More questions about reloading 308 for Ruger American

[Joshboyfutre]

Okay, so I'm new to reloading, relatively new to bolt-action rifles have more experience with semi-automatics, but know my fundamentals, and I'm new to the hunt for sub-MOA. For the record I think people make it sound alot easier than it is to reload and shoot sub-MOA! Not saying its super hard but it sure ain't super easy lol. I'm in the process of finding good loads for different weight bullets. I have two decent loads for 168g & 175g at this point, and I'm getting ready to find out what 155g holds. Once I get that info I'm gonna compare all and pick one. One thing that I think I've misunderstood is ballistic coefficients. For Sierra matchkings the b.c. for 175 is higher than 168's is. That made me think that since I'm getting decent groups w/168 I should get great groups with 175's... Couldn't really see a big difference. Does it only effect range of accuracy or something? I also find alot of conflicting info on load data in different manuals. Sierra only had 41.7g as a max load for varget w/175g bullet. Lee says 42g min... Stuff like that. Is there a best manual for .308? Lastly would like to know what some guys pet loads are using sierra bullets with varget powder for a Ruger American or any other rifle w/a 22" barrel with 1:10 RH twist. Just want to compare notes. Heres what I got thus far-
168 SMK- 43.5g & 46g Varget/O.A.L.-2.830
175 SMK- 42g & 43g Varget/O.A.L.-2.820

 

[splattergun]

ballistic coefficient is a way of measuring how well a bullet cuts wind resistance during flight. It is important after the bullet has left the barrel and is generally most important in long distance shoting. It is only one of many factors that affect accuracy.

Before the bullet leaves the gun there is a different set of factors. Each rifle barrel likes different bullet weights, depending, again, on multiple factors such as rifling twist, barrel shape and weight, harmonics, chamber and throat dimensions and tolerances etc,. Some will prefer a 150 gn, some others a 165 gn, some others a 175 etc.

Before that comes the cartridge, which has it's own set of factors such as case capacity, bullet weight and shape, powder burn speed and other factors. When we learn to reload we also learn to balance all these factors. It is knowledge that is accrued over time and to different levels to meet personal needs.

Before worrying so much about BC, first try to find a bullet weight your gun prefers. YOu might get lucky and hit on a winner rather quickly. 308s seem to have a good reputation with 150s and 165s. But whatever weight you are seeing good results with is where you want to experiment with them. It might take several different bullets before you find the one that's best in your gun, but IMO that is a big part of the fun. FYI< many reloaders find their most accurate loads near the upper end of the data range. But be careful and work your loads up.

As for the different data; the bullet manufacturers produce and test their own data and are generally very conservative (read Lawyered up) in what they will publish.
Lee's data is simply reprinted from various sources, usually powder manufacturers. THe powder makers produce and test their own data, and it is usually a bit higher than what you will get from the bullet makers. I prefer the data taken directly from the powder manufacturer and will cross reference it with other sources.

 

[jmr40]

Higher BCs' equal more aerodynamic bullets. Longer is generally more aerodynamic. It does 2 things and neither have anything to do with accuracy except at extreme range. More aerodynamic bullets retain more speed downrange, hit harder, and can drop less.

It can get complicated when comparing different calibers etc. For example a 200 gr 30 caliber bullet will have far better BC's than a 200 gr 33 caliber bullet. At the muzzle a 338 WM will fire a 200 gr bullet about 100 fps faster than a 200 gr bullet from a 300 WM and have a lot more energy. But at 150 yards the more aerodynamic 30 caliber bullet will be moving at the same speed and with the same energy. At ranges greater than 150 yards the better BC's of the 30 caliber bullet mean more speed, more energy and less bullet drop.

Here is a visual with some loads fired at 200 yards from my 30-06. The top group is 150 gr bullets at 3000 fps. The middle group is 165 Nosler Accubonds with a BC of .475 fired at 2880 fps. The bottom group is 165 gr Hornady Interlocks with a BC of .435 fired at 2880 fps.

The lower BC of the Hornady's resulted in more drop at 200 yards and the impact speeds were 100 fps slower even though they left the muzzle at the same speed. The Noslers were more accurate, but not because of the BC's. My rifle just likes that load a little better. Either load is perfectly acceptable

 

[Joshboyfutre]

Thank you both for very good explanations of ballistic coefficient when it comes reloading. For some reason I had in my head that ballistic coefficient was how stable the bullet that cuts through the air as soon as it leaves the muzzle not so much as it covers distance (almost like turbulence for an airplane). Right now I'm only testing at a hundred yards so I'm just not going to pay any attention to ballistic coefficient until I graduate two longer ranges. As for the varying maximum loads I kind of had a feeling it had something to do with jerks suing companies LOL. Trying to get a sub MOA group with this Rifle has been there most fun I've had shooting in quite a while... But also the most frustration LOL. Reading all of these articles and gun magazines I kind of had it in my head that just pick up a rifle and shoot it and it will be sub moa. Kinda misleading... A lotta work is going into reloading and testing goes into it. I guess I could always just buy match ammo but thats no fun. Thanks again

 

[Rule3]

There are also a whole lot of other variables that pertain to shooting teeny tiny small groups. Not just the powder, bullet COL etc etc. The rifle and the shooter play a big big part.

Have you shot any good factory "match"ammo out of the gun?. Yes, it is expensive but I think worth it for a few boxes just to see.

Forget the Lee data as mentioned it is just copied from somewhere, The Sierra and Hornady, Speer data is good.

 

[Bart B.]

Keep in mind the fact that hand held rifles shoot bullets less accurate than rifles clamped in test fixtures. Us humans do not hold and aim rifles exactly the same from shot to shot. The barrel axis moves around while the bullet goes through it from chamber to muzzle; how much is determined by the amount and direction our bodies move as the rifle recoils before the bullet leaves.

Your groups show how well you shoot that rifle and that ammo. If you shoot test groups with a rifle held against your shoulder as it rests atop something on a bench and they are in the 1-1/2 MOA range at 100 yards, you may have a rifle and ammo that will test about 3/4 MOA clamped in a free-recoiling test fixture.

Benchrest competitors don't hold their rifles shooting their ammo into sub 1/2 MOA groups. Those rifles are resting on bags and untouched by their owners except for one finger touching the 1/4 ounce trigger. The rifle's already been positioned and aimed where desired. It recoils exactly the same from shot to shot. Us humans holding rifles are not that repeatable.

And that being said, some people don't hold rifles as repeatable as others while the bullet goes through the barrel. And nobody holds a rifle perfectly still. But these facts are rarely, if ever, brought up when people discuss accuracy with any part of the shooting sports.

 

[Joshboyfutre]

With federal Gold medal match it shoots around .5 moa, with 168g smk with 46g of varget it shoots.56 moa, & 175 smk shoots .68 moa. I use a rifle rest with a kick plate, and have been shooting since I was a kid. Really upped my game while in the Army though with use of fundamentals. I can shoot an AR from a kneeling position and get 2"-3" groups with Iron sights @ 100yds. I'm not bragging or anything I just want to show that I'm not throwing the rifle down and blasting away lol. It will shoot fine long as I do my job, I just thought that 175 bullets would give better groups than 168 because of a higher b.c. my understanding of b.c. was off. I think I get it now though. As for lee, I use all the info I can find for my loads cause I learned all this on my own. Didnt lnow anyone that reloads so I just studied up on all of it and was super careful. Thats why If u watch I'm always on here asking stupid questions about reloading. This site has been a wealth of knowledge. Its not that I can't get sub moa groups its just alot harder than I thought. Everyone u talk too shoots moa with a smoke hanging outta their mouth while holding a beer in their left hand... If u know what I mean lol

 

[Rule3]

I would (and do) use the 168 grain bullets than.

 

[mdi]

Wow, bunch of good info., but since my Ruger American can shoot waaaay better than I can, 1 MOA is good (great) for me. I have mostly had success with Hornady 155 A-Max bullets and IMR 4064 and my best group @ 100 was right around 15/16" (yeah, I measure in 1/16ths), but mostly run 1"-1 1/8". I keep my 168 HPBT Match bullets for my Garand...

 

[Joshboyfutre]

I've been thinking about trying 4064 instead of varget, might get a can and compare the two

 

[Bart B.]

You say with federal Gold medal match it shoots around .5 moa, with 168g smk with 46g of varget it shoots.56 moa, & 175 smk shoots .68 moa.

Are those dimensions the smallest or average of several groups shot with their respective loads? Or just what one load shot once?

 

[Joshboyfutre]

1 load. So far Ive loaded groups of three from min to max miving up in half grain increments. The gold medal match is the best measurement it shot though. I dont remember the exact measurement but it was consistantly shooting great groups. I don't think those groups are one time flukes, but I guess I'll find out when I try all of them again.

 

[Bart B.]

The size of a single 3-shot group means several of the same load will range from about 60% smaller size to about 240% bigger than its size.

Shoot at least 15 shots per test group to find out what the load's real accuracy is; what you can count on at least 80% of the time.

If your shots start to walk impact as the barrel heats up, shoot 3 then wait until the barrel cools down then do that four more times.

About half the groups shot will be close to average in size. One fourth will be larger and one fourth will be smaller.

I recommend using the largest group fired to represent the accuracy the rifle and ammo has as you shoot it. Smallest groups fired are almost impossible to duplicate.

 

[Joshboyfutre]

I was kinda wondering what kind of standard I should hold. All the numbers I have now are just from ladder tests to see where my harmonic nodes are. So after testing 155g the way I've been doing I'll go back and test each group that shot well with five 3-shot groups. Or should I be doing my ladder tests with more shots also? How do u do ur initial load tests w/a new rifle? Chrono excluded because I need to get one still.
Btw, thank u for the advice

 

[Joshboyfutre]

Also whats ur opinion of using a wet towel to cool my barrel down? I was thinking of rubbing it down with a damp towel then waiting a bit for the temps to even out, would that even work?

 

[combatinfidel]

I've been thinking about trying 4064 instead of varget, might get a can and compare the two

I'm getting ready to test bar get loads against 4064 loads


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[combatinfidel]

I highly recommend a chrono because it checks consistency of your loads if you have one group spread out with very close velocities and a low standard deviation than you would want to try another load if you have a group spread out with a difference in velocity and a higher standard deviation than you may want to reload that group paying more attention to making everything the same case length charge bullet seating OAL


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[Joshboyfutre]

Yeah I've been meaning to get one just haven't been able to free the money up. Definately need to get on that. If u could post the results of ur tests I would be interested to see the results.

 

[combatinfidel]

Yeah I've been meaning to get one just haven't been able to free the money up. Definately need to get on that. If u could post the results of ur tests I would be interested to see the results.

I'm going to try and go to the range this week I'll let you know what my results are like you I loaded three rounds from min to max in half gn increments for each however I am shooting a savage 11 scout in 308 with an 18" barrel


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[Joshboyfutre]

Right on man, thanks

 

[Bart B.]

If one uses a chronograph to "check consistency of your loads," consider the following facts.

Muzzle velocity from rifles hand held against ones shoulder will have a three to four times extreme spread in fps than it's barreled action clamped solid in a fixed mount. Average muzzle velocity will be lower with hand held rifles. Hand held rifles start recoiling backwards as soon as the bullet leaves the case mouth. Our bodies absorb the rearward recoil which subtracts from the bullet's velocity relative to the barrel. If your bullet takes 1.2 milliseconds to go from case mouth to muzzle, that's how long the rifle will move backwards while the bullet's still in the barrel. While the rifle recoils at slower speed, it still subtracts from the bullet's speed relative to the rifle itself.

If you can test fire the rifle in free recoil without it sliding off the bags it rests on, that'll produce much more uniform velocities than if hand held.

Or take the barreled action out of the stock then bolt it to a 7" long 2x3 so the recoil lug is against one end then bolt that block of wood to a 2x4 long enough to clamp on the bench at your range. Cut a notch for the bolt handle to clear. Bolt another block of wood under one end that hangs over the front of the bench to keep the fixture and barreled action fixed in place when fired. Set up the chronograph screen so they're centered on the bore axis at the desired distance.

One other interesting fact. The same rifle and ammo fired by several people all holding it against their shoulder as it rests atop something on a bench top will have average muzzle velocity spreads of 50 fps or more. I've seen as much as 90 between me and a friend shooting the same load in a 12 pound match rifle testing .308 Win loads.

 

[Joshboyfutre]

Thats wild. So that effect harmonics and everything else from person to person, not just rifle to rifle? Guess the moral of the story is go further than just having the same sight picture each time, but also conciencly make sure to keep the same grip and shoulder placement of the rifle? Also a round that does well in my rest with a kick-plate might not be as good against my shoulder? Its crazy how many variables there are when it really comes down to it!!

 

[combatinfidel]

I use a vice at the range that is bolted to the table the stock is clamped into the vice I generally try and eliminate as many variables as possible


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[Bart B.]

No effects on barrel harmonics from how the rifle's held; as long as the barrel it totally free floated and doesn't touch the stock fore end anywhere. The barreled action has one resonant frequency and several harmonics of it that don't change. Because the barrel metal and shape stay the same from shot to shot, so does the frequencies it wiggles and whips at. Barrels don't get hot enough shot once every 5 to 10 shots per minute for 10 to 20 shots to change these frequencies.

That said, depending on how the rifle's held, the direction and amount of whip and wiggle will change. Hot loads cause greater amounts than reduced ones. This is why two people shooting the same rifle and ammo will probably have different zeros on the sights to hit point of aim.

 

[Joshboyfutre]

Yeah I guess that makes sense with the harmonics being the same. Man u r a wealth of knowledge! Thank u for laying everything out in an easily understood manner. You Sir, are a gentleman and a scholar!! Not being a suck ass, its just that my understanding of B.C., harmonics, MOA, & load testing have really improved from this one thread.