Can you check my brass?

[m1ajunkie]

I came up with some .308 loads that shoot very well out of my .308 ar, but I am afraid they may be overpressure.

The five cases on the top are lc lr brass and this is the load:
178 amax
43.6gr varget
win wlr primer
2.81"

the four on bottom are wcc nato brass and they are:
175gr smk
43.4gr varget
win wlr primer
2.80"

The lc lr brass is 3x fired and the wcc is 5x fired. I am planning to retire this batch and start with some 1x fired wcc cases for the next batch. The lc lr cases are not shiny and slightly tarnished so I am thinking it should be easy to spot ejector/ extractor marks which are not present. The wcc show light ejector marks, but I noticed those showed up upon intial firing of the q3130 ammo. Ejection is at about 1-2 o clock, but all my empties land there now that I am running the 20" barrel. FWIW, I worked both these loads up to 44gr before I started getting cratered primers and gas leaking around the primer.

Pic:

 

[BOLTRIPPER]

Re: Can you check my brass?

dude...gassers beat the shit out of brass...what do you expect!

 

[m1ajunkie]

Re: Can you check my brass?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BOLTRIPPER</div><div class="ubbcode-body">dude...gassers beat the shit out of brass...what do you expect! </div></div>

Thats what I've been reading, but I want to make sure nothing looks out of the ordinary. I have seen the armalite document stating reasons for things like ejector, extractor marks, scratches on the brass and what not so I am still learning how to judge pressure correctly.

 

[maggitas]

Re: Can you check my brass?

I concur with bolttripper on this one. I am currently running Federal Brass with Fed 210M Primers Hornady 178 Amax in my TBA M40. My brass shows no pressure signs. When I shoot Federal Gold Medal Match factory ammo I get the same looking brass as your picture.

YMMV,

Johnn

 

[thefitter]

Re: Can you check my brass?

It's my understanding that with a semi all you can really evaluate reliably is primers. Those look OK to me.

I also have been told cratered primers are not that conclusive. Look for FLAT primers.

 

[EWP]

Re: Can you check my brass?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: thefitter</div><div class="ubbcode-body">It's my understanding that with a semi all you can really evaluate reliably is primers. Those look OK to me.

I also have been told cratered primers are not that conclusive. Look for FLAT primers.</div></div>

I think you have it backwards, flat primers can be a head space problem as well as high pressure but only high pressure can cause a primer to flow into the firing pin hole causing craters.

 

[thefitter]

Re: Can you check my brass?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: EWP</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: thefitter</div><div class="ubbcode-body">It's my understanding that with a semi all you can really evaluate reliably is primers. Those look OK to me.

I also have been told cratered primers are not that conclusive. Look for FLAT primers.</div></div>

I think you have it backwards, flat primers can be a head space problem as well as high pressure but only high pressure can cause a primer to flow into the firing pin hole causing craters. </div></div>

I'm not an expert in any sense, what I was told was that the size and tolerances of the firing pin can cause the cratering appearance.

Is it safe to assume that if you don't have flat primers at lower charges but do at higher charges that it's pressure not your head space?

If you had head space problems would you not see it at all charge weights?

 

[Grump]

Re: Can you check my brass?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: thefitter</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: EWP</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: thefitter</div><div class="ubbcode-body">It's my understanding that with a semi all you can really evaluate reliably is primers. Those look OK to me.

I also have been told cratered primers are not that conclusive. Look for FLAT primers.</div></div>

I think you have it backwards, flat primers can be a head space problem as well as high pressure but only high pressure can cause a primer to flow into the firing pin hole causing craters. </div></div>

I'm not an expert in any sense, what I was told was that the size and tolerances of the firing pin can cause the cratering appearance.

Is it safe to assume that if you don't have flat primers at lower charges but do at higher charges that it's pressure not your head space?

If you had head space problems would you not see it at all charge weights?

</div></div>

Ah, the joys of pressure signs voodoo and false positives and true negatives.

Everyone's right, sorta.

Without getting to the numbers of tolerances, yes, a primer can crater rather nicely with a safe load if there is a lot of clearance between the firing pin and its hole. Case in point--all the posts from worried people who just bought Remington 700s.

Yes, a primer can be flat if you are running something like .015 between your cartridge and the front of your chamber. It will NOT show up at all charge weights, but will show as a primer backed out--you guessed it--whatever your clearance is. That also is a case where a high fired primer is NOT a pressure sign. BTDT about 10 years ago. The square-cornered primers on the full-power loads changed to only slightly squared in the radius when I loaded for *that* chamber instead of for minimum cartridge dimensions.

Me, I worry about *any* ejector marks on brass, except in--you guessed it again--AR systems. Seems like something funky goes on in their chambers, and even factory ammo going slow enough often results in a small ejector mark. Even then, I carefully watch the velocity and back off if it is "too good" for the barrel length.

 

[m1ajunkie]

Re: Can you check my brass?

The velocity is a good point I forgot about.

I haven't had a chance to check my loads at there current load, but what would be considered "to good" for a 20" ar with the 175/178gr?

Prior to running 43.4gr and 43.6gr I had both loads at 43grs and was getting 2575 with the 175 and 2525 with the 178s. I won't know until tues but I would think these as they are now are around 2600 with the 175 and 2560ish with the 178, assuming they follow trends present in load development.

Grump, you are correct about ejector marks in the ar. I see somewhat random ejector marks when shooting factory ammo.

 

[thefitter]

Re: Can you check my brass?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Grump</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: thefitter</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: EWP</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: thefitter</div><div class="ubbcode-body">It's my understanding that with a semi all you can really evaluate reliably is primers. Those look OK to me.

I also have been told cratered primers are not that conclusive. Look for FLAT primers.</div></div>

I think you have it backwards, flat primers can be a head space problem as well as high pressure but only high pressure can cause a primer to flow into the firing pin hole causing craters. </div></div>

I'm not an expert in any sense, what I was told was that the size and tolerances of the firing pin can cause the cratering appearance.

Is it safe to assume that if you don't have flat primers at lower charges but do at higher charges that it's pressure not your head space?

If you had head space problems would you not see it at all charge weights?

</div></div>

Ah, the joys of pressure signs voodoo and false positives and true negatives.

Everyone's right, sorta.

Without getting to the numbers of tolerances, yes, a primer can crater rather nicely with a safe load if there is a lot of clearance between the firing pin and its hole. Case in point--all the posts from worried people who just bought Remington 700s.

Yes, a primer can be flat if you are running something like .015 between your cartridge and the front of your chamber. It will NOT show up at all charge weights, but will show as a primer backed out--you guessed it--whatever your clearance is. That also is a case where a high fired primer is NOT a pressure sign. BTDT about 10 years ago. The square-cornered primers on the full-power loads changed to only slightly squared in the radius when I loaded for *that* chamber instead of for minimum cartridge dimensions.

Me, I worry about *any* ejector marks on brass, except in--you guessed it again--AR systems. Seems like something funky goes on in their chambers, and even factory ammo going slow enough often results in a small ejector mark. Even then, I carefully watch the velocity and back off if it is "too good" for the barrel length. </div></div>

"pressure signs voodoo"... I like that.

What about in a M1A? I frequently see ejector marks with factory ammo. But I have never paid attention to them.

I will start hand loading for that platform in the next couple of weeks. I had planned on just watching the primers carefully.

 

[scotharr]

Re: Can you check my brass?

The brass and primers look fine to me. You indicated that you did get pressure signs .5gr higher. So, I'd say your current load is probably a max safe load and that could change if conditions change: hotter weather, etc.

 

[Grump]

Re: Can you check my brass?

I'm an M1A guy.

Factory ammo leaving ejector marks (like that big batch of once-fired 1990s FC a friend gave me back then...) is *usually* just a sign of soft-headed brass. A lot of head clearance can assist the process--the brass speeds back there and there's an impact component. I derive this "professional" opinion from some long clearance case body separations a few years ago--plenty of "skirt" to keep the gas contained, but UGLY ejector marks on loads that are modest by every measurement, including the all-important to me velocity for barrel length component.

If you have a Wilson gage, or are willing to caliper/mic loaded and fired rounds using the subtractive .40 S&W case trick, then it is a very, very good idea to measure the difference after firing, to evaluate any "squaring" or "flattening" of primers of all cases, then factoring in velocity.

Forgot who posted it above, but 2575 fps with 175s/178s out of a 20-inch tube is as fast as *I* would dare push them. A "fast" barrel is probably always also a higher-pressure barrel.

I stop at 2600 fps with that bullet weight out of a 22-inch barrel.

 

[m1ajunkie]

Re: Can you check my brass?

I was able to chrony my loads today.

175smk running right on 2600fps out of my 20".

178 amax running 2560fps out of my 20".

Getting velocities was about the only positive thing I did at the range today. I could not get any groups with my .308 better than 2.5". I feel this is all me today because the past few range trips I have been shooting 5 rounds right around an inch. Today, conditions were terrible. Mirage was bad, wind was blowing my target foward and back in the stand, and the grass was so tall in the field that blades of grass were in my line of sight with the target. I was beginning to think something was wrong, but I believe I had my scope mag to high for conditions, I didn't think about that until I was basically out of ammo.

I hope my loads are still shooting as good as they have been as I am planning to hit the 700yd range next thurs.

I did end the day with this 5 round group out of my .223 sdm ar:

 

[Grump]

Re: Can you check my brass?

Using a 56-gr water capacity on the cases and "default" burn rates, QuickLOAD predicts 2528 fps with your Varget/A-Max load out of a 20-inch tube. Pressure predicts safe.

Fudging burn rate to match your 2560 fps (not a huge difference-1.25% or something) puts the pressure right at absolute SAAMI max. Add .1 gr more powder and they are over spec.

That load also predicts a port pressure between 800 and 3,000 PSI higher than spec for an M1A, depending on whether you "translate" the piezo numbers direct to the CUP specs the military set not later than 1957, or add 2,000 to the numbers to match what QuickLOAD's numbers for loads tested for port pressure in the early 1980s. IOW, I ran published test results through QuickLOAD and the port pressure predictions there were almost exactly 2,000 PSI higher than the CUP numbers reported for those same loads, same brass, same velocities.

Had to fudge the burn rate a little more to get 2600 with your 175 SMK load. That shows overpressure, 61747 PSI piezo.

You can decide what to do with this. If any factory load with either bullet is slower than your handloads, I recommend backing off just a bit.

 

[m1ajunkie]

Re: Can you check my brass?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Grump</div><div class="ubbcode-body">Using a 56-gr water capacity on the cases and "default" burn rates, QuickLOAD predicts 2528 fps with your Varget/A-Max load out of a 20-inch tube. Pressure predicts safe.

Fudging burn rate to match your 2560 fps (not a huge difference-1.25% or something) puts the pressure right at absolute SAAMI max. Add .1 gr more powder and they are over spec.

That load also predicts a port pressure between 800 and 3,000 PSI higher than spec for an M1A, depending on whether you "translate" the piezo numbers direct to the CUP specs the military set not later than 1957, or add 2,000 to the numbers to match what QuickLOAD's numbers for loads tested for port pressure in the early 1980s. IOW, I ran published test results through QuickLOAD and the port pressure predictions there were almost exactly 2,000 PSI higher than the CUP numbers reported for those same loads, same brass, same velocities.

Had to fudge the burn rate a little more to get 2600 with your 175 SMK load. That shows overpressure, 61747 PSI piezo.

You can decide what to do with this. If any factory load with either bullet is slower than your handloads, I recommend backing off just a bit. </div></div>

Grump,

Thanks for the info. FWIW I am running a 20" lmt ar with a 5r rifled barrel. I don't have enough experience to know, but I have read the 5r has slightly greater velocitys than a regular barrel? Does that sound plausible?

 

[turbo54]

Re: Can you check my brass?

My method (right or wrong) to assess pressure is looking at the radius on the edge of the primers. Also, inspecting spent primers after they've been pressed out of the pocket. A little mushrooming is acceptable IMHO. Most NATO brass I've gotten has FLAT primers and a LOT of mushrooming, and I consider that high pressure. My loads don't do that.

Mt savage bolt gun with a 24" barrel gets 2525fps with a 180gr SMK over 42.5gr Varget, with a nice radius left on the primer, a *slight* mushroom, no ejector mark and an easy bolt lift.

On a sidenote... SAAMI specs indicate 308 to be higher pressure than 7.62x51 NATO, but my experience with spent brass from both tells me NATO ammo is actually hotter... for whatever that's worth...

 

[Grump]

Re: Can you check my brass?

Aw, Turbo, I'm thinking that a lot of that sharp cornering on USGI ammo is from a lot of empty headspace in the ammo/gun combo.

Primer fires, case grabs chamber walls forward, primer backs out and mushrooms, and then the pressure exceeds the slip/brass stretch point and the case squishes the primer's mushroom.

A proven, published load in .308 did that with my rifle, primers quite flat, until I compared length (to the shoulder) of fired and sized cases. The 'smith who chambered it said he put it halfway between military and SAAMI specs, to minimize the chances of slam-fire. Nope, it was closer to totally max chamber headspace. Backed out my sizer die an 1/8th-turn and primers looked much better and cases lasted longer than three reloads!!!

OTOH, I've obtained a few boxes of 1x-fired USGI match brass from people who picked them up at Camp Perry, and in both '06 and M118 varieties, primers always looked pretty flat. I blame the rifles.