Posted: 4/5/2016 7:47:50 PM EDT
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I shot five 5 shot groups. Out of these groups what load would you choose? Should I condunct another study between or around any of these loads? I had the rifle on sand bags on the bench. I'm new to sharp shooting and reloading so I believe the biggest variable is myself, and I'm working on that.
Heres the report: Rifle: Ruger RPR .308 Scope: Weaver 1.5-6x32 Bullet- 175gr Sierra Matchking BTHP Powder- IMR 4064 Brass - Hornady Match Primer- CCI #200 Weather: 40 degrees overcast 20mph wind 1 o-clock 20% 1030hPa 1000ft Bore: 60 rounds total, 40 since clean. Setup- Sandbags and bench. 
Load 1 (41.8gr) 2463 (CB) 2507 2501 2497 2555 Ave= 2505 SD= 33 
Load 2 (42.0gr) 2516 2496 2502 2543 2518 Ave= 2515 SD= 18 
Load 3 (42.3gr) 2532 2523 2511 2547 2568 Ave= 2536 SD= 22 
Load 4 (42.6) 2555 2571 2565 2598 2600 Ave= 2578 SD= 20 
Load 5 (42.8) MAX 2599 2610 2581 2637 2574 Ave= 2600 SD= 25 
My sizing die was set up so that when I chambered a sized piece of brass the body of the bolt would almost fall closed. All charges were trickle measured. All bullets were seated to a COAL of 2.800" +or- 0.010". Any help or suggestions would be much appreciated. Thanks. |
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Quoted:
Thanks, I'll have to look up what exactly a ladder test is  . I'll change the title. I'm thinking I'll try another study from 42.2-42.8!
Quoted:
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this is not a ladder test but... Load 4 (42.6) 2555 2571 2565 2598 2600 Ave= 2578 SD= 20 looks best and best SD Thanks, I'll have to look up what exactly a ladder test is . I'll change the title. I'm thinking I'll try another study from 42.2-42.8!
http://www.6mmbr.com/laddertest.html best example of an extreme ladder test, great read. -edit- im in a helping mood tonight... you mentioned all bullets seated to COAL length of xxxx, you dont want to seat to a set COAL. you need to measure to the ojive of the bullets, it is much more consistent due to how the bullets are manufactured. If you are concerned with OAL for magazines, then measure a large sample (5 or more) from your box of bullets and determine the LONGEST of the group. Use the longest bullet and seat based on the ojive to meet your OAL criteria, then you should never have a bullet longer than this and still all be seated to the same "position". Remember, like a piston in a car...the magic is happening between the primer and the base of the bullet, that is the length you want consistant. Good luck! your off to a good start. |
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Quoted:
http://www.6mmbr.com/laddertest.html best example of an extreme ladder test, great read. -edit- im in a helping mood tonight... you mentioned all bullets seated to COAL length of xxxx, you dont want to seat to a set COAL. you need to measure to the ojive of the bullets, it is much more consistent due to how the bullets are manufactured. If you are concerned with OAL for magazines, then measure a large sample (5 or more) from your box of bullets and determine the LONGEST of the group. Use the longest bullet and seat based on the ojive to meet your OAL criteria, then you should never have a bullet longer than this and still all be seated to the same "position". Remember, like a piston in a car...the magic is happening between the primer and the base of the bullet, that is the length you want consistant. Good luck! your off to a good start. Quoted:
Quoted:
Quoted:
this is not a ladder test but... Load 4 (42.6) 2555 2571 2565 2598 2600 Ave= 2578 SD= 20 looks best and best SD Thanks, I'll have to look up what exactly a ladder test is . I'll change the title. I'm thinking I'll try another study from 42.2-42.8!
http://www.6mmbr.com/laddertest.html best example of an extreme ladder test, great read. -edit- im in a helping mood tonight... you mentioned all bullets seated to COAL length of xxxx, you dont want to seat to a set COAL. you need to measure to the ojive of the bullets, it is much more consistent due to how the bullets are manufactured. If you are concerned with OAL for magazines, then measure a large sample (5 or more) from your box of bullets and determine the LONGEST of the group. Use the longest bullet and seat based on the ojive to meet your OAL criteria, then you should never have a bullet longer than this and still all be seated to the same "position". Remember, like a piston in a car...the magic is happening between the primer and the base of the bullet, that is the length you want consistant. Good luck! your off to a good start. Wow, good read indeed. I'll give that a try! This is fun, I feel like a scientist. Guess I'll pick up one of those ojive deals for my calipers. Thanks for the tip! ..or is it ojive?! 
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Would have been easier if all targets were visible in ONE photo . . . OCW looks at similarity of POIs, not microscopic examination of the groups.
42.6-42.8 have similar POIs. Though they aren't perfect, they look like a good area to explore further. Then things change and scatter a bit as you look at reduced charges . . . until 41.8gr where the group comes back together.which may be the top of (or the actual) lower accuracy node. The distance between them is closer than I'd suspect, so . . . I'd first explore 42.8 and up a bit (Hodgdon says max is 45.6C) assuming you saw no pressure signs and want the velocity. If you can't or don't, I'd explore 41.8gr and down a bit. You only tested a 2.4% variation in powder charge weights . . . sometimes you will be in between the real nodes miss real nodes which are more likely 3% apart. My guess would be you are in between. ETA: Unless you're intentionally looking for very soft practice loads, Hodgdon's reload data suggests only checking increased powder loads. |
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I agree with Twoboxer, your charge weights are pretty close to each other, and you only tested over a total of 1 grain of powder weight.
That being said, you are dancing around the charge weight that most find to be "the one." (Google Sleuthing FGMM.) The good news is that you have a chronograph. It can be more helpful than your targets if it is working correctly. Groups that have good chrono data but group poorly can sometimes be tightened up with seating depth changes. I like to shoot a ladder test over a chronograph increasing charge weights by roughly 7% (0.3 grains in 308 cal). I use the ladder to establish the max charge in my gun. I also shoot this over a chronograph to monitor velocity changes. Sometimes nodes will appear as very small changes in velocity between charge weights. And I often find large jumps in velocity indicating I have reached my max before the brass shows pressure signs. I then back down 10% from my max charge weight and begin my OCW loads, again increasing charge weights by 7%. I shoot the OCW over a chronograph at targets that are in a line so I can see POI shifts better. I trust my chrono data more than the targets when looking for nodes, but 9 times out of 10 they are the same. The nodes on the targets are not necessarily the best groups, but those groups with minimal change in POI. Once I find my powder charge weight node, I do a seating depth test to find my final load. It may difficult to work up a load for the RPR since they are such good shooters. Your groups will all look pretty good (they already do)!! Focus on ES, variance in velocity between groups and POI on the targets. Hope that helps and good luck! |
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The testing you ran is fine, but it isn't an OCW or Ladder. By now you have seen the articles on Ladder and OCW.
You probably don't need to run one unless you plan on going out to distances that use most of the sonic distance. Your testing is showing promise at the distances you are using, so maybe you should try and optimize as is. Unless you are really trying to get out past 400 yards on a regular basis? |
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Quoted:
Would have been easier if all targets were visible in ONE photo . . . OCW looks at similarity of POIs, not microscopic examination of the groups. 42.6-42.8 have similar POIs. Though they aren't perfect, they look like a good area to explore further. Then things change and scatter a bit as you look at reduced charges . . . until 41.8gr where the group comes back together.which may be the top of (or the actual) lower accuracy node. The distance between them is closer than I'd suspect, so . . . I'd first explore 42.8 and up a bit (Hodgdon says max is 45.6C) assuming you saw no pressure signs and want the velocity. If you can't or don't, I'd explore 41.8gr and down a bit. You only tested a 2.4% variation in powder charge weights . . . sometimes you will be in between the real nodes miss real nodes which are more likely 3% apart. My guess would be you are in between. ETA: Unless you're intentionally looking for very soft practice loads, Hodgdon's reload data suggests only checking increased powder loads. Quoted:
Would have been easier if all targets were visible in ONE photo . . . OCW looks at similarity of POIs, not microscopic examination of the groups. 42.6-42.8 have similar POIs. Though they aren't perfect, they look like a good area to explore further. Then things change and scatter a bit as you look at reduced charges . . . until 41.8gr where the group comes back together.which may be the top of (or the actual) lower accuracy node. The distance between them is closer than I'd suspect, so . . . I'd first explore 42.8 and up a bit (Hodgdon says max is 45.6C) assuming you saw no pressure signs and want the velocity. If you can't or don't, I'd explore 41.8gr and down a bit. You only tested a 2.4% variation in powder charge weights . . . sometimes you will be in between the real nodes miss real nodes which are more likely 3% apart. My guess would be you are in between. ETA: Unless you're intentionally looking for very soft practice loads, Hodgdon's reload data suggests only checking increased powder loads. I see what you're saying! I should have tested a broader range of charge weights. I saw no pressure signs at 42.8, and I stopped there because Sierra Load data suggests 42.8 max. I will proceed with caution and find a practical maximum weight as described in the 6bmmr article. From what I've read about other's results with 20" barrels and this load combination I should expect nodes somewhere around 41.9 and 43.1, which would leave me sort of in between as you stated! Thanks, Twoboxer! Quoted:
I agree with Twoboxer, your charge weights are pretty close to each other, and you only tested over a total of 1 grain of powder weight. That being said, you are dancing around the charge weight that most find to be "the one." (Google Sleuthing FGMM.) The good news is that you have a chronograph. It can be more helpful than your targets if it is working correctly. Groups that have good chrono data but group poorly can sometimes be tightened up with seating depth changes. I like to shoot a ladder test over a chronograph increasing charge weights by roughly 7% (0.3 grains in 308 cal). I use the ladder to establish the max charge in my gun. I also shoot this over a chronograph to monitor velocity changes. Sometimes nodes will appear as very small changes in velocity between charge weights. And I often find large jumps in velocity indicating I have reached my max before the brass shows pressure signs. I then back down 10% from my max charge weight and begin my OCW loads, again increasing charge weights by 7%. I shoot the OCW over a chronograph at targets that are in a line so I can see POI shifts better. I trust my chrono data more than the targets when looking for nodes, but 9 times out of 10 they are the same. The nodes on the targets are not necessarily the best groups, but those groups with minimal change in POI. Once I find my powder charge weight node, I do a seating depth test to find my final load. It may difficult to work up a load for the RPR since they are such good shooters. Your groups will all look pretty good (they already do)!! Focus on ES, variance in velocity between groups and POI on the targets. Hope that helps and good luck! Haha, that is exactly what I was trying to replicate was the FGMM clones! Looking at my results for 42.0, they have to tightest velocities but the most vertical dispersion, just like you said. Strange! I will be revisiting the 41.5-42.5 range to find that sweet spot, only this time I'll be checking CBTO seating measurements instead of COAL! That's good to know about noting large velocity variations indicating scatter nodes or approaching max pressure, I'll keep an eye on that! Thank you, Kandoc! Quoted:
The testing you ran is fine, but it isn't an OCW or Ladder. By now you have seen the articles on Ladder and OCW. You probably don't need to run one unless you plan on going out to distances that use most of the sonic distance. Your testing is showing promise at the distances you are using, so maybe you should try and optimize as is. Unless you are really trying to get out past 400 yards on a regular basis? I'm stuck with 100 yards for the next two weeks but I will very rarely, if ever shoot more than the local 500 yard range. I assume it is unnecessary, I could probably hit most targets with one of these loads at 500 yards, I'm just enjoying learning the process! Thank you, I'll find my lower "41.7ish" node and then experiment with seating depth! I'll be loading this weekend, upgrading my scope, and once this rain goes, testing out to 500 yards. I'll post my results! Thanks for the help, I've learned a lot. 
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Quoted:. . . Haha, that is exactly what I was trying to replicate was the FGMM clones!. . . Don't know the difference in case volume between Hornady and Federal brass, but your 41.8gr load shot pretty well on its own :) I've shot 168gr FGMM as bechmark loads in my 308 and re-barreled 30-06. As usual, they shot very well but a different load shot better. So keep looking !?! |