Dans Posts

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If anyone has some of Dans info saved and would like to post it here, it would be appreciated.
Would like to keep it civil, and not ramble off on another tangent, but I won't get upset regardless of any way it winds up.

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Bullet Drift is to the right
100 Yards 1.3? 1.3 MOA
200 Yards 3.0? 1.5 MOA
300 Yards 5.1? 1.6 MOA
400 Yards 7.8? 1.9 MOA
500 Yards 11.5? 2.3 MOA
600 Yards 16.1? 2.7 MOA
700 Yards 21.9? 3.1 MOA
800 Yards 28.4? 3.5 MOA
900 Yards 35.7? 3.9 MOA
1000 Yards 43.2? 4.3 MOA

Something I had saved from a previous post. If memory serves me Dan T came up with these numbers.

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Don McDowell wrote:
Dan that might be a fairly close approximation. But I'm also thinking that humidity gets to playing an part in both wind and elevation. Then you throw in some mirage, and about all a fella can say is Thank god for sighter shoots.... I've been thinking that a photographers light meter reading and humidity, temp, and barometric pressure would be a great help if noted in a persons field book at each match or range session.
Don, Humidity can be ignored for our purposes because it has very little affect on our projectiles' trajectory. The full range of humidity, from 0% all the way to 100% humidity only accounts for a 4% change in air density at a given temperature and barometric pressure. Temperature and barometric pressure changes account for most of the change in air density. So, those are the two conditions we should track if interested in better understanding how those fluctuations affect our bullets' trajectories. A number of guys have done tests to try and better understand how light angle affects the targets apparent image. And, all that I've talked to found that the apparent image does change location throughout the day. The way they tested this was to clamp a quality rifle scope to a sturdy bench with the cross-hairs on a target at some distance. They looked through the scope regularly throughout the day and found that the cross-hairs moved about the target; well, actually the target's apparent image changed with the light angle. I've found that early in the morning and late in the afternoon, especially in the winter when shooting north, group location will change quickly. For instance, if shooting a 10-shot group and only getting the first 5 rounds off before a ceasefire, taking a 10 minute break before resuming shooting the group, there will be two separate groups. That has happened often. Certainly mirage has a considerable affect on apparent image. The image moves in the direction of the mirage, as most marksmen know. A boil is when there is no wind, a 12 o'clock wind or a 6 o'clock wind and there is light on the target. It moves the apparent image up, so aim low in a boil. I know that common wisdom says don't shoot in a boil; but, I've got to say learning how to shoot in a boil can really put points on the old score card. The controversy concerning what happens to a target that goes from sunlight on it to cloud-cover shadow has been discussed often. My take is simply this; if there was no mirage running then there will be no change in bullet impact from that change because the apparent image didn't change location. If there was mirage running before the cloud cover put the target in the shade then the apparent image will change to opposite the direction the mirage was running._________________Cheers....DanT

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Eric,

Your load's MV is about 1,300 fps. Here are the elevation as well as windage for a 10 mph, 9 o'clock wind, with elevation zero at 100 yards.

Range---Drop--Windage---Velocity
(yd)----(MOA)--(MOA)-----(ft/s)
0--------***-----***------1303.4
100-------0-------1.5-------1208.7
200----10.6------3.0-------1130.2
300----22.8------4.4-------1067.6
400----36.2------5.8-------1017.6
500----50.7------7.0--------976.3
600----66.1------8.2--------940.9
700----82.5------9.3--------909.7
800----99.8-----10.3--------881.7
900---118.1-----11.4-------856.0
1000--137.2-----12.3-------832.2
1100--157.3-----13.3-------810.1
_________________
Cheers....DanT

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Gents, Along with the silhouette-distance, windage-correction algorithm I posted on this thread, there is also the issue of the bullet's "spin drift" and its affects on perceived wind correction requirements. To refresh some memories, spin drift is caused by rapid bullet rotation; drift to the right from a right-hand-twist barrel and to the left for a left-hand-twist barrel. This phenomenon is not linear, it is a function of time-of-flight squared as well as the bullet's spin-rate (the faster the more the drift due to greater yaw of repose angle as spin-rate increases) and bullet length (the longer the more the drift due to more surface area to be acted on by differential pressure caused by the forward motion of the bullet and its yaw of repose angle.) I've heard it said that wind from 3 o'clock does not have as much affect on a bullet's trajectory as 9 o'clock wind with respect to horizontal displacement. When that is heard the thought that comes to mind is the speaker's rifle does not have its sights setup properly to cancel spin drift; that is, spin drift is adding to and subtracting to windage corrections. From 9 o'clock it is adding, from 3 o'clock it is subtracting. When we consider spin drift at silhouette distances, the distances in question in this thread, we should first look at horizontal displacement due to just spin drift at the c, p, t and r lines. To set the parameters for this discussion, assume that the rear sight-ladder is perpendicular to the front-sight bubble; that is, a "square" sight setup. And, let's further state that the load is cutting the "X" at 100-yds when the rear sight is set to mechanical windage-zero. Finally, HPT's load composed of the 45-cal, Paul Jones Creedmoor, 540gr bullet, launched at 1140 fps will be the target load, bad pun, eh...oh darn it's a double intender too. Oh, almost forgot, barrel twist is material, so HPT's twist-rate is specified to be an 18-twist. Next, a review of the effects of spin drift from 100-yds out to the c, p, t and r lines. At 200 meters, spin drift will horizontally displace the bullet about 0.4 MOA to the right from the 100-yd zero, rifle with "square" sight setup. At 300 meters, spin drift will horizontally displace the bullet about 0.8 MOA to the right from the 100-yd zero. At 385 meters, spin drift will horizontally displace the bullet about 1.1 MOA to the right from the 100-yd zero. At 500 meters, spin drift will horizontally displace the bullet about 1.6 MOA to the right from the 100-yd zero. As you can see, the above is not trivial, especially at the turkey and ram lines. To further get the point across, here's what wind corrections in a 10 mph 9 o'clock wind would look like for a rifle setup as described above. 10 MPH 9 o'clock Wind Chickens: 3.4 MOA Pigs: 5.8 MOA Turkeys: 7.1 MOA Rams: 8.6 MOA Now, compare that to a 10 MPH, 3 o'clock wind: 10 MPH 3 o'clock Wind Chickens: 2.6 MOA Pigs: 4.2 MOA Turkeys: 4.9 MOA Rams: 5.4 MOA As you can see, not setting your sights up properly can have a deleterious effect on your ability to score well in a rapidly switching wind condition. If the wind is fairly stable in direction one can just "chase the spotter", but when the winds start switching around the clock, far too many are toast if their sights are not setup properly. And, some rifles I've examined have had the rear staffs tilted to the right; that's even worse than having the staff perpendicular to the front bubble. We want our staffs tilted to the left to cancel spin drift so that our mechanical zero is our calm-wind zero at each yard-line we shoot at. Finally, it can be said; the further our targets, the more important proper sight setup becomes. The effect increases exponentially with range so at 1,000-yds we are talking 38.8" of right drift just from spin drift when shooting HPT's load. It is this writer's belief that a substantial amount of confusion arises from spin drift's effects on windage corrections. Setting one's sights to cancel this phenomenon might be the subject for future posts._________________Cheers....DanT I have no special talent. I am only passionately curious. Albert Einstein

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Anyone have a "ballpark windage" rule for shooting Silhouttes? I'm looking for something like the following:

These windage corrections are for 9 or 3 o'clock winds.

_0.3__MOA X mph at chickens

_0.5__MOA X mph at pigs

_0.6__MOA X mph at turkeys

_0.7__MOA X mph at rams

Shooting 540gr Creedmoor @ 1140 fps

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Fouling Control Challenges: Blow-tubing vs. Wiping

There are several factors that affect one's ability to control BP fouling when using a blow-tube, or, for that matter, when wiping between shots. Each time a round is fired, heat from powder combustion as well as bullet friction accumulate in the barrel. And, in the direct sunlight radiant heating also contributes to increased barrel temperature, a root cause of fouling control challenges. After a string-of-fire, one's barrel can become quite hot. It is this heating that makes fouling control, when using a blow-tube, difficult. Humidity also plays a part in the fouling-control effort; the lower the humidity for a given ambient temperature the more challenging it is to control fouling and thereby maintain match-grade accuracy during a string-of-fire.

So, to get a handle on barrel heating and cooling, both go on at the same time; let's analyze what is going on during a string-of-fire when shooting in the direct sunlight. First, as was stated already, heat is absorbed by the bore from the hot gases produced when the powder burns as well as from bullet friction and radiant heat from the sun. Our typical barrel steel is 4140 or 4150 chromoly. It has a thermal conductivity of 42.7 W/m-K (watts per meter per degree Kelvin.) Stainless steel 416R, what is typically used for stainless-steel barrels in the US, has a thermal conductivity of 25.1 W/m-K. The bottom-line is that chromoly steel absorbs 70% more heat than a stainless steel barrel, all other things being equal, each time a round is fired. Another consideration is that heat absorption is a function of the bore's surface area. For a given steel type and barrel length; a 45-cal tube has 63 % more surface area than a 35-cal tube and therefore absorbs 63 % more heat than the 35-cal barrel. So, the takeaway is: the larger the caliber, the hotter the barrel will become compared to a smaller caliber, all other things being equal. And, chromoly will absorb 70 % more heat than a stainless steel barrel each time a round is fired all other things being equal.

When shooting a string-of-fire in the direct sunlight, like we do in BPCR Target-rifle Matches, radiant heat from the sun is also a factor, concerning how much a barrel will heat-up. Once again, stainless steel gets the nod for its lower radiant-heat absorption. A simple test performed years ago at the Raton silhouette range is instructive. Two rifles, one with a blued 4140 chromoly barrel and another with a bead-blasted 416R stainless barrel were pulled from their cases at the same time and placed in a rifle rack behind the firing line. After ? hour in the sun the chromoly barrel was quite warm. The stainless barrel was still cool to the touch. When shooting a match in direct sunlight, this radiant-heat-absorption difference between chromoly and stainless has a meaningful effect on fouling control.

As soon as a barrel is hotter than the surrounding ambient air it will start to radiate heat in its inexorable effort to attain thermal equilibrium; be at the same temperature as the ambient air. The larger the difference between ambient and barrel temperature, the greater the radiation effect, Mother Nature abhors disequilibrium.

While a chromoly barrel absorbs more radiant heat than a stainless barrel, it also radiates heat at a higher rate due to its thermal conductivity, that is, it transfers heat from the interior of the barrel to the surface to affect faster cooling through radiation, more efficiently. However, the delta between its absorption and radiation of heat is larger than for stainless steel. Chromoly absorbs more radiant heat than it radiates, which is why it warms in the sunlight without any rounds being fired. That is why a blued, chromoly barrel will be quite warm to the touch when placed in the summer sun at Raton and a stainless barrel will not. It should be noted that the added heating of a chromoly barrel is also due to the bluing. A polished or bead-blasted chromoly barrel will not absorb as much radiant heat as a blued one.

There is also a difference in exterior surface area, a contributing factor in how quickly a barrel will cool-down, between an octagonal barrel and round barrel. If both barrels are of the same weight and length, the octagonal barrel will have about 3 % more surface area and therefore cool a bit more quickly, but the difference is trivial compared to other effects that differentiate the heating and cooling characteristics between chromoly and stainless steel.

So, the takeaway from the above is; large-caliber, blued, chromoly barrels present more of a fouling control challenge than a smaller caliber, bead-blasted stainless steel barrel for a given atmospheric condition, all other things being equal. And, barrel heating is a primary effect when it comes to controlling BP fouling and thereby maintain match-grade accuracy during a string-of-fire.

One last thought. A bead-blasted chromoly barrel will have much more surface area than a polished one and therefore cool-down quicker even if it is blued. I've seen bead-blasted chromoly barrels that have been blued; they look pretty cool to this crank.
_________________
Cheers....DanT

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After a few weeks in the Deep South, I can say it sure is full of fine folks. The Doc and I worked on load development for his 10-twist, 38-50 Shiloh while I was staying at his place. Results show fine promise for an outstanding silhouette and mid-range position rifle. The rifle's off-hand hold is excellent (28" barrel length) and its accuracy and very light recoil will allow for the finest off-hand shooting. And, at the top of both games, the winners typically score very high in the off-hand portions. Chip Mate and Rick Moritz have been putting "the hurt" on their fellow competitors due to their excellent off-hand scores using 38-50's in Mid-range Position matches. Well, Al Sledge also. In a big silhouette match, full of hungry "top dogs," high chicken scores are a must.

Doc Lay's current match load is as follows:

Neck-turned (0.0105") 38-50 brass formed from 30-40 Krag (Remington) cases
F150 Match large pistol primers with 0.006" watercolor paper wad under primer
55.0 grains of Swiss Fg
0.060" LDPE over-powder wad
0.003" bullet neck tension
Paul Jones Elliptical # 2 with Mini-grooves cast in 20-1, 367 grains
Estimated MV = 1,230 fps

The rifle is a Shiloh Sharps silhouette model with a 10-twist barrel, chambered with the DanTDesigns 38-50 match reamer.

The load development was done at Doc's range behind his house at 100 yards. Doc and I also went to his tree farm to test the rifle at 500 meters. Doc later tested the rifle at his pig and turkey lines with excellent results. Below is a picture of Doc's 500 meter group. No effort was made to adjust for the changing wind conditions and there were no wind flags on the range. The bottom, horizontal line of bullet impacts was fired when we had a fish-tailing headwind. The top 3 impacts happened whenever the wind switched to a tailwind twice so those top 3 impacts were not sequential. The vertical difference between the two groups is about 6 inches

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HPguy420 wrote:
Not sure what you're trying to say. From the 1,000-yd line the trajectory apex is about 35 ft above the line-of-sight for a typical 45-90 launching a PJ Creedmoor at 1,300 fps. What is "time in flight deflection?"


All I was saying was actual "drift" factor would only be the same as dropping bullet from 35 feet and seeing how far off it lit. ( not very far) so the "deflection" has to be from other factors. (as you point out.)

Dropping a bullet from 35 ft would take the following time to hit the ground:

Time = Square Root of [ (2 x distance) / acceleration of gravity]

Time = SRof [(2 x 35 ft) / 32 ft per sec squared]

Time = 2.3 seconds, substantially less than the time-of-flight from the 1,000-yd line.

Launched at 1,300 fps from the 1,000-yd line, a PJ Creedmoor in 45-cal would take about 3.145 sec.

The way wind deflection was first understood was by subtracting the actual time-of-flight from the vacuum time-of-flight. The vacuum time-of-flight is simply the time for the bullet to go a distance in a vacuum; that is zero drag. So, at 1,300 fps, the PJ Creedmoor would take:

ToFVac = 3,000 / 1,300 = 2.307 sec

Actual ToF = 3.145 sec

If we subtract ToFVac from ActualToF we get 0.837 seconds. Now, say we have a 10 mph, 9 o'clock wind. If we multiply the time difference by the wind speed we get:

10 mph = 10 x 5,280 x 12 = 633,600 inches per hour = 176 in/sec

Multiply time difference by how fast the wind's going in inches/second to get:

Wind Deflection = 0.837 sec x 176 inches/sec = 147.31 inches of lateral bullet movement over 1,000 yards.

When I spot for a shooter shooting the 45-cal, PJ Creedmoor I give them 1.5 MOA per MPH of 9 o'clock wind from the 1,000-yd line; 1.4 from the 900 and 1.3 from the 800-yd line. Pretty close, eh? And, when a computer simulation is run using 0.420 for PJ's BC and 1,300 fps, the wind deflection at 1,000-yds is 148.6 inches. For the Paul Jones Money Bullet I give; 1.0 MOA per MPH of 9 o'clock wind from the 800-yd line, 1.1 from the 900 and 1.2 from the 1,000-yd line.

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MV, Bullets, Group Size, Distance: The Nexus Perplexus

Well, it finally happened, the 10-twist, 38-70's bullets were arriving at the 300-yd, mid-range target in the "Nasty Speed Zone", just above the speed of sound. Numerous top marksmen have experienced this phenomenon; great groups at close targets, horrible groups at medium distance targets and excellent groups at distant targets. The likes of Doc Lay, Arnie Moos and Gerry Podesta, all top marksmen in their own rights, have had loads that performed as above described. Doc Lay has a 38-72 load that will shoot ? MOA groups at the ram and turkey lines, but he can't buy a pig with that match load. Gerry Podesta has the same problem with his 40-82 Crossno. My 38-70 match load shoots lights-out at 200 and 600 yards, but snucks big-time at 300 yards, go figure. Well, figure I've been doing and the conclusions track with ballistic theory. And, one variable is common with all of their, and now my, observations: high MV loads that deliver their bullets to the target, just above the speed of sound, suck big-time in the group-size department.

The transonic region is a very "sticky wicket," as our British brethren would say. As bullet speed drops below about 1,200 fps, the turbulence it is affected by increases rapidly (exponentially) until the bullet speed drops below the speed of sound. If one's bullet is in that speed range as it hits the target, their group size will be increased dramatically.

Here's last Saturday's case in point for your perusal. At 200 yards the 38-70 load in question was producing sub-MOA accuracy with all shots on-call. At 300-yds the accuracy took a dive big-time. Breaks did not produce on-call holes though the target. At 200 yards my score was 100-5X with the first half of the string mostly 10's until the wind was figured-out. At 300 yards the wind was about the same, but the score sucked at 91 with 1X. All breaks were excellent, but the bullet holes through the target were not on call. At 600 yards the rifle performed spectacularly. Even with an "Oh Snit Shot" that was in the 7-ring at 6 o'clock (on call) I managed a 93-2X in much more difficult winds compared to the wind challenge at 300 yards. And, we shot the 500-yd target instead of the 600-yd target.

The conclusion of all this is; if one's bullet speed is between about 1,200 fps down to the speed of sound just before it hits the target, accuracy might just be in the proverbial toilet

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Re: 38-72 Winchester
by DanDeMan on Tue Dec 18, 2012 6:51 am
Boats,

I found one email I sent to a friend about how to form 38-72 brass and load ammo.
====================================================================
Here's the only die set to order:

http://www.buffaloarms.com/38_72_Win_RC ... x?CAT=4042

Process for forming 38-72 brass from Hornady’s 405 Winchester brass.

1. Run your press ram all the way up and then screw the FL die all the way to the top of the shell holder and back it off 2 revolutions.

2. Very lightly lube a piece of brass.

3. Size the brass about 1/2 way.
4. Remove the brass from the shell holder and wipe off any accumulation of lube in the neck transition area that is now forming. If you don't, you will dimple the neck due to too much lube. Now finish sizing the piece of brass.

5. Trim the piece of brass to about 2.580" so the mouth will not hang-up in the chamber from being too long. This sacrificial case is used to set the FL die for minimum sizing.

6. Try to chamber the brass. It should not chamber quite yet
.
7. Screw in the die body 1/4 turn, resize and try to chamber the brass.

8. Repeat this process until the brass just chambers and comes out easy. When the brass is getting close to chambering go to 1/8 turn increments as the objective is to minimally size the brass for an excellent fit in the chamber. By doing this you will eliminate the need to fire-form the brass and be able to go straight to load testing.

I strongly recommend the following concerning loading for the 38-72 and 38-70 after thousands of rounds fired in testing and even more in matches. A fellow top BPCR shooter has been working on his new 10-twist 38-72, but did not listen completely to my recommendations. His results have NOT been satisfactory yet. During each conversation we've had over the past month he has repeatedly reported doing something I told him not to do with the expected less than stellar results. I wish you better success.

1. Use Federal Match Large Pistol primers.
2. Use an over-primer-wad: Punch out 0.008" thick wads (I use water color art paper that can be found in most office supply stores in the art section). Use a 45-cal wad punch for this operation. I fold a sheet of the paper so that every punch produces 8 wads. Place a wad in the shell-holder of your priming tool, slide the case over the wad and punch the primer through the paper so the over-primer-wad is in the primer pocket on top of the primer. This also backs the LP primers out to where a LR primer would be.

3. Use only Swiss 1.5 powder; between 68 and 72 grains depending on bullet and loading technique: slip-fit vs neck-tension.

4. Use a 0.060" LDPE. It must not be below the neck-shoulder junction.

5. For slip-fit bullets use between 30 and 60 thou compression. Once the compression goes much over 60 thou you will get lots of vertical from MV variation. Don't even bother to try. And, don't seat the bullets out so far that the chambering operation pushes the bullet back into the case more. The rounds should chamber with just a little thumb pressure with the bullet seated out as far as possible.

6. For neck-tension use 0.002" NT, zero powder compression and a 0.060" LDPE that is no more that 0.002" in diameter larger than the base band of the bullet. If the diameter of the wad is too large you might get case stretching.

7. Properly cleaning the cases after each firing is a must.

8. Properly annealed cases, after each cleaning, work best.
I have gotten the best accuracy using 2 thou neck-tension. Slip-fit has also delivered excellent accuracy, but I'm looking for the best accuracy possible so have gone to using neck-tension.

Hope this helps and let me know how your progress goes.
Cheers,

Dan Theodore

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I'm currently working with a new 40-72 Winchester Browning Highwall. It is my second 40-72. The first had a 13-twist, chromoly, Lilja barrel screwed to a Steve Earl Wesson # 1. I shot my highest 900 and 1,000 yard scores with that rifle; a 97-5x and 94-2x respectively down at Phoenix. The current 40-72 has a 14-twist, stainless steel barrel by Douglas. Going stainless for BPCR's is the only way to go. I'll not bore you with the details other than to say I'll never have another chromoly barrel again. And, I've got a number of converts that feel the same. Stainless barrels can be "blued" so they look like the typical BPCR. Douglas made a special run of 8 land & groove barrels for me and several buddies. The barrel has 0.040" wide lands and 0.120" wide grooves to minimize base distortion, the steering part of the bullet once it takes flight.

The 40-72 is an oh so easy to load for BPCR cartridge. And, one just opens a box of 405 Winchester brass manufactured by Hornady and starts load-testing. The original BP round, the 40-72, has the same body dimensions as the 405 Winchester. When that smokeless round came out, Winchester made the rim thicker and larger in diameter so the 46,000 PSI round could not be loaded into an old 40-72. A 405 factory round would surely burst the mild steel barrels on the old 40-72's.

Here's a link to one of my 40-72 threads. I'm hpguy420 on the Shiloh site and one of my companies is called DanTDesigns. You'll see that on reamer and bullet prints.

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Much cogitation has sapped the consciousnesses of more than a few shooters when it comes to bullet-weight-variation and its effects on Point-of-impact, POI. To set my mind straight, I undertook a series of tests from the 1,000-yd line down at the Coalinga Gun Club back in 2004. Granted, the test was done using a BPCR; but, the results still apply to HP Silhouette, And, I might add, gravity is always on and it affects random vertical dispersion by the square of the bullet's time-of-flight. So, the BPCR tests from the 1K-line are much more extreme than a high-velocity, high BC bullet fired over just 500 meters. TOF for the BPCR bullets fired from the 1K-line is in the 3 second range. A HP round fired to 500 meters has a TOF of less than 1 sec. OK, I need to get some real results...back in a Flash, Jack...a 6.5, 140 A-Max launched to 2,800 fps has a TOF of just 0.694 secs when shot at rams, a 7mm, 168 SMK launched to 2,400 fps has a TOF of about 0.854 secs. To be clear, the effects of gravity on random vertical dispersion caused by bullet-weight-variation is not linear, that is, the BPCR bullet takes 3 seconds to travel 1,000-yds while the 168 SMK takes 0.854 secs to traverse 500 meters; so, 3/0.854 = about 3.5 times the effect, NO, that is not how gravity works. The actual effect is that the BPCR load is about 14 times more affected than the SMK load by bullet-weigh-variation with respect to random vertical dispersion, because random vertical variation goes by the time-of-flight squared.

So, here's the skinny. A method of casting "underweight" bullets was developed to cast lead-alloy projectiles for the test. When the bullet mold is bathed in a propane flame until all of the surface moisture is driven-off, high-quality bullets can be cast that will be underweight. As the mold warms from the hot alloy, the bullet weighs will increase. The result was that bullets that had a 5-grain range were used for the test. The "normal" bullet weight is 404 grains. It was launched from a 38-70 rifle sporting a 10-twist barrel. The powder charges were carefully weighed as well the brass properly annealed. The result, completely unexpected by this riflecrank, was that the target didn't care how much the bullets weighed. All bullets went into the same group from the 1,000-yd line.

Now, for BPCR's, carefully controlled powder-charge weights do have a substantial benefit in reducing random vertical dispersion at long-range.

So, the takeaway from that testing is, who cares if your high BC, high velocity bullets have a grain or two variation in weight, as long as they are not deformed.
Cheers,

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After experimenting with, doing load development for and using in matches many different BPCR cartridges, the 40-72 is the most flexible and easy to load for, IMHO. I've gotten excellent accuracy using very mild loads, 400-gr bullets launched to 1,210 fps (accurate, mild silhouette and mid-range load,) all the way to driving a 466-gr bullet to 1,360 fps for long-range work.

Below is a recommended reamer design for the 405 Hornady brass. The design is for barrels with 0.400"/0.408" bore/groove diameters. Bullet design depends on twist selected. The chamber reamer was designed to use tapered bullets for long-range work so they can be seated out further for increased powder capacity. Lighter bullets with all driving bands at groove-plus-0.001" (0.409") allow the bullet to be seated deeper into the case to suck-up case capacity. Also, the reamer will cut what I call a moderately tight chamber. The guys that have chambered rifles with this reamer design have reported excellent accuracy. As a matter of fact, one of my Aussie buddies just had a 40-72 rifle built that has a Ron Smith, gain-twist, stainless steel barrel that finishes at a 13-twist. This week he reported MOA groups at 300 meters during some more initial testing and his last match with it was quite successful. Some of the Aussies that frequent this sight might know him, Bruce Moulds.

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Bruce,

Here's the equation to determine bullet drift that's a function of bullet spin.

3.4 X t^2 = Bullet Drift in Inches

So, the equation is 3.4 times the time-of-flight squared to calculate bullet drift. In our case the typical time-of-flight is about 3 seconds from the 1,000-yd line. So, that would be 3.4 x 9 = 30.6 inches of bullet drift over 1,000 yards or about 3 MOA (half the width of the target.)

My LR rifles are set up so that the calm zero is the mechanical zero at 800, 900 and 1,000 yards. Bullet drift from spin, also know as "spin drift", is nonlinear. That is, its rate-of-drift (like acceleration) increases with range which can be seen in the time-squared variable in the equation.

I've developed a relatively easy way to set the rifle's sights up so this can be accomplished. First, the rifle is locked into a vice or placed in a cleaning rack, so it will not move easily, with the front-sight bubble centered-up. With the eyecup removed from the rear staff, a magnetic level is attached to the side of the staff that doesn't have the elevation knob so the level will be parallel to the staff. The bubble should be about 6" to 8" above the staff pivot point. One wants to shim the staff-base to the left (shim(s) under the right side of the base when standing behind the rifle) so that the bubble just touches the right side of the line in the bubble when standing behind the rifle. Once this is accomplished; shoot at 100 yards off-the-sticks so that bullet impact is about 1" to 1.5" to the left of the X. Move the front sight to accomplish the appropriate bullet impact. This procedure is for right-hand-twist barrels. Reverse the process for left-hand twist barrels.

If you follow the above procedure, you should be pretty close to matching your mechanical zero with the calm-wind zero at LR distances. My rifles are set up so that at each LR yard-line, if it is calm, the sight can be put on mechanical zero and the bullet impact will be in the middle of the target horizontally. Shooting in boils is a good way to work on fine-tuning the front sight.

If one has their sights so setup, it is a distinct competitive advantage, especially when the wind is switching badly. During a major wind-direction change, one can go to their mechanical zero and estimate just one wind direction and magnitude instead of estimating what the value of the wind was (direction and magnitude) and then adding that estimate to the estimate of the new wind value (direction and magnitude.) That is 4 estimations and twice the error as compared to just going to one's mechanical zero and making just the estimate for the new wind direction and magnitude.
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