Spike Camp
Weatherby Nation => Around the Campfire (General Discussion) => Topic started by: grizzly340 on July 31, 2018, 03:33:02 PM
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After realizing my velocity in my 7mm mag isnt what I thought with the 160 gr. Bullet I started looking at the load density's and noticed alot of them were in the 80% and some high 70' % full range. And when compared to the 7mm Weatherby load density's where some were 101% and A 103% full . I am like what the heck is the reason for that.
Turns out that all the other 7mm Magnums have 65,000 psi and the 7mm Rem. Mag only has 61,000 psi. Does any one know why that is. Im feeling jipped here.?
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One of the reasons I have read about is because of the wide difference in case capacity of the 7mm Rem Mag case. It can measure up to 10 grains different between lots and different makers. How true that is or not I do not know. Or why there should be such a huge internal case difference compared to all other cartridges.
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This is something l have never really understood
How does one caliber have a different max working psi than another. Unless they are adjusting for types of rifles and actions it was designed for.
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Some of us old folks remember when the 264 Win Mag came out. It wasn't long before it was deemed "A barrel burner". A few years later the 7mm Rem Mag came out. My guess is that Remington did not want a "barrel burner". The method widely used at that time for testing chamber pressure was CUP (copper units pressure) and had huge variations in pressure readings. The 243 Winchester has/had the same issues. May not have any bearing in the matter, but if you look at chamber pressures for the 6mm Creedmoor and the 243 Winchester you will find the 6mm Creedmoor to be significantly higher, and the 243 Winchester is usually loaded a few thousand PSI below its maximum in factory ammo. That is how the 6mm Creedmoor creates more velocity with less case capacity. The only 7mm magnum older than the 7mm Rem. is the 7mm Weatherby mag and Roy wasn't publishing pressure data, He was just building them strong enough to do the job. Powders available at that time may have something to do with it as well. But heck I'm just old and forgetful.
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The 7mmRem was designed back in the 1950s when Winchester came out with the 338 Win which is the parent case and at the time was wildcat so SAAMII kept the pressure low since there was all sort of different chambers in rifles.
Remington made it legal around 1962 but don't quote me on the dates because I may be off a year or two.
You can load it up to 65Kpsi in a good solid action just like any other magnum.
I have no problem getting 3000fps with a 160gr bullet out of my M70 7mmRem with a 26" barrel and could push it harder but not interested in doing it since there isn't much that will stand up to a 160 at 3000fps.
so I don't feel slighted at all and my case life will be longer then those 65kpsi bruisers. :)
( edit for spelling ;D)
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Some of us old folks remember when the 264 Win Mag came out. It wasn't long before it was deemed "A barrel burner". A few years later the 7mm Rem Mag came out. My guess is that Remington did not want a "barrel burner". The method widely used at that time for testing chamber pressure was CUP (copper units pressure) and had huge variations in pressure readings. The 243 Winchester has/had the same issues. May not have any bearing in the matter, but if you look at chamber pressures for the 6mm Creedmoor and the 243 Winchester you will find the 6mm Creedmoor to be significantly higher, and the 243 Winchester is usually loaded a few thousand PSI below its maximum in factory ammo. That is how the 6mm Creedmoor creates more velocity with less case capacity. The only 7mm magnum older than the 7mm Rem. is the 7mm Weatherby mag and Roy wasn't publishing pressure data, He was just building them strong enough to do the job. Powders available at that time may have something to do with it as well. But heck I'm just old and forgetful.
Well there was one know one talks about much and that is the 7mm Mashburn also known as the 7mm-300 Win.
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Nothing to add except thanx grizzly340 for asking this question, I never noticed that, and also to those that responded.
I'm a huge 264Win Mag fan. Was in the market for that when I stumbled across the 257 Weatherby.
truck driver 2... I pride myself with (while not owning) at least knowing a little about most rifle calibers but you put a new one on me with the 7mm Mashburn.
It's time to do some web searching...
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I have always found 7mm Rem load data mild, most of my loads where above book data. ::)
Rob
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There is certainly some conservatism in the reloading data. I haven't gone on an extended search, but I am told that some of the data from the past was a little "warmer" than the loads presented today. That said...the powders are not the same as those in the 1960s...even formulations of the same powder have changed.
Realize...Weatherby cartridges utilize free-bore, so they run at a little higher pressures. The pressure spike is lower prior to the bullet engaging the barrel lands.
I look at it this way...I shoot magnum cartridges so I don't have to load them extremely hot. My father used to run some really hot loads in his 6.5-06 to keep pace with my .264 Win Mag, but he was definitely loading above any published data. If you shoot a magnum cartridge, you don't have to do that and you're still getting excellent performance.
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This is one of the better questions. Here's another one take a 30-06 built in 1906 with an max pressure of 60,200 psi, then in 1925 the 270 win was born utilizing the 30-06 case and it's max pressure is 65000 psi then jump to 1957 and the 280 Remington based again on the 30-06 but it's max pressure is 60000 psi. Of course I highly doubt anyone was using electronic transducers reading in PSI at the time, and as we all know CUP was the standard of the of the day. This leads to issues in and of itself and that's based on how the ballistic tech interprets the reading/data, how well the test was conducted and down the road in the future how accurate was the cup to psi conversions. ??? I almost think it's not totally based on the brass case itself , but other factors and about the only way to know for sure is find some history buff to answer the question OR call a bunch of ballistic techs from the different powder & rifle companies and see how many different answers we get. There is absolutely no doubt cartridge cases in the same caliber from different manufacturers have different cases capacities depending upon the manufacturer, some actually are the same case capacity, that leads to another issue who actually made the cases and who put their head stamp on them ? No every ammo company makes their own cases a lot of this stuff is farmed out. The same thing with powders there are at least 3 powders out there that are duplicate with another companies name on it, not similar , not like, they are the exact same powder with someone else's name on them. Wyoming is correct some powders have changed slightly thru the years. Yes some powder charge loading have decreased thru the years, and I almost bet some powder charges have increased. Those old manuals from the 30's are interesting reads.
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When Roy Weatherby developed his first magnums the slowest burning powder readily available was IMR-4350. There was a big war going on, so that may have played a factor in what was available. I don’t know what slow burning powders were available when Remington’s 7mm mag was developed.
As was pointed out, the freebore helps keep pressures lower with Weatherby cartridges while still getting great velocity across bullet weights. A gunsmith described the 7mm Rem chamber as being choked when compared to the 7mm Weatherby.
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+1 Zonie. It is fun to look at the old load manuals and see the changes. My dad started me reloading in 1964 and the oldest manual I still have is the Speer #7 dated 1966. The load data for the 7mm Rem Mag 160 gr. spitzer using 64 grains IMR4350 (max) gets 3102 FPS. The 7mm Wby with the same bullet using 65 grains IMR 4350 gets 3110 fps. The max load for the 7mm Wby. of IMR 4350 is 67 grains gets 3201 fps. I like the little history notes of that time period.
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There are some caliber's that the psi was keep low for one reason or another. The 6.5x55, 280 Remington, and the 7 mm Remington
Also some manuals are mild like the Berger manual, and some are hot, l have a old Lyman manual that l have never reached their max with any caliber or load
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Nothing to add except thanx grizzly340 for asking this question, I never noticed that, and also to those that responded.
I'm a huge 264Win Mag fan. Was in the market for that when I stumbled across the 257 Weatherby.
truck driver 2... I pride myself with (while not owning) at least knowing a little about most rifle calibers but you put a new one on me with the 7mm Mashburn.
It's time to do some web searching...
Slide over to the Nosler Reloading Forum and search it. There is a good bit of interest in it over there.
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Contacted Remington thinking since they designed the cartridge they might be able to help. No luck. :o Response below:
The chamber pressure specs are set by SAAMI and these are the specifications we adhere to in production. We are unable to offer up a reason as to why one round has a specific pressure that is different than another as these standards are not set by Remington.
Thank you,
Remington Consumer Services
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I was digging to and I found something along what Chet was saying and I think Wyoming mentioned spikes. This says that for unknown reasons the 7mm rem. mag along with the .243 win. Are prone to spikes in pressure and on the side of caution there psi are lower ??
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Dano thanks for checking, Remingtons reply was about as I would expect. This begs the question who actually is saami and are they regulated by federal law ? My understanding correct me if I'm wrong companies do not have to be a member of saami. This is where I have some questions do the saami member companies set guidelines and standards for all member cartridges, OR does the member company set the standards for their cartridges and then submit to saami for testing ? I almost bet it's the latter, and I doubt they are regulated by federal laws ?
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I think the sponsoring company sets the limits and submits it for testing.
Example: the 416 Remington is loaded to a much higher pressure than a 416 Rigby but the Rem has lower muzzle velocities. Nosler’s recent cartridges based on the 404 Jeffrey case are at a much higher pressure than the .423 caliber was designed for. I believe it was Dubyam who said to get the velocities they were after Nosler pushed the pressures way up. It’s simple physics. Remington and Nosler squeezed out what they could from the limits of the case in a modern action.
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To follow up on Zonie's post, Who is Saami?
https://en.wikipedia.org/wiki/Sporting_Arms_and_Ammunition_Manufacturers%27_Institute
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These old Weatherby load data sheets I emailed some of you years ago have the avg. breech pressure for each load side by side with the other data. I wish every body did that. But it does add more questions for me on page 2 it says that loads at or over 55,000 p.s.i. should not be used and are for reference only. and I believe them because I missed that part and loaded the 84 grains of 4350 in my 300 wby. and the bolt wouldn't open. so those got pulled.
but anyway if all these loads are not tpo exceed 55,000 p.s.i where does the 65,000 p.s.i. or even 61,000 p.s.i. come into play ??? or are we not talking the same p.s.i. ??
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Ah, the days of litigation where the only winners are the lawyers! ;D
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I believe the 55.000 psi you are referring to is actually 55.000 cup not psi,as mentioned before a lot of production bolt action rifles have no freebore in the 7 rem mag chambering which imo accounts for some pressure spikes that were mentioned previously and the second thing that I think comes in to play is the wide variety of action types it is chambered in especially the auto loader which cant handle as much pressure as the bolt action,not surprised that Remington pleaded the 5th but as the cartridge designer if they don't know the reason then nobody does