The 6mm BRX vs 6mm BR
The 6mm BRX uses 6mm BR brass as the base brass. Making the 6mm BRX is easy and involves loading up 6mm BR brass and fire forming it in a 6mm BRX chamber (the fire forming loads can also be very accurate). The net result is the 6mm BRX case that has a 30 degree shoulder (same as the 6mm BR) but the body of the case is .100″ longer than the 6mm BR and it picks up a fair amount of additional powder capacity over the 6mm BR.
The 6mm BRX has the capability to easily push the 105-108 gr. 6mm bullets up in the 3000 fps range.
There are Die Sets Available for the 6mm BRX – Contact 6mmAR.com to order.
6mm BRX Load and Chrono Information
The general consensus is that Varget, Reloader 15 and H4895 are three of the most popular powders of choice for the 6mm BRX, and the CCI BR-4 and #450 primer are also primers of choice for some shooters. This author used CCI BR-4 primers and had good results with them. This author also found H4895 and VV N140 to be an excellent powder in the 6mm BRX.
Top end loadings vary (depending on the rifle, barrel, lot of powder, etc.) but top end accurate loadings with the 105-108 gr bullets are generally being reported in the range of 2900 – 3000 fps (with exceptions both up and down).
Making Brass – Very Easy!
The technique used by this author to make 6mm BRX brass is very easy – just load up factory 6mm BR brass with a non-moly bullet using standard 6mm BR loads, using good neck tension (new out of the box brass is fine, otherwise use .004″ neck tension) making sure the bullet is jammed into the lands about .025″-030″, and shoot them in the 6mm BRX chambered rifle – Done! Not only did this author find that the fire forming loads were very accurate (using standard 6mm BR loads) but the brass, after fire forming, came out very consistent and uniform. This author is not sure why some use the “false shoulder” method with 6mmBRX brass (too much work and works the brass too much in this author’s opinion). The false shoulder method involves necking up 6mm BR brass with something like a .257″ or .264″ mandrel, then necking down a portion of the neck to 6mm again to make a “false shoulder” to hold back the case when it is chambered. For fire forming loads, this author found with good neck tension (new out of the box brass, or .004″ neck tension) and loading bullets .025″ in the lands, the cases were held back fine for fire forming.
Chronograph Testing – At this point this author has done some chrono testing, which is noted below. The rifle involved is a target rifle with a 30″ 6mm 1:8 twist 4 groove barrel with a 6mmBRX chamber similar to the reamers described below on this page . The results were as follows:
Chronograph Loadings: 6mmBRX brass, fire formed from 6mm BR Lapua Brass, with the primers noted and all results are for five shot strings:
Chrono Results Still To Be Posted – Work on this page still in progress.
General Comments on the 6mm BRX:
The cartridge seems to be extremely accurate and easy to load for.
6mm BRX Reamers:
Reamer Above = No Neck Turn Reamer for prior Lapua “Cardboard Box” brass that loaded out around .269″ – .2695″ and Great For General All Around Shooting with all brass.
Reamer Below = No Neck Turn Reamer For Lapua’s Newer “Blue Box” Brass That Loads Out Around .2675″ – .268″
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.