Scale, powder, chrono, or me?

[snbyiggidy1]

I have been working on some precision loads for my two precision rifles. One is a 6.5 Creedmoor the other 224 Valkyrie both bolt action. I am issuing a Dillon beam scale and IMR 4350 for the Creedmoor and CFE223 for the Valkyrie. I have been working velocity node testing hoping to find a powder load that gives me single digit standard deviations. This has been less than successful. The best SD I have seen so far has been 14.7 and that was not repeatable. My velocities are all over the place. I get a couple rounds close then rounds that are several hundred fps different resulting in SD’s of 200 fps +\-. I don’t think this is my load weights as variations that large in fps would require over a grain difference in powder charges which is not happening. So that leads me to wonder if it is the powders or is my magnetospeed giving me bad numbers? I have had several times in the past when doing incrementally larger charges in sequence where the magnetospeed would give me a slower round in the middle of a string when it should have gone up in velocity. This has happened several times. I am just wondering if maybe I need to invest in a better scale, or chrono? Or maybe give a different powder a go when it becomes available again. Any thoughts?

 

[Islander]

How new are your rifles? Sometimes barrels need some rounds through. A lot depends on the quality of the barrel also.

 

[snbyiggidy1]

The 6.5 is a factory tikka CTR barrel and the other is a Preferred Barrel Blank barrel. Both have a little over 100 rounds. Still fairly new but not brand new.

 

[MCHOG]

IF it's between your Magnetospeed and your scale, I would bet it's the scale. Having said that, I'll add that: (a) a goal of single-digit SDs is a waste of time for 95% of folks; (b) you will never get there with that scale; and (c) a lot of other things can affect your SD. There are plenty of good scales that are less than $200. I'd start there. Or just get an A&D FX120.

 

[TheOfficeT-Rex]

How's the battery in your magnetospeed? Sometimes I'd get wonky readings when it got low.

There are several things it could be - ie. How are you setting neck tension? Also, if you are doing velocity ladders with a single round at each charge weight it is quite possible to get a few data points below the trendline.

 

[snbyiggidy1]

IF it's between your Magnetospeed and your scale, I would bet it's the scale. Having said that, I'll add that: (a) a goal of single-digit SDs is a waste of time for 95% of folks; (b) you will never get there with that scale; and (c) a lot of other things can affect your SD. There are plenty of good scales that are less than $200. I'd start there. Or just get an A&D FX120.

Totally agree that it is a waste for the most part. I would be happy with SD’s above that but I have not been able to get even close. Here is the results of one of six tests done today.

How's the battery in your magnetospeed? Sometimes I'd get wonky readings when it got low.

There are several things it could be - ie. How are you setting neck tension? Also, if you are doing velocity ladders with a single round at each charge weight it is quite possible to get a few data points below the trendline.

I will get a new battery for the next range trip and see it that helps. It was a new battery when I had issues before but hey it is worth a try so will do that.

Agree with MCHOG. Probably something you are doing with the charge weights...inadvertently. But, is it new or fireformed brass? Which primers? How are you sizing (neck tension, specifically)? How is your seating depth consistency? Are you letting a round sit in a hot chamber before firing...specifically on one that goes unusually fast? I would start by weighing out some charges that don’t go into the case...just weigh one out and set it aside. Check that the scale goes back to zero and then weigh out another....check zero and then re-weigh the first charge....does it still weigh the same thing? Do this enough to be absolutely convinced that each charge that goes into a case weighs what you think it does.

Batteries in the magneetospeed?

Just some ideas.

I use a Sinclair mandrel for sizing neck tension and use a Redding completions micrometer seater with very consistent seating depth results. With form fired brass. I will do the measuring like you suggested and see what happens. I have no issue buying a new scale. Will start looking in that direction.

 

[snbyiggidy1]

Hmmm...that’s a huge variation. Have you tried the magnetospeed with a different rifle/cartridge...some kind of “known”?

Agreed. It is a huge spread and bigger than a small variation of powder charges. However don’t disagree that testing my measuring system would be a good place to start. I forgot to say I am using cci bench rest small rifle primers all of the same lot. As for testing with a known cartridge. No I have not. I will have to see if anyone I know has a known load they could shoot with my magnetospeed. I do t personally have a known load. Load development is new to me.

 

[snbyiggidy1]

All the questions were in part to rule out any big problem in your process. It sounds reasonable. How are your trim lengths? You don’t have some brass pieces that are over length, do you? I’m not sure that would do what your seeing...speed changes...but it’s worth checking. I don’t know shit about .224V but I’ve loaded a lot of 6.5CM. What are your numbers for those? Low SDs aren’t necessarily a result of perfect load weights...all the other stuff matters too. Finally, how organized are you? Is there a chance you are mixing up loaded cases and getting out of sequence?

My trim lengths are very good. Very consistent using a Giraud trimmer and checked following trimming to make sure they are consistent which they are. I am very particular when I load and use a system that keeps me in order. I thought the first time I saw an odd speed that I had maybe switched a round or got the measurement wrong. But after seeing similar results again and again being even more diligent I have decided it has to be something else. Here is one of my 6.5 tests.

 

[Islander]

That is a pretty significant spread. I’d check the magnetospeed with some known velocity ammo. Even buy some factory rounds and run them through, they should be a lot more consistent than what you’re getting.

 

[ditter]

Think about if you wanted to get a spread like that on purpose. You'd have to have such big variance on charge weights and that would be difficult on a beam scale. Id say its the chrono. Shoot some good factory ammo over the chrono and see if it gives the same results.

 

[snbyiggidy1]

That is a pretty significant spread. I’d check the magnetospeed with some known velocity ammo. Even buy some factory rounds and run them through, they should be a lot more consistent than what you’re getting.

Yeah...I’m starting to think maybe it’s a chrono issue...that spread look really reasonable except for shot 4. And that seems too much to be attributable to anything other than some kind of gross loading error. You could try shooting a string at...300 yards or more. If there’s really a velocity difference of several hundred FPS, it will hit low. Of course this depends on you being a good enough shooter to see the difference as a low shot not a poorly executed shot. Or, shoot some factory ammo and see what’s up. Or, put the chrono away and just short for OCW as it prints, without regard to the speed. Keep us posted.

Looking back at some of my 6.5 data
I tried some factory Hornady 140 g ELDM back at the beginning of using the magnetospeed. Shot nine rounds which one round did not register any data. That produced an extreme spread of 78fps and an SD of 23.9. So better that the recent data. I also was able to get the SD of my reloads using IMR 4350 down to 21.3 and 22.6 for two different tests. I kept that as my charge weight and started seating depth adjustments. Half MOA at 100 was best group so far with that so very happy. Then got distracted with new 224 build and testing which has brought on the real issues. I think I will try a new battery I am thinking that might be an issue given early on data vs today’s. Also I am confident in my ability to shoot well enough to see the difference at distance. Think I will try that if a new battery does not produce better results.

 

[TheOfficeT-Rex]

While you're swapping the battery, double check your alignment ( I used a 14" piece of 1/4" wood dowel slipped into the bore) and your sensitivity setting.

 

[Slab74]

I have found that I need to check the tension on the strap every few round, while using that chronograph. With some barrel profiles, it moves a lot. I was getting weird numbers that were not showing up on target before I checked it between rounds. That is why a labradar is on my list. I know that they are not perfect but what is?

 

[snbyiggidy1]

While you're swapping the battery, double check your alignment ( I used a 14" piece of 1/4" wood dowel slipped into the bore) and your sensitivity setting.

Good ideas. I have checked alignment in the past with a rod but being honest have not every time I put it on.

I have found that I need to check the tension on the strap every few round, while using that chronograph. With some barrel profiles, it moves a lot. I was getting weird numbers that were not showing up on target before I checked it between rounds. That is why a labradar is on my list. I know that they are not perfect but what is?

I have been considering changing out to a labradar. Almost went with that initially but...Nothing is perfect for sure but a Labrador seems like it might fit the bill a little better. Plus would work with all my guns so I could check velocities on my subsonic pistol reloads too.
lol

This thread reminds me why I HATE chronographs. You fiddle around more than you shoot, theres a fifty/fifty chance you shoot a piece of equipment, you finally get it adjusted, aligned, tuned and ready and then half your data string gets corrupted, you catch a neighbors shot instead of yours, it starts raining, etc. what a pain in the ass. When I was shooting for groups at a fixed distance, I NEVER ran a chrony. The holes in the paper were all I needed. Now, once Im happy with groups at 100 and 300, I’ll take the chrony to the range one time, get an average speed over some shots (I say some because if you set out to collect data on 5, 3 will invariably fail to accurately record) and call it good. Eff it. I’d rather miss than spend time collecting chrony data.

Right there with you. I went down the chronograph hole for sure. I like the idea of shooting for groups then distance. Even with the velocity reading issues the rifle has been grouping great. Might try my current load out to 300 and see what happens.

 

[snbyiggidy1]

Did some testing today. New battery in the chrono seemed to help some but did not solve all the inconsistencies. Retested the last set of loads which did produce better results but still have random strange numbers that don’t make sense. Was very careful as always to get my loads as correct and consistent as possible. Think the next step is to work through a OCW loading and shoot out to distance and see how things go. Or maybe if I can find someone with a labradar to try. Or run my magnetospeed on their known loads to see if it reads consistent with their known loads.

 

[snbyiggidy1]

Ok guess I should have actually done the math before I spoke. I actually did find some good data today with the new battery installed. Yes there was a couple odd numbers with some new powders and loads but I retested some loads I was pretty sure would be good and they are. Here are the results. Sorry for the hand written results that are a little harder to read. Forgot my iPhone to magnetospeed speed dongle at home so had to just do all my testing which was more rounds than these then pull the data for these sets out. Bottom line it looks like the new scale and new battery made a huge difference. Think it will be hard to get better than a SD of 7.61. Thanks for all the advice.