Need some advise from hand loaders for a 308 please

[Jimro]

Unclenick,

I wouldn't want to reload either Mk248 (300 Win Mag) at all or Mk316 brass too much. To optimize accuracy the brass upholds Federals reputation for being "soft" and you get loose primers quickly, despite Federal publically stating that they increased the hardness of the Mk316 load specifically for semi-autos. The Mk248 load being spec'd to 68k PSI doesn't help things at all either. But the military doesn't reload, so brass life isn't a concern from that perspective.

I also questioned the move to the Fed GMM primer for Mk316, but so far there have been no negative results running that load through M14s, Mk17/Mk20s (FN SCAR variant) or AR-10 variants.

On the flip side of that, Slamfire has reports of slamfires with milspec large rifle primers as well. It could just be a matter of time, but as of right now I'd say that the 210M primer has demonstrated itself reliable enough for semi-auto use by the military.

Jimro

 

[chiefr]

One more concern I feel the need to bring up in regards to earlier posts including my own on this subject, is the differences between automatic rifles and bolt guns.

Years of reloading for HKs, AR 15s, M1As FNs etc has taught me how picky some autos can be to function and group satisfactorily with reloads.

 

[grubbylabs]

These are the best groups I could manage with this rifle so far. The 5 shot group is Varget and a 168 grain Hornady HPBT. The 10 shot group I did kinda quick, and is the Surplus H335 and a Hornady 150 grain SP.

 

[Bart B.]

There is one issue of a centerfire rifle that has a bolt that, if severe, no reloads with cases from it will shoot very accurate.

Bolt face that's way out of square.

More common in commercial semiauto military offshoots.

 

[RC20]

The last thing I would do before I got rid of or safe queened the rifle would to try different COLs first.

I not only agree, I think that is not emphasized enough.

The gun may not be sub 1 MOA, but the COAL is very important to what it likes and sometimes even primers can change the equation so that's another one to try.

I also agree on the semi autos, I have heard all the stories of tack driving and I have had two, neither was that impresive (the second one is a RR). Nice enough gun but I have yet to find a load that makes it 1 MOA let alone sub.

 

[bfoosh006]

I suggest you try some reloads with IMR 3031.

 

[Unclenick]

Bfoosh006,

That's a good idea. The max loads will be a bit slower, but the faster powder will make for a shorter barrel time, and that may be what's needed to synchronize to harmonic muzzle swing in the short barrel. It would be interesting to see.

On the flip side of that, Slamfire has reports of slamfires with milspec large rifle primers as well. It could just be a matter of time, but as of right now I'd say that the 210M primer has demonstrated itself reliable enough for semi-auto use by the military.

I was present at one slamfire of a Garand using LC 72 M2 Ball. So neither the primer hardness, nor proper primer seating are absolute guarantees against slamfires. It's just a question of reducing the probability some. Slamfire also posted the report on M16 slamfires for which Lake City reduced the primer sensitivity and apparently that reduced the slamfire incidents successfully.

I have to suspect, when you get a slamfire with military ammo, that there's a marginal mechanical spec somewhere in the mix.

I recall back in the early 90's that Federal denied their primers were more prone to slamfires than others. They felt that reputation had arisen simply because their primers were used by more match shooters than any other brand at the time.

I'm not fully convinced, though. It's just a gut feel, probably biased by personal experience with Federal's pistol primers that handguns with weak mainsprings will often fire them when others fail. I don't know that this characteristic carries over to rifle because I haven't ever lightened mainsprings in mine. But from all the slamfires reported with Federal primers in the past (the ones they dismissed), including the two OOB firings Slamfire had with them, that they are at least as sensitive as anyone else's. Without performing an H-test, though, there's no quantifiable comparison that can be made.


Grubbylabs,

One other thought is to ask if you looked the crown over carefully. One article I read long ago was about the purchase of one of Dave Manson's crowning tools, and the two co-purchasers got some of their money back by crowning rifles for about 15 members of their club, and, IIRC, charging them only if accuracy improved, which it did in 50% of them. So it's a common shortcoming.

If you know someone with a lathe and dial indicator, have them chuck the bolt up and check for bolt face squareness and squareness on the back side of the locking lugs. Because truing a bolt face or lapping lugs increases headspace by the amount you take off, an extremely crooked face may mean getting a new bolt rather than messing with the current one. Also watch that the firing pin extension remains within spec if you alter that.

 

[Bart B.]

Here's my take on squaring up bolt faces........

As the boltway may not be aligned with the chamber axis, turning a bolt in a lathe on its center then facing it may end up with the bolt face still out of square with the chamber axis. I've seen that happen, expecially with forged receivers. Cases fit in the chamber and that axis is what the bolt face should be square with.

Face the receiver first so its square with the barrel tenon threads. Then lap the lugs to full contact. It's now ready for a closed bolt (and held in that position 'cause that's where it is when the round fires) in the receiver to be faced with one of these or the likes thereof:

http://www.midwayusa.com/product/493220/ptg-bolt-face-lapping-tool-remington-700

Either face lapping with compound or cutting with an end mill works fine. Headspace will increase a little bit. If too much, the barrel needs be set back one thread then rechambered.

Plus, squaring up the receiver face typically ends shot walking from barrels getting hot.

 

[Jimro]

Unclenick,

I've had that feeling as well, knowing enough competitors who switched from FGMM primers to CCI or Wolf after having one slamfire. However since I can't quantify that feeling in any meaningful way I try to look at the facts as they are, and that is that slamfires are a very rare event.

Of course the lack of evidence of slamfires with Mk316 ammunition shouldn't be construed as evidence that FGMM primers aren't more sensitive than other primers, just that they are robust enough to serve in a milspec load with semi-auto rifles with free floating firing pins. It should also be noted that handloaders are using many more loading tools and techniques than the Federal ammunition plant that is putting out Mk316 which gives a good explanation why one process producing one load shouldn't be considered as proof positive that every process and every load using the same component will end up with the same net reliability.

Jimro

 

[Bart B.]

Of the 20 or so slamfired cases I've seen from Garands, every one had a full, normal dimpled primer flat with the case head. Same shape and depth as normally fired ones. Which pretty much convinced me the hammer made a normal, full-force fall on the firing pin in a well closed bolt.

 

[Rimfire5]

You didn't say what twist your rifle was or if you were shooting with iron sights or a scope. If iron sights, I would suspect that sighting was the critical component in accuracy more than the rifle itself.
If you were using a scope off a rest, then you have a starting point to explore if you can improve the effective accuracy by finding a load that your rifle likes best.

Even if you don't have a super accurate rifle, you might be able to find some loads that could flirt with the 1 MOA result if you play with velocity and maybe seating depth (AOL).

If you aren't turned off by the price of Federal Premium Gold Match 168s or 175 SMK factory ammo, they are both good indicators of .308 factory ammo that will give you indications of what high quality factory ammo will do. If your rifle has a preference for bullet weight, they might also tell you if you should concentrate on heavier or lighter bullets.

Since you already have at least one powder/bullet combination that is performing close to 1 MOA, you also have a hand load starting point.
Start with a couple of powder and bullet combinations that have shown the best results. Just keep detailed records and adjust the powder changes in regular increments, probably in 50 fps increments until you get a feel for where to really concentrate.

Then work up some loads in sequence around the loads that gave the best results. You might get lucky. At worst, you'll find out what your rifle prefers and determine what combinations give the best results for your particular rifle.

While is isn't the same caliber as you .308, by doing some analysis, I helped a range buddy with a 1976 Colt HBAR in .223 that he couldn't get to shoot accurately. And he couldn't get it to average under 1 MOA even shooting from a rest with a Leupold scope with max power of 18x.
From his data, it was obvious that his 1:7 twist was better with 77 grain SMK but really got results when the velocities were in a narrow range. Turned out that if he kept the velocities between 2550 fps and 2600 fps with SMKs he averaged 0.873 with H4895.
With Varget the range was very narrow between 2450 and 2500 fps and he averaged 0.812. Above 2500 he averaged 1.106. Below 2450 he averaged 1.209.
With Berger 77 OTM bullets and Varget powder, he averaged 0.809 between 2267 and 2322. Over 2322, he averaged 1.364.

I have found similar, but not as severe velocity preferences as I found with that Colt when loading for my .308 bolt actions and my M1A. Mostly, I find my rifles have stronger bullet weight or bullet length (touching the rifling) than velocity preferences, but they are sensitive to velocity when trying to find really accurate nodes.
My M1A has a 150 gr bullet range from 2600 to 2642 fps, a 168 gr best performance range from 2488 to 2525 fps and a 175 gr best performance range from 2459 to 2482 fps. With the right hand loads it shoots less than 1 MOA by a pretty good margin.

You may find that kind of velocity preference with your rifle. If not, you'll have the data to know what your best loads really are.

 

[Eppie]

Unclenick said: 10,275 Try a box of Federal Gold Medal Match ammo that uses the 168. It tends to shoot well in most any gun chambered for the .308. It would give your expectations a baseline to work from.

Do the above.

Then you will have isolated what the gun is capable versus the handloads. I always keep some FGMM 168 on hand so that when I have problem I can isolate it the component. I call them my control group.

Having said that. I can also say that I used to own a DPMS .308 and it was never that accurate. I eventually migrated to a POF 308, that was an improvement but still not as good as a $600 Remington 700.

 

[grubbylabs]

Thanks for all the help so far, I will be looking into a few of the suggestions, like getting some federal match ammo. I checked the OAL on my rounds, and the 2.800 is just barely short enough to fit the magazine. I was seating just a little shorter to keep from having seating problem. I think I am going to try the IMR 4895 still. I am also going to try some Speer bullets and and go up to a 180 grain bullet, and possibly a 190 grain bullet.

 

[Bart B.]

I don't think any bullet over 170 grains will shoot more accurate.

 

[grubbylabs]

Just going to try it so I can say I tried every thing. At this point I am not even sure trying a different powder will make a difference, but what the heck. I might even try upgrading to a higher quality scope in the near future to see if that changes any thing. Its wearing a less than $200.00 Vortex.

 

[TATER]

Nothing wrong with a vortex, A good trigger could make all the difference too though.

 

[Bart B.]

If you can, slug the barrel with soft lead then measure it's widest points with a good micrometer. If nothing loaded seems to shoot worth a darn, the barrel's groove diameter may be large enough to drive a pickup truck through. Hopefully, it won't be more than .309" which is about the limit for MOA accuracy needs with .308" bullet diameters in well loaded ammo.

I've seen a few .30-06's with .311" groove diameter barrels that no .308" diameter bullet would shoot inside 3 inches at 100 yards from any set of components under it I tried. There's no reason a .308Win./7.62NATO barrel would be different.

 

[grubbylabs]

I had not thought about slugging the barrel, I might have to try that. Going to wind up with a 30 cal mold at some point any way. I wonder how load development for the 30 cal will go compared to how it went with my 223?

 

[chris667]

3031 will give you higher velocity with lighter bullets out of a 16" barrel.
I use 43.7 g of IMR3031 in a Winchester case with a 150g bullet.
I use 45.0g of IMR4895 in a Winchester case with a 168g bullet.

 

[44 AMP]

Going to wind up with a 30 cal mold at some point any way.

If you are talking about cast bullets in a gas operated gun, (AR?) be prepared for issues. Lead, bullet lube and powder residue all together don't do well in some gas systems.

if you are talking about using a .30 mold to cast a slug for slugging the barrel, use pure lead, and pay attention to the "feel" when driving it through the bore. A tight spot in the bore will show by feel, and by the diameter of the slug after it passes through it. A loose spot will only show by the "feel" of the slug going through.

Good Luck!