6BR velocities... what I see vs. what I read...
- Thread starter memilanuk
- Start date
memilanuk
Gold $$ Contributor
0.1gr... ye gads. Do you have any idea how long it takes me to weigh charges w/ this retarded scale in 0.3gr increments?!? :,
I wasn't going by any 1% rule, but just what I've always used for .308 and smaller cases.
I might knock it down to smaller increments... depends on how much punishment I think I can take at the reloading bench. Right now I'm not sure I can hold/shoot steady enough from a rest to discern the difference. I've been shooting mostly iron-sights and sling this summer, so my bench shooting skills, limited as they are, are pretty rusty right now.
I wasn't going by any 1% rule, but just what I've always used for .308 and smaller cases.
I might knock it down to smaller increments... depends on how much punishment I think I can take at the reloading bench. Right now I'm not sure I can hold/shoot steady enough from a rest to discern the difference. I've been shooting mostly iron-sights and sling this summer, so my bench shooting skills, limited as they are, are pretty rusty right now.
Forum Boss
Administrator
Monte, this is just a voodoo guess, but based on your numbers I think you'll find a "happy spot" at 31.1-31.3 with the bullets .015" into the lands.
With the increased start pressure of jammed, naked bullets I think 32.0 will be too much.
UPDATE: Monte, I had one rifle, with a factory bbl, that didn't like jammed bullets at all--it tossed lots of flyers. When I inspected a dummy round to see the engraving on the jacket, the marks were on 2/3 of the Jacket diameter only. There was one third where there was almost no engraving. Inspecting the bbl with a bore-scope, sure enough, the entrance to the lands was not uniform. In this 6-groove bbl, two lands weren't formed correctly in the very start of the bbl. In that bbl, jamming the bullet caused everything to line up off-center.
In a good bbl that shouldn't be an issue. But if you get bad results with the jamming experiment--check your engraving for signs that the entrance to the rifling ain't kosher.
With the increased start pressure of jammed, naked bullets I think 32.0 will be too much.
UPDATE: Monte, I had one rifle, with a factory bbl, that didn't like jammed bullets at all--it tossed lots of flyers. When I inspected a dummy round to see the engraving on the jacket, the marks were on 2/3 of the Jacket diameter only. There was one third where there was almost no engraving. Inspecting the bbl with a bore-scope, sure enough, the entrance to the lands was not uniform. In this 6-groove bbl, two lands weren't formed correctly in the very start of the bbl. In that bbl, jamming the bullet caused everything to line up off-center.
In a good bbl that shouldn't be an issue. But if you get bad results with the jamming experiment--check your engraving for signs that the entrance to the rifling ain't kosher.
memilanuk
Gold $$ Contributor
Mod,
Well, I got 30 rds loaded up... 5 rds each of 30.5-31.5gr in 0.2gr increments,+/- 0.02gr, I can only take so much), seated out 35 thou from where they were. If'n I find what looks like a node in there somewhere, I'll zero in on it in smaller resolution increments. I had a bad experience w/ running a wee bit too hot of a load this summer, still culling cases out of my .308 stock from that little 'learning experience'. Most of the primer pockets on these cases are still tighter than a tick's behind, and I'd like to have them stay that way as long as possible, so I'm hoping the 'node' is somewhere down in the nice no-pressure-signs-at-80°F range too!
Lynn,
I've got a Redding #2 beam scale... reasonably nice scale, like it a lot better than an RCBS 10-10 I'd had before it. Currently it's sitting there waiting for the day when I pitch that AccuLab across the room. It's far more accurate... when it hold zero. Since it works normally most of the time, I can only presume it's something local in the environ which comes and goes that makes it flip out... I've yet to figure out what exactly it is. I'm thinking the EM shielding on these units ain't as good as maybe it should have been. I've been using a VibraShine trickler to trickle up, and the calibrated thumb-n-finger method to pinch and roll out any excess back into the hopper of the measure.
Do you normally just shoot 5rd groups sequentially, i.e. one group for one increment, then another group for the next, or do you go round-robin ala the Optimal Charge Weight theory to spread out the effects of barrel heating and fouling more evenly amongst the groups?
TIA,
Monte
Well, I got 30 rds loaded up... 5 rds each of 30.5-31.5gr in 0.2gr increments,+/- 0.02gr, I can only take so much), seated out 35 thou from where they were. If'n I find what looks like a node in there somewhere, I'll zero in on it in smaller resolution increments. I had a bad experience w/ running a wee bit too hot of a load this summer, still culling cases out of my .308 stock from that little 'learning experience'. Most of the primer pockets on these cases are still tighter than a tick's behind, and I'd like to have them stay that way as long as possible, so I'm hoping the 'node' is somewhere down in the nice no-pressure-signs-at-80°F range too!
Lynn,
I've got a Redding #2 beam scale... reasonably nice scale, like it a lot better than an RCBS 10-10 I'd had before it. Currently it's sitting there waiting for the day when I pitch that AccuLab across the room. It's far more accurate... when it hold zero. Since it works normally most of the time, I can only presume it's something local in the environ which comes and goes that makes it flip out... I've yet to figure out what exactly it is. I'm thinking the EM shielding on these units ain't as good as maybe it should have been. I've been using a VibraShine trickler to trickle up, and the calibrated thumb-n-finger method to pinch and roll out any excess back into the hopper of the measure.
Do you normally just shoot 5rd groups sequentially, i.e. one group for one increment, then another group for the next, or do you go round-robin ala the Optimal Charge Weight theory to spread out the effects of barrel heating and fouling more evenly amongst the groups?
TIA,
Monte
Both seem to wor similarly at 1K...memilanuk
Gold $$ Contributor
Got back from the range... still debating whether that was a complete waste of time or not 
On the plus side... the chrono worked all the time,still need to recharge the battery), and the scale behaved itself last night so it wasn't too irritating. The MV's were, by and large, much more consistent. Measured case head expansion on rounds as they were fired per a suggestion and it seems the loads weren't too hot.
On the minus side... didn't pick up much velocity. If anything, it went down some. I did allow a little more time between groups,measuring case heads, taking notes, etc.) so maybe things didn't heat up as much.
Charge MV,avg) E.S. S.D. Comments
30.50 2814 7 3 5 shots
30.70 2834 9 3 5 shots, looked like it wanted to group
30.90 2854 28 10 5 shots
31.10 2863 12 5 5 shots
31.30 2877 15 6 5 shots
31.50 2896 7 2 5 shots
Groups were uniformly... crap. Honestly, I shoot better than this w/ the iron sights on my Service Rifle AR.
May have to play w/ this seating depth variable some more... I like the more consistent MV's, but the group sizes are terrible.
On the plus side... the chrono worked all the time,still need to recharge the battery), and the scale behaved itself last night so it wasn't too irritating. The MV's were, by and large, much more consistent. Measured case head expansion on rounds as they were fired per a suggestion and it seems the loads weren't too hot.
On the minus side... didn't pick up much velocity. If anything, it went down some. I did allow a little more time between groups,measuring case heads, taking notes, etc.) so maybe things didn't heat up as much.
Charge MV,avg) E.S. S.D. Comments
30.50 2814 7 3 5 shots
30.70 2834 9 3 5 shots, looked like it wanted to group
30.90 2854 28 10 5 shots
31.10 2863 12 5 5 shots
31.30 2877 15 6 5 shots
31.50 2896 7 2 5 shots
Groups were uniformly... crap. Honestly, I shoot better than this w/ the iron sights on my Service Rifle AR.
May have to play w/ this seating depth variable some more... I like the more consistent MV's, but the group sizes are terrible.
Not that this necessarily applies to your rifle, but do you have any Benchmark? I couldn't get my Varget loads to group less than an inch after I broke it in last week yet the Benchmark loads did fairly well. I'm still using one of those 'hot' lots of Varget which may be a problem too, but I can't bring myself to dump it into a coffee can and burn it up. -Rod-
memilanuk
Gold $$ Contributor
lynn,
I'll mess with it some this week if I get time. Got to get some stuff squared away for a match this weekend... trying to organize it *and* shoot in it *and* get a gun/load dialed in for the wife. Fun, fun, fun. Don't know how much time I'll have to spend on the 6mm BR.
I don't mean to sound pig-headed,well, not any more so than normal), but I've never yet managed to get a gun to shoot consistently well w/ the bullets jammed... not my .223's, not my .308's, not my 6.5-08, and not the 6mm BR. Well, the 6.5-08 shot pretty well w/ one load slightly 'jammed' but it was a PITA to keep it there w/ the throat on the move. Maybe I'm doing something wrong here. I normally size the cases so I have 2-3 thou of neck tension,more like 2), and when I seat into the lands, I mean beyond the point where a bullet makes very firm contact,i.e. won't move anymore w/o a serious effort) in a SP dummy cartridge. Usually have to plunk the bullet loose out of the lands. Seating in *further* than that hasn't netted me much in the way of good results so far, which is why I'm kind of hesitant to go forward. If you can point out what I'm doing wrong in terms of seating into the lands so that maybe it works this time, I'd be very appreciative.
Thanks,
Monte
I'll mess with it some this week if I get time. Got to get some stuff squared away for a match this weekend... trying to organize it *and* shoot in it *and* get a gun/load dialed in for the wife. Fun, fun, fun. Don't know how much time I'll have to spend on the 6mm BR.
I don't mean to sound pig-headed,well, not any more so than normal), but I've never yet managed to get a gun to shoot consistently well w/ the bullets jammed... not my .223's, not my .308's, not my 6.5-08, and not the 6mm BR. Well, the 6.5-08 shot pretty well w/ one load slightly 'jammed' but it was a PITA to keep it there w/ the throat on the move. Maybe I'm doing something wrong here. I normally size the cases so I have 2-3 thou of neck tension,more like 2), and when I seat into the lands, I mean beyond the point where a bullet makes very firm contact,i.e. won't move anymore w/o a serious effort) in a SP dummy cartridge. Usually have to plunk the bullet loose out of the lands. Seating in *further* than that hasn't netted me much in the way of good results so far, which is why I'm kind of hesitant to go forward. If you can point out what I'm doing wrong in terms of seating into the lands so that maybe it works this time, I'd be very appreciative.
Thanks,
Monte
Monte:
That point where the bullet won't move without a serious push is what I call "hard into" the lands. I have found as you have that seating there can lead to inconsistent results. My tests with a PressureTrace instrument shows significant pressure variations, with large spikes under this condition. Velocity, ES, and SD show this as well. My theory is that it takes a large amount of pressure to overcome the static friction in this condition, and this friction load impact on the propellant burn rate can be all over the map, depending on the bullet particulars and the exact ignition characteristics.
If you seat back from this point, even by as little as 0.005", these pressure variations go away, and everything gets more consistent. Again, this was verified using the PT instrument. I believe this is due to the fact that the bullet is moving when it hits this "hard in" point, and the friction is now in the dynamic state, and therefore takes less force to keep moving. This apparently has beneficial impacts on the propellant burn.
I also believe that the primary point of loading into the lands is to ensure that the bullet engraves as straight as possible. For the MatchKings, and a 1.5 degree throat, I can see land contact for almost 0.020" before "hard in", so even 5 thou back from hard in will keep things lined up. Precision Shooting has published part one of a two part article on this subject of bullet engraving and throat angle optimization.
I have been shooting moly in my 6.5-284 for the singular reason that it appears to help,based on PressureTrace and chronograph measurements) the pressure variations. The 6 Dasher has not been tried with moly, but that is coming soon.
My loads are all starting at 0.010" back from "hard in", as I don't want to hit the point of having pressure problems, and want the bullet to be supported by the lands. Seems to work for me...
I'll have my MAK tubegun in 260AI next weekend...
That point where the bullet won't move without a serious push is what I call "hard into" the lands. I have found as you have that seating there can lead to inconsistent results. My tests with a PressureTrace instrument shows significant pressure variations, with large spikes under this condition. Velocity, ES, and SD show this as well. My theory is that it takes a large amount of pressure to overcome the static friction in this condition, and this friction load impact on the propellant burn rate can be all over the map, depending on the bullet particulars and the exact ignition characteristics.
If you seat back from this point, even by as little as 0.005", these pressure variations go away, and everything gets more consistent. Again, this was verified using the PT instrument. I believe this is due to the fact that the bullet is moving when it hits this "hard in" point, and the friction is now in the dynamic state, and therefore takes less force to keep moving. This apparently has beneficial impacts on the propellant burn.
I also believe that the primary point of loading into the lands is to ensure that the bullet engraves as straight as possible. For the MatchKings, and a 1.5 degree throat, I can see land contact for almost 0.020" before "hard in", so even 5 thou back from hard in will keep things lined up. Precision Shooting has published part one of a two part article on this subject of bullet engraving and throat angle optimization.
I have been shooting moly in my 6.5-284 for the singular reason that it appears to help,based on PressureTrace and chronograph measurements) the pressure variations. The 6 Dasher has not been tried with moly, but that is coming soon.
My loads are all starting at 0.010" back from "hard in", as I don't want to hit the point of having pressure problems, and want the bullet to be supported by the lands. Seems to work for me...
I'll have my MAK tubegun in 260AI next weekend...
I was having vertical problems in my 30BR till another shooter told me to jam them into the lands .020" so i did and it worked then someone else said be care full if you have to extract a loaded round it could pull the projectile but it didn`t as i checked.
I was loading and still am with .002" neck tension and when chambering it actually was pushing the projectile back about .005" consistently so i reset my seater so they were .015" into the lands and yes you could just make out where they were contacting the lands accuracy was good and bolt closure was good you just feel it take the pressure as the bolt cams over. Works for me haven't tried it in any other rifles as yet my 6mmPPC Sako wouldn`t have much projectile left in the case if i did that i expect as i think it has a fairly long throat. Usually seat it with the projectile just above the neck shoulder area.
I was loading and still am with .002" neck tension and when chambering it actually was pushing the projectile back about .005" consistently so i reset my seater so they were .015" into the lands and yes you could just make out where they were contacting the lands accuracy was good and bolt closure was good you just feel it take the pressure as the bolt cams over. Works for me haven't tried it in any other rifles as yet my 6mmPPC Sako wouldn`t have much projectile left in the case if i did that i expect as i think it has a fairly long throat. Usually seat it with the projectile just above the neck shoulder area.
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