Editor: Many new barrels will deliver higher velocities with the same load after 100-150 rounds through the bore. The exact reasons for this speed-up are not 100% certain, and velocity increases (if any) will vary from one barrel to the next. But this “speeding up” phenomenon is common, so be prepared if this happens with your next barrel. If you do experience a significant velocity increase you should probably re-tune your load AFTER the velocity stabilizes at the higher level.
From the Sierra Bullets Blog Article by Mark Walker, Sierra New Product Development Director
In a previous post, I discussed a couple of methods to tune a load to your barrel to help achieve the best accuracy possible. People most often work on load tuning if they get a new rifle or have a different barrel installed. In both instances, the barrel is new and has not been fired very much. According to most competitive shooters, this is the most accurate your barrel will ever be, so getting it tuned and shooting accurately is a priority.
The Speed Up Phenomenon After 100-150 Rounds
Even though after you work up a load and your new barrel is shooting great, a lot of shooters notice that at around 100 to 150 rounds their rifle may stop shooting as accurately. I had this happen to a rifle and I was confused as to why something that worked so well to begin with would all of a sudden quit shooting. I decided to break out the chronograph to do another load work up to see what was going on. To my surprise, the velocity had increased around 80 fps over the original velocity! After performing another ladder test and adjusting the seating depth, the rifle was once again shooting well.
There are several thoughts on why this may happen, however, you can rest assured that it does happen. One thought is that as the barrel breaks in, the tooling marks in the throat of the chamber smooth out and allow less resistance to the bullet as it exits the bore thereby increasing speed. Another idea is that the throat area starts to get a little rough which in turn causes more resistance which increases pressure and therefore more velocity. I’m sure there are some out there who have a better understanding as to why this happens, but it can definitely affect the accuracy of your rifle. So be aware and never be afraid to rework a load to keep your rifle in tune.
Experts Confirm That Barrel Speed-Up Is Common Two respected shooters have observed an increase in velocity with new barrels, typically after 100 rounds. Gunsmith and Hall-of-Fame benchrest shooter Thomas “Speedy” Gonzalez has documented barrel speed-up with testing. Moreover, Speedy’s bore-scope barrel inspections revealed a smoothing of the barrel lands. Jim See, a top PRS competitor, has encountered barrel speed-up many times. Accordingly, he re-tunes his load at 150 rounds.
“Alex Lipworth and I documented this phenomenon about four years ago and I have told all my customers about this. My son Mikee would shoot 100 rounds through all new barrels we planned on shooting before we would begin to do load development. We had a shooting snail that caught all the bullets set up in front of an indoor bench. We called it a wear-in process because upon careful examination of the bore when the ‘Speed Up’ takes place the cut-rifled bore resembles that more of a button-rifled barrels with the lands taking on more the softer look of a buttoned bore.” — Speedy Gonzalez
“Seen it [barrel velocity increase] too many times to count. All my match barrels get a ‘generic round’ loaded for them, which has worked well in barrels historically. After I hit 150 rounds I fine-tune the load and never look back, until the tube starts to slow down at it’s life end.” — Jim See
Do you have some ammo that got loaded incorrectly, perhaps with the wrong powder? Then you’ll want to disassemble the ammo for safety’s sake. You can use an impact puller to do this task, but if you have more than a dozen rounds or so, you may prefer to use a collet-style bullet puller. These work very quickly and positively, making quick work of big jobs. The efficiency of the collet-style puller is worth the investment if you frequently disassemble ammo. These devices retail for under $35.00 (collets sold separately). Normally, you’ll need a specific collet for each bullet diameter. But collets are not that costly, so this isn’t a big deal, particularly if you only load a few calibers, such as .223, 6mm, and .308.
Hornady and RCBS use different mechanisms to tighten the collet around the bullet. On the red lever Hornady Cam-Lock Bullet Puller, a lever-arm on the top of the bullet puller serves to tighten the collet around the bullet. Simply rotate the lever from the vertical to the horizontal position to grab the bullet. Lower the ram to remove the case. The bullet will drop out when you return the lever arm to the vertical position. This is demonstrated in the video below:
Hornady Cam-Lock Bullet Puller Demonstrated
Collet bullet-pullers resemble a loading die with a lever or handle on the top. They screw into a standard reloading press. Hornady and RCBS both make collet-style bullet pullers. They use the same basic principle — the device tightens a collet around the bullet, and then the bullet is separated from the case by lowering the press ram. NOTE: Collet pullers may leave small marks on your bullets, unlike impact (kinetic) pullers.*
Like the Hornady tool, the RCBS Bullet Puller employs a collet to grab the bullet. However, the RCBS tool tightens the collet in a different way. The head of the RCBS tool is threaded internally. By rotating the lever arm clockwise in a horizontal circle you squeeze the collet around the bullet. To remove the bullet, after lowering the press ram, simply spin the lever arm back in the opposite direction. The use of the RCBS tool is demonstrated in these two videos:
RCBS Collet Bullet Puller Demonstrated:
WARNING: When removing bullets from loaded cartridges, always make sure there are no obstructions or debris in your shell-holder or under the loaded round. NEVER engage a primer seating accessory on your press when working with loaded rounds. You can cause a round to discharge by contacting the primer! Also, we recommend you keep your head and torso away from the bullet puller tool at all times.
*By contrast, impact pullers rarely mark bullets, particularly if you put a little bit of foam or paper wadding in the closed end of your impact puller. When dismantling loaded rounds, powder kernels can get trapped in the wadding, so you should remove and replace the wadding before changing to cartridges loaded with a different powder type (assuming you intend to save the powder).
It’s October, the fall season, and that means rainy, wet weather is on the way in many areas of the country. With rain comes increased moisture in the air, i.e. increased humidity. And that, in turn, can affect how your powders perform by altering their burn rates.
Most shooters realize that significant changes in temperature will alter how powders perform. That’s why you want to keep your loaded ammo out of the hot sun, and keep rounds out of a hot chamber until you’re ready to fire. But there are other factors to be considered — HUMIDITY for one. This article explains why and how humidity can affect powder burn rates and performance.
We’ve all heard the old adage: “Keep your powder dry”. Well, tests by Norma have demonstrated that even normal environmental differences in humidity can affect the way powders burn, at least over the long term. In the Norma Reloading Manual, Sven-Eric Johansson, head of ballistics at Nexplo/Bofors, presents a very important discussion of water vapor absorption by powder. Johansson demonstrates that the same powder will burn at different rates depending on water content.
Powders Leave the Factory with 0.5 to 1.0% Water Content
Johansson explains that, as manufactured, most powders contain 0.5 to 1% of water by weight. (The relative humidity is “equilibrated” at 40-50% during the manufacturing process to maintain this 0.5-1% moisture content). Importantly, Johansson notes that powder exposed to moist air for a long time will absorb water, causing it to burn at a slower rate. On the other hand, long-term storage in a very dry environment reduces powder moisture content, so the powder burns at a faster rate. In addition, Johansson found that single-base powders are MORE sensitive to relative humidity than are double-base powders (which contain nitroglycerine).
Tests Show Burn Rates Vary with Water Content
In his review of the Norma Manual, Fred Barker notes: “Johansson gives twelve (eye-opening) plots of the velocities and pressures obtained on firing several popular cartridges with dehydrated, normal and hydrated Norma powders (from #200 to MRP). He also gives results on loaded .30-06 and .38 Special cartridges stored for 663 to 683 days in relative humidities of 20% and 86%. So Johansson’s advice is to keep powders tightly capped in their factory containers, and to minimize their exposure to dry or humid air.”
Confirming Johansson’s findings that storage conditions can alter burn rates, Barker observes: “I have about 10 pounds of WWII 4831 powder that has been stored in dry (about 20% RH) Colorado air for more than 60 years. It now burns about like IMR 3031.”
What does this teach us? First, all powders start out with a small, but chemically important, amount of water content. Second, a powder’s water content can change over time, depending on where and how the powder is stored. Third, the water content of your powder DOES make a difference in how it burns, particularly for single-base powders. For example, over a period of time, a powder used (and then recapped) in the hot, dry Southwest will probably behave differently than the same powder used in the humid Southeast.
Reloaders are advised to keep these things in mind. If you want to maintain your powders’ “as manufactured” burn rate, it is wise to head Johannson’s recommendation to keep your powders tightly capped when you’re not actually dispensing charges and avoid exposing your powder to very dry or very humid conditions.
Real-World Example — “Dry” H4831sc Runs Hotter
Robert Whitley agrees that the burn rate of the powder varies with the humidity it absorbs. Robert writes: “I had an 8-lb. jug of H4831SC I kept in my detached garage (it can be humid there). 43.5-44.0 gr of this was superbly accurate with the 115 Bergers out of my 6mm Super X. I got tired of bringing it in and out of the garage to my house for reloading so I brought and kept the jug in my reloading room (a dehumidified room in my house) and after a few weeks I loaded up 43.5 gr, went to a match and it shot awful. I could not figure out what was going on until I put that load back over the chronograph and figured out it was going a good bit faster than before and the load was out of the “sweet spot” (42.5 – 43.0 gr was the max I could load and keep it accurate when it was stored in less humid air). I put the jug back in the garage for a few weeks and I now am back to loading 43.5 – 44.0 gr and it shoots great again. I have seen this with other powders too.”
If you have two jugs of the same powder, one kept in a room in your house and one somewhere else where it is drier or more humid, don’t expect the two jugs of the same lot of powder to chrono the same with the same charge weights unless and until they are both stored long enough in the same place to equalize again.
Even with high-quality brass from Lapua, Peterson, Norma, Alpha and RWS, occasionally you may find one or two cases per box which have a small flake or obstruction in the flash-hole. This will appear like a thin crescent on one side of the flash hole (see photo). You should inspect ALL new brass before loading to identify any pieces with a partially-obstructed flash hole. It’s a good idea to remove any flake or thin crescent left as an artifact of the flash-hole forming process. Because the flash-hole itself is normally centered and of the correct diameter, it is not necessary to ream the flash-hole to a larger diameter. All you really need to do is remove the small obstruction(s). This can be done quickly with inexpensive tools.
Use a Small Pin Vise to Remove Flash-Hole Obstructions
Folks have asked if there is a tool that can remove obstructions from a Lapua small, BR-sized flash hole without opening the hole size. The Lapua PPC/BR flash hole is spec’d at 1.5mm, which works out to 0.059055″. Most of the PPC/BR flash-hole uniforming tools on the market use a 1/16″ bit which is nominally 0.0625″, but these often run oversize — up to 0.066″.
If you want to just clear out any obstructions in the flash hole, without increasing the flash hole diameter, you can use an inexpensive “pin vise” with an appropriate drill bit. For $5.39, Amazon sells a 10-piece set of cobalt steel 1.5mm drill bits that match the Lapua flash hole exactly. Other vendors such as Ace Hardware offer a #53 pin vise drill bit that measures .0595″ or .060″ (depending or source). An 0.0595″ (1.51 mm) bit is close enough. You can find pin vises and these small-diameter drill bits at hobby stores.
For quite some time, Sinclair Int’l has sold a similar device for small (PPC and BR-size) flash holes. Like the 749008617 unit for large flash holes, the 749005418 Reamer for small flash holes works from the outside, so it can index off the primer pocket. It reams to .0625″, and also costs $29.99. The standard dimension for Lapua 220 Russian and 6mmBR flash holes is 1.5mm or .0590″. This tool will permit standard-size decapping rods with .0625″ tips to work without binding. However, note that both Forster and Redding normally supply .057″ decapping pins with their PPC and BR dies. So, it is NOT necessary to ream your Lapua BR/PPC flashholes, unless you prefer to do so for uniformity. It IS, however, a good idea to check BR/PPC flash holes for burrs before loading the first time.
Redding also makes a handy tool that deburs and uniforms small flashholes, but works from the inside of the cases. This Redding tool has a bushing that fits in the case neck for proper alignment.
NOTE: If you purchase the Sinclair Flash Hole Reamer tools, we recommend you mic the cutter tip before you process a bunch of cases. Sometimes a tip comes through that is oversize. This will ream the flash holes larger than you may intend.
With the skyrocketing prices of ammo, more shooters than ever are hand-loading pistol and rifle ammunition. But many novice reloaders tell us that it’s a bit overwhelming in the beginning. Just learning all the technical terms (e.g. ogive, meplat, ballistic coefficient, load density etc.) is difficult, and the task of selecting the right tools and gear can be daunting.
The first thing a new reloader should do is find an experienced reloading mentor. One can learn the basics much more quickly under the guidance of an experienced hand-loader who “knows the ropes”. We also recommend that newbies acquire a good basic reloading handbook — not just a list of load recipes, but a book that explains the processes.
One of the best handbooks available is The ABCs of Reloading (10th Edition, 2021) by Philip Massaro. Released in March 2021, this reference contains 288 pages with hundreds of BW photos. The latest 10th Edition is available from Gun Digest Store for $29.99 (or $29.99 for Printable PDF Digital Book). You can also purchase from Walmart for $19.54 with possible Free Shipping.
Since the first edition was published in the 1970s, the ABCs of Reloading series has taught countless firearms owners safe/reliable methods for creating their own ammunition. ABCs of Reloading provides beginners what they need to know to get started in reloading. From basic topics such as “How does a cartridge work?” and “What components do I need?” to more advanced discussions of cartridge pressure, headspace, and chrono testing, this is a great resource for new handloaders.
In addition, the sections on advanced reloading and new powders make the new edition valuable for experienced handloaders. And long-range shooters will benefit from the sections on making ultra-consistent ammo and fine-tuning for precision accuracy. Massaro’s coverage of new reloading gear and components is another bonus (shown below is the impressive RCBS MatchMaster powder dispenser).
Review from purchaser of “The ABCs of Reloading”, 8th Edition:
“When I first got the itch to load my own ammunition, I was overwhelmed by the amount of information and terminology involved in this fascinating field/hobby. It was very difficult to take all the individual pieces of information that I had and form it into an understandable process. I was snowed in under a blizzard of data that I was piecing together through chat rooms and web sites. Phrases like ‘roll crimp’ and ‘headspace’ came at me in a blizzard. I could look up each phrase, understand each one as a piece, but still the whole picture was fuzzy. In essence, that is what this book will do for you — turn it all into a coherent, linear whole. The writing is very solid and clear, the illustrations are well-done and helpful, and the information is very complete. After reading this book, the entire process made sense to me, and more importantly, I was fully warned about the dos and don’ts of the reloading world. The coverage is very complete. Primers, powders, bullets, and … all necessary tools and accessories are discussed and explained. This is just a great book. It won’t make you an expert … but it will put you on the right road if you wish to become one.” — Mykal Banta
Do you know what the inside of a rifle chamber (and throat zone) really looks like? Do you understand the concept of headspace and why it’s important? If not, you should read the Brownells GunTech article Gauging Success — Minimum Headspace and Maximum COL. This article explains the basics of headspace and shows how to measure headspace (and length to lands) in your barrels with precision. The article also explains how to adjust your full-length sizing dies to “bump the shoulder” as needed.
Why is headspace important? The article explains: “Controlling headspace and setting proper C.O.L. also represent improved safety and reduced cost of handloading. Excessive headspace can cause case head separation and gases in excess of 60,000 PSI escaping from a rifle’s chamber. Too little headspace can result in a chamber forced bullet crimp and a bullet that becomes an obstruction more than a properly secured projectile. Excessive C.O.L. can result in a rifling-bound bullet, a condition that could result in spikes of excessive pressure.” [Editor’s NOTE: It is common for competitive benchrest shooters to seat bullets into the rifling. This can be done safely if you reduce your loads accordingly. With some bullets we often see best accuracy .010″ (or more) into the lands. However, this can generate more pressure than the same bullet seated .010″ away from initial lands contact. As with all reloading, start low and work up gradually.]
How is headspace specified? Most cartridges used within the United States are defined within ANSI/SAAMI Z299.3-4. Brownells explains: “In the case of the .243 Winchester, as an example, there are pressure specifications, cartridge drawings and, as pictured above, chamber drawings. Armed with a chamber drawing, each manufacturer producing a firearm for the .243 Winchester knows the proper standard dimension to cut chambers and set headspace. Notice there are two headspace reference dimensions for the chamber. The upper is a place in the chamber where the shoulder is .400″ in diameter; the “datum” or “basic” line. The lower is the 1.630″~1.640″ minimum – maximum dimension from the breech face (bolt face) to that point in the chamber that measures .400″.”
The actual headspace of any firearm is the distance from the breech face to the point in the chamber that is intended to prevent forward motion of a cartridge.
Finding Cartridge Length to Lands with OAL Gauge
Using a comparator on a set of calipers, you can quickly determine cartridge base-to-ogive length. This is the measurement from the base of the case to the forward-most full diameter section of the bullet, which is for convenience called the ogive. (Technically, the “ogive” is the full curve from bullet tip back to full-diameter ring). Shown here, that ogive is 0.243″ diameter.
The next step is using a modified (threaded) case with a Hornady OAL tool to determine Length-to-Lands (LTL) in your rifle’s chamber. During this measurement process, the modified case, with a bullet in its neck, is inserted in the chamber. Go slow, take your time. Here are 5 tips that will help you get repeatable and reliable LTL measurements:
1. Start with a clean chamber and clean barrel throat.
2. Make sure the modified case is fully screwed down and seated on the OAL Gauge. It can sometimes unscrew a bit during repeated measurements.
3. Insert the modified case slowly and gently, but ensure the shoulder of the modified case is fully seated on the end of the chamber.
4. Push the gray plastic rod GENTLY. It is common for the bullet to be tilted a bit. You want to allow the bullet to self-center in the throat BEFORE you apply much pressure. Then tap a couple times and push until you feel resistance. Do NOT push too hard — that will jam the bullet in the lands.
5. Repeat the measurement at least 3 more times. If you follow our instructions, you should, typically, get a repeatable measurement, within 0.0015″ or so, 3 out of 4 times.
Starline Brass offers a series of videos with helpful reloading tips. Focused primarily on pistol cartridges, these short videos can help anyone get started with metallic cartridge reloading. If you load pistol rounds on a progressive, this video series is particularly helpful. The on-camera host is Hunter Pilant, son of Carroll Pilant of Sierra Bullets.
Preventing Double Charges
Tip: Use a bulky powder that fills your case more than half way with a correct charge. This will overfill the case if it is double-charged, making it very difficult to seat a bullet.
Tumble New Brass Before Loading the First Time
Tip: Tumble new pistol cartridge brass in used media for 30 minutes before loading for the first time. This will add enough graphite (carbon residue) to smooth case entry into dies. You can also lube the case mouths with graphite, or use spray lube.
Powder Through Expander — How to Eliminate Hang-ups
Tip: When loading pistol brass with a progressive press, sometime the powder-through expander is hard to remove, especially with short cases. There are two fixes — first, try deburring the inside of the case mouth on your cases. Second, the radius of the powder through expander plug can be modified to smooth entry and exit (see photo). Starline will do this modification for free.
⏺️ » Over 70 loadbook varieties — great for pistol and hunting loads
Loadbooks pack a ton of valuable load data in a single handy volume. These booklets efficiently summarize data from multiple bullet and powder manufacturers. We have used these Loadbooks for our pistol loading as well as common rifle hunting loads. Right now a wide selection of these loadbooks are in-stock at MidwayUSA, with affordable prices. The 6.5 Creedmoor manual is $9.29, the .45 ACP book is $10.49, the .223 Rem book is $11.49, and the .308 Win book is $12.49.
Chose from over 70 cartridge types, including .380 ACP, 9mm Luger, .357 Magnum, .40 SW/10mm, .45 ACP, .204 Ruger, .223 Rem, 22-250, 6mm Remington, 6.5 Creedmoor, 6.5×55, 7mm-08, .270 Win, .284 Win, .308 Win, .30-06, 300 WinMag, .338 LM, 12ga shotshell and many more. NOTE: On MidwayUSA’s landing page, click “Select Title” then scroll down to choose your preferred cartridge type. You an order multiple loadbook titles by adding to the shopping cart.
NOTE: Good load information is available online from Hodgdon and other powder companies. But it’s handy to have a print book that you can use without Wifi, and make notes about your loads. Sometimes a traditional reference is actually more convenient than the internet.
Do you know how gun primers are made — how the explosive elements are applied into those tiny cups? Find out by watching this video filmed at a Federal ammunition factory. It starts out with empty primer cups loaded, 1000 at a time, into trays using vibration (0:05 time-mark). While much of the process is automated, there is still a significant role played by production workers who apply a green, paste-like charging compound to the inside of hundreds of primer cups.
At the 0:17-second time-mark you can see the factory worker “charging” the primers with the priming compound. After the cups are filled, then the plate of cups “mates up with a plate of anvils” (0:40 time-mark). Then the primers are unloaded from trays and inspected.
Primer “Mysteries and Misconceptions” Article
There is an excellent article about primers on the Shooting Times website. This authoritative Shooting Times article explains the fine points of primer design and construction. The author reveals some little-known facts about primers and corrects common misconceptions. Here are some highlights:
Size Matters
Useful Trivia — even though Small Rifle and Small Pistol primer pockets share the same depth specification, Large Rifle and Large Pistol primers do not. The standard pocket for a Large Pistol primer is somewhat shallower than its Large Rifle counterpart, specifically, 0.008 to 0.009 inch less.
Magnum Primers
There are two ways to make a Magnum primer — either use more of the standard chemical mix to provide a longer-burning flame or change the mix to one with more aggressive burn characteristics. Prior to 1989, CCI used the first option in Magnum Rifle primers. After that, we switched to a mix optimized for spherical propellants that produced a 24% increase in flame temperature and a 16% boost in gas volume.
Foiled Again
Most component primers have a little disk of paper between the anvil and the priming mix. It is called “foil paper” not because it’s made of foil but because it replaces the true metal foil used to seal early percussion caps. The reason this little disk exists is strictly a manufacturing convenience. Wet primer pellets are smaller than the inside diameter of the cup when inserted and must be compacted to achieve their proper diameter and height. Without the foil paper, the wet mix would stick to the compaction pins and jam up the assembly process.
When your cases become hard to extract, or you feel a stiff bolt lift when removing a cartridge, it’s probably time to full-length size your cases, and “bump” the shoulder back. We generally recommend bumping shoulders each time you reload, after the initial fire-forming. Benchrest and F-Class benchrest shooters, running relatively high pressures, typically full-length size every load cycle, bumping the shoulder .001-.003″. High Power shooters with gas guns generally full-length size every time, and may need to bump the shoulders .003″ or more to ensure reliable feeding and extraction.
Use Shims for Precise Control of Shoulder Bump
Some shooters like to set the “default” position for their full-length die to have an “ample” .003″ or .004″ shoulder bump. When they need less bump, a simple way to reduce the amount of shoulder movement is to use precision shims in .001″ (one-thousandth) increments.
Here are reports from Forum members who use the shims:
“Great product. I have my die lock ring(s) adjusted for the shortest headspace length on my multiple chambers 6BRs and 6PPCs. When needing a longer headspace, I just refer to my notes and add the appropriate shim under the lock ring. Keep it simple.” — F.D. Shuster
Mats Johansson writes: “I’ve been using [shims] since Skip Otto (of BR fame) came out with them. I set up my dies with the .006″ shim, giving me the option of bumping the shoulder a bit more when the brass gets old and hardens while still having room to adjust up for zero headspace, should I have missed the original setup by a thou or two. Hunting rounds can easily be bumped an extra .002-.003″ for positive, no-crush feeding. Being a safety-oriented cheapskate, I couldn’t live without them — they let me reload my cases a gazillion times without dangerous web-stretching. Shims are a must-have, as simple as that.” — Mats Johansson
Sinclair Die Shim Kit — Seven Shims for $14.99
Sinclair Int’l (through Brownells) offers a seven-piece set of Sizing Die Shims that let you adjust the height of your die (and thereby the amount of bump and sizing) in precise .001″ increments. Sinclair explains: “Some handloaders will set their die up to achieve maximum sizing and then progressively use Sinclair Die Shims between the lock ring and the press head to move the die away from the shellholder. Doing this allows you to leave the lock ring in the same position. These shims are available in increments of .001″ and work very well.”
Seven Shims from .003″ to .010″
Sinclair’s $14.99 Die Shim Kit (item 22400) includes seven shims in thicknesses of .003, .004, .005, .006, .007, .008, and .010. For ease of use, shim thickness is indicated by the number of notches cut in the outer edge of each shim. Even without looking you can “count” the notches by feel.
Two respected shooters have observed an increase in velocity with new barrels, typically after 100 rounds. Gunsmith and Hall-of-Fame benchrest shooter Thomas “Speedy” Gonzalez has documented barrel speed-up with testing. Moreover, Speedy’s bore-scope barrel inspections revealed a smoothing of the barrel lands. Jim See, a top PRS competitor, has encountered barrel speed-up many times. Accordingly, he re-tunes his load at 150 rounds.
Like the Hornady tool, the 
Tests Show Burn Rates Vary with Water Content
Finding Cartridge Length to Lands with OAL Gauge
