Im guessing this is over gassed?

[Basic user]

Im at 42.9 of varget (1.1gr below book max) on a suppressed PSA rifle length, rifle buffered LR308 firing hornady 178s. Its destroying the rims. Lantac enhanced bcg and superlative arms block opened all the way. I even threw in another tungsten weight in the buffer for a total of 6.4oz. Rough chamber maybe? I scoped it once and don't remember seeing anything out of the ordinary.

 

[NHPiper]

I used to run 44gr of Varget in an 18" bolt gun with 175SMKs. So this seems to be in the range, but brass can have can have wildly different internal volumes.

How many rounds through the barrel? Have you bore scoped to see if there is a carbon ring? They can cause massive pressure swings.

A couple of those rounds have very clear pressure signs with the brass marked up and primers flattening.

I do sometimes run 8208 loads in a 5.56 hot enough to flatten primers but there is a lot less powder in those charges than a large frame AR. I would be backing those down at least a grain.

So sort story, over gassed but also over pressure.

 

[Basic user]

About 200 or so rounds through the barrel. I dont remember a carbon ring I will double check and post pics. The reason why I'm baffled is that the gas blocks all the way open, the buffer's an ounce heavier, and I'm more than a grain below book max.

 

[NHPiper]

About 200 or so rounds through the barrel. I dont remember a carbon ring I will double check and post pics. The reason why I'm baffled is that the gas blocks all the way open, the buffer's an ounce heavier, and I'm more than a grain below book max.

Did it just start happening?

Any changes to the load like a change to Base to Ogive, primers, or brass type?

 

[Basic user]

Did it just start happening?

Any changes to the load like a change to Base to Ogive, primers, or brass type?

I've never ran it up to max before. I've always loaded to the book minimum and was happy with the .7" groups she was giving me the 4 or so times Ive had her out. After it's proved itself that it can group, I was then interested in getting the load close to book max to now take her out to distance and then this started happening. Now I'm stumped. I've only ever loaded this with berger 175s and around 42 grains or so. Once I got to around 42.6 it started to do this. So I stopped, threw another ounce in the buffer, and returned to the range and it's still happening.

 

[Ronin22]

I've found a heavier buffer or stiffer spring will reduce the smears of the case heads, but the gas port diameter is the main thing to consider. If your SA bleed off GB is all the way open and you are still blowing primers and getting those ejector smears then I would bet your gas port is too large. You could remedy with a restrictive gas block and make the hole smaller.

 

[Basic user]

Yea, I was thinking the same thing... I could close off the gas block in the restrictive mode but they say you shouldnt do that to their blocks, which is odd but I understand. I was going to try it and see what happens. Or just shoot it without the can as well... How big is that gas port that it's still doing this? lol. I'll just have to pull it down and measure that port size to see.

 

[Ronin22]

Yea, I was thinking the same thing... I could close off the gas block in the restrictive mode but they say you shouldnt do that to their blocks, which is odd but I understand. I was going to try it and see what happens. Or just shoot it without the can as well... How big is that gas port that it's still doing this? lol. I'll just have to pull it down and measure that port size to see.

Yes, I have had no luck using the restrictive mode on the SA GB. I have luck with the restrictive Aero Precision GB, or cooler and more expensive yet are the Rifle Speed hand adjustable GBs. Even a couple/few thousands can make or break a gas port hole size. I have over bored a couple and saved them with restrictive gas blocks. I have also gone so big that only the SA bleed off saved the barrel.

 

[Basic user]

Yes, I have had no luck using the restrictive mode on the SA GB. I have luck with the restrictive Aero Precision GB, or cooler and more expensive yet are the Rifle Speed hand adjustable GBs. Even a couple/few thousands can make or break a gas port hole size. I have over bored a couple and saved them with restrictive gas blocks. I have also gone so big that only the SA bleed off saved the barrel.

I see. Yea, I've had a few rifle speeds and out of all of his models not a single one fits 99% of my ARs lol. That's my luck though. I may try for this one specifically.

 

[eklarsen]

You're over pressured and about to learn a violent science lesson.

 

[NHPiper]

I've never ran it up to max before. I've always loaded to the book minimum and was happy with the .7" groups she was giving me the 4 or so times Ive had her out. After it's proved itself that it can group, I was then interested in getting the load close to book max to now take her out to distance and then this started happening. Now I'm stumped. I've only ever loaded this with berger 175s and around 42 grains or so. Once I got to around 42.6 it started to do this. So I stopped, threw another ounce in the buffer, and returned to the range and it's still happening.

What was the difference in velocity between the minimum and what you were getting now?

 

[45-90]

Im at 42.9 of varget (1.1gr below book max) on a suppressed PSA rifle length, rifle buffered LR308 firing hornady 178s. Its destroying the rims. Lantac enhanced bcg and superlative arms block opened all the way. I even threw in another tungsten weight in the buffer for a total of 6.4oz. Rough chamber maybe? I scoped it once and don't remember seeing anything out of the ordinary.View attachment 8520821

You are over max in my reloading manual, which states 42.4 gr.
Drop the charge to 40.5 gr and try...your problems should disappear, make sure your not jamming bullets into the rifling.
Appears 41.3 would be a good max for your rifle...and this brass.
Some lots if Nosler brass are soft in the case head, some old lots only lasted one firing in a bolt gun.
So try another brand of brass, Lapua is expensive but I use it in auto loaders, ...sometimes, as it has harder cases heads.

is that primer blown out of the case or just deprimed? That would be way over pressure.
Are All charges weighed ?

 

[Basic user]

You are over max in my reloading manual, which states 42.4 gr.
Drop the charge to 40.5 gr and try...your problems should disappear, make sure your not jamming bullets into the rifling.
Appears 41.3 would be a good max for your rifle...and this brass.
Some lots if Nosler brass are soft in the case head, some old lots only lasted one firing in a bolt gun.
So try another brand of brass, Lapua is expensive but I use it in auto loaders, ...sometimes, as it has harder cases heads.

is that primer blown out of the case or just deprimed? That would be way over pressure.
Are All charges weighed ?

Which book is that for reference? And I'm off the lands by a bit on this load, by how much I'd have to look at my notes; just got back into town so will check that. And I agree this brass feels soft. I hear winchester is kind of tough; is that true would you know? And that primer fell out. This batch of brass is on it's 5th loading I think? The first 3 or so of it's loading was at the minimum. And I weigh every charge on my v4 autotrickler to zero tolerance. I measure bto on every bullet seated as well.

 

[Basic user]

What was the difference in velocity between the minimum and what you were getting now?

I just started load workup so I havent even chronoed it yet. I proved it can group first, and then wanted to see how far I could push it before I seen signs of pressure. When I started to see pressure I felt it was too early, (according to my 2 books and hodgdons online) which leads me to this post. I'm going to chrono the next load I shoot through it, at the lower charge weight to see where I am.

 

[N_Turs]

I would say assuming your not over charging and your case pressures are ok, Just run the gas block in restrictive mode. Ive used there blocks like this without issue. While I like their product calling them and discussing the use and tuning is not worth it. They are very short on the phone and just always assuming you dont know what your doing... The gas block will work fine in a restrictive setting it will just be more prone to carbon fowling and locking of the adjuster.

 

[clcustom1911]

When I started loading 308 for my semi, I accidentally used bolt gun data from the manufacturer. My "just above mid-range" load according to that data was actually almost 3 grains over max when I compared it to ar-10 load data.

Factory ammo (very light chamber flute marks)

My "assumed safe" load. Very heavy chamber flute embossing on the case. One the bright side, i know my chamber was cut nicely

Double check your sources of data and compare them to the 308 AR loading sticky thread in the reloading section.

 

[Terry Cross]

Like the gents above suggested, I believe you are simply over pressured for that particular barrel/chamber.

Nothing in your pictures or description would make me think this is over gassing your system.

You mentioned that the rims are getting destroyed. Technically, your rims look fine. I don't see anything similar to rims that were torn off by the extractor, which would point to over-gassing and the bolt trying to extract before the chamber pressure drops.

You are destroying primer pockets and getting brass extruded into the ejector hole which is destroying the case head. To me that is pure pressure indicators.

No need to measure your gas port. That will not fix your problem.
No need to jack around with your GB adjustments or buffer. Neither of those are your problem.
Get a safe and well behaved load THEN tweak your gas system if needed, which will likely be fine as is.

It doesn't much matter in the least what the reloading manuals say or what other peeps .308s can handle. Your rifle think's that load is too hot.
Do something with your ammo to get your chamber pressure down and the gas system will respond accordingly.

 

[Basic user]

I see. So it's just too much powder then eh? What confuses me, is how the base of the cases are damaged. I don't see any of the ejectors tearing the rims, but rather displacement of the brass on the face of the base; if you were to rub your finger over the head stamps, there are super sharp burrs torn out of the face. How does this happen?

 

[DeathBeforeDismount]

Nosler is also some of the softest, shittiest brass you could use. It's going to exacerbate any pressure issues. Switch to quality brass like lapua and it will contain the pressure much better.

 

[Cascade Hemi]

Nosler made Nosler brass is really low quality. While you're figuring out your load, take the opportunity to change the brass.

 

[Cascade Hemi]

Nosler is also some of the softest, shittiest brass you could use. It's going to exacerbate any pressure issues. Switch to quality brass like lapua and it will contain the pressure much better.

Even Starline would be an improvement, albeit less capacity than the Nosler.

 

[Basic user]

Really? I didn't realize Nosler sucked so much. I hear that it's good brass all the time. It was also pretty affordable when I bought it and that was one of the deciding factors; I knew AR10s beat up their brass so I didn't want to run any expensive shit through it; Would starline really be more durable?

 

[Cascade Hemi]

Really? I didn't realize Nosler sucked so much. I hear that it's good brass all the time. It was also pretty affordable when I bought it and that was one of the deciding factors; I knew AR10s beat up their brass so I didn't want to run any expensive shit through it; Would starline really be more durable?

Nosler used to buy their brass from Norma. That is where their brass reputation came from. When Nosler started making their own brass it was never the same. I would take Starline brass over new Nosler every single day. Just be aware that Starline 308 Winchester brass has much lower capacity than Winchester brand used in a lot of load data.

FWIW, I don't think a low dwell, properly gassed, AR10 is hard on brass even at the top end of pressure. "Service Rifle" 308Win load data is for an M14, not an AR10.

 

[Basic user]

Understood. I do know about the relationship between nosler and norma, but for some reason I read that nosler somehow got their shit together. That may have been bad intel. Is winchester tough? I read it in Glen Zedikers book. For reference this is a 20" rifle length, though I'm guessing this gas port's kinda big. Going to gage it soon to confirm.

 

[Bevo]

What does it do with factory ammo?

 

[Basic user]

What does it do with factory ammo?

She's ok with factory stuff. In terms of rim health if that's what you mean.

 

[Xcount]

Nosler bought the Silver State Armory operation almost 10 years ago. Some caliber's changed brass at that time. Some stayed as rebranded Norma.

 

[Basic user]

I see.

 

[Basic user]

Ok, did an experiment because I wasn't satisfied that running too much powder was the entire cause of the back of the case head getting all tore up. The ejector and extractor in my opinion after screwing with it, were both too tough. Pulled the ejector, clipped a coil, cleaned and oiled it, and now it's smoother and not sprung as hard; didn't see the necessity of throwing cases into another dimension. Pulled the ejector and seen it had not only a high spring rate spring in there, but the top hat AND TWO donuts on the thing. Why? Was this a mistake? The thing was sprung WAYYY too hard. Threw a light polish on the claw, ditched both donuts, and now it feels pretty normal to me. I then went to the superlative arms gas block and turned it almost all the way off, to I think just 6 clicks open, in the restrictive mode. I then ran a 10mm bronze brush in a drill through the chamber and it came out clean as a whistle. Super smooth now.

Now, I went back to that same brass, cleaned up the faces of the bases with a little light sanding, and reloaded another entire ladder starting with just below the load that began to cause the brass damage; 43.4 grains of Varget. Loaded 43 to 43.8 in two tenths grain increments and the damage to the case face is minimal to non existent. Very pleased to see this. They also didn't get as carboned up either. They still got dirty but not like before. Going to try this one more time, (should have thought of this while I was at the range) but will shoot this load with the gas block totally closed off, to eliminate any possible violence from the bolt ripping the case out of the chamber possibly too fast or too hard. We'll see what if any damage is done to the brass then. Love these experiments.