Differing data - 7.62x39 loads

Weekend Gunslingers

Weekend Gunslingers

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Hi folks

Wondering if anyone knows how this works. The Accurate 1680 data from the powder manufacturer lists the following min/max for the 123gr Hornady projectile: 24.6 to 27.3

The Hornady reloading data app on the other hand lists the min 20.1 and max 23.9 for the same powder

Which one is correct and why the discrepancy?

Thanks for you input
 
Each of those sources of data would "work" in the particular rifle it was tested with. The chambers and bore dimensions of most rifles, and the 7.62x39 in particular, can vary quite a lot. So you have come across a classic situation in which a chronograph is your best tool to sort out the discrepancies. You should start with a starting load, let's say 23 grains in this case, increasing charges by 1/2 grain at a time and stop when your velocity has reached the published maximum, not when the "maximum" powder charge has been reached. Velocity at maximum is going to equal pressure at maximum, with the given bullet and powder.
You should also be aware that the bullets made by Hornady can be .308" diameter and .310" diameter depending on the model. Match bullet to your bore size. Going down in bullet size is normally safe but inaccurate, going "up" in bullet size ( putting an oversize bullet down a tight bore) is likely to increase pressures.
 
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Longwalker said:
Each of those sources of data would "work" in the particular rifle it was tested with. The chambers and bore dimensions of most rifles, and the 7.62x39 in particular, can vary quite a lot. So you have come across a classic situation in which a chronograph is your best tool to sort out the discrepancies. You should start with a starting load, let's say 23 grains in this case, increasing charges by 1/2 grain at a time and stop when your velocity has reached the published maximum, not when the "maximum" powder charge has been reached. Velocity at maximum is going to equal pressure at maximum, with the given bullet and powder.
You should also be aware that the bullets made by Hornady can be .308" diameter and .310" diameter depending on the model. Match bullet to your bore size. Going down in bullet size is normally safe but inaccurate, going "up" in bullet size ( putting an oversize bullet down a tight bore) is likely to increase pressures.
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Sound advice. Thanks. Looks like I am buying a chronograph soon :)
 
Hornady data is often very conservative.

For reference, my notes said 26.6 gr AA1680 behind Hornady .310 123gr V-max seated to 2.190" produces 2250 fps when fired from my CZ527 carbine. No pressure sign, shoots good out to 400m. I consider this to be on the slow side hence switched to CFE bLK. Again, work up your load for your rifle.
 
diegocn said:
Hornady data is often very conservative.

For reference, my notes said 26.6 gr AA1680 behind Hornady .310 123gr V-max seated to 2.190" produces 2250 fps when fired from my CZ527 carbine. No pressure sign, shoots good out to 400m. I consider this to be on the slow side hence switched to CFE bLK. Again, work up your load for your rifle.
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Nice I have some CFE BLK. Thanks!
 
Weekend Gunslingers said:
Nice I have some CFE BLK. Thanks!
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CFE BLK is a great powder for bolt action rifles, chambered for the 7.62x39.

When you start getting enough in the case to start seeing pressure signs, accuracy can become erratic.

AA1680 is OK, but I prefer 30.0 grns of REL7 which I get 2600fps out of my Howa 1500 sa and it's accurate with 123grn SST IL bullets.

The load I use is slightly compressed, over CCI 250 magnum primers.

The AA1680 load I developed gives just over 2500fps with the same bullets and primers. It's just not as accurate

I also load 150 grain Speer Spire Point bullets over 25.5 grns of REL7 for appx 2400fps and it's accurate out of my rifle.

The CFE BLACK load I used was 31.0 grains over CCI250 primers for 2600fps, but it wasn't nearly as accurate as the above load of REL7.

The CFE BLACK load was 25.7 grains over CC250 primers, for 2200fps with the Speer Spire Point bullets.

I played around with H4895 with the 150 grain Speer bullets and velocities were again erratic.
 
bearhunter said:
CFE BLK is a great powder for bolt action rifles, chambered for the 7.62x39.

When you start getting enough in the case to start seeing pressure signs, accuracy can become erratic.

AA1680 is OK, but I prefer 30.0 grns of REL7 which I get 2600fps out of my Howa 1500 sa and it's accurate with 123grn SST IL bullets.

The load I use is slightly compressed, over CCI 250 magnum primers.

The AA1680 load I developed gives just over 2500fps with the same bullets and primers. It's just not as accurate

I also load 150 grain Speer Spire Point bullets over 25.5 grns of REL7 for appx 2400fps and it's accurate out of my rifle.

The CFE BLACK load I used was 31.0 grains over CCI250 primers for 2600fps, but it wasn't nearly as accurate as the above load of REL7.

The CFE BLACK load was 25.7 grains over CC250 primers, for 2200fps with the Speer Spire Point bullets.

I played around with H4895 with the 150 grain Speer bullets and velocities were again erratic.
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Great info thanks. I am still trying to find a consistent accurate load for 123gr projectiles in a semi auto. I have H335, CFE BLK and AA1680. Still working on it :)
 
I use H4198 with the 123gr and H335 with the Sierra .311/150gr SP...........mag primers shrunk groups 50% in a CZ527
 
Weekend Gunslingers said:
Hi folks

Wondering if anyone knows how this works. The Accurate 1680 data from the powder manufacturer lists the following min/max for the 123gr Hornady projectile: 24.6 to 27.3

The Hornady reloading data app on the other hand lists the min 20.1 and max 23.9 for the same powder

Which one is correct and why the discrepancy?

Thanks for you input
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All of those data are all correct for some rifle, some test conditions, and some level of lawyer/liability fear. I wouldn't be shy of using the Accurate data myself but it depends on you and your comfort level.
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If you have no experience with the cartridge/powder in your rifle then start at the lowest data minimum and work up in 1 gr or half grain increments to gain your confidence in your rifle / load combo.
So in this case I would load 1 only at each charge weight: 20gr, 21gr, 22gr, 23gr, 23.5gr, 24gr. Start at the bottom, inspect the fired case after every shot before taking the next. If the fired brass or extraction show pressure, don't fire the remaining cartridges.

Then you know where to start load development because you proved it.
 
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Real solid stuff given above! Several tests at real pressure labs show that "home hand loader" "signs" of pressure are not reliable - at all. Not the "look" of primers, not bolt lift, not "recoil", not case expansion measurements - except for velocity - velocity from same powder and same barrel length always is directly related to pressure. If they got 2,400 fps at 50,000 PSI with powder XYZ in a 20" barrel, the only way you will get more velocity than they did, with those components, is by accepting a higher pressure than they did. At least one, maybe more, articles written about this by John Barsness - his testing was done with his hand loads and his rifles at Western Powder's lab in Myles City, Montana. Some times, in some cartridges, and some of his rifles, the "home grown" signs worked - and some times they did not - he was significantly "over pressure", in some instances, without knowing it. So, he wrote that he now only relies on velocity, to try to stay within "industry" pressure specs. And , for some cartridges and rifles, he does "deliberately" exceed "industry specs" - for various reasons, which he has also written articles about.
 
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OP - I suspect it adds to confusion, but checking more than one set of data is a VERY GOOD THING. I was helping an acquaintance with a cartridge/rifle he had inherited. He "randomly" went on Internet, to Nosler's loading site, and decided to use the data given there for 175 grain bullets in his new-to-him 7mmSTW. Once I got comparing to what is in my books, what he was using was "very" high - even compared to previously published Nosler data. We checked website - they showed identical powders and loads for both 160 grain and 175 grain bullets - so the "random" starting load that he picked from that website, for his 175 grain bullets, was actually a "starting" load for the 160 grain bullets, but exceeded their book published Maximum load for 175 grains. Did not help that he had a custom barrel with unusually tight chamber neck - and was using brass reformed from another cartridge - so his necks were too thick - could not insert a bullet into the fired case - a real collection of "what not to do" examples... Amazing to me that he was able to get the bolt open after firing, but he had repeated at least three times, and fought with that bolt each time.
 
Do note the 31 gr CFE BLK is above hodgdon max load. I use 29.5gr (max load) and get 123gr hornady .310 to 2440 fps from cz527 during winter. Primer is slightly flattened but acceptable.

I've tried several powders for this caliber and found CFE BLK to be one of the top performer both in fps and accuracy. AA1680 is good on fps but not as good accuracy wise. 4198 give low fps around 2100 range. 4895 results in a compressed load.
 
diegocn said:
Do note the 31 gr CFE BLK is above hodgdon max load. I use 29.5gr (max load) and get 123gr hornady .310 to 2440 fps from cz527 during winter. Primer is slightly flattened but acceptable.

I've tried several powders for this caliber and found CFE BLK to be one of the top performer both in fps and accuracy. AA1680 is good on fps but not as good accuracy wise. 4198 give low fps around 2100 range. 4895 results in a compressed load.
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I have tried 29gr CFE with the 123gr projectile in my semi-auto. I had no pressure signs myself (as far as they are effective in telling as stated in a previous post). The accuracy was not stellar though. I may try the 29.5gr as Hodgdon has 29.7 as max for a 125gr projectile. I will be getting a chrono soon to use the velocity as a measure as previously suggested but in the meantime I have to try working off min/max loads.
 
OP - you do not say what rifle you are working with - a semi-auto 7.62x39 sounds like it might be an SKS or similar?? I do not know what you would consider "stellar accuracy" from such a one - if that is what you have?? Do not think you can make a silk purse from a sow's ear - I do not own one, but suspect 4" or 5" at 100 yards might be what they were about??? I think their design parameters was to go bang every time whether frozen solid at 40 below or soaking wet in steamy jungle at plus 40 C - but I do not think "stellar accuracy" was one of their design parameters??
 
Echoing the above post on accuracy expectation.

Hornady steel cased 123gr SST is a very good factory load. I use it to find the accuracy limit of my rifles.

In cz527, hornady sst prints group less than 1.5 moa consistently, while surplus/barnaul prints 2-3 moa. So I know there's room for improvement by reloading.
In (a very well tuned) SKS however, both surplus and hornady sst shoots about 3 moa. Hence I consider that to be the limit of the rifle.
 
Potashminer said:
OP - you do not say what rifle you are working with - a semi-auto 7.62x39 sounds like it might be an SKS or similar?? I do not know what you would consider "stellar accuracy" from such a one - if that is what you have?? Do not think you can make a silk purse from a sow's ear - I do not own one, but suspect 4" or 5" at 100 yards might be what they were about??? I think their design parameters was to go bang every time whether frozen solid at 40 below or soaking wet in steamy jungle at plus 40 C - but I do not think "stellar accuracy" was one of their design parameters??
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I am using an M10X for the load development. Rifle is capable of sub MOA groups as per shooting illustrated's article (I believe they were able to squeeze a 0.7 MOA out of it if memory serves) and I have had about 1.3MOA with some factory ammo. I am hoping for a 1-1.5inch handload in that ball park. Apologies for being unclear before :)

Link to article: https://www.shootingillustrated.com/articles/2019/2/27/range-review-mplusm-industries-m10x/
 
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OP, I wish you very good look with your attempts. I own and have owned a number of hunting rifles - and have taken many dozens head of various big game. Most of my big game centre fire hunting rifles would struggle to do 5 shot sandbag rested groups at 100 yards, of 1.5 inches or less. So that is a really ambitious goal, I think. I have two - a 9.3x62 with 250 Accubonds, and a 338 Win Mag with 225 Accubonds, both bolt actions, that I have done a reasonable amount of tuning on - each of them will do 3 shot groups, from sandbags, under 1" at 100 yards, almost every time I try. But even with them, it is a "not always" deal. Just happens often enough, that I don't do any more fussing with them. For hunting, mostly the cold barrel shot that is the "money maker", and those seem to be dependably "good".

I have just pretty much finished up assembling a CG63 in 6.5x55, and two 7.62 NATO rifles - time to learn how to go longer - so have found a 300 yard shooting place - going to be working with those rifles, at that range. All new for me - do not know if I still have the eyes for the aperture sights on the PALMA style rifle, but will try it. The other two have 12 power scopes, so not too worried about "vision" for those two - at least for now...
 
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