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Going over max on Magnum Rifle

Discussion in 'Handloading and Reloading' started by Trent, Mar 10, 2013.

  1. Trent

    Trent Resident Wiseguy

    I've pushed handgun ammo past max before, on 9mm and 45, but I've never really pushed rifle past max. My theory has always been "whatever it hits won't care if it's going 100fps slower".

    But on a recent test of 300 Win Mag on load development, I found my best load of 26 lots tested, sitting at a charge of 69.8gr of H4831SC w/ 220 gr Sierra Match kings. Sierra lists that as the max charge for that powder / weight / bullet combination.

    I'm seating my Sierras longer than the book, by .108", which gives me a little additional capacity; and that "max" charge doesn't show any signs whatsoever of overpressure. Primers are still rounded on the corners, not set back, no detectable expansion of the web area, etc.

    With the "best" group being at the high end, I'm tempted to push forward to see if it tightens up further. :)

    With the background out of the way, my question is;

    What increment should I use for testing beyond listed max on a case this large?

    1% increments would be about 0.6 gr, 0.5% increments about 0.3gr (rounded down).

    With H4831SC being resistant to temperature changes I'm not nearly as worried about load development in the winter / early spring and shooting in the dead heat of summer, as I would be with other powders.
  2. Trent

    Trent Resident Wiseguy

    Whoops posted in Rifle forum instead of reloading; can a mod move please?
  3. rcmodel

    rcmodel Member in memoriam

    You should be when pushing the envelope that close to the lick'm and stick'm edge.

    You might get a paper cut next summer!

    Resistant to temperature changes doesn't mean immune to temperature changes.

  4. buck460XVR

    buck460XVR Well-Known Member

    Checkin other sources(Hodgdon and Lyman), I found max charges for the Sierra 220gr RN in 300 Win Mag that exceeded your load, but could find nothing anywhere else for the 220gr MatchKings. Most folks figure reloading manuals have a certain amount of "margin of error" figured into the max loads listed. While that may be true, it doesn't justify readily exceeding it just for chips and giggles. Myself, if I was unhappy with accuracy and I could not find a published load showing a higher charge rate, I would try another powder before I went above published loads. But then I wouldn't intentionally load 9mm to over +P+ either.
  5. Kachok

    Kachok Well-Known Member

    Before you start going over max why not try out a couple faster powders. Nosler lists a 220gr Partition in a 24" barrel 300 Win Mag at 2762fps with IMR 7828 and RL22 only 10fps behind, both are slower burning and faster moving then 4831. RL22 is my favorite, and the only powder I have ever used over max charges with, the stuff does not get weird pressure spikes working up, compresses very well, and it burns as slow as a Alabama summer so it is very well suited to very heavy for caliber bullets
  6. Trent

    Trent Resident Wiseguy

    RC; good point. I'm shooting in 40 degree weather with 40 degree ammo, if I work this up to the brink and then shoot it on a nice hot Illinois 100+ degree day, I might be in for a bad time.

    I think I'll load TWO 5 round batches up at .3gr and .6gr over, just to see if the trend continues with the group sizes shrinking. I've got more case capacity because I'm loading a longer OAL than the "book tests", so there's a little wiggle room there anyway.

    Buck; different seating depth and bearing surfaces make it somewhat risky to exchange load listings for bullets. It's not JUST a matter of powder vs. bullet weight. Those bullets have a much different bearing surface and recommended seating depth. The 220Gr RN have a very long bearing surface, but they are "shorter" overall than the MatchKings, so they don't have to be seated as deep. Both of those factors play in to the load.

    Kachok; I've tried H4350 which is a considerably faster powder. However, the results I got were pretty inconsistent. Out of 5, 5 shot groups, I had an average group size of 1.142", with a low of .944 and a high of 1.471. Compared to H4831SC I had an average group size of .989 with a low of .795 and a high of 1.350.

    In ALL tests I've done with this rifle since I got the Krieger barrel on it, I've found a pattern - it prefers either very low or at-max charges. The group sizes grow as you get to the middle point between the two.

    It's very likely I'll end up with TWO loads I like for this rifle, since "Starting charge" and "Max charge" are both giving me consistent sub MOA groups. Meanwhile the exact middle is giving me consistent 1.5 MOA groups.

    The lower of the two loads will be used for practice, easier on the barrel (and me!).
  7. ngnrd

    ngnrd Well-Known Member

    That's certainly a good option. Of course, even 1.5 MOA is plenty good enough for most hunting.
  8. gamestalker

    gamestalker member

    RL22 became new best friend a number of years ago for the 7mm RM. And more recently it has done the same thing with the .270 win. However, it is such a slow burning powder that exceeding maximum published data by more than a tad is impossible, you simply can't get any more in the case.
  9. buck460XVR

    buck460XVR Well-Known Member

    Trent....I know all about bullet profiles, seating depths and bearing surfaces. If you re-read my post slowly, you'll see no-where did I recommend using info for the other bullet. All I said was I found higher charge rates for the other bullet and NO info whatsoever in other sources for the powder/bullet combo you listed. Kinda why I didn't give the powder charge rates.......for fear you might try to use it. Also why I said if I couldn't find a higher published load recipe, I'd try another powder, instead of playing with above max loads. Like the knowledge of bullet profiles, seating depths and bearing surfaces, this is just basic reloading.
  10. Walkalong

    Walkalong Moderator

    Oh yea.

    I retest everything in July/August here where I sometimes record temps over 100 degrees. Some loads that were fine in 50 to 70 degree weather simply are not at those temps.
  11. Trent

    Trent Resident Wiseguy

    Well, I worked up one set at 70.1gr.

    I couldn't do more... because I ran out of that particular lot # of H4831SC, AND I'm out of Winchester Large Rifle Magnum primers. I had enough to build 50 rounds to experiment a little around the high & low end.

    I'm down to my last pound of H4831SC now (diff lot # tough), and have to switch to Remington primers (have 2k of their WLRM equivalent).

    I'm loading a series of proof rounds with the new components later tonight.

    Unfortunately this will probably be it for my 300 Win Mag experiments until components become available. This last pound of H4831SC is the last of the mohicans here, out of H1000, out of H4350. Don't have any other powders that are suitable.

    Frigging shortages are starting to irritate me.

    Edit; and Buck, I didn't mean to sound condescending in my post. I tend to explain myself too much, so there's no mistake about what I mean, and sometimes it comes across as cocky, arrogant, or condescending in print. No ill will intended though. I'm an engineer by trade so I tend to over-explain and over-think things. :)
  12. witchhunter

    witchhunter Well-Known Member

    When I get close, I go .1 grain at a time. One round of each, shoot them 1 at a time and look them over. When I go as high as I can I pull the rest and log that as my max for that rifle. Then check them in August!!! 1 at a time....
  13. Bmac1949

    Bmac1949 Well-Known Member

    Good thread, makes me realize that i have some homework to do before I attempt max loads. That's if I ever need to. what I'm loading now (270, 308 and 30-30) give me the best groups well before I need to load to the max.
  14. Trent

    Trent Resident Wiseguy

    I've never had a best group at Max before with any other rifles..

    Now I've got four different sets of test data on this barrel from four different loads; all showing a preference for the low end and high end of the range.

    So my next two tests are to experiment around upper and lower ends a little, in .4 increments (about .05% increments) to see if I can find a sweet spot. One test will be at current OAL which is .001 from the lands; the second will be .010 from the lands. (Just to see if a minor OAL change makes any difference).
  15. ranger335v

    ranger335v Well-Known Member

    "What increment should I use for testing beyond listed max on a case this large?"

    Trent, no offense is intended but I believe anyone asking that question should stick to the book max, for sure I'M not going to comment on it! But I will say that seating long runs rifle peak pressure up, not down.
  16. Trent

    Trent Resident Wiseguy

    I'm not jamming the bullet in to the lands. I've measured where the lands start (precisely), to confirm the measurements given by Krieger for the reamer they used on my barrel. I have extra space to work with here, this isn't a factory barrel. :)

    That effectively gives me extra case capacity to work with, which doesn't increase pressure; but rather, lowers it. I've fired ammo out of this gun that I had leftover for my old barrel. In the last barrel that ammo was showing flattened / set back primers (74.5gr H1000/220gr MK). That ammo, in this barrel, the primers are still nice, and round, and pretty. Can't even tell which of the brass was at the starting load, and which was the max, after I tumbled them.

    I agree with you if you load long enough to get the bullet up on the lands, you're going to run in to problems; but I'm not. :)
  17. Trent

    Trent Resident Wiseguy

    I will add; To a point; there's the whole free-bore Weatherby trick they used on their rifles, to reduce pressure. But that's cheating. :)
  18. jmr40

    jmr40 Well-Known Member

    What does your chronograph say? When developing loads it is your best guage. If the book says a max load is 64 gr of powder. And that will get 3000 fps, then 3000 fps is your max load, not 64 gr of powder. It is the velocity you are getting that determines chamber pressure. Some guns might need a little more powder to reach the same velocity and pressure than another gun

    I've had some powders reach 3000 fps while still 2 gr below book max. I've had loads that were 50-100 fps below 3000 fps when right at book max.

    The problem with loading over the max powder charge is that while that load may be perfectly safe in your rifle, it might not be in mine. I've seen two identical rifles shoot the same ammo 130 fps different.
  19. Trent

    Trent Resident Wiseguy


    I've seen that in handguns, too. My Springfield 1911 shoots 230gr jacketed bullets 100fps faster than my Glock 21. :)

    I didn't have my chrono out this last trip - was pouring down rain. But this next test I will have it with me.

    After that, I have to work up everything all over again (switching primer brands due to lack of Winchester primers), and will have a new lot of powder (as soon as I can FIND any). In fact, the last lonely 1lb bottle of H4831SC I have is a different lot from the testing I did previously, so I'm re-proofing with it before I shoot any of the hotter loads.
  20. Trent

    Trent Resident Wiseguy

    Oh, my first F-Class match is April 7th, so I'm working under a time limit, too.

    With the component shortage the first match may very well also be my LAST one for awhile. :(

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