How can I get lower pressures?

[m1ajunkie]

I have a load for 77gr smk's in .223 that I really like the accuracy of, but it's showing signs of overpressure.

I am loading:
77gr smk
23.7gr varget
Winchester small rifle primers
Lake city brass
2.252-2.257" Overall

Here is a pic of the brass. You will notice two different types of brass and that is what my question is about.

In the pic above, the 3 pieces of brass to the left have a headstamp that is "LC", year, nato cross, and then 3 circles imprinted in equal thirds around the rim. The four pieces to the right are LC and the year equally spaced in quarters around the case, these were from federal xm193.

In the 65 degree weather the types of cases like the three on the left were not showing ejector marks, but almost every primer had a small nipple in it. The cases like those 4 on the right don't show primers nippling, but are showing ejector marks. I still feel like the primers look like normal as far as looking flat. I fired 30 rounds this weekend to test my load more in depth.

Are these to hot for an ar at the way they stand?

Could I go to some kind of commercial brass and possible reduce the pressure? I have lots of privi brass that I could try out.

 

[Falar]

Re: How can I get lower pressures?

NATO brass has more volume, not the other way around.

There is info on case capacity with 5.56/.223 brass here:

http://www.6mmbr.com/223Rem.html


Also, check this link and see #5:

http://www.armalite.com/images/Tech Notes/Tech Note 17, Marring of Cartridge Cases, 960729.pdf

When I fire M855 and M193 it almost always has those marks on the base of the brass. IF, and this is a big if, your rifle has a NATO chamber, that load shouldn't be overpressure with that brass.

 

[m1ajunkie]

Re: How can I get lower pressures?

I'll add, these cases were free of any marks prior to loading my handloads. I took special care to select cases that would not give a false reading.

The barrel on my rifle is a compass lake engineering, and they recommended I go with the CLE chamber when I had the barrel made. I did so because they told me it would basically shoot anything I would run through it.

"Military 5.56x45 brass often, but not always, has thicker internal construction, and slightly less capacity than commercial .223 Rem brass." This is a quote from the 6mm br website, and this is what I've always heard but I'm new to reloading so I just want to start out correct.

I am getting 2700fps out of a 20" barrel with this load which I am happy with, but I don't want to be unsafe. Falar, are you saying I am okay with the loads as is?

 

[Falar]

Re: How can I get lower pressures?

They have a chart farther down on that 6mmbr page where they actually measured the capacity of various lots of brass. #1 for internal volume was LC 06. I've measured my LC 06-09 and it is right in line with their results.

Did you look at my other link? Allow me to quote straight from it:

GENERAL: Cartridges fired in AR-10 and M16 family firearms bear characteristic
scratches and marks which shooters sometimes think indicate defects.
FACTS
The following scratches and marks are typical with ArmaLite patent firearms, from a variety of
manufacturers, and do not indicate defects:
1. Light scratches along the length of the cartridge body. Caused by contact with magazine feed
lips or another cartridge during feeding.
2. 2 dents and related scratches on neck. Caused by neck striking 2 locking lugs during
extraction. The Ejector forces the case to the side, causing the contact.
3. Random circumferential scuffing of body. Caused by case brushing past chamber mouth
during feeding.
4. Dent on case body or mouth. Caused by case contacting upper receiver during ejection.
5. Circular mark on edge of base, with shiny brass or shaved brass in evidence. Caused by case
being pressed into ejector hole, with some burnishing or cutting as the bolt rotates.
6. Scratches or slight rim deformation caused by the extractor snapping over rim, and
the energy applied during extraction.
7. Light protrusion of primer metal around the firing pin strike (cratering). Caused by clearance
between the firing pin and firing pin hole; varies depending on primer hardness and cartridge
pressure.

IMO your loads would be safe in a NATO chamber. I don't know anything about the specs of the chamber you listed is in your barrel. Per the tech note from ArmaLite that I posted above, I don't sweat those circular marks on the cases in MY AR15s, which all have NATO chambers. I see it very frequently in NATO spec factory loads.

If you are uncomfortable with it start loading less and less powder until you find the point when they go away. If the velocity is unnacceptable at that point perhaps try a different powder.

According to quickload there are several powders that will provide more velocity with less pressure with 77gr SMKs in NATO brass.

 

[m1ajunkie]

Re: How can I get lower pressures?

I read both links, but didn't make it down to the water table on 6mm br because I thought I had read all there was about brass.

The armalite link made me feel better about the marks on the cases. I am unsure why the xm193 cases show the marks, but why do the other lake city cases not show the marks? Until reading that article I was under the impression that the ejector marks were a good way of indicating overpressure.

If the ejector mark is not an accurate sign in an AR, what else should I be looking out for in addition to the primer condition? I'm guessing if the load is really hot the rifle will fail to cycle or I will get stuck cases?

FWIW, I tested my load all the way up to 24gr of varget last week before the pressure signs got to be more than I was comfortable with. 23.7gr looked good in the 10 rounds I shot in that test so I loaded these up to get a more in depth sample.

 

[Falar]

Re: How can I get lower pressures?

If you start seeing truly flattened primers you are probably a full grain or so over max. Other than that, an ejection pattern closer to 12-1 o'clock and unusually strong recoil are the other signs you go by.

 

[m1ajunkie]

Re: How can I get lower pressures?

Thanks for the help. I haven't seen any fully flattened primers yet so I feel better about my load.

 

[frankythefly]

Re: How can I get lower pressures?

I weight sort all of my LC brass I have found year to year lots differ quite a bit. I try to get all my within .3grns. Also Varget differs quite a bit from lot to lot, so if you run out of varget and get more chances are the lot will be different and so will you velocity/pressure. Did you measure those cases with the markings on them? Did they stretch any differently in terms of length than the other ones? Also What is the length of your gas tube?

 

[m1ajunkie]

Re: How can I get lower pressures?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: frankythefly</div><div class="ubbcode-body">I weight sort all of my LC brass I have found year to year lots differ quite a bit. I try to get all my within .3grns. Also Varget differs quite a bit from lot to lot, so if you run out of varget and get more chances are the lot will be different and so will you velocity/pressure. Did you measure those cases with the markings on them? Did they stretch any differently in terms of length than the other ones? Also What is the length of your gas tube? </div></div>

I just got a chance to go out and measure the pieces of brass. There was no difference between either type of brass as far as length. The measurements were between 1.740" and 1.746", and my target when trimming is roughly 1.74".

ETA: I measured the diameter just past the rim of the fired rounds. All were at .375", while a newly resized round was at about .374-.3745"

This rifle has a rifle length gas system.

I got some cci primers I am going to try out to see if they reduce the nippling in the primers. I have heard that winchester and federal are the hottest out there so maybe the cci's will help.

Either way, from some of the advice I am getting I feel like these may be good to go, but right on the verge of to much. Ejection is normal and I haven't experienced any extra recoil.

 

[nhassey48]

Re: How can I get lower pressures?

moly

 

[m1ajunkie]

Re: How can I get lower pressures?

I'm sorry for the newb questions, but I don't have any where else to ask advice in this area.

Here is a pic comparing once fired SSA 77gr mk262 clone cases, my the brass from my load, and 2 pieces of resized brass with an unfired primer ready to be loaded. Do my primers look overly flat? Compared to the factory load, they look the exact same to me. The more I read the more confident I get in this load.

 

[gunsnjeeps]

Re: How can I get lower pressures?

I'd say they look good from the pictures.

 

[pshell]

Re: How can I get lower pressures?

Did you work up to that load? If so, did the lower charge weights have the shinny spots on the case head?

I was never able to get my AR to show signs with 69 SMK's and Varget (did get harder recoil and different ejection pattern, so it did show signs just not in the brass) but I can with 77 SMK and Ramshot Tac. I start to get ejector marks in the brass at 24 grs of Tac in Lapua brass shooting 77 SMK out of an 18'' barrel. At all charge weights below 24, the shinny spot in the case head is not present.

 

[m1ajunkie]

Re: How can I get lower pressures?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: pshell</div><div class="ubbcode-body">Did you work up to that load? If so, did the lower charge weights have the shinny spots on the case head?

I was never able to get my AR to show signs with 69 SMK's and Varget (did get harder recoil and different ejection pattern, so it did show signs just not in the brass) but I can with 77 SMK and Ramshot Tac. I start to get ejector marks in the brass at 24 grs of Tac in Lapua brass shooting 77 SMK out of an 18'' barrel. At all charge weights below 24, the shinny spot in the case head is not present. </div></div>

Yes, I started at 22.5gr and worked up to 24gr where accuracy went from basically 1" at 23.7/8gr of varget to about 2.5". Groups never dropped below 1.5" until 23.7gr, anything under that and my 10 round groups were all at 1.5". (all testing at 100yds) As far as the marks on the cases, they were present at all levels, and after reading the armalite link I believe it is something that my rifle does normally. I believe the ejector marks are a hair worse at 23.7gr, and my primers are showing nipples now.

I have loaded some cases to try out this weekend with cci primers that are supposed to be a little harder to resist piercing.

 

[sandwarrior]

Re: How can I get lower pressures?

m1ajunkie,

First, if you can measure the bullet ogive to lands (OAL). If the bullet is starting in the lands then you'll have higher pressures. If you don't have the Stonypoint tools, then start by just barely sizing down a case 1/32nd or so down the neck. Just enough to hold a bullet firm but not hard. Seat a bullet in the case (no primer or powder) to where it's down in the neck but not short enough to feed from a magazine. gently chamber the case and let the lands push the bullet down into the case. Remember too much grab on the bullet it will stick in the lands. You should be below 2.226" to fit in a standard magazine. So, if you are longer than 2.226 then that is good, as it gives your bullet a little running jump to hit the lands.

There would be two ways to reduce pressure here. One is to reduce powder. BTW, Hodgdon shows 23.7 gr.as max in a .223 chamber. As noted if you have the 5.56 NATO you can go higher. There is more 'jump' from the case to the lands (read: longer leade/throat). The other way to reduce pressure is to seat the bullets a little deeper. With 23.7 gr. of Varget and 77 gr. SMK's, I know you can. Not to worry, with the tanget ogive of SMK's they will make the jump just fine and not cause accuracy issues.

Personally, I use 25.5 gr. of RE-15 behind 75's/77's in a 16" barrel for a velocity of 2690. It's a bit tricky trying to compare loads but I'm thinking, that under normal circumstances, you should definitely be within the pressure range of 5.56 and it sounds like you may be at the very top of the .223 range.

Edit:

As far as case volume, I've found the 95 gr. Winchester cases to generally be the roomiest. Some LC is like, other lots it's thicker. The only way you can produce some match ammo is to sort cases by lots or volume. Just remember all the lots vary from each other. I've had most everything range from 92 gr. up to 109 gr. That is a lot of volume change. This is why after years of reloading this stuff I typically recommend seeing if you can get LE surplus Winchester as it usually runs 95-98 gr.
For non-match ammo you'll just pretty much have to load down just a bit and get what you get. Fortunately, volume doesn't make as big of difference as volume of powder.

-good luck.

 

[Graham]

Re: How can I get lower pressures?

It's almost impossible to predictably tell pressure signs in an AR based on reading the primer alone. To drop pressure you could go to Moly bullets, but I wouldn't advise it. Because if you're not blowing primers and the primers still show a radius, you're probably OK. Different AR's with different firing pins will do all kinds of things to .223 primers that have nothing to do with pressure signs. Consider that Varget may be a tad slow for your gas gun with the gas port where it is located now, so you might be on the verge of hard cycling. Change powders.

 

[m1ajunkie]

Re: How can I get lower pressures?

Sandwarrior,

Thanks for the info. I don't have the tools to measure correctly at this time so I will try the bullet trick.

I had these loaded a hair longer than 2.25", so I may load some up for this weekend that are a little shorter.

 

[sandwarrior]

Re: How can I get lower pressures?

I forgot to mention, on the 25.5 gr. load of RE-15, that is a 5.56 NATO chamber. That load is too hot in my Savage 12 FV. Even though the lands have eroded back almost to where the 5.56 chambers are.