Know the target velocity; want least pressure?

[Potashminer]

I have several 7x57's that I have been loading with 145 Speer HotCor and 150 Nosler Partition. My "pressure series" workup with my shooting Chrono matches quite well with Speer and Nosler manuals. Read all the cautions about 1893's and 1895's versus modern actions.

I recently acquired a "Mod. Mauser 1896 Ludw. Loewe & Co Berlin" B7XX serial number with the "crown over fracktur" symbol below the receiver serial number . The bolt has the square bottom as per the 1893 style that were made by Loewe for shipment to South Africa Republic in 1896. Full length 29"+ barrel; stock cut off ahead of barrel band, mismatched bolt, so I don't believe this has any real historical significance any more.

The bore has received days and days of soaking in Wipeout; about 3 times 10 strokes with snug fitting patches and JB's and one flush with carb cleaner. I no longer get any color of any sort on patches, but bore is quite dark, yet.

I would like to shoot it. I have a supply of .284" 175 Hornady round nose . I read that original loads would have been 173 grain round nose solids at 2300 fps - from the 29 " barrel.

I am a bit stumped regarding best choices for powder. John Barsness articles on pressure have pretty much convinced me that velocity and pressure are closely related, at least as far as increasing charge in a pressure test series. What I am not clear on is the velocity / pressure relationship when changing from one powder to another. Is it possible to chose among powders to get the 2300 fps but with greater or lesser peak pressure? If so, would slower powders be the direction to go?

 

[amosfella]

With nothing to back me up at this point, it would depend on the burning speed and profile of the burn as well... I'd be looking at IMR 7828 or IMR 4831 to start. I've always had best luck with the slowest powder for the bullet weight and speed.

 

[Longwalker]

Before you shoot anything out of that clean, dark bore, coat it with Dyna bore coat. Their micro ceramic bead treatment can make a very big difference on old, dark, but clean bores. Bullet jacket material just slides over, doesn't not imbed in the rough spots. I used it on a nice old 9x57 that needed some TLC, it even shot cast Ok afterwards. I also used it to treat a couple of high volume .22 center fire varmint rifles that could not be cleaned until well past what they deserved otherwise. No fouling after scores of shots. Well worth the trouble to send away for a kit.

 

[Longwalker]

Slower powders do give a gentler rise to peak pressure. I like H4350 in my 7x57's and I have no trouble with "over pressure" at good velocity, (2350 fps with 175's in three 7x57's ) but I have seen pressure spike a bit with faster powders that I have tried and especially with some ball powders. Ball powders like W760 tend to be less forgiving at the top end. IMR 4831 is slower burning than H4350 and relatively low pressure for your desired velocity in the 7x57, might be good if you can get enough in to reach 2300 fps. IMR 7828 is too much of a good thing in my opinion, but not likely to be "dangerous".

 

[huntingfamily]

Potashminer

I also load for a few 7x57's.

With your situation, slower powders is the way to go.
That said, Alliant Reloder 25 or Hodgdon Retumbo should give you around those velocities with low peak pressures.

Increase powder charge gradually while watching for pressure signs. Use your chronograph.

YMMV

 

[Ganderite]

Slow powders will give you maximum velocity - in the range of 2800 fps.

Assuming you want some accuracy, I would not download a slow powder to 2300 fps. For that velocity you want a faster powder.

Based on a 24" barrel & 150 gr bullets

36 4320 - 2,365
35 4895 - 2,475
38.5 RL15 - 2550
48 - 4831 - 2625

I would try 4895 first, or 4064.

 

[amosfella]

Slow powders will give you maximum velocity - in the range of 2800 fps.

Assuming you want some accuracy, I would not download a slow powder to 2300 fps. For that velocity you want a faster powder.

Based on a 24" barrel:

36 4320 - 2,365
35 4895 - 2,475
38.5 RL15 - 2550
48 - 4831 - 2625

I would try 4895 first, or 4064.

Are you looking at the right bullet weights?? The loads listed by you don't come close to matching 2 books I have looking at the 175 gr bullets... The OP was asking about loading a 173 gr bullet...

 

[Ganderite]

Are you looking at the right bullet weights?? The loads listed by you don't come close to matching 2 books I have looking at the 175 gr bullets... The OP was asking about loading a 173 gr bullet...

Thank you !! Good catch. I was quoting the 150 gr load.

For 175 gr bullets around 2300 fps. This is not a mild load.

37 RL15
38 4064
44 4350
45 4831
46 RL22

 

[Potashminer]

Thanks to all for your replies. I am hoping to duplicate the original 1895-ish load to see for myself what it performs like. Amazing to read reports of the best Boer marksman opening fire on British columns at more than 1,000 meters distance (with iron sights!), and the American's incredulity at the rate and effectiveness of the fire they received at San Juan hill.
I went down the road this morning and retrieved my Lyman's 49th, and it appears they used a similar 29" Mauser 95 for their velocity numbers and a universal receiver for the pressure numbers. It specifically states that the SAAMI limit of 46,000 CUP was set in deference to the M93 and M95 actions. I note that they list 41.5 through to 46.0 of H4831 (31,400 CUP and 41,600 CUP, respectively), and I have that powder on hand, so will start there. I also have IMR 4350 to try next if the H4831 doesn't work out.