Ejector Extrusion Marks Question

[Fire4EffectCA]

Bullet: Sierra 168 gr
Brass: Once fired Mem16 7.62x51
Primers: Winchester WLR Large Rifle
Powder: IMR 4064, 41.5 gr
COAL: 2.800”

I have been away from rifle reloading for two decades and have returned recently and started with 308 Win. I obtained good accuracy with 5 shot groups at 100 yards yesterday, but noticed light ejector extrusion marks on about 1/3 of the fired case heads. I fired 5 rounds of factory loaded Mem16 7.62x51 to foul the barrel and none of these fired case show any sign of ejector extrusion marks.

Ejector extrusion marks on the case head are typically a sign of high pressure, but I am using the starting load of 41.5 gr recommended by IMR. The powder is fresh from Graff’s, but the primers are 20 years old. I have stored the primers indoors in a dry and cool location.

I am using a Redding Type S bushing resizing die with a 0.333 neck bushing. This gives me 0.0035 neck tension. I did load and chamber a few cartridges while releasing the BCG on a loaded magazine and the COAL did not decrease. The 2.800” COAL should be fine.

NOTE: I reloaded 20 Remington 308 cases also and about 1/3 of those cases exhibited the same signs.

I had a few old boxes of Federal GM308M I fired a while back through the same rifle and the ejector extrusion marks were more pronounced and the primers had the same cratering.

Any suggestion on what to look for?

 

[918v]

Maybe too much gas.

 

[Fire4EffectCA]

Maybe too much gas.

Why would there be too much gas with a starting load.

 

[918v]

Because the powder is too slow burning for your gas system. You’re shooting a M1A, right?

 

[Fire4EffectCA]

Because the powder is too slow burning for your gas system. You’re shooting a M1A, right?

I am shooting a Stoner SR-25.

 

[918v]

Same principle. Is your gas block adjustable?

 

[Fire4EffectCA]

Same principle. Is your gas block adjustable?

Yes, but if I turn it down the bolt will not lock back on the last round.

 

[straightshooter1]

Bullet: Sierra 168 gr
Brass: Once fired Mem16 7.62x51
Primers: Winchester WLR Large Rifle
Powder: IMR 4064, 41.5 gr
COAL: 2.800”

I have been away from rifle reloading for two decades and have returned recently and started with 308 Win. I obtained good accuracy with 5 shot groups at 100 yards yesterday, but noticed light ejector extrusion marks on about 1/3 of the fired case heads. I fired 5 rounds of factory loaded Mem16 7.62x51 to foul the barrel and none of these fired case show any sign of ejector extrusion marks.

Ejector extrusion marks on the case head are typically a sign of high pressure, but I am using the starting load of 41.5 gr recommended by IMR. The powder is fresh from Graff’s, but the primers are 20 years old. I have stored the primers indoors in a dry and cool location.

I am using a Redding Type S bushing resizing die with a 0.333 neck bushing. This gives me 0.0035 neck tension. I did load and chamber a few cartridges while releasing the BCG on a loaded magazine and the COAL did not decrease. The 2.800” COAL should be fine.

NOTE: I reloaded 20 Remington 308 cases also and about 1/3 of those cases exhibited the same signs.

I had a few old boxes of Federal GM308M I fired a while back through the same rifle and the ejector extrusion marks were more pronounced and the primers had the same cratering.

Any suggestion on what to look for?

You might want to measure the case volumes of at least 10 of those Remington cases to see if there's an issue like I found in some of the Remington cases I have. What I found was that they significant variance and averages less than most of the other brands I have, which if that's so in your case, it could be a pressure difference due to the smaller volumes even though you're using powder charges near the suggested starting load.

 

[918v]

Maybe the recoil spring is too strong. Is it a new rifle? Maybe it needs to be broken in. Or a lighter recoil spring installed.

Otherwise you’ll need a different powder like AR-Comp.

 

[Fire4EffectCA]

Maybe the recoil spring is too strong. Is it a new rifle? Maybe it needs to be broken in. Or a lighter recoil spring installed.

Otherwise you’ll need a different powder like AR-Comp.

The rifle is 27 years old. It is one of the first 100 SR-25's built by Reed Knight and Eugene Stoner.

I have found many older posts where reloaders are using IMR 4064 for the AR-10.

 

[isofahunter]

Couple of points to consider.

Mil cases tend to have thicker walls less internal capacity than commercial brass used in most reloading data. Safe load in commercial case can be HOT in Mil. I have reloaded a lot of Mil over the years and typically 3% lower vs commercial.

My AR10 with 4064 beat the piss out of my LC cases. Dropped 4064 for 4895 (faster burn) and so far better results.
Not sure how long your barrel is but my 16 inch was just not long enough for a good burn. My theory is the powder burned too long extending the pressure curve and the bolt was starting to unlock at the high end creating stress on case. Change in powder has shortened the curve allowing for pressure to drop more before bolt unlock. Better case life. My 2 cents based on what I have done and the result I experienced.

 

[Fire4EffectCA]

Couple of points to consider.

Mil cases tend to have thicker walls less internal capacity than commercial brass used in most reloading data. Safe load in commercial case can be HOT in Mil. I have reloaded a lot of Mil over the years and typically 3% lower vs commercial.

My AR10 with 4064 beat the piss out of my LC cases. Dropped 4064 for 4895 (faster burn) and so far better results.
Not sure how long your barrel is but my 16 inch was just not long enough for a good burn. My theory is the powder burned too long extending the pressure curve and the bolt was starting to unlock at the high end creating stress on case. Change in powder has shortened the curve allowing for pressure to drop more before bolt unlock. Better case life. My 2 cents based on what I have done and the result I experienced.

My barrel is 24". I actually loaded two different cases.

308 Remington nickel platted.
7.62x51 Men 762A

 

[Fire4EffectCA]

You might want to measure the case volumes of at least 10 of those Remington cases to see if there's an issue like I found in some of the Remington cases I have. What I found was that they significant variance and averages less than most of the other brands I have, which if that's so in your case, it could be a pressure difference due to the smaller volumes even though you're using powder charges near the suggested starting load.

Thanks. I will read up on how to measure case volume.

 

[straightshooter1]

Thanks. I will read up on how to measure case volume.

It's not really all that difficult. Here's how I do it:

1. Use fired cases with the primer left in (or better, install a primer upside down so no water goes into the primer).

2. Set the case on the scale and zero it.

3. Fill the case with water using a syringe or a small squeeze bottle that you can control a small flow/drips until there's a slight dome above the case mouth (don't spill any water or get any on the outside of the case).

4. Wick off the dome of water with the edge of a paper towel until the water appears level with the case mouth edge, no concave or convex shape (easy to see if there's a bright light reflection from the other side of you or use a flashlight to see).

5. Since you zeroed the scale with the case on it, the indicated weight is your "case volume". . .write it down.

Repeat the steps. 10 times give you a good idea of your average is.

Typical case capacities for a .308 range from ~54.0 grs - ~56.0 gr. Winchester brass tends to have more capacity due to their thinner case wall and will have a volume of ~57.5 grs and the Remington's I mentioned before were ~52.5 grs (just to give you some idea of what the differences can be).

 

[918v]

Just weigh the brass. RP should weigh around 165 grains. Men should weigh 175 grains.

 

[Matches Malone]

Bullet: Sierra 168 gr
Brass: Once fired Mem16 7.62x51
Primers: Winchester WLR Large Rifle
Powder: IMR 4064, 41.5 gr
COAL: 2.800”

I have been away from rifle reloading for two decades and have returned recently and started with 308 Win. I obtained good accuracy with 5 shot groups at 100 yards yesterday, but noticed light ejector extrusion marks on about 1/3 of the fired case heads. I fired 5 rounds of factory loaded Mem16 7.62x51 to foul the barrel and none of these fired case show any sign of ejector extrusion marks.

Ejector extrusion marks on the case head are typically a sign of high pressure, but I am using the starting load of 41.5 gr recommended by IMR. The powder is fresh from Graff’s, but the primers are 20 years old. I have stored the primers indoors in a dry and cool location.

I am using a Redding Type S bushing resizing die with a 0.333 neck bushing. This gives me 0.0035 neck tension. I did load and chamber a few cartridges while releasing the BCG on a loaded magazine and the COAL did not decrease. The 2.800” COAL should be fine.

NOTE: I reloaded 20 Remington 308 cases also and about 1/3 of those cases exhibited the same signs.

I had a few old boxes of Federal GM308M I fired a while back through the same rifle and the ejector extrusion marks were more pronounced and the primers had the same cratering.

Any suggestion on what to look for?

Just FYI, the Hornady manual as well as a few others with a COAL of 2.8 list around 41.5 grs of 4064 as near max load for a 168gr.

 

[whatsupdoc]

Is there brass extruding into the ejector hole or just a ring mark on the brass?
Sometimes when drilling the hole for the ejector there is a sharp edge that will
leave that kind of mark on the brass.

How far are you pushing the shoulder back on the case?

 

[Fire4EffectCA]

Just FYI, the Hornady manual as well as a few others with a COAL of 2.8 list around 41.5 grs of 4064 as near max load for a 168gr.

Interesting. The powder manufacturer (IMR) says 41.5 gr is a starting load, but Hornady says 41.5 gr is a max load for their 168 gr bullet. For the bullet I am using, the Sierra reloading manual calls out 43.4 gr as the maximum load. I think I will drop the amount of powder to 40.6 gr and try again.

 

[straightshooter1]

Interesting. The powder manufacturer (IMR) says 41.5 gr is a starting load, but Hornady says 41.5 gr is a max load for their 168 gr bullet. For the bullet I am using, the Sierra reloading manual calls out 43.4 gr as the maximum load. I think I will drop the amount of powder to 40.6 gr and try again.

I get very good results with 40.9 grs of IMR 4064 pushing 168 SMK's out of my bolt gun. But then, my COAL is at 2.860 (Lapua Brass that has case volume of 55.9 grs of H2O) for best groupings.

 

[Fire4EffectCA]

Is there brass extruding into the ejector hole or just a ring mark on the brass?
Sometimes when drilling the hole for the ejector there is a sharp edge that will
leave that kind of mark on the brass.

How far are you pushing the shoulder back on the case?

Not much. My SR-25 has a very tight chamber 1.632".

 

[mick243]

OP - are you certain that you got all the resizing lube off the reloads before firing , as a bit of lube on the brass can give signs of over pressure where none exists...

 

[918v]

Federal loads the MK316 Mod 0 load which is a 175SMK on top of 41.7grs of 4064 in a FC military case, same capacity as your MEN16. That load was designed for gas guns. Your load is lighter, yet causes problems. I would fix the mechanical issue rather than reduce the load to AK levels.

I would turn down the gas and try a lighter spring, and maybe a lighter buffer. Do you have an AR15? It’s a 2 min swap.

 

[Fire4EffectCA]

OP - are you certain that you got all the resizing lube off the reloads before firing , as a bit of lube on the brass can give signs of over pressure where none exists...

My brass is squeaky clean before reloading.

 

[Doom]

I load 43 gr of 4064 in LC brass with the 168 SMK, granted with a bolt gun. This is a mild load and approximates FGMM. One thing I would check is the case OAL. Assuming the issue is not powder, I think the issue may be case prep.

 

[Fire4EffectCA]

Federal loads the MK316 Mod 0 load which is a 175SMK on top of 41.7grs of 4064 in a FC military case, same capacity as your MEN16. That load was designed for gas guns. Your load is lighter, yet causes problems. I would fix the mechanical issue rather than reduce the load to AK levels.

I would turn down the gas and try a lighter spring, and maybe a lighter buffer. Do you have an AR15? It’s a 2 min swap.

I always bag and date my fired cases and the ejected brass from the Federal GM308M2 (175 gr SMK) I fired through this same rifle a few weeks ago looks perfect. This SR-25 is 27 years old and I would imagine the buffer spring has gotten weaker over time. I appreciate what you are saying, but I think I will start with the reduced load first. I have never had any malfunctions in the 27 years I have owned this rifle and it performs flawlessly with factory ammo. I know a lot of initial owners of the first few lots of SR-25's had issues with the tight chambers, but that resolved itself as the rifles were broken in. I did not have that issue, but Knight did modify my gas system when I returned the rifle for installation of a Milazzo-Krieger trigger.

 

[Fire4EffectCA]

I load 43 gr of 4064 in LC brass with the 168 SMK, granted with a bolt gun. This is a mild load and approximates FGMM. One thing I would check is the case OAL. Assuming the issue is not powder, I think the issue may be case prep.

I checked every case for for OAL after loading.
Double checked all powder measurements wth two scales.
All my cases were resized within less than 0.001" of each other.
All my cases were 0.001" concentric or better.

I wish other primers were available. I don't know what the Winchester WLR primers are adding to the mix.

 

[smoothy8500]

The powder manufacturer (IMR) says 41.5 gr is a starting load, but Hornady says 41.5 gr is a max load for their 168 gr bullet.

I believe the Hornady loads in question come from their "Service Rifle" load book, for M1A/Garand/AR10/Semi-auto rifles. I'm using a very similar load (Hornady brass instead) in my Aero M5 with Criterion Match bbl. I notice the same slight ejector swipes on some brass, but no cratered primers. Are you sure that the cases are not being excessively sized, shoulders only bumped back .003" or so?

 

[918v]

I always bag and date my fired cases and the ejected brass from the Federal GM308M2 (175 gr SMK) I fired through this same rifle a few weeks ago looks perfect. This SR-25 is 27 years old and I would imagine the buffer spring has gotten weaker over time. I appreciate what you are saying, but I think I will start with the reduced load first. I have never had any malfunctions in the 27 years I have owned this rifle and it performs flawlessly with factory ammo. I know a lot of initial owners of the first few lots of SR-25's had issues with the tight chambers, but that resolved itself as the rifles were broken in. I did not have that issue, but Knight did modify my gas system when I returned the rifle for installation of a Milazzo-Krieger trigger.

GM308 or GM762? There is a difference. The latter is supposed to be the MK316 load loaded with 4064.

But the more we talk the more I suspect your particular lot of 4064 is the problem or maybe your scale.

 

[918v]

I believe the Hornady loads in question come from their "Service Rifle" load book, for M1A/Garand/AR10/Semi-auto rifles. I'm using a very similar load (Hornady brass instead) in my Aero M5 with Criterion Match bbl. I notice the same slight ejector swipes on some brass, but no cratered primers. Are you sure that the cases are not being excessively sized, shoulders only bumped back .003" or so?

Hornady makes several different 308 cases, the heaviest of which weigh 187 grains and are the reason for the light charge data.

 

[smoothy8500]

Hornady makes several different 308 cases, the heaviest of which weigh 187 grains and are the reason for the light charge data.

True, they do have a wide variety of weights and is probably the reason. However, their book does have Service Rifle loads that are 5-7% lower than the standard "bolt action" loads. which may account for the discrepancy noted by the OP and what Matches Malone referred to. Regardless, semi-autos don't need to be hotrodded to bolt action levels and case volume limits safe loads.

 

[Fire4EffectCA]

GM308 or GM762? There is a difference. The latter is supposed to be the MK316 load loaded with 4064.

But the more we talk the more I suspect your particular lot of 4064 is the problem or maybe your scale.

I am using two scales to double check loads. I do have calibrated weights too.

 

[Fire4EffectCA]

I believe the Hornady loads in question come from their "Service Rifle" load book, for M1A/Garand/AR10/Semi-auto rifles. I'm using a very similar load (Hornady brass instead) in my Aero M5 with Criterion Match bbl. I notice the same slight ejector swipes on some brass, but no cratered primers. Are you sure that the cases are not being excessively sized, shoulders only bumped back .003" or so?

My resized cases measure 0” in a RCBS precision mic. Factory loaded Federal GM308M2 (175 gr SMK) measures -4 (0.004”) in a RCBS precision mic. Federal is bumping their shoulders back 0.004 more than me.

 

[918v]

Try a different powder if you can.

 

[smoothy8500]

Factory new cases are usually several thou less than SAAMI spec to ensure trouble-free chambering. Have you measured a fired case, with the gas closed/off to see what your actual shoulder bump should be?

 

[Fire4EffectCA]

Try a different powder if you can.

Powder selections are very limited now. I did pick up a pound of A2520 when I purchased the IMR 4064 from Graff.

 

[Fire4EffectCA]

Factory new cases are usually several thou less than SAAMI spec to ensure trouble-free chambering. Have you measured a fired case, with the gas closed/off to see what your actual shoulder bump should be?

Fired cases measure 1.632". I am only bumping back 0.002".

 

[smoothy8500]

You've ruled out the most likely culprits: Oversized cases, over-gassed, jammed bullets, and hot loads. You could bump down the load, since using the military brass and easily find a sweet-spot around 39.5gr to 41.5 of 4064 that still gives you that accuracy without stressing your brass. A lot of Service Rifle shooters in High Power and Tactical AR load at 40.5gr which is pretty popular at the 600yd distance.

 

[Matches Malone]

I believe the Hornady loads in question come from their "Service Rifle" load book, for M1A/Garand/AR10/Semi-auto rifles. I'm using a very similar load (Hornady brass instead) in my Aero M5 with Criterion Match bbl. I notice the same slight ejector swipes on some brass, but no cratered primers. Are you sure that the cases are not being excessively sized, shoulders only bumped back .003" or so?

It’s not just Hornady. It’s nosler, Lee and a few others have similar load data results.

 

[smoothy8500]

It’s not just Hornady. It’s nosler, Lee and a few others have similar load data results.

OK, that is interesting, since I took a quick look at Nosler's Load data and it still shows 44.5gr max (with their Nosler case). My older Sierra book shows similar loads, As do the current Hodgden/IMR website (Service Rifle Loads). Still, stick with time-proven High Power service load somewhere between 39.5 to 41.5 of 4064, no need to go beyond that.

Thanks for including your info.

 

[FLIGHT762]

I have the same rifle as you do. Bought it in 1993. Serial # is 202XX. An early gun. right out of the box, it was blowing primers with factory Federal GMM. I called Knight's. I was told to keep shooting it. I did settle in some. It has the same tight chamber as your rifle, fired cases measure +.001-.002 on the RCBS precision mic . My rifle does not have an adjustable gas port.

Gas guns cannot handle the pressures as well as a bolt gun without some modifications. In the early 2000's, we switched to some new lots of Hornady TAP 168 ammo. My SR-25 was working fine with the earlier TAP, but the new ammo was blowing primers with that ammo. I contacted Hornady L/E Division and was asked to send back the ammo for their testing. I received a new lot of ammo a couple of months later that shot fine in the rifle. I don't know what they changed, but the new ammo was fine.

I've had good luck with all of the regular, medium burning powders AR Comp, 8208XBR, 4895, 4064, Varget and Reloader 15. You just have to adjust you powder charges down some from bolt gun levels that are listed in most reloading manuals.

Your brass is thick brass, that will cause pressures to rise. The gun is telling you what's going on. Follow what you're seeing. Drop the powder charges a grain or so and re-check. Minor swipes are no big deal but the swipes that you are seeing means with the sharp edges on it means drop the powder charge a bit.

I have been reloading for this rifle since 1993. The rifle works fine with powder charges tailored to the brass.

The thickest brass types will fall into the 180-185 weight class (weighed with a fired primer in the case) Federal GMM, US 7.62 NATO brass, CBC etc. This heavier brass need a little less powder than the thinner cases like Winchester and Hornady.

 

[918v]

Powder selections are very limited now. I did pick up a pound of A2520 when I purchased the IMR 4064 from Graff.

A lot of people like AA2520 in their gas guns. I think your gas gun will like it.

 

[Fire4EffectCA]

I have the same rifle as you do. Bought it in 1993. Serial # is 202XX. An early gun. right out of the box, it was blowing primers with factory Federal GMM. I called Knight's. I was told to keep shooting it. I did settle in some. It has the same tight chamber as your rifle, fired cases measure +.001-.002 on the RCBS precision mic . My rifle does not have an adjustable gas port.

Gas guns cannot handle the pressures as well as a bolt gun without some modifications. In the early 2000's, we switched to some new lots of Hornady TAP 168 ammo. My SR-25 was working fine with the earlier TAP, but the new ammo was blowing primers with that ammo. I contacted Hornady L/E Division and was asked to send back the ammo for their testing. I received a new lot of ammo a couple of months later that shot fine in the rifle. I don't know what they changed, but the new ammo was fine.

I've had good luck with all of the regular, medium burning powders AR Comp, 8208XBR, 4895, 4064, Varget and Reloader 15. You just have to adjust you powder charges down some from bolt gun levels that are listed in most reloading manuals.

Your brass is thick brass, that will cause pressures to rise. The gun is telling you what's going on. Follow what you're seeing. Drop the powder charges a grain or so and re-check. Minor swipes are no big deal but the swipes that you are seeing means with the sharp edges on it means drop the powder charge a bit.

I have been reloading for this rifle since 1993. The rifle works fine with powder charges tailored to the brass.

The thickest brass types will fall into the 180-185 weight class (weighed with a fired primer in the case) Federal GMM, US 7.62 NATO brass, CBC etc. This heavier brass need a little less powder than the thinner cases like Winchester and Hornady.

I have several brands of 308 brass I have fired over the years and I decided to try some commercial Winchester 308 brass for the next reload. I had been waiting for a 0.331 neck bushing due to the Winchester brass being thinner. It came in and I loaded the following yesterday.

20 rounds with 168 gr Sierra SMK bullets and 40.5 gr of 4064 powder.

20 rounds with 168 gr Sierra SMK bullets and 41.0 gr of 4064 powder.

10 rounds with 168 gr Sierra SMK bullets and 41.5 gr of 4064 powder.

This time I will take my LMT MWS with a 20 inch barrel to test the loads. I received a new EZTUNE gas tube yesterday for this rifle and want to check it out. If my knees are better tomorrow I will head to the range.

Questions:

The 0.331 neck bushing for my Redding resizing die should be giving me 0.003” neck tension with the thinner Winchester brass. Do you taper crimp too or is the 0.003” neck tension sufficient for autoloaders?

Have you updated the recoil spring and buffer in your 1993 SR-25? I am still running the stock recoil spring and buffer.

Thanks for your input. I don’t know anyone who still shoots one of the early SR-25’s and it is great to hear your experiences.

 

[smoothy8500]

or is the 0.003” neck tension sufficient for autoloaders?

It's sufficient. I don't crimp any of my semi-auto loads, including the M14 and LR308. Verify the actual neck tension by comparing sized necks and then again after seating projectiles.

 

[Fire4EffectCA]

It's sufficient. I don't crimp any of my semi-auto loads, including the M14 and LR308. Verify the actual neck tension by comparing sized necks and then again after seating projectiles.

Sized Neck = 0.331"
Seated Bullet = 0.334"

 

[smoothy8500]

 

[FLIGHT762]

I also use a .331" bushing on my older Winchester brass. I do not crimp. Never had the need to crimp any of my autoloader loads.

The only up grade to the 1993 SR-25 is a Tubbs flat recoil spring.

 

[Fire4EffectCA]

Interesting day at the range. Instead of the Stoner SR-25, I took my LMT MWS out for ammo testing. It has a new 20 inch stainless steel 1:11.25″ RH 5R cut 7.62×51 barrel and a new EZTUNE gas system.

First off, all of the different loads, 40.5gr, 41.0gr and 41.5gr showed no signs of excess pressure. The EZTUNE gas system functioned perfectly with the reduced loads. The 40.5gr and 41.0gr loads were accurate and the 40.5gr was the most consistently accurate. I only fired a limited number of 41.5gr loads and the group size really opened up. It looks like the 40.5gr load performed the best.

 

[Cascade Hemi]

I may have missed it, are you using the original buffer spring? I see a new stock but don't know if you've ever changed the buffer spring.

 

[Fire4EffectCA]

I may have missed it, are you using the original buffer spring? I see a new stock but don't know if you've ever changed the buffer spring.

No, I am still using the original buffer spring. I am thinking about installing a Tubbs flat recoil spring.

 

[918v]

No, I am still using the original buffer spring. I am thinking about installing a Tubbs flat recoil spring.

I tried it, it went in but wouldn’t come out. Had to unscrew the buffer tube to get it out again. Fuck that.