I've posted this in the Medium Bores forum also, so Moderators bear with me.

I know there are a couple of you guys out there that have performed extensive research and reloading on this cartridge and I've been loading this cartridge for about two years now. A friend of mine and feloow AR poster suggested and with good reason, that some of my loads might be to hot, so I solicit your opinion on the following:

Weatherby has waxed and waned on their advertise velocity for the 250gr offering throughout the years. Originally, they touted an MV of 2850 fps at about 50k PSI. This data was published in their old 'Weatherby Guides'.

Ove the last few years however, they've bumped up their advertised velocity to an even 3000 fps with their factory loadings. When I bought my Accumark, I started loading using their recommended 84.9gr of MRP at an advertised 2850 fps and about 49,600 average breech pressure. I also tested their factory offerings and they produced velocities in the mid 2900s and very accurate.
Well my stated loads above came in at a SCREAMING 3022 plus FPS with great standard deviation and zero pressure sign that I could tell, other than velocity of course which is an indicator of pressure of course if the speeds are too high. Barrel is a 26" Krieger factory.

So, my question is this, given the fact that Weatherby advertises 3000 fps and my loads show no visible pressure signs (loose primer pockets start at about the 5th or sixth reload), is the aforementioned load too hot? thanks, jorge

The only real way to tell is to fire tell in a barrel set up with a strain gage, piezo unit and see what it says.

If the data you are useing says 2850 is the velocity at a certain PSI and you are useing the components they used - Lots change, I know, but a WLR primer is a WLR primer for most intents - and you are almost 200 FPS faster, I`d be real suspect of the load. Especially in a barrel that likely isn`t as tight as the SAAMI spec barrel used to develope the data. You can`t get velocity without pressure and if one is higher then is expected likely the other is also.

I`ve a 270 Win that drives 140 gr bullets at over 3000fps with starting to middle of the road charges. I used a strain gage on it and found the pressures were right at the psi readings I found with factory ammo or a little above. I am happy with the load and feel quite sure that it`s safe, but I won`t raise the charge even though the book says I can add 4 more grains of powder.
The load was 55.0 gr of R22 with a win case , WLR primer and 140 SST at 3035 fps avg for 10 rds. The Hornady manual shows the same bullet with their case and same other components as giveing 2700-2800 fps with 54.5/56.2gr.

MY favorite load for my factory wby 340 is 88 grains of 7828 under a 250 partition. This gives me 2930-2950 and no signs of pressure.
I've hit the speeds you talk about without much signs of pressure except slight extractor marks.
That being said I would say that you have definately hit the max. I had an experience in AK with my 340 years ago with my 340 with the load above. It rained for 3 days straight and I got some water in the barrel (unknown to me..but should have known better). There was no game in the area...and after 3 days of boredom I decided I had to shoot at something and picked a lily pad bud in a pond about 200 yds below me. I took the shot and then found out I could hardly open the bolt. It wouldn't have been a good deal in a dangerous situation.
I guess it taught me to be a better "manager" of my firearm in the field and it was also a lesson that when you run near max pressure in poor field conditions you can also be heading for trouble.
My experience with weatherby factory ammo is it gets darn close to advertised velocity but not quite. I doubt that if we could send the ammo back to the factory for reloading that it would survive more than 5 reloads without the primer pockets being "gone". I would say that alot of the WSM stuff I've seen wouldn't go more than 3 factory loadings!! Not sure if I've answered your questions but but I don't think you are exceding what the factory does for loads/pressure/speed.

quote:

Not sure if I've answered your questions but but I don't think you are exceding what the factory does for loads/pressure/speed

Thanks, Kraky, that is sort of what I was asking. Absolutely zero pressure signs, nt even extractor marks and I can relaod the same brass up to 5X withouth the primer pockets getting soft on me and the fact I tried it in 95 deg temps with o detrimental effects also plays into the equation. jorge

quote:

my loads show no visible pressure signs (loose primer pockets start at about the 5th or sixth reload), is the aforementioned load too hot? thanks, jorge

You've answered your own question. The brass cartridge case is the weak link in the pressure containment system. (That's a good thing, considering you'd much rather it fail first rather than for the action of your rifle to fail first.)

If you consider five firings from a brass case (which will eventually wear out from one cause or another) to be acceptable, then your loads are not "too hot", at least from a safety point of view. In other words, if it takes five firings to expand the primer pocket enough to make the new primer fit unacceptably loose, then there's no way that the pressure of these loads will ever cause the much stronger action to fail.

But considering that if you back off only a couple of grains, your primer pockets might last ten or more firings and your velocity might not suffer more than a few fps loss, you may want to try a slightly lighter load. Also, if you happened to shoot this load under very hot conditions, or with a case that has a small defect, you could find yourself with an inconvenient case failure. So, backing off of a load that results in any discernable primer pocket expansion is probably a good idea.

quote:

loose primer pockets start at about the 5th or sixth reload

This is not .340 specific. Back off your loads until the primer pockets quit yielding. If you run into a soft case you may have no safety margin left.

quote:

Originally posted by jorge:
...I started loading using their recommended 84.9gr of MRP at an advertised 2850 fps and about 49,600 average breech pressure. I also tested their factory offerings and they produced velocities in the mid 2900s and very accurate.
Well my stated loads above came in at a SCREAMING 3022 plus FPS with great standard deviation and zero pressure sign that I could tell,

Hey Jorge, It appears you have been blessed with a "Fast Barrel" on your 340Wby.

quote:

... other than velocity of course which is an indicator of pressure

It might be or it might not be. The problem comes when you rely on it, and it provides mis-leading information. Here is a link to a well written document on Chronographs & Pressure which was written by one of the regulars on this Board. It will provide an excellent insight about "Why" they can be misleading.

quote:

So, my question is this, given the fact that Weatherby advertises 3000 fps and my loads show no visible pressure signs (loose primer pockets start at about the 5th or sixth reload), is the aforementioned load too hot? thanks, jorge

I personally like a few more reloads from my cases, which would mean that I would back off just a bit.

It really depends on how hot the weather will be when those Cartridges will be used. If it will be 50deg-80deg hotter than when the Load was originally Developed, then it "might" just be a bit too hot.

I doubt it will harm the Weatherby, but even if the Load is backed off 200fps, the only one who will know is you. You know as well as I do the animals won't know the difference - as long as you can maintain the fine accuracy.

Well gents, I couldn't stand the suspense so I pulled some bullets apart. Yup, you guessed it, they were hot-loaded to 87.1gr. Guess my balance beam scale was off that day. Max load according to Weatherby is 88grs, so I should be ok now as the rest of my reloads were clocking around the mid 2900s right in line with factory. Thanks for the suggestions. Oh yeah, I crossed checked the loads with my digital. BTW, the trend between the two is the balance beam tends to trhow a heavier charge by about .2 tenths/grain. jorge