think the consistent measurement off the ogive matters more. Ymmv, many on thus forum have far more experience than I so perhaps they can chime in.
 
I got sierra match kings to try tomorrow with varget. I will see how things will go.

Yeah i used to leave the barrel cool down a little. There is not a huge difference with the overall results, (till now)
 
As above, I wouldn't consider the above trial to be significant. Your rifle shoots very well, well enough that you may now be the limiting factor in accuracy. Also, you need to let the barrel cool for several minutes, such that the barrel temp is constant between shots...
 
Good on you that you are reloading....adds a whole new fun dimension to the game doesn't it? Have fun but if you are trying to find some optimal loads you'd more likely find a good result, sooner by being more methodical and minimizing the variables that you are changing at one time. A new bullet is a whole new work-up.

There many good online sources of information on load development methodology (OCW, ladder, etc.).

If you are exploring OAL effects, you should determine your max. OAL and start maybe 10 thousandths off that length.

Nice groups for your first test...feels better than shooting Commercial ammo, eh!
 
Have you done any load testing to determine the velocity sweet spot? Normal practice would be to start with a minimum load and step it up in about 10 increments to maximum load and shoot different targets with each one. Measure the vertical only of the POI. You are looking for a range of velocities where the the powder charge and velocity increases but POI does not go up -- kind of stays flat. That is a good target velocity for your barrel. It is better to do this test at 200 meters than 100.

Next you could try varying seating depth. It is not normal practice to change case length. The minimum chamber length for a .308 is 2.025". I would trim to 2.020" and just keep them there. Let the shorter ones grow to that length.

Try not to change more than one thing at once. If I was starting with a 308 using a 155 grain I would choose:

Varget - Min 44 Max 47 (Find the velocity sweet spot by doing about 10 equal steps from min to max)
Primer - F210m
Bullet - Berger VLD 155 grain

But, whatever you pick for powder, primer, and bullet, stick with it until you identify the best velocity (powder charge), and second, the seating depth. Then move on to trying other tweaks... Just my thoughts.
 
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