Chronograph problem or reloaded/shooter problem

[GaryD]

I have a custom 6.5 creedmoor that I have started reloading. With hornady 140g Amax match grade factory loads I have shot in the 3's. Hornady prints the powder load on the box and I started working around that set up. Copied that load 41.5 grains of H4350 and with + and- 0.2 grains. Also substituted 140g bergers for Amax. Seating depth same as measured to ogive on factory loads (jammed as determined by the sharpie method). The 41.7 grains had the best group 1.6 in at 300 yds.

To aid in my endeavor to be a better shooter and reloader I purchased a chrony beta master chronograph. I reloaded with H4350 41.7 to 42.3 grains in 0.2 increments

Results at 300yds 14 mph wind at 3 o'clock

Two factory rounds 2682, 2707 fps

41.7 g. Avg 2664 es 83.98 sd 30.21. Group size 1.6 same as before

41.9 g. Avg 2704 es 22.40 sd 8.72 Group size 1.2 best group

42.1 g. Avg 2669 es 22.81 sd 9.79 Group size 3.8 worst group

42.3 g. Avg 2724 es 44.63 sd 17.44 Group size 2.3

41.5 g 2769, 2780 to compare to fps with factory loads

Question is should I believe the chrono data? In some cases more powder gives less speed and the least powder the fastest speed although only two shots vs 5 for groups. The worst extreme spread resulted in a close second best group which one would expect to be the worst?

Opinions?

Maybe I just opened a can of worms?
Maybe I should just take that can of worms and go fishing

Gary

 

[BoydAllen]

One of the possible variables that you may not have considered is neck tension, as evaluated by the force that it took to seat the various bullets. How even did they feel as far as the amount of effort it took to seat the bullets?

Another thing that is worth looking at is how much variation there is in case weight. A lighter case will generally have more capacity than a heavy one, and produce less pressure with the same powder charge, all other things being equal.

Did the factory loads list the primer? What primer did you use?

How did you weigh your loads? Scales can vary considerably in their accuracy.

How much longer than the point where they touch are the bullets seated. If you seat bullets a bit too long, to what length are they pushed back when you chamber a round, measured off the ogive. Were does the seating depth that you chose fall between just touching and where the bullet was pushed back to?

The common use of "jam" is an incorrect usage of a term that was originated in the short rang benchrest game, some decades back. It is a noun, that is the OAL (now measured off the ogive) that is the longest that a bullet may be seated to, (using the neck tension that loads are to be assembled with) without being pushed back into the case. Bullets are properly described as being seated a specified distance off of the lands, or touching, or a given distance longer than touch, or alternately into the lands. If one is to the maximum sustainable length (jam), one says that he is seating at jam length, or simply at jam. The range of possible seating depths that are available between touch and jam varies with the shape of the bullet. Throat, or leade angle is also a factor.

In any case, I would believe what your chronograph is telling you and consider that you are probably working with small samples at each loading and that in some cases the effect of one or more variables, other than powder charge, may have been responsible for the readings that you cannot account for, For instance if scale error, case weight, and neck tension all go in the direction that tend to reduce velocity, you could end up with a small sample average that did not increase with charge weight.

 

[amlevin]

Another consideration is the distance from the chronograph. Sometimes the muzzle blast can cause erratic readings. If not from the gases themselves triggering the sensors, then from moving the tripod.

I had a "shooting chrony" that I had to just retire because it was fussy over lighting conditions and also gave inconsistent readings.

Now use a different brand with IR sensors and use a heavy weight to stabilize the tripod. Make sure that the chronograph is level as well and the bullet is traveling across it in the same plane as previous shots. Vary the trajectory and readings will vary as well.

 

[BoydAllen]

There was a typo/mistake/brain fart in my previous post. The correction is shown in red.

 

[GaryD]

Thanks Boyd. The factory primer was a federal 210m and I used cci benchrest primer br2. I was using a RCBS charge master. I waited after the charge was thrown to check for over weight remove the pan from the scale and reweigh. I also use a 105 g bullet to check after the calibration and use it about every 10 loads to check for scale drift.

The neck tension is something I was aware of. I made a dummy load and measure neck diameter and used bushing .02 smaller. I also use a lee hand press to seat the bullets. I think I get a better feel for tension rather than using a bench mount press. I did not notice much difference in seating force.

I have not weighed the brass but I still have them in the order fired and can compare weight with velocity tonight

 

[GaryD]

AM

I stepped off about 15 feet from the muzzle to the chrony. The tripod is a flimsy and may have contrubuted to the problem.

One thing I forgot to mention with each grouping shooting at the bulleye is a raise in elevation of 1.2 inches and right .9 inches right to left wind. This was least powder to most powder. Which I would expect with an increase in velocity

 

[Killshot]

Results at 300yds 14 mph wind at 3 o'clock

Two factory rounds 2682, 2707 fps

41.7 g. Avg 2664 es 83.98 sd 30.21. Group size 1.6 same as before

41.9 g. Avg 2704 es 22.40 sd 8.72 Group size 1.2 best group

42.1 g. Avg 2669 es 22.81 sd 9.79 Group size 3.8 worst group

42.3 g. Avg 2724 es 44.63 sd 17.44 Group size 2.3

41.5 g 2769, 2780 to compare to fps with factory loads

I wouldn't think that five rounds with such high spreads would print that well at 300yds but what do I know....

Follow any advice Boyd offers.

 

[amlevin]

AM

I stepped off about 15 feet from the muzzle to the chrony. The tripod is a flimsy and may have contrubuted to the problem.

One thing I forgot to mention with each grouping shooting at the bulleye is a raise in elevation of 1.2 inches and right .9 inches right to left wind. This was least powder to most powder. Which I would expect with an increase in velocity

Your last paragraph pretty much hits on why I use my Chronograph at the end of my load development. I first work "on paper"(targets) and once I have a load that yields good accuracy I then set up the "chrono" and shoot no less than 25 of the finished rounds over it. This gives me a larger dataset to derive the important information from. I use Muzzle Velocity for my external ballistics chart calcs. The rest, ES, SD, and MAD are at that point only footnotes as I have the results on the only piece of paper that matters.

In the beginning I was totally stymied over loads that produced single digit SD's but groups far larger than some of those with far larger numbers.

Using my method I've found that more often than not, that first shot at a new distance, using the chart for setting my scope, is dead on. YMMV

 

[normmatzen]

I, too, have a Beta Master. When I first got it, my results were not really consistent. I would also get some shots that would not register.
Well, I did the "Unthinkable!" I read the directions!

I found that you only use two shade pieces on clear days and only single up-rights. I also wrapped some blue painters masking tape around the up-rights at the, by the manual, sweet spot.

I haven't looked back! I now get VERY consistent results. Also, a stiff tripod is very important to keep the chroney from jiggling. I have a very stout tripod I use for my spotting scope AND the chroney. Just consider the results you get using a jiggling tripod under a good spotting scope, it is useless!

 

[jlow]

I, too, have a Beta Master. When I first got it, my results were not really consistent. I would also get some shots that would not register.
Well, I did the "Unthinkable!" I read the directions!

I found that you only use two shade pieces on clear days and only single up-rights. I also wrapped some blue painters masking tape around the up-rights at the, by the manual, sweet spot.

I haven't looked back! I now get VERY consistent results. Also, a stiff tripod is very important to keep the chroney from jiggling. I have a very stout tripod I use for my spotting scope AND the chroney. Just consider the results you get using a jiggling tripod under a good spotting scope, it is useless!

This is good advice. An additional piece I can give based on experience is that if you put a laser boresighter on the rifle, it will allow you to be sure that the round will travel down range at the proper height and midpoint between the sweet spots – that will give you good consistent readings and if you have your rifle on a rest, almost no chance of shooting the chrony or any of the other parts of the chrono.

Because of the distance the chrony is from your rifle, you will be surprised how far off you can be from the sweet spot even if you go and look down the barrel from the chrony……

Just remember to take the boresighter out of the barrel before you shoot ;D One way to avoid this problem is to use the boresighter's bag to block the trigger when you have it on the barrel.....

 

[tunered]

There was a typo/mistake/brain fart in my previous post. The correction is shown in red.

I thought it was gonna be this. Scales can vary considerably in their accuracy.

 

[DougMH]

I have a custom 6.5 creedmoor that I have started reloading. With hornady 140g Amax match grade factory loads I have shot in the 3's. Hornady prints the powder load on the box and I started working around that set up. Copied that load 41.5 grains of H4350 and with + and- 0.2 grains. Also substituted 140g bergers for Amax. Seating depth same as measured to ogive on factory loads (jammed as determined by the sharpie method). The 41.7 grains had the best group 1.6 in at 300 yds.

To aid in my endeavor to be a better shooter and reloader I purchased a chrony beta master chronograph. I reloaded with H4350 41.7 to 42.3 grains in 0.2 increments

Results at 300yds 14 mph wind at 3 o'clock

Two factory rounds 2682, 2707 fps

41.7 g. Avg 2664 es 83.98 sd 30.21. Group size 1.6 same as before

41.9 g. Avg 2704 es 22.40 sd 8.72 Group size 1.2 best group

42.1 g. Avg 2669 es 22.81 sd 9.79 Group size 3.8 worst group

42.3 g. Avg 2724 es 44.63 sd 17.44 Group size 2.3

41.5 g 2769, 2780 to compare to fps with factory loads

Question is should I believe the chrono data? In some cases more powder gives less speed and the least powder the fastest speed although only two shots vs 5 for groups. The worst extreme spread resulted in a close second best group which one would expect to be the worst?

Opinions?

Maybe I just opened a can of worms?
Maybe I should just take that can of worms and go fishing

Gary

I certainly DO NOT trust my Shooting Chrony anymore. I was shooting MOA vertical groups at 300 yards down at Quantico, VA and had chrony ES on 30 rounds of 80. I can't imagine shooting MOA at that distance with that ES reading. So, I just bought a used Oehler 35p off of eBay.

I suppose you could try shooting through both your chrony and a buddy's chrony and take an average reading? Basically that's what the Oehler 35p is. It's a chrony with a verification chrony. If the readings are to far apart, the printer puts an * beside the reading on the printout and you should not use that in your calculations.

With any chronograph, I believe it's critical to shoot through exactly the same area of the triangle on every shot. If you had say 4 targets in a square down at 300 yards where you would be changing your muzzle angle, you would not get as accurate a chrony reading is if you were shooting a single target. That may seem obvious.

 

[jlow]

The OP said “although only two shots vs 5 for groups” which I take that some were 2 round groups and others 5 round groups…..

Ask any statistician and they will tell you that your N size i.e. the number of rounds you used to get this data is much too small to make anything of the differences you are seeing. The machine will mindlessly calculate average, ES, and SDEV for you but that does not mean the data is meaningful.

Just saying.....

 

[GaryD]

I think Boyd made a good point on empty brass weight. The 5 shots with the highest es had the lightest and the heaviest empty brass wt and matched up with the slowest and fastest for the group. In my mind I would not have thought it would have made that much of a difference but now i will consider that in my reload routine. I don't remember the exact weight difference but was over 2 sd for the heaviest and 2 sd less for the lightest( total of 30). If I remember correctly from stats is significant fact.

Compound that with the poor 20 dollar wal-mart tripod I feel that could be the problem

That's why I like this site. Enough people hear to share their been there done that this is what I did to fix it in a professional manner.

Gary

 

[BoydAllen]

As has been mentioned, when shooting small numbers of shots with each load, it is probably best to only consider the average and extreme spread, and to forget about SD. Do you know how SD is calculated? and what it represents? Because chronographs calculate it, the term gets thrown around a lot, but as the previous poster stated, with small samples it is basically meaningless.