Would You Keep Going?

[RabbitSlayer]

Loaded up a pressure test for 223AI, Starline 556, Remington 7.5, N133. I didn't think I would even fire them all, but the only pressure sign at all is primer cratering. Primer is not flattened at all. I see no marks on the brass and bolt lift was just fine. The first cratering started .5 gr before this.

I shoot the same components in my regular 223 and book max has about the same cratering. Id normally back off a little and call it good at this point, but maybe I am just a wuss lol.

I don't think I will blow my face off, but I dont want to prematurely ruin my brass.

Would you keep going?

 

[Paul Hilgedick]

Looks to me like bushing the firing pin hole would be in order.

Paul Hilgedick

 

[RabbitSlayer]

Looks to me like bushing the firing pin hole would be in order.

Paul Hilgedick

I considered that too. Both my tikka in 223 do it. My Tikka in 6 creed the primers can be flat as a pancake and no cratering.

 

[SD guy]

Ok, we are working with an AI cartridge. Op is likely striving for max velocity with an AI cartridge. Yet he ask what we would do. We are a varied crowd so the answers will vary as well

. I would start off with a few questions. What is action? How much is the shoulder pushed back. how is your accuracy.

You seem concerned about achieving a long brass life. I would concur. Do not know which primer you are working with. Some primer cups are thicker than others. Seems the bolt / firing pin have ample clearance.

So would keep going? Probably would continue another 9 tenths of a grain down as well as up in 3 tenths increments & see what the paper and chronograph has to say along with pressure signs. Accuracy holds more value to me than velocity. Sometimes we get both. Sometimes we settle for great accuracy & super brass life.

 

[Fast14riot]

Firing pin hole is too large, but I don't see any pressure signs yet. I shoot 7.5's in many and they'll flatten out when pressure starts getting high.

 

[RabbitSlayer]

Ok, we are working with an AI cartridge. Op is likely striving for max velocity with an AI cartridge. Yet he ask what we would do. We are a varied crowd so the answers will vary as well

. I would start off with a few questions. What is action? How much is the shoulder pushed back. how is your accuracy.

You seem concerned about achieving a long brass life. I would concur. Do not know which primer you are working with. Some primer cups are thicker than others. Seems the bolt / firing pin have ample clearance.

So would keep going? Probably would continue another 9 tenths of a grain down as well as up in 3 tenths increments & see what the paper and chronograph has to say along with pressure signs. Accuracy holds more value to me than velocity. Sometimes we get both. Sometimes we settle for great accuracy & super brass life.

Its a tikka action. Its rem 7.5. I'm not pushing for max velocity. I know im close. Powder is up to the base of the neck. I just want to decide where pressure is and never get close to that again. Cratering is a sign of pressure. This is a little more than I have seen before, but even some factory ammo craters and flattens primers in various guns I own. Accuracy testing is the next step. Heck gonna be hard to beat the random fireforming load.

Im trying to get better at looking at pressure. I didn't give the full details, cuz I want to know what you see. Im positive a bunch of people here have kept on going till they are smacking the bolt open with a hammer and popping primers, and they have done it multiple times. I haven't been loading that long, so I am always on the side of caution.

 

[jpjulian]

You might consider measuring case head expansion ahead of the extractor groove. 5.56 brass "should" be harder than .223 brass as it is meant for higher pressures. I have read that expansion greater than 0.0005" is an indicator of high pressure when measured from a new, not a once fired, case. This measurement on new Winchester .223 cases showed 0.003-4", (IIRC), along with a mild ejector mark, from my AR Highpower loads. Winchester .223 cases "may" be softer. Case head expansion is somewhat controversial but absent indicators other than cratered primers might be something to look at.

 

[JSH]

If you flatten a Remington 71/2, you have a lot of pressure.

Bushing a firing pin so it doesn’t crater doesn’t take away the pressure, it just hides it. Yes there are exceptions to that. Measuring pin and hole will answer questions. Another thing is firing pin protrusion.
I had an issue with 204 a few years ago. My buddy and I did some measuring when I started popping primers (Savage, let the hate begin). I came home and measured the rest of them and all were excessive. Readjusted and no more issues.
I have considered bushing firing pins for accuracy, I came to the conclusion I have not really out done how they came from the factory.

There are some good AI cartridges that there is some gain to, and there are some that go backwards, 30-06AI comes to mind.
Blowing a primer and having smoke and gas come out of places other than the muzzle is unnerving to say the least.

 

[RabbitSlayer]

You might consider measuring case head expansion ahead of the extractor groove. 5.56 brass "should" be harder than .223 brass as it is meant for higher pressures. I have read that expansion greater than 0.0005" is an indicator of high pressure when measured from a new, not a once fired, case. This measurement on new Winchester .223 cases showed 0.003-4", (IIRC), along with a mild ejector mark, from my AR Highpower loads. Winchester .223 cases "may" be softer. Case head expansion is somewhat controversial but absent indicators other than cratered primers might be something to look at.

Hmmm i think i have some virgin cases from this lot that I culled cuz they were way heavier. I for sure have 250 new from a different lot. I'll try that in the morning.

 

[precision1]

I don't have a gun that craters primers at all and keeps round primer edges like that.strange for me

I shoot rebarrelled surplus Mausers and all....

Did you use a few reloading manuals to see if your velocity and max was adding up to a smart velocity for max and using a chronograph?

Those manuals will tell you what pressure they hit velocity at
Bullet seating depths affect this

I only use cci and federal primers

 

[RabbitSlayer]

I don't have a gun that craters primers at all and keeps round primer edges like that.strange for me

I shoot rebarrelled surplus Mausers and all....

Did you use a few reloading manuals to see if your velocity and max was adding up to a smart velocity for max and using a chronograph?

Those manuals will tell you what pressure they hit velocity at
Bullet seating depths affect this

I only use cci and federal primers

The bullet and powder are published by VV. 223 AI as I understand should be 1.5 to 2 gr more. Velocity was what I expected roughly. Im at Tikka mag length.

 

[Tangent]

I'd keep an eye on the velocity, if it's well above expected or spikes as you increase charge that can tell you a lot. I'm fairly cautious, so once I start seeing primer changes or extractor marks I back off a little. Are you getting any case head expansion? Good brass life and top end loads don't go hand in hand and the most accurate loads are often not the fastest.

 

[Doom]

The pressure signs we look for are all associated with potential failure of a specific component (primer or case) or an indication that the pressure is excessive (beyond the SAAMI limit such as bolt lift). In this case the primer cratering is a function of the clearance between the firing pin and the bolt. Without knowing what that clearance is it can only be assumed that the primer is/may be the limiting factor. The cratering is not only a function of the firing pin clearance but also the shape of the bolt hole in/on the face of the bolt.

The key to evaluating this issue is to look at what is happening at low starting loads. Does the primer show cratering? It may or may not. If it does then the key is to watch for how the cratering changes as the load increases. If it doesn't then the key is begin to watch for cratering as the load increases and then when it begins to watch it.

The degree to which cratering is an issue is also related to the amount of firing pin protrusion. Excessive protrusion increases the likelihood of blanking the primer as the material is thinned due to the cratering.

In the case of the primer shown, I can tell you my Remington 700 308 shows more cratering at minimum loads than this primer shows. But increasing the load does not show an increase in cratering to beyond book maximum. I have never blanked a primer. If you increase the load beyond this point if the cratering increase then you know you are moving closer to the point that the primer will fail. Unfortunately that is about all you really know and it is a judgment call as to where to stop.

 

[Webster]

Loaded up a pressure test for 223AI, Starline 556, Remington 7.5, N133. I didn't think I would even fire them all, but the only pressure sign at all is primer cratering. Primer is not flattened at all. I see no marks on the brass and bolt lift was just fine. The first cratering started .5 gr before this.

I shoot the same components in my regular 223 and book max has about the same cratering. Id normally back off a little and call it good at this point, but maybe I am just a wuss lol.

I don't think I will blow my face off, but I dont want to prematurely ruin my brass.

Would you keep going?
View attachment 1641790
View attachment 1641791

Why is your goal to see how much powder you can stuff in a case without creating problems. I reload for accuracy at decent FPS.

 

[fkimble@charter.net]

As already mentioned, the cratering is most likely due to excessive bolt face hole size versus small firing pin size. The primer is well rounded. Get your bolt face redone and the cratering will go away. Do a search for bolt face bushing on here, there are several respected smiths doing this.

Frank

 

[K22]

Hard bolt lift and / or ejector marks on the case head are almost always signs of high pressure. Primer appearance is the least reliable indicator in my experience especially when this is the only condition observed.

The one technically correct method to access excessive pressure is measuring case head expansion but this is beyond the capability of the average reloader in the sense that obtaining accurate information requires knowledge, special equipment and a skilled operator to obtain reliable data. Speer has extensive information on this issue which is too extensive to repeat here.

Often excessive pressure will reveal itself in loose primer pockets but one does not want to wait until that is observed. At the first sign of excessive pressure, one needs to back off.

There is no such thing as a "wuss" when it comes to concern over excessive pressure.

 

[bozo699]

Looks to me like bushing the firing pin hole would be in order.

Paul Hilgedick

^^^^^^^^
Wayne

 

[bozo699]

You might consider measuring case head expansion ahead of the extractor groove. 5.56 brass "should" be harder than .223 brass as it is meant for higher pressures. I have read that expansion greater than 0.0005" is an indicator of high pressure when measured from a new, not a once fired, case. This measurement on new Winchester .223 cases showed 0.003-4", (IIRC), along with a mild ejector mark, from my AR Highpower loads. Winchester .223 cases "may" be softer. Case head expansion is somewhat controversial but absent indicators other than cratered primers might be something to look at.

This is 100% the correct way to check for pressure.
Wayne

 

[Ackman]

Loaded up a pressure test for 223AI, Starline 556, Remington 7.5, N133. I didn't think I would even fire them all, but the only pressure sign at all is primer cratering. Primer is not flattened at all. I see no marks on the brass and bolt lift was just fine. The first cratering started .5 gr before this.

I shoot the same components in my regular 223 and book max has about the same cratering. Id normally back off a little and call it good at this point, but maybe I am just a wuss lol.

I don't think I will blow my face off, but I dont want to prematurely ruin my brass.

Would you keep going?
View attachment 1641790
View attachment 1641791

That's not an overpressure sign. It's a sign that the firing pin hole is a little bit too large for the firing pin. Having a tighter fitting bushing installed will cure that. And no, that's not gonna blow your face off or ruin your brass.

 

[STS]

Why is your goal to see how much powder you can stuff in a case without creating problems. I reload for accuracy at decent FPS.

^^^^^ It took 13 responses, but someone finally came up with the correct solution. It doesn't make any difference if you squeeze another 50 fps out of it. The additional velocity that can be had over and above what is already demonstrated on your cases, would be near impossible to detect in the field. I have a .223 AI, and fireform loads are about 200 fps less than the improved loads, and I can't tell the difference on the target, or in a dog town, out to at least 200 yards. Further out you can see the difference but not at 200. So another few fps is not worth much. If you want it just for the he!! of it, then go for it. The only thing that matters is how does is shoot, and is it in tune.