reynolds357
New member
Bart, seating bullets "out a ways" actually lowers pressure until you get to a very small area just before the lands. Longer=Lower until just before the rifling and then it =higher. Clear as mud?
Stuck at low velo for .308
- Thread starter nik f.
- Start date
Jim Watson
New member
I load .308 with 155 Scenars and 175 Sierras or Bergers with Varget at one grain below the Lyman maximum for the particular bullet weight. This is substantially more than what Sierra stops at. I get "pressure signs" at Lyman's maximum. I am probably somewhat overloading the round only one grain below, but accuracy is good and brass life is ok.
Sierra data is worth considering, though.
I could not load 90 grain .223 Sierras more than what Sierra said, they would fail in flight before I could get them supersonic at 1000 yards. So I changed to JLK bullets which will stand the gaff.
I am not a good enough loader and shooter to tell a difference in extruded powders; Varget, 4064, and Re15 all shoot the same as far as I can tell. Any of them are better than AA2520 or Win 760 in MY rifles. A pity, I really like the way the ball process powders measure so smoothly and accurately.
My .22-250 just loves H414 and Win 760, though.
Sierra data is worth considering, though.
I could not load 90 grain .223 Sierras more than what Sierra said, they would fail in flight before I could get them supersonic at 1000 yards. So I changed to JLK bullets which will stand the gaff.
I am not a good enough loader and shooter to tell a difference in extruded powders; Varget, 4064, and Re15 all shoot the same as far as I can tell. Any of them are better than AA2520 or Win 760 in MY rifles. A pity, I really like the way the ball process powders measure so smoothly and accurately.
My .22-250 just loves H414 and Win 760, though.
pbcaster45
New member
I too love the way ball powders meter, but I won't use them in my hunting rifles. Ball powder is okay when its warm but during the the cold winter months (when I'm hunting whitetails) I don't trust any to maintain velocity. During the fall and summer I do like to use Accurate 2230-C for feral hogs (in my .338 Federal with Federal 215 Primers) - but that's it.
@Bart B. - Reading your post I am pretty sure I have conflated barrel whip and harmonic distortion. It does make more sense to me that the position of the muzzle in its whip trajectory will affect the POI to a greater degree than the shockwave theory.
So my question to you, please forgive me if I missed your explanation the first time, is what variables do you think will most affect the bullet exiting the muzzle consistently?
I see you have some favorite powders, hopefully I can pick some up soon without having to set up camp at Cabela's loading dock.
@taylorce1 - So you're saying the problem exists within the target acquisition/fire control system?
I can accept that. Just means that I need more practice, "Honey Talorce1 says I have to go to the range on Sunday too!"
Seriously though, I will definitely agree that my twitchiness could be at fault. Mostly though I was worried about the fact that at 100yds my groups are around 1/2", 200yds opens to a little over 1", but 300yds jumps to almost 3 1/2" at times.
So my question to you, please forgive me if I missed your explanation the first time, is what variables do you think will most affect the bullet exiting the muzzle consistently?
I see you have some favorite powders, hopefully I can pick some up soon without having to set up camp at Cabela's loading dock.
@taylorce1 - So you're saying the problem exists within the target acquisition/fire control system?
I can accept that. Just means that I need more practice, "Honey Talorce1 says I have to go to the range on Sunday too!"Seriously though, I will definitely agree that my twitchiness could be at fault. Mostly though I was worried about the fact that at 100yds my groups are around 1/2", 200yds opens to a little over 1", but 300yds jumps to almost 3 1/2" at times.
nik asks me:
Each one has its own resonant frequency that's typically under 100 hz (cycles per second). The 3rd or 4th harmonic (3 or 4 times the resonant frequency) is typically what causes the muzzle axis to change the most that effects the angle the bullet leaves. For example:
http://www.varmintal.com/atune.htm
And this article from way back in 1901, some 112 years ago:
http://archive.org/details/philtrans05900167
The only way to keep it repeatable is to have the barrel totally free from contact with anything except for the receiver it's screwed into. Which is why the most accurate rifles in the world all have totally free floating barrels; no contact pads between the barrel and the stock fore end whatsoever.
Renolds, I know there's a small null space where the bullet can be that has lower peak pressure when fired than a tiny bit either side. If pressure's too hot where the bullet shoots accurate, oft times cutting back a grain will reduce pressure but not accuracy.
The way the barreled action vibrates. And whatever wiggles, whips, bends or whatever it has have to be the same for every shot fired. Reasonably uniform muzzle velocity helps, too.
Each one has its own resonant frequency that's typically under 100 hz (cycles per second). The 3rd or 4th harmonic (3 or 4 times the resonant frequency) is typically what causes the muzzle axis to change the most that effects the angle the bullet leaves. For example:
http://www.varmintal.com/atune.htm
And this article from way back in 1901, some 112 years ago:
http://archive.org/details/philtrans05900167
The only way to keep it repeatable is to have the barrel totally free from contact with anything except for the receiver it's screwed into. Which is why the most accurate rifles in the world all have totally free floating barrels; no contact pads between the barrel and the stock fore end whatsoever.
Renolds, I know there's a small null space where the bullet can be that has lower peak pressure when fired than a tiny bit either side. If pressure's too hot where the bullet shoots accurate, oft times cutting back a grain will reduce pressure but not accuracy.
Bart B.
Don't confuse anyone, we've been over this before http://thefiringline.com/forums/showthread.php?t=505440.
But no matter how much we argue about the reasons that the OCW method works (harmonics, optimal barrel time, etc), the bottom line is that it works and the instructions are easy to follow.
Jimro
Don't confuse anyone, we've been over this before http://thefiringline.com/forums/showthread.php?t=505440.
But no matter how much we argue about the reasons that the OCW method works (harmonics, optimal barrel time, etc), the bottom line is that it works and the instructions are easy to follow.
Jimro
reynolds357
New member
PBCaster, I have not ovserved Ball powder to be that extremely temp sensitive. All powder is temp sensitive and I have never known ball to give any problems when lit with a magnum primer.
Nik's interesting comment:
Bolt that barreled action in a stock such that the receiver fits the stock exactly the same way with the same torque on the stock screws plus having the barrel totally free floated, it'll whip, wiggle, vibrate and shake exactly the same way for each shot fired. If 1000 of identical barreled actions are done this way, they'll all behave the same way. When there's contact between the barrel and stock fore end, depending on where and how much it is plus how it changes by the way the rifle's held, the barreled action will no longer whip, wiggle, vibrate and shake the same way for each shot.
Even if a bunch of rifles have different profile and sizes of barrels but chambered for the same cartridge, they can all shoot to the same excellent level with the same load providing their barrels are all totally free floating and do not touch the stock whatsoever. One exception's the M1 and M14 service rifles; their barrel's held very repeatably by the stock ferrule at the front of the fore end; held the same way for each shot, they are very accurate. That's been proved for decades when the same lot of ammo has to be used by everyone shooting the match.
Every factory barreled action with a given profile barrel and cartridge chambering has the same fundamental or resonant frequency; within a few tenths of a cycle per second anyway for microscopic differences in their dimensions. So, they whip, wiggle, vibrate and shake exactly the same way for each shot fired. The amount they do that will vary with the load used, but for each load it'll be the same. Just like a piano string gently pounded by its hammer or smacked as hard as possible; it's frequency is the same.
Bolt that barreled action in a stock such that the receiver fits the stock exactly the same way with the same torque on the stock screws plus having the barrel totally free floated, it'll whip, wiggle, vibrate and shake exactly the same way for each shot fired. If 1000 of identical barreled actions are done this way, they'll all behave the same way. When there's contact between the barrel and stock fore end, depending on where and how much it is plus how it changes by the way the rifle's held, the barreled action will no longer whip, wiggle, vibrate and shake the same way for each shot.
Even if a bunch of rifles have different profile and sizes of barrels but chambered for the same cartridge, they can all shoot to the same excellent level with the same load providing their barrels are all totally free floating and do not touch the stock whatsoever. One exception's the M1 and M14 service rifles; their barrel's held very repeatably by the stock ferrule at the front of the fore end; held the same way for each shot, they are very accurate. That's been proved for decades when the same lot of ammo has to be used by everyone shooting the match.
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The rule of thumb I learned long ago, and applying to all calibers was to have at least one full caliber of contact between the case neck and the bullet for good neck tension. So for a .308 that would be at least .3"
Normally not an issue with med and heavy bullets, even seating them well out.
There are two general rules in play, one is that most guns will shoot better with the bullets seated to just off touching the lands. But remember its most, and not all. And, how much of a difference it makes becomes important, as well, depending on what it is you are looking for from your gun and load.
The other general rule is that most guns will shoot better (tighter groups) with loads that are below maximum velocities. But again, how much of a difference it makes depends on the individual gun and loads used.
With a precision rig like what you have, and for shooting paper at known ranges, a small difference in the group size could be significant to you, where it would be meaningless to a deer hunter.
One thing I'm wondering, since you are a "paper hunter", is why is top (or upper end) velocity important to you?
Until you get to ranges where the bullet is dropping down through the sound barrier (and resultant turbulence) and other long range concerns, a few hundred fps (while useful in field situations, where it can help compensate for mis-estimation of range) doesn't seem that important to me for range shooting.
When you know the speed, no matter what it is, and you know the range (again, no matter what it is), and the BC of the bullet, drop is a straight calculation, and one you can consistently compensate for. The difference in drop for the same bullet at 2400fps and 2650fps isn't very much, and if you can compensate for one, you can do it for either just as well.
The faster the bullet, the less time it is in the air, so the less wind can have an effect on it. That is true, but again, we are talking very small differences, and again, if you can read the wind that well, and know the proper correction to make for the conditions, making that correction is the same for higher speeds as lower, all that differs is a tiny bit amount of correction.
Your rifle may have more than one "sweet spot", and its worthwhile to try everything until you know where it is or they are. If I had a rifle that would shoot great at 2400fps, and not as well at 2700fps I'd shoot it at 2400fps if accuracy was my primary goal.
@44 AMP - Mostly I am concerned why my rifle seems to be limited to such low velocities where others are fine shooting factory ammo. It is more the mystery of why my pet load goes to 5x the diameter of group with only 3x the change in distance.
Some friends and I are going to set up a more practical course of fire at some private land where we will set up various targets at unknown distances out to 500yds. I would like to have that cushion you talked about so I am not embarrassing myself with missed shots. I'd like to have a hotter load figured out before pride (and possibly wagers) are on the line.
Thanks for the info on the seating depth. Bearing surface seems to make more sense so it looks like I won't be getting anywhere near the lands with any 155gn bullets.
I'm cutting out of work early today to do some prep for the range tomorrow. I think I am going to give the OCW test a try and see if it works for me. *for whatever reason it might.
Some friends and I are going to set up a more practical course of fire at some private land where we will set up various targets at unknown distances out to 500yds. I would like to have that cushion you talked about so I am not embarrassing myself with missed shots. I'd like to have a hotter load figured out before pride (and possibly wagers) are on the line.
Thanks for the info on the seating depth. Bearing surface seems to make more sense so it looks like I won't be getting anywhere near the lands with any 155gn bullets.
I'm cutting out of work early today to do some prep for the range tomorrow. I think I am going to give the OCW test a try and see if it works for me. *for whatever reason it might.
Jim Watson
New member
If you are loading single shot, you don't have to worry about what the magazine will take or how deep the bullet is in the neck. Just seat deep enough that it doesn't come apart from handling if that is what it takes to get you to an accurate jump to the lands.
The Creedmoor shooters were loading paper patched .44-90s about 1/8" in the case mouth.
The Creedmoor shooters were loading paper patched .44-90s about 1/8" in the case mouth.
It is entirely possible to make highly accurate ammo with very little, or even NO part of the bullet in the case. Look at the Schuetzen rifles and such where the bullet is muzzle loaded, with just the case in the breech.
The "at least one caliber" rule is just a general one, and I have known people who will load one half caliber seating depth, if conditions apply. Very small neck to bullet contact makes the ammo more fragile. Fine on the range, but more risky in the field, especially in the smaller calibers.
As long as the bullets don't fall out or become misaligned in the case during normal handling, you can go as shallow as you like, for single loading the chamber (provided you have the room).
Ammo that is going to be fed through a magazine needs to be fairly durable, and in autoloaders, its vital the rounds withstand the forces they get without damage or deformation.
The "at least one caliber" rule is just a general one, and I have known people who will load one half caliber seating depth, if conditions apply. Very small neck to bullet contact makes the ammo more fragile. Fine on the range, but more risky in the field, especially in the smaller calibers.
As long as the bullets don't fall out or become misaligned in the case during normal handling, you can go as shallow as you like, for single loading the chamber (provided you have the room).
Ammo that is going to be fed through a magazine needs to be fairly durable, and in autoloaders, its vital the rounds withstand the forces they get without damage or deformation.
Okay so here are my results for a batch of 4064 behind a 178 grain A-Max bullet. If I am reading this right it appears that my optimal charge weight is somewhere in the range of 44.9 and 45.5 grains of powder. At this point I should pick the 45.2 gr charge and start to play with OAL in .1" increments. Does this seem correct? OAL will have that big an effect on group size?
allaroundhunter
New member
I would start at 45.2 gr and work up to 45.8 gr in .1 gr increments before either started messing with seating depth.
You pulled the low shot on the 45.8 gr group.
You pulled the low shot on the 45.8 gr group.
When the .308 Win. was popular for 200 through 600 yard matches, a standard load of 44 grains of IMR4064 under a Sierra 168 or 43 grains under a Sierra 180 and 42 grains under a Sierra 190. Reduced loads of 41 grains were often used for 168's at 200 and 300 yards. 1/4 MOA accuracy at 200 yards, 1/3 MOA at 300 and often 1/2 MOA at 600 yards. In all sorts of barrels. This is with properly full length sized cases. Neck only sized cases never shot this well consistantly.
I think any charge of IMR4064 over 43 grains under a 178 grain bullet is way to much for best accuracy. It's important to have the pressure curve uniformly shaped. With too much powder in the case, the pressure curve is no longer repeatable and the bullets will leave at different muzzle pointing directions.
If you're holding the rifle against your shoulder when you shoot test groups at 100 yards, it's easy for your own non-repetability of holding the rifle to cause a 1/2 inch or more error in where the rifle points when the bullet leaves.
And just maybe, your barrel may not be capable of shooting smaller groups with any load.
I think any charge of IMR4064 over 43 grains under a 178 grain bullet is way to much for best accuracy. It's important to have the pressure curve uniformly shaped. With too much powder in the case, the pressure curve is no longer repeatable and the bullets will leave at different muzzle pointing directions.
If you're holding the rifle against your shoulder when you shoot test groups at 100 yards, it's easy for your own non-repetability of holding the rifle to cause a 1/2 inch or more error in where the rifle points when the bullet leaves.
And just maybe, your barrel may not be capable of shooting smaller groups with any load.
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So I went to the range on Saturday with a box of Gold Medal Match 175s and 50 rounds based on my OCW findings (55.2g IMR 4064) with varying OALs from 2.81 to 2.90in.
First, the GMM shot great. It was kind of a windy morning but I consistently made sub 1/2 MOA groups with the factory ammo. So at 2,600fps (Federal's claim) it appears that my concern about being stuck at low velocity is disproven.
I then started shooting the handloads and got some interesting results. I shot one from each progressively longer round at each of six targets corresponding to the length selected. (so that no specific group would have the disadvantage of a dirtier barrel. At the end of the testing I had a five round group on each of the ten targets representing each OAL group. There were three acceptable groups but they weren't together on the range of length.
2.81"= POI 2.5" low, 1.5" dia
2.82"= POI 2" low, 1.75" dia
2.83"= POI .25" low, .375" dia
2.84"= POI 2.75" low, 1.375" dia
2.85"= POI 2.5" low, 1.5" dia
2.86"= POI .625 low right, .5" dia
2.87"= POI 2.375" low, 1.875" dia
2.88"= POI 2" low, 2" dia
2.89"= POI .625 low left, .5" dia
2.90"= POI 2.25" low, 1.375" dia
I really didn't have any idea how much difference OAL can make. All groups were shot rested, off a bipod, with rear bag.
So it looks like I should settle on one of the three lengths for seating depth?
First, the GMM shot great. It was kind of a windy morning but I consistently made sub 1/2 MOA groups with the factory ammo. So at 2,600fps (Federal's claim) it appears that my concern about being stuck at low velocity is disproven.
I then started shooting the handloads and got some interesting results. I shot one from each progressively longer round at each of six targets corresponding to the length selected. (so that no specific group would have the disadvantage of a dirtier barrel. At the end of the testing I had a five round group on each of the ten targets representing each OAL group. There were three acceptable groups but they weren't together on the range of length.
2.81"= POI 2.5" low, 1.5" dia
2.82"= POI 2" low, 1.75" dia
2.83"= POI .25" low, .375" dia
2.84"= POI 2.75" low, 1.375" dia
2.85"= POI 2.5" low, 1.5" dia
2.86"= POI .625 low right, .5" dia
2.87"= POI 2.375" low, 1.875" dia
2.88"= POI 2" low, 2" dia
2.89"= POI .625 low left, .5" dia
2.90"= POI 2.25" low, 1.375" dia
I really didn't have any idea how much difference OAL can make. All groups were shot rested, off a bipod, with rear bag.
So it looks like I should settle on one of the three lengths for seating depth?
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DAVID NANCARROW
New member
Wow Nik. Just went to the Hodgdon site and they list a max load for a Sierra 175 SMK at 45.6 gr which is a compressed load?????
Anyhow, Ive had a Remington VS in 308 for several years now, and I have had good accuracy with 168 gr Sierra SMKs under a max book load of Reloder 15. 1/4 moa @ 200 yards when Ive practiced a lot. Rifle is more accurate than I am. I cant say for certain, but RL-15 seems to come into its own with the longer 26 inch barrel length. Velocity is pretty good, but most testing is on a 24 inch barrel so I was hoping and did beat their velocity figures, not by much. I have the same 1:12 twist you have and the rifle came with a H&S precision stock from the factory. Nice setup, that. Best thing I ever did was to buy an inch pound torque wrench for the action screws. Its very repeatable.
If you prefer ball powder over stick, BLC-2 and W748 pretty good in 308.
Anyhow, Ive had a Remington VS in 308 for several years now, and I have had good accuracy with 168 gr Sierra SMKs under a max book load of Reloder 15. 1/4 moa @ 200 yards when Ive practiced a lot. Rifle is more accurate than I am. I cant say for certain, but RL-15 seems to come into its own with the longer 26 inch barrel length. Velocity is pretty good, but most testing is on a 24 inch barrel so I was hoping and did beat their velocity figures, not by much. I have the same 1:12 twist you have and the rifle came with a H&S precision stock from the factory. Nice setup, that. Best thing I ever did was to buy an inch pound torque wrench for the action screws. Its very repeatable.
If you prefer ball powder over stick, BLC-2 and W748 pretty good in 308.
@David N.- Thanks for the info. Unfortunately I haven't seen 168s nor RL-15 in over 6 months.
Interestingly I just ordered a torque driver this weekend. What torque specs are you using for the HS Precision stock? I was talking to a friend with a Savage that he has to really crank on the action screws to get it accurate.
Interestingly I just ordered a torque driver this weekend. What torque specs are you using for the HS Precision stock? I was talking to a friend with a Savage that he has to really crank on the action screws to get it accurate.