Primer flattening question

[Adam S]

Hi all. I have a question that I hope isn't ridiculous. I've handloaded for several years, but have done low pressure rounds like .38 Special and downloaded rifle cartridges to use in older military rifles for target use only. I'm working up a load for my .300 Winchester Magnum and wanted to get opinions from those more experienced than me if my primers look like they're flattening too much.

Here's what I think is pertinent info, though I may be overlooking some things:
1. Rifle is a Sako 85. Primer is CCI Magnum, powder is IMR 4350, bullet is Barnes TSX 180 gr.
2. This is the max load listed in the Barnes manual (69.0 gr)
3. My chrono results are a very consistant 2912 (Barnes manual lists 2978. I know there are lots of factors in max velocity, I'm just listing it for reference.
4. There is no sticking of the bolt or difficulty extracting at all.
5. Recoil seems consistant with other loads.
6. It's a little hard to tell in picture, but there is no cratering of the primer that I can tell.
7. I cannot see any ejector marks on the brass.
8. I MIGHT, just maybe be able to convince myself I see a little of an impression on the primer of tiny machining marks that MAY match the bolt face. It could easily be my imagination.

So my question is, does this amount of primer flattening look concerning? I'm not out for the hottest load or last fps, but this load is averaging 3/4 MOA so I don't want to abandon it if all is ok.

Thanks!

 

[tarbe]

Short answer, no.

Longer answer...primer condition is not a very reliable gauge of pressure!

Case head expansion is much better.

Bolt lift is good...but by the time you get sticky bolt lift, you are probably already past where you should be...and there is no early indicator like with case head expansion.

In a familiar rifle that isn't prone to allowing cratering of primers, a cratered primer definitely gets my attention...as do extractor marks on the headstamp or difficult (even slightly) bolt lift.


Tim

 

[Hogpatrol]

As tarbe posted, flat primers are not a reliable indicator of pressure. Are the primer pockets still tight? Hot loads can make them loose enough to be able to push the primers in with your finger. Cratered primers can also be caused by too much clearance between the firing pin and bolt head.
Not a Sako expert but Remington bolt action rifles are notorious for a sloppy firing pin/bolt head fit.

 

[Clayton]

No expert here, but have a lot of experience working up loads like you're doing. Both @tarbe & @Hogpatrol are correct in their comments. Just from the photo, I can see no signs of excess pressure. Case head expansion is a good first sign to watch for. However it can be misleading sometimes. Once had a .308 Win M700 that had a rather generous chamber. You should keep an eye on case life too. Excessive hot loads will shorten case life. Split necks with only 4 or 5 reloads aren't a good sign.

 

[Ridgewalker]

Measure the case of a fired factory load using the same brass you reload at the web. Then compare it to your handloads after firing. It should be the same if the pressure is close to the same.
I track this on every brand I test and every different handload for my own retired engineer problem.
This and velocity is what I was taught to use as the best indicator.
Still there are always exceptions. Its good that you are checking these things.
I have found that Federal nickel plated brass after even one factory firing can have loose primer pockets. Just one of my personal findings although they should be made to the same brass composition and dimensions as everyone else’s.

 

[greyfox]

Nope, No concern. Primer's not "bulging" and extraction is not noticeable, It's just more pressure pushing back on the bolt face and a hole for pressure to increase (Bernelli's Principle). BTW, my 180 gr load is 1 grain over yours, no issues what so ever,

 

[Hogpatrol]

For those more technically inclined, the program Quick Load can calculate approximate pressure levels with a given load. I use it for my wildcat cartridges.
An FYI, reloading manuals, bullet manufacturer and powder companies' recommendations can be on the conservative side.

 

[Ridgewalker]

An FYI, reloading manuals, bullet manufacturer and powder companies' recommendations can be on the conservative side.

Yes, I have some manuals from the 1950s and 1960s that are not nearly so conservative. But today we are in a time of litigating hang nails, so they have to be conservative.

 

[tarbe]

I hope the careful reader has noticed a pattern here.

Whether using primer condition, case head expansion, or bolt lift, the handloader needs to be considering these indicators in relation to known reference points in this rifle.

One data point taken in isolation can be misleading.

 

[Ridgewalker]

I hope the careful reader has noticed a pattern here.

Whether using primer condition, case head expansion, or bolt lift, the handloader needs to be considering these indicators in relation to known reference points in this rifle.

One data point taken in isolation can be misleading.

Good point tarbe!

 

[Hogpatrol]

Another factor to look at is velocity. Flat or cratered primers along with higher than normal velocities could indicate excessive pressure.

 

[Dr Ray]

Hi all. I have a question that I hope isn't ridiculous. I've handloaded for several years, but have done low pressure rounds like .38 Special and downloaded rifle cartridges to use in older military rifles for target use only. I'm working up a load for my .300 Winchester Magnum and wanted to get opinions from those more experienced than me if my primers look like they're flattening too much.

Here's what I think is pertinent info, though I may be overlooking some things:
1. Rifle is a Sako 85. Primer is CCI Magnum, powder is IMR 4350, bullet is Barnes TSX 180 gr.
2. This is the max load listed in the Barnes manual (69.0 gr)
3. My chrono results are a very consistant 2912 (Barnes manual lists 2978. I know there are lots of factors in max velocity, I'm just listing it for reference.
4. There is no sticking of the bolt or difficulty extracting at all.
5. Recoil seems consistant with other loads.
6. It's a little hard to tell in picture, but there is no cratering of the primer that I can tell.
7. I cannot see any ejector marks on the brass.
8. I MIGHT, just maybe be able to convince myself I see a little of an impression on the primer of tiny machining marks that MAY match the bolt face. It could easily be my imagination.

So my question is, does this amount of primer flattening look concerning? I'm not out for the hottest load or last fps, but this load is averaging 3/4 MOA so I don't want to abandon it if all is ok.

Thanks!

primer

• Adam S
• Jun 11, 2018
• 1

Drop one grain and see what the result is. I usually find that max loads rarely shoot consistently and usually but not always to start open up the groups,
Suggest the Winchester primers if that doesn’t work.
A slight drop in velocity won’t make any practical difference. I personally prefer to have a very accurate load rather than top velocity.
That way I develop great confidence.

 

[ChrisG]

Primers are the most obvious place most people look when determining load pressure, They are also the absolute least reliable. Ejector slot signs in the brass, case head overexpansion and sticking bolts are a more reliable sign when taken with Chrono data. sometimes a cratered primer is a cratered primer and high pressure, sometimes it is just an oversized firing pin hole and a soft lot of primers. The only sure sign of overpressure in a primer is something like this:

This is an example of much too high pressure but is also evidenced by the case head bulge, the cratering in the primer as well as bolt face machine marks imprinted and the semi-circular ejector hole print in the head of the case on the right just above the "22-" in 22-250. Check the other things before you start deciding that your pressure is too high. In my experience, most of the time but not always, the rest of the case will start showing signs of excessive pressure before the primer does. I have had ejector prints in my case head and a fairly normal looking primer. I have had primers mashed so that they just had the tiniest little fillet edge around them and no other signs. I still back off a bit, not because I need to but because I don't like to beat my equipment harder than I need to. Usually, the high pressure loads don't produce correspondingly awesome ballistics, so I don't worry about dropping it down. A 140 grain 6.5mm bullet a 2,550 fps is fine with me and it definitely doesn't bounce off of the whitetail deer and black bear that proliferate around where I live.

The only sure way to know your pressure is to invest in a strain gauge setup which is a few hundred dollars and takes all the guess work out of it.

 

[Adam S]

Thanks to all of you for the insightful comments. I appreciate the input.

I know only looking at primers is only part of the equation, but ​

I read all the warnings in my reloading manuals and want to make sure I'm being (probably over-) cautious.

Several of you mentioned using chronograph info as a warning when you're getting close to the edge. What exactly are you looking for? I'm finding a fairly consistent 35-40 fps increase for 1 grain increase in powder for this load.

Unfortunately, I carelessly deprimed the cases of the load with 1 grain less before I noticed the primers. I will load a few more of those for comparison, but it's good to know it doesn't look like I'm doing anything too dangerous with these loads.

 

[Adam S]

Measure the case of a fired factory load using the same brass you reload at the web. Then compare it to your handloads after firing. It should be the same if the pressure is close to the same.
I track this on every brand I test and every different handload for my own retired engineer problem.
This and velocity is what I was taught to use as the best indicator.
Still there are always exceptions. Its good that you are checking these things.
I have found that Federal nickel plated brass after even one factory firing can have loose primer pockets. Just one of my personal findings although they should be made to the same brass composition and dimensions as everyone else’s.

Just so I understand, are you measuring the outside diameter of the case right above the belt?

The primers are not loose at all, thankfully.

 

[WAB]

Yes, I have some manuals from the 1950s and 1960s that are not nearly so conservative. But today we are in a time of litigating hang nails, so they have to be conservative.

Hang on to those old manuals. The new ones and the online loads are a waste of time, written by lawyers! I use a tattered old Lyman manual. Pure gold. I’ve been reloading for 40+ years and it has never gotten me in trouble. Odd flattening on those primers but if all else checks out I’d stick with the load.

 

[PHOENIX PHIL]

Hang on to those old manuals. The new ones and the online loads are a waste of time, written by lawyers! I use a tattered old Lyman manual. Pure gold. I’ve been reloading for 40+ years and it has never gotten me in trouble. Odd flattening on those primers but if all else checks out I’d stick with the load.

Need to be careful with those old manuals. The recipes for the various powders change over time and with those changes the max loads change too.

 

[PHOENIX PHIL]

Thanks to all of you for the insightful comments. I appreciate the input.

I know only looking at primers is only part of the equation, but ​

I read all the warnings in my reloading manuals and want to make sure I'm being (probably over-) cautious.

Several of you mentioned using chronograph info as a warning when you're getting close to the edge. What exactly are you looking for? I'm finding a fairly consistent 35-40 fps increase for 1 grain increase in powder for this load.

Unfortunately, I carelessly deprimed the cases of the load with 1 grain less before I noticed the primers. I will load a few more of those for comparison, but it's good to know it doesn't look like I'm doing anything too dangerous with these loads.

Not sure what others have observed. But I have seen where suddenly an increased load did not result in increased velocity and even on occasion where it dropped. Go to next load up and you get a bigger spike in velocity than you expect. Not sure how this happens, but this also about the time such things as ejector marks on the head show up and/or sticky bolts.

 

[MAdcox]

I have found that Federal nickel plated brass after even one factory firing can have loose primer pockets. Just one of my personal findings although they should be made to the same brass composition and dimensions as everyone else’s.

Had the same issue. Bought 3 boxes of Federal Premium Trophy Copper for my 300wsm for practice of the sticks and because I needed some more brass to reload. The first box I tried to reload the primers were just falling out of the case. Measured all 60 pieces of once fired brass and almost all of the primer pockets were out of spec. Had to chunk it all and buy new brass. Will not be using Federal stuff anymore.

 

[Ridgewalker]

Just so I understand, are you measuring the outside diameter of the case right above the belt?

Yes. My micrometer sits right against the belt on the “web” I believe they call it. I have machined cases down to the belt and you can see how it is thinning out after a number of reloads. Eventually if you full length resize, it can separate there. In my experience you will have to anneal the neck at least once or it will split before it separates at the web.