Sierra's numbers a bit conservative?


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sam700
November 27, 2010, 05:50 PM
I recently started using Varget in my .308 with 168 grain sierra match kings. According to the Sierra manual, the max load for varget is 43.5 grains with a 168 grain SMK. I noticed that 43.5 grains is very conservitive compared to some of the other 168 grainers I致e loaded. According to the chronograph, I知 getting an extreme spread of 70 fps with this load which leads me to believe that the load might be too light. By going up to 44 grains, the extreme spread goes down to 50 fps, but I知 hesitant to load it any hotter. I知 curious as to why nearly all other bullet manufactures publish heavier loads for the 168 grainers. I知 wondering if there is something special about the smk痴 (more bearing surface?) that require a lower powder charge or if they put out overly conservative numbers.

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Sediment
November 27, 2010, 05:55 PM
Is it a hollow or flat boat tail bullet? Little bit sleepy and my memory is powering down.

tkcomer
November 27, 2010, 06:08 PM
While I can't vouch for Varget as its not in Sierra's second edition book, pretty much all the powders that are listed in both books, the newer edition is lighter than the second edition. Some are a lot lighter.

sam700
November 27, 2010, 06:32 PM
It is a boat tail.

W.E.G.
November 27, 2010, 06:38 PM
http://i227.photobucket.com/albums/dd7/rkba2da/reloading/too-hot1.jpg

http://i227.photobucket.com/albums/dd7/rkba2da/reloading/too-hot2.jpg

Sediment
November 27, 2010, 06:42 PM
From the Hornady book, yes I know it's not Sierra but my it helps for some perspective.

165-168gr BTHP #30501
Varget Minimum 32.6gr @ 2100 FPS, Maximum 44.0 gr @ 2600 FPS. Max OAL 2.800"

After looking at your printout the numbers do seem a tad on the conservative side. Maybe they have a Kryptonite core?

W.E.G.
November 27, 2010, 06:49 PM
http://i227.photobucket.com/albums/dd7/rkba2da/reloading/too-hot3.jpg

http://i227.photobucket.com/albums/dd7/rkba2da/reloading/too-hot4.jpg

W.E.G.
November 27, 2010, 06:51 PM
Distinguish the default case capacity numbers for 7.62 NATO vs. .308 Winchester.

Quickload assumes 4 grains less H2O capacity in 7.62 NATO.

Point is, without info about the case capacity of the brass being used here, we are just guessing about pressures.

W.E.G.
November 27, 2010, 06:57 PM
How clever of Hodgdon to mix CUP and PSI standards on their pressure data on their web site.

http://www.hodgdon.com/basic-manual-inquiry.html

http://i227.photobucket.com/albums/dd7/rkba2da/reloading/too-hot5.jpg

USSR
November 27, 2010, 06:58 PM
Sierra's numbers a bit conservative?

Yes, indeed. I called them up once to question a so-called "Max" load. They could not tell me the pressure generated on any of their "Max" loads, and told me that the Max load is simply where they decided to stop. So much for a detailed, scientific analysis.:rolleyes: What is crucial with the .308 more than any other round, is the brass you use. If you notice W.E.G.'s QuickLoad data, it is based on using 7.62x51 brass, which has a much reduced case capacity than some commercial brass. If you are using Winchester or Hornady Match brass (both of which are very light with a large case capacity), you can go several grains higher before reaching the same pressure level as the 7.62x51 brass. This is an advantage when using relatively slow powders such as Varget or RL15. Oh, and I concur with your assessment that the large ES numbers are probably a result of low pressure.

Don

sam700
November 27, 2010, 07:35 PM
I'm using remington (.308, not 7.62X51). So you think that Sierra is listing load data that would be more applicable to milsurp brass with a reduced case capacity?

The Lyman reloading manual lists something along the lines of 45 grains as a standard load. As far as everybody knows, there is nothing special about the match kings such as a greater bearing surface that would require a more reduced load?

kaferhaus
November 27, 2010, 07:44 PM
I work up in .5gr increments until I see pressure signs such as flattened or cratered primers and then back up a full grain.

That load MAY then be temperature sensitive and you'll have to keep an eye on it during warmer temps.

918v
November 27, 2010, 08:04 PM
Sierra uses FC brass to work-up those loads. FC 308 cases have less capacity than Winchester and cannot tolerate repetetive 44+gr Varget loads. If you use Winchester or Hornady brass, you can go as high as 45 grains under the 168.

zeke
November 27, 2010, 08:17 PM
918V-bingo. If memory holds Fed is even heavier (preliminary indication of powder capacity) than military brass. Winchester is about the lightest case commonly available. Alot of differences in loading manuals may be because of brass and primers used. Am also guessing not every single powder and bullet combo is actually pressure tested up to max loads in most manuals? Alot of the loads listed in some manuals, go back in history. Sometimes way back.

Redneck with a 40
November 27, 2010, 08:26 PM
I load military 7.62 brass at around 42 grains of Imr4895, 168 gr HPBT. With Remington brass, I'll go up to 44.5. I'm currently loading some Federal brass, yeah I know it sucks, but I got it dirt cheap. I'm running 43 grain IMR4895 in the Fed brass.

Sierra's data show's 41 grains as max, that's downright anemic in my rifle, 20" barrel.

sam700
December 3, 2010, 11:59 AM
I tried upping the loads a bit and didn't get any pressure sign. I started at 43.5 grains where I had been before, and worked up in 1/2 grain increments till I got to 45.5 grains. When I got to 44.5 grains, I noticed that I got an extra 100 fps over 43.5, but my groups opened way up to about 1.5 MOA. When I got to 45.5 grains, my groups shrunk back down to 1/2 MOA.
After I got that initial velocity bump at 44.5, I didn't notice any significant change in speed.

I really didn't get any improvement in extreme spread as it stayed at roughly 50fps throughout the test. I see that Hodgdon publishes a 168 grain load that goes up to 46 grains. Any chance that if I work up to 46, I may get a better spread?

918v
December 3, 2010, 12:16 PM
It's up to you, but mind your primer pockets because they will loosen-up if you load this hot. BTW, does your bolt lift feel the same as with factory ammo? What pressure signs are you looking for?

Howard Roark
December 3, 2010, 12:27 PM
Bore diameter and type of rifling also affect pressure.

Clark
December 3, 2010, 12:34 PM
I find that Quickload is right on the money predicting Varget pressure and velocity.

I don't always use load books, but when I do, I prefer Sierra.

sam700
December 3, 2010, 01:00 PM
bolt lift feels normal, but it is cold out so we'll see what happens in the summer. Still, if I don't get the es to settle down, I won't be using the load by that time.

I'm looking mainly for cratering and a hard bolt lift. I haven't gotten either. I noticed that at 45 grains, I got a little shiny spot on the case head from the extractor.

The question is why Hodgdon publishes 46 grains as the max for a standard 168 and Sierra publishes 43.5. Is there something unique about the match kings that requires a lighter load?

USSR
December 3, 2010, 01:34 PM
The question is why Hodgdon publishes 46 grains as the max for a standard 168 and Sierra publishes 43.5. Is there something unique about the match kings that requires a lighter load?

See my previous post:

I called them up once to question a so-called "Max" load. They could not tell me the pressure generated on any of their "Max" loads, and told me that the Max load is simply where they decided to stop.

There is no scientific basis to their so-called "Max" loads. There is nothing unique to their MatchKing bullets, they are simply a conservative company.

Don

R.W.Dale
December 3, 2010, 02:20 PM
I don't always use load books, but when I do, I prefer Sierra.


LOL I read that and instantly thought of 'the worlds most interesting man" or handloader anyway. I assume that was pun intended.

Can I sig quote you on that??

Clark
December 3, 2010, 02:24 PM
I have experience working up to a loose primer pocket in cartridges that have Mauser case heads with large Boxer primer pockets:
Examples: 22-250, 243, 6mm Rem, 250 Savage, 257 Roberts, 25-06, 260 Rem, 6.5x55 [US brass], 270, 7mm-08, 7x57mm, 280, 300Sav, 308, 7.62x51mm, 30-06, 8x57mm, 338F, 358, and 35W.

If I find the threshold of loose primer pockets, and then back off a safety margin, there is my load. Vernon Speer said 6% powder charge safety margin in 1956.

I can go for a little less than 6% safety margin.
Sierra, when I compare, seems to go for a little more safety margin than Vernon, but their loads do seem to be reality based.

I own ~ 50 load books, and some brands of load books max loads go up and down over the years like the stock market.

Contrast that with Sierra load books.
They never change their loads.
And they probably will not change, as long as powder and brass manufacturers keep making consistent products.

Besides Sierra, who else makes reality based load books? Ackley?

USSR
December 3, 2010, 02:55 PM
Besides Sierra, who else makes reality based load books? Ackley?

If I were to pick only one reloading manual, it would be the Lyman 49th Edition. The problem with reloading manuals printed by powder companies is - their loads only use their powders. The problem with reloading manuals printed by bullet companies is - their loads only use their bullets. In addition to providing loads using bullets and powders from various manufacturers, Lyman also provides load data using lead bullets, although only those cast from Lyman moulds. Oh, and their loads are reality based.

Don

243winxb
December 3, 2010, 03:49 PM
I noticed that at 45 grains, I got a little shiny spot on the case head from the extractor.

High pressure sign from the ejector. Is there something unique about the match kings that requires a lighter load? I知 wondering if there is something special about the smk痴 (more bearing surface?) The difference might be in the bearing surface and/or the jacket thickness. There are tools to measure a bullets bearing surface.

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