Primer pocket truing

[Coyote Shadow Tracker]

Having shot F-Class for many years, drilling certain brands of brass with an incorrectly sized bit will ruin the accuracy of said case.
Lapua and Norma both use CIP sized flash holes that are smaller than US sized flash holes. When I started using Norma brass, I was de-burring flash holes with a Brownell's tool, it was enlarging the flash hole… another shooter pointed out the difference and I bought the cutter for the smaller flash hole and my groups at 600 shrunk considerably.
So, my take on drilling flash holes is don't do it unless you SEE that it improves something.

Cheers.

They sell different size Prime Flash Hole Uniformers. Lapua Claims that their cases are already debured and don't need deburing. LAPUA also has a different size flash hole then other manufactures - so if you are going to uniform your Flash Holes make sure you use the correct tool.

• .062 for Lapua 1.5mm flash holes
• .080 for "standard" flash holes

The brass case is very important and sometimes important details are overlooked–such as the Primer Pocket and Flash Hole inside of the case.

In cartridge manufacturing, the flash hole is "punched" into the brass. While this is the least expensive method, it has many shortcomings and inconsistencies. The flash holes, therefore, are of different sizes and shapes. The most detrimental to accuracy are the irregular "breakouts" and "burrs" on the inside. This will cause "shot-to-shot" differences in Primer "Flame Fronts", causing inconsistent pressure/velocity and, thereby, loss of accuracy. Bench Rest Shooters have been uniforming flash holes since 1969.
The main reason for Flash Hole uniformity, Primer Pocket Uniformity, Primer Seating Depth is to get PROPER & CONSISTANT Flash Burn.
Naturally you need to use the correct tools when preforming these modifications.

With the Precision K & M UNIFORMER tools, you can realize the potential accuracy by simultaneously reaming, de-burring and chamfering the inside of the flash hole. The unique features of the K & M Tools provide uniformity with a pre-set depth stop, (Gage), surrounding the tool steel cutter, therefore, does not require the case to be trimmed to a precise or consistent length. Operation is controlled in reference to inside-bottom of case, not case mouth.

I am not telling anyone to do any Brass Prep if they choose not to.
Remember if you do anything incorrectly in reloading you probably won't get good results.

I do Brass Prep to all my cases because I like the groups I shoot.

 

[misterc01]

They sell different size Prime Flash Hole Uniformers. Lapua Claims that their cases are already debured and don't need deburing. LAPUA also has a different size flash hole then other manufactures - so if you are going to uniform your Flash Holes make sure you use the correct tool.

• .062 for Lapua 1.5mm flash holes
• .080 for "standard" flash holes

The brass case is very important and sometimes important details are overlooked–such as the Primer Pocket and Flash Hole inside of the case.

In cartridge manufacturing, the flash hole is "punched" into the brass. While this is the least expensive method, it has many shortcomings and inconsistencies. The flash holes, therefore, are of different sizes and shapes. The most detrimental to accuracy are the irregular "breakouts" and "burrs" on the inside. This will cause "shot-to-shot" differences in Primer "Flame Fronts", causing inconsistent pressure/velocity and, thereby, loss of accuracy. Bench Rest Shooters have been uniforming flash holes since 1969.
The main reason for Flash Hole uniformity, Primer Pocket Uniformity, Primer Seating Depth is to get PROPER & CONSISTANT Flash Burn.
Naturally you need to use the correct tools when preforming these modifications.

With the Precision K & M UNIFORMER tools, you can realize the potential accuracy by simultaneously reaming, de-burring and chamfering the inside of the flash hole. The unique features of the K & M Tools provide uniformity with a pre-set depth stop, (Gage), surrounding the tool steel cutter, therefore, does not require the case to be trimmed to a precise or consistent length. Operation is controlled in reference to inside-bottom of case, not case mouth.

I am not telling anyone to do any Brass Prep if they choose not to.
Remember if you do anything incorrectly in reloading you probably won't get good results.

I do Brass Prep to all my cases because I like the groups I shoot.

Good infof - THX!

 

[Alex Wheeler]

I have been involved in flash hole testing. I had some brass made with no hole so I could drill and ream them to size. I have tested uniforming and deburing. I have tested seating to depth vs feel. Its what we do for 1000yd BR. There is only one game out there that measures groups. Its BR. Period. My current process, after testing everything I can is to not touch the primer pocket or flash hole, and seat by feel. Many records on the books will back this up, no BS claims on the internet. Facts recoded by official match reports and current world records. Do not over think this for a hunting application. There are far more important parts of the tune.

 

[orkan]

Once upon a time, every "world record" in shooting was set with a musket. lol

Doing things the way they've always been done, and then expecting change?

This is all advancing, no matter what anyone thinks. No one is going to stop it. Just like every other time advancements have arrived, people are always there advocating the previous ways of doing things. Those that adopt the new equipment and new ways, continue to improve, regardless of what others think or say. That's how it's always gone, and that's how it will continue to go. Those that don't adapt, are left behind.

The CPS & PrimeWhere along with primer seating depth testing methodology I've pioneered controls this variable as fully as is currently possible.

If you can seat bullets to +/- .001, then you should. If you can hold headspace to +/- .0005, then you should. If you can dump powder to +/- 1 kernel, then you should. If you can seat primers to +/- .001, then you should. Equipment is available that will let us do all of that, with no additional time spent than we would be spending already.

Just yesterday I talked to a gentleman that had 2 failure to fire in his match gun previously, and upon receiving his PrimeWhere gauge, discovered over 8 thousandths of primer seating depth variance in what remained of that firing. He was seating by feel, but he had some very tight pocket to primer fitment, and the force to insert the primer, masked the ability to "feel" where to stop correctly. This has come up countless times. He seated the same batch of components on his next firing with the CPS which he setup using the PrimeWhere Digital, and after priming and measuring 350 pieces of 6BRA found an extreme spread of 1.6 thousandths and a SD of .0003. (best report I've received yet) So the average variance of his seated primers went from over 5 thousandths, to less than half of a thousandth.

The forward thinking, always advocate for better, rather than settling with worse.

To those reading this, just ask yourself if this passes a logic check. Which sounds right to you?

Leave variables uncontrolled on purpose?
Or control and uniform every variable you can?

Firing pin travel distance must be uniform... but the location of the primer that determines how far the firing pin travels before it hits something, doesn't?

Would you run a cocking piece that varied where it locks up on the sear by 5 thousandths randomly between shots?

Sounds silly when you say it out loud doesn't it? Anyone that can think logically, knows you don't want variable force or distance (which translates to force) in your ignition system.

I wonder how many here know that when you push the primer in deeper, velocity generally increases?

Primer pocket and flash hole uniforming fall into a different category, not because we don't want to control those variables... but because we currently do not have adequate tooling to improve upon what the factor offers, most of the time. In the worst brass, we can improve upon it... however if you attempt to "uniform" Alpha or Lapua cases (or any quality manufacturer)... you are likely to INCREASE variance. Not just in the mechanical measurements, but in the surface finish... specifically of the wall of the primer pocket, which will absolutely lead to a friction differential uniformity problem - which will translate directly to a primer seating depth and deformation variance. If we COULD improve upon the brass dimensionally without negatively affecting the interface, then I would be an advocate of that. Yet I've not found such a piece of equipment yet, outside of a very expensive CNC turning center.

I know there are those out there that are looking to genuinely improve. I'm telling you in no uncertain terms, if you control your primer seating depth uniformity to the degree I describe above, you'll experience an improvement in your shooting. If you don't understand the premise, the process, or why it will make a difference, just give me a call and I'll explain it in as detailed a way as I can.


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[Muddyboots]

Reloaders/shooters are by far the most detailed or not detailed group depending upon which side of the bed you got out of that morning.

I like eliminating "potential" (another 10 page discussion on potential) "variances" (another 10 pages) in my reloading process.

So what does that mean? I perform certain steps on my brass that "I believe" can introduce a variance to my loaded round.

What are those steps? None of your business.

Back to my 4 fingers of Jim Beam. Ok, why 4 and not 3? I have big fingers is why.

 

[K.E.C. Darkside]

I do debur the flash hole and do a quick pocket true on all my brass new or old. More to make sure I don't miss something than to do much other than a basic cleaning. It also provides consistency with my process. In the end, I find that consistency is what allows for the best ammunition output.

I do debur the flash hole and do a quick pocket true on all my brass new or old. More to make sure I don't miss something than to do much other than a basic cleaning. It also provides consistency with my process. In the end, I find that consistency is what allows for the best ammunition output.

Howdy, what he said. I stay to my routine, no worries.

 

[Sending156s]

I've been reloading for more than 60 years. Shot 1000 yard completion for years, won inbs/nbsra national championship for score and two state 1000 yard championships. I'm also a avid long range hunter.

While I de-burr the flash hole, I very rarely true the primer pocket for depth and being square. What I'd like is some input on how many think it is worth the time and effort to true the primer pocket.

I uniform non Lapua brass. It's one time in life of brass. Most brass have a radius at the bottom which hinders seating primers flat. Does it help? A definite yes since it makes me feel better & boosts my confidence in my ammo.
Best wishes!

 

[SWHandldr]

I uniform my LC 5.56 brass on my Lyman case prep center. Minimum effect on pocket walls & best I measure, consistent depth +/- .002.
Frakford Arsenal hand primer, set with a feeler guage, yields .004 below flush.

My 18" 1:8 HB Frankenrifle shoots 60 gr VMaxes into 2 MOA at 200 yds with this brass, CCI 4OO's (cple thousand still on hand from a LGS closing looong ago) & WC852(fast).

Cost effective plinking & varmint medicine for my retired budget.

 

[Alex Wheeler]

Once upon a time, every "world record" in shooting was set with a musket. lol

Doing things the way they've always been done, and then expecting change?

This is all advancing, no matter what anyone thinks. No one is going to stop it. Just like every other time advancements have arrived, people are always there advocating the previous ways of doing things. Those that adopt the new equipment and new ways, continue to improve, regardless of what others think or say. That's how it's always gone, and that's how it will continue to go. Those that don't adapt, are left behind.

The CPS & PrimeWhere along with primer seating depth testing methodology I've pioneered controls this variable as fully as is currently possible.

If you can seat bullets to +/- .001, then you should. If you can hold headspace to +/- .0005, then you should. If you can dump powder to +/- 1 kernel, then you should. If you can seat primers to +/- .001, then you should. Equipment is available that will let us do all of that, with no additional time spent than we would be spending already.

Just yesterday I talked to a gentleman that had 2 failure to fire in his match gun previously, and upon receiving his PrimeWhere gauge, discovered over 8 thousandths of primer seating depth variance in what remained of that firing. He was seating by feel, but he had some very tight pocket to primer fitment, and the force to insert the primer, masked the ability to "feel" where to stop correctly. This has come up countless times. He seated the same batch of components on his next firing with the CPS which he setup using the PrimeWhere Digital, and after priming and measuring 350 pieces of 6BRA found an extreme spread of 1.6 thousandths and a SD of .0003. (best report I've received yet) So the average variance of his seated primers went from over 5 thousandths, to less than half of a thousandth.

The forward thinking, always advocate for better, rather than settling with worse.

To those reading this, just ask yourself if this passes a logic check. Which sounds right to you?

Leave variables uncontrolled on purpose?
Or control and uniform every variable you can?

Firing pin travel distance must be uniform... but the location of the primer that determines how far the firing pin travels before it hits something, doesn't?

Would you run a cocking piece that varied where it locks up on the sear by 5 thousandths randomly between shots?

Sounds silly when you say it out loud doesn't it? Anyone that can think logically, knows you don't want variable force or distance (which translates to force) in your ignition system.

I wonder how many here know that when you push the primer in deeper, velocity generally increases?

Primer pocket and flash hole uniforming fall into a different category, not because we don't want to control those variables... but because we currently do not have adequate tooling to improve upon what the factor offers, most of the time. In the worst brass, we can improve upon it... however if you attempt to "uniform" Alpha or Lapua cases (or any quality manufacturer)... you are likely to INCREASE variance. Not just in the mechanical measurements, but in the surface finish... specifically of the wall of the primer pocket, which will absolutely lead to a friction differential uniformity problem - which will translate directly to a primer seating depth and deformation variance. If we COULD improve upon the brass dimensionally without negatively affecting the interface, then I would be an advocate of that. Yet I've not found such a piece of equipment yet, outside of a very expensive CNC turning center.

I know there are those out there that are looking to genuinely improve. I'm telling you in no uncertain terms, if you control your primer seating depth uniformity to the degree I describe above, you'll experience an improvement in your shooting. If you don't understand the premise, the process, or why it will make a difference, just give me a call and I'll explain it in as detailed a way as I can.


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Forward thinking test everything on the target and go with what shoots smallest. I have been involved with testing and development with a lot of rifle components, especially ignition. The records continue to fall every year because of advances in equipment and tuning knowledge. Some guys go to extremes at the loading bench to make the ammo as perfect as they can because they can. One of my customers spins his case with an indicator on the primer to make sure its seated square. Guys dont post about it but youd be surprised at how far some go with regards not just primer sorting and seating but all aspects of the load. I have done my own testing and I can make them shoot in the 1"s at 1k without doing that. In fact, at Deep Creek last march I shot a 1.6 and backed it up with a 1.5 at 1k with the worst lot of 205s I have seen .008 height variation. I did not sort them, just seated. Didnt even clean the carbon out of the primer pockets. This is the kind of accuracy we are seeking, we didn't get here by not testing everything you can think of. Now, I'm not advocating that guys should not try different tools or methods, but most of the time shooters focus on the gadgets and tools when the real problem is they dont have a good load development process.

 

[Sending156s]

Once upon a time, every "world record" in shooting was set with a musket. lol

Doing things the way they've always been done, and then expecting change?

This is all advancing, no matter what anyone thinks. No one is going to stop it. Just like every other time advancements have arrived, people are always there advocating the previous ways of doing things. Those that adopt the new equipment and new ways, continue to improve, regardless of what others think or say. That's how it's always gone, and that's how it will continue to go. Those that don't adapt, are left behind.

The CPS & PrimeWhere along with primer seating depth testing methodology I've pioneered controls this variable as fully as is currently possible.

If you can seat bullets to +/- .001, then you should. If you can hold headspace to +/- .0005, then you should. If you can dump powder to +/- 1 kernel, then you should. If you can seat primers to +/- .001, then you should. Equipment is available that will let us do all of that, with no additional time spent than we would be spending already.

Just yesterday I talked to a gentleman that had 2 failure to fire in his match gun previously, and upon receiving his PrimeWhere gauge, discovered over 8 thousandths of primer seating depth variance in what remained of that firing. He was seating by feel, but he had some very tight pocket to primer fitment, and the force to insert the primer, masked the ability to "feel" where to stop correctly. This has come up countless times. He seated the same batch of components on his next firing with the CPS which he setup using the PrimeWhere Digital, and after priming and measuring 350 pieces of 6BRA found an extreme spread of 1.6 thousandths and a SD of .0003. (best report I've received yet) So the average variance of his seated primers went from over 5 thousandths, to less than half of a thousandth.

The forward thinking, always advocate for better, rather than settling with worse.

To those reading this, just ask yourself if this passes a logic check. Which sounds right to you?

Leave variables uncontrolled on purpose?
Or control and uniform every variable you can?

Firing pin travel distance must be uniform... but the location of the primer that determines how far the firing pin travels before it hits something, doesn't?

Would you run a cocking piece that varied where it locks up on the sear by 5 thousandths randomly between shots?

Sounds silly when you say it out loud doesn't it? Anyone that can think logically, knows you don't want variable force or distance (which translates to force) in your ignition system.

I wonder how many here know that when you push the primer in deeper, velocity generally increases?

Primer pocket and flash hole uniforming fall into a different category, not because we don't want to control those variables... but because we currently do not have adequate tooling to improve upon what the factor offers, most of the time. In the worst brass, we can improve upon it... however if you attempt to "uniform" Alpha or Lapua cases (or any quality manufacturer)... you are likely to INCREASE variance. Not just in the mechanical measurements, but in the surface finish... specifically of the wall of the primer pocket, which will absolutely lead to a friction differential uniformity problem - which will translate directly to a primer seating depth and deformation variance. If we COULD improve upon the brass dimensionally without negatively affecting the interface, then I would be an advocate of that. Yet I've not found such a piece of equipment yet, outside of a very expensive CNC turning center.

I know there are those out there that are looking to genuinely improve. I'm telling you in no uncertain terms, if you control your primer seating depth uniformity to the degree I describe above, you'll experience an improvement in your shooting. If you don't understand the premise, the process, or why it will make a difference, just give me a call and I'll explain it in as detailed a way as I can.


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Nice write up & contribution Gregg. I guess I do what you suggested. I stated i don't do Lapua. That also includes Alpha. Alpha does have a severe radius at the bottom of the bottom of their primer pocket, but the head material is so hard it binds the tool on a high percentage of attempts, so I've stopped it on Alpha also. On the brass I do uniform, ex; Hornady, I seat with a 21st century hand primer. It's controlled to .001 per click. I'm old & my hands are starting to hurt. It won't be long before I transition to the CPS. It's a good contribution to the accessories available to reloaders to make the task easier & more precise.

 

[Sending156s]

Forward thinking test everything on the target and go with what shoots smallest. I have been involved with testing and development with a lot of rifle components, especially ignition. The records continue to fall every year because of advances in equipment and tuning knowledge. Some guys go to extremes at the loading bench to make the ammo as perfect as they can because they can. One of my customers spins his case with an indicator on the primer to make sure its seated square. Guys dont post about it but youd be surprised at how far some go with regards not just primer sorting and seating but all aspects of the load. I have done my own testing and I can make them shoot in the 1"s at 1k without doing that. In fact, at Deep Creek last march I shot a 1.6 and backed it up with a 1.5 at 1k with the worst lot of 205s I have seen .008 height variation. I did not sort them, just seated. Didnt even clean the carbon out of the primer pockets. This is the kind of accuracy we are seeking, we didn't get here by not testing everything you can think of. Now, I'm not advocating that guys should not try different tools or methods, but most of the time shooters focus on the gadgets and tools when the real problem is they dont have a good load development process.

Alex, thanks for a brief glance at what goes on in competition. Would you share the cartridge you were shooting at 1K?
I believe I have a streamlined reloading process addressing the variables that do affect performance, but would like to compare it to yours. It sure would be nice to see your process. I would look to see if there's something I could take away from it. Thanks…hope you get to enjoy a beautiful fall day!

 

[RockyMtnUT]

I have been involved in flash hole testing. I had some brass made with no hole so I could drill and ream them to size. I have tested uniforming and deburing. I have tested seating to depth vs feel. Its what we do for 1000yd BR. There is only one game out there that measures groups. Its BR. Period. My current process, after testing everything I can is to not touch the primer pocket or flash hole, and seat by feel. Many records on the books will back this up, no BS claims on the internet. Facts recoded by official match reports and current world records. Do not over think this for a hunting application. There are far more important parts of the tune.

Amen. This is the truth. Not that "pest control"truth.
The last line is spot on.

 

[Alex Wheeler]

It was a 6BRA. But I shoot more hunting rifles and elr stuff than BR. My process is exactly the same for any cartridge I load for. It's pretty basic. Like most guys I bought all the tools I could out of the sinclair catalog. At first I blindly did all of the "accuracy prep work" to my brass. I eventually got to testing each of the processes and weeded out the ones I could not see on target. Most all of these tools came from Benchrest in the days that they did not have the quality components we do today. Now you can just buy lapua brass and Berger bullets and get .25 moa without sorting or uniforming.
I always shoot new brass once. I dont do load development on new brass because it will change on fired brass. After shooting it once, I will size it in a full length bushing die, I use the wax hornady sells in the silver tin, a lot of guys use the one shot spray. After I size the case I wipe it off with a microfiber cloth to remove the wax. Trim and deburr if needed. Then I seat the primers, I use a 21st century hand tool. It is adjustable for depth, but it set it so I can feel the primer bottom out. Lately I have not even been cleaning the primer pockets. Then spin a snug nylon brush in the neck with a drill for 3 or 4 seconds. You want a drill not a slow case prep tool. Then dump powder and seat the bullets. On hunting stuff I dont do anything to the brass, for BR all I do is turn the necks. While that's a basic process it still needs to be done right. You need to have consistent shoulder bumps and consistent seating depths. I weight powder to the kernel as well. Those will definitely show on target if not. I dont clean brass or anneal it. Cleaning wont hurt, but it doesn't help. Annealing can help and it can hurt. Annealing is part of the tuning process, not all loads like that soft neck. Have been annealing for about 15 years and have not found a rifle that it improved my groups. In some cases it made them worse in others, it didn't hurt but didn't improve. I'm not against it, just dont do it blind. Test it both ways. I dont lube necks or use mandrels. In my experience I have got the best accuracy not touching the inside of the neck. Some lubes like graphite powder do ok, others like colloidal graphite have hurt my accuracy. That natural carbon layer polished with a tight nylon brush is still what I keep coming back to.
This is just my way, I have friends and customers that have far more elaborate processes that shoot just as well. I just prefer to do what matters and spend less time at the loading bench.

 

[Mike Dunaway]

Well for myself I would like to know the harm I am doing. I have the hand held/manual tools. I can see the problems that could happen. Am I enlarging the pocket depth or circumference? What damage to the flash hole. I am not a recreation shooter. I load a hundred or so rounds each season to hunt with and to verify data.