This is a discussion on Reducing SD and ES within the Reloading forums, part of the Sniping Related category; Back to the issue I just loaded forty rounds, with four different types of primers. They're going to get shot through the chrono tomorrow Then ...
Back to the issue
I just loaded forty rounds, with four different types of primers.
They're going to get shot through the chrono tomorrow
Then I simply select the best primer with the lowest ES/SD, correct? as I've already determined the best combination of powder/brass/bullet and seating depth
Or will all this be thrown off?
How much will the primer affect my other results?
99% of the Lawyers make the rest look bad.
Who would be Free; Themselves must strike the blow.
Back to the question of how to lower ES/SD, among the anal retentive crowd known as Benchrest Shooters, the holy grail of consistent ammo is Case Preparation.
They spend more time on case prep than any other aspect of their "sport".
Matching case capacities in batches by using water fill or actual case weights, Annealing, neck turning not only to fit their custom chambers but also to achieve consistency that factories won't produce in neck wall thickness. Couple all that with the proper amount of neck tension by selecting the right bushing for neck sizing or having the die maker hone one to their specs.
Neck tension is so important to consistency they often use none at all. Some shooters, that aren't under a time constraint in their competition, will merely "stuff" a bullet into the lands using a separate tool that inserts the bullet into the lands with micrometer accuracy. They then use a case that's been primed, charged, and capped with some green florist's foam--just something to hold the powder in place.
For those that have a time constraint and can't breech load their bullets as described, will use only enough neck tension to keep the bullet from sliding all the way into the case on it's own. The final seating is done when the bolt is closed on this "minimal neck tension" cartridge.
For my case prep I merely clean in SS Pins, Anneal, Neck size with a bushing and then in a final step make sure all neck ID's are the same by using a mandrel type expander. The cases, when new, were fired once, F/L sized, then the necks were "skim cut" to just true them people used to do with tires. Not necessarily cut all the way around the circumference but enough to insure that at least 3/4 of the way around the neck is uniform in thickness.
This gives me cartridges that I don't have to be ultra careful when handling and can load from a magazine if I so choose.
As for the Chrono Readings? When I see groups that are measuring sub .250 MOA on a regular basis, the only reading I care about from the chrono is the average speed. I use that to fill one of the "boxes" in my Ballistic's program for use in multiple distance calculations. Unless your chronograph uses the old "shoot through" contact sheets (one use per) the sensors can be triggered by different parts of the bullet as it passes "through". The most accurate method if you can afford it is Ulta High Speed Video with a distance measuring background like used on Mythbusters and in a lot of labs. Unfortunately those cameras can run easily from the low 5 figures up into the low 6 figures. Everything else is "value engineered" for the intended user.
Orkan, no worries. She actually gets mad at me when I assume she knows what I'm saying when I start talking to her about this stuff. But some of the guys she works with are jokes, and these are the ones that are actual "gun experts."
As I'm sure you know, theres a huge gap between practical knowledge and book knowledge when it comes to this stuff.
Regarding my ES/SD issue
I actually ran the math on the values I got from the too close chrono tests and at 500 yards theres only a 5-1/2 inch drop between the fastest and the slowest value. Using the average value thats still close enough to kill ground squirrels at that range.
However theres good news. Mrs. Ragnarnar was kind enough to re-chrono the rounds I loaded last night. This time at an appropriate range of 8-1/2 feet.
A few of the values didn't get recorded, but I got what I needed.
Again the load is 25.4gr BL-C(2), 70gr Berger VLD Target, in Lapua brass.
CCI BR-4: Mean 2925 SD 11.56
CCI No.41 (for 5.56) Mean 2931 SD 12.6
CCI No. 450 (SRMP) Mean 2923 SD 9.1
CCI No. 400 (SRP) Mean 2892 SD 28.6
(I wasn't able to find any 7-1/2's)
Obviously I'm going with the magnum primers, a SD of 9 fps is better than I could have hoped for this early on.....
I'm really interested to see what happens if/when I get around to annealing, neck turning and anything else I do.
Thanks for the help with this one folks, I don't know why it didn't occur to me to me that muzzle blast would affect the chrono readings
edit: just found this
take a look at the primers part.
Last edited by Ragnarnar; 01-29-2016 at 09:42 PM.
They had a booth a SHOT. They had a few units sitting there, but I was unimpressed with their literature and display
I'm fortunate that I have a chrono at my disposal that I didn't have to pay for....
Um.... something about me hoping that they'll change their marketing and start shipping them out.... I swear I had something for this
Last edited by Ragnarnar; 01-29-2016 at 09:31 PM.
You have no idea how refreshing it is for me to see someone doing testing themselves, getting advice here, and then going to do real world testing of their own and working through these issues. Someone ACTUALLY shooting, rather than just talking about it. More amazing still is the fact that you are remaining objective and data-oriented in your approach. You have absolutely no idea how refreshing it is to have an opportunity to help someone such as yourself. Bravo sir, and I look forward to seeing more of your work.
BTW, when gathering chrono data, I prefer to run long strings. Minimum of 20 and sometimes up to 50 (just shoot over the chrono during a regular range session). Larger sample sizes give truer numbers. In a string of 5 or so, it only takes ONE round to blow the ES number out of the ballpark. In a larger sample size it stands out as an anomaly.
Last edited by deadshot2; 01-30-2016 at 07:06 AM.