270 WBY vs 7mm Wby..what am i missing here?

icehunter121

icehunter121

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K folks..a buddy of mine picked a mk5 in 270 WBY from a estate sale. With factory ammo the groups where only 2 inches or so and that was with 140 gr. Accubonds. The velocity was just about 3400 fps. With there hand loads of h4831 with a 140 barnes ### they only got 3100-3200 or so.So I grabbed one of my manuals and did some looking. Its the hornady 7th edition.

Comparing the 2 calibres the 7 WBY i own can drive a 139 gr slug out at 3400 fps but when you flip a few pages back the 270WBY maxes out at 3100 fps...WTH?? Its the same basic case and all just a tad smaller slug diameter


Any ideas?? He wants to drive a ### shock at 3400 or so...get good accuracy which is why I am tuning up his rifle this weekend...but why the big change in the one manual??
 
This isnt a earlier rifle. Its the newer fluted,synthetic stock model. Not sure what the rate of twist is in it,but by looking and the data in the link I am wondering if it has to do with the bearing surface of the tsx slug..more bearing surface = more friction and a lower velocity...Just a thought..
 
As you know some manuals are pretty conservative with their published data. I have handloaded 130gr tsx's to 3450fps, 140gr tsx's to 3350 and 140 accubonds to mid 3300's. Each gun is different but in mine at least these loads did not exhibit any signifigant signs of pressure.

IMR 7828 and RL22 are great for velocity but 7828 showed very little tolerance for temperature variations so I stopped using it.
 
In my Lee book, the loads for 270 weatherby with a 140 gr jacketed bullet, IMR7828 lists a load of - Start Gr 64.7 for 2965 f/s up to max 73.5c gr for 3325 f/s @ 53000 CUP
Minimum OAL 3.295"
That powder is at the top of the velocities listed for 140 grain bullets. Reloader 22 comes in second.
For a barnes X bullet, there is only the 130 gr triple shock near that weight range. BUT, I'll give the top loads anyhow. Of course only 3 powders listed Accurate XMR 3100
61.9 gr start @ 2892 F/S up to 72.5c gr for 3338 F/S @ 67000 PSI Min OAL 3.295"
Just some stats from another book for you to compare. Hope it helps a little bit.
 
Thanks for the help folks.He dropped off this rifle with me yesterday and to say the least I am not impressed with it.I know this has nothing to do with velocity but it sure does with accuracy. I took it apart and it has this fancy dancy aluminum bedding plate in the stock.But the barreled action can move back and forth about 1/16 of a inch and a lateral roll of at least a good 1/4 of a inch. No bedding what so ever in the stock.

There are 2 pressure points on the fore end but with a fluted barrel these arent even giving a firm point on either side.My idea for him is to bed the rifle properly,get rid of the pressure points so the barrel is free floated...then start working up some loads for it.If we can get a inch or less at 3300+ fps he would be a happy camper.Its just tough for me to do with out his approval on kind of a costly rifle.Meh screw it..he likes to spend money!!

But keep the help coming as this is a work in progress and I will surely post the results as they come in..
 
My Weatherby ULW was the same as what you are describing. I bedded the recoil lug and sanded down the original pressure pad and built up a new one that provides more even barrel contact.

I decided to retain the pressure pad because often very light contour barrels respond better to slight fore-end pressure than to be entirely free floated them. YMMV.

You may want to experiment with the amount of pressure the pad exerts on the barrel, mine is around 4-5 lbs.

As far as IMR 7828 goes, I was able to achieve the velocities I wanted however I found it to be quite temperature sensitive. During a range session in the summer I had my established 140gr.TSX load shoot 100-150 fps faster through the chrony for a three shot string. Being concerned I stopped shooting and pulled some rounds when I got home to confirm the charge weight was correct...it was. I also think some of the difference came from 2 different lots of powder as I have used this new lot of powder and am getting similar velocities as before at nearly a grain less powder.

I am a Weatherby fan but sometimes I wonder why :p I've had some pretty frustrating range sessions with a couple of my guns to the point where I felt like selling the whole lot of them and be done with it. They will shoot well, sometimes it just takes a lot of patience and determination.
 
marcoman said:
My Weatherby ULW was the same as what you are describing. I bedded the recoil lug and sanded down the original pressure pad and built up a new one that provides more even barrel contact.

I decided to retain the pressure pad because often very light contour barrels respond better to slight fore-end pressure than to be entirely free floated them. YMMV.

You may want to experiment with the amount of pressure the pad exerts on the barrel, mine is around 4-5 lbs.

As far as IMR 7828 goes, I was able to achieve the velocities I wanted however I found it to be quite temperature sensitive. During a range session in the summer I had my established 140gr.TSX load shoot 100-150 fps faster through the chrony for a three shot string. Being concerned I stopped shooting and pulled some rounds when I got home to confirm the charge weight was correct...it was. I also think some of the difference came from 2 different lots of powder as I have used this new lot of powder and am getting similar velocities as before at nearly a grain less powder.

I am a Weatherby fan but sometimes I wonder why :p I've had some pretty frustrating range sessions with a couple of my guns to the point where I felt like selling the whole lot of them and be done with it. They will shoot well, sometimes it just takes a lot of patience and determination.
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Kind of a PITA to have such problems with a $1700 rifle...
 
I have a older manual that i guess is before everyone got to conservative that has max loads with two common powders at around 3450 fps. The powders listed are 4831 and 4350. both loads are for a 130 gr spitzer the 150gr spitzers go up to 3250 fps
 
1899 said:
Kind of a PITA to have such problems with a $1700 rifle...
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Very valid point, however all manufacturers have put out rifles with their own little idiosyncrasies albeit it does make it more annoying when you drop almost $2k on a rifle and have to tear it down to get it to shoot.

As if to rub salt into the wound I picked up a well used Sako Fiberclass in .300 Win for $600 that will out shoot every rifle in the safe save for a Sako TRG22 and an M24 clone .308 ..... go figure :redface:
 
1899 said:
Kind of a PITA to have such problems with a $1700 rifle...
Click to expand...

That's because now days $1700 isn't that much for a rifle. Read the forums, unless you're packing a 3k to 10k super tacticool rifle, you may as well just buy a Stevens.;)

On the flip side, the Stevens will likely out shoot it, lol.

Each rifle is an anomaly unto itself, to paraphrase a tad. They are all different, and they all require a little tuning. Ok, some more then others. - dan
 
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