Can anybody explain this?

[Blue-Dot-37.5]

I shot my .257 Wby Mag today after work. I didn't have enough time to shoot the Savage ML, hopefully that will be tomorrow.

Weatherby Stainless Vanguard, tupperware stock, I did bed the rifle. Leupy VX-III 4.5-14x50 Long Range scope w/side focus.

I set up targets at 100, 200 and 300 Yds. I didn't get a chance to chrono the load, but I know that it's not "weatherby" fast. For some reason, if I get anywhere above 1/2 of the recommended powder range, there are pressure signs. (i.e. powder range is 60-70 grains, 66 grains shows signs of pressure)

The load is 115 gr. Barnes Triple Shock FB bullet, 55.0 g IMR-4350, Fed 210M primer OAL 3.425. (yeah, it's long but it still feeds from the magazine.......)

I shoot directly South, wind was from N/NW 5-15 mph. The first 100 Yds is open field, the last 200 is into woods.

shot #1 from cold clean gun impacts .25" left, .5" down from point of aim.
Shots 2,3,4 make a sloppy cloverleaf 1/4" above POA, 1.5" left. group size is .7" c-c

Shots 5,6,7 are @ 200 Yds. Same POA. Impact is 2.5" left, about 2" low again sloppy cloverleaf .7" c-c

Shot 8, 9, 10 is @ 300 Yds. Shot 8 is 5 1/4 down, 2 3/4" left. Now my neighbor comes over and bs's for 25 minutes. The gun cools down (I was taking about 2 minutes between shots before the bs session) Shot 9 is 9.5" down, 1 1/8" left. Shot 10 is 6" down, 2" left. On all targets I held POA on the same spot.

Now I can understand why shot #9 is low (different barrel temp) but I can't understand why the group size didn't appreciably open up as the range increased. Shots 8 & 10 are roughly 1" apart..... I ran out of daylight, so I had to quit shooting. I need to shoot again with different wind to see if I really have to move the sight or if it was 100% the winds fault.

Any ideas anyone?

Blue-Dot-37.5

 

[laker]

Blue Dot Try this I had simillar with my weatherby. Are your action screws torqued down. Try to torque down to 65 in LBS. I was getting very tight groups @100 yds but I would get 2 point of inpacts with the same POA. I could shoot 6 shots and 3 would be in one group and 3 would be 4-6 in apart. I called weatherby and they told me to torque the action screws to 65 in LBS and WALA. GOOD LUCK..

 

[Blue-Dot-37.5]

Thanks laker. I'll try that. I'll check mine first, I don't know what they are now.

Blue-Dot-37.5

 

[Doohan]

if I get anywhere above 1/2 of the recommended powder range, there are pressure signs. (i.e. powder range is 60-70 grains, 66 grains shows signs of pressure)

Maybe a long shot but it could be a sign of throat erosion. Have you had this gun a long time? Shot the heck out of it?

Sorry, only thing I can think of??

 

[big6x6]

55.0 g IMR-4350

Kinda off the subject...
That's a kinda fast powder for the .257 Weatherby isn't it? You've tried IMR-7828, AA-8700, AA-3100, H-1000, RL-25, or RL-22? I've never used any but Norma MRP was the standard powder for years in most of the Weatherby cartridges. While usually very accurate I have found IMR-4350/AA-4350 to be kinda hot natured in .270 Weatherby, 7mmRemMag, .300 Winchester, and .300 Weatherby. I have in fact quit using it in those calibers for that reason. Slight powder charge increases and even temperature changes sometimes go from no pressure signs to a bolt that is hard to lift with no warning. That really means it was too hot to start with. Couple that with a copper alloy Barnes bullet and I'll have a pressure problem. ANYWAY....

Back to your problem... I just checked wind drift with my new "Load from a Disk"! Lets say you are getting 3100fps with that load and the Barnes bullet has a bc of .400. At 300yds you have 10.7 inches of wind drift with a perfect 15mph crosswind. 3.6 inches with just 5mph. I vote wind is at least partially responsible...

 

[Blue-Dot-37.5]

I've owned it for 1.5 years and only have run maybe 250 rounds thru it, taking care not to overheat the barrel. I don't think the throat is eroding, at least I hope not! It was new when I purchased it $368.00 out the door.(thanks wally world !)

Chuck:

You are probably right. I have tried most of the powders listed, and some not listed.... (but the powder mfg gave me load info). I still have lots of playing to do with it, but because of the thin barrel I can't shoot it fast, or for an extended length of time without watching the barrel temp climb, sorta like the Savage ML's.

I have some Cerro-Safe & I will slug the chamber when I get a bit of free time.

I was really wondering if anybody could explain why the groups didn't get much larger despite going from 100 to 200, then to 300 Yds.

Sierra said to try the same load, with flat based bullet and with a boat-tail.
According to them, some Wby's prefer one style bullet over another.

Blue-Dot-37.5

 

[Doohan]

whew!! good thing..

Maybe if you had 12x the rounds through it you may want to check..

That is a heck of a deal!!

 

[big6x6]

Sierra said to try the same load, with flat based bullet and with a boat-tail.
According to them, some Wby's prefer one style bullet over another.

That's good advice with ANY rifle/cartridge! Usually and mostly a flatbase WILL outshoot a boat-tail until the distance gets on out there. A 117gr Sierra ProHunter would be a good one to try. Harry1 my brother had really great accuracy with the 115gr Nosler Partition.

I was really wondering if anybody could explain why the groups didn't get much larger despite going from 100 to 200, then to 300 Yds.

Don't argue with success!

 

[Blue-Dot-37.5]

I splurged last night and ordered a box of factory ammo from Midway loaded with 115 grain Barnes X bullets. I'll see how they shoot and chrono them. If they shoot a couple hundred fps quicker and don't show any signs of pressure, I'll try setting the OAL of the handloads back to factory specs to see if that helps with the pressure signs with the higher powder load levels.

Blue-Dot-37.5

 

[omega]

I splurged last night and ordered a box of factory ammo from Midway loaded with 115 grain Barnes X bullets. I'll see how they shoot and chrono them. If they shoot a couple hundred fps quicker and don't show any signs of pressure, I'll try setting the OAL of the handloads back to factory specs to see if that helps with the pressure signs with the higher powder load levels.

Blue-Dot-37.5

Length (OAL) especially with Barnes bullets would be my bet on the pressure signs. I went through this with a 375 H&H Encore barrel, I was way below on powder with Barnes 210 grain bullets and flattening primers with a lot of barrel heat. I had to relearn that lesson on a 25/06 barrel 2 years later! 35 to 50 thou off the lands and no pressure and incredible accuracy.

 

[Blue-Dot-37.5]

omega:

The problem with the Wby is the freebore that Roy Weatherby designed into his guns to reduce pressure. With anything less than a 115 gr. bullet, there is so much freebore in my gun that the bullet will be free of the case before it contacts the lands/grooves. I only have the Barnes bullet in the case slightly more than 1 bore diameter and it's still .125" off the lands/grooves. Its' impossible to load the Weatherby cartridges like a normal cartridge.

Does anybody know where I can find a dimensioned print of the different Weatherby chambers, specifically .300 Wby and .257 Wby? Not of the loaded ammo, but of the chamber that shows what the length of the freebore should be.

Blue-Dot-37.5