Help with ejector marks and over-pressure

[Ronincjn]

Hello all,

I have spent the last few months practicing my reloading and trying to develop a LF hunting round for both deer and pig here in CA. I have not had a great amount of success, I have done several pressure ladder test with the Maker 85gr TREX w/H335 as well as 110gr Lehigh CC w/XBR. I'm using an AR platform, SW MP-15 lower with a PSA 18" 6.5G upper. I originally had to send the upper back because it would not cycle Hornady American Gunner ammo even when fully gassed. PSA expanded the hole in the barrel, and for the life of me I can't remember to what size. I have not touched the gas block since it has been returned to me, but I'm pretty sure it is fully open and could be a reason for the ejector marks. But, I find it weird that all three of the 85gr test it showed very little consistency in over pressure signs. These test have been done between 50-65F in the same location.


Test #1 85gr
Bullet - 85gr TREX tipped
Brass - once fired hornady
primer - CCI 450
powder - H335
brass length - 1.515
COAL: 2.267



Starting load 28.0gr increase by 0.2gr to a max of 31.8gr (20 rounds). Each charge will be accompanied by its velocity.

28.0 --- 2563
28.2 --- 2571
28.4 --- 2603
28.6 --- 2624
28.8 --- 2640
29.0 --- 2647
29.2 --- 2663
29.4 --- 2681
29.6 --- 2721
29.8 --- 2766
30.0 --- 2757
30.2 --- 2794
30.4 --- 2791
30.6 --- 2829
30.8 --- 2821
31.0 --- 2895
31.2 --- 2904
31.4 --- 2925
31.6 --- 2945
31.8 --- 2987 (only round I saw a pressure sign, light ejector mark)

Looks like I had a pressure spike between 30.8 and 31gr (74fps) ejected brass looked fine, no excessive pressure signs.

Test #2 85gr
11 rounds using same components but adjusting COAL/CBTO - to give me 2.260/1.663. Starting at 28gr and increasing at 0.3gr to 31.0.

28.0 - 2488
28.3 - 2532
28.6 - 2608
28.9 - 2600
29.2 - 2625
29.5 - 2662
29.8 - 2674
30.1 - 2699
30.4 - 2750
30.7 - 2797
31.0 - 2785

Very very light ejector mark on case head at 31.0.

Test #3 85gr
85gr TREX

Powder: H335
primer: CCI450
Brass: 1-fired Hornday
trim/lenght: 1.512
COAL: 2.260

Pressure string:
28.5-2540
28.8-2601
29.1-2638
29.4-2637
29.7-2720
30.0-2738
30.3-2731

I stopped at 30.3 because I was seeing shiny ejector marks starting at 29.7gr and getting progressively worse (half moon and full circle)

Test #1 - 110 Lehigh CC
110-Lehigh CC
powder: XBR
primer: CCI450
Brass: 2-fired Hornady
trim/length: 1.511
COAL: 2.255

Pressure string:
26.1-2296
26.4-2324
26.7-2358
27.0-2373
27.3-2406
27.6-2412
27.9-2460
28.2-2482
28.5-2522

Started showing some light ejector marks around 27.3 and became more noticeable as the charge increased, primers all look good with a spike (48FPS) between 27.6 and 27.9gr.


I have attached two pictures from this last test showing the ejector marks, these are the most aggressive marks I have witnessed to date. I feel like I should be able to continue to increase the charge based on other load data but at this point it just doesn't seem safe. I know that every barrel reacts differently to powder, bullet and pressure. So, perhaps that is where my problem lies. Any help/insight would be appreciated.

Thanks,
Ronin

Caseheadex1.jpg
Caseheadex2.jpg

[Lemonaid]

Short version is there are two main things that will cause ejector swipe and extractor swipe in a gas gun. One is over pressure in the chamber, the other is due to execess gas going through the system causing the bolt to unlock and extraction to start not at a optimal time. (At least that's what I was told). So if velocity from your load is at a safe level according to trusted load data, it's likely a gas adjustment problem.

[A5BLASTER]

Hello all,

I have spent the last few months practicing my reloading and trying to develop a LF hunting round for both deer and pig here in CA. I have not had a great amount of success, I have done several pressure ladder test with the Maker 85gr TREX w/H335 as well as 110gr Lehigh CC w/XBR. I'm using an AR platform, SW MP-15 lower with a PSA 18" 6.5G upper. I originally had to send the upper back because it would not cycle Hornady American Gunner ammo even when fully gassed. PSA expanded the hole in the barrel, and for the life of me I can't remember to what size. I have not touched the gas block since it has been returned to me, but I'm pretty sure it is fully open and could be a reason for the ejector marks. But, I find it weird that all three of the 85gr test it showed very little consistency in over pressure signs. These test have been done between 50-65F in the same location.


Test #1 85gr
Bullet - 85gr TREX tipped
Brass - once fired hornady
primer - CCI 450
powder - H335
brass length - 1.515
COAL: 2.267



Starting load 28.0gr increase by 0.2gr to a max of 31.8gr (20 rounds). Each charge will be accompanied by its velocity.

28.0 --- 2563
28.2 --- 2571
28.4 --- 2603
28.6 --- 2624
28.8 --- 2640
29.0 --- 2647
29.2 --- 2663
29.4 --- 2681
29.6 --- 2721
29.8 --- 2766
30.0 --- 2757
30.2 --- 2794
30.4 --- 2791
30.6 --- 2829
30.8 --- 2821
31.0 --- 2895
31.2 --- 2904
31.4 --- 2925
31.6 --- 2945
31.8 --- 2987 (only round I saw a pressure sign, light ejector mark)

Looks like I had a pressure spike between 30.8 and 31gr (74fps) ejected brass looked fine, no excessive pressure signs.

Test #2 85gr
11 rounds using same components but adjusting COAL/CBTO - to give me 2.260/1.663. Starting at 28gr and increasing at 0.3gr to 31.0.

28.0 - 2488
28.3 - 2532
28.6 - 2608
28.9 - 2600
29.2 - 2625
29.5 - 2662
29.8 - 2674
30.1 - 2699
30.4 - 2750
30.7 - 2797
31.0 - 2785

Very very light ejector mark on case head at 31.0.

Test #3 85gr
85gr TREX

Powder: H335
primer: CCI450
Brass: 1-fired Hornday
trim/lenght: 1.512
COAL: 2.260

Pressure string:
28.5-2540
28.8-2601
29.1-2638
29.4-2637
29.7-2720
30.0-2738
30.3-2731

I stopped at 30.3 because I was seeing shiny ejector marks starting at 29.7gr and getting progressively worse (half moon and full circle)

Test #1 - 110 Lehigh CC
110-Lehigh CC
powder: XBR
primer: CCI450
Brass: 2-fired Hornady
trim/length: 1.511
COAL: 2.255

Pressure string:
26.1-2296
26.4-2324
26.7-2358
27.0-2373
27.3-2406
27.6-2412
27.9-2460
28.2-2482
28.5-2522

Started showing some light ejector marks around 27.3 and became more noticeable as the charge increased, primers all look good with a spike (48FPS) between 27.6 and 27.9gr.


I have attached two pictures from this last test showing the ejector marks, these are the most aggressive marks I have witnessed to date. I feel like I should be able to continue to increase the charge based on other load data but at this point it just doesn't seem safe. I know that every barrel reacts differently to powder, bullet and pressure. So, perhaps that is where my problem lies. Any help/insight would be appreciated.

Thanks,
Ronin

[ATTACH=CONFIG]16411[/ATTACH]
[ATTACH=CONFIG]16412[/ATTACH]

Check the gas block if it's full open, back it in to half closed and try your highest charge again and see what it does.

[Ronincjn]

Check the gas block if it's full open, back it in to half closed and try your highest charge again and see what it does.

Short version is there are two main things that will cause ejector swipe and extractor swipe in a gas gun. One is over pressure in the chamber, the other is due to execess gas going through the system causing the bolt to unlock and extraction to start not at a optimal time. (At least that's what I was told). So if velocity from your load is at a safe level according to trusted load data, it's likely a gas adjustment problem.

This will be the next thing to cross off the list. I will reload the charges were I started to see the ejector mark form with the gas half closed. I have also attached another photo of a casing of the Hornady American Gunner I shot the same day. Primer is flat, not all the hornady primers were flat, and not even a light kiss of an ejector mark. I would think if it was an over-gassing issue it the ejector mark would be present on the hornady factory ammo as well. This ammo is on more or less 2450fps from my rifle.

Factory Hrndy Case head.png

[VASCAR2]

Ejector mark on 6.5 Grendel cases in the AR-15 are not uncommon. Sometimes the ejector mark on case heads is attributed to a very stout ejector spring.

[41bear]

I have this question for y'all, why not close the gas off when pressure testing to eliminate the gas part of the equation?

[Ronincjn]

I have this question for y'all, why not close the gas off when pressure testing to eliminate the gas part of the equation?

[Lemonaid]

I have this question for y'all, why not close the gas off when pressure testing to eliminate the gas part of the equation?

Because it's a pain to extract or eject with no gas.

[VASCAR2]

https://www.shootingillustrated.com/articles/2018/7/23/ar-15-gas-ports-impacts-on-accuracy-and-velocity/