David Tubb’s 37XC
The Quest for the Ko2m rifle cartridge
David Tubb’s 37XC cartridge pictured below is made to work on a 338 Lapua Magnum bolt face. This is it’s strongest selling point. You can upgrade your 1 mile rig to a 2 mile performing cartridge in .375 caliber with a simple change of the barrel. Given the length of David Tubb’s 37XC, this will be a single feed only cartridge.
Left to right: 338 lapua (empty)- 33XC Warner 256gr Flatline – 33XC cartridge head – 37XC Warner 361gr Flatline – 375 Cheytac (empty) Note – the XC case length VS. the 375 Cheytac. Pic. courtesy of Vestals custom rifles. NEXT, 375 Cutting Edge Lazer 400gr.
Watch 37 XC ammo in the making for King of 2 Miles
The quest for the ideal 2-mile rifle cartridge has taken us on numerous forums, phone calls and social groups as well as a trip to Italy, Denmark and France in search of what others are doing to be able to connect with that elusive 2-mile target 48”x60” (120cmx150cm) rectangle (3200meters) – now synonymous with the King of 2 miles competition.
The competition has spread like an Australian wildfire from the US to Europe, Latin America, South Africa, Russia and the list keep growing. Other matches like Conquer the Castle in the US, NRA ELR Nationals in Raton NM, Spearpoint, Ringneck, ELRSO, ELR South East, Long Range Only, World’s longest Shot Challenge and ELR Central have come up with a regular league with many shooters getting a go every month at these distances. There are also some private training facilities especially in the US like Kaian Vista Ranch that hold training with professionals shooters to get you there. The ELR Scene has also developed into ELR heavy and ELR Light class (338Caliber and less like the 33XC for example)
After our trip to the 2 mile facility at Coldbore Range, Denmark, we were even more hooked partly because we saw the potential of a team working well together while acknowledging that we were limited with our 300Norma Mags to about 1700-2000m especially in wet ground which gobbled up our bullets. David Tubb’s 37XC cartridge was an appealing option with a lower barrier entry.
Want to see what the 300 Norma Magnum is capable of? Checkout our 1 mile shooting trip in Sicily.
Interested in experiencing an amazing 5-day long weekend in Sicily, Italy?
Surrounded by beautiful scenery and some of the best long range shooters and kit from all over Europe. In 2022, Fabrizzio Giugga led the way to 2000m with his 300PRC.
Join our event
37XC Wind Drift Chart
Above: Wind drift comparisons for 300Norma vs 37XC vs 41XC vs 416Barrett for 10mph full value wind. Notice, although there is a difference to the larger 416Barrett with a 40inch barrel, the 37XC and 41XC are using a 33-inch barrel here to achieve this performance as well as the same platform. The 300Norma is there to accentuate the difference in level of performance. What the 300Norma is capable of at 1mile, the 37XC will do at 2500m with ease (windage-wise)
We’ve spoken to a few tens of industry leaders to understand what is it that would make an ideal chambering for this purpose. What bullet, cartridge, barrel length, action, scope, mount combination would bring us closer to achieve this? The combinations are increasing.
US Optics Sn9 3.8-22×58 – old school scope with exterior adjustments offering 235MOA plus of elevation adjustment seen mounted on a DTA. We need approximately 180-220 MOA of elevation adjustment depending on atmospherics and 15-25MOA of windage at 2 miles depending on wind speed.
Roberto Buccolo of Windcut bullets from Italy customised this DTA HTI with a 50inch barrel chambered for 460Steyr (more info on .460 STEYR coming soon!)
ELR cartridges: Which one are you eyeing in your sights? 375CT, 460 Steyr, 408 cheytac, 338 LM
It was readily apparent that this quest was largely dictated by how big you want to go, both in terms of expenditure but also in terms of weight and size of your platform. We’ve seen everything from benchrest style rigs to Fclass platforms on steroids to lighter tactical looking rifles.
These are proper 2-mile rigs purpose built to accomplish one thing – Extreme Range performance with a similar price tag
F-Class Rig extravaganza – Italian work of Art by BCM proudly owned by G. Zanoni from Italy.
The quest for the ultimate cartridge is not complete without mentioning the bullets that are available for David Tubb 37XC cartridge. Back when .375 caliber bullets where largely reserved to the 375H&H and similar hunting cartridges, only a few where considering .375 chambered barrels and cartridges. Looking at a few threads online from 10 years ago, it is apparent we have now come a long way thanks to those innovating in this space – Cutting Edge Bullets, Warner Tool Company, WindCut, Hornady, Berger, Cutting Edge bullets, Badlands precision, TPM Balle, Solid solution design (SSD) among others and creating new slick bullets with impressive ballistic coefficients. Some real, some hype or hope, we have come miles closer to our goal.
Look at what professionals use, it saves you having to walk down the road and back.
However, recalling from lessons learnt in other shooting disciplines, the key to help a sport grow is accessibility, modularity and affordability. In other words, do I have to build a new rifle from scratch for every discipline then buy another scope, dies, press, brass, primers? This would make an already expensive sport almost prohibitive – the equivalent of Dragster racing for the shooting sports. The number of facilities in Europe is still limited making dedicated 2 mile platforms somewhat overkill?
What cartridge could make use of existing long range 338 platforms without having to change your receiver, bolt and chassis and possibly your reloading press as well whilst benefiting from the best bullets made to date? > David Tubb 37XC cartridge
Enter the 37XC brainchild of David Tubb, probably the most accomplished competitive shooter.
The 37XC has nailed it. David Tubb came up with a solution that may just bridge the gap between the two worlds with his line of 33XC, 37XC and 41XC cartridges. Are you familiar with the 338 Lapua cartridge? Well these cartridges make use of the same bolt face that is used for the 338 Lapua, in other words, you can use that same action and bolt for your new build. The 37XC is larger than a 338 Lapua Ackley improved and significantly smaller in capacity than a 416 Barrett(120gr powder vs 189gr ish).
Basically all you need is to rebarrel your action with a 338, 375 or 416 barrel, change the dies and you’re ready to load up some ammo. A barrel with a 1.250 shank will fit a 338Lapua action as opposed to those used on bigger actions requiring a 1.700 shank.
I have compiled some of the data I have found on the 33XC and 37XC Info Facebook group. It is not meant to be a pet load for you to start with. Always start low and work up. Thanks to all those sharing their real world data. The best thing is that most of your standard reloading kit will work just as well for this cartridge as seen in the setup shown by Precision Arms, this person is very knowledgeable in his approach. Find him here
37XC Load data compared to other ELR rounds
|Cartridge||Avg. Charge||Performance||Powder charge increase|
|2850ft/s 300grain berger
3000ft/s 230grain berger
|This is the base charge. We shall see what it takes with other cartridges.|
|37XC||118 grains of rl23 in a 30 inch barrel
126 gr n570 pressure signs, room for 4gr plus more powder
H1000 / h50BMG, H4831
36inch barrel Re33 126grains
36inch barrel 8133 122.5grn
36inch barrel 131.5gr Re33
36inch barrel 119.5gr H1000
34″ barrel 119gr N570
|3150fps with cutting edge 350mth
350 lazer 3091ft/s
400grain Warner flatline 2960ft/s
375Grain Lazer 3053ft/s
377grain MTAC 3075ft/s
352grn MTAC 3265ft/s
CE 352gr MTAC 3165ft/s
CE Lazer 400gr 2920ft/s – our 37XC load
|At least 30% increase over a 338 Lapua|
|41XC||126 grain rl26
32 inch barrel 126 grain rl26
32 inch barrel Rl26 124grain
30 inch barrel 126 gr rl26.
|500 grain CEB lazer in 30inch @ 33 degrees 2830ft/s with the .220 freebore
505Gr Warner Flat lines 1.8twist barrel 2860ft/s
500gr CEB lazer 2880ft/s
2900ft/s 500 gr lazer
450 lazer 2930ft/s
|416 Barrett||505 grain bullet 3190ft/s||180-190 grains (52% increase in powder charge over a 37XC
Now take a look at the wind drift chart, How much is that difference worth to you? That’s the real question.
Want more load data? At the end of this article there is a link for more load data.
Jeff Prat reports positive results using 120.0 grains of N570 pushing a 400 gr. Cutting Edge Lazer at an average of 3012 fps. That’s about 100ft/s faster than my load with the same charge.
DTA SRS rifles in 338Lapua area easily turned into 2mile gun in a 37XC chambering.
Every Reloader’s dream – 0 Standard Deviation. Pictures courtesy of Precision Arms.
In a nutshell, the 37XC is giving us performance approaching that of a 416B with a shorter barrel, less weight, less cost and less financial commitment while matching the 375Cheytac.
What will Tubb’s 37XC cost?
- A new barrel of this length including muzzle brake should hover around £1300-1400/€1600
- New set of dies $330 plus freight and import costs approx. $450/€415/£365 dollars to Europe
- Brass 37XC Peterson Brass (50 pieces) – $122 they’ll be around €162/50 once they get to Europe
- Bullets – approximately $2.90 each for the 400gr Warner flatline in .375
- Press – Keep the same one you have if you’re already loading 338Lapua.
- Barrel wear, estimate 1200-1500 rounds depending how fast you shoot it. (£/€1.30 barrel wear per shot)
The increase in popularity and lower financial commitment of the 37XC seems it’s helping it to catch up and penetrate the elr cartridge market
If it’s the 416 that you’re obsessed with, you have the possibility to get a 41XC.
Above: 41xc with 450 lazer with 33xc with 265 mth for scale.
The 450 lazer reaches 2930ft/s 30 inch barrel burning 126 gr rl26. Thanks to Ryan Leithwood for sharing the picture.
408Cheytac bolt face ELR Cartridges to Match 416Barrett
A new line of cartridges on the 408 Cheytac bolt face is now also hot on its heels with the likes of the 416 and 458 Vestal enabling you to go from a 375Cheytac to a 416Barrett performance with less powder using the same action! In the same way the 37XC enables you to do it on a 338LM bolt face, the 416Vestal enables you to do it on your existing 375cheytac action.
Left to right: 458 Vestal, 416 Vestal, 375Cheytac,338 Lapua
It never ends does it?
Follow this interesting thread “Heavy impacts by Caliber” posted by Brian Wink
David Tubb’s 37XC Load Development
This month of May was special, we received our 37XC barrel for the Desert Tech SRSA2 from Harry at Solid Solution Design in the Netherlands. I had ordered 5 barrels for this rifle that I would receive during the year. I did not need them all at once as I would not have the time to load for each however when I got the delivery, I had 4 other barrels in there in all colours, shades and fluting styles. Christmas time! The barrel is a Bartlein 34″ 1.7 Twist for the 400grain Cutting edge bullet or the 407gr Berger crowned with the Warner Tool Company MOAB muzzle brake, beautifully machined, it’s the best I’ve seen to date.
The barrel is 1.25 at the chamber and tapers to 1″ at the muzzle. Unlike an HTI that may have a 2inch barrel at the chamber, this barrel is a lighter profile than a similar 375 Cheytac in an HTI yet we are firing the same diameter bullet at similar velocities. We’ll get to that comparison in abit.
Why 37XC on a Desert Tech?
The ease of this platform is the possibility to switch from a small caliber training round like the 6.5creedmoor to an ELR round by quickly switching barrels around and providing similar performance to a 375Cheytac rifle with a similar sized barrel. The rifle is very compact and enables you to engage from short range out to 2 miles in this configuration. If you want a rifle that can be used in multiple disciplines, this multicaliber option is worth looking into.
Can you imagine if for each of these rifle builds, you had to buy a scope, a mount and all the other bits that go into a new rifle ?
Keep in mind the fact that most ELR rifle builds are very specific, heavy rifles built for that specific role. That’s alot of money tied up in one rig for one discipline. Unless you’re specifically shooting ELR only as some of the top competitors, like Ryan Cheney or Gene Nowaczyk, Rei Hoang a dedicated rig maybe more commitment than you want and it won’t get much use. Being able to enjoy the rifles you own and getting enough shooting out of them is important given the money you’ll end up putting into these dedicated and specialised rifles.
Next I wanted to find out at which point will the bullet touches the lands so that I could start loading up some rounds for my ladder test at 300meters. I loaded a dummy round in a case that was used for proofing the gun, wrapped a piece of 0.5x.25″ paper around the bullet and seated this bullet. It provides sufficient neck tension to hold the bullet in place while it touches the rifling without being too tight. I remove any excess paper from around the neck before I chamber it. I took about 6 measurements and worked out an average. From then on I move about .010 off the lands. From this point to the seal tight band on the Cutting Edge bullet, I can move 0.024″ before the seal tight band would engage the neck of the cartridge. If I test seating depth in 0.003 increments, that means I have 8 seating depths I can test once I found a load that does well.
Below: Checking how much distance I have to the seal tight band as seen under a magnifying glass. Cutting Edge Bullets informed me that I would not be needing to make huge seating depth tests to tune these bullets.
Next picture, wrapping a piece of paper about 0.003″ thick around a bullet (like a paper patch) inside a fired case to be able to seat a bullet tight enough to measure the distance at which the bullet touches the rifling without using a bushing that would put too much neck tension on this bullet. This was during load development of the 375Cheytac which my spotter Rob was setting up.
The compact dimensions of the Desert Tech might initially deceive you. That rifle houses a real long barrel in there, keep scrolling. The March Genesis ELR scope 6-60×56 provides over 400MOA of elevation. With the lower mount shown here, I have 235MOA of elevation before the scope touches the body of the rifle.
The March Genesis Turrets are large and easy to read. I love doing load development with a high Mag scope such as this.
It allows me to have a very precise point of Aim at 600m which does not induce any error in the hold. Super precise for load development.
I shot load dev on 50x mag like an Fclass rig.
Notice that the length of the 37XC barrel by Solid Solution Designs shown below is almost the length of the entire barreled action of my 300Norma Mag!
Below, setting up to start ladder test at 300m with the SQI-Andix https://www.sqi-andix.com/products/ mounted to the left of the rifle. This is a very compact ballistic velocity scanner that can be easily carried with you. Notice I placed it in the top right corner of my Pelicase for travel so I would have everything with me for zeroing in France.
I loaded 16 rounds for my ladder test, from 116gr to 120.1gr of N570. The Desert Tech bolt does not have the same camming force of some of the larger bolts in custom made actions so I did not want to push this load too much because if the cases get hard to extract, I’m in trouble. I did not have any extraction issues at the velocities I was running it. I stopped at 2927ft/s with a 400gr. Others I spoke to like Goran from Optics Trade whom I also met in France during Ko2M was running his at around 3020ft/s, a full 100ft/s more than mine and comparable with Rob’s 375 Cheytac. However I remembered a comment from the Queen of 2 Miles, “don’t chase velocity chase accuracy”. I kept this in mind while developing the load.
The ladder test at 300m was promising, I had 2 or 3 shots on top of each other in the same horizontal plane. Here I am after getting same point of impact as I increase the charge of the load. Normally at this distance I want all shots touching to enable me to tune the load even more as I did with the 300 Norma Mag shooting 250 Atips.
Below, some data from the ladder test as shown on the
AndiScan micro is an advanced ballistic velocity Doppler radar for measuring muzzle velocity of projectiles. It operates in 24GHz frequency band. It is a highly integrated and extremely small form-factor device that is intended to be directly mounted on the rifle. This frees the user from a complicated setup alignment and it also allows to perform measurements under dynamic conditions. It is a first device of this form-factor on the public market.
A2 model is an updated new version of the original A1 pilot model
Once I was done from the ladder test, I picked 3 loads and went back to the loading bench to load some more ammo.
I had all the cases readily prepared with a base charge so all I had to do is trickle up the difference and seat the bullet. Below you can see the ammo prepared for testing 3 different batches. One of those batches at119gr closed nicely with 4 shots all touching at 300meters. Normally, once I get to this point I will then fine tune and start trying seating depth tests if I am happy with the velocity and extreme spread preferably under 10ft/s for a string.
Once I have this I will usually try the load at 600meters and then fine tune seating depth to keep 5 shots in under a 2inch vertical. The weather started pouring and I had about 10 rounds left and loaded them at 119 grains N570 giving me 2920ft/s. I wanted to see if I could get some dope so I shot 2 rounds at various distances to 1000m. This is not enough to properly do trajectory validation but I was short of time and needed to get the rifle going before flying to France. I decided to load 3 more rounds at 119 to try at 300m and then shoot the other targets. These 3 rounds I shot at 300m again were all touching so I thought the load must be there more or less at least for this competition we have a node then we may need to fine tune when I am back with and I have once fired cases.
My spotter asked me how much does the gun weigh all in, it looked light to him especially compared to his 15kg rig. Rightly so at just under 10kg all in, it was the same weight of an Fclass rifle in a category where most rifles will weigh in just under 18kgs!
Firing a 400gr bullet at 2900ft/s generates substantial recoil even with a good brake, don’t underestimate that you will be firing a 15 round string in quick succession during these ELR competitions so it will get to you. I felt the difference between 33XC shooting a 300gr berger at 3200ft/s and 37XC in the same platform was substantial. The Warner Tool Company MOAB brake did a great job but I needed to couple it to a realistic match weight for it to be truly effective. I realised this the second time I shot it as the scope touched my safety glasses.
Meanwhile I called an engineer friend of mine and told him I needed a solution, firstly to increase the weight of the rifle to about 13.5kgs or just under 29lbs and we needed to find a way to improve the recoil pad. The recoil pad on the stock Desert Tech is a elongated piece of rubber on a plastic clip on type plastic spacers. This is fine for other cartridges upto 33XC but when I switched to this, it was recoiling straight into my collar bone. With our flights just 1 week away, my friend Jeanpierre stepped in to help.
Desert Tech Butt Pad modification
The butt pad had to be adjusted for my body type. With a relatively muscular built and adding on to the heavy recoil, the butt pad needed to come down a good 1.5inches. We attached a butt pad I had lying around from my RPA rifle and attached this to a hard rubber like material that was perfectly cut to match the contour of the Desert Tech butt pad. Jeanpierre made some adjustments to these slots shown in picture two so that the spacer could slide easily without the need to using any tools. This worked perfectly, it was robust and never moved. There was only one thing to find out, what will it shoot like now that we adjusted the butt plate and added another 6lbs plus to the gun? There was not enough time to go back to the ranges so my first shots with the new setup were in France on the zero range at Camp Canjuers.
37XC Zeroing at Camp Canjeurs
I looked forward to trying it out now, having upped the weight by 34%, I was eager to send a few rounds down range so when we got to this 100m facility, I mounted the SQI Andix
I Ran 5 rounds over AndiScan micro unit which gave me an extreme spread of 11ft/s and average of 2936ft/s with 400gr Lazers. At this time of the day, the gravel on this rifle range was cooking. When we lay down we could see heavy mirage and I had to turn down the power to get a good zero.
The first round was high from my Sicily zero. I had removed the scope for travelling as well as the barrel. I then shot a 3 round group shown below to see how the gun was grouping and made 2 more adjustments, I didn’t fire the last round after that. With me I also had the new March High Master 5-42×56 ELR scope.
ELR scope Options
If I would have to own just one scope, it would probably be this, the New 5-42×56 March High Master. This scope has the potential to shoot your rifle to 2 miles yet you can use it for almost any discipline. The wide magnification of 5-42×56 allows use in numerous scenarios. The large turrets enable easy to read and adjust in any condition using gloves or otherwise. The turrets are also lockable by clicking a switch on top of the turret which I find handy when travelling.
The windage knob has two scales from left to right and from right to left. One full turn on the windage is 25MOA. It has a staggering 138MOA of vertical adjustment. this means if I zero it at 100m, I can take my 37xc to 2500-2600m. This scope sits in an ERATAC adjustable mount with 0-70MOA of adjustment in Quick Detach mount. I did remove it and mount it again and there was no change in poi. I love the fact that I can easily mount and unmount this scope/mount combo in the same place without zero point of impact shift as tested below.
Most ELR shooters do not really have a 100meter zero as these guns never really engage anything shorter of 1100m to start with.
So let’s discuss using the Offset zero method that is popular with many US shooters. Let’s say your gun needs 25 MOA to 1100m. They will zero the rifle to impact 25 MOA high at 100m. This effectively means that the rifle is now zeroed at 1100m. With this scope, If i dial 138MOA from my 1100m zero, I can shoot to 2850m without needing any additional appendice. I will insert the OFFSET of 25 MOA in my kestrel or which ever app you use, and this amount will be deducted from your correction. This method requires you to measure the offset accurately on the zero range if you wish to use it properly. You also need a tall target to ensure your shot is captured on paper when it hits 25MOA high. At Camp de Canjeurs, we had one board for every 5 shooters with an A4 paper target each. If you had an offset method like my spotter Rob, you would not be able to do this properly with other A4 targets attached to your same board being shot by other shooters at the same time.
Another method that can be used is to check how far your targets will be on day two to find out if you need to make adjustments to your adjustable base such as Eratac or the Ivey mount.
The eratac adjusts by means of unscrewing one front and one rear fixing screws, adjusting the nut to the desired amount of adjustment and tightening it again.
Eratac 0-70MOA adjustable mount for Extreme long range shooting, enavles you to engage further with your existing scope.
You can get a 0-70MOA or Mil equivalent Eratac as well as an 80-150MOA version which is lesser known out there. This allows you to dial in 100MOA on the eratac so that you will still have another 130MOA on your scope which means you now have 230MOA on the scope. Assuming you were good to go with your 100m zero out to 2500m, you can decide to adjust the eratac before day 2 of the shoot so that you will engage the 2400,2700 and 3200m targets with your 100MOA adjustment on the eratac and the difference dialed in on your scope turret.
Harry Drescher from solid solution designs decided to use an Ivey Mount wherein he set the elevation turret of the ivey so that he would have a base adjustment as described above with the eratac and then use the scope turret to dial in the remaining shots.
The March Genesis seen below used on Marco Been’s Warner Tool Company Rifle allows you to dial from 100m zero to 350+ MOA. Learn about the March Genesis here.
Harry Drescher with his Desert Tech HTI and SSD custom barrel 36Inch, Adjustable Bag Rider, Zero Compromise Scope and Ivey Mount.
There is an adjustable bag rider for almost every gun. Check out their site Adjustable Bag Rider
Order your Ivey Mount here
King of 2 Miles 37XC
During the Ko2M shoot seen below, the presenter asks Benjamin Gineste, what is that rectangular box beneath his forend? Now you know that’s the weight I had to slap on to the rifle to make it a little bit more comfortable to shoot for 15 rounds in succession
The other thing with chambering these long 37XC round in a bullpup rifle like the Desert Tech is that you may need to move your head around abit till you get use to the movement when loading a marker sized round beneath your cheek. The loaded round needs to be slipped in the chamber just under your nose and it may get some getting use to till you get accustomed to handling these long cases. Also the feeding port on the DT was made for 338LM rounds in magazine length so if you leave the round there and then go into position and try chambering that long round, it may get a little hairy so in order to avoid this, I typically chambered half the round by hand then just closed on the bolt. Remember, there is no action, the round goes straight into the chamber whereas in a conventional rifle, your round sites in the action feeding ramp before you put forward that round into the chamber. Once you get into it you’ll find its not that much of an issue.
Stay tuned for more info coming soon!
In order to place my cheek always in the same spot, I added a small plastic sticker that I can see just beneath my eye when I rest on the cheekpiece, this enables me to be consistent and get the right eye relief every time enabling me to find the target fast. The other one is located on the pistol grip, this enables me to place my hand in the same spot applying same pressure everytime. The moment I feel the sticker, I know I’m good to go awaiting spotter to call in the airstrike -send it!
That’s what it’s like to feed these from the entry port made for smaller rounds. The HTI on the other hand has a much larger cut out made for handling upto 50 BMG.
For more information, I invite you to read David Tubb’s 37XC cartridge guide on his own facebook group
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