Level of precision

[JFrank]

Does level of precision in handloading required to produce single digit SD ammo differs from caliber to caliber?
Let's compare some fundamental criteria:
- powder charge variance
- headspace variance
-CBTO variance

Let's assume we have 0.2 gr variance in powder charge weight, 0.005 headspace variance and 0.005 CBTO variance.
This seems to be trivial conclusion, but shooting 10 shots out of .284 with aforementioned variance should theoretically produce smaller SD than shooting 10 shots out of 6BR with the same variance for the above parameters because (a) 0.2gr powder charge variance constitutes smaller % variance for 50gr charge weight than for a 30gr one (b) the same refers for 0.005 CBTO variance for a 180gr bullet vs 105gr bullet and (c) headspace variance.

If you agree on the above, isn't it fair to say that producing a single digit SD ammo is more difficult in case of smaller calibers?

When I’m searching for improvements in ES/SD department of ( 6 br size cases) , minor headspace variances just doesn’t seem to show on the chronograph nor on the target. A quick way TO improve is case sorting by weight, volume and speed. Additionally’ primer testing, bullet hold testing and of course this is assuming accurate powder charges are being dispensed.

 

[Dgd6mm]

3 weeks ago I watched a man shoot 2 - 5 shot groups at 600 over a Lab Radar.
Both groups were under 1 inch. The bigger was 0.9 something. This was a 6br. I have no idea what his numbers were or are. All I said that whatever he was doing to make it shoot, it was working. So my question is, what do your numbers need to be to make this happen?

 

[dgeesaman]

I don’t think meticulous loading practices alone will cut es under ten.

There are many other factors involved and not all loads will have low es. Searching for a low es load is not the same thing as doing certain things with precision in the bench.

 

[D-4297]

I think it becomes a combination of so many issues , to even include Barrel harmonics . The so-called "tuning fork" effect . Just a few years ago , a very highly rated shooter won a National Championship in F-Class with a SD of nearly 30 , but his loads were also very consistent . I recently had to change powders , and re-develop my load . After doing the Math for a starting point , the result on Target was very promising , with exceptional grouping at 600 , but the "Desired" velocity was slightly lower than I was after . The SD was 7.4 on fifty rounds . Tolerable . I "bumped" the load by two tenths and got to the desired velocity I was seeking , and the SD DROPPED to 6,2 on the next fifty rounds . I shot this load in a Match last week-end , and won the Match by One point , against some very good shooters . All other Brass prep stayed the same as usual . Matching the powder , to the bullet , to the case prep , to the velocity node , to the harmonics to the primer , to the ......on and on . Isn't that why we do this ?

 

[Jeff Porter]

I shot two strings in competition on e-target two weeks ago that showed one ten shot string with SD of 9.6 and a 20 shot string with SD of 9.0 with a .223. My other strings that day were 12-15 SD. All of this at target not muzzle.
This was done with 4x fired brass, processed un bulk by MS processing. Trimmed and chamfered on a Giraud tri-way trimmer. 205mar primers using a RCBS hand primer, H4895 from a Chargemaster and sierra Match king 77 seconds. I did sort the SMK by base to ogive since they were seconds. No real meticulous prep.

 

[Jeff Porter]