Need some advise from hand loaders for a 308 please

[grubbylabs]

It took a little work in the AR15's but I finally got a load that works well with cast in it, so I think I should be able to find something that will work ok in my DPMS 308.

I never did see any leading or lube issues, just shotgun pattern sized groups until I got the bullet going slow enough.

 

[Reloader2]

I suggest you try some reloads with IMR 3031.

I've been loading 165's with IMR3031 for my grandson.

 

[bfoosh006]

The guys with 16" SOCOM's were having the same problems... IMR 3031 solved most of the accuracy issues.

A Gentleman by the call name of RAMMAC on www.m14forums.com.... has a TON of info on IMR 3031 in a 16" barrel SOCOM.

Here is the link to his section on m14forums.com....

http://m14forum.com/rammac/

I truly suggest you try some IMR 3031.

 

[rboyer224]

Problems with factory loads even!!

Hello all. Just joined this forum to try to figure out my problem. I also have the DPMS GII Recon. The pictures are of the factory ammo I've shot through the gun so far. I can completely understand having pressure issues with handloads, but factory ammo?? Now, I do have a silencer on it also, and understand that increases overall pressure and most likely effects timing, but I didn't expect it so much with factory ammo. Since firing these, I've added an adjustable gas block but have not had a chance to shoot it again. Still can't believe that the silencer creates enough pressure to blow out the primer!! I guess I could also try it without the silencer and see the difference.

 

[Tinbucket]

Need some Advice ffrom handloaders for .308 please

IMR 4064 is what I use most loadings.
A Speer, and bullet does matter, 150 grain-47.0 grains0f 4064. CCI primer.
give me 2800 fps out of Remington 600, with it's short barrel.
A little more than NATO pressures if you're shooting in an auto.
Any of the 150 grains will probably not be any pressure issue with the load.
I've got a few 168 grain load but anything heavier I load in the .30-06.
The Old Lyman and some other manuals have higher pressure higher velocity loadings and I have some still packed up.
This load came out of Speer manual, I think

 

[Jimro]

rboyer224,

I don't know what Hornady loading you are using. Based on the cartridges I'm guessing you are using a "Superformance" load.

It is recommended that to get the best functioning with Superformance ammunition in gas operated/gas piston semi-automatic or select fire guns, rifle length gas systems with 20 inch or longer barrel lengths are best for reliable firing and extraction. Any other configuration, particularly shorter barrels/gas systems are best served with the installation of an adjustable gas system, ESPECIALLY if a suppressor is to be installed.

Due to the longer duration of peak pressure produced by Superformance™, the post peak/declining port pressure at common carbine and mid-length gas port locations is still higher than that produced by standard propellant. This has a tendency to flood the system with a larger volume of gas, at a higher velocity, that tries to open the bolt of the gun too fast. It’s a timing issue. The cartridge case is still swollen from the application of pressure during firing while the gun is simultaneously trying to extract the cartridge case before it has had an opportunity to settle back to its original size, or more simply: the gun is still in the process or firing while it’s trying to extract the cartridge case.

If the firearm and the ammunition are not in sync, there can be what is commonly identified as “pressure signs” on the cartridge case. This is exhibited by the movement/marring of the head of the cartridge case, cratered primers, flat primers, ripped or ruptured cartridge cases, “popped primers”, and/or any combination of these effects. If any of these “pressure signs” are apparent, stop firing immediately. If an adjustable gas system is installed, it is advisable to reduce the amount of gas flowing through the system by closing the gas port until the gun operates correctly.

With the installation of an adjustable gas system, gas pressure can be metered to a point that enough gas is applied to open the bolt, but at a slower rate to allow the cartridge case to return to its original diameter prior to the movement of the bolt, and thus allow for proper extraction.

http://www.hornady.com/ammunition/superformance-in-gas-operated-firearms

Just know when you use that adjustable gas block to tune your rifle for the Hornady load, you will get poor extraction from regular ammo.

Hope this helps.

Jimro

 

[Mike / Tx]

grubby, I know this is sort of an apples to oranges approach but I'll throw in anyway.

I shoot a short barreled Ruger a LOT. It sports a 16.5" pencil thin barrel as well, and the whole thing with 5 rounds ready to hit the woods only weighs 6.5 pounds, so it rocks around a little when fired form the bench.

I tried ALL of the highest recommended powders and worked through the loads listed here and elsewhere, shot some of the top notch match loads, and all trying to find ANYTHING that shot as good or better than the plain ol Rem CL's I had been using.

Just about the time I decided that 1.5" was as good as it gets no matter what, I went to loading up some reduced loads using H4895 for my grandson and wife to use on some feral hogs. I had, in the past, loaded them to the very bottom of the data using some 125gr bullets when the kid was only 3 so he could learn to shoot without getting pounded to death. Well these were maybe a grain below the standard start load for the 150gr bullets. The funny thing was they shot EXCELLENT. So I worked them on up to see how far this would go. I ended up matching the velocity of the Rem factory loads only instead of the 1.5" groups I was getting right at or just below 1" at 100yds using the Rem 150gr bulk bullets.

I pretty much cut the group size in half, using H-4895. I realize that your rifle is gas operated, but even still working up form the starting loads should give you enough umph for ejection, and you could be like me and hit something that you actually like.

Just throwing that out there as I have been there with the short barrels ..

 

[rboyer224]

Thanks Jimro

Jimro,

Thanks for that info. I do understand why it happens (now), but did not know about that ammo. It was the Superperformance ammo. I do have an adjustable gas block on it now and will try again. I completely understand the whole chain of events causing the swiped head and all that, however,..... The bulges caused by the ejection holes still have me a little confused. I understand the timing and that the bolt is trying to pull the case out before it has shrunken back down to size, but those two ejector port hole bulges must be caused at the very moment the round is fired. That's the only point where the pressure is that high and the bolt is not turning yet, which pushed the soft hot brass in to those two holes. I don't see how closing off the gas port can have any effect at all on the initial pressure and those two dimples/bumps???? With the adjustable gas block and the timing being corrected, I can see how it will no longer swipe those two bumps off, but they would most likely still be there correct? The gas block is not changing the pressure that the round creates, it's just changing how much of it comes back (and when) to the bolt. Does that all make sense? Anyway, thanks for that link. Luckily I only had a few shots before I realized that this was happening. Hopefully the gas block corrects it all. Thanks again.

 

[Jeff2131]

IMR3031...4064 is too slow for .308 in ar's.

 

[Bart B.]

IMR4064 in .308 Win cases has been used in AR10, M1, M1A and M14NM rifles with 168's for match winning and record setting accuracy. The best of them shot 4 inches or better at 600 yards.

In the '60's and '70's, military teams tried IMR3031 in .308 Win. ammo for M1 and M14 rifles and it did very good, for a couple dozen shots, then powder fouling degraded accuracy. IMR4064 loads would go 60 t0 80 shots before cleaning was needed to maintain best accuracy.

 

[Tinbucket]

Need some advice from handloaders for .308

Kind of a diverent thread but for slam fires in Garand and M16 or AR15.
There are or were Titanium firing pins available for the M16. I haven't ordered on since I've not had the problem. It might take a bit of a search for them, if still available. Lither firn pins help with slam fires.
I have a Garrand and ran across mention of a spring loaded firing pin.
I didn't book makr it but others I'm sure know a lot more about these two subjects.

 

[Jimro]

Thanks for that info. I do understand why it happens (now), but did not know about that ammo. It was the Superperformance ammo. I do have an adjustable gas block on it now and will try again. I completely understand the whole chain of events causing the swiped head and all that, however,..... The bulges caused by the ejection holes still have me a little confused. I understand the timing and that the bolt is trying to pull the case out before it has shrunken back down to size, but those two ejector port hole bulges must be caused at the very moment the round is fired. That's the only point where the pressure is that high and the bolt is not turning yet, which pushed the soft hot brass in to those two holes. I don't see how closing off the gas port can have any effect at all on the initial pressure and those two dimples/bumps???? With the adjustable gas block and the timing being corrected, I can see how it will no longer swipe those two bumps off, but they would most likely still be there correct? The gas block is not changing the pressure that the round creates, it's just changing how much of it comes back (and when) to the bolt. Does that all make sense? Anyway, thanks for that link. Luckily I only had a few shots before I realized that this was happening. Hopefully the gas block corrects it all. Thanks again.

No problems. As to the amount of pressure verses the ammount of gas, those are two important concepts to understand. The "initial pressure" needs to be in a mechanically locked environment. Superformance ammo reaches peak pressure sooner, and stays there longer, than normal ammunition. Weird stuff happens when you get early bolt unlocking. Superformance doesn't produce more pressure, it just produces more gas to get more performance. So you get more pressure both earlier and later, with the same peak maximum pressure where it should be.

I don't know if I have the words to explain why you have two dimples, but I'll try.

But, what I expect the two dimples are is one from the bolt pushing the cartridge into the chamber on loading, and the other on early extraction. I think the brass is catching in the chamber before the bolt rotates into the locked position. As your ejector spring weakens with time and the chamber dimensions grow, expect one of the dimples to start fading away.

Hope this helps,
Jimro

 

[Bart B.]

There's one section of extruded brass back from the case head normal flat surface for each cutout in the bolt face that lets brass extrude back into it.

Look at the bolt face and its cutouts will be a mirror image of the case heads.

Would be good to see pictures of both bolt face and case head for the most extruded case for all to see and compare.

 

[rboyer224]

So are you saying it's normal for the brass head to extrude back in to the bolt face holes? Is it going to continue to do this even when the gas block is adjusted correctly? I hope not. That kind of ruins my reloading brass!! Here's a picture of the bolt.

 

[Jimro]

You have twin ejectors, so twin ejector marks are to be expected with high pressure signs. I was wrong in my previous assessment.

But during normal firing the brass will push back into the bolt face. Under normal pressure this will not prevent your brass from being reloadable. Properly adjusted, you shouldn't be ruining brass.

Jimro

 

[rboyer224]

Very good. Thanks Jimro. I was hoping that would be the case.

 

[Bart B.]

Cartridge brass starts extruding into bolt face holes at about 65,000 cup or 75,000 psi. Pressure in those cases is way too high for safety. Cut the charge 5 grains then try again.

I've shot .308 proof loads that didn't have anything like those cases do.

 

[rboyer224]

Bart B

Thanks sir, but if you look back, that ammo is factory Hornady ammo. That's why I've been asking the questions. If it were my handloads I would assume full ownership and of course reduce the charge.

 

[Bart B.]

I forgot about it being factory ammo.

Now I think the barrel is bad. Have someone measure chamber, bore and groove dimensions. Something is way too small.

My first guess is the chamber is too short from bolt face to chamber mouth. The firing pin drives the case mouth hard into the chamber mouth crimping it into the bullet. That raises pressure. Fire an empty primed case in it then see if the case mouth is crimped in.

 

[Jimro]

Bart B.

The ammo in question is Hornady Superformance, which has a different pressure curve than standard ammunition.

The adjustable gas block should fix the problem, which is that the sooner than expected peak pressure is causing earlier unlocking while the cartridge is still under significant pressure. It may turn out that the lot of Superformance being used is just unsuitable to that rifle, although I think the adjustable gas plug will work. But a potentially bad lot of ammo isn't out of the realm of possibilities either.

We used to see this when people would try to run "Hornady Light Magnum" loads through Garands and M1As without adjustable gas plugs and they'd ruin the op rods.

Jimro