Huge manual discrepancy

[Kachok]

Reading through the online Sierra manual I ran across the powder/bullet combination I already use for my 7mm-08 (47.5gr Big Game, 140gr SGK, 2.800"), but according to Sierra I am running almost 5 grains over max!!! http://accurateshooter.net/pix/sierra708.pdf
I worked up from Noslers data, http://www.nosler.com/7mm-08-remington and I had no pressure issues with the SGK which has a similar bearing surface area.
Anyone know what could cause such a huge difference in data? Is there any chance I am crazy overpressure without any hint of a sign?

 

[ArchAngelCD]

If you go to the Accurate load data base they list a 140 BARNES TSX bullet with a max charge of 46.5gr Big Game w/COL of 2.800". I don't know where you got your charge weight but it's even a full grain over the data provided by Western.

Have you ever checked the velocity generated by your load?

 

[Otto]

A 10% variance between manufactures isn't huge or uncommon.
But it's advisable to follow the data from Sierra if you're using their bullet.

 

[ArchAngelCD]

A 10% variance between manufactures isn't huge or uncommon.
But it's advisable to follow the data from Sierra if you're using their bullet.

I agree...

Where did you get the load you are now using?

 

[Kachok]

I could not find a Sierra Manual so I worked up from Nosler 140gr load data. Same weight similar bearing surface area as a 140gr Ballistic Tip. Have not chronoed that load yet, estimated around 2850fps.

 

[steve4102]

If you go to the Accurate load data base they list a 140 BARNES TSX bullet with a max charge of 46.5gr Big Game w/COL of 2.800". I don't know where you got your charge weight but it's even a full grain over the data provided by Western.

Not really, as the Barnes all copper bullets usually have their own data specif to copper solids.

If you look one line above the 140gr Barnes bullet you will see a Hornady 139gr Hornady SP cup-n-core bullet. This data list a Max charge of 48gr BigGame. A much better match then the 140gr Barnes All Copper Bullet.

One thing you may not know about Sierra and how they obtain their load data. Unlike all of the powder manufacturers and some of the bullet manufacturers, Sierra does not have any "Pressure Testing" equipment. They test their loads in regular firearms with not pressure device and determine max loads the old fashioned way, they read brass and guess. Don't lose any sleep over Sierra data, it is not pressure tested and should be taken with a huge grain of salt.

I think your 47.5gr load is fine, if it's accurate and you are not seeing loose primer pockets after 4-5 firings you are GTG.

 

[ArchAngelCD]

Well, you are correct Kachok...
The current Nosler load data online lists all their 140gr bullets with a max charge of 47.5gr Big Game. http://www.nosler.com/7mm-08-remington

I don't know what to tell you but before I change anything I would for sure send those rounds over a chrono and see if the velocities are too high.

 

[Kachok]

Who does use actual pressure testing equipment in case I come across such an issue in the future?

 

[Kachok]

Well, you are correct...
The current Nosler load data online lists all their 140gr bullets with a max charge of 47.5gr Big Game. http://www.nosler.com/7mm-08-remington

I don't know what to tell you but before I change anything I would for sure send those rounds over a chrono and see if the velocities are too high.

I cannot compare apples to apples because Noslers data is with a 26" tube my 7mm-08 is a 22" so unless I was hitting 3k fps I would have a hard time saying if anything was out of place.

 

[steve4102]

Ramshot data with Hornady bullet and 48gr BigGame is 2842 with a 24 inch barrel @ 56K psi. QL suggests your load with 22 inch barrel and 47.5gr should be about 2750-2780fps.

 

[steve4102]

Who does use actual pressure testing equipment in case I come across such an issue in the future?

All the powder manufacturers and Lyman use pressure testing equipment and list actual pressures.

Nosler has a pressure lab, but does not list pressures.

Speer also tests with pressure equipment and will not list pressures.

Hornady has some pressure barrels, so some of their data is pressure tested and some is not, it depends.

Lee has no lab or any real data, they borrow all their data from the Free Powder Guys data and repackage it and sell it.

Barnes has a pressure lab.

Duno, about the rest.

 

[ArchAngelCD]

I cannot compare apples to apples because Noslers data is with a 26" tube my 7mm-08 is a 22" so unless I was hitting 3k fps I would have a hard time saying if anything was out of place.

Yes I understand that but I'm not talking about small changes, I'm talking about something that clearly stands out which would happen if you were overpressure. If the ammo shot in your 22" barrel is generating more velocity than Nosler is reporting from a longer barrel something is not right, that's what I mean...

 

[Grumulkin]

I'm with Sierra; I also test pressure in the old fashioned way. It's hard to believe though that a manufucturer of bullets does no pressure testing with tranducers, pressure barrels, etc. I guess I'm glad I've never bought or even looked at their manual.

That said, I've run into more than one situation with widely varying recommended loads with the starting load in one manual being over the maximum load in another manual.

Regarding Barnes bullets; in the several cartridges I've loaded them in, there is little or no difference in the best powder charge between them and a variety of other traditional copper jacketed lead core bullets. That includeds both the TSX and the Banded Solids.

 

[Otto]

One thing you may not know about Sierra and how they obtain their load data. Unlike all of the powder manufacturers and some of the bullet manufacturers, Sierra does not have any "Pressure Testing" equipment. They test their loads in regular firearms with not pressure device and determine max loads the old fashioned way, they read brass and guess. Don't lose any sleep over Sierra data, it is not pressure tested and should be taken with a huge grain of salt.

Not quite. Yes, Sierra doesn't have their own pressure test fixtures. But they hardly publish maximum loads based on guesses and brass reading.
All of their loads using their bullets are verified by a third party namely Hodgdon.

 

[ArchAngelCD]

Since most times something below the Max charge weights will deliver the best accuracy I have a feeling that's why bullet manufactures load data is usually slightly lower than other sources. The bullet makers want to be known for accuracy so buy publishing the most accurate data they get what they are looking for. Of course this is just speculation on my part but it sounds reasonable.

 

[Kachok]

Well according to Nosler the max load of 47.5gr of Big Game IS the most accurate load and my 7mm-08 agrees completely, that is one of only a handful of loads that my Browning likes, the rest all involve H380.

 

[Master Blaster]

Sierra is using a federal MAGNUM primer, and Nosler is using a winchester large rifle standard primer. Unless I read it wrong, that is the difference in load and pressure.

 

[Kachok]

Yeah but there is not 5gr of difference in the primer not even close, general rule about magnum primers is 5% increase max.

 

[steve4102]

Sierra is using a federal MAGNUM primer, and Nosler is using a winchester large rifle standard primer. Unless I read it wrong, that is the difference in load and pressure.

Sorry, but you did read it wrong.

Sierra #5 list the primer to be Federal 210M. The 210 is their standard large rifle primer, the "M" stands for Match. Federal large rifle Mag primers are #215 and 215M.

Not quite. Yes, Sierra doesn't have their own pressure test fixtures. But they hardly publish maximum loads based on guesses and brass reading.
All of their loads using their bullets are verified by a third party namely Hodgdon.

Not quite. From Sierra.

Hi Steve,

Thanks for the email.

I’d guess we might get a manual finished in the next two years but there is no time table in place at this time.

We shoot all our loads in real guns and read pressures just like you do so there are no hard and fast numbers to publish.

That might all change in the future. Powder companies need to know the pressures for their product while actually all we try to do is provide safe and accurate information generated with our bullets when we do a book.

JB of Handloader/Rifle Magazine has said that Sierra has been known to send a few rounds off to Western Powders for testing, but only a few, it is not a regular practice.