I am using new Hornady brass and after firing it once, there are lots of scratches and marks on the brass from neck to the rim. There are lines running along side of brass for the entire length of the brass. Rim and bolt face side of brass both have significant marks. My gun is gassed properly, I am using adjustable gas block and the brass is ejected at 3.30-4 o'clock. I have attached pics of the brass, can someone tell me if this is normal for brass used in 308 AR-10 and if not, what I need to do to reduce marks on the brass?
AR-10 is chewing up my brass
- Thread starter dzz
- Start date
just because it throws the brass at 3-4 does not mean it is gassed properly. Turn down the gass and get a heavier buffer. But you may not be able to make the brass look better. AR10's are hard on brass
Is this happening to the next round in the magazine as the bolt strips the cartridge above, to the round being chambered as it feeds, or to the empty case as it ejects?
Have you tried a different magazine brand?
How does the feed ramp and chamber look? Polished? Sharp edges?
Tell us about the build and share pictures.
Have you tried a different magazine brand?
How does the feed ramp and chamber look? Polished? Sharp edges?
Tell us about the build and share pictures.
You have excessive pressure signs as well on the case head and cratering primers.
Is this a factory rifle or one you pieced together?
Is this a factory rifle or one you pieced together?
It could be a mag related issue on the length wise scuffs. Get a black sharpie and color the brass and put one round in the mag. Load it and eject it manually. Do it from an open bolt to simulate a regular bolt closure. Eject manually and see if you can identify anything.
Repeat with two or three rounds or more and see if that's it.
What it could be is the magazine spring is still really stiff and it's putting excess upward pressure especially with a full mag. If that's the case then load up the mags to full capacity and put them on the shelf for a week or two. Its probably just the rounds rubbing up against each other in the mag.
As for the load, it looks way too spicy.
Repeat with two or three rounds or more and see if that's it.
What it could be is the magazine spring is still really stiff and it's putting excess upward pressure especially with a full mag. If that's the case then load up the mags to full capacity and put them on the shelf for a week or two. Its probably just the rounds rubbing up against each other in the mag.
As for the load, it looks way too spicy.
Too much powder in those rounds, Hoss!
Look at the cratering in the primer. Lighten up the load and dial in your gas.
Look for a load that duplicates the LC Match 7.62. Runs great in semi’s like AR-10’s and SCAR’s.
But you are not beating up your brass nearly as bad as you are beating up your rifle!
Sirhr
Look at the cratering in the primer. Lighten up the load and dial in your gas.
Look for a load that duplicates the LC Match 7.62. Runs great in semi’s like AR-10’s and SCAR’s.
But you are not beating up your brass nearly as bad as you are beating up your rifle!
Sirhr
Did you peirce a primer in there some where? I see some primers that appear to have flowed into a void on the bolt face?
I put it together myself. Also, according to one post on another forum:
safe loads can have cratering. But it IS a sign that you are getting close to a place where you need to pay attention.
Cratering can be caused by:
1 - Weak firing pin spring.
2 - Thin or weak cup (CCI 400, Federal 200, and Rem # 6-1/2)
3 - Over sized firing pin hole in the bolt
4 - High pressure.
I am using CCI # 400 primers
Its unlikely you have a weak firing spring as the trigger is actually the firing pin spring unless you made a major change to whatever hammer spring came with your trigger. For reference I use a Hi Speed National Match trigger with the match spring set, which is extremely light, with no issues.
All large rifle primers are pretty much .027" thick. The only real difference from manufacturer to manufacturer is the cup height. I use CCI 200s as my AR-10 primer, with many of my loads over book max.
This leaves 2 remaining issues which are likely the issue.
Oversized firing pin hole is a big problem. I use a Toolcraft bolt and while not marketed as a high pressure bolt, it's worked well. I do have some mild cratering, but nowhere the extent you're seeing. If I was really worried, I would probably swap it for a JP.
High pressure in combination with a large firing pin hole is really very likely the issue here. Add in Hornady brass which is a bit softer in the head, it creates more issues. I will say your brass is really beat up. Unless that brass has seen a lot of firings, it should not be in that bad of shape. You are seeing a lot swipes and marks, which tells me you're over pressure. Swapping to Lake City brass will potentially cost you a bit of accuracy, but I have LC brass that has seen 5+ firings that looks pristine in comparison to your Hornady, and I do run some spicy loads.
In conclusion? If you want to run heavy loads, buy a high pressure bolt but also reduce your charge. You never did say what your loading is, but from appearances you're hotter than you should be.
Very true. I just can't feed my AR-10 expensive brass, and bought up 3000 pieces of LC over the years that only ever sees use in my AR-10. Other than being a gigantic PITA to prep and size the first time, it's been working great. I did feed it some Peterson at one point, but decided the accuracy improvement wasn't good enough to warrant the money spent. If I want to shoot for accuracy, I'll just use my bolt guns. The ARs are for beating up steel.
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Other posters have identified it but i'll chime in since I do a ton of precision gas gun work and PRS gas gun loading.
First, you have an old school oversized firing pin hole and firing pin. This isnt a problem in and of itself but it is going to mark most primers in loads above ~55-58k psi chamber pressure.
Second, you are using Hornady brass, which tends to be soft and easily flows into extractor grooves and get blasted into ejectors at higher pressures.
Third, you are running those rounds hot hot hot. the ring around the brass is from the case being driven into the bolt face HARD from pressure.
If you are going to do precision loading in a gas gun you really should be using tough brass like FC and utilize a high pressure bolt. Tuning with weights is generally required for the best results, you can buy tungsten and swap them into your buffer until you get the speed right. Most gassers really need a LOT of mass in a large frame to operate at tolerable speeds and to make brass last. You can also match this with a stiffer spring to slow down the cyclic rate, which will stop the extractor from yanking the rims.
Dont forget to size your brass with a RCBS small base die to bump those heads for smooth chambering and ejection. One thing that's common with gas guns is the head grows after a few firings and will no longer chamber freely and under unlocking will stick. Clickers in a bolt are bad, clicking at the case head in a gasser is a sure way to tear brass heads and rims off.
If you use a small base sizer die to bump heads, use tough brass, and tune your gun, there is no reason to not be able to get 10+ firings out of your brass. I shoot a JP LRI20 with FC brass and the brass still looks immaculate with the same set of 200 on its 15th+ firing. Alpha brass works too and has a tougher case head if you want to upgrade.
First, you have an old school oversized firing pin hole and firing pin. This isnt a problem in and of itself but it is going to mark most primers in loads above ~55-58k psi chamber pressure.
Second, you are using Hornady brass, which tends to be soft and easily flows into extractor grooves and get blasted into ejectors at higher pressures.
Third, you are running those rounds hot hot hot. the ring around the brass is from the case being driven into the bolt face HARD from pressure.
If you are going to do precision loading in a gas gun you really should be using tough brass like FC and utilize a high pressure bolt. Tuning with weights is generally required for the best results, you can buy tungsten and swap them into your buffer until you get the speed right. Most gassers really need a LOT of mass in a large frame to operate at tolerable speeds and to make brass last. You can also match this with a stiffer spring to slow down the cyclic rate, which will stop the extractor from yanking the rims.
Dont forget to size your brass with a RCBS small base die to bump those heads for smooth chambering and ejection. One thing that's common with gas guns is the head grows after a few firings and will no longer chamber freely and under unlocking will stick. Clickers in a bolt are bad, clicking at the case head in a gasser is a sure way to tear brass heads and rims off.
If you use a small base sizer die to bump heads, use tough brass, and tune your gun, there is no reason to not be able to get 10+ firings out of your brass. I shoot a JP LRI20 with FC brass and the brass still looks immaculate with the same set of 200 on its 15th+ firing. Alpha brass works too and has a tougher case head if you want to upgrade.
Small base sizing is also critic as Emrek says above.
If you are loading for semi-auto, you need to do FL resize with small base die. Not standard die. Not neck bump. Those tools/techniques are for bolt guns.
Sirhr
If you are loading for semi-auto, you need to do FL resize with small base die. Not standard die. Not neck bump. Those tools/techniques are for bolt guns.
Sirhr
The lines on the case might be feedramps or magazine lips
The primer cupping and the ejector mark could be overpressure rounds or just sharp ejector edges and an oversided firing pin hole
Before you get worried try some different brands of ammo and compare the cases
The primer cupping and the ejector mark could be overpressure rounds or just sharp ejector edges and an oversided firing pin hole
Before you get worried try some different brands of ammo and compare the cases
Everyone is always saying Federal is soft, I have a bunch and have been liking it although so far I have also been running my loads too hot.
The current FC GMM 308 brass with the blue primer sealant and nickel plated primer is harder brass than the 20+ Y/O GMM brass was. The brass that had the brass colored primer with no primer sealant was much softer brass.
I've been shooting this brass since the late 1970's. Been reloading it in a SR-25 since the mid 1990's and a GAP 10 since 2013.
I've been shooting this brass since the late 1970's. Been reloading it in a SR-25 since the mid 1990's and a GAP 10 since 2013.
I do remember "soft" FC brass from maybe 10-15yrs ago but recent stuff seems fine. I shoot lots of it.
One of the things that needs to be said out loud once in a while.... is that FC by itself doesn't mean anything.
In 308 and 223, there is more than one design and source from FC and some were not good for reloading while others are not.
In 308 and 223, there is more than one design and source from FC and some were not good for reloading while others are not.
