Velocity consistency question

[reloader_rob]

Hey guys I have just begun reloading and so far have turned out about 30 rounds of 223 for a Remington model 700. As far as I can tell I have made sure everything was exactly the same for every round and I even weighed the power twice with two different scales a RCBS 1010 and a Hornady LNL dispensing system. So I do believe they were exactly 25 grains each.
When shooting the rounds I noticed that the velocity on the chronograph varied a bit more than I expected here are some of the velocities that I experienced.
3012
2979
2988
2945
2966
3034
3014
3037
3017
2983
2956
I would've expected much less variation but then again I am new to this so I don't really know. I'm drawing from shooting factory rounds through a chronograph and only experiencing about 2 to 3 ft./s difference between the rounds (Black Hills) but we only shot three rounds.

Propellant: Benchmark
Primer: CCI small rifle bench rest
Bullet: Berger 52 grain match varmint .224

So if anyone could please enlighten me what I should expect for variations in velocity it is much appreciated.

Thank you

 

[Walkalong]

An ES of 56 is not all that bad, although I would like to see better, and usually do, in .223 and its ballistic twin the .222 Mag. Results on target are more important. If you were shooting 1000 yards then the ES would need to be better.

Welcome to THR

 

[reloader_rob]

Thank you Walkalong, and I do intend to shoot 1000 yard but not with the .223, I also purchased equipment for my AIAW 300 and plan to load AMAX 208 Gr with H1000, and am currently wondering how I should expect better consistency in the velocity when I don't seem to know why I'm not achieving it in .223. It's a mystery of the day for me.

 

[rfwobbly]

You didn't mention your brass. You need all the same brass because the internal volume varies from brand to brand.

 

[BADUNAME37]

Your velocities are in line with the results I get from my .223 and my 22-250.

 

[reloader_rob]

I did not think that would factor. The brass is new Lake City from midwayusa.
What factors does this affect?

 

[mbruce]

Hey Rob

When you say everything is exactly the same...what specifically is everything?

From what I read perfection seeking benchrest shooters weigh every bullet, every case, every primer...they load to the exact same specs...everytime. Or get as close to it...

 

[reloader_rob]

I did not think to weigh the items individually. So when I said everything is the same I basically said everything between each of the rounds was the same brand of primer and same brand of brass and same bullet and same propellant with same propellant charge.

I can see how a bullet that had a heavier weight would definitely fly slower than one with a lighter weight however, I would have thought be all the same "bullet" they would all be the same weight.

What factor with a primer with a different weight play? Is it not just the first stage in the chain of detonation; it's only purpose to ignite the powder?

Thanks again guys, you got me thinking about things that I did not know to think about.

 

[jenrob]

Just some food for thought and a couple things that have work for me. I use Mag primers in all my rifle applications. I cut my powder back at first then work the load up. this dropped my spread by a few feet. I was leary the first time I did this.

Learned that from a gentleman at a gun show> a freind of mine sell reloading supplies and I went to the show to visit and pick up some small and large rifle primers. he only had Mags in the large and told me that I could use them to just drop my charge a 1/2 to full gn and work up. I told him I would wait and this is where the older fellow came in. he said that the mag primers burn longer and hotter thus lighting the powder of more consistant. after a while of talking I took the large mags home and started loading. After that small brick of standard primers was gone I switched them to mags also.

Another thing that has got more consistant velocities is useing a dispenser rather than weighing out each load. this was also just a couple FPS better on the spread, but then again when things go haywire the spread is more so on the dispenser. I use an RCBS charge master for most, but this is something to try it is time consumming so sit and enjoy.

Set your dispenser up to load weight that you want. dispense into your scale try and weight each load if they are within .3gr of each other leave them alone if there is more of a difference than that poor it back in and continue loading this same way. just cause the powder weighs different it came out of a sized cylinder (dispenser rotor). this is what I like to call volume loading within reason. it acts the same as seating the bullet in more takeing up more space (volume) in the case. In which will change your velocities.

 

[Walkalong]

There are folks here who shoot 1000 yard in competition. They can be a huge help for that. If i recall correctly, they are looking for ES numbers around 10 or less.


In Benchrest we did not weigh primers. That doesn't matter. We did prep the heck out of brass and sort into groups. I liked to keep batches of brass within a five tenths spread. Say 107.0 to 107.5, but would settle for a spread of .6 or .7 if need be. Most never weighed bullets. We did buy custom BR bullets, such as Barts, or Knights, though, which are held to excellent tolerances.

 

[USSR]

Thank you Walkalong, and I do intend to shoot 1000 yard but not with the .223, I also purchased equipment for my AIAW 300 and plan to load AMAX 208 Gr with H1000, and am currently wondering how I should expect better consistency in the velocity when I don't seem to know why I'm not achieving it in .223. It's a mystery of the day for me.

At least one of the ES problems with your .223 loads is, you are not using good brass. For LR shooting like you want to do with your AI AW, you want a load with an ES of <= 20, and an SD of <= 5. Lapua brass is the best brass made in all the cartridges I shoot. It's pricey, but if you can afford an AI AW, then it should be no problem for you. Winchester would be my 2nd choice for brass, but you have to match prep it, whereas the Lapua is pretty much load and go. Whatever brass you use, weigh them and set aside the light and heavy ones for fouling shots. IMHO, their is no sense in weighing primers or bullets; there just isn't enough difference to make it worthwhile. Regarding the bullets, one thing you might want to do is, measure them from the base to the ogive and segregate them that way. One last thing, make sure you trim all your cases to the same length each time you resize them. Hope that helps.

Don

 

[788Ham]

The comments by jenrob on post #9, I'll have to 2nd that! The sm. mag rifle primers is all I've ever used in the .223 cartridge. I was told years ago to do this, more consistent ignition each shot, has worked for me!

 

[reloader_rob]

I didn't have any idea that the brass was going to make that much difference. I had figured that if I did good case prep that they should all be the same no matter the manufacturer because they would all then fit the specifications of size.
I have weighed some of the Lake City brass and have found a good bit of variation in its weight.

Here's a question for you guys, what brass does Black Hills use for their 300 Win mag? Rather than purchasing several thousand rounds of unfired Winchester brass, I wonder if the Black Hills brass I have collected will be just as good to reload. I think I still have 800 or so factory rounds of theirs that I need to shoot.
I looked on the head stamp and there's no indication of the manufacturer of the brass but when shooting through a chronograph this is where we had less than 3 ft./s difference for three shots and two of those shots were exactly 2995 and the other was 2993.
What are your collective thoughts and just reloading this brass versus purchasing new unfired Winchester brass?

 

[RidgwayCO]

Three shots are not enough to draw a valid statistical conclusion about the brass, or the load for that matter...

 

[reloader_rob]

Oh, thats something else I did not know. I was under instruction from a ex-Special Boats Service sniper and this is what he did to get an avg for generating a drop chart. Then we validated the chart.

So in general, how many shots do you call enough to get your average?

 

[RidgwayCO]

To generate statistically-relevant data, you need at least 10 shots, and more is always better (although you start to get into the overkill area with more than 25 shots). YMMV.

 

[USSR]

Here's a question for you guys, what brass does Black Hills use for their 300 Win mag? Rather than purchasing several thousand rounds of unfired Winchester brass, I wonder if the Black Hills brass I have collected will be just as good to reload. I think I still have 800 or so factory rounds of theirs that I need to shoot.

Black Hills brass is made by Winchester, so you are GTG with that brass.

Don

 

[murf]

reloader rob, try remington no. 7 1/2 primers with that load (reduce and work up). may tighten things up for you.

murf

 

[Walkalong]

I had great luck in .222 Mag with 2015 and Remington 7 1/2's.

 

[cfullgraf]

Oh, thats something else I did not know. I was under instruction from a ex-Special Boats Service sniper and this is what he did to get an avg for generating a drop chart. Then we validated the chart.

So in general, how many shots do you call enough to get your average?

I know enough about statistics to be dangerous. From scratch, you need a large sample size of a process to establish the capability of the process. Once established, small sample sizes can provide sufficient information.

In the case of the military, I am sure they have established the capability of the rifle with a particular ammunition. Then when changing lots or getting a new supply of ammunition, it is easy to establish new data.

If the ammunition used changes substantially, they would have to start over again.

We did this kind of stuff in industry and could tell if our process was headed out of spec with testing only a few samples. Fortunately for me, we had other folks that crunched the numbers on the large sample, capability studies.

 

[GTS Dean]

I agree that brass is the likely culprit. I sort by headstamp, then after prepping the cases, by weight, then by powder capacity.

 

[USSR]

Just to give you an idea as to how much difference brass can make. I took some LC M72 Match brass and match prepped it every way I could, including neck turning, and it still couldn't keep up with straight out-of-the-box Lapua brass.

Don

 

[reloader_rob]

Thats pretty interesting Don. Makes me want to know just where the difference is in manufacturing.

I was looking at the head stamps of some BH "Blue Box" 223 and its LC like the other lake city I bought. Now the BH in the Gold Edition 300 I have is all stamped BH.

GTS Dean, your not out of the Weatherford area are you?

Rob

 

[reloader_rob]

Today upon recommendations of using better brass I bought some Norma and loaded 10 rounds with Berger 52 Grain and 10 rounds with Hornady 52 Grain AMAX all seated the same and all with exactly 25 grains of benchmark and all same CCI bench rest primers.

The results of the Hornaday showed a FPS of about 100 ft./s difference.

The Berger never read which it is curious to me as to why? Does anybody have any thoughts as to why none of the Berger loads read?

Also does anybody have any suggestions of how to get the variance on the feet per second down further?

 

[gamestalker]

I've spent many hours trying understand variances in velocity, and concluded that there are numerous elements responsible for the seemingly unlikely results. When I began my quest for consistent velocity, I thought that my powder charge was the key, I wasn't even close. Barrel temparature between shots, the bullets physical characteristics, brass, OAL relative to the lands, and lots of other stuff way out of my intellectual league.
As I have progressed through this quest, I've discovered numerous elements, some within my control, and others less so. I discovered some bullets vary in weight, considerably. I then considered that if bullets have inconsistent weight issues, it's only reasonable to think they have other inconsistencies that could add to the spread in chronographed velocities. Olgive consistencies is another obvious issue with most bullets. It's my beliefe and experience, this element can be managed to some extent by adjusting OAL on each bullet in relation to the lands.
So far I've only touched on the bullet and powder charge, of which the latter is less effective on consistencies than I originally thought. The density of the powder charge will effect how pressures build, and when they peak too. In my personal experience, this is where brass is relative but can be managed with some sucess with compressed powder charges. Deffinitely not the only option, but it can help.
Next, I managed the distance to which the bullet contacts the lands by minimizing that distances to zero on each bullet seated. Again this is not the only way to achieve better consistency, but it does work.
I have stabilized velocities in all my rifle's by using this method and have managed to keep pressures within acceptable limits. Try to find bullets that are more physically consistent in olgive and weight, try to work with slow burning powders that will give you safe compressed charges, seat to the lands, and don't start measuringyour velocities until the barrel has warmed up some, and cooled some between each set with some cinsistency.