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A beginning for 257 Roberts
Discussion regarding the reloading of ammunition and tuning of loads for accuracy
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PaulS
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PostPosted: Tue Mar 31, 2020 4:16 pm    Post subject: A beginning for 257 Roberts Reply with quote

I finally got to the range to start testing my new brass for signs of excessive pressure.
I am working with a Browning A Bolt that has a 22 inch barrel, 7mm Mauser new brass (PPU) full sized in my 257 RCBS dies. CCI 250 primers and Hodgdon H414 powder.
I started with loads that were just under to just over where I got signs of pressure with my used brass and am looking for signs of pressure while recording velocities and standard deviation in % of muzzle velocity.
Here are the first results:

charge---------SD----------over pressure?---MV
47.8 gr.----SD=0.860%----No pressure----3261
47.7 gr.----SD=0.750%----No pressure----3225
47.6 gr.----SD=0.712%----No pressure----3238
47.5 gr.----SD=0.725%----No pressure----3218

There is a sweet spot load at 47.6 grains that gave an SD of 23 fps or .712% of MV.
The maximum listed load is 50 grains of H414 so I will continue up the scale until I get indications of over pressure. At that point I hope to have at least one and maybe two more sweet spots to choose from.
The velocity surprises me as it is already approaching 25-06 range but it is welcome. I am using an 87 grain TNT bullet that should absolutely destroy a coyote with a decent hit.

I will continue the research as time allows and post updates here.
WARNING: This data cannot be used in any +p cases without a reduction of 10%.
I have also found that there is a lot of variation in case capacities in non-+P brass as well. When using commercial 257 brass start low and work up.

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slimjim
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PostPosted: Wed Apr 01, 2020 3:49 am    Post subject: Re: A beginning for 257 Roberts Reply with quote

Paul, are you doing 3-shot groups? If so, why waste precious resources and barrel life? My practice is to do a single-shot per charge weight in 0.5 grain increments and mark each impact. E.g., 47.5, 48.0, 48.5, 49.0, 49.5, 50.0, and if you don't mind pulling a bullet, 50.5. If 3 in a row group at 1 moa, pick the middle charge weight then do 3- or 5-shot groups around that powder weight to fine-tune you accuracy node. Example below. Note, I use 0.3 grain increments for smaller cases but this can be used for larger cases also, just uses more resources.



77 smk with varget at 200 yards copy.jpg
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Elvis
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PostPosted: Wed Apr 01, 2020 10:46 pm    Post subject: Re: A beginning for 257 Roberts Reply with quote

now ME.......I would be happy with ANY of those that group well...3200fps is honking along.

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PaulS
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PostPosted: Sat Apr 04, 2020 7:10 am    Post subject: Re: A beginning for 257 Roberts Reply with quote

Slim,
I am not a target shooter and shooting the barrel out is not a concern for me. I am just looking for my maximum load at this point. Once I have a maximum load I can work on groups. I want the lowest standard deviation when I develop a load so it is consistent across a wide temperature range and under all hunting conditions. Jumping 3 tenths of a grain I might miss that sweet spot I am looking for. I shoot five shot groups when I start shooting for groups and a typical session will use twenty rounds in 4 groups of each load. This has always worked for me so I use it.

I could skip around but in the end it is more rounds fired or lost opportunities to find the best load. In a hunting rifle I will likely never shoot out the barrel - I never have before and I have rifles that have had a lot of bullets down the bore.

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Paul
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slimjim
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PostPosted: Sat Apr 04, 2020 11:12 am    Post subject: Re: A beginning for 257 Roberts Reply with quote

Paul, it may take 5- or 10-shot groups to determine if a load is good, but I can tell on the 2nd shot if a load is not worth pursuing. Why waste all that time and resources.

I can work up and find my max pressure boundary in 5 shots, one doesn't need to do that task in 5-shot group, 0.1grain increments. In the process of shooting that single-round-per-charge weight ladder, if 3 group within an inch, I know that is where the accuracy node can be found. Then load around that middle charge weight to fine tune. In the example above, I used only 6 rounds to find the performance boundary and accuracy node. I verified with 6 more rounds (two 3-shot groups) the accuracy node ws 0.5 moa. I didn't even have to adjust COAL to refine. Last week, I did the same with a .223 5-shot load ladder for a 70 MKZ with 0.3 grain increments. I loaded the middle weight of the accuracy node and went successfully hunting without a follow-up group to verify.

At the rate you are going, you are going to fire up to 130 rounds during at least 5 range sessions. Your method does work, but ....

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Elvis
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PostPosted: Sat Apr 04, 2020 1:49 pm    Post subject: Re: A beginning for 257 Roberts Reply with quote

Slim...what haapened to your velocity in above picture...
9fps diference between first 2 loads then closer to 50 from there on???

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Elvis
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PostPosted: Sat Apr 04, 2020 1:51 pm    Post subject: Re: A beginning for 257 Roberts Reply with quote

Paul...if you chuck chronicgraph away,and find an accurate load...why bother trying anything else???? if it works why piss around with it further???
but Im simple,or so SWMBO always tells me....

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slimjim
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PostPosted: Sun Apr 05, 2020 3:03 am    Post subject: Re: A beginning for 257 Roberts Reply with quote

Elvis wrote:
Slim...what haapened to your velocity in above picture...
9fps diference between first 2 loads then closer to 50 from there on???

Elvis, there could be several reasons. If the case isn't close to full, velocity deviations can be more common. This is only 1-shot per charge weight, not an average of 3- or 5-shots. The one before could have been on the high side of the standard deviation and this next one, the one you are calling out on the low side of SD.

What I'm looking with the velocity in a ladder like this, is a big jump or even a drop off as I'm approaching a max charge weight/max chamber pressure. The ladder I did after this was with a .223 and XBR which I could not find load data for. When I got a jump of 100 fps, I stopped, brought the remaining rounds in the ladder home, and pulled them

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PaulS
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PostPosted: Sun Apr 05, 2020 5:15 pm    Post subject: Re: A beginning for 257 Roberts Reply with quote

I'm not going to say that what I'm doing is THE right way or any better than any other way.
It is just the way I am doing it. I builds trust in the load and provides a record of the velocities and standard deviations with each load I test. I used this method to find my pistol loads and I am very happy with the results. I trust those guns to shoot predictably under all conditions.
On a side note I have had so much trouble with the 257 finding any consistency at all that I decided to do a work-up this way to help build confidence in the rifle, the load I end up with, and myself.
I do like shooting the gun and I am having a good time playing with the numbers. For me to find a "good" load I have to shoot it in the cold, in the damp spring and in the mid-summer heat. If it remains accurate over that stretch of time and in those differing conditions then I am comfortable that it will always be there for me.

I'm having fun with it! Smile

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Paul
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Vince
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PostPosted: Sun Apr 05, 2020 6:18 pm    Post subject: Re: A beginning for 257 Roberts Reply with quote

“PaulS” wrote:
... I'm having fun with it! Smile

Mate, at the end of the day, that is the most important thing...you’ve enjoyed yourself and had fun. If you didn’t reach the desired standard, then you go out again tomorrow and have more fun.

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Elvis
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PostPosted: Sun Apr 05, 2020 7:06 pm    Post subject: Re: A beginning for 257 Roberts Reply with quote

fun and recoil therapy all rolled into one..... Paul mate ,you do what suits you.when you find a load that works for you......stick to the sucker and be happy LOL.

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slimjim
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PostPosted: Mon Apr 06, 2020 4:06 am    Post subject: Re: A beginning for 257 Roberts Reply with quote

PaulS wrote:
For me to find a "good" load I have to shoot it in the cold, in the damp spring and in the mid-summer heat. If it remains accurate over that stretch of time and in those differing conditions then I am comfortable that it will always be there for me.

Definitely need to build confidence in our loads over all weather conditions. I will take the same paper target to each range session over a years time and shoot 2 shots at point of aim (POA). I'll cover the holes from the back with different colored tape after each range session. The points of impact (POI) is my rifles true performance. This is how I like to do "10-shot" groups.

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PaulS
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PostPosted: Wed Apr 08, 2020 9:42 pm    Post subject: Re: A beginning for 257 Roberts Reply with quote

Slim,
I agree completely. The shot that is the most important is the first shot.
I have never had trouble with the first shot going someplace that the following shots didn't follow. I have heard that it can happen - my brother is having that issue with his new 22. I think it is not uncommon with new barrels. Once a barrel gets shot for a few years they seem to straighten out.
Slim, I want you to know that I appreciate your input. I respect you and your time is valuable as is your wisdom. You are a good man and I do appreciate the help you provide.

Fun and recoil therapy and then more fun crunching numbers and reloading the next batch.
The only interruption is cleaning the guns and that is relaxing so it's all good times.

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Paul
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Speer, Lyman, Hodgdon, Sierra, and Hornady = reliable loading data
So and So's pages on the internet = NOT reliable loading data
Always check data against manuals
NEVER exceed maximum listed loads
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PaulS
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PostPosted: Tue Jul 21, 2020 6:02 pm    Post subject: Re: A beginning for 257 Roberts Reply with quote

I fired half the cases I had loaded, five rounds of each in 0.1 grain increments looking to see where pressures were going to come into play. I got half way through the loads and had to stop because I was getting tired. The loads from 47.5 to 48.9 grains of H414 under a Speer 87 gr. TNTHP using CCI 250 primers. No signs of pressure with velocities that went from 3218fps up to 3417 average of 5 shots. I have three good groups in those and with 11 more loads to check I assume I will have at least two more groups under an inch.I got real good extreme spread with 48.6 grains with ES = 19.5 and a standard deviation of 9.8 with an average velocity of 3389 fps. In a group under 1 inch at 100. So far that looks like a winner.
I'll let you know when I get done with the last 11 groups what I find. It seriously looks like I will be close to 3500 fps if I don't run into pressure signs before I get to the listed 50 grain "maximum". I keep feeling like there is a 1/4 inch group in there waiting for me... Very Happy Cool

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Paul
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So and So's pages on the internet = NOT reliable loading data
Always check data against manuals
NEVER exceed maximum listed loads
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