Producing accurate charges

[Richard]

For those looking to get very accurate charges!

What I am illustrating is only for someone interested in long range precision rifle shooting with top shelf equipment. For general purpose shooting, hunting with the average factory rifle, this degree accuracy in weighting charges is not necessary.
When shooting 600 and 1,000 yard bench rest matches, Extreme Spread in velocity is critical to group size. Typically, at 1,000 yards, a 25 fps difference in velocity of shots can equate to about 3.5” of vertical spread. In the case of my 6.5 x 284 improved with a 140 gr. VLD bullet at 2900 fps, a shot with a velocity of 2925 and one with 2875 can relate to 7” of vertical. AND, that does not take into consideration what might be happening with the wind which gets hard to control or read at that distance. At least, if you can eliminate or minimize the vertical spread, you have a better chance of getting a good group.
One of the things that can help control vertical is to have your powder charges very equal. There are also other factors, but consistency of powder charge is critical. As you can see from the photo, I do have the RCBS Chargemaster which measures to 1/10 grain. This however, can be to the very high side or the low side of your setting and actually relate to almost 2/10 of a grain difference. To minimize this, you really need a scale that can accurately measure to a few hundredths of a grain. There are “lab” quality electronic scales that can do this, but they do not come cheap. They start at around $250 and go up. They can also be quite finicky.
In talking with other shooters, some with the high dollar lab scales and others without, I came to the conclusion that with a little work, you can achieve the same results with a standard “tuned-up” balance beam scale. To tune it, you simply have to make sure the agate “v” ways that the beam rests in is perfectly clean and free from any junk or oil. Second, you need to take the edges of the steel “V’s” that rest in the agate and sharpen them with a very fine stone. In this condition, you should be able to see movement in the beam with as little as one to two kernels of powder (stick powder).
In the picture, you can see I have a RCBS powder trickler setting on a stand with a little cross rail. This allows the side of my hand to rest on the rail while I turn the trickler stem. What I do, is use the Chargmaster to throw a charge 1/10 grain light of my target load. I then dump that charge into the pan on the beam scale. I can then trickle, kernel by kernel until the beam balances. For ease of seeing, I glued a pin on the scale which will overlay the beam pointer. I have a magnifying glass also to help with eye strain. With everything set up at eye level, it is simple and quick to trickle up to my load. I have checked this set up with my buddy’s lab scale and found it just as accurate without the cost.
The Chargemaster is a great powder measure, but for long range bench rest, it is just not as accurate as I would like. For everything else it is perfect.
Richard

[cfvickers]

I use the lyman dispenser and scale, and get 1-6 FPS Extreme spread from my 6.5-284, but it is more of a hunting load. Extremely accurate but near max load of RL17 and at 3204 FPS for a 130 gr. VLD it can't be kind to the barrel if shooting more than three shot strings before a complete cool down. But it is shooting 1/2 inch or better groups at 200 yards. I don't think I can hold it any steadier than that with my rest setup, which isn't much to talk about.

[Richard]

If you can do 1 to 6 fps EVERY time, you are doing great. Here, you can't just do three shots...............That is with match ammunition. Our 600 yard matches involve four targets with five shots each. Everyone comes pre-loaded (as opposed to the short range BR guys who do their loading at the range and ES's are not critical?) So you can see that you will need to have every round as close to each other as possible. ONE shot can open up any one of your four groups and put you out of the running.
When you chronograph, how many shots in the string do you do? Also, what type of chronograph do you have? If you are dealing with anything less than the four foot screens that Oehler uses, your results are going to be off by as much as 10 to 20 fps. My friend in Louisiana has permanent stanchions to put his Oehler 43 ballistic chronograph photo cells on and they are set 24 ft. apart. This allows him to get in the one to two fps range. He has a similar set up at 300 yards. (He is a retired engineer if you get my drift?) ES's has a lot more to do then with just powder volume
Its case capacity, neck tension from case to case, smoothness of the neck interior, seating depth, primers, different lots of powder. So if you are getting 1 to 6 fps, you should get into the benchrest game because it don't get much better than that. The majority of BR shooters are tickled to death if they can "consistently" stay under 10 fps.
All of these scales like your Lyman, my RCBS, the Pact............they all are only good to 1/10 of a grain. That's the reason for my set up.
Richard

[cfvickers]

Yes it is every time, but as you know well, there is a whole lot more that goes into it than charge weights. I verified the load with 5 shot strings across the chronograph 6 to 8 times, and at most I get an ES of 6, twice it was 1, most commonly 4 fps. But like I said with a load that hot I would never choose it for competition in any rifle. It is very near max load. less than a half a grain. If you ever work with rl17 remember that above 92 degreesF outside temp it starts to get pressure spikes and Te hotter it is outside the crazier your pressure will get. may do fine with one and the next blow a primer. But at any point when I am hunting the temp is well below 65 and I have no issues with the load at all. And it was chronographed at different temps outside as well. blew a primer when outside temp was 102 first shot but velocity was 3203, right in the range it should be. I know, at 102 I shouldn't have tried it but I did anyway. I was not shocked by the result. I fully agree with you on the effect of charge weights on spread and standard deviation though. but you also have to have everything else exactly the same as well.

[cfvickers]

By the way, I only have 2 cheaper chronographs but from everything I have read ES and SD numbers on them are pretty accurate it is the overall accuracy of the velocity its self that could be off. Mine both read the same velocity with my ammo so I figure I am not too far off. what I am saying is that you may read a velocity of 3204 but it really may be 3180, but, if it is set up the same every time, your displayed es or sd should only be a fraction of a fps off. basically it reads velocity the exact same way every time. it isn't going to bounce around and just give you crazy readings unless you have a lighting issue. If 3204 was really 3180 3204 would be 3180 tomorrow if it was set up the same way and correctly so. Where the ohler comes in it helps with the calculation of bullet drop and making up range cards and the such.

[Richard]

Your forgetting the main features............the "check" screen and the wider spacing of the photo cells. In effect, two separate readings.........One to verify the other.
The problem with the cheaper chronographs are the short spacing between the photo cells. This causes the "timer-clocks" to have more trouble picking up the start of the bullet hitting the first screen and then stopping after crossing the last screen. What with variations in components along with chamber temp's, I am finding it a little suspect to your claims of those readings EVERY time? I'm just saying? Been around this game a long time and have a little bit of that "Doubting Thomas" in me!
I am also saying this: While your gun/load "might" be producing very low ( 1 to 6 fps) ES's, its the chronograph itself that can not read that accurately? I have shot groups at 600 and 1,000 yard that displayed negligible vertical stringing yet, those loads only showed under 20 fps ES. That amount should have been somewhat strung. Meaning the load was good but my Pact was telling me different? These affordable chronographs are only meant to get you in the ballpark. When you have photocells 24 feet apart like my friend, that is when you get serious.
Richard

[cfvickers]

I am not, here to try to convince you. In contrast my point was that the small variation you may see in charge weights with less expensive scales doesn't make that great of a difference. People win competitions all the time with far less expensive gear than what you describe I know a few of them. and my gear is more expensive than one of the best that I know. If the lighting is correct I disagree. It will have some offset that is, but unless you are shooting at a different angle or something any two identical projectiles at identical true velocities will read thesame because it reads it the same way every time.

[cfvickers]

the oehler is more usesr friendly and easier to get accurate reading because of more sensors set farther apart. But as long as the cheap ones are calibrated correctly and you are shooting directly across the sensors there is no reason that it would not be acurate. How much education do you have in electronics? Mine is extensive, and I can say that the cheap chronos have more limitations, but the oehler has limitations such as size, and inconvenience. The small cheap ones must be set up exactly right to get a good reading. Basically the oehler gives less erroneous readings and compensates a little better for the angle at which the bullet passes over the sensors. but at the same angle every shot you wil get the same reading if velocity is identical. I am elitest about some things myself, but just say you like it better, and that will be good enough. Now how did I eliminate those variables over several days shooting across it? I have a stand with an indention permanently set in front of my bench where the chronograph sets. I shoot from the same position every time. Therefore I should get the same readings, if they are the same. I had a200 yard range in my back yard at the time I developed that load.

[cfvickers]

Ok, I have done this, as i believe I stated on two separate chronographs, 6-8 checks probably 5 on a chrony beta and 3 on a prochrono. this should eliminate erroneous readings and count for 2-3 tests with 10-15 shots each based on your logic that more sensors and screens??? makes it more accurte. The screens were sometimes there, sometimes not. what chronograph requires screens if you have some cloud cover??? None. I reread that statement because I just got home, before I was at work and stopped at your calling me a liar. You want to compare notes and knowledge about electronics and how these things work, I'm down. You bring the oehler propaganda book you have been reading and I will bring a head full of real world knowledge from 2 years of school and 6 years of working on whatever was placed in front of me. The goal of the screen is simply to give the photocell something to contrast the bullet so it will pick it up. the one in the oehler may be stronger but if it sees it it sees it, and the clock starts, when it passes over the second one, the clock stops, now, it takes the time from one to the other with the distance between them,and converts it to feet per second. it is very simple math and not hard to figure, it doesn't take a horrible expensive piece of equipment to do it accurately. what that horrible expensive piece of equipment does is helps to eliminate operator error. It should if designed as I believeit is, take 3-4 readings. time from first to last, 1st to 2nd, and arent there 4 sensors in that? 2-3 and 3-4. if one of the readings doesn't match the velocity of the other three it can throw that one out and still give you a good reading. where only having 2 sensors, you get one shot at the reading. now, if it is calculating on the assumption tht the sensors are 12 inches apart, and they were 12.1 it would give you a slower reading than actual. However, that reading would be no further off percentage wise than the next shot or the one after that or the next 500, if the bullets are even close to the same path. This is why it can give you the wrong velocity but be correct on the deviation to within a fraction of a foot per second. now remember 12.1 inches when it should be 12 even would put it reading roughly 30 fps slow at 3,000 fps. so one must also remember that the lower the ES/SD the MORE ACCURATE the ES/SD reading actually is. because as it increases the amount of error increases exponentially. Now that we have had a lesson on the workings of chronographs, I am going to sleep. have a great day. Understand that I am not arguing that the oehler or pact chronographs are not more accurate, I am saying that when figuring ES/SD numbers the extra accuracyyou get from them will not win or lose any shooting contest unless a guy was using a cheap one with a bad battery. By the way, a low battery slows down the processing and this is why you get bad readings with bad batteries.

[Richard]

Now let me ask you this? My friend out in LA. who is the retired mechanical engineer and has done more testing with everything concerned with both F-class, short and long range benchrest and anything about guns a ballistics. Here is a guy I would put up against the best of the best. Why would he................set his Oehler 43 ballistic chronographs (photo cells) 24' apart? Both at point blank and 300 yards. Yes, he has two! We have driven together to matches and roomed together on numerous occasions. He informed me the reason was that the further apart the photo cells (sometimes I happen to call them sky screens - which I never use) (I have a shield I use to keep the sun out of the cells) At our range, the sun always comes in from the right side and if you looked at my set up, the cells are set down inside a wooden box.) The more accurate the readings are since the timer clock can better decipher the start/stop. Which makes sense. He feels that two feet spacing of photo cells can allow for as much as 25 fps difference in shot readings.
This person is highly regarded in benchrest circles for the extreme testing and inovating he does. I know him...........I do not know you? Since I have been on this board the past four years, I have separated a lot of Wheat from the Chaff; There is a lot more chaff here than wheat! And until I get a feeling that the person knows what they are talking about, I view them with a lot of skepticism. So just call me doubting Thomas for the time being. Like I said, I have a feeling my loads have lower ES's then the chronograph is showing. I can say this when I get my targets back and see maybe 1/2 to 1" of vertical at 600 yards and yet my readings would say it should be more than that? I just do not think the chronograph is picking up correct readings due to their short spacings as my friend indicated? Unfortunately I do not have a range in my yard or I would have permanent mounting posts for at least 8' spacings.
And, getting back to the dispenser? Take a lab quality scale that can weight 2/100's of a grain and see how accurate your Lyman is? The 600 yard shooter of the year, who I shoot with every month, uses a similar set up and many others are using the lab scales.
Richard

[cfvickers]

As I am saying, I am not arguing its overall accuracy. That is unquestionable. My point is the percentage of difference will be the same every time. Maybe you misunderstand him. 24 inch spacint can be as much as 25 fps off on a velocity reading. What I am saying i that it will be tht same 25 fps off every time provided that the chono is 8in a fixed position each and every time. 24 ' spacing is better, absolutely. if the bullet is not traveling exactly parrallel to the length of the chronograph you will be way off. But if niether the gun or the chronograph changes positions the percentage of error will remain the same each time making your velocity reading off yet your es/sd numbers still accurate. I don't know how to demonstrate it short of a shooting a video and posting it, and I cannot do that right now Now if I could afford an oehler chronograph, I would have one. but I cant so I rely on meticulous setup of what I have to get accurate readings.

[Richard]

No, he is saying it is the inability of the clocks to accurately read the shadow starting the first clock and stopping it with the second clock. The space is just too short to do this accurately. With the 24' spacing or any longer spacings the start/stop clock can be more definitive. I would also have an Oehler if not for the $575! ;D
Just like Five shots tell a better story than three? No matter how much Tar busts my balls ;D
Richard

[cfvickers]

Lighting can have a negative effect on a cheaper chronograph. due to spacing. yet when the variables are equal the readings will be equally accurate or inaccurate. One variable will have one effect. that effect will not change until that variable changes. like shooting across the chronograph when a cloud is blocking the sun, then again when the cloud has passed. these shots cannot be accurately compared. I learned this early on. I am as scientific with my testing procedures as I can possibly be because I have chased enough ghost problems as an electronics tech to know that all variables must be considered when working with them, and I have fired enough rounds for accuracy to know how many variables there are when trying to get an accurate load.

[esshup]

Richard:

Keep an eye on e-bay. I picked up a a model 35 for slightly less than $500. What I didn't expect was that it came in a 12" x 10" x 52" hand made wooden case, padding that was cut to fit the oehler pieces exactly, with 3 extra sensors (complete with shields, etc.) and some extras that I can't think of right now. It isn't the 35P, but for the $$, I'll write down the info after every shot.

[Richard]

I was almost to the point of getting a 35p but procrastinated too long Then there were no more! I spoke with Ken Oehler at the NRA show in Charlotte two years ago and he indicated he was making a run of about 75. Then I heard the price? Could not justify it At the previous $350 price I was ready to lay down my bucks but not $575. One of my new friends who joined my club just got one and the first time out? Shot thru three of the black plastic photo cell guards. This was actually his first chronograph also. He switched guns and had to lower his rest but neglected to lower the photo cells. Cost him $30 for three sets of the plastic guards.
I think I am pretty much resigned to live with my PACT to put me in the ballpark I want to be with my velocity. My targets at 600 yards will tell the story on my ES's. That is, unless I happen to stumble on some "rat killin' deal"! ;D
Richard

[esshup]

Richard, my first experience with a chronograph was back in the mid '90's and it was a 35P chronographing and patterning (yes, it was a LOT of counting) almost 1,000 shotgun rounds. After that, I always wanted one. I really lusted after the Model 43 with the acoustic target, but couldn't swing the $$.

I really believe in the check screen, and believe the wider screen spacing capability is a must. (No, I'm not trying to stir the pot)

Once I've got the load dialed in, I have put the Chrony right in front of the target and had the Oehler by the gun. I haven't shot either of them yet, but have blown off half of the the acetate covering over the screen on the Chrony.....

I've since made a aluminum box for the Chrony to fit in that has a 30° angled piece of 1/2" thick Lexan in front of the read-out. The bottom of the box has an adapter that fits into a camera tripod. Easy to adjust and hold. The spotting scope allows me to read the readout at 100 yds. The Chrony will fold up inside the box for storage, and the metal rods will fit right along side of it. I hope that the lexan will provide some measure of protection if it gets hit.

[Richard]

Maybe one day I will stumble into one at an auction, garage sale, flea market or local "Want ad press"? Then my problem would still be protecting the photo cells from the sabots.........And, its not just the front one, but all three! Right now, my Pact is nestled inside a wooden box with rubberized material and bracing on the front. The photo cells sit down inside the box. It is pretty durable since my added re-reinforcements ;D
Richard
dougsmessageboards.proboards.com/index.cgi?board=gear&action=display&thread=2343

[esshup]

That looks good and sturdy, nicely packaged in one box to keep everything together. Have the skyscreens held together so far? I saw where you whacked one and cracked the PVC with a sabot.

Take a piece of 1/2" I.D. heavy walled rubber hose (auto parts store) and slip it over your rope handle. Makes it easier to carry.

[Richard]

Actually, I have not used those sky screens in well over a year. The problem at our range is the sun wants to come in from around 3:00 to 5:00. Not overhead. So the sky screens would not be much of a help. I have since built a large shade the slips in the side of the box to shield the photo cells from the sun glint.
As far a carrying the box? I only have to remove it from my truck about 10 feet ;D.......before it gets put on the tripod. It then lives inside the cap on the bed of my truck until the next outing.
Richard