.223 es/sd

[SGK]

Question: does this velocity SD 'finickiness' characteristic of the 223 relate also to lighter bullets? I'm trying to find a load for my 1:10 223 Rem with 52 gr Hornady ELD-M bullets. I probably should be using Sierra TMK in 60 or 69 gr but I purchased a big bunch of the 52 gr ELD-M. I'm still hoping to get single digit SD from 5 shot strings. Best so far is an SD of 9.8fps.

(I'm using Varget.)

 

[CharlieNC]

Hello. What kind of Brass are you using? Besides using quality brass that all weighs within .1 grain and is the same internal capacity, you should use try Benchrest primers such as Remmington 7 1/2.

Using a stick powder, Lapua brass with within .1 grain internal case capacity, and quality primer, the lowest SD I seen you can get consistently is about ~4-6 SD, with some batches of 5 shot groups in the ~2-3 SD range with 5.56. XBR8208, Norma 203B, RE15, Varget, can do sub 10 SD consistently with consistent components. Your question will be answered directly on this website soon I think. I know they are working on 5.56 this summer.
http://www.natoreloading.com/

Shooting Ftr, I don't know how I would reasonably get enough brass within .1gr to even shoot one 20 shot match. Within .5gr is feasible given > 1.5gr for the population. Whats your secret?

 

[XTR]

Shooting Ftr, I don't know how I would reasonably get enough brass within .1gr to even shoot one 20 shot match. Within .5gr is feasible given > 1.5gr for the population. Whats your secret?

Keep in mind in replying to this post a typical F class match weekend starts with 150 or so loaded rounds.

 

[CharlieNC]

Keep in mind in replying to this post a typical F class match weekend starts with 150 or so loaded rounds.

Of course. I don't have a problem segregating different weights into different 20 round matches plus sighters. A minor resulting elevation adjustment between matches is not an issue to achieve improved consistency within a match. I could accommodate .3gr segs in this manner, but not .1gr.

 

[clowdis]

Of course. I don't have a problem segregating different weights into different 20 round matches plus sighters. A minor resulting elevation adjustment between matches is not an issue to achieve improved consistency within a match. I could accommodate .3gr segs in this manner, but not .1gr.

Yep, I'm likely to carry 250 rounds o more to shoot a National, even more if I shoot mid range and long range, so sorting to .1 internal case capacity is a definite nope!

 

[Ned Ludd]

Of course. I don't have a problem segregating different weights into different 20 round matches plus sighters. A minor resulting elevation adjustment between matches is not an issue to achieve improved consistency within a match. I could accommodate .3gr segs in this manner, but not .1gr.

The real key is to carry out some velocity testing with relatively small number of cases to determine exactly how much internal volume variance you can get away with before the velocity change becomes significant. The easiest way to do this is to select 5 cases (each) with the highest and lowest volumes you can from a given brass prep, load them up identically, then determine velocity. For this experiment, it's better to use actual case volume, but I would also weigh the cases prior to loading. As the total number of cases required is small, it shouldn't be too painful. Once you have determined velocities, you can decide for yourself how much internal volume variance you can really stand, and how to achieve that level of volume variance. IMO - chances are pretty good you can come very close to doing it simply by weight-sorting the cases into 3 to 5 distinct groups.

The data in the graph below is derived the exact same brass prep for which I showed the effect of case weight on velocity earlier in this thread. Notice the two cases of weight greater than 6.30g at the upper left. Those are from the same "heavy" subgroup that represents about one in 4 cases within this Lot of brass and gave me almost 30 fps greater velocity than the three cases in the 6.17 to 6.22 gr weight range. Sorting 150 cases (or more) by weight can easily be done in less than an hour using an analytical balance, which many also use to weigh powder.

 

[SGK]

Interesting that you get such a range. I just weighed thirty five 2xF 223 Rem cases (Lapua), sized, trimmed to length, chamfered and deburred. I had previously turned the high side of the necks down to approx 0.013", leaving a reasonable amount of uncut 'low side'. Here are the results in grammes.

35 Count
6.149 Average
0.021 STDevA
6.110 Min
6.209 Max

 

[CharlieNC]

The real key is to carry out some velocity testing with relatively small number of cases to determine exactly how much internal volume variance you can get away with before the velocity change becomes significant. The easiest way to do this is to select 5 cases (each) with the highest and lowest volumes you can from a given brass prep, load them up identically, then determine velocity. For this experiment, it's better to use actual case volume, but I would also weigh the cases prior to loading. As the total number of cases required is small, it shouldn't be too painful. Once you have determined velocities, you can decide for yourself how much internal volume variance you can really stand, and how to achieve that level of volume variance. IMO - chances are pretty good you can come very close to doing it simply by weight-sorting the cases into 3 to 5 distinct groups.

The data in the graph below is derived the exact same brass prep for which I showed the effect of case weight on velocity earlier in this thread. Notice the two cases of weight greater than 6.30g at the upper left. Those are from the same "heavy" subgroup that represents about one in 4 cases within this Lot of brass and gave me almost 30 fps greater velocity than the three cases in the 6.17 to 6.22 gr weight range. Sorting 150 cases (or more) by weight can easily be done in less than an hour using an analytical balance, which many also use to weigh powder.

View attachment 1098249

I did this, so far only evaluating the volume effect on velocity via Quick Load. As I recall it was 16fps. Eventually I will get around to loading them and shooting over the chrono. But the results such as you have made it clear that weigh sorting is a low investment benefit. Interestingly I weighed 1000 new LC brass and it had less variability than my 200 Lapua. I like the higher capacity of the LC as I can get the same velocity at lower pressure according to QL, and it has shot just as well over several years.

 

[Ned Ludd]

Interesting that you get such a range. I just weighed thirty five 2xF 223 Rem cases (Lapua), sized, trimmed to length, chamfered and deburred. I had previously turned the high side of the necks down to approx 0.013", leaving a reasonable amount of uncut 'low side'. Here are the results in grammes.

35 Count
6.149 Average
0.021 STDevA
6.110 Min
6.209 Max

This is the first Lot of Lapua .223 Rem cases that I've ever had that had such a significant number of cases in that high weight range. In numerous previous Lots, you might find a case that heavy once in a while, but not 25% of the total. It's problematic because of the ~30 fps increase in velocity. Even if I sort all those heavier cases into a separate weight group, I'm going to have to drop the charge weight by 0.2 to 0.3 gr to keep the velocity (and the load) the same as with the lighter cases.