257 STW - 10 Loads for the 100gr Sierra Game King

Andy

Andy

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I recently purchased this Browning M1885 from "Doug", who has recently become my "Overbore" Rifle supplier, the previous rifle being a Rem 700 in 300 RUM. I don't "need"it, (I only hunt whitetails at 200 yds and less - no Pronghorn at 500 yds), but I wanted it. Before there'a a chorus of "It's overbore!", "It's inefficient", and "It's a barrel-burner", let me say - "obviously". I can afford the powder, and if, after hunting with it for 40 years, the barrel has lost its accuracy edge, maybe my grandkids will re-barrel it.

Below: Browning M1885 "High-Wall". 26" fluted 1:10 twist barrel. Bushnell 3200 5-15X50 scope in Leupold rings

Browning_1885_257_STW.jpg


Below L to R: 25/06, 257 Weatherby, 257 STW

2506_25Wby_25STW.jpg


Below L to R: inverted bullet showing throat length, seated 100 gr Sierra Game King at 3.540", unseated bullet.

257_STW.jpg


I wanted to zero the rifle, and try out some powders, so I chose 10 different powders, of which three are obsolete (H570, H5010 and H870). All loads are published maxes, or if no info was available, what I believed would be under a max load. Now that the rifle is zeroed, I have some nice fire-formed neck-sizeable brass and some load data, I'll choose a bullet (100gr TSX?) and do some load development.

In doing the load development, I also learned a bit about a few powders for which there is very little data, i.e. their relative burn rates in the 257 STW. Here it is:

Winchester 7mm STW brass sized to 257 STW
CCI Mag Primers
3.540" OAL (0.060" off the rifling)

1. Re25 - 84.0 grs - 3800 fps (max load)
2. H570 - 86.0 grs - 3575 fps (well under max load)
3. H1000 - 86.0 grs - 3880 fps (max load)
4. Retumbo - 88.0 grs - 3850 fps (max load)
5. H5010 - 92.0 grs (full) - 3850 fps (just under max load)
6. H870 - 92.0 grs - 3850 fps (just under max load)
7. Re50 - 92.0 grs - 3650 fps (well under max load)
8. H50BMG - 92.0 grs - 3540 fps (well under max load)
9. US869 - 92.0 grs - 3550 fps (well under max load)
10. 20N29 - 93.0 grs (full) - 3540 fps (well under max load)

I'm done with H570, H5010 and H870, as they are obsolete and I only have 1-2 lbs of each. My beloved H870, and H5010 would probably have been excellent choices, but alas, they're gone forever.

I'll likely settle on Retumbo, Re50 and H50BMG for the next stage of load development.

If the definition of "Overbore" is that no powder exists that allows the use of a full case and not be overpressure with heavy bullets, then the 257 STW is certainly not overbore. 100 grs is only a medium weight bullet, but Re50, H50BMG and 20N29, would still be under max pressure with a full case with a 120gr bullet. Interestingly, US869, even though having a burn rate between H50BMG and 20N29, is so dense (I could fit 102.0 grs in the case under the 100 gr Sierra), that I could go no more than approximately 96% load density.

I image that 20N41 would be a good powder choice, as would Re33 when it comes out.
 
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I don't know exactly what you are looking for here, but if you are planning for using this as a hunting platform, a Sierra bullet of any type at those velocities sounds messy and a recipe for disaster.
 
If you use a monometal bullet like the TSX/TTSX, the bullet will hold together, and you will at least minimize the amount of bloodshot meat that results.
I have owned three 7mmSTW rifles, and I actually considered a 257STW myself, but I really didn't feel like having a new barrel installed every couple of years.
 
Awesome post Andy, I have been looking at the 257stw for some time now. Not sure if you know this or not, but Simpson wrote a multiple page write up on the 257stw in shooting times. It covers pretty much everything needed to get started. Case forming, barrel lengths, favored bullets, expected barrel life, and a fair amount of load data. A neat cartridge for sure.
 
Nice round. I have it's parent and grandparent. RL33 might be a good powder to try when it becomes more readily available. I want to try it in my 264WM.
 
neat..and they say 25-06 Ackley improved is overbore.

I had 7stw setup a few years back...the 25 looks like a lot fun also.

You should try the 125gr. Matrix or give Dale at chinchanga (spelling) a call for some even heavier options.
 
A bump for an old thread as this information is as good as anything that can be found on the net.

I just finished my 257 STW 2 days ago. Its a Rem action trued, with a 28" benchmark 3 groove 10 twist finished at 28"

So far I have only used US 869 and a 100g ballistic tip in the soft and ridiculously expensive Nosler 7mm STW brass necked down. OAL of 3.585 this puts the bullets about 15 thou off the lands which seems best so far.

92g = 3750fps and around an inch at 100yards
93g = 3850fps and the odd very faint ejector mark and shoots around 1" or better at 100 yards.
94g = 3880fps with a couple ejector marks.


I am finding the US 869 to give fairly large velocity swings up to 70fps but my neck tension is varying a bit as is my OAL. I will test the accuracy out at longer ranges and if it shoots decent groups I will probably just stick with this powder. Read lots about this powder being dirty but up at the higher pressures I don't see as being a problem. It does take a bit more to get it all out when cleaning but its not a big deal and I am not seeing any carbon rings ahead of the chamber.
 
Republic of Alberta said:
A bump for an old thread as this information is as good as anything that can be found on the net.

I just finished my 257 STW 2 days ago. Its a Rem action trued, with a 28" benchmark 3 groove 10 twist finished at 28"

So far I have only used US 869 and a 100g ballistic tip in the soft and ridiculously expensive Nosler 7mm STW brass necked down. OAL of 3.585 this puts the bullets about 15 thou off the lands which seems best so far.

92g = 3750fps and around an inch at 100yards
93g = 3850fps and the odd very faint ejector mark and shoots around 1" or better at 100 yards.
94g = 3880fps with a couple ejector marks.


I am finding the US 869 to give fairly large velocity swings up to 70fps but my neck tension is varying a bit as is my OAL. I will test the accuracy out at longer ranges and if it shoots decent groups I will probably just stick with this powder. Read lots about this powder being dirty but up at the higher pressures I don't see as being a problem. It does take a bit more to get it all out when cleaning but its not a big deal and I am not seeing any carbon rings ahead of the chamber.
Click to expand...

Keep up the good work!

I did a bit more work last year in the 257 STW with the US869, but did not achieve the MV's you have (the two extra inches of barrel you have probably account for about half of the difference):

94.0 - 3725 fps
95.0 - 3850 fps
96.0 - 3900 fps

I think that the highest MV I will be able to achieve with my gun at sane pressures is about 3950 fps and with about 97.0 grs of US869.

I also discovered that the Burn Rate of US869 is much closer to H50BMG than I previously thought - it seems to be just very slightly slower. It's much more dense though, so more can be fit in the cartridge.

If I was going to hunt with this gun, I'd likely develop loads for the Barnes 100 gr TSX (my 1:10 barrel twist might not stabilize the 115 gr TSX).
 
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Andy thanx for your work with this cartridge. I think I will stick with the 93g load for now. I am on my 3r firing with some the brass and think that 93g is about all this Nosler brass can take and still get a reasonable amount of use out of it. My 3 groove bbl may be helping with velocity a bit. The gun is now shooting well under an inch as well. Haven't tried out past 100 yards yet....
 
"I want it" is the best reason to buy anything. Sierra says their 100 grainer GK is best past 200 and the Prohunter for under 300. Don't imagine Bambi will notice or care though.
 
I have a suggestion for you, if you are going to use the sierra 100 gr game king for deer hunting, maybe find a harder bullet. I used to use them out of my 257 wby for mule deer hunting, when I shot deer inside of 300 yards they would blow up on the hide. at the velocities you will get from a 257stw these will act just like a varmint bullet. At 250 savage velocities they work great. I would recommend using a 100 gr barnes BT
 
Any more load updates or any good reports of on-game performance this past season?

I, too am thinking about this cartridge...any ideas what a 110gr Accubond or a 115 TTSX might do as far as muzzle velocity? 3600 +/- perhaps?
 
tjhere is a guy in Rimbey working on a new wildcat round he calls the 25 Extreme, I think his case starts with the lapua 6.5 x 47. not as hot as you fellowa are looking at but sounding good for its size. FS
 
25 caliber for long range needs longer bullets and fast twist barrels. Been experimenting with a long-necked 25 SAUM. Barrel is 1:8 twist. 135 gr bullets and Retumbo results are very good, 3150 fps. Haven't tried 145 or 155 gr bullets yet. For some real wild and crazy ideas check "Allen Magnums" web site. They start with RUM cases. My goal with the 25 SAUM was to have a cartridge capable of winning F-Open matches. Retumbo doesn't heat up barrel steel as quickly as R-25. 300 meter groups with the 135's have been fantastic. Also discovered stainless barrels cool much slower than chrome moly barrels.
 
I used 110gr accubonds out of my 257 wby. For the last 2 years with great results. My handloads chronograph 3480, all bullets have exited the far side of the animals shot
 
I have a 257 stw and believe it or not a 257 stw ackley improved.
The 257 was built at corlanes trued and all the good stuff with a 26 in fluted pacnor barrel. I have mostly bend shooting have 110 swift scriroco out if it. Powder choice was a challenge. I was using R25 which worked good had great velocity. Only problem was it would all if a sudden pressure up for no reason. Well actually the reason was powder bridging when you were shooting it. I switched over to ramshot magnum which is a ball powder. Problem was solved. I would have to check on the velocity. I haven't #### the gun in a few years.
The other one that is the 257 stw ackley is built on a remington action with a sendero barrel that was re chambered. Out if this one I shoot the 110 accubonds with R25. This one I never had any pressure problems with. Shoots really good and like can be expected really fast. I only shot one deer with this gun 598 yards broadside, clipped one rib on the way in and I recovered the bullet against the hide on the far side. Deer went 20 or 30 yards. I was a little disappointed in the performance.
I have had several and still have one 257 weatherby magnum and have always #### 117 gr hornady btsp out if them.
Makes a real good deer gun. Just not at long range.

I haven't shot them in a few years. I got more into long range shooting and the 25's just don't have the energy or bc to do the job.
Been more into the 6.5 mm's and the big 30 calibers with heavier bullets.
Never know I may have to sell these as they don't get used.
 
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