Question. For you guys whose got more experience in reloading than me. I have a remington M7 7mm08. Getting ready to reload for. I bought some hornady SST 139 grain bullets and some 140 grain NBT. I want to know if 1 grain different between the two bullets really make a difference in the powder charge. I know that the books say YES! but has anyone used say, said powder charge like 4064 powder charge for the 140 nbt for the sst 139. I had to ask. I understand that 1/10 of a grain can make a Bev difference in accuracy. So please don't. Judge my question as ignorant. Sometimes you just have to be schooled. Thank you I welcome all replies.
Does 1 grain make a difference?
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I think the thickness of the bullet jacket, hardness of jacket, and the hardness of the core have more an influence towards increasing/decreasing pressure than one grain difference in bullet weight. This has to do with how much force it takes to swage the bullet through the throat and then into the rifling. Of course, knowing the jacket thickness, and hardness of either the core or jacket is something you can't investigate with home tools.
In terms of accuracy, I believe that location of the center of gravity has a much greater affect on accuracy than slight weight differences. And then, just how good of a shot are you and is your rifle a bench rest rifle? If your weapon requires you to hold it, but the butt in your shoulder, and use your hand to pull the trigger, than sight alignment, stock weld, and trigger pull errors are magnitudes greater than tiny weight or charge differences. The in print press is all about equipment, emphasizing that such mundane things as practice are unimportant to shooting compared with expensive equipment and gadgets. I don't know if any bowls anymore, but the most perfect, round bowling ball will go right into the gutter, just as a bad ball, if you don't know how to roll it at the pins.
I have shot excellent scores with thrown charges of IMR 4895, short grained stick powders that throw about plus or minus 1/2. I tested thrown IMR 4064 in a 30-06 and that shot well, that powder is probably a plus or minus a grain.
Barrels tightness makes a huge impact on pressures. My Douglas barrels and Wilson barrels in 223, I had to cut loads by 1.5 grains to avoid blown primers in a Kreiger barrel.
There are differences in pressures between bullets, my suggestion is to start with midrange loads and see how they do. Don't try max with new bullets, and, the more you shoot them, don't be surprised if you find that you need to reduce the loads later.
Bullet weight? If the bullets are both cup and core bullets 1 grain apart, probably not. If they are dissimilar, such as a standard cup and core vs a solid, it can indeed.
Powder charge weight? If .1 grain makes a big difference, like say 47.0 shoots like crap, 47.1 shoot lights out, and 47.2 shoot like crap, it's not a good load, even if 47.1 really shoots well. A good load will shoot over a wider spread.
Powder charge weight? If .1 grain makes a big difference, like say 47.0 shoots like crap, 47.1 shoot lights out, and 47.2 shoot like crap, it's not a good load, even if 47.1 really shoots well. A good load will shoot over a wider spread.
ArchAngelCD
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I can't say it any better than Walkalong just did.
Probably not in this case. You see some weird things in load manuals though. I shoot 155 gr bullets in my 308 and most load data for 155's is exactly the same as for 150's for max loads. But some manuals have it different. When looking at loads for my 6.5 CM they show exactly the same max charge weight for 143 and 147 gr bullets, but a lower max charge weight for 140 gr bullets, and all with Hornady ELD bullets. I've found that the same charge weight gives me the same speeds and accuracy with both 140's and 143's. Haven't tried 147's yet
I don't worry about small differences in charge weight with rifle loads. I round up to the closest 1/2 gr for starting loads and go up 1/2 gr at a time after that. If a max load is supposed to be 41.7 gr I will work up to 41.5 and and sometimes even go to 42. I've never found anything less than 1/2 gr increments to be beneficial.
I don't worry about small differences in charge weight with rifle loads. I round up to the closest 1/2 gr for starting loads and go up 1/2 gr at a time after that. If a max load is supposed to be 41.7 gr I will work up to 41.5 and and sometimes even go to 42. I've never found anything less than 1/2 gr increments to be beneficial.
25-20 WCF
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The weight difference? Absolutely not, many bullets of that weight and above can have a one grain difference within the same box. As stated, bullet construction has a greater effect. But that does not mean you can ignore good loading practices like starting several grains below the listed maximum charge weights.
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Varminterror
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I’ll throw this out there: Hornady 50grn V-Max’s can be bought for 223rem in at least 3 different factory loads: Hornady, HSM, and Remington factory ammo all use the 50grn V-max (Remington is psuedonymed as the “accutip”). Point of impact and group size will vary among those 3 factory loads.
Shooting different factory ammo, even with the same bullet, can produce very different outcomes. Shooting different bullets over the same charge weight can produce very different outcomes. Sometimes they all print the same POI, most times they don’t. Why risk it? Shoot both, work up for both, and have knowledge in hand for both.
Shooting different factory ammo, even with the same bullet, can produce very different outcomes. Shooting different bullets over the same charge weight can produce very different outcomes. Sometimes they all print the same POI, most times they don’t. Why risk it? Shoot both, work up for both, and have knowledge in hand for both.
CptnAwesome
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I'm kind of thinking like Varminterror. If it was the same bullet I'd say no it doesn't matter, but it's a totally different bullet from a totally different manufacturer.
I've seen published data for two different bullets of the same weight have different max charges with the same powder so I'd be careful. If you're not flirting around max charge you'd prob be okay. But if your planning on going near just work up for both.
Better safe than sorry/injured/or worse
I've seen published data for two different bullets of the same weight have different max charges with the same powder so I'd be careful. If you're not flirting around max charge you'd prob be okay. But if your planning on going near just work up for both.
Better safe than sorry/injured/or worse
748
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Different lots of cheap bullets can have a one grain difference between the heaviest ones and the lightest ones.
It's more to do with jacket thickness and construction.
It's more to do with jacket thickness and construction.
stillquietvoice
Contributing Member
I asked the same question you did several years ago. The information, s different from, that I received is that the bullets have different jacket thicknesses different ogive, different boat tail angle and bearing surface. So that 1 grain weight difference changes pressures a great deal. More than the 1 grain of weight
It may not matter, but if different bullet from a different manufacturer I would do separate workup for each. A good load could be somewhere close in charge weight, but depending of shape, bearing surface and many other things it could be quite different.
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Varminterror
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Even with the same bullet, different loads will yield different results. Shouldn’t be surprising. Fiocchi, Underwood, HSM, Hornady, and Remington all load that same 50 vmax. All of them print different POI’s and different group sizes at 100yrds.
In this case, we’re talking about different bullets, potentially over the same charge. A single grain difference in weight might not seem like much, but we’re not talking about 1 grain difference between two bullets in the same lot. We’re talking about different Ogive profiles, different jacket thicknesses and alloy hardness, different base design, different core alloy and positions, different tip designs, different boattail profile, different cannelures, different internal jacket lock rings... The 139 SST is actually 20 thousandths longer than the 140 NBT, and NBT’s have a much thicker base.
At best - MAYBE they both shoot well and have POI’s close enough together to use common zero on your rifle for hunting, but it’s pretty doubtful you’ll be able to consider the two interchangeable for reloading and shooting.
In this case, we’re talking about different bullets, potentially over the same charge. A single grain difference in weight might not seem like much, but we’re not talking about 1 grain difference between two bullets in the same lot. We’re talking about different Ogive profiles, different jacket thicknesses and alloy hardness, different base design, different core alloy and positions, different tip designs, different boattail profile, different cannelures, different internal jacket lock rings... The 139 SST is actually 20 thousandths longer than the 140 NBT, and NBT’s have a much thicker base.
At best - MAYBE they both shoot well and have POI’s close enough together to use common zero on your rifle for hunting, but it’s pretty doubtful you’ll be able to consider the two interchangeable for reloading and shooting.
FROGO207
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I have found even the different compositions of the gliding metal used in the jackets can make a difference as well. Also boat tail and flat base of the same weight will be different sometimes. Often I cannot shoot well enough anymore to detect it though but others can with my reloads. I always work up the load with each type/brand/weight bullet even though it takes more time and cost. A couple times I have found a particular bullet and barrel combo would not shoot better than a shotgun pattern but other bullets were quite accurate. You never know when you start.
Thanks for the advice. I guess I should have said it like this. I have a remington model 7 20" barrel in 7mm08
Im getting ready to load for. I have the 140gr NBT and the Hornady SST 139gr bullets. Can I use the same powder charges for either bullet. Do you think I could load the 140gr NBT with the charge the 139gr SST calls for and vice versa. ?
Im getting ready to load for. I have the 140gr NBT and the Hornady SST 139gr bullets. Can I use the same powder charges for either bullet. Do you think I could load the 140gr NBT with the charge the 139gr SST calls for and vice versa. ?
Jim Watson
Member
Well, Hodgdon makes a 2 grain difference in maximum H4895 between 139 Hdy and 140 Swift.
But is that because of the weight difference, or something else?
stillquietvoice
Contributing Member
2 years ago I was at my wife's sisters place shooting with family. It was hot 100 in the shade. I had 2 loads with me 1 139 sst 48.0 Max charge of imr 4350 and a 140 nbt Max charge of 46.5 gr imr 4350. The 139 loads fired fine with no problems. The 140's gave pressure signs, flat primers, hard extraction, and ejector marks. From experience with my rifle is say no, but you may have different results with your gun. Shooting the same loads at 80 degrees or less there is no issue so it could have been just the temperature. Work up loads slow.
^Yep^. Many times questions are asked just for info purposes and not intended for use, but, for a new reloader changing bullets would be a good reason to start a new load work up...
sage5907
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Where one grain can make a real difference is when you are at or going past the maximum recommended powder charge. For example, if the recommended maximum powder charge is 57 grains and when you get to 57 grains you begin to see flattened primers and a big expansion in the rear portion of the case it is foolish to go further, and would be advisable to back off at least two grains. If you would then go to 58 grains the problems would get worse quickly and if you went to 59 grains you could get blown primers. Some powders are quicker to show pressure signs than others and one powder I remember is IMR 4895 and with that powder one grain near the maximum charge can make a big difference. Slow burning powders are more forgiving.
I have spoken to hodgdon about the swift loads, and they promised the difference in max loads from say a 140 swift to a 139 sst IS due to the Swifts harder bullet construction and higher pressures, NOT because of the weight change.
You can grab the 139 load DATA and work up a load for both bullets, but do not necessarily expect the same results from each one, test both out and THEN decide if xx.x gr will shoot good for both bullets or if (due to different manufacturer and profiles etc) the nbt likes the xx.x and the sst likes the xy.y. For what it's worth, I have a few rifles that have allowed me to swap an nbt for an sst with no visible change in accuracy BUT I tested that thoroughly before taking them to the field!
Yep.
Keep in mind that with hunting Bullets if you weigh a handful of them out of the same box you’ll probably find a grain of difference in weight. You don’t have to change your load for that.
I think hardness is a factor but bearing surface is just as much of a factor. A long pointed bullet va a short fat bullet of the same weight will have way different max. Just a lot more friction on the short fat bullet.
I think hardness is a factor but bearing surface is just as much of a factor. A long pointed bullet va a short fat bullet of the same weight will have way different max. Just a lot more friction on the short fat bullet.
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