coyotezapper
Member
I thought I would give an example of how simple it can be to develop a good consistent load jumping bullets. I will preface this example by saying that if you search the different forums on the internet it is generally recommended to jam, kiss or slightly jump bullets to get best results why developing a load. With a custom rifle with a custom throat, yes this is common but for factory rifles this is hard to do because of the factory throat dimensions. For example, most factory Rem700 rifles have very generous freebore which can be discouraging to some when measuring OAL during load work up. If you were to ask Remington why they do this they would probably say it is for safety purposes and I agree. To often it is the practice of some to ask for load suggestions for a certain cartridge and then think that if it is safe in one rifle it should be safe in mine, right? - WRONG. Different chambers / throats, bbl twists and brass itself can create different pressures. This is why most reloading info by powder manufactures list brass make and primers in their load data and even these recipes can sometimes be problematic. Powder lots can affect this data so be careful when changing lots.
Why is this practice of jamming, kissing or slightly jumping so popular? I think it is because this is what benchrest shooters do, generally. By seating a bullet in to the lands it helps bullet / bore alignment. And we all want to shoot tiny groups like they do. Remember though that they are usually working with custom throated rifles and are very good at working with these custom necks, throats / leades.
Let me make two more points. 1- Concentric loads are the most accurate. If you have the bullet seated out way long just so you can touch the lands, the bearing surface of the bullet may be only touching half the neck and concentricity can suffer. Why is the 6PPC such an accurate cartridge? One reason it has a long neck which makes for a lot of bearing surface contact with bullet. Why is the 7mm RSAUM better than the 7mm WSM? - this is my opinion, because it has a longer neck and allows for more concentric rounds and less throat erosion. 2- pressure = velocity. There are no magic powders. For example, if you load to Hodgdon's listed velocities you will be in the neighborhood of their listed pressures with the only exception being twist rate of rifle. Faster twists create higher pressures earlier than slower twists. Just because you don't see pressure signs do not assume you are ok. I have pressure checked many loads with a Oehler 43 PBL and found some loads 5-8K over pressured with no physical signs on brass. Please be careful.
Off my soapbox and on to the load work up example. Factory Rem 700 22-250 SPS Varmint bedded in a B&C stock, Timney trigger set at 24 oz. BBL is a 1-14" twist factory bbl that was shortened from 26" to 24". No other modifications done to rifle.
BBL was broke in with 20 rounds fired, cleaning to bare steel between each round fired. BBL was coated with two patches of Neolube No. 1 after each cleaning, before next round fired.
Load details: Powder - Varget, Primers - Fed210M, Cases - Winchester, Bullet - Berger 55 FB Target #22410
Standard RCBS dies used for FL sizing. Wilson inline Seater Die with micrometer used for seating bullets. Micrometer seater is very helpful in making exact seating depth changes.
COAL ( Comparator used )with bullet just touching lands - 2.5530" ( 2.5270" OAL base to tip. Remainder of measurements will be with comparator - Base to Ogive including tool )
Bullets seated 2.410" COAL giving good bearing surface contact with case neck - .143" jump.
Powder charges - 3 rounds each charge - with chronographed velocities.
35.4 3466 fps
35.7 3521 fps
36 3531 fps
36.3 3574 fps
36.6 3639 fps
36.9 3654 fps
37.2 3660 fps
37.5 3682 fps
I did not list group size because at this time I am only looking at my velocity curve. I do look at the groups vertical POI from one charge to the next.
I picked 37.2 grs to work with because the velocity increase from 36.9 to 37.2 was only 6 fps indicating a sweet spot / powder node. I then tested 37, 37.1, 37.2 and 37.3 grs verifying I was in a good wide node. ES for these four charges was 17 fps with a SD of 8 fps. 35.7 to 36 grains also showed a powder node but higher ES & SD so I went with the 36.9 to 37.2 window which had lower numbers.
Seating depth test. This was done with the same 37.2 grs Varget. The seating depth test was done with 5 round groups. Here is the results of the seating depth test. Measurements are center to center.
2.410" .740" ( 4 in .335" ) Its wanting to shoot but not quite there
2.405" .815" ( 4 in .435" )
2.400" 1.19" ( 4 in .580" )
2.395" .616" ( 4 in .588" )
2.390" 1.22" ( 4 in .701" 3 in .214" )
2.385" 1.10"
2.380" .500" ( 3 in .047" )Load is now settling in to accuracy node
2.370" .2685"
2.360" .4645"
2.350" .5345"
Groups starting opening up after this. Velocity did increase slightly, because as the bullet is seated deeper velocity will increase due to case capacity change. If you use Quickload you can use this feature by filling an empty case with h20 and then weighing full and empty to determine actual case capacity. You can then change the QL set capacity to your actual capacity and this will help generate a more accurate prediction. There can be quite a difference from one brass manufacturer to the next. Remember this is a factory Remington bbl and the bullets are jumping a mile.
So now I have a good working load. I will seat bullet at 2.380" COAL - longest length with 37.2 grs Varget and will be good to shoot for a quite a while. I will be able to get at least .030" throat erosion before I will need to adjust seating depth, maybe. Sometimes it will just continue to shoot well past this seating depth window. My 6.5 4S has .050" throat erosion and still shoots 1/4 MOA and it only had a seating depth window of .020". I should never have to touch powder charge because the change will be so slight.
The key here is the powder charge. Because of the flat spot in the velocity increase, it gives me a wider window of use. Yes, there is probably a better accuracy node somewhere else but not with the same powder node and I won't have to chase the lands or adjust powder charge at all or as often as when this window is smaller. Now, if I am a tenth of a grain light or heavy on my powder throwing it will not affect anything and same with my seating depth - I will not have to sort bullets or 2 step seat them.
Final Notes. With a COAL length of 2.380" there is .173" Jump. I use this method with all bullets including VLD's. No round robin, no 300 or longer test distances, just 100 yds. SO FAR, if it shoots at 100 yds it will hold its accuracy at longer distances. I have used this method with a 338 Lapua - factory Remington 700, to shoot at 1 mile and it works. I use this method with all of my big game rifles and test them to transonic ranges to verify drops.
THIS IS ONE METHOD. It is not the "ONLY" method but it works for me. Is there better methods, probably but maybe not as simple. I hope this method will help someone who may be just starting handloading.
Why is this practice of jamming, kissing or slightly jumping so popular? I think it is because this is what benchrest shooters do, generally. By seating a bullet in to the lands it helps bullet / bore alignment. And we all want to shoot tiny groups like they do. Remember though that they are usually working with custom throated rifles and are very good at working with these custom necks, throats / leades.
Let me make two more points. 1- Concentric loads are the most accurate. If you have the bullet seated out way long just so you can touch the lands, the bearing surface of the bullet may be only touching half the neck and concentricity can suffer. Why is the 6PPC such an accurate cartridge? One reason it has a long neck which makes for a lot of bearing surface contact with bullet. Why is the 7mm RSAUM better than the 7mm WSM? - this is my opinion, because it has a longer neck and allows for more concentric rounds and less throat erosion. 2- pressure = velocity. There are no magic powders. For example, if you load to Hodgdon's listed velocities you will be in the neighborhood of their listed pressures with the only exception being twist rate of rifle. Faster twists create higher pressures earlier than slower twists. Just because you don't see pressure signs do not assume you are ok. I have pressure checked many loads with a Oehler 43 PBL and found some loads 5-8K over pressured with no physical signs on brass. Please be careful.
Off my soapbox and on to the load work up example. Factory Rem 700 22-250 SPS Varmint bedded in a B&C stock, Timney trigger set at 24 oz. BBL is a 1-14" twist factory bbl that was shortened from 26" to 24". No other modifications done to rifle.
BBL was broke in with 20 rounds fired, cleaning to bare steel between each round fired. BBL was coated with two patches of Neolube No. 1 after each cleaning, before next round fired.
Load details: Powder - Varget, Primers - Fed210M, Cases - Winchester, Bullet - Berger 55 FB Target #22410
Standard RCBS dies used for FL sizing. Wilson inline Seater Die with micrometer used for seating bullets. Micrometer seater is very helpful in making exact seating depth changes.
COAL ( Comparator used )with bullet just touching lands - 2.5530" ( 2.5270" OAL base to tip. Remainder of measurements will be with comparator - Base to Ogive including tool )
Bullets seated 2.410" COAL giving good bearing surface contact with case neck - .143" jump.
Powder charges - 3 rounds each charge - with chronographed velocities.
35.4 3466 fps
35.7 3521 fps
36 3531 fps
36.3 3574 fps
36.6 3639 fps
36.9 3654 fps
37.2 3660 fps
37.5 3682 fps
I did not list group size because at this time I am only looking at my velocity curve. I do look at the groups vertical POI from one charge to the next.
I picked 37.2 grs to work with because the velocity increase from 36.9 to 37.2 was only 6 fps indicating a sweet spot / powder node. I then tested 37, 37.1, 37.2 and 37.3 grs verifying I was in a good wide node. ES for these four charges was 17 fps with a SD of 8 fps. 35.7 to 36 grains also showed a powder node but higher ES & SD so I went with the 36.9 to 37.2 window which had lower numbers.
Seating depth test. This was done with the same 37.2 grs Varget. The seating depth test was done with 5 round groups. Here is the results of the seating depth test. Measurements are center to center.
2.410" .740" ( 4 in .335" ) Its wanting to shoot but not quite there
2.405" .815" ( 4 in .435" )
2.400" 1.19" ( 4 in .580" )
2.395" .616" ( 4 in .588" )
2.390" 1.22" ( 4 in .701" 3 in .214" )
2.385" 1.10"
2.380" .500" ( 3 in .047" )Load is now settling in to accuracy node
2.370" .2685"
2.360" .4645"
2.350" .5345"
Groups starting opening up after this. Velocity did increase slightly, because as the bullet is seated deeper velocity will increase due to case capacity change. If you use Quickload you can use this feature by filling an empty case with h20 and then weighing full and empty to determine actual case capacity. You can then change the QL set capacity to your actual capacity and this will help generate a more accurate prediction. There can be quite a difference from one brass manufacturer to the next. Remember this is a factory Remington bbl and the bullets are jumping a mile.
So now I have a good working load. I will seat bullet at 2.380" COAL - longest length with 37.2 grs Varget and will be good to shoot for a quite a while. I will be able to get at least .030" throat erosion before I will need to adjust seating depth, maybe. Sometimes it will just continue to shoot well past this seating depth window. My 6.5 4S has .050" throat erosion and still shoots 1/4 MOA and it only had a seating depth window of .020". I should never have to touch powder charge because the change will be so slight.
The key here is the powder charge. Because of the flat spot in the velocity increase, it gives me a wider window of use. Yes, there is probably a better accuracy node somewhere else but not with the same powder node and I won't have to chase the lands or adjust powder charge at all or as often as when this window is smaller. Now, if I am a tenth of a grain light or heavy on my powder throwing it will not affect anything and same with my seating depth - I will not have to sort bullets or 2 step seat them.
Final Notes. With a COAL length of 2.380" there is .173" Jump. I use this method with all bullets including VLD's. No round robin, no 300 or longer test distances, just 100 yds. SO FAR, if it shoots at 100 yds it will hold its accuracy at longer distances. I have used this method with a 338 Lapua - factory Remington 700, to shoot at 1 mile and it works. I use this method with all of my big game rifles and test them to transonic ranges to verify drops.
THIS IS ONE METHOD. It is not the "ONLY" method but it works for me. Is there better methods, probably but maybe not as simple. I hope this method will help someone who may be just starting handloading.
