Pressure questions

[sam05]

I’m pretty new to reloading, so don’t be too hard on me. I’m loading 308 win, put together 10 rounds with 150 Hornady interlocks, 46 grains of blc-2 and Remington large rifle primer. They chamber in my rifle but the bolt closed just a bit tighter than a factory round so I adjusted my full length die down an 1/8th of a turn, they chamber with no effort at all. So I put together 10 more rounds, same bullet same charge same primer, same COAL. The first 10 rounds looked perfect after firing, next ten with die adjusted down gave me flattened primers. I’m saying all of that, did I size the second set of 10 too far?

thanks in advance fellas
Sam

 

[gwpercle]

Not really .
What happened with load #2 is the primer had a little room to run into the bolt face , giving it that flattened appearance ... the pressure is fine . One reason "reading" primers for pressure is tricky .

Some set their dies for a little resistance when chambering , in theory , best accuracy .
Hunters in the field want a round to chamber , even if the round has a speck of dirt on it so set their dies so no / very-little resistance is felt in turning down the bolt .

It's all personal , both methods are correct method #1 is better (in theory) accuracy and #2 is to assure easy chambering in hunting conditions .
You didn't size set #2 too far ...you simply sized them for easy chambering ...
And there's nothing wrong with that !
Remember ... Always more than one way to skin a reloading cat !
Gary

 

[Charlie98]

Your sizing technique is basically correct... so that's OK. Sizing the case a bit further could have changed the pressures a bit, and considering your starting load is knocking on the door of max published (Hodgdon) data, but I think what gwpercle said is more likely.

What are you shooting those in?

FWIW, I size my .308 brass for the weapon it's going in. My brass for my .308 Savage bolt gun is sized to give a bit of resistance camming the bolt down into battery (your load #1) so it doesn't overly work the brass. My brass for both my .308 Savage 99 lever-action is sized to minimums (your load #2,) because the lever does not provide a lot of leverage to close the bolt, and my M1a is sized to minimums because I want the bolt to close freely on a chambered round.

 

[Slamfire]

I use cartridge case headspace gauges to set up my dies.



the difference between the top and bottom notches is more or less the maximum amount of stretch a case can take before case head separations are a problem.



An example of too much clearance between case shoulder and chamber shoulder



Comparators work well, and as for my 7.5 X 55 Swiss rifles, are the only device on the market which I can measure case length changes before and after firing.



I recommend don't size to zero case shoulder to chamber shoulder clearance. It does not improve accuracy and instead will create problems in the future. You will encounter hard chambering, and hard extraction. There needs to be clearance between the case and chamber or the case will be compressed by the bolt lugs and the chamber walls after firing. The lugs and chamber are steel, they are operating below yield, they both stretch under the pressure, but relax to original dimensions. But, steel and brass relax differently, (brass is in fact operating above yield) and interference fit brass cases will at some point be under compression from the lugs and chamber after firing.






I recommend setting up your sizing dies so the shoulder is pushed back 0.003". There will be small variations in a batch as cases work harden, therefore there will be some where the shoulder will be set back somewhat less than the average. Three thousandth of an inch is enough that a little bit of unburnt powder won't cause hard bolt closure, and my cases lasted forever.

Shoot enough, I am certain you will come to the conclusion that reliable feed, ignition, and extraction are more important then theoretical tiny improvements in group size. While bench rest and F Class shooters desire the ultimate small group, they are still extremely careful to create ammunition that will feed and extract. You get a limited amount of time to shoot your string, having to knock out cases with a cleaning rod will ruin your score, as the wind will change during your down period! (The Range Gods are watching, waiting, for an opportunity to mess with your score!) My F Class buds don't feed rounds from a magazine and many don't have ejectors on the rifles. I do not recommend F Class reloading practices for anything except F Class competition.

I did have to go to a zero clearance case shoulder to chamber shoulder clearance with my 35 Whelen's. The case shoulder of a 35 Whelen is shallow. In some of my rifles I had misfires and hangfires till I installed a stronger mainspring and went to zero clearance. I am sure the shallow shoulder on a 35 Whelen cushions the firing pin blow. I do believe the sharp shoulders we see on the current F Class cartridges are there to maximize the energy delivered by the firing pin to the primer. Better and more consistent combustion.

 

[JerkyFreak]

This shows one of the pitfalls of using primer appearance to judge pressure.

Zero headspace the primers will look normal with very little flattening even though the load is over-pressure.

Excessive headspace gives severly flattened primers that look to be overpressure even at relatively mild loads.

 

[sam05]

Thanks for the quick replies guys, I am shooting these in a savage axis, fde SR ii, the academy sports special. I started at 46 grain charge after looking at all 3 of my manuals. I think I’ll back up .5 grains and run the free chambered rounds and reset my die so the bolt has that little bit of resistance because the first loads seemed to be the most accurate.

thanks
Sam

 

[edwardware]

They chamber in my rifle but the bolt closed just a bit tighter than a factory round so I adjusted my full length die down an 1/8th of a turn, they chamber with no effort at all.

Just to be clear, you turned the sizing die down 1/8 turn?

That's a huge adjustment in sizing! Go look at thread pitch, and figure out how much you changed sizing.

In all likelihood, you are observing primer signs of excess headspace, not pressure. I will disagree with the others and suggest you NOT buy a chamber gauge, and instead buy a comparator so you can measure shoulder position in fired and sized cases.

 

[gwpercle]

Thanks for the quick replies guys, I am shooting these in a savage axis, fde SR ii, the academy sports special. I started at 46 grain charge after looking at all 3 of my manuals. I think I’ll back up .5 grains and run the free chambered rounds and reset my die so the bolt has that little bit of resistance because the first loads seemed to be the most accurate.

thanks
Sam

Sounds like a Most Excellent Plan to me Sam ... Let us know how they shoot !

I always did like the Savage Axis rifles ,
Gary

 

[sam05]

You guys are awesome, I knew you’d have all the info I was looking for. You guys have given a couple of different ways to approach this and led me to some new toys I need to add to my bench! I will give these a few more goes and see what happens this weekend. I’ll let you guys know what happens!

Thanks
Sam

 

[Varminterror]

I cut the shoulder and neck out of some of my small base dies, making my own body dies, because I do not want to size to minimum headspace just to thin out the body. Small base dies should really be body dies only - but I get why folks want only one step in the process. But we often end up with excessive headspace and undersized necks, when all we want is a smaller body diameter at or near the casehead… that doesn’t make sense.

 

[cfullgraf]

Sierra Bullets has some good information that can be found on line about sizing and preparing cases.

One notable point, sizing for bolt guns is a bit different than sizing for gas guns for best accuracy, case life and function.

Good reading. Search on Sierra Bullets and look for their information pages.

 

[AJC1]

Just to be clear, you turned the sizing die down 1/8 turn?

That's a huge adjustment in sizing! Go look at thread pitch, and figure out how much you changed sizing.

In all likelihood, you are observing primer signs of excess headspace, not pressure. I will disagree with the others and suggest you NOT buy a chamber gauge, and instead buy a comparator so you can measure shoulder position in fired and sized cases.

I agree. I think if he clocked with a sharpie and adjusted the width of his marks he would get much better results. The tools give good data but technique can help a lot as well.

 

[AJC1]

I’m pretty new to reloading, so don’t be too hard on me. I’m loading 308 win, put together 10 rounds with 150 Hornady interlocks, 46 grains of blc-2 and Remington large rifle primer. They chamber in my rifle but the bolt closed just a bit tighter than a factory round so I adjusted my full length die down an 1/8th of a turn, they chamber with no effort at all. So I put together 10 more rounds, same bullet same charge same primer, same COAL. The first 10 rounds looked perfect after firing, next ten with die adjusted down gave me flattened primers. I’m saying all of that, did I size the second set of 10 too far?

thanks in advance fellas
Sam

Reading primers in my opinion is a comparative exercise once your basics are covered. Your headspace is controlled, your using the same manufacturer of brass and your comparing one powder charge to another. This should not be done between different brands of primers either. Reading primers can give you good information, but they need to indicate pressure of a single variable with all others being controlled. As a side note, savage has a long history of having excessive clearance from bolt to firing pin, resulting in cratering. If your gun does that, the ammount/severity is another sine. Stop before piercing, as gas cutting ruins a bolt fast.

 

[EricBu]

I’m pretty new to reloading, so don’t be too hard on me. I’m loading 308 win, put together 10 rounds with 150 Hornady interlocks, 46 grains of blc-2 and Remington large rifle primer. They chamber in my rifle but the bolt closed just a bit tighter than a factory round so I adjusted my full length die down an 1/8th of a turn, they chamber with no effort at all. So I put together 10 more rounds, same bullet same charge same primer, same COAL. The first 10 rounds looked perfect after firing, next ten with die adjusted down gave me flattened primers. I’m saying all of that, did I size the second set of 10 too far?

thanks in advance fellas
Sam

Possibly you nocked the shoulder back when you adjusted the die down. Do you have a case gauge? If you drop it it in the gauge, and it drops below the flush line, you bumped the shoulder to much...this can definitely cause an over pressure situation.

 

[barnfrog]

Just to be clear, you turned the sizing die down 1/8 turn?

That's a huge adjustment in sizing! Go look at thread pitch, and figure out how much you changed sizing.

Almost 0.009" to be inexact. The thread pitch of standard reloading dies is 14, so one full turn would be a fourteenth of an inch, or 0.0714". One eighth of that is 0.0089", which is a lot. You may want to adjust your die back a bit so you're not overworking your brass.

 

[AJC1]

Possibly you nocked the shoulder back when you adjusted the die down. Do you have a case gauge? If you drop it it in the gauge, and it drops below the flush line, you bumped the shoulder to much...this can definitely cause an over pressure situation.

Do we call this the AD Ackley disproved, as in reverse of increasing case capacity.

 

[NMexJim]

On Hodgdon site, starting load for BLC-2 with 150 grain bullet shows 45 grn starting and 48 grn max. Neither my 10th or 11th Hornady editions show any data for 150 grain bullets and BLC-2. Regardless, by Hodgdon, you’re running about mid-range and should be fine pressure-wise.

I too highly recommend comparators and case gauges. They take the guess work out of the equation. Same with bullet seating gauges such as the Hornady below.

https://www.hornady.com/modified-cases#!/

Can I ask what rifle you’re loading for? You didn’t mention your COAL measurement or where on the bullet you’re measuring that from - tip or ogive Powder density might enter in, but I don’t use BLC-2 and would defer that to others.

You reasoning seems spot on. Invest in the measurement tools. One of the folks that taught me a bunch with reloading told me that “you don’t know what you don’t know”. I laughed when he said that. I don’t anymore. The more you know, the better your rounds will be.

 

[EricBu]

Do we call this the AD Ackley disproved, as in reverse of increasing case capacity.

I call it the "oh sh#t" unimproved. Buddy of mine that I started down the loading path a few years back bought an AR, and decided to reload 5.56. His first try at bottlenecks. He calls me up, all upset. Blowing primers, and sometimes a light strike/no boom. Every time he got a light strike, the bullet stayed in chamber, and he had to rod it out. He also mentioned having to hit the FA a lot. Yeah...rounds were chambering in the lands. I went over...poor guy had cranked his Dillon sizing die down on his 550 until it was camming over hard. I brought 2 gauges, a Wilson and one of my hunnies. His shoulders were set back so far, I swear the rounds were dropping an eighth inch below flush on the hunny, and we'll below the nogo line on the Wilson. The only reason he still has a gun is that he started with an obscenely low charge.

 

[AJC1]

I call it the "oh sh#t" unimproved. Buddy of mine that I started down the loading path a few years back bought an AR, and decided to reload 5.56. His first try at bottlenecks. He calls me up, all upset. Blowing primers, and sometimes a light strike/no boom. Every time he got a light strike, the bullet stayed in chamber, and he had to rod it out. He also mentioned having to hit the FA a lot. Yeah...rounds were chambering in the lands. I went over...poor guy had cranked his Dillon sizing die down on his 550 until it was camming over hard. I brought 2 gauges, a Wilson and one of my hunnies. His shoulders were set back so far, I swear the rounds were dropping an eighth inch below flush on the hunny, and we'll below the nogo line on the Wilson. The only reason he still has a gun is that he started with an obscenely low charge.

Starting at start has saved a newb more than a few times I'd venture. I'm positive you got him in task and dialed in.

 

[sam05]

Ok guys I loaded up 10 rounds at 45 grains of blc2 and 10 rounds at 45.5 grains, got about half of them that the primers looked fine after firing and half were a little flattened, so I think they are safe and the problem is that I oversized them and as you guys explained the primer has some room to back out and get flattened. All three powder charges seemed to hit about the same point of aim. I didn’t shoot any groups just smackin 12 inch steels out to about 300 but they were pretty consistent. Thanks for all of the ideas and help guys!

Thanks
Sam