Which group to test further?

[cstrah6]

My 6.5 Creedmoor did not seem to like 140 ELDM H4350 combo. Could not get below 1.5 MOA for 15 shot group no matter powder charge.

Went out this morning and tested 140ELDM with Staball 6.5 with 5 shot groups at 42 gr and 43 gr. No signs of pressure at 42 gr but do have some ejector marks at 43 gr.

Pictures show the two groups. My question is which group would you pick to load a 15 shot group with.

No chrono only working at group size.

Group on the left measured .68
Group on the right measured .77 with the 5 round being low.

 

[Marbles]

The one without pressure signs.

If you truly think the powder charge will make a difference, then both.

 

[Andouille]

If 42 and 43 shoot these statistically indistinguishable groups and you have pressure signs at 43, and you want to maximize velocity (and don't subscribe to "node theory"), then just shoot 42.5. Its my experience that 1/2 grain makes little to no difference on accuracy with 6.5CM with H4350, SB 6.5, H4831sc, VV560, V555, and combinations of 140 eldm, 147 eldx, 147 eldm which are generally very accurate at 0.050" +/- jump.

 

[cstrah6]

I was not supper concerned about the ejector mark on the 43 gr load because I have seen this on factory ammo as well in this rifle. I was more concerned about the bolt lift being heavy. I’m new to reloading and not super confident in pressure signs to be honest.

Here is the ejector mark on 43 gr load.

 

[cstrah6]

If 42 and 43 shoot these statistically indistinguishable groups and you have pressure signs at 43, and you want to maximize velocity (and don't subscribe to "node theory"), then just shoot 42.5. Its my experience that 1/2 grain makes little to no difference on accuracy with 6.5CM with H4350, SB 6.5, H4831sc, VV560, V555, and combinations of 140 eldm, 147 eldx, 147 eldm which are generally very accurate at 0.050" +/- jump.

I am trying to maximize velocity. I cut the barrel down to 18 inches in this rifle shooting suppressed. I will try 42.5 and see how it shoots

 

[Caseknife]

If you are new to reloading and trying to maximize velocity and not shooting with a chrono, maybe get a chrono?

 

[Andouille]

I was not supper concerned about the ejector mark on the 43 gr load because I have seen this on factory ammo as well in this rifle. I was more concerned about the bolt lift being heavy. I’m new to reloading and not super confident in pressure signs to be honest.

Here is the ejector mark on 43 gr load.

It appears that you also have some primer catering (raised lip on firing pin indent) and a moderately flattened primer so dropping the load would be prudent. Bolt lift occurs when youre already substantially over pressure, so it's important to pay attention to the precursor signs to guide your safe load.

Hornady brass is on the softer side and won't handle pressure as well as does premium brass, but were talking maybe 20-30fps gain before you see the same pressure signs. I use Lapua (best) and Starline (better) for 6.5 CM.

Lastly, seating the bullet farther out in the case than SAAMI COAL may gain you a fee FPS due to increased powder capacity and case volume. This assumes adequate magazine length and a jump of 0.030-0.050" to the lands. This jump is in the sweet spot ELDM and ELDX in 6.5CM.

Are you shooting a tikka?

 

[cstrah6]

If you are new to reloading and trying to maximize velocity and not shooting with a chrono,

It appears that you also have some primer catering (raised lip on firing pin indent) and a moderately flattened primer so dropping the load would be prudent. Bolt lift occurs when youre already substantially over pressure, so it's prudent to pay attention to the precursor signs to guide your safe load.

Thanks for the info! I will stay at 42 gr!

 

[cstrah6]

It appears that you also have some primer catering (raised lip on firing pin indent) and a moderately flattened primer so dropping the load would be prudent. Bolt lift occurs when youre already substantially over pressure, so it's important to pay attention to the precursor signs to guide your safe load.

Hornady brass is on the softer side and won't handle pressure as well as does premium brass, but were talking maybe 20-30fps gain before you see the same pressure signs. I use Lapua (best) and Starline (better) for 6.5 CM.

Lastly, seating the bullet farther out in the case than SAAMI COAL may gain you a fee FPS due to increased powder capacity and case volume. This assumes adequate magazine length and a jump of 0.030-0.050" to the lands. This jump is in the sweet spot ELDM and ELDX in 6.5CM.

Are you shooting a tikka?

No shooting a tika. This is a cheap Thompson center compass I have had for a few years. Rifle shoots extremly well for the price. I paid $200 bucks at academy for this about 8 years ago.

I followed Forms seating depth rules and seated the bullet with the base close to the neck shoulder junction which put me at 2.817 COL length. Sharpied the bullet and was not touching the lands. Not sure what I am off the lands.

I have some Starline brass coming in so I will see how it does at 42-43 grains.

 

[N2TRKYS]

I always want the fastest load. So, whichever is the fastest.

 

[Tanner]

Left group is round and that’s important to me. If that’s a 42gr load I’d simply load a pile of that and start gathering dope to however far you plan to shoot.

 

[cstrah6]

Left group is round and that’s important to me. If that’s a 42gr load I’d simply load a pile of that and start gathering dope to however far you plan to shoot.

Sorry to ask if it’s common knowledge but what is the importance of the group being round?

 

[Tanner]

Sorry to ask if it’s common knowledge but what is the importance of the group being round?

Shows me that things are jiving and you’re not dealing with vertical or horizontal stringing.

 

[RME]

Keep shooting and you'll see every 3 shot group shape imaginable....from the same load

 

[mtnbound]

My 6.5 Creedmoor did not seem to like 140 ELDM H4350 combo. Could not get below 1.5 MOA for 15 shot group no matter powder charge.

Went out this morning and tested 140ELDM with Staball 6.5 with 5 shot groups at 42 gr and 43 gr. No signs of pressure at 42 gr but do have some ejector marks at 43 gr.

Pictures show the two groups. My question is which group would you pick to load a 15 shot group with.

No chrono only working at group size.

Group on the left measured .68
Group on the right measured .77 with the 5 round being low.

Both are fine as far as size.

I don’t worry about some PSI stuff, I am looking for consistent signs in my LD test groups. If all of the 43gr group shows signs then drop to 42 or 42.5. If there isn’t consistent psi sign then run it.

I would likely load 20 of each and shoot 15 for group size and save 5 for longer range validation. Let the winner of the 15rd group be the one you go with.

 

[pbroski]

You already have the group size data staring you right in the face. Overlay those two 5-shot groups, and that's the size a 10 round group will be for either 42 or 43 grains. A difference of only 1 grain just doesn't have any real effect on either precision or POI at 100 yards. The POI difference you see on your target is due to random distribution with small sample size.

 

[cstrah6]

You already have the group size data staring you right in the face. Overlay those two 5-shot groups, and that's the size a 10 round group will be for either 42 or 43 grains. A difference of only 1 grain just doesn't have any real effect on either precision or POI at 100 yards. The POI difference you see on your target is due to random distribution with small sample size.

Good to know! I’ll stay at 42 gr and load a bunch and shoot

 

[Andouille]

Sorry to ask if it’s common knowledge but what is the importance of the group being round?

absolutely nothing, both of your groups are statistically indistinguishable due to the low shot count. @pbroski is spot on that you can overlay the groups and that's likely representative of a group from eithe 42 or 43 grains. Take a read here: https://rokslide.com/forums/threads/your-groups-are-too-small.290821/

The only definitive determination that can be made from a small sample size group (<20 rounds) is if a group is "definitively over a set group size goal." A small group with a small round count can only suggest that you have a good load, but you need to shoot preferably >20 (some would say >30) shots to get an idea of the cone of fire that results from dispersion, and the cone of fire will be ROUND as an average, assuming there's nothing wrong with your gun (loose action, bad barrel, etc.) or your shooting technique (bad trigger pull, not lined up behind gun, flinch, etc).

Most practical way to evaluate groups against each other is to shoot at least 10 rounds and measure mean radius, which accounts for the position of each shot relative to the averaged center of the group. This measure gives you a better, quantitative measure of the dispersion for a given load, and is useful for determining your averaged point of aim. https://www.outdoorlife.com/guns/what-is-mean-radius/

6.5CM Starline brass has about 1 grain less capacity than Hornady brass, so you'll want to back off about 1.5 grains, and work back up to pressure signs, then load about 0.5 grains below pressure signs.

I'm guessing that your COAL is short for a TC rifle, as they are known to have long throats (farther distance to the lands). I would load at SAAMI COAL which is 2.825" if you don't want to mess with finding the distance to your lands. There's no reason I can think of to load any rifle shorter than SAAMI COAL because all rifles will safely chamber to that standard. That will lengthen your bullet by 0.008" which will drop pressure a probably imperceptibly small amount.

If you really want to maximize speed, then consider measuring the distance to your lands and loading to 0.030-0.050" jump, which will increase powder capacity. The caveat is that you'll have to test a small ladder (e.g., 43, 43.5. 44gr) to find pressure. For example my Tikka loads to 2.886 with 140 ELDM and I was able to add about 1 grain more powder without hitting pressure. There are several techniques to "find the lands:"

 

[cstrah6]

absolutely nothing, both of your groups are statistically indistinguishable due to the low shot count. @pbroski is spot on that you can overlay the groups and that's likely representative of a group from eithe 42 or 43 grains. Take a read here: https://rokslide.com/forums/threads/your-groups-are-too-small.290821/

The only definitive determination that can be made from a small sample size group (<20 rounds) is if a group is "definitively over a set group size goal." A small group with a small round count can only suggest that you have a good load, but you need to shoot preferably >20 (some would say >30) shots to get an idea of the cone of fire that results from dispersion, and the cone of fire will be ROUND as an average, assuming there's nothing wrong with your gun (loose action, bad barrel, etc.) or your shooting technique (bad trigger pull, not lined up behind gun, flinch, etc).

Most practical way to evaluate groups against each other is to shoot at least 10 rounds and measure mean radius, which accounts for the position of each shot relative to the averaged center of the group. This measure gives you a better, quantitative measure of the dispersion for a given load, and is useful for determining your averaged point of aim. https://www.outdoorlife.com/guns/what-is-mean-radius/

6.5CM Starline brass has about 1 grain less capacity than Hornady brass, so you'll want to back off about 1.5 grains, and work back up to pressure signs, then load about 0.5 grains below pressure signs.

I'm guessing that your COAL is short for a TC rifle, as they are known to have long throats (farther distance to the lands). I would load at SAAMI COAL which is 2.825" if you don't want to mess with finding the distance to your lands. There's no reason I can think of to load any rifle shorter than SAAMI COAL because all rifles will safely chamber to that standard. That will lengthen your bullet by 0.008" which will drop pressure a probably imperceptibly small amount.

If you really want to maximize speed, then consider measuring the distance to your lands and loading to 0.030-0.050" jump, which will increase powder capacity. The caveat is that you'll have to test a small ladder (e.g., 43, 43.5. 44gr) to find pressure. For example my Tikka loads to 2.886 with 140 ELDM and I was able to add about 1 grain more powder without hitting pressure. There are several techniques to "find the lands:"

I am familiar with your groups are to small. I still have a hard time wrapping my head around some items though.

For instance on the same target posted above, I have another load at 43.7 gr (Hornady book max) that measures 1.5 Moa for 5 shots. Felt solid on all groups that day so I don’t believe shooter problems accounted for the increase in group size.

So just because it’s a 5 shot group it’s not valid that 42 Gr (.68 Moa) is a better load for this rifle compared to the 43.7 (1.47 Moa)?

 

[cstrah6]

I know that for a 15 shot group the .68 inch group will get larger most likely. But wouldn’t the 1.47 inch group as well?