Sierra 175 Matchking and Re-15

[allaroundhunter]

Hey guys, quick question regarding use of the above mentioned components. My Sierra manual lists the max charge at 41.3 gr, but my Lyman manual has it at 44.3 gr. This (to me) is a large difference in max charge and I am actually thinking that the Lyman manual is more correct and here is why. The Sierra manual has the charge data for the 175 HPBT, 180 gr SPT, 180 gr SBT, 180 gr HPBT, and 180 gr RN all clumped together. I feel like this would cause a much more conservative list of max charges since they are going with the "one charge fits all" type of thing.

Y'alls thoughts?

 

[billymarr]

barely less then 10% so work up slowly.

 

[USSR]

While you don't mention the cartridge, I suspect it is .308 Winchester. If so, then the use of different brass used in load testing accounts for some of the difference, in addition to Sierra's load data being extremely conservative. I have found Lyman's load data to be very dependable.
If you are using Winchester brass, you may very well be able to go up to the 44 grain load. Unless you are using military 7.62x51 brass, I would suggest starting at 41 grains and working up from there.

Don

 

[allaroundhunter]

Don, it is indeed a .308, I apologize for not mentioning it. I am using federal brass, not any military stuff.

I fully intend to start low around the 40 gr range and work my way up while checking for pressure signs. I was just surprised by the large difference between the two manuals.

 

[Jim Watson]

I am loading 175 SMK (and 155 Scenar) .308s with Varget rather than Re15, but just as a guideline; I am over Sierra's maximum but below Lyman's.

Speer used to show three load levels rather than the usual two. I never had any trouble with the middle load which was 95% of the maximum.

Federal rifle brass has a reputation for being softer than other brands. I would load it conservatively.

 

[velocette]

All Around Hunter;
Sierra uses Federal brass for their load development and load recommendations.
Federal brass is the heaviest of all the .308 brass that I have weighed. This includes MIL spec brass from Lake City and other Nato spec brass.
What this all means is that Fed brass will have the least internal capacity of any of the brass you are likely to find. That means that Fed brass will take the least amount of powder to attain maximum pressures. It also explains Sierra's reputation for being conservative with their load data. It is conservative especially if you are not using Fed brass.
In my experience, going from heaviest to the lightest .308 brass:
Federal / Lapua / RP & LC / Win / Hornady.

Roger

 

[stubbicatt]

Double check the manufacturer of the brass each data set was developed on. That may explain the discrepancy.

FWIW, I have found that 43.3 grains of RL15 and 175 Match Kings in "palma" brass by Lapua works really well. It also works with the large primer Lapua brass, without presenting any pressure signs.

 

[allaroundhunter]

Double check the manufacturer of the brass each data set was developed on. That may explain the discrepancy.

Sierra uses Federal brass (as was previously stated) and Lyman used Remington brass. Would that explain an almost 10% difference in max charge?

 

[dprice3844444]

don't forget to always use a chronograph while working up loads if possible

 

[USSR]

Sierra uses Federal brass (as was previously stated) and Lyman used Remington brass. Would that explain an almost 10% difference in max charge?

Not entirely. As I stated previously, Sierra is extremely conservative with their load data. I called them once to question the pressure level of one of their so-called "Max" loads, and they told me they didn't know what the pressure was and, "that's just where we decided to stop".

Don

 

[allaroundhunter]

While I don't exactly like that approach, I guess it explains the results that are in my load book

 

[stubbicatt]

There are manufacturers of piezo electric pressure testing equipment in which you glue a small strain gage over the chamber of your rifle, and once properly calibrated, will be very helpful in determining your max loads. I have one of these setups, and used it years ago, to arrive at what is max in my rifles. It has its limitations, the one that bugged me the most was the sacrificial cartridge case which one cut at a precise location and then measured with a ball micrometer in order to properly calibrate the thing.

I realize mine is an arbitrary and probably way too imprecise method of determining max charge weight, but once I became comfortable working with the strain gage setup, I weighed the sacrificial case, and made a note of it. With each subsequent lot of brass, I will weigh and average 10 cases, and compare that weight to my sacrificial case, and arbitrarily adjust my max loads up or down by that percentage if I am using the same lot of powder.

If a new lot of powder I simply use the old calibration factors, and use a case that weighs within 1/2 grain of the sacrificial case to get a max load with that new lot of powder.

It works for me, but it may not work for you.

 

[USSR]

I have one of these setups, and used it years ago, to arrive at what is max in my rifles.

Yes, there is no absolute Max, there is simply the reasonable maximum in each particular rifle with each particular load. And here is something else to think about. First, factory ammo is never loaded to SAAMI maximum pressure levels. This is one reason why handloading can improve performance by bringing a round up closer to the SAAMI maximum pressure level. Second, there is a built-in safety margin in modern bolt action rifles, which is greater when rifles are chambered for certain cartridges. For example: two identical bolt action rifles are chambered in .270 Winchester and .30-06. The .30-06 rifle has 5k psi more pressure leeway built into it than the .270. Why? Not because it needs it, but simply because the .30-06 is a 60k psi round while the .270 is a 65k psi round. When I was shooting in LR competition, I brought my .30-06 loads up to the 59k psi pressure level. When I switched over to shooting the 6.5x55, I greatly exceeded the listed SAAMI pressure specs for that cartridge. Why? The 6.5x55 is deliberately down loaded in deference to the many old Norwegian Krags and small ring Mausers still out there, and I was shooting a strong, modern rifle for which cartridges with higher pressure specs are available. I approached load development through a combination of using Quick Load software, a chronograph, and by examination of my brass for pressure signs. Please understand, I am not advocating exceeding published "Max" rifle loads, in most cases it is not necessary. I am simply saying that a Max load will vary from one rifle to the next, and this is how I approached load development to find the Max load for my rifles for a specific purpose,

Don

 

[allaroundhunter]

Thanks for the help, everyone. I am fairly new to reloading, but I am quickly realizing that my reloading manuals are guidelines as opposed to law. I'm always checking for pressure signs, and as I work up this load I won't worry too much going over the book max so long as I'm not getting any signs of an overpressure. But yes, as I approach book max and exceed it (if I do), I will be increasing my powder charge by minimal amounts... Just to be safe