Many other gunwriters, including the dean of them all, Jack O'Connor, often belittled the stories of super-accurate rifles as occurring far more often in the typewriter than on the range. I can recall writing a piece that I called 'The Accuracy Myth' about 25 years ago in which I came to about the same conclusion.
- How Far Apart Are Rifle Barrel Accuracy Nodes Located
- How Far Apart Are Rifle Barrel Accuracy Nodes In Neck
My best example of this is using Pyrodex RS on a clean barrel with a Knight Wolverine. The first shot out of a clean barrel can be as much as 6' out of the group at 100 yards. With that first fouling shot on the barrel, 1' groups are very common but on a clean barrel, that first shot can be anywhere in that 12' circle. To assure some standardization always use a distance of either 10 feet or 15 feet to the center of the sky screen support which will give a 'measurement distance' of 10 or 15 feet. Also, keep the chronograph electronics out of the path of direct muzzle blast. For some tips on chronographing and possible problems click here.
Developing An Accurate Load
I have often been asked what is the best method to develop a load for afirearm. On the surface, the task appears daunting as one seems to befaced with having to trying hundreds of combinations in different loadingmanuals to find one that works well in your particular firearm. However, as we will see, there is an easier way.
- Almost all modern medium hunting cartridges are capable of good accuracy at these ranges. Face reality, I won’t be shooting across valleys, that’s just unethical. Any 30.06, 308, etc, will be accurate. I don’t worry about it much, barrel length and rate of twist didn’t matter to the deer and bear I take either.
- If I wanted a super-accurate rifle I would start with the best-quality match-grade barrel I could find. Such a barrel will cost $500 or more. There are many entire production rifles that cost less.
The following is based upon information in part from an article on chronograph usage by Jim Ristow, ofRSI Software, and is excerpted here with his permission.
First a little theory
Every barrel develops harmonic vibrations when a cartridge is fired, similarto a string being shaken. A gun barrel's vibration can be described as a 3-dimensional sine wave, or corkscrewmovement and is caused when the bullet is accelerated into a rapid spin by therifling.
It is impossible to entirely eliminate barrel movement. Even a thickbarrel's muzzle will move with every shot and any velocity variation will alter wherethe muzzle is located as the bullet departs. This random movement ofthe muzzle gives rise to increased group size. Most experienced gun buildersagree it is best to allow a barrel to flex. The idea is if the barrel'smovement can't be eliminated the next best thing is that it flexconsistently. That's why good shooting guns usually have their actions andonly the first inch or so of the rear of the barrel bedded tightly into the stock tohold the receiver firmly, with the remainder of the barrel free floated. In addition, short, thick barrels have wide(r) nodes so velocity isn't ascritical to achieving a sweet spot.
Because the velocity of the bullet passing through the barrel affects the wayit flexes accurate loads should deliver as consistent a velocity from shot toshot as is possible so that the bullet exits the muzzle at the same point in the'flex.'. You can control this to adegree but it is impossible to entirely eliminate shot to shot velocitydeviation. At around a variation of 10 to 12 f/s it may become almost impossible to reduce theeffect any further.
It has long been understood that barrels perform best within certainvelocity ranges. These velocity ranges are commonly referred to as a'harmonic nodes' or 'sweet spots'. The reason for thisis that the tensile strength (or the ability to resist further bending) of themetal alloy increases as it moves further away from it's static state. Thebarrel gets stiffer when it is forced to the extremity of its movement. Atthe point of maximum movement, slight velocity variations change the muzzlelocation less; resulting in lower shot dispersion and thus a smaller groupsize. What most shooters don't understand is the harmonic vibration is related to the mass of the bullet. Therefore, once the harmonic node(s) for agiven weight bullet is identified, a lot can be learned, if you know thevelocity.
There is also a new theory of 'barrel timing' being developed basedupon data obtained from strain gauges. Upon firing the chamber swellsslightly and an annular ring of expansion travels down the barrel causing thebore to expand slightly and this effect continues as the expansion reflects backand forth along the barrel diminishing with each passage. Initial datasuggests that not only should a load perform best at one of the velocity nodesbut that the bullet should not exit the muzzle at the same time that theexpansion ring reaches the muzzle as the slight increase in bore size adverselyaffects accuracy. Research on this is continuing and as more data comes inI will add it to this page.
How Far Apart Are Rifle Barrel Accuracy Nodes Located
In the days of yore (BC -- before chronographs), it was necessary to blindlyhunt for loads that worked. Once a good load was found, changing any componentcould render the whole process useless (since changing components varies pressure andvelocity) and one pretty much had to start from scratch if anything changed. Achronograph provides direct insight into what your loads are doing, and what you need to do to make them work better. You will be able to immediatelydetermine if a changed component produces velocity outside of the range thebarrel likes. In most cases simply adjusting the powder charge willcorrect the problem.
Anyone who handloads really needs to have a chronograph, especially if theyare serious about developing good loads. The best chronograph on themarket is the CED Millennium 2 Chronograph. It is extremely accurateand stable,interfaces with RSI's Shooting lab software, and can be fitted with infra-redsensors which will 'see' bullets under conditions (including totaldarkness) that would fail on other chronographs. While the CED is available from severalsources, if you order it from RSI you will always get the latest model along with the serialcomputer cable and some extras. By the way RSI will provide full support for CED unitspurchased from other sources, including support for the serial computerinterface port. To order a CED chronograph from RSI gotowww.shootingsoftware.com and tell him that Fr. Frog sent you.
By the way.... If you own a chronograph of any make and are havingproblems getting it to work properly clickhere when finished reading this page for some tips.
Step1-- Initial Load Development
Lets start from scratch and assume nothing is known about a good load for a particularfirearm. The only information we have is from load manuals. Also,time is valuable, since we probably don't have a range in our back yard. Even if we are lucky enough to have a place to shoot outside the back door, saving time bydoing things efficiently lets us enjoy other things in life. We will also assumethat your rifle's bore is clean and free from copper fouling, that your barrel'sbedding is correct, and that all screwsare tight on your rifle. Another thing to keep in mind is that it often takes several'fouling' shots from aclean barrel for velocities to stabilize so you should fire a couple of fouling shotsbefore starting load development.
Most reloading manuals list their loads starting with the fastest powders andwork down to the slower powders. The powders have been selected as suitablebased in part on the loading density so any of the powders should workwell. If you are starting out by having to purchase powder, select one ofthe powders in the middle or slow end of the loading data list suitable for the bullet youwill be using. For more information on load density and its effect onperformance see the in-depth article on RSI's site by clickinghere.
At your reloading bench prepare your brass for reloading. Sort yourbrass by brand or military manufacturer/date head stamp. Clean, resize, trim(nominally to .01' less than the maximum allowable case length as specifiedin your load manual--the actual length is not as important as is the lengths beinguniform),and prime about a 100 pieces of the same brand of brass with your favorite primer. (The brand ofcomponents you use are not important at this point as long as all the cases are thesame brand or military manufacturer/date head stamp and you use the same primersand bullets for all the cases.)
Check your loading manual and determine the maximum charge suggested for yourpowder. Then determine how much adjustment on the powder measure willthrow about 1 percent or slightly less of the weight of maximum charge ofpowder. (As an example, if the maximum load was 45.3 grains, you woulddetermine the amount of adjustment of the measure that would give you about a 4/10 to 5/10grain increment--often about 1/4 to 1/2turn of theadjustment). Then, set your powder measure to throw a charge in thelower third of the charge weight range as recommended by your loadingmanual. Also note the maximum velocity indicated in your loadmanual so you have some idea of when you are approaching a maximum load.
Use your preferred method to set your seating die so that bullets will beseated 10 to 20 thousandths off the lands or to the workable maximum overalllength if they will be used in a magazine fed firearm. It should be notedhere that it may be a good idea to check your seating plug to ensure that itbears only on the ogive of the bullet and not the tip. Becausebullet tips vary slightly in shape seating a bullet by means of its tip leads tovarying seating depths. It may be necessary to alter the seating plug by drilling it outslightly so itbears only on the ogive. Some manufacturers will custom cut seating plugsfor you.
Setting a seating die for the 'overall length' should bedone using on of the gauges that measure from the ogive and not the tip of thebullet. Sinclair and others make inexpensive gauges for this or you canfashion your own.
Head for the range with bag of primed cases, bullets, powder, powder measure, asingle stage press, a seating die, and a 'permanent' type marking pen. All you will be doing is throwing powder charges and seatingbullets, so how you mount the press and measure so it is useable at the range is up toyou. Some shooters just screw their stuff to a heavy wood plank. (For anifty idea on this see the end of this article.) Of course, you will also betaking your chronograph, rifle rest and 'sand bags,' your notebook andpencil, and hearing and eye protection.
Load 5 starting rounds and slowly and carefully fire them at an aiming point through the chronograph (weassume you have good bench shooting technique). Record group size, the velocity andthe standard deviation for the string. Increase the charge one'increment' by turning your adjusting screw on your powder measure as describedabove and shoot 5 more at a separate aiming point. Continue this process untilyou start seeing signs of high pressure or reach maximum velocity. If youget a really good group, load one sample round with that load and label it withthe marking pen beforeadjusting the measure so you can weigh it at home later (or if you can weighcharges at the range do so and record the charge weight).
As velocities increase you should see obvious changes in-group size. Itshould be readily apparent when you reach a velocity node the barrel likes.However, don't stop at the first point where you get a tight group as mostrifles have two or more nodes. As you pass through each node, groups willopen up again until you approach the next node. Stop only when you are atmaximum velocity or pressure. Once there, you should have identified roughvelocity nodes for the bullet's weight. It's now time to getserious. If you can weigh powder charges at the range you can proceedthere, otherwise it's time to head back to your loading room.
Step 2--Fine Tuning
At this point most of the drudge work has been completed and it is time forfine tuning. You should have a good idea of velocity nodes velocities but reallyhave not shot 'serious' loads. Pull the bullets from the sample loads thatproduced the best groups and carefully weigh the charges. Load at least 5more rounds of each 'node load' using your best reloading techniqueand another 5 each just over and under that charge (say 1/2of the initial 'increment). Return to the rangewith your loaded rounds to validate what you have learned and if possiblealso determine the velocity range/width of each node.
While loads at the different node velocities will probably all perform well,if you are developing a target load which you will be shooting a lotyou may want to develop your load around the lower velocity nodes as a means ofkeeping throat erosion to a minimum. For a hunting load where you want toget maximum ranging and terminal performance concentrate on the higher velocitynodes.
Generally the thicker the barrel the wider the node. This is importantwhen working up loads that will be effective during different times of the year.Here in Arizona, loads that work in 110 degree heat often perform poorly in thecooler winter months. Conversely loads identified in winter months often producevelocities that are too high to work during the summer. Most of this isdue to changing interior ballistics due to temperature changes and not otherdifferences in atmospheric conditions. By identifying the width of yournodes you should be able to find a load the works all year long. Simplyuse the high end of the node you are loading to if shooting in significantlycolder conditions then when the load was developed, and load to the low end ifshooting in significantly warmer conditions then when the load was developed.
As mentioned before, changing components will affect performance. Bullets ofthe same weight but different brand or shape will produce different velocitieswith the same powder charge. This is due to differences in jacketthickness, bullet bearing surface within the bore, gas seal on the base due toshape, hardness of core material, etc. If you change bullet brands in your load,once you determine the new bullet's velocity is above or below the previouslyidentified nodes, all that should be required to make it shoot much better is toadjust the powder charge so the velocity is within the range your barrel likes.
Changing primers will also produce different velocities. Once you haveidentified what load your gun likes, it is simply a matter of adjusting the powdercharge if you change primers. In the final accuracy analysis the only substantial differencebetween primers may be the thickness of their shells. There is, however, a difference in velocity they producewith a given powder charge--sometimes 50 f/s or more. Is there a realdifference when charges are adjusted to deliver the same velocities? Forall but the most die-hard benchresters, probably no.
Most shooters are familiar with the measurement called 'standarddeviation.' Standard deviation (SD) is simply a statistical measurement ofthe uniformity of a sample of events. The standard deviation data provided bymost modern chronographs will help identify good loads. While it is notalways true that loads with the lowest SD produce the very smallest group, generallya good load will have a low shot to shot velocity deviation. (Velocity deviationcan sometimes be controlled by seating depth, neck tension, flash hole deburring,etc., and these arethings you can worry about after you get a good load and have some free time toplay around with the really fine tuning.) The bottomline is, however, that if you don't have data for comparison, you cannot fine tune your loads.
Obviously the degree of care in loading, component quality, and shooterability all impact group size. And, of course, not all guns are capable of shootingone hole groups--except those owned by some of the gun magazine writers. (Besides, if you want a 1-hole group just shootonce!) But, once you identify node velocities for aparticular firearm with a chronograph, much of the guesswork in working up loadscan be eliminated and a wide range of components can be made to providesatisfactory results. If you are happy with the load you can stop here.
If you are a stickler for details and want to wring the very best out of yourloads you can go a little further with some detail work to ensure maximumuniformity of your final working load. Weigh 10 unprimed pieces of yourbrass and find the average weight. Then weigh all the cases and cull anycases that deviate by more than about 3/4 gr from theaverage weight, or sort them into batches by weight. Uniform the flashhole using a tool like Midway's controlled depth flash hole deburrer. Ensure that the primer pockets are of uniform depth (but don't ream the toodeep) by using a pocket uniformingtool like Sinclair's. And then there is selecting the very best bullets.
For a more detailed look at what affects ammunition accuracy and informationon bullet quality and how to determine the very best bullets you can clickhere.
| Primer Pocket Uniformer | Flash Hole Deburring Tool |
Unless you are developing loads for bench rest shooting youshouldn't have to do anything else to ensure that your ammo is the best it canbe.
Fr. Frog's Rules for Reloading
1) You don't need to wring the last possible foot-second of velocity out of your firearm/ammunition combination. Better an accurate, consistent load than a blue screamer that won't hit the proverbial barn.
2) Pay attention to details, but unless you are a bench rest competitive shooter, there is a point of diminishing returns on the effort you put into your reloading for accuracy.
3) Changing anything changes everything.
4) Don't do anything stupid
5) Inspect, inspect, inspect.
6) Most gun writers are pathological liars
Some tricks along the way to make life easier.
Digital Scales -- Digital scales are convenient but they can sufferfrom drift and reading errors. You may be surprised just how inconsistentthey can be, with some brands of scales varying ± .2 gr or more with the sametest object repeatedly measured. I have seen some scales develop 5% ormore drift during use. For critical or max loads use a balance beamscale.
Try this with your (or your friend's) digital scale. Warm it up andcalibrate it according to the manufacturer's instructions. Then weigh abullet or some other object repeatedly (say 10 times) with the object centeredin the scale pan. Then repeat the test but place the object indifferent corners of the scale pan. It should be noted that dropping anobject to be weighed into the pan-- as opposed to gently placing it in thepan--can cause a wide variance in readings. You shouldperiodically do this test with your digital scale, because since it useselectronics rather than mechanics to weigh things it is possible for thecircuitry to drift or deteriorate over time. Be safe! Check frequently!
A Portable Loading Table --Besides having a chronograph one of the things that will make life easier isto assemble a small portable loading area. The picture below is probablyself explanatory. The whole unit is about 12' deep and about 24'wide (dimensions and style vary) and has a series of holes drilled to hold cases. It is fitted with aninexpensive Lee brand 'Reloader' press (used solely for bulletseating),an RCBS powder measure, a Dillon/CED electronic scale, and some spots for someextra seating dies and accessories. The whole assembly is very handy andtravels well. It sits nicely on the back bumper of a truck, or pickuptailgate secured with strap clamps or it can siton your shooting bench and secured with c-clamps. It is generally stable enoughto just sit on a bench or tailgate. Every serious loader should have one of these. I have discontinued making them for sale due to the ridiculous shipping costs.
If youwant to try building one yourself I can supply rough plans and a drillingtemplate for the case holder and die/shellholder blocks for $5.00. Theconstruction should be obvious from the photo and you can make it whatever sizeyou like. You'll need a table saw and a drillpress along with 3/8', 1/2', and 1' Fostner bits to drill the holes. Contact me by clicking here.
Chronograph setup--When setting up your chronographalways use the same screen spacing and distance from the muzzle for consistentresults. With modern high clock speed chronographs a 2 foot screenspacing works fine. To assure some standardization always use a distance ofeither 10 feet or 15 feet to the center of the sky screen support which willgive a 'measurement distance' of 10 or 15 feet. Also, keep the chronograph electronics out of the path of directmuzzle blast.
For some tips on chronographingand possible problems clickhere.
How Far Apart Are Rifle Barrel Accuracy Nodes In Neck
Dummy Rounds--Make up dummy rounds (without powder or primer) ofthe proper overall length for each bullet you use. Use these rounds to setup your seating die.
Use A Case Gauge-- Use a case gauge as sold by L.E. Wilson andDillon to set up your sizing die. This ensures that your headspace will becorrect and consistent. If a case dropped into the die has itsrim between the high and low steps on the gauge your die isproperly set.
Consistent Crimp - Get a Lee factory crimp dies for the calibers youreload. They provide a very consistent crimp which improves accuracy andare inexpensive. Just ensure that you don't over-crimp.
Wave diagram courtesy LymanCorpoation
Photographs and seater graphic © copyright 2001 by John Schaefer
Once You Have LoadedAmmo - Repackbox makes a very nice line of cardboard ammo boxes torepack bulk ammo in. Made from a stiff white board most of the boxes aresized to hold a standard magazine's worth of ammo (30 rounds of 5.56 mm and 20rounds of 7.62 NATO, etc.). Also available are packing aids stuff forpacking magazines and survival rations. Pricing and shipping are veryreasonable. Currently available for: 9MM, 10MM, 30Carbine, 380 ACP, 357 MAG, .40 S&W, 44 MAG, 45 ACP, 45 Long Colt, 5.56 X 45& .300 BO, 7.62 X 39, 7.62 X 51, 7.62 X 54R, 303 British (Also .30-40),30-06, 30-30 Winchester, and 12 GA.
For further information visit their web site orcontact Roger Small at 615.792.7947 or via email at rsmall(at) gijewelry (dot) com, or www.repackbox.com. Please tell Roger that I sent you.
As an aside, they also offer 'made in the US' GIreligious jewelry approved for issue. Made fromnon-magnetic, non reactive, bright finished, 100% 304 stainless steel. Thechains are the beaded 'dog tag' type, 24' long, and alsomade of 304 stainless steel. The back of each pendant is stamped with theirManufacturers 'CAGE' Code: 3YWL0.
Developing Loads forCartridges Without Published Data
Developing loads for cartridges that have nopublished data available can be a tricky and potentially dangerous job. The old method of measuring case head expansion has been proven to be unreliableat best. See http://www.shootingsoftware.com/ftp/dbramwell%20july%2019%2004.pdffor further details.
If you have data for a cartridge of similar case capacity andpressure data for it you can start with the loads that give pressures below thatof the unknown cartridge limits and slowly work up to load giving equivalent pressurebut this has to be done very carefully. Ifyou have a pressure measuring unit like PressureTrace II you are in a much betterand safer place. Start with data for a cartridge with a similar case capacityand then slowly work up from the lowest pressure loads to loads that do notexceed the unknown cartridges limits. If you are working with knowncaliber but using a modified non-standard chamber designs or rifling youcan see what is happening and work up safe loads rather than guessing. Theloading data for the DMR chamber design for the 6.8 x 43 mm (6.8 SPC) wasdeveloped using a PressureTrace II unit. You can get more information on thePressureTrace II by visiting www.shootingsoftware.com/pressure.htm.
Please email comments to Fr. Frog by clickinghere.
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Disclaimer
As far as I know all the information presentedabove is correct and I have attempted to ensure that it is. However, I am notresponsible for any errors, omissions, or damages resulting from the use ormisuse of this information, nor for you doing something stupid with it. (Don'tyou hate these disclaimers? So do I, but there are people out there who refuseto be responsible for their own actions and who will sue anybody to make abuck.)
Updated 2019-03-12
A standard reloading technique for creating safe ammunition is to start off with a “ladder charge” that starts at the “starting charge weight” and works up to the “max charge weight” in 0.3 or 0.5 grain increments for a given powder and bullet combination. Some data sources only list max charge weight and tell hand loaders to reduce by 10% to calculate the starting charge weight.
Now, in this load workup, a hand loader will normally find two distinct accuracy nodes, one near the starting charge weight, and one near the maximum charge weight. Generally, but not always, these charge weights will be around 8% apart. I don’t know why this happens for sure, but there are a lot of theories about barrel timing and harmonics that make plenty of sense.
So, between those two accuracy nodes, which will be MORE accurate? Here is a rule of thumb that is generally right; the one with the smaller charge weight for “position insensitive” powders such as extruded “stick” powders as it will perform more consistently across a wider temperature range (lower pressure means slightly less effect due to ambient temperature shifts), and conversely for harder to light off ball powders, the heavier charge for more consistent ignition (but you really need to watch the temperature swings for POI shifts). This rule of thumb isn’t hard and fast, but it should serve you well in choosing an accuracy node for your favorite rifle.
Now that I’ve given different advice for two different types of rifle powder, which powder is better? Well generally an extruded powder is easier to get good accuracy from, all else being equal. However all else is almost never equal, and ball powder is MUCH easier to run through a mechanical volumetric powder measure (although even bulky “hard to measure” powders like IMR 4064 have worked out well for me through a Lee Perfect Powder Measure for 308 Win size cases). For something like 223 Rem aka 5.56×45 I actually prefer a ball powder for most of my shooting needs when using a progressive reloading press. The charge weights are almost half of a 308 Win charge weight and so the margin of error for a few more or less kernels of powder is magnified in the smaller case. Yes you can get more accurate results hand weighing every single charge, but that takes a dang long time and I’d rather be shooting than reloading most days (although I have transitioned to a stick powder for High Power loads in order to get the most temp stable powder for the 55 degree swings I see across the competitive season).
One of the most seductive, and dangerous things, is when the upper accuracy node is just beyond max charge, and you can see groups start to tighten up as you approach max charge. I don’t recommend going beyond max charge in search of accuracy. I know people who do it, but the small advantage they gain from having a bullet go a little bit faster is mostly irrelevant at 600 yards or less.
On the flip side of going over max charge, going under minimum charge is also not recommended unless you are using a powder specifically tested for low density charge weights like H4895, and even then use the load data provided by Hodgdon for those low recoil loads. A light charge with a just slightly too heavy or slightly higher friction coefficient bullet is a bad combination to have some times.
Rarely in my experience, you’ll only get one accuracy node in a load workup, but it has been known to happen. What that means is that there is probably a node under min charge, and another over max charge. If you can fine tune the accuracy at that node, then all is good in your world.
But what do you do if you have a powder and bullet combination that doesn’t seem to have ANY accuracy nodes during your load workup? Change components. The darndest thing happened to Ryan at TLSR with a Savage Hog Hunter, it just wouldn’t shoot 165 and 168gr bullets worth a darn, but would shoot cheap 147-155gr bullets tight. Sometimes all the general wisdom just doesn’t work and you have to try something else. Individual rifles are a just that, individuals, and sometimes you’ll get lucky with a “recipe load” that performs well in a variety of rifles (Dan Newberry’s Optimal Charge Weight load workup method tries to identify those universally good loads). But sometimes you won’t get lucky, and nothing you have on hand will shoot worth a darn, and the only thing left to do is change around components until you find something that works (I recall some famous gun rag writer having to resort to 7mm bullets swaged down to 270 bore for one of his custom 270 Winchester rifles to get it to shoot worth a darn).
Comments are open, what’s the darndest accuracy story you’ve got?