1/10th of a grain = how many fps?

Screwtop.243 · Mar 22, 2018

So, I finally made my way into 20th century technology and bought myself an RCBS Chargemaster Lite to weigh out my charges, hoping to retire my old RCBS 505 beam balance scale. When I got the Chargemaster Lite, I put it through it's paces with some Varget and RL-15 to see how accurate it was vs. the 505 beam balance, and was a bit dissapointed to see it's accuracy waiver a bit more than the +/- .1g advertised.

I called RCBS and they had me wipe the thing down with a dryer sheet to remove any static charges that might be coming into play. I guess it helped a little and I may be within that advertised +/- .1g accuracy now, but it got me to thinking, how much difference does .1g make? For instance, with my .25-06 varmint load (a 90 grain blitzking over 54 grains of IMR 4831 w/avg. velocity of 3,320 fps) how much of difference is +/- .1g really gonna make? I'm thinking/hoping it's in the single digits, and in the grand scheme of things negligable compared to the 60-80 fps ES's that I'm trying to address by other means. Thoughts?

Squaregrouper · Mar 22, 2018

I'm by no means an advanced reloader. That being said, I get my Lee beam scale to a precision of one "stick pellet" of powder using RL16. At charge weights A, B and C, I will have an extreme spread of 20-25fps with charges more precise than 1/10gr. However, at charge weight D, my velocities were nearly identical. Brass, primer, projectile and seating depth were all damn close to identical for all loads as well.
I don't know if this helps to answer anything.

Major03 · Mar 22, 2018

Hmmm, interesting question. My guess is variations in brass internal volume and bullet weight would matter more than +\- .1 gr.

Probably would matter what caliber too. .1 gr of 30’06 would be a lower % of overall powder than .1 gr of .223 I would think.

Sort some cases and bullets, trickle up some charges and run an experiment with a Chrony. Worse case scenario you do some shooting

PowPow · Mar 22, 2018

I bet temperature & powder sensitivity to temperature will have more of an impact on your FPS than +/- 0.1gr.

deerassassin22 · Mar 22, 2018

This is a good read

https://www.autotrickler.com/accuracy.html

Screwtop.243 · Mar 22, 2018

deerassassin22 said:
This is a good read

https://www.autotrickler.com/accuracy.html

That was interesting, thanks. Based on his .308 example (50 fps/grain) +/- .1g would mean 5 fps, which seems reasonable but as others have said, many more factors are at play.

In the 25-06 example I gave, I had ES of about 80 fps with my Magnetospeed Sporter (Horrors!). So if the .308 example from the article is any indication, and my goal is to reduce ES under 20 fps, should I just not worry about the Chargemaster's +/- .1g variation and continue using it? I'm thinking I'll get more bang for my buck reducing ES by focusing on primer pocket/flash hole uniforming and neck tension, etc.?

John from MD · Mar 22, 2018

In the powder range you are using, unless you are shooting at 1000 yards, you won't notice a couple of grain difference. Use the time to segregate your brass and standardize your neck thickness. These two actions will give you more of a return than worrying about a couple of tenths of a grain of powder.

K-43 · Mar 22, 2018

My Lyman likes to throw a tenth low from time time, so when it throws low I trickle in a few kernels to bring it up. It's still faster than a regular measure, beam scale, and trickler.
Also, I had problems under fluorescent lights. I changed to LED overhead and desk lamp bulbs and it settled down a bit.

paxfish · Mar 23, 2018

I agree that bullet variation is likely even more important, and so I weigh them into lots.

I still use a beam balance and trickle every rifle charge.

BTW - Love those Blitzkings in my AR in 55gr. Tiny groups!

Screwtop.243 · Mar 23, 2018

John from MD said:
In the powder range you are using, unless you are shooting at 1000 yards, you won't notice a couple of grain difference. Use the time to segregate your brass and standardize your neck thickness. These two actions will give you more of a return than worrying about a couple of tenths of a grain of powder.

Thank you John and all. This is useful information. I will focus efforts accordingly.

PowPow · Mar 23, 2018

This thread still led the perfectionist in me to covet the A&D FX-120i scale.

Jerry M · Mar 23, 2018

Too many variations in case capacity, neck thickness, bullet length & weigh to matter about 1/10 of a grain.

Good luck

Jerry

Blacksmith101 · Mar 24, 2018

If you are banging steel gongs it doesn't matter much. If you want to send them all through the same hole in the target then pay attention to what the bench rest shooters do; to the extent of weighing everything, using the same case for each shot and orienting the case the same way. Find your happy medium for what shooting you are doing. You have crossed the first hurdle in realizing every thing is a variable that has some effect, Eley identified nearly 1,000 variables that effect a .22 rim fire.

http://www.shootingtimes.com/ammo/ammunition_eley_101405/

Eley engineers identified 50 primary variables–basics like bullet mass, case internal volume, and propellant charge mass.

Then they determined 200 secondary variables–things like the ambient humidity in the assembly facility, the metallurgy of the cases, human competence. Finally, they identified 700 tertiary variables–subtle things the TenEx project manager told me turned out to be the ultimate keys to getting things really up to “the TenEx level.” For example: weather conditions in the country where the propellant powder is manufactured on the day that particular lot of powder was mixed. (Yes, Eley actually adjusts the TenEx loading profile for each powder lot based on this and other equally subtle considerations. The same is true of the other end of the process; manufacturing “lots” of TenEx consist of one day’s run from a single loading machine because the weather is different each day.)

Klunatic · Mar 24, 2018

Here is pretty interesting article on reloading and "nodes" for a particular rifle. In the article they discuss the node of a barrel and how when you reach the optimal velocity for the barrel that even .4 grains of powder variation will not result in a significant change in velocity. There are also several articles relating to the effects of neck tension, compressed loads. Interesting read.

http://www.65guys.com/10-round-load-development-ladder-test/

MG in MD · Mar 24, 2018

The phrase “all other things being equal” occurs to me. The problem is, you will never get all other things to be equal so I agree with other comments that say that other aspects are more important.

Pinecone · Mar 25, 2018

Of course, it depends on the charge and case. A 0.1 grain difference in a .50 BMG case is not going to make a huge difference. But that same 0.1 grain difference in a .25 ACP is HUGE.

For common rifle rounds, 0.1 is not going to make a huge difference, especially if you use the OCW method of load development. The OCW postulates islands of accuracy, where a couple of tenths +/- do not affect the accuracy.

atblis · Mar 25, 2018

PowPow said:
This thread still led the perfectionist in me to covet the A&D FX-120i scale.

You can scratch that itch for less money. I've got this guy. USB data logging and plenty precise.
http://www.affordablescales.com/adam-equipment/highland/hcb-123.asp#.WreNL3MpA0M

Magnumite · Mar 25, 2018

Doing quick math, 0.1 grain in a 54 grain charge is less than 0.2% variation. The scales tolerance of +/- 0.1 grain is a 0.2 grain range. There is more variation in the scale’s accuracy than in 0.1 grain change in charge weight. Using Pinecone’s observation of OCW (I use a different method but look for stabilty on either side of an optimum charge) a load shouldn't be that effected by the weight of a scale’s variation - at least in that charge weight range. I look for broader charge range stability. I load 223/5.56 with the press’s powder measure and it shoots sub MOA. From my periodic checks using Varget for that load I have observed 0.2 grain variations. I don’t consider loads in the range of 4.0 grains of pistol powder if a +/- 0.1 grain variation shows any statistical variation. If the powder is that sensitive I personally wn’t use it if given other options. Caveat being I haven’t loaded tiny capacity calibers.

deerassassin22 · Mar 25, 2018

atblis said:
You can scratch that itch for less money. I've got this guy. USB data logging and plenty precise.
http://www.affordablescales.com/adam-equipment/highland/hcb-123.asp#.WreNL3MpA0M

NICE!!!

E.Shell · Mar 25, 2018

Simple and direct answer: Unless your 25-06 load's standard deviation is ZERO, you cannot see a tenth or two of variation.

Scale manufacturers and shills would have you believe weighing to 1/100th of a grain or finer will actually matter.

Where velocity deviation actually matters, such as long range precision competitions, most successful match shooters strive for a load that provides stability and consistency specifically so you cannot see it. See "OCW Load Development".

1/10th of a grain = how many fps?

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