ejector marks

[GW Hunter]

I'm in the process of developing a copper bullet load for my Weatherby 7mm. Using the Barnes 150 gr TSX, I loaded up 3 bullets each of IMR 7828SSC.(My rifle loves that powder...) starting at 72gr up to 74.5 gr in .5 gr increments. My primers are Remington 9 1/2M. While my primers never showed any fatigue, I started to get really faint ejector marks at 73gr and increasing more visible with each progressive load. They were quite obvious at 74.5 gr. Bolt lift and cartridge ejection, however, never changed. It was the same as it always has been and the shells showed no sign of fatigue either. Should these ejector marks be a concern?

 

[Barrelnut]

Should these ejector marks be a concern?

I think so. The back of the case is moving differently than the body and shoulder during fire. The case body expands and grips the sides of the chamber, the case head them moves rearward and slams into the bolt face. I fit slams too hard, you get the ejector marks. Now if it is a new case that hasn't expanded before, the body and shoulders may have more room and spring to spring back and not exhibit hard bolt lift or extraction, but on the next firing they might. Non of this maynot really hurt anything, just loose some case life and primer pockets might go sooner. I IMO shiny ejector marks are a sign of too much pressure.

How long are the bullets seated? Seating a little deeper may lower pressure some.

 

[GW Hunter]

Thanks for the reply. The bullets are seated at .524. C.O.L. is 3.353.

 

[GW Hunter]

Barrelnut, when you say seat deeper, how much are you talking about?

 

[Barrelnut]

GW,

I just looked up the 7mm Weatherby Mag with 150 Barns on their web site and it says the the C.O.L. should be 3.250. So you are quite a bit long. And my understanding is that Barns bullets like a long jump and that might be to help relieve pressure since the copper alloy they use it harder than a lead/copper bullet. That's why they have the 3 rings, I believe, to help with pressure. So if you seat the bullet deeper back to around 3.250 it will have a longer free run before it hits the lands and that too can help relieve pressure and the ejector marks might go away. But the thing might not shoot as well, who knows. This is never easy is it. LOL. Plus Weatherbys are supposed to have long throats for long jumps to help relieve pressure already. My understanding is Weatherby did that because they loaded pretty hot to get those legendary Weatherby speeds.

Here's the link to the Barns PDF showing the COL: http://www.barnesbullets.com/files/2014/11/7mmWeatherbyMagnum.pdf

 

[climb-101]

have you tried shooting over a chronograph to see how fast its going. I was fighting ejector marks on one of my guns and I was well below book minimum. When i shot it over the crono, i was all the way up around the max speed which means for what ever reason the pressure was up.

I ended up switching to a slower burning powder plus backing it down a little more. I get a very faint ejector mark now. Unless you look hard you cant find it.

I thought seating the bullet out further as long as its not jammed into the lands helped reduce the pressure since there was more case volume. once its jammed into the lands it increases pressure a lot but i could be wrong on this. How did you find the lands on your gun, you may actually be into the lands, I had the problem when i used on of the hornady gauges.

 

[bigedp51]

If your getting a raised bump from the brass starting to flow into the ejector hole its high pressure. If you are just seeing a ring impression without a raised bump the ejector hole may just have sharp edges. This can can be fixed by stoning the edges of the ejector hole.

Below is brass flow into the ejector and has a raised bump, caused by high chamber pressure and exceeding the elastic limits of the brass. This varies with brass hardness with softer brands of brass showing brass flow sooner than harder brands of brass.

Another thing to check is base expansion just above the extractor groove of the fired cases.

Simple Trick for Monitoring Pressure of Your Rifle Reloads | Hodgdon Reloading

Below a exagerated example of base of the case expanding due to high pressure.

 

[Rich Coyle]

G W Hunter,

You don't have to be concerned about too much jump with Barnes. I would back off from where you are in .040" increments firing five shots each at 100 yards. I prefer 100 yards over longer ranges so there is less influence from the wind. You might be clear back to .200" before you get accuracy. Once you get accuracy you can then go between the best groups you are getting.

 

[GW Hunter]

lol...I've been so focused on not getting too long of a freebore that I didn't notice what was right in front of me regarding Barnes recommended O.A.L. As far as velocities, I was getting 3250 at 72 gr and up to 3385 at 74.5. Barnes 150 gr chart doesn't have 7828 on it so I didn't have any comparable data for the velocity. I will definitely seat the next batch deeper and see what happens...

 

[GW Hunter]

G W Hunter,

You don't have to be concerned about too much jump with Barnes. I would back off from where you are in .040" increments firing five shots each at 100 yards. I prefer 100 yards over longer ranges so there is less influence from the wind. You might be clear back to .200" before you get accuracy. Once you get accuracy you can then go between the best groups you are getting.

That's sounds like my next plan... Thanks

 

[243winxb]

faint ejector marks at 73gr and increasing more visible with each progressive load.

Faint can be seen on some factory ammo.

More is high pressure. After 5 firing or less, the primer pocket may expand and primer fall out. Watch for gas leakage around the primer and bolt face pock marks.

Remember the factory can load shells at maximum PSI, because they are not going to reload it.

 

[CatShooter]

Remember the factory can load shells at maximum PSI, because they are not going to reload it.

No... The factory does NOT load at maximum pressure because they are not going to reload it.

They load at an agreed upon industry standard pressure, that is NOT the maximum pressure that we typically use.

 

[Pdvdh]

Another thing to check is base expansion just above the extractor groove of the fired cases.

Simple Trick for Monitoring Pressure of Your Rifle Reloads | Hodgdon Reloading

Below a exagerated example of base of the case expanding due to high pressure.

Measuring case head expansion is an additional tool in the tool box to monitor pressure. The Hornady techs must have bad eyes, as I've successfully measured case head expansion for decades now with 0.001" calipers. Yet Hornady states 0.0001" calipers are necessary.

They state ~0.0005" measured expansion is an indicator of maximum pressure. I have no troubles reading 0.0003" changes in diameter with quality 0.001" calipers, which is more than sufficient for the associated task. Am not at all motivated to purchase a set of 0.0001" calipers for this use of the calipers.

 

[CatShooter]

Measuring case head expansion is an additional tool in the tool box to monitor pressure. The Hornady techs must have bad eyes, as I've successfully measured case head expansion for decades now with 0.001" calipers. Yet Hornady states 0.0001" calipers are necessary.

They state ~0.0005" measured expansion is an indicator of maximum pressure. I have no troubles reading 0.0003" changes in diameter with quality 0.001" calipers, which is more than sufficient for the associated task. Am not at all motivated to purchase a set of 0.0001" calipers for this use of the calipers.

When the fad of measuring case head expansion with blade micrometers emerged from the swamp of ignorance came to light, I was one of the original Dumb Bunnies that ran out and bought one - a new top quality Starrett (cuz who would be dumb enough to have a used one in stock).

But I quickly learned the folly of my new toy... well not so quickly, cuz it caused me to waste a lot of time and bullets.

The problem is, case heads vary in hardness, A LOT!!!

Lapua, and Lake City cases have heads with a Brinell hardness (scale "B") around 80 to 90 (I measured them)... Remington and Hornady run 45 to 50-ish (I measured them too).

So, a load that is fine in your Lapua, LC, or Norma cases, will squish the heads of Remington and Hornady cases, giving your nifty blade micrometer a heart attack... yet the loads are fine and safe.

The second problem with using case head expansion for a "pressure indication" is that the pressure actually "thumps" the case head with 3,500 to 5,500 pounds (real pounds, not psi) of pressure, so each reloading, increases the hardness of the head.

Anyone wanna buy a nifty new (almost) Starrett 0-1" blade micrometer? Hardly used, in a beautiful case.