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Alright, I did my first ladder test this weekend. I was really surprised by 3 things. The first was lower than expected velocity, the second was surprisingly consistent accuracy, and lastly the primer strikes looked very light until the last 3 rounds where they began to look normal. I generally follow the reloading manuals pretty closely, but sense the data for the 7x57 is so conservative I am trying to use a common sense approach. This is a tang safety Ruger M77 by the way.
I shot 16 rounds, starting at 40 grains H-4895 under 120 grain TTSX bullet with a COAL of 3.125" This is a little over .15" off of the lands and about .15" longer than the book COAL length. Barnes #3 manual lists a max charge of 44.0 grains under the XBT bullet, but H-4895 is not listed under the 120 grain TSX bullet in the #4 manual for the 7x57. It is listed in the #4 manual with a max load of 43.0 grains for the 7mm-08. So I decided to err on the side of caution and stopped at 43.0 grains and figure with the extra .15" of COAL I should be safe. However I am about 200 fps behind the "book" velocity for the 7mm-08 or the 7x57. Granted my barrel is 20" and their numbers are from a 24" barrel.
Now, I expect to loose some velocity but not 200 fps going from 24" to 20", especially not with a faster powder like H-4895. So I am feeling that it would be safe to try and go up another 1.0 or 1.5 grains, but before I did I wanted to see what other more experienced re-loaders thought.
Sorry if this was long winded, but I wanted to try and get all the pertinent information out there.
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Campfire 'Bwana
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lastly the primer strikes looked very light until the last 3 rounds where they began to look normal When you write "primer strikes" do you really mean the little indentation right at the point where the firing pin pokes the primer?
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I would disassemble the bolt, and clean out any grease inside.
Something is slowing down the firing pin, if you do have light primer strikes.
Edit to add: I would ease up on the rear action screw torque. Leave the front screw torqued properly. You may be bending the receiver.
Last edited by DMB; 08/17/10.
Don Buckbee
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I can try and take pictures after I get home from work. But yes, the indentations from the firing pin were very shallow until the last couple of rounds. I was assuming the pressures were low enough that the firing pin was forcing the primers deeper into the primer pocket, and at the last few rounds the pressure became high enough to keep the primers flush with the case head. But those are all assumptions. The primer pockets do seem pretty deep on my cases. The cases are made by PRVI, that's the only brand I could find.
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Start off with your 7/08 data and then work up from there...
being a bigger case, you can start right at max load for the 7/08..
in my model 70 FW, I just run 44 grains of IMR 4895 with a 140 grain Ballistic tip for an MV of 2800 fps.
In the Ruger Mk 2, I use 40 grains of 3031 across the board..but most common used bullet is the 175 gr RN Hornady... for an MV of 2650 fps.. when the book states the MV should be 2450..
7 x 57 data and velocities are all over the map...so you have to trust your own rifle and a chronograph..
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1. No matter the barrel length, actual velocity will be lower than book speeds more often than not. Lots of reasons but it doesn't matter why, it is what it is.
2. Your case shoulders may be pushed back too far, allowing the pin to drive the cases forward and giving the appearance of light strikes with your light loads. Hotter charges will drive the case heads back against the bolt face and primers will look normal. If so, neck size or back your FL sizer out maybe 1/8th turn (about .009"), or less, and try that.
3. Your decision on the powder charges are reasonable. I would NEVER suggest anyone exceed book limits or what he feels comfortable with. But, that doesn't limit what I do myself, especially for older cartridges where the book makers must accomidate near anchient weapons chambered for them.
4. Your OAL is also appropriate, book values are just starting suggestions, not laws. After you indentify your best shooting power charge, try seating adjustments in maybe 10 thou steps, in and out, to see if you can't tweak the accuracy a bit.
5. 4895 is a good, consistant buring power but it may be a few tads too fast for best speeds even with a light for caliber bullet. I would also want to try some RL-19, H-380 or H-414.
6. I have no idea what loosening your tang screw might do to help with pin strike and velocity questions. ???
Last edited by boomtube; 08/17/10.
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I realize that H-4895 is probably on the fast side, but I have had good luck with it in the past with my .308 so I thought it deserved a shot. And like I said, I am pretty happy with the accuracy. I also have a ladder test set up with 140 TSX/H-4350 and 175 Hornady's and H-4831SC. But the 120/4895 is showing enough promise I may not run those ladders anytime soon. It managed to keep shots 10-16 in a group about 1.25 inches despite over a grain of powder difference between the first and last shot. I think I will set up a ladder from 43 to 44 grains and see how it goes. If the groups open up I will just drop it back down to 42.8 and call it good.
The last 4 shots averaged about 2790 fps, I figure the 120 TTSX at those speeds should do for any deer, bear, or elk in my neck of the woods as I don't plan on trying to push range out past 200 yards anyway. And it's definitely mild on the shoulder!
Last edited by mortre; 08/17/10.
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SAAMI MAP for the 7x57 is 51,000 PSI peak. There is absolutely no reason at all that the cartridge cannot be run at 60,000 PSI in a modern action.
There are very few instances where I'm sanguine about loading over book limits, but this is one of them.
Two grains over a published load that is 51 KPSI or less is a pretty safe bet. You should be able to safely duplicate the actual ballistics of any commercial 7mm-08 cartridge, perhaps plus a little bit.
I tend toward heavier bullets, and have no trouble running the 160/162 grainers at 2750 FPS, 56 KPSI, more or less.
Last edited by denton; 08/17/10.
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2. Your case shoulders may be pushed back too far, allowing the pin to drive the cases forward and giving the appearance of light strikes with your light loads. Hotter charges will drive the case heads back against the bolt face and primers will look normal. If so, neck size or back your FL sizer out maybe 1/8th turn (about .009"), or less, and try that.
Bingo.
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Question. If "Hotter charges" are driving the case heads back to give a normal look. Does that give a general vicinity of the pressure levels that the top loads are generating? If so, about what pressure level is it that this starts to happen?
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"..about what pressure level is it that this starts to happen?"
Dunno, I don't have pressure testing gear so it would only be a wild azz guess and your's is as good as mine. But, it would vary significantly depending on the alloy of the case, how smooth or oily the chamber may be from shot to shot. It really doesn't matter, you want to be on the upper side of that range anyway.
Last edited by boomtube; 08/18/10.
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Alright, I did my first ladder test this weekend. I was really surprised by 3 things. The first was lower than expected velocity, the second was surprisingly consistent accuracy, and lastly the primer strikes looked very light until the last 3 rounds where they began to look normal. I generally follow the reloading manuals pretty closely, but sense the data for the 7x57 is so conservative I am trying to use a common sense approach. This is a tang safety Ruger M77 by the way.
I shot 16 rounds, starting at 40 grains H-4895 under 120 grain TTSX bullet with a COAL of 3.125" This is a little over .15" off of the lands and about .15" longer than the book COAL length. Barnes #3 manual lists a max charge of 44.0 grains under the XBT bullet, but H-4895 is not listed under the 120 grain TSX bullet in the #4 manual for the 7x57. It is listed in the #4 manual with a max load of 43.0 grains for the 7mm-08. So I decided to err on the side of caution and stopped at 43.0 grains and figure with the extra .15" of COAL I should be safe. However I am about 200 fps behind the "book" velocity for the 7mm-08 or the 7x57. Granted my barrel is 20" and their numbers are from a 24" barrel.
Now, I expect to loose some velocity but not 200 fps going from 24" to 20", especially not with a faster powder like H-4895. So I am feeling that it would be safe to try and go up another 1.0 or 1.5 grains, but before I did I wanted to see what other more experienced re-loaders thought.
Sorry if this was long winded, but I wanted to try and get all the pertinent information out there. I load my Remington 700 7x57 with 49 grains of H4350 under a 140 Nosler Partition for a velocity of 2835 fps out of a 22 inch barrel, this was safe in my rifle. Going to a heavier bullet with a bit heavier powder charge should clear up the low velocity problem.
Last edited by 303carbine; 08/26/10.
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Yep..I would agree with that...
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