The 6mm GT (aka 6GT) cartridge was conceived as a “bigger Dasher” for PRS and NRL competition. The 6mm GT’s creators wanted 6mm Dasher accuracy and moderate recoil delivered via a cartridge with a slightly longer case body for better mag-feeding, longer neck for seating flexibility, and more moderate pressures. So far the 6GT has performed very well in PRS competition. Today’s story is a bit different — this is about an experiment — running a 6mm GT in an F-TR type rifle. Understand that, under current NRA rules, you may only shoot .223 Rem (5.56×45) or .308 Win (7.62×51), in official, sanctioned F-TR competition, but the 6GT is fine for F-Open. Mike McCasland wanted to see the potential of the cartridge for long-range target shooting, so he put a 6mm GT-chambered Bartlein barrel on a nice custom rifle with McMillan XIT stock and Kelbly F-Class Panda action. The results were impressive.
6mm GT — New Cartridge with Multi-Discipline Potential
Story by Mike McCasland, Texas Precision
The 6mm GT began garnering attention within PRS circles in early 2019. It promised to shoot 105-110gr 6mm bullets at 2950-3000 FPS, yet not suffer from mag-feed issues sometimes found with 6mmBR variants such as the 6 Dasher, 6BRX, and 6BRA. Moreover, since it burned less powder, the 6mm GT promised increased barrel life compared to the 6mm Creedmoor or 6XC. The 6mm GT case size should still work with the accurate powders in the Varget burn-range. I found the 6GT also worked great with H4350.
As someone who aspired to building a repeater and jumping into the PRS game, and had a spare F-TR rifle sitting around, I thought it would be fun to build up a 6mm GT to see if there was any merit to the hype. My smith, Wes Ripley of RIP Precision in Texas, builds a lot of PRS rigs, and already had the reamer on hand (a 0.120″ freebore variant).
Whidden Gunworks had some 6mm GT FL bushing die kits in stock, so I figured why not see what all the fuss was about? At the very least I could play around with the 6mm GT in F-Open Class at local club matches to see how it compared to the 6BRA, 6 Dasher, and other popular 6mm cartridges.
How the Project Got Started with Backup F-TR Rig
My 6mm GT build really started as a project spawned purely from COVID-19 Isolation boredom. This rifle primarily serves as a backup F-TR gun, and it had been relegated to performing some load development on .308 barrels, so I could spin new ones on my main match rifle. The only problem was, I had run out of .308 barrels that needed load development. So, I basically had an ideal test platform just collecting dust in the safe. All I needed was a 6mm GT-chambered barrel, since (like the 6mmBR) the 6mm GT works in a short action with a .308 Win-sized bolt-face.
6mm GT Rifle Specifications:
Action: Kelbly Panda F-Class SA RB/RP
Stock: McMillan XIT with RAD 2A
Barrel: 30″ 5R Bartlein 1:7.5″-Twist, HV Contour
Scope: Vortex Golden Eagle 15-60x52mm
Trigger: Jewell Benchrest, about 2 ounces
Bipod: Phoenix Precision
About the 6mm GT Cartridge
BRASS — The first thing you’ll find is cartridge brass choices for the 6mmGT are rather limited currently. At present, the only commercial options are Hornady and Alpha Munitions. For the die-hard Lapua fans, you can technically make 6mm GT brass from 6.5×47 Lapua, however that process is very labor-intensive.
I have used both Hornady and Alpha brass in this rifle and haven’t noticed much difference between the two. I will say that my batch of Alpha brass was slightly softer than Alpha brass I’ve used in other calibers; you could feel a difference when neck turning cases. I’m unsure if that’s a batch issue, or something specific to their 6mm GT brass as a whole. As far as performance, there was little discernable difference. Oddly enough, the Hornady brass seemed to have slightly less case capacity than the Alpha; with most other cartridges it’s the other way around.
POWDERS — The 6mm GT was designed with Hodgdon Varget in mind, and that popular powder works exceedingly well in this platform. That said, the 6mm GT can work with a wide variety of powders, some yielding better performance than Varget.
I’ve tried a multitude of powders during my initial 6mm GT load development: Varget, Shooters World Precision, RL16, VV N140, H4350, and RL-15 to name a few. In my barrel, Hodgdon H4350 seems to deliver the best velocity/accuracy combination. SD and ES also seemed to be the lowest with H4350.
Load Development for the 6mm GT — Many Powders Tested
BULLETS — The most common 0.120″ freebore chamber allows for the majority of high-BC 6mm projectiles found in both F-Class and PRS. I had good luck with the pointed 107gr Sierra Match Kings (SMK), as well as the 110gr Hornady A-Tips in my rifle. For those looking to run the heavier 112-115 grain 6mm offerings, I believe GAP designed a 0.160″ freebore reamer that gets those bullets out of the neck/shoulder junction. Shown below is the 0.120″ freebore JGS reamer print:
SUMMARY — Good Cartridge with Much Potential
Generally speaking, I think the 6mm GT is a good little round. Some may not subscribe to this theory, but I believe some cartridges are inherently easier to tune than others. I’m not sure the 6mm GT is as easy-to-tune as a 6mmBR, 6 Dasher, or 6 BRA, but I don’t think it lags that far behind.
With relatively little trouble, I was able to find loads with both Varget and H4350 that would consistently shoot very well — 0.2 to 0.3 MOA. Moreover, I found the 6GT cartridge lives up to the velocity claims made by G.A. Precision. I was easily able to push the 110gr A-Tips to 2950 FPS, and the 107gr SMKs to low 3000 FPS range without any pressure signs, or unnecessary wear and tear on the brass.
As a fun test, I ran my 6mm GT rifle in a local 1000-yard F-Class match with the 110gr A-Tips, just to see just how well they would perform. Although wind conditions of the day and some E-Target issues prevented my 6mm GT rig from getting the better of the larger 7mm and .30-Cal rifles, the 6mm GT proved itself an accurate little round at distance. Here is a 1000-yard ShotMarker target:
After putting several hundred rounds through my 6mm GT rifle, I anticipate building another 6GT on a repeater action to give PRS a try. I think if you are looking for a dual-purpose rifle that can run tactical matches (with 100% feeding reliability), and can also be used for mid-range, F-Open Class competition, the 6mm GT would be a very good option.
About the author, Mike McCasland:
Mike McCasland is an avid shooter who competes regularly in F-Class matches. Based in Texas, Mike is the creator of the Texas Precision YouTube Channel. There you’ll find many videos covering reloading, gun projects, and marksmanship. Mike has done some notable product reviews including a comparison test of Micrometer Competition Seating Dies. To access Mike’s YouTube Channel, CLICK HERE.
Brownells is a well-known retailer of guns, gun parts, tools, accessories, ammo, and pretty much everything gun related. What you may not know is that Brownells has a very active video production department that releases new “how-to” and product information videos every week. These videos offer helpful advice on gun cleaning/maintenance, reloading, as well as selecting/assembling components for various kinds of rifles. And every week Brownells serves up a new products video. There now over 1000 videos on the Brownells YouTube Channel, this really is a remarkable resource.
Here are six of our favorite recent videos from Brownells. AR owners will find some good advice on spare parts, new reloaders can learn how to use the OAL tool, and all gun owners should watch the video on ammunition storage.
Introduction to PRS Competition
In this video, Tom Beckstrand, former Special Forces Sniper Team Leader and Guns & Ammo magazine staffer, looks at the Precision Rifle Series (PRS). Tom covers the types of stages in a typical PRS match using unconventional, real-world shooting rests. He also discusses the equipment you’ll need including bag supports, bipods, tripods, and optics. As most ranges aren’t set up for PRS, Tom offers tips on how to train at your local range.
How to Use Hornady OAL Tool and Hornady Bullet Comparator
Gun Tech Steve Ostrem explains how to properly use Hornady’s Overall Length Gauge to determine length-to-land precisely. The OAL Gauge uses a “Modified Case” that theads onto the tool and holds a bullet. Push on the back of the gauge until you feel the bullet just touch the rifling. (We do this gently at first, tapping the rod a couple time to ensure the bullet is aligned correctly). Once you’ve got the length, then use the tool with a comparator on your calipers to get the lenght-to-lands. NOTE: We recommend taking the measurement 3-4 times in a row to get a reliable number. With a little practice your should be able to get repeatable measurements within .0015″.
New Bog Pod Tripod and Caldwell Electronic Muffs
Brownells staffer Paul Levy showcases the impressive new DeathGrip Tripod from Bog Gear. The DeathGrip’s adjustable jaws clamp firmly to the rifle’s forearm. This is a useful device for both PRS shooters and hunters. The head assembly has 25-deg front/rear tilt and 360-deg swivel. And the jaws’ non-slip, rubberized padding won’t scratch that stock. The legs snap open to three pre-set hard stops, and there’s plenty of length extension. Easily switch between rubber feet and steel spikes without removing a single part from the trippod. This video also features Caldwell’s E-Max™ Pro noise-cancelling electronic muffs. These affordable 23 dB NRR units boast dual microphones and digital volume controls, and two sizes are offered — Youth and Adult.
How to Store Ammunition Safely and Securely
Notably, this is the single most popular Brownells video this year, with 494,000 views since March 2020. Here’s the deal — ammunition WILL keep for a long time if you store it properaly. DO store ammunition in a cool, dry place that doesn’t have wide temperature swings. Temperature cycling will also degrade primers and powder. Put it in airtight ammo cans to keep out the moisture. Tupperware containers will work too. Brownells also recommends putting moisture-absorbing silica packs in your ammo containers. DON’T just keep ammo in factory cardboard factory boxes stacked in the basement, attic, or garage — especially not on the floor! The ammunition boxes will absorb moisture which will degrade primers and powder and corrode the brass cases. Yes, sealed military ammo will usually handle this kind of storage for quite a while, but it’s still not wise.
Must-Have Spare Parts for AR-Platform Rifles
This is one of Brownells most popular recent videos, with 154,000 views in just four months. Two gun technicians answer the question: “What spare parts should I keep on hand for my AR-15?” On the list are: Gas Rings, Buffer Spring, Extractor Spring and Pin. NOTE: You may want to try the one-piece spiral gas ring rather than the standard rings which require alignment. The cotter pin and cam pin can also easily get lost when the Bolt Carrier Group is disassembled for cleaning. On the lower receiver you’ll want spare springs and detents for the pivot/takedown pins. If you’re using lighter-power springs, keep standard-power spares on hand. If your rifle stops working, swap in the factory-spec springs to find out if the problem is the gun or your ammo. Also, if you have upgraded your trigger, always keep the original trigger as a backup.
Cleaning Advice for .22 LR Rimfire Rifles
Gun Techs Steve Ostrem and Caleb Savant debunk some myths about cleaning .22 LR barrels. One myth is that cleaning will harm the accuracy of a .22 LR barrel. Caleb thinks this myth is the result of people cleaning a barrel from the muzzle and damaging the muzzle crown, which CAN diminish accuracy. If it’s done right, cleaning won’t damage the bore. However, you certainly do NOT have to clean your 22 LR’s bore every time you go to the range. But DO clean the action every time you shoot the rifle, especially on a semi-auto. What about shooting a lot of lead bullets? Won’t that lead up the bore? The guys give us the straight skinny on lead fouling, too. When you see your .22 LR rifle’s groups opening up, you may want to consider cleaning.
Above is a 26-year-old hand-loaded .300 Winchester Magnum case that failed to fire. After the misfire, the shooter used an inertial (impact) bullet puller to pull the bullet. In the process the case-neck sheared off.
Here’s a cautionary tale from the Tactical Rifle Shooters Facebook group. This real-world example explains why you should be cautious of old ammunition. Here serious internal corrosion was discovered.
Old Ammunition — Why You Should Be Careful
Commentary byTactical Rifle Shooters
The subject often comes up as to whether it is safe to shoot old ammunition. Historically my answer has always been yes, since over the years I have shot military surplus ammo dating back to World War II (1939-1945) and never had a problem. With over 40 years in competitive shooting, I’ve also had boxes of factory ammo that were 30+ years old and all worked flawlessly.
But I had an interesting experience this week shooting some .300 Winchester Magnum (WinMag) that I had loaded for competition with Reloder 22 back in 1993. I was breaking in a new barrel so just shooting any old ammo that I had. Of the 20 rounds, 15 shot perfectly, three had a fraction of a second hang-fire, and two didn’t shoot at all.
SMART TIP: If you have old ammunition, pull one bullet to see what’s going on inside.
So I pulled the bullets using a hammer-type impact (inertial) bullet puller. What I found was verdigris-like corrosion inside the necks, with one neck completely separating. One reason for this could be that dissimilar metals (copper and brass) can set up a reaction resulting in corrosion. Like I said, this is the first time I’ve seen this, but will definitely be more aware when shooting old hand-loads in the future.
Above is one of the 26-year-old reloaded .300 WinMag cartridges which had failed to fire. To check the internal condition, the bullet was removed using an impact (inertial) bullet puller. Note the verdigris-like corrosion and crack in neck.
Here’s a close-up of the same .300 Winchester Magnum hand-load from 1993 showing serious corrosion inside the neck. (This was a fail-to-fire.) The powder was Alliant Reloder 22. If you have old ammo, it wouldn’t hurt to pull one bullet to see what’s going on inside.
Even with surging firearms sales in 2020, Remington Arms Company (Remington) found itself in financial trouble — with overwhelming obligations to creditors and investors. Accordingly, on July 27, 2020, Remington filed for Chapter 11 Bankruptcy — the second time in recent years.
Remington, based in Madison, North Carolina, filed for Chapter 11 in March 2018. With major loan reorganizations, Remington “emerged nearly two months later, having converted more than $775 million in debt into equity for its lenders.” (Source: Syracuse.com.) However, despite this debt-restructuring, the company has struggled with high interest costs and litigation related to the 2012 Sandy Hook Elementary School shooting. The perpetrator had a Bushmaster XM15-E2S rifle sold by Remington.
This time, there are more challenges — and it’s unclear how the company’s operations will fare in the months and years ahead. According to the Wall Street Journal, the debt-burdened firearms maker will seek buyers for its assets:
Remington Arms Declares Bankruptcy Despite Surging Gun Demand
Firearms maker Remington Arms Co. filed for bankruptcy protection for the second time since 2018, weighed down by more debt than it can repay even as fearful Americans buy more guns than ever.
Remington … sought chapter 11 protection and will try to sell its business at a time when civil unrest and worries about personal safety have driven firearm sales to record highs.
The chapter 11 petition in the U.S. Bankruptcy Court in Decatur, Alabama, marks Remington’s second restructuring since 2018, when it filed for chapter 11 and transferred ownership to investors including Franklin Resources Inc. and JPMorgan Chase & Co.
Remington has been searching for potential buyers and was in talks to sell itself out of bankruptcy to the Navajo Nation before negotiations collapsed in recent weeks, leaving the company without a lead bidder, or stalking horse, in place.
The manufacturer’s firearms and ammunition businesses could be sold off separately, according to a person familiar with the matter.
Remington Has a Storied History
Founded in 1816 by Eliphalet Remington in New York, Remington is the oldest continuously-operating gun manufacturer in the United States. Even with its present difficulties, Remington still sells more sporting rifles and shotguns than any other American company. Remington has developed more cartridges than any other U.S. company. And it is the only American company that sells firearms AND ammunition under its own name.
In June 2020, Hornady introduced the 6mm ARC, a new SAAMI cartridge optimized for AR-platform rifles*. The new 6mm ARC is basically a 6.5 Grendel necked down to 6mm, with the shoulder moved back around .030″. That pushed-back shoulder does reduce case capacity (and velocity), but we assume Hornady did that to create a shorter, proprietary chamber so people could not simply neck-down Lapua 6.5 Grendel brass, as has been done for years with Robert Whitley’s outstanding 6mm AR wildcat.
What Is the 6mm ARC Cartridge? The 6mm ARC cartridge is a new SAAMI-spec cartridge based on the 6.5 Grendel case necked down for 6mm bullets, with the shoulder moved back 0.030. Yes it is designed to run in AR15-platform rifles. You’ll need a new barrel, bolt, and mags. If you already have an AR chambered in 6.5 Grendel, the ONLY thing you need to change is the barrel. Everything else — bolt, magazines, gas system – is compatible with 6mm ARC.
▶ Official SAAMI Cartridge (not wildcat)
▶ Fits standard AR15-platform rifles
▶ Fits Short/Mini action bolt rifles
▶ Efficient short, fat case design
▶ 30-degree case shoulder
What Do I Need To Shoot the 6mm ARC?
Faxon and Ballistic Advantage are already producing barrels, with more manufacturers sure to follow. All the other required components are already on the market for 6.5 Grendel rifles. Aero Precision already offers complete 6mm ARC uppers.
If you’re converting a standard 5.56×45 mm (.223 Rem) AR15 upper to shoot 6mm ARC, you’ll need a 6mm barrel, a Type II 6.5 Grendel bolt carrier group, and new magazines. Some folks have suggested standard AR mags will work, but trust us, you want the magazines that have been designed for 6.5 Grendel. All the hardware you need is currently available at Brownells. And Brownells also sells complete Aero Precision 6mm ARC Uppers, starting at $749.99.
* While 6-6.5 Grendel shooters are known to run stout pressures, the new 6mm ARC cartridge has a relatively moderate Maximum Average Pressure (MAP) rating of 52,000 psi according to the official SAAMI specifications. For a variety of reasons, is wise to keep pressures in a semi-auto rifle moderate. Don’t chase the velocities you might get in a bolt-action gun.
Do you own an M1 Garand, or have you always wanted to acquire one of these legendary semi-auto battle rifles? Well then here is a valuable new resource: The Essential M1 Garand: A Practical and Historical Guide for Shooters and Collectors. This new book by Jim Thompson covers the history of the M1 Garand, and offers practical advice for Garand owners, along with complete parts lists. The book includes annotated military and National Match manuals, a troubleshooting chart, and a section on hand-loading for the Garand. The final Section addresses common questions about the rifle and offers detailed instructions for maintaining this wartime classic. First published in February, 2020, The Essential M1 Garand is available in Print Paperback and Kindle eBook versions. View Table of Contents.
Recommended M1 Garand Manual
Along with The Essential M1 Garand book by Jim Thompson, there are many other good M1 Garand print resources. Among the many M1 Garand manuals available, we recommend the CMP’s U.S. Rifle, Caliber .30, M1: ‘Read This First’ Manual. This booklet covers take-down, reassembly, cleaning, lubrication, and operation. The manual comes with CMP rifles or can be purchased for $3.25 from the CMP eStore. The CMP also offers many other M1 Garand print resources including:
We’re saddened to announce that noted gunsmith Donald “Stick” Starks passed away last Wednesday. He succumbed to COPD, a disease he’d struggled with for many years. Stick Starks was respected as a knowledgeable gunsmith who built very successful competition rifles, and help popularize many innovative smithing techniques. As proprietor of S&S Precision Rifle in Texas, Stick built great rifles, and helped many folks get their start in competitive rifle shooting. In this Forum Thread, many folks recounted memories of Stick and expressed their sadness at his passing…
“Stick was a great friend and gunsmith. He will be missed.” — Chris Covell
Online Memorial for Donald “Stick” Starks
There will be an online memorial service for Stick Starks on Wednesday, July 15, 2020. This will work via the Zoom video meeting service. This may require you to install some software.
This video shows Stick Starks at his very best, building a rifle with great attention to detail. He did superb chambering and metal work and his bedding jobs were as good as it gets.
Remembering Donald “Stick” Starks…
Eric Kennard posted: “I learned my good friend Don “Stick” Starks died … after a several year battle with COPD. Stick was an amazing and innovative gunsmith. He was a Master Machinist who built engines for dragsters and race boats in his past years. Stick was ornery as all get out. I will truly miss him. He built all of Kenny Adams’ rifles that led Kenny to becoming the 2013 World F-Class Champion. God Speed Stick.”
Forum member Thud added: “My best recollections of Stick is his helping both new and seasoned shooters. They would see him at the range or a match and make a bee line to talk to him. He would listen to their problems or ideas and comment on them. There were customers that would call several times a day just to talk, He always made a few minutes available to them so they flounder. For anyone who had a problem with their rifle — he was always will to help both at the range or in the shop. He was a easy-going guy yet a serious guy who would help anyone if you needed it.”
Forum member Bill (Boiler_House 7) praised Starks’ skills: “Don was such a nice guy and a super good friend. Some may not know this but he was a super talented automotive machinist back in the day as well. He turned out a lot of quality work on race motors at ABC performance in Odessa, Texas. Don is going to be missed by a lot of people he influenced with his knowledge through the years. RIP my friend.”
“Stick was the one who shoved me off the bank into the deep water of accurate rifles, and competitive shooting. The stainless steel Stiller Viper and red Robertson-stocked gun he built [for me] is truly a prized possession. I am really sad to see him go. May his breathing be easy now.” — D. Martin
We have always liked Tikka actions, and now there is a great re-barreling option for Tikka T3 owners. Criterion Barrels Inc. (CBI), makers of “pre-fit” barrels for Savage, Remington, and Rem-clone actions, also produces Tikka pre-fits. These pre-chambered barrels for Tikka T3 actions will be headspaced with a barrel nut, just like a Savage.
Click image for full-screen version
Criterion’s Tikka T3 pre-fit barrels are currently sold through Solid Accuracy, a respected Texas-based outfit that sells high-end scopes, stocks, barrels and other rifle components. Solid Accuracy states: “Each Solid Accuracy/Criterion pre-fit barrel features a hand-lapped bore and meets extreme quality control standards. Utilizing a proven barrel nut design, these barrels can be swapped in just a few minutes using only a barrel nut wrench and the appropriate headspace gauge set. Solid Accuracy offers finished lengths up to 30″ with multiple contour options.”
These Tikka pre-fits were introduced in 2017, and the accuracy results were impressive. Solid Accuracy’s initial test rifle featured a Tikka T3 action mounted in a KRG X-Ray chassis, with Criterion barrel chambered in 6.5 Creedmoor. The group below was shot with a stout load of H4350 and Sierra 140 grain MatchKings seated .009″ in the lands.
Criterion is proud of how well the Tikka pre-fit project turned out. These barrels work great in the Tikka platform. One of Criterion’s staffers was so impressed with the initial test results that he is built his own Tikka T3 rifle, with a Criterion pre-fit of course…
Our friend Gavin Gear has just released an excellent video showing how to make a threaded Modified Case for use with the Hornady Lock-N-Load Overall Length Gauge. You can watch Gavin make a Modified Case start to finish in the video below:
Video Shows How to Drill and Tap Modified Case
Gavin has some clever tricks. First he uses a sizing die to hold the cartridge case during the threading process. Second he uses two drill bits in sequence — a smaller bit to ream out the primer pocket, and then a larger “M” bit to increase the hole diameter before threading the brass. Finally he leaves the threading tap IN the brass, locks the tailstock, and then “gently pulls on the quill” to remove the brass from the die held in his lathe (See 5:46 timemark).
Get the Correct 5/16″-36 RH Tap
Unfortunately, Hornady has selected an uncommon thread type for OAL Gauges. You probably won’t be able to buy the correct 5/16″ – 36 RH HSS Tap at your local hardware store. However you CAN order this special tap from Amazon for $9.99.
Modified Case Q & A — TECH TIPS
Why do I need a Modified Case?
Every serious reloader should have a Modified Case for each cartridge type they shoot. The reason is that this allows you to get very precise measurements of the length-to-lands in your chamber. When used with the Hornady OAL Gauge, with some practice, you should be able to get repeatable length-to-lands measurements within about 0.015″. We generally do 4-5 measurements with the OAL Gauge and usually 3 or 4 will be “on the money”. NOTE: We recommend a gentle, easy pressure on the plastic pusher rod. Don’t push too hard or you will jam the bullet hard into the lands, which produces inconsistent results.
Can’t I Just Buy a Modified Case?
Hornady makes a variety of Modified Cases sold on Amazon and through retailers such as Midsouth. While Hornady makes modified cases for many standard cartridges, if you shoot a wildcat such as the 6mm Dasher or .284 Shehane, you’ll need to create a custom modified case. And even if you shoot a standard cartridge such as the .308 Win, you can get more consistent measurements with a custom Modified Case.
If you do decide to make your own modified case, you’ll want to start with a case that’s been fired in your rifle. That way you get the best fit to YOUR chamber. Also, you won’t need to expand the neck to provide bullet clearance. Then you need to drill out the primer pocket and tap the base of the case to match the threads on the Hornady OAL Gauge tool. Make at least two modified cases, as you’ll probably misplace one at some point.
Erik Cortina Makes a Modified Case
If you want to learn more about making Modified Cases, top F-Class shooter Erik Cortina has also created a helpful video showing the process he uses to make modified cases. In Erik’s video, he shows how he taps a case to work with the Hornady Lock-N-Load Overall Length Gauge (formerly the Stoney Point Tool). Erik also explains how to get the best results when using the Modified Case to measure length to lands.
MORE INFORMATION: Want to learn more? We published a much longer story in which Erik explains in greater detail how to made the Modified Case. That article illustrates the 5/16″ – 36 RH HSS Tap required and shows how to set up the lathe to drill and tap your case. If you are serious about making your own Modified Cases, you should Read the Full Article.
Want to see the details?CLICK HERE to view full-screen photo.
Check out those five targets. The Aggregate (average) of all five targets is a tiny 0.0840 inches! These were shot by Gary Ocock at 100 yards in a California benchrest match on August 6, 2017. Though Gary’s 0.0840 Agg beats existing records, this was not a “sanctioned” match, so Gary’s killer Agg will NOT be submitted for IBS or NBRSA records. So, sadly, the Agg won’t appear in the record books, but this remains a spectacular, verified feat of rifle accuracy, accomplished in competition.
Gary’s red railgun is arguably the Most Accurate Gun Ever Built. As far as we can determine, no one has ever shot a smaller 5-target Agg anywhere, at any time. FYI, the NBRSA Unlimited Class 5×5 Aggregate World Record is 0.1242″ shot by Jerry Lahr in 2012. Gary’s 0.0840″ Agg is much smaller.
The Unlimited Benchrest Record That Will Never Be (Official)
Report by Boyd Allen
Gary Ocock’s stunning unlimited Aggregate is beyond amazing. That’s an average of five, 5-shot groups of .0840. Shot under sanctioned match rules, but at an unsanctioned 100-yard fun match, this Aggregate is well under the current 100-yard official records of the IBS (.1386), and the NBRSA (.1242). The fourth of the five groups measured a minuscule .018, less than half the size of the existing NBRSA Unlimited record of .049 (also shot by Gary). Check it out:
When the top 15 shooters all post teen Aggs, conditions must be pretty favorable. However there were some light switchy winds — Gary said that he shot better in the left to right condition.
GUN SPECIFICATIONS
Ocock’s red Jay Young Unlimited Railgun features one major difference from Young’s typical Railgun designs. The bottom of the barrel block is integral with the top (moving part), of the gun. The barrel is Ocock’s usual 1:13.5″-twist Krieger chambered for the 6 PPC. The BAT Neuvo action* is unusual in that its lugs are horizontal at lock-up instead of the usual vertical. With horizontal lugs, both lugs maintain contact with their abutments when the action is cocked. In the more normal configuration when cocked the top lug is forced off of its seat by a combination of the angle of the trigger cocking piece interface, the pressure of the striker spring, and bolt clearance at the rear of the action.
LOAD SPECIFICATIONS
Gary shot this remarkable Agg with well-used brass, Vihtavuori N133 powder, and self-made 66gr BT bullets** seated at “jam”. This amazing Agg was shot on the second day of a 2-day Unlimited Benchrest match. On Day 1 Gary had experimented with various loads using both surplus IMR 8208 and Vihtavuori N133, but was not satisfied with the results. For his first group on Day 2, Gary tried a light load of N133. After seeing the result, however, he decided to go to the other extreme — a super stout N133 load — with the same powder. As you can see, Gary’s willingness to experiment paid off.
Notably, Gary used light neck tension. Ocock found that for these bullets and this barrel, light neck tension worked best (contrary to “normal” N133 benchrest practice). Ocock used a bushing that only produces .001″ difference between the diameters of sized and loaded case necks.
This video shows a line-up of Rail-Guns. One of Gary Ocock’s Rails appears at the 0:35 time-mark.
Comment on Ocock’s Achievement
Congratulations to Gary Ocock for superb shooting (and smart loading). Even though the match was not sanctioned (so the Agg will never be a record), Ocock has raised the bar very high, and given us a new standard of ultimate accuracy.
Though this 0.0840 Aggregate and 0.018 group will never go into the record group, they are still noteworthy. There’s virtually no doubt that they would have survived inspection by any record committee. Except for the lack of fixed backers, an IBS requirement (for detecting cross-fires), all other conditions were met for an officially-sanctioned match.
Ocock Did Set Single-Group IBS World Record with Red Railgun
Photo credit: Ben Zentner
Here is Gary with his Red Railgun at a Visalia event in October 2017. Ocock let the event’s youngest competitor, 12-year-old Gavin Lichtenwalter, shoot Gary’s new Railgun for the last three matches on Sunday afternoon. The day before, 10/21/17, Gary shot an IBS Heavy Benchrest World Record putting five shots in just 0.045 inches, as certified by the IBS record committee. Here is that group, as first measured at the range at 0.039 inches.
*The new BAT Neuvo actions are the result of a collaboration between Dwight Scott, and Bruce Thom, featuring Dwight’s ideas and BAT’s proven manufacturing expertise.
** Ocock shot his own, boat-tail match bullets, made with George Ulrich-crafted dies using Hood cores. Although he said that it had been a while since he had weighed any, his best guess was that they weigh something around 66.5 grains.
As someone who aspired to building a repeater and jumping into the PRS game, and had a spare F-TR rifle sitting around, I thought it would be fun to build up a 6mm GT to see if there was any merit to the hype. My smith, Wes Ripley of RIP Precision in Texas, builds a lot of PRS rigs, and already had the reamer on hand (a 0.120″ freebore variant).
BRASS — The first thing you’ll find is cartridge brass choices for the 6mmGT are rather limited currently. At present, the only commercial options are Hornady and Alpha Munitions. For the die-hard Lapua fans, you can technically make 6mm GT brass from 6.5×47 Lapua, however that process is very labor-intensive. 
SUMMARY — Good Cartridge with Much Potential
Online Memorial for Donald “Stick” Starks
Check out those five targets. The Aggregate (average) of all five targets is a tiny 0.0840 inches! These were shot by Gary Ocock at 100 yards in a California benchrest match on August 6, 2017. Though Gary’s 0.0840 Agg beats existing records, this was not a “sanctioned” match, so Gary’s killer Agg will NOT be submitted for IBS or NBRSA records. So, sadly, the Agg won’t appear in the record books, but this remains a spectacular, verified feat of rifle accuracy, accomplished in competition.
