The factory barrel is 29", one inch short of the 30†BenchRest model. I use Varget in a number of guns that all have shorter barrels and it is one of my favorite powders. If I cant get good groups with Varget I figure I have something wrong. 22" 30-06 and .270 sub MOA, .220 Swift with a 26" barrel, dime sized groups and now this 6MM BR with a 29" barrel is really nailing it. The only non factory is my .220 Swift. I built that around a Shilen #3 that was available at the gunsmith school for a pretty good price.
The other point is that if you are basing powder selection on how much burns in your barrel length you will never get the best accuracy. The ideal situation is that all the powder is consumed within the brass itself. So any powder that burns in the barrel is having a negative affect because the pressure curve is all messed up. You want peak in the bell and a pretty sharp drop after that. If you choose any powder figuring it will burn in the barrel you end up with a pressure curve that starts off nice but drags on rather than give a smooth falloff. Keep in mind that unburned powder also adds to the a mass you are pushing down the barrel. No small matter is that the pressure is dropping rapidly as the mass of unburned powder speeds down your barrel. This lower pressure is going to ignite some of that powder in a less efficient manner than the powder in the case, which had the benefit of over 50,000 PSI, Pressure is critical to ignition. So you may think you are pushing a 68 grain bullet, but if you are using so much powder that it has granules tumbling down the barrel, these have to added to the weight of the bullet itself, at least until they burn off.
Every barrel has a preference but you can assume that the powder density allows you to fill the case as full as possible will give you every advantage. Trying for faster powders may help but of you can only go with a 70% load density your powder may not burn consistently and be position sensitive.
All this of course provides you with plenty of issues where one thing seems better but it contradicts another rule. Try to find a powder that burns and quickly as possible without sending half it weight powder down the barrel.
If you are shooting single shot, try jamming the bullet into the lands. It helps align the brass and bullet concentricity and the extra pressure on ignition will give you a much better bell curve of pressure. The whole game is about the pressure curve. The curve determines the barrels whip and you need it the same each shot. If you don't jam, then neck tension may be different each shot and thus the pressure curve will be different as well. So each shot the bullet exits with the barrel in a different location . Try to establish enough safe neck tension to give the cleanest possible burn within the case itself. If you cannot seat into the rifling, (hunters should not unless you can fire your gun to empty it) then learn to anneal your brass so your neck tension is the same with each bullet on release. This helps the pressure curve of the burn to be the same each time. All this of course assumes you have made selections that have your bullet properly stabilized in flight.
A hotter primer can at times help with a more consistent powder ignition and thus give more FPS ( at times up to 75 FPS) and a quicker pressure curve. You can do something with each powder to establish a good curve. Of course, workup to the load, especially when introducing a new primer. Winchester primers in my gun give me 50 FPS extra while changing nothing else./ Since velocity is the correct result of the pressure, you can assume that the primer is increasing your overall chamber pressure, so proceed with caution.
every powder than can be user in your gun safely has a sweet spot. It may never have as good as sweet spot as another powder but if you are stuck for now using only a handful of powders, the quickest way to know what load is your best with that powder and bullet, primer combination is to ladder test. It can tell you in 10 shots what your charge should be for your particular combination. The results are stunning and may very well change your mind about what powders you should use and if you need to weigh or throw your charges. That is another discussion, Google how to ladder test, it will change the way you approach load development and powder selection. It will also keep you from using up your barrel, just to find the right load.
In any event, the proof is in the pudding. Every day groups in .1s and that .096 just made my day. I have over 14 powders to choose from and I keep coming back to Varget, 3 to 1 over every other powder I use.
The other point is that if you are basing powder selection on how much burns in your barrel length you will never get the best accuracy. The ideal situation is that all the powder is consumed within the brass itself. So any powder that burns in the barrel is having a negative affect because the pressure curve is all messed up. You want peak in the bell and a pretty sharp drop after that. If you choose any powder figuring it will burn in the barrel you end up with a pressure curve that starts off nice but drags on rather than give a smooth falloff. Keep in mind that unburned powder also adds to the a mass you are pushing down the barrel. No small matter is that the pressure is dropping rapidly as the mass of unburned powder speeds down your barrel. This lower pressure is going to ignite some of that powder in a less efficient manner than the powder in the case, which had the benefit of over 50,000 PSI, Pressure is critical to ignition. So you may think you are pushing a 68 grain bullet, but if you are using so much powder that it has granules tumbling down the barrel, these have to added to the weight of the bullet itself, at least until they burn off.
Every barrel has a preference but you can assume that the powder density allows you to fill the case as full as possible will give you every advantage. Trying for faster powders may help but of you can only go with a 70% load density your powder may not burn consistently and be position sensitive.
All this of course provides you with plenty of issues where one thing seems better but it contradicts another rule. Try to find a powder that burns and quickly as possible without sending half it weight powder down the barrel.
If you are shooting single shot, try jamming the bullet into the lands. It helps align the brass and bullet concentricity and the extra pressure on ignition will give you a much better bell curve of pressure. The whole game is about the pressure curve. The curve determines the barrels whip and you need it the same each shot. If you don't jam, then neck tension may be different each shot and thus the pressure curve will be different as well. So each shot the bullet exits with the barrel in a different location . Try to establish enough safe neck tension to give the cleanest possible burn within the case itself. If you cannot seat into the rifling, (hunters should not unless you can fire your gun to empty it) then learn to anneal your brass so your neck tension is the same with each bullet on release. This helps the pressure curve of the burn to be the same each time. All this of course assumes you have made selections that have your bullet properly stabilized in flight.
A hotter primer can at times help with a more consistent powder ignition and thus give more FPS ( at times up to 75 FPS) and a quicker pressure curve. You can do something with each powder to establish a good curve. Of course, workup to the load, especially when introducing a new primer. Winchester primers in my gun give me 50 FPS extra while changing nothing else./ Since velocity is the correct result of the pressure, you can assume that the primer is increasing your overall chamber pressure, so proceed with caution.
every powder than can be user in your gun safely has a sweet spot. It may never have as good as sweet spot as another powder but if you are stuck for now using only a handful of powders, the quickest way to know what load is your best with that powder and bullet, primer combination is to ladder test. It can tell you in 10 shots what your charge should be for your particular combination. The results are stunning and may very well change your mind about what powders you should use and if you need to weigh or throw your charges. That is another discussion, Google how to ladder test, it will change the way you approach load development and powder selection. It will also keep you from using up your barrel, just to find the right load.
In any event, the proof is in the pudding. Every day groups in .1s and that .096 just made my day. I have over 14 powders to choose from and I keep coming back to Varget, 3 to 1 over every other powder I use.
It looks like the day I picjed it up at the 'smiths, 6 weeks ago. All 268 rds. fired were with N133 & most recently N135. I know from past experience if those same number of rounds were with most other types of powders, I would be doing the JB routine. On top of being very clean burning I also find it to work in any & all my slow twist barrels, and it's very consistant from one can/lot to another. Hard to find I know but the search is worth it to me. Your problems have nothing to do with loading techniques and everything to do with the fouling associated with some powders.
