100 yards, 25 inch Schneider, 175 SMK, CCI 200, I4064, FGMM 1X brass
Rifle
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Target
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Numbers
41.5 is a great group. 41.2 will win number wise. Really 40.6 to 41.5 all are pretty good.
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now that we have some of the magneto speed variable explained lets get to the OPS question .. about an actual 4064 load...
loading for 308 is by some peoples accounts. .. very easy.. its a forgiving caliber with inherent accuracy.. however since 308 is ubiquitous there are millions of component combinations out there, between bullet shapes, brass manufacturers and case capacities (different capacities even with the same headstamp) things start to get a bit more complicated
since the OP really didn't state much in the HELP department .. lets assume that accuracy is important but since its a tactical rifle I am 'ASSUMING' that velocity is important as well... 175s in a 308 start becoming a reloading challenge for distances past 800m because most loads begin to go transonic there. while the 175 SMK is a good bullet with decent transonic characteristics .. its not immune to instability and its worse with crosswinds than say a berger
so if you want to be at 1k you need velocity to keep you at mach 1.1 MINIMUM and better 1.2 so you are well out of transonic
you are not going to get there from here (at your charge weights) .. you are at the lowest of low nodes using FGMM brass (newer mfg)
on what I call a 70s day .. 70 deg F and 70% humidity a MS velocity of 2700 BARELY gets you to the target above mach 1 so you are already into transonic by then.. and any colder or denser air... and it gets worse
so you need speed.. but speed usually comes at a price, accuracy.. because more speed needs a bigger fire, more gas, bigger explosion, more barrel upset, and the higher the velocity node, the more narrow it becomes in general as far as OPTIMAL CHARGE WEIGHT and OPTIMAL BARREL TIME .. since the bullet is leaving earlier in the upset , the barrel whip is faster with more amplitude and depending on the powder, the pressure curve can get spiky
V
V
| 1000 | 992 to 1008 | -365.3 | -10.1 | 101.5 | 2.8 | 1170.7 | 1.038 | 532.5 | 1.688 | 297.1 | 8.3 |
| 1025 | 1018 to 1032 | -393.7 | -10.7 | 108.1 | 2.9 | 1141.9 | 1.012 | 506.6 | 1.753 | 308.5 | 8.4 |
| 1050 | 1043 to 1057 | -423.8 | -11.2 | 114.9 | 3.0 | 1115.5 | 0.989 | 483.5 | 1.819 | 320.2 | 8.5 |
now.. not saying that it can't be done at 1000 with a slower node... Brad Suave the 2004 nation F-TR champ was using a load that was in the 2600 region but that was when the X ring was twice the size.. now the X is 5" at a grand.. and for that .. any bullet instability puts you out of the game.. worse again if winds are strong.
now if you need terminal effects at distance.. i.e. killing bad guys.. again.. velocity = energy and that is one of the reasons uncle sam has ALWAY loaded high nodes at the expense of absolute accuracy .. M188LR, 77g MK262, MK318, the new MK248 Mod1 300WM is way OVER pressure in any rifle not using the military chamber - all at the edge not the most accurate but will kill at range.
so lets look at FGMM which by the way is made by the same people that have the contract at Lake City military currently ...
FGMM 308 175 comes in 2 flavors now.. both with 175SMK GM308M and GM765M
the GM308 shoots at a lower node than the GM762 and in fact .. having talked to Federal to confirm several years back.. GM762M is over-run MK316 military sniper ammo .. the follow on to M118LR, which has had different powders and recipes over the years...
http://www.snipercentral.com/history-m118-ammunition/
early in A-Stan is was obvious that M118LR wasn't cutting it.. the bolt gun snipers didn't like it because velocity between cold nights on the mountain and hot days saw 200+FPS velocity swings and in the hot summers pressures even for bolt guns were getting high and it was breaking op rods in the newly resurrected SOCOM M14s that were being used ... so Navy CRANE spec's out MK316 .. more velocity with a faster powder that would have better temp stability and function in bolt and semi auto M14 and M110 rifles... MK316 was born
Now in my rifle, a 24" schneider barrel 6 groove, with a VERY TIGHT chamber and short throat, just off the lands of 175smk with OAL 2.86ish (Beasly Plama reamer from PTG) I get PHENOMENAL velocity from FGMM762 ... MS 2765 FPS with SD of 7 and ES of 18 on a 70/70 day with better than .5 MOA accuracy ... remember that is MS velocity . mil spec velocity is 75 FEET down range, not 1" from the muzzle.
The spec sheet that has circulated the web has confirmed that the powder used for MK316 is indeed 4064 although the powder charge they list, 41.x is way too low to get these kinds of velocities and it has been suggested that its definitely NOT canister 4064... for me.. in low volume brass like the FC11 brass of 1x MK316 and old LC85 match brass.. 43.3g of my lot of 4064 gets me to 2780FPS SD 10 and ES of 26 ... holy CHIT thats smokin
Dan Newberry, the 'inventor' of the OCW method of reloading has long suggested this as a node.. on the high side in 'military brass' like LCLR, MK316 (LCXX), and late model FGMM.. all very close to the same weight and volume brass.. you will need more powder to reach that velocity in Lapua and even more in Winchester brass as they have greater capacities..
your 25" barrel length my not be optimal for harmonics... I figure you went with it because the marines used it (until they went 20").. yes.. BUT they BED the action AND barrel.. they bed the barrel 1" in front of the recoil lug ..effectively giving it a 24" beam length.. this has long been a 'standard' for barrel lengths in high power rifles going back to the late 1800's .. probably not by coincidence ...
Also, GM308 is loaded with less powder, about .5g and is at a lower node ~2600 fps last time I used it.. its a more forgiving node, slightly better accuracy across a broader range of rifles.. its a very good GENERIC load but hand loads can beat/match its accuracy at a higher node..
also GM308 is not bullet or primer sealed like GM762, and GM762 is supposedly running a harder primer cup according to Federal
so it really depends on what you are looking for for HELP
if you have a load that groups well, with the MS off and the rifle set up the way YOU intend to shoot it.. AND it has a velocity and SD you can live with that is all that matters...
for me, I take my rifle to both F-Class matches at 1000 for fun (can't compete most guys have rifles that have paint jobs that cost more money than I spent to put my rifle together) and to PRS matches.. so for ME I need at LEAST 2700 at the muzzle with 175s to cheat the wind and stay above mach .. BUT I HAVE TO HAVE a single digit SD and will take 3/4 MOA at 100 with a 5 SD over a .4 MOA load with a ES of 60 because at 1000y a 60fps difference is FEET off the bull down range.. run the numbers in a ballistic calc if you don't believe me... SD is EVERYTHING at range especially with a 308 that is coming down practically vertically at 1000, look how narrow that danger space is in the chart above.. column 2 .. its real narrow...
if you were only going to shoot inside 600 .. perhaps 168 is the way to go bullet wise, the 168 SMK is inherently more accurate in MOST rifles especially 1/12 twist, and at the lower node I have had batches of FGMM 168 (a low node load) that would stack more than not with SDs in the 3-5. a phenomenal load.. and that is the reason most SWAT departments use it... over the 175.. no department in the US would authorize a shot outside 150yards.. so for them its about in close accuracy, not velocity or energy at 1000y .. the difference of a inch is the difference in hitting the hostage not the bad guy
this just scratches the surface...
IT ALL DEPENDS is how I will end it...
