Ejector Swipe Question

[chris514scott]

So I have been trying to work up a load on a 6.5 creedmoor barrel for my AXMC. It seems like I'm getting primer swipe no matter what. I have loaded the rounds and ejected them without firing to make sure they were not to long. The case on the left is 39gr H4350 at 2677fps. The case on the right is 41gr H4350 at 2791. 147gr bullets in Peterson fat neck brass. I don't want to go below the 39gr but if I'm getting swipe no matter what should I just say screw it and run the 41gr? Both have an awesome group with single digit ES/SD.

Thanks for any i

 

[chris514scott]

More pics

 

[Huskydriver]

Sfp or lfp?

 

[chris514scott]

Sfp or lfp?

Large

 

[Deleted member 10043]

Dat a hota rounda

 

[TheOfficeT-Rex]

What's the headspace difference between fired and size but unfired?

Was it consistent in all loads from 39 to 41?

Speed seems about right at 2650, but almost 2800 with a 147 feels like it should be hot (I dont shoot 147s). If youre chasing speed, I noticed I could get more speed with less pressure marking from RL16 vice 4350.

 

[Steel head]

2800 with 147’s in 6.5CM is quite spicy.
Same speed and bullet in my long throated 260 with roomy brass is getting spooky with H4350.

I second the R16 recommendation.

With R16 was able to get to just under 2890 with 147’s before pressure hit and I backed down to 2800 as accuracy was there and SD’s are worthy of a temple.

 

[McCrazy]

As others have said you are getting pretty high velocities. What is the length of your barrel?

What is the "primer swipe" you speak of?


The case on the right definitely has significant primer flattening and cratering. You definitely need to back off from that.

Both cases have noticeable ejector marks but I'm not seeing any ejector swipe. Possibly you just have a sharp ejector that is cutting into your brass.

 

[Dooby]

So I have been trying to work up a load on a 6.5 creedmoor barrel for my AXMC. It seems like I'm getting primer swipe no matter what. I have loaded the rounds and ejected them without firing to make sure they were not to long. The case on the left is 39gr H4350 at 2677fps. The case on the right is 41gr H4350 at 2791. 147gr bullets in Peterson fat neck brass. I don't want to go below the 39gr but if I'm getting swipe no matter what should I just say screw it and run the 41gr? Both have an awesome group with single digit ES/SD.

Thanks for any i

Did you turn down the "fat neck"? Just speculating here, but is it possible that if no neck turning on fat neck, possible to cause pressure signs?

 

[clcustom1911]

When I was doing load development for the 147 with H4350, I too noticed overpressure signs when the velocity was 2775+ out of my 24" Proof Research barrel. Even Black Hills 147 is down at at around 2625 or so. I'm probably going to back my loads down to 2650 as I currently have them running with 41.5gr about 2725-2750 depending on temperature, etc.

 

[Cerwinski]

I wouldn't think those loads would be causing those issues. I shoot 41.6 in my HMR and get right around 2700 FPS. What are you getting your velocity readings with? Maybe cross-check with a different chronograph to confirm. Also check for carbon buildup. I have a Grendel that really starts mangling brass if I let carbon get out of control. When I keep it in check the brass comes out fine. Just a few suggestions.

 

[John Glidewell]

Learned this in David Tubbs interview. Take fired case and try to drop a new bullet in it. If it does not drop in the case then your case necks are being kept from fully expanding and need to be turned. You said you got the fat necks too, did you turn them before shooting? If not, I suspect, as mentioned above, the fat necks are causing the pressure issue.

 

[chris514scott]

Sorry for the late reply everyone. I needed to get measurements to answer the questions. Thanks for all the replies so far. Barrel is 26"

What's the headspace difference between fired and size but unfired?

Was it consistent in all loads from 39 to 41?

Speed seems about right at 2650, but almost 2800 with a 147 feels like it should be hot (I dont shoot 147s). If youre chasing speed, I noticed I could get more speed with less pressure marking from RL16 vice 4350.

Base to Datum Unfired is 1.5315
Base to Datum Fired is 1.535.
Consistent from 39 to 41

Did you turn down the "fat neck"? Just speculating here, but is it possible that if no neck turning on fat neck, possible to cause pressure signs?

Have not turned necks yet.

I wouldn't think those loads would be causing those issues. I shoot 41.6 in my HMR and get right around 2700 FPS. What are you getting your velocity readings with? Maybe cross-check with a different chronograph to confirm. Also check for carbon buildup. I have a Grendel that really starts mangling brass if I let carbon get out of control. When I keep it in check the brass comes out fine. Just a few suggestions.

Readings are from a LabRadar

No carbon buildup. Barrel has very few rounds on it.

Learned this in David Tubbs interview. Take fired case and try to drop a new bullet in it. If it does not drop in the case then your case necks are being kept from fully expanding and need to be turned. You said you got the fat necks too, did you turn them before shooting? If not, I suspect, as mentioned above, the fat necks are causing the pressure issue.

Just tried this. Bullet does not drop in freely. Tad bit of pressure and it slides in. I measured outside neck diameter on unfired and fired brass.

Outside neck diameter Unfired is .293
Outside neck diameter Fired is .296

 

[John Glidewell]

I would turn the necks. I had this happen with 2 rifles and turned the necks to .0125 or .013 and the issue went away and they were shooting little groups again.