Need Help! Weatherby MK 5 in 300 Weatherby magnum

[stagpanther]

So here's the background: A local businessman has let me hunt and shoot on his properties for years. He takes off to go on hunts all over the world several times a year and his thing is bagging big game. He always has let a local gun store take care of his rifles prior to leaving for a hunt.

Last year he asked me if I would like to tune/zero a rem 700 in 7mm RUM and it took me all of 1 second to think about it and say sure! It turned out to be a fantastic shooter and the guy was very pleased with my help. So he just asked me to tune and zero his Weatherby Mk 5 in 300 Weatherby Magnum for a hunt in Wyoming he leaves for this weekend. Being yet another rifle/cartridge I haven't shot before--I jumped at the opportunity immediately.

I'm using their factory ammo--180 gr partitions which were averaging around 3,280 fps. Stuff is quite good--I got an SD of around 5 fps out of the first 5 cartridges I fired.

I was asked to zero at 300 yds and was told he might use it out to 600 yds. A quick check of ballistics chart shows what I consider a reasonable point-blank range out to about 500 yds.

The rifle is topped with a Trijicon 2.5 x 10 x 56 accupoint; another interesting piece of equipment I hadn't used before.

Long story short--I fired 3 4-shot groups at 300 yds and I couldn't get it to group worth beans, they were about 7 to 8 inches in size. It is a bit of a kicker--but no worse IMO than my savage 111 in 300 win mag which I've enjoyed shooting for years and will easily group sub-MOA beyond 300 yds.

I'm thinking maybe loose rings (they are Weatherby specific 1-piece mounts) but I'm a bit hesitant to go that route since the present set-up is set to his personal LOP/eye relief.

Any thoughts/advice?

[sako2]

Do you have any rl23 to try or any rl33 to try with a 200 gn bullet?

[sako2]

What powder are you using nosler list imr4831 as the most accurate powder for 180.

[stagpanther]

I have both of those powders--but this guy uses Weatherby's (expensive) ammo only. He's going for deer/elk size game.

[sako2]

OK sounded like you where loading for it. Can you get a box of 200 gn to try?

[44 AMP]

Zero it for 300yds (or your desired mean point blank range) with the ammo he's going to use, in time for him to take it this coming weekend? You could do that.

Tune the rifle to shoot acceptable groups in that amount of time? I wouldn't promise him that. Just too many things to check, and test and too little time.

Ok, general thoughts as I think of the, in no particular order..

if the rifle won't group well enough, there are roughly 5 broad categories to look at.

rifle
optics
ammo
shooter
and the "fit" or relationship between each and all.

some things can be easily checked, other things require testing. Let's start with the rifle, in general. Is it a new rifle? Is there anything obviously flawed or damaged? (like the crown?) Is everything that is supposed to be tight, tight? (action screws, mount screws?) If everything looks right and works right, we pause, for now.

Optics; same in general, looks ok? screws tight? One can test the optics by putting it on a different rifle of known performance (one that has a similar recoil level). Its a bit of work, but it can rule out the scope being the problem.

Ammo: this gets a bit tricksy, because there are two categories combined. There is the uniformity of the ammo itself, and there is the way the rifle behaves shooting it.

last is the shooter. you sound like you've got the experience that we can for now, leave the human element for last.

I'm afraid I don't know what Weatherby is doing with their rifles today. I do know what they were doing 30-40 years ago, but don't know if that still applies.

Back then, Weatherby Mk Vs were known for having about 1/2" of freebore. They were never known for being extremely accurate, they delivered decent accuracy for big game hunting, but not MOA or better, usually. Also, back then, the only ammo for them came from Weatherby.

Does the Mk V have the slender 26" tube?

A lot could be different today. First thing I would suggest is getting some different ammo and seeing if you get the same or similar results. I would also suggest not being over concerned with a 4 shot group.

Here's a question I just thought of, those groups you shot, were they seeming random dispersal or were some shots close together with a couple far away?

Any way you could tell which shot went where? What I mean is, is the first shot "on" and the second one close? And as the barrel heats the next two are in different counties??

Lots and lots of questions, all can be answered, but not before the weekend.

And, FWIW, a different rifle in a different though similar caliber shooting MOA doesn't mean anything about the MK V you are testing.

[stagpanther]

Just did some work on it before reading the latest posts--already came to many of the conclusions you mentioned above 44. BTW--the only real comparison I made to the 300 win mag was the felt recoil (I didn't mean to say it's accuracy was comparable, only that I shot it well enough to get good accuracy with it)--which I don't think is all that different. Anyway--looks like I fell down the rabbit hole whether I like it or not.

I decided to take the scope off and check the mount/rings out--there was an obvious mis-alignment between the front and rear rings, a gap in the front rings had formed and the a gap between it and the scope body had formed and filled with a bit of debris and rust. The scope body itself has some wear damage as a result. The rear mount screws in the receiver were looser compared to the front ones--I don't know what the factory specs are (I went onto Weatherby's website and couldn't find a manual download or serial number check list) but torqued them down to equal the front ones (which were around 40 inlbs).

The next obvious thing I looked at were the action screws--both the front and back were spinning freely with little more than about 10 inlbs. After googling for a while I found a Weatherby forum with a recommendation for procedure for tightening action screws on a fiber-stock Mk 5 and followed it. At this point I don't have enough time--or experience with Weatherby--to start fooling with the pad bedding, from what I've read so far these things were not meant to be free-floated. Also did a thorough bore cleaning--loads of copper-fouled patches came out with the bore tech copper remover I used.

He gave me two boxes of ammo to work with ($127 a pop at his GS) and has not so far taken me up on my offer to work up some reloads for him, would take way too much time at this point.

Problem now is--after the work I just did if there is no improvement-- I will have to tell him I wouldn't take the gun on his hunt. Worse than that, I worry he might think I was the cause of the issues.

[stagpanther]

"Zero it for 300yds (or your desired mean point blank range) with the ammo he's going to use, in time for him to take it this coming weekend? You could do that.

Tune the rifle to shoot acceptable groups in that amount of time? I wouldn't promise him that. Just too many things to check, and test and too little time.

Ok, general thoughts as I think of the, in no particular order..

if the rifle won't group well enough, there are roughly 5 broad categories to look at.

rifle
optics
ammo
shooter
and the "fit" or relationship between each and all.

some things can be easily checked, other things require testing. Let's start with the rifle, in general. Is it a new rifle?" no, but the owner says only about 200 shots down the barrel. It has been obviously used in some heavy weather safari action, he's dropped red stag and giraffes with it, dents and rust were on the barrel and the barrel crown has the bluing worn off though I can't see any obvious deformations.

"Is there anything obviously flawed or damaged? (like the crown?) Is everything that is supposed to be tight, tight? (action screws, mount screws?) If everything looks right and works right, we pause, for now.

Optics; same in general, looks ok? screws tight? One can test the optics by putting it on a different rifle of known performance (one that has a similar recoil level). Its a bit of work, but it can rule out the scope being the problem.

Ammo: this gets a bit tricksy, because there are two categories combined. There is the uniformity of the ammo itself, and there is the way the rifle behaves shooting it.

last is the shooter. you sound like you've got the experience that we can for now, leave the human element for last.

I'm afraid I don't know what Weatherby is doing with their rifles today. I do know what they were doing 30-40 years ago, but don't know if that still applies.

Back then, Weatherby Mk Vs were known for having about 1/2" of freebore. They were never known for being extremely accurate, they delivered decent accuracy for big game hunting, but not MOA or better, usually. Also, back then, the only ammo for them came from Weatherby.

Does the Mk V have the slender 26" tube? "

yes

A lot could be different today. First thing I would suggest is getting some different ammo and seeing if you get the same or similar results. I would also suggest not being over concerned with a 4 shot group.

Here's a question I just thought of, those groups you shot, were they seeming random dispersal or were some shots close together with a couple far away? "

I would say random--mostly cause I really couldn't figure out what the approximate center of the group was. I did manage a couple of shots right into the bull's eye--but considering the rest of the group's dispersion I take that as a fluke of luck

Any way you could tell which shot went where? What I mean is, is the first shot "on" and the second one close? And as the barrel heats the next two are in different counties??

Good question--my feeling is that there was an obvious increase in dispersion due to heat--even though I was allowing around 3 minutes between shots. Barrel gets very hot with each shot. Unfortunately I didn't have a spotting scope to see well at 300 yds--nor 10 x was quite enough for my old eyes

"Lots and lots of questions, all can be answered, but not before the weekend.

And, FWIW, a different rifle in a different though similar caliber shooting MOA doesn't mean anything about the MK V you are testing."

thanks for the useful suggestions.

[std7mag]

Stag,
I know i'm coming in late, but thought i'd chime in anyways.

Seems as though you found the issue with the loose screws. But i think you went almost twice the torque on the mounts. Bases usually get about 20-25 lbin.
Rings depends on ring manufacturer, and scope manufacturer. But usually 18-20 lbin.

I wouldn't worry too much at group size, as much as that first cold bore shot.
He's also going to need to rezero the rifle anyways. Big difference from Florida's 28ft elevation with 98% humidity, and Wyomings 7,000 ft elevation and 26% humidity.

[stagpanther]

Stag,
I know i'm coming in late, but thought i'd chime in anyways.

Seems as though you found the issue with the loose screws. But i think you went almost twice the torque on the mounts. Bases usually get about 20-25 lbin.
Rings depends on ring manufacturer, and scope manufacturer. But usually 18-20 lbin.

No problem--I need all the help I can get! Anyways--the mount/rings are a one piece unit on the MK 5; it appears the rear mount is a bit higher than the front. From what I was able to gather in my net sleuthing they need to be torqued down hard--the front ones wouldn't budge until I got up around 50 inlbs (none of the screws on the rifle had been lock-tited as far as I could tell). There was an obvious misalignment between the front and back mount/rings; the front ring had started digging away at the scope body under the rifle's considerable recoil.

I wouldn't worry too much at group size, as much as that first cold bore shot.
He's also going to need to rezero the rifle anyways. Big difference from Florida's 28ft elevation with 98% humidity, and Wyomings 7,000 ft elevation and 26% humidity.

Yes, totally agreed. My goal is to get a baseline of calculator data, generate the tables (dial in the scope) and then point out the variables that will need to be changed depending on where he goes.
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[stagpanther]

OK sounded like you where loading for it. Can you get a box of 200 gn to try?

Not around here--have to be ordered. Do the bigger pills shoot better in the Weatherby?

[stagpanther]

I did finally find the owner's manual on Weatherby's site--it does confirm the action screw torque procedure I ended up using--55 inlbs (rear first then front on synthetic stocks) so right there the action was obviously recoiling badly with the loose screws I found. I'm wondering if the recoil lug is possibly damaged from the loose action. I'm not going to do a total disassemble until I discuss further with the owner.

The rifle looks to me like an older model--it doesn't have the modern spiral fluted bolt body but does have the 9 lugs for magnum cartridges.

[std7mag]

You won't get any wear on the recoil lug itself, if anything the lug recess in the stock might wear a little.
But since he's not shooting a 1,000 yard benchrest match, i probably wouldn't worry too much about it. Especially since you have torqued the action screws properly now.
Best left for a winter bedding project.

[stagpanther]

You won't get any wear on the recoil lug itself, if anything the lug recess in the stock might wear a little.
But since he's not shooting a 1,000 yard benchrest match, i probably wouldn't worry too much about it. Especially since you have torqued the action screws properly now.
Best left for a winter bedding project.

I already talked to him today to prepare for a back-up rifle, which he said he can do--and he thanked me for being frank about the issues. whew.

That 7mm RUM I worked on last year would be perfect for long range hunting of deer or elk IMO, but people get used to particular rifles I guess.

[stagpanther]

After changing the scope ring's screw tension on the 300 Weatherby Mag to 25 inlbs +/- I went out and took a few shots yesterday and the scope actually slid back under recoil and the rear ring base moved. Because the mount and rings had been way over torqued (I measured around 55 inlbs) I believe this created a fundamental asymmetry between the front and back rings--there is very hard asymmetric wear on the scope body. I discussed the issue with a Leupold engineer and he said it's possible that some distortion of the scope tube could happen under those circumstances--which is my concern as well. So I'm ordering new base and rings and plan on lapping them when I get them. I have plenty of 30mm body scopes of my own on rifles that can shoot well under MOA--so I'll test his scope on one of my rifles to make sure it hasn't been damaged.

In the meantime, I've checked out the back-up 270 Weatherby Magnum and all the screws appear to be torqued correctly, including the action screws.

[std7mag]

The 270 will be more than adequate for Wyoming.

[stagpanther]

The 270 will be more than adequate for Wyoming.

I'm sure of that. Problem is, his local GS sold him boxes of discontinued old 130 gr ammo (some of which I told him I refuse to fire) so he's stuck using it for his hunt. He says the rifle doesn't like 150 gr bullets and apparently Weatherby themselves confirmed that is sometimes the case. Still, I'm impressed with the performance of the 270 mag--much lighter felt recoil than the 300 too. I'm getting around 3,373 average fps with 130 norma SP's through it.

[stagpanther]

Learning a lot about these weatherby Mk 5's. Heat management is a big issue--I think more so than other sporter barreled type bolt rifles. Either need to wait at least 4 minutes between shots for consistency--or squeeze a chambered cartridge off fast so that it doesn't heat up. The two MK 5's I shot have what I consider exaggerated comb risers which also bulge to the side--for my fat head I found it some work to get close to a natural cheek weld and maintain an easy center line of sight in the optics--though the newer carbon stocks seem to have done away with the side bulge. I found this to be a significant factor in avoiding canting the gun when sighting.

My friend is an "old school Kentucky windage" kind of guy; simple duplex crosshairs and hold-overs is all he does. Works for him, but I'm not confident enough at longer distances in variable conditions for that kind of shooting. I had to have his 270 wby mag ready to go today and zeroed for 300 yds, and as my luck would have it winds last night (my last chance to zero his VX7) were 8 to 12 and gusting 15 crossing almost 90 degrees and dropping into the gravel pit. I decided to go with initial zeroing at 100 yds (which were largely sheltered by thick trees) using the labradar's average of 3,373 fps and ballistics calculator told me that would be around 2.7 inches low at 300 yds. The last 150 yds of the bullet's flight was exposed to the full force of the swirling cross winds, the first three shots I simply wanted to test for consistency.



I was pretty pleased even though the group was about 1 MOA left and low of the center target. I took the fourth shot with an estimated 1 MOA right hold-over and the POI was less than an inch from POA.



Called it good to go, delivered rifle and ballistic charts to my friend and told him I expected some prime backstrap when he got back.

[T. O'Heir]

You cannot sight in for somebody else. You can only sight in for you. You can get the thing close, but the shooter must sight in for himself. Everybody sees and holds every firearm differently.
"...another rifle/cartridge I haven't shot before..." That's a reason to do it, but the guy will not have a rifle that's sighted in. Make sure you tell the guy that as a CYA thing.
"...The 270 will be more than adequate..." Yep. There's no game in North America that requires a magnum of any kind to kill. He's not likely to find .300 Weatherby ammo in the wilds of Wyoming either. .270 is everywhere. Cabela's shows it as on Back Order at $76.99 per 20 for 180's. They do show 180 grain Weatherby brand ammo at $39.99(odd since everything else starts at $65) and in stock. Doesn't mean the Wyoming store has any though.
"...discontinued old 130 gr ammo..." Only matters if it hasn't been stored properly. Old ammo isn't necessarily unsafe. Kind of odd 130 grain .270 would not have sold though.

[stagpanther]

You cannot sight in for somebody else. You can only sight in for you. You can get the thing close, but the shooter must sight in for himself. Everybody sees and holds every firearm differently.
"...another rifle/cartridge I haven't shot before..." That's a reason to do it, but the guy will not have a rifle that's sighted in. Make sure you tell the guy that as a CYA thing.
"...The 270 will be more than adequate..." Yep. There's no game in North America that requires a magnum of any kind to kill. He's not likely to find .300 Weatherby ammo in the wilds of Wyoming either. .270 is everywhere. Cabela's shows it as on Back Order at $76.99 per 20 for 180's. They do show 180 grain Weatherby brand ammo at $39.99(odd since everything else starts at $65) and in stock. Doesn't mean the Wyoming store has any though.
"...discontinued old 130 gr ammo..." Only matters if it hasn't been stored properly. Old ammo isn't necessarily unsafe. Kind of odd 130 grain .270 would not have sold though.
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Oh thank you all-knowing oracle of wisdom for your helpful advice!

All this time I thought all you had to do was slap a scope on turn the screws and that was it?

My friend has taken one or more of almost all of the world's largest game with his 300 Weatherby Magnum--he has much of his house filled with taxidermy trophies to prove it.

He doesn't read about it--he does it.

I'll be sure to pass along your sage advice.

[stagpanther]

The long Weatherby freebore is a fascinating feature of Weatherby rifles--seems to almost fly in the face of conventional wisdom of "shortest jump to lands". The theory seems to be it enables a smooth ramp up of peak pressure in an "blown out" cartridge. The short norma bullets don't seem to suffer any from a short COL compared to Weatherby's own ammo (though Norma makes them both). I'm beginning to think I just might get suckered into buying one of these the more I explore them. Their recent 6.5-300 looks mighty interesting though the selection of bullets that can hold together out of it I imagine is limited.

[stagpanther]

Almost done working on my friend's 300 WBY mag. It's almost a new gun. In case you're wondering, I marked his former LOP/eye relief reference on the scope body prior to going to work. I had to buy two sets of new bases and rings, mostly cause the newer standard MK5's have a different front base screw measurement from his older magnum one. Nobody I use had the dual dovetail extra-high rings (have to use because of 56mm front objective) in stock, so I had to use the standard "adjustable windage" ring for the rear. An engineer at Leupold told me they can take the punishment from the 300 WBY mag. Maybe, but I still think dual dovetail bases and rings are the better way to go.

The old base rear actually had the screws over-driven--they were binding the bolt somewhat. I used the shorter screws and now the bolt floats effortlessly into the receiver. After mounting the rings I hand-lapped them for alignment for the 30mm scope body. My personal 30mm scopes slid perfectly back and forth when I tested them, but my friend's Trijicon accupoint binded a bit, not a good sign since that might be a sign that it's body had been distorted in the previous mounting. I also leveled and took out the cant. I did a quick 3 shot test at 300 yds yesterday and using Weatherby ammo I was right at MOA--a vast improvement from the previous set-up, but I'm still not quite satisfied. I'm going to mount a bubble level on the scope to see if that helps. This older model ultra-light (no brake/compensator) is a handful under recoil, so it has a propensity for muzzle-flip for such light weight. I hate the side-bulging cheek weld pad molded into the stock though.

If there's one thing that impresses me about this rifle (other than the power of the cartridge) it's the unique in-line 9 lug bolt--that is truly a thing of beautiful engineering.

[natman]

If I had a 300 Weatherby, I'd want somebody else to sight it in for me too.

[Pat T]

One thing you could try too is to decopper the barrel. If it's gone 200 rounds without this I bet it's full of it!

[stagpanther]

One thing you could try too is to decopper the barrel. If it's gone 200 rounds without this I bet it's full of it!

Absolutely, I spent half a day and filled up half a trash can with patches dredging copper and deposits out of the barrel--the lands especially were filled with crud. The owner felt something might be wrong with the barrel but I told him most likely not.