What happens to velocity with HBN coated bullets?
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Re: What happens to velocity with HBN coated bullets?
Lubricvation of the bullet (moly hbn), causes pressures to go down and the lack of pressure causes bullet MV to go down. The loss of bullet MV can be compensated with more powder because the peak pressure has gone down.
Lubricvation of the bullet (moly hbn), causes pressures to go down and the lack of pressure causes bullet MV to go down. The loss of bullet MV can be compensated with more powder because the peak pressure has gone down.
Re: What happens to velocity with HBN coated bullets?
It sounds bass-ackwards but Mitch is right. The bullet is easier to push down the barrel so less pressure builds up behind it before it exits the muzzle. Less pressure = lower MV.
The effect is much greater on pressure than on velocity, which means if you add powder to get back to the original pressure, the MV will be higher than that of the original naked bullet load.
It sounds bass-ackwards but Mitch is right. The bullet is easier to push down the barrel so less pressure builds up behind it before it exits the muzzle. Less pressure = lower MV.
The effect is much greater on pressure than on velocity, which means if you add powder to get back to the original pressure, the MV will be higher than that of the original naked bullet load.
Re: What happens to velocity with HBN coated bullets?
Anyone know if pressure goes back up the same level if you accomodate more powder to reach a higher speed, say the speed you were achieving BEFORE you used hbn?
Anyone know if pressure goes back up the same level if you accomodate more powder to reach a higher speed, say the speed you were achieving BEFORE you used hbn?
Re: What happens to velocity with HBN coated bullets?
Thanks Guys. That would explain why the velocity was lower with the same charge. So, I should work up a new load after switching to the HBN coated DTAC's?
Thanks. Anything else I should know abut using em?
Thanks Guys. That would explain why the velocity was lower with the same charge. So, I should work up a new load after switching to the HBN coated DTAC's?
Thanks. Anything else I should know abut using em?
Re: What happens to velocity with HBN coated bullets?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: vman</div><div class="ubbcode-body">Anyone know if pressure goes back up the same level if you accomodate more powder to reach a higher speed, say the speed you were achieving BEFORE you used hbn? </div></div>
All that's happening is you're reducing the friction between bullet and bore, which means it takes less effort to drive it down the barrel. As a rule of thumb, if you bump up the charge enough to return Pmax to where it was for your nekkid bullet, you will have a higher MV. It's entirely possible to reach MVs safely with coated bullets that would have produced unsafe pressures with nekkid bullets.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: vman</div><div class="ubbcode-body">Anyone know if pressure goes back up the same level if you accomodate more powder to reach a higher speed, say the speed you were achieving BEFORE you used hbn? </div></div>
All that's happening is you're reducing the friction between bullet and bore, which means it takes less effort to drive it down the barrel. As a rule of thumb, if you bump up the charge enough to return Pmax to where it was for your nekkid bullet, you will have a higher MV. It's entirely possible to reach MVs safely with coated bullets that would have produced unsafe pressures with nekkid bullets.
Re: What happens to velocity with HBN coated bullets?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: WSM 650 AM Radio</div><div class="ubbcode-body">Thanks Guys. That would explain why the velocity was lower with the same charge. So, I should work up a new load after switching to the HBN coated DTAC's?
Thanks. Anything else I should know abut using em?
</div></div>
According to Quick-Load's predictions, a coated bullet produces 2000-3000 less psi. In my experience, they need their own load work-up if you expect them to be as accurate as your nekkid bullet loads.
It's inevitable -- even desirable -- that some of the coating from the bullets will rub off onto the bare bore until the bore itself gets slick enough that no more will rub off. MV and accuracy will not stabilize until this "conditioning" is complete. You can accelerate the "conditioning" process by treating the freshly-cleaned bore before shooting. You can use either a solution of your powder in high-purity (90-91%) rubbing alcohol or Lock-Ease (the liquid, not the aerosol). The alcohol evaporates and leaves the powder clinging to the bore. Lock-Ease is graphite powder in a petroleum-based solution. You can leave it in the bore indefinitely without any harm. When I shot WS2-coated bullets, Lock-Ease seemed to work faster. With hBN, the hBN/alky mix seems to work better. But that could just be me.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: WSM 650 AM Radio</div><div class="ubbcode-body">Thanks Guys. That would explain why the velocity was lower with the same charge. So, I should work up a new load after switching to the HBN coated DTAC's?
Thanks. Anything else I should know abut using em?
</div></div>
According to Quick-Load's predictions, a coated bullet produces 2000-3000 less psi. In my experience, they need their own load work-up if you expect them to be as accurate as your nekkid bullet loads.
It's inevitable -- even desirable -- that some of the coating from the bullets will rub off onto the bare bore until the bore itself gets slick enough that no more will rub off. MV and accuracy will not stabilize until this "conditioning" is complete. You can accelerate the "conditioning" process by treating the freshly-cleaned bore before shooting. You can use either a solution of your powder in high-purity (90-91%) rubbing alcohol or Lock-Ease (the liquid, not the aerosol). The alcohol evaporates and leaves the powder clinging to the bore. Lock-Ease is graphite powder in a petroleum-based solution. You can leave it in the bore indefinitely without any harm. When I shot WS2-coated bullets, Lock-Ease seemed to work faster. With hBN, the hBN/alky mix seems to work better. But that could just be me.
Re: What happens to velocity with HBN coated bullets?
Here was my findings when I coated bullets with hBN. I took my XTC load 123gr SMK 38.0gr N150 in Remington brass and then coated the bullets. When I chronoed the coated bullets to the non-coated bullets I didn't notice any difference. Which I thought was strange cause it should have gone slower being identical charges.
The last year when I was loading I decided to switch brass as the REmington brass was soft and primer pockets were opening up so I went to RA-60 for my 123's and LC LR for my 142's. When I went to seat the bullets the redding seading die was deforming the bullets and they were noticably harder to seat, at first I thought must be the brass. A month ago I was doing my reloading for the season and the same thing was happening again and I thought it was my die took it apart everything looked good, so then I seated a naked bullet and it slid in and there was no deformation ring. This was strange as if the hBN was increasing the friction. I thought back to this past spring was shooting a 2x1000 at Ft. Knox a load that worked great in my .280 remington 62.25gr of H1000 with naked 175's the previous seaon was giving my preasure issues with coated 175's.
Now I'm not saying hBN increased the pressure but the seating issue sure got me thinking, needless to say I'm not shooting hBN coated bullets again till I can do some more testing as I never noticed a velocity decrease and if it actually is increasing pressure like I've noticed I don't want to mess with it.
Here was my findings when I coated bullets with hBN. I took my XTC load 123gr SMK 38.0gr N150 in Remington brass and then coated the bullets. When I chronoed the coated bullets to the non-coated bullets I didn't notice any difference. Which I thought was strange cause it should have gone slower being identical charges.
The last year when I was loading I decided to switch brass as the REmington brass was soft and primer pockets were opening up so I went to RA-60 for my 123's and LC LR for my 142's. When I went to seat the bullets the redding seading die was deforming the bullets and they were noticably harder to seat, at first I thought must be the brass. A month ago I was doing my reloading for the season and the same thing was happening again and I thought it was my die took it apart everything looked good, so then I seated a naked bullet and it slid in and there was no deformation ring. This was strange as if the hBN was increasing the friction. I thought back to this past spring was shooting a 2x1000 at Ft. Knox a load that worked great in my .280 remington 62.25gr of H1000 with naked 175's the previous seaon was giving my preasure issues with coated 175's.
Now I'm not saying hBN increased the pressure but the seating issue sure got me thinking, needless to say I'm not shooting hBN coated bullets again till I can do some more testing as I never noticed a velocity decrease and if it actually is increasing pressure like I've noticed I don't want to mess with it.
Re: What happens to velocity with HBN coated bullets?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: WSM 650 AM Radio</div><div class="ubbcode-body">Great info, thank you. I'm working up new loads with HBN coated now. They sure seam to shoot the same point of Aim, cold bore, etc. </div></div>
It does tend to reduce the CBS's shift in POI. That's one of my primary reasons for using it.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: WSM 650 AM Radio</div><div class="ubbcode-body">Great info, thank you. I'm working up new loads with HBN coated now. They sure seam to shoot the same point of Aim, cold bore, etc. </div></div>
It does tend to reduce the CBS's shift in POI. That's one of my primary reasons for using it.
