The 6mm Super LR Cartridge

The 6mm Super LR Cartridge

The 6mm Super LR Cartridge – Its Attributes

Conceptually, the 6mm Super LR is like a long bodied 6XC (case body about .120″ longer).  The Super LR has a long neck (.321″ vs. the .263″ long neck of the parent  .243 Winchester case).  The Super LR also has a 30 degree shoulder angle vs. the 20 degree shoulder angle of the .243 Winchester parent case.  The Super LR has a case capacity of approximately 54 gr. of water weight vs. 49 gr. of water capacity of a 6XC and 55 gr. of water capacity for the .243 Winchester.

The Super LR has sufficient case capacity to permit the 115 gr. 6mm bullets to be shot up in the 2950 – 3000 fps range without being “on the edge” of maximum pressures.  As a competition shooter looking for consistency over long strings of fire, I find this appealing.  Frankly, I never had good consistent accuracy over long strings of fire with loads right up at “max”.  If you do not need to run sustained fire in long strings, you can “hot rod” things more.  Testing has shown that the Super LR has the capability to run the 115’s up around 3100 fps without issues.  If you like to shoot the 105-108 gr. class of 6mm bullets, the 6mm Super LR can also push them up in the 3150-3200 fps range with the right selection of powders.  In addition, if you like to shoot the 105-108 gr. bullets and like to keep them close to the lands, the Super LR cartridge case neck is long enough to give most of them a good bearing surface purchase, even if the chamber is throated for the 115 gr. bullets.  This is not possible with the parent .243 Winchester case with its shorter neck.

The 30 degree shoulder angle of the 6mm Super LR is another potential benefit of the Super LR.  Not only does it help to avoid the throat torching effect that people associate with the .243 Winchester (because of the .243’s short neck and mild 20 degree shoulder angle), but the 30 degree shoulder angle has also been a hallmark of some very accurate cartridges (6 PPC, 6 BR, 6XC, 6.5 x 47 Lapua, etc.).

These attributes of the 6mm Super LR make it an ideal cartridge for a variety of uses, such as competition shooting, varmint hunting (particularly for long-range work), and other types of shooting.

Brass Is Easy – No Neck Turning & No Initial Trimming Option

Making brass for the 6mm Super LR is very easy, just take .243 Winchester brass, and lube the cases (particularly the neck and shoulder of the cases) with a lube like Hornady One Shot spray lube, and run them in and out of a 6mm Super LR full length sizing die, and that’s it – your brass is made!

For an easy “no neck turn” brass option with no initial trimming either, use a chamber reamer like one of those shown on this page with either Winchester brand .243 Win. brass (the author’s favorite) or Remington brand .243 Win. brass.  Both of these brands of brass have shoulder metal that is right around the same thickness as the neck metal of the brass, so that when you re-form the shoulder of the case there are no “donut” issues. 

Imported .243 Win. brass (Lapua and Norma) and Nosler Custom .243 Win. brass all have shoulder metal that is considerably thicker than the neck metal, and reforming these to the 6mm Super LR makes a “donut” at the base of the neck that requires the cases to be neck turned after forming.

This author has experimented with all types of .243 brass with the 6mm Super LR, and honestly, the Winchester or Remington brands of .243 Win. brass work out to be very excellent.  First off, it’s very easy to reform these brands to the 6mm Super LR case (just run the cases through the full length sizing die, and that’s it, no neck turning or initial trimming necessary).  Secondly, these brands of brass are very reasonably priced and readily available.  Finally, with some basic weight sorting of the brass, and the culling out of an oddball case here and there, it’s easy to wind up with batches of brass that are of very high quality and consistency.  In truth, I weight sort and cull cases, no matter what brand of brass I use, and all brands of brass have weight variances and odd ball and defective cases (yes, my “rejects” bin has plenty of Lapua cases in it too).   For reference, I weight sort brass so that a batch is all within 1 grain (i.e. like brass that is 158 to 158.9 gr. is in one batch and 159 to 159.9 gr. is in another batch, etc.)   Testing with the 6mm Super LR has not borne out an advantage to using a particular brand of brass if it is weight sorted, with the culling out of any oddball or defective cases.

Die Sets Readily Available – Contact 6mmar.com To Order

Reloading dies are readily available for the 6mm Super LR.  At the time of the writing of this, factory 6mm Super LR dies are set to be made by Redding (i.e. Type S. FL Bushing die and Competition Seater) and to make the 6mm Super LR cases, all you need to do is lube up some .243 Win. brass with something like Hornady One Shot spray lube and run the cases through the sizing die and that’s it, the cases are done!

In addition, if you already have a 6XC die set, you can run properly lubed .243 Win. cases in and out of a 6XC sizing die with the die approximately .120″ up from the position it would normally be used.   Using a 6XC die set for the 6mm Super LR is a little bit tricky, but it can be used, although the sizing die does not hit the bottom .120″ of the brass on re-sizing.  Since factory 6mm Super LR dies are available, the best option is to purchase and use them.

Working With The 6mm Super LR

Shortly after making up a few test cases the first night, a reamer order was called in.  Once the reamer was received, a test barrel was immediately chambered up with the 6mm Super LR for testing.  Testing immediately showed promise, both in terms of velocity and accuracy with the 6mm Super LR.  The objective was not looking for blistering speed, just a good solid 2950 – 3000 fps with the 115 gr. bullets without having to run the cartridge hard, and the Super LR was clearly up to that.  In addition, the accuracy was there with the cartridge as well.

For load data, one can typically use similar loads as one would use with a .243 Winchester as the capacity of the cases is very close.  This really helps make the 6mm Super LR easy to work with, because there is a lot of loading data out there for the .243 Winchester.

Shooting the 6mm Super LR – Very Accurate And Consistent

After the successful initial testing with the 6mm Super LR, a new 6mm 1:7.8″ twist Bartlein barrel was purchased.  After the barrel was received (which seemed like forever), this new barrel was chambered up in the 6mm Super LR and then installed on a prone rifle with a Barnard action.

The first testing done with the rifle was with H4831SC powder, and a load of 43.5 gr. of it seemed very accurate at 100 yards with the DTAC 115’s.  When this load was chronographed, the muzzle velocity of the 115 DTAC’s was right around 3000 fps (right in the target velocity range).  The load seemed to be “good to go”, so zeros were obtained for shooting not only with a scope but with iron sights as well.  The plan was to try the 6mm Super LR out at 600 yards in the next 3 x 600 yard match.

The first 3 x 600 yard match attended with the 6mm Super LR immediately indicated that there was merit to the 6mm Super LR.  In the past, I had shot well in 3 x 600 yard matches and had a “clean” here and there, but never two in the same match.  The first time out with the 6mm Super LR netted up three cleans in a row for my first 600 aggregate score in a 3 x 600 yard match – “Wow”, that’s one way to be convinced you are on the right track, shoot the whole day and don’t drop a single point!

Follow up match shooting with the 6mm Super LR was just as good with the original Bartlein barrel as it was with other additional barrels (7.5″ twist) that have been chambered up, and I was able to accumulate a string of my highest scores shot in competition, including many 600 and 1000 yard “cleans”.  Many of these matches were shot with the Berger 115 gr. VLD bullets in the 6mm Super LR, but the 105-108 gr. bullets were used as well, all with the same chambering.   Based on these match and testing results, there is no question that the Super LR cartridge is an inherently accurate and consistent cartridge, and the design of the cartridge accomplished all that was expected of it.

Awesome For Long-Range Competition, Hunting & Varminting!

While the focus of this author’s work with the 6mm Super LR has been primarily in the competition shooting venue, it is clear that the very attributes that make the 6mm Super LR a great cartridge for longer range competition work, also make it exceptional for varmint and other hunting, particularly for long-range work.   For varminting, push something like a plastic tipped .500 B.C. 6mm 105 gr. Hornady A-Max bullet out of a 6mm Super LR at 3150 fps. and you clearly have some very long-range striking power with very superior wind drift numbers and explosive impact potential.  Couple this with the fact that you can still hit the magazine length for a short action (i.e. around 2.8″ OAL) and you have a very versatile 6mm cartridge with plenty of power and long-range accuracy.

Reamer Prints Below

Below – 6mm Super LR reamer – throated for 115’s (#1303 Below)

Below – 6mm Super LR/S reamers (shorter throat – see notes on print)

#1307 below – For Bolt Guns

#1304 below – For Semi Auto Guns (more generous body dimensions)

Notes On OAL’s With Certain Bullets

With The 6mm Super LR Reamer:

For the 6mm Super LR Reamer above (i.e. with the .120″ free bore, which is throated for the 115’s) the following bullet measurements were made to show at what OAL the noted bullets hit the lands:

DTAC 115’s (Lot #204258) 2.887″ OAL (Ideal OAL)
Berger 115 VLD (Lot #1422)  2.952″ OAL (Ideal OAL)
JLK 115 VLD (No Lot #) 2.920″ OAL (Ideal OAL)
Sierra 107 (Lot #0008747115518) 2.890″ OAL (Forward in neck but good OAL)
Hornady 105 A-Max (Lot #2090321) 2.833″ OAL (Ideal OAL)
Berger 108 gr BT (Lot #1539) 2.848″ OAL (Ideal OAL)
Lapua 105 gr Scenar (Lot #LMLME1) 2.860″ OAL (Ideal OAL)
Berger 105 gr VLD (Lot #1415) 2.935″ OAL (Forward in neck quite a bit, works but barely)
Berger 100 gr BT (Lot #1945) 2.851″ OAL (Forward in neck more but still good OAL)
Berger 80 gr Flat Base (Lot #800) 2.750″ OAL (Forward in neck more but still good OAL)
Hornady 87 gr V-Max (Lot #2050099) 2.768″ OAL (Forward in neck more but still good OAL)

Note:  When the term “Ideal OAL” is used, it means the junction of the boat tail and bearing surface of the bullet is forward of the junction of the neck and shoulder of the case by about .025″ or so.  When the term “Forward in neck but good OAL” is used it means the junction of the boat tail and bearing surface of the bullet is forward of the junction of the neck and shoulder of the case by about .040″ – .070″ or so (depending on the bullet involved) which is still good because the cartridge neck is .322″ which means you have about .250″ plus of neck still holding onto the bullet.

The Berger 105 VLD’s (newer lot #’s after Lot #591 with real streamlined front end) sit pretty far forward in the neck of the case.  They are usable with the throating on this reamer, but just barely.  Options instead of this bullet would be the Sierra 107, the Berger 108, the Hornday 105 A-Max, and the Lapua 105 Scenar which all have an “Ideal OAL” with this throating.

Some 105 – 108 gr bullets would most likely also be good for magazine feeding with this throating in a short action:  The  Berger 108, the Hornday 105 A-Max, and the Lapua 105 Scenar

With The 6mm Super LR/S Reamer:

For the 6mm Super LR/S Reamer above (i.e. with the .075″ free bore, which has a shorter throating for across the course chambering, magazine feed rifles, varmint rifles shooting smaller or lighter bullets, etc.) the following bullet measurements were made to show at what OAL the noted bullets hit the lands:

DTAC 115’s (Lot #204258) 2.842″ OAL (A little back in case)
Berger 115 VLD (Lot #1422)  2.906″ OAL (Good OAL)
JLK 115 VLD (No Lot #) 2.873″ OAL (Ideal OAL)
Sierra 107 gr (Lot #0008747115518) 2.842″ OAL (Ideal OAL)
Hornady 105 A-Max (Lot #2090321) 2.792″ OAL (At jct of neck and shoulder)
Berger 108 gr BT (Lot #1539) 2.802″ OAL (Good OAL)
Lapua 105 gr Scenar (Lot #LMLME1) 2.806″ OAL (Ideal OAL)
Berger 105 gr VLD (Lot #1415) 2.887″ OAL (Forward in neck a bit but works well)
Berger 100 gr BT (Lot #1945) 2.798″ OAL (Forward in neck a little but works well)
Berger 80 gr Flat Base (Lot #800) 2.706″ OAL (Good OAL)
Hornady 87 gr V-Max (Lot #2050099) 2.717″ OAL (Good OAL)

Note:  When the term “Ideal OAL” is used, it means the junction of the boat tail and bearing surface of the bullet is forward of the junction of the neck and shoulder of the case by about .025″ or so.  When the term “Forward in neck but good OAL” is used it means the junction of the boat tail and bearing surface of the bullet is forward of the junction of the neck and shoulder of the case by about .040″ – .070″ or so (depending on the bullet involved) which is still good because the cartridge neck is .322″ which means you have about .250″ plus of neck still holding onto the bullet.  “Good OAL” means the bullet junction of the boat tail and bearing surface is still ahead of the neck and sholder of the case. “Back in case” means part of the bearing surface of the bullet is back beyond the necks/shoulder junction (although the bullets still shoot very well there in many cases).

With The 6mm Super LR/SS Reamer (Not Shown):

For the 6mm Super LR, we also have another shorter throater reamer that has a .040 free bore that is set up for certain uses.  If you want to shoot the 115 gr DTAC’s, or the 107 Sierras, or the 95 gr Sierras, and need to hit 2.800″ OAL as the target OAL (i.e. for certain magazine feed applications requiring a short OAL, or varmint rifles shooting smaller and lighter bullets, etc.) this reamer is ideal.  The following bullet measurements were made to show at what OAL the noted bullets hit the lands (i.e. with the 6mm Super LR/SS reamer):

DTAC 115’s (Lot #204258) 2.797″ OAL (Back in case)
Sierra 107 (Lot #0008747115518) 2.799″ OAL (Very slightly back in the case)
Sierra 95 gr (Lot #0037165068895) 2.798″ OAL (Forward in neck a bit but good)
JLK 115 VLD (No Lot #) 2.815″ OAL (A little back in case)
Berger 115 VLD (Lot #1422)  2.866″ OAL (A little back in case)
Hornady 105 A-Max (Lot #2090321) 2.749″ OAL (Back in case)
Berger 108 gr BT (Lot #1539) 2.757″ OAL (At jct of neck and shoulder)
Berger 105 gr VLD (Lot #1415) 2.850″ OAL (Forward in neck a little but very good)
Berger 100 gr BT (Lot #1945) 2.753″ OAL (Ideal OAL)
Berger 80 gr Flat Base (Lot #800) 2.660″ OAL (Ideal OAL)
Berger 70 gr Flat Base (Lot #487) 2.665″ OAL (Forward in neck a bit but good)
Hornady 87 gr V-Max (Lot #2050099) 2.665″ OAL (Ideal OAL)
Hornady 75 gr V-Max (Lot #2060258) 2.660″ OAL (Forward in neck a bit but good)

Note: 

This 6mm Super LR/SS reamer would also work shooting the JLK 115 VLD’s mag length in most rifles, since actual and practical magazine length for a lot of magazines and magazine wells for a lot of short action rifles is somewhere between 2.840″ to 2.865″ (and larger for some other rifles, like the MAK tube gun short action magazines allow a 2.880″ OAL loading).

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Max Case and Trim Length for Brass Cases

There is no formal established max case or trim lengths for the brass.   The author suggests the following for guidelines:

Max Case Length:  2.036″

Trim Length:  2.026″

Written by Robert Whitley for 6mmar.com, but subsequently removed, we feel this information is so helpful that we posted it for future reference and archive purposes. Contact Robert at www.6mmar.com for info and purchase enquiries.