Author Topic: Flattened primer question (Read 937 times)

LouisV · « **on:** May 31, 2004, 12:43:12 PM »

I'm loading for a Savage model 11 in 7-08 rem. I'm useing 37grains of Varget behind the 162 grain Amax in Winchester cases that are necksized. The O.A.L. is 2.800" and the primer is the CCI BR-2. The average velocity is 2421 fps. The concern I have is that the fired cases show some flattening and a slight cratering of the primer. The Hornady manual shows the max load at 39.5 grains and 2600fps. I know this is a case of "your mileage may vary". But I'm getting pressure signs at what I thought was a moderate velocity. Is anyone else shooting a combination similar to this with the same results? LouisV

Duffy · « **Reply #1 on:** May 31, 2004, 06:38:52 PM »

I have a little different combo but still a 708 but in a Encore. My 140g load @ 2600 gives a pretty flat primer but a factory Hornady 139g light mag load is just as bad if not a bit flatter. Are you having bolt lift problems? How's accuracy? Just for giggles seat the bullet about .010-.015 deeper in the case and see if the flattening goes away and accuracy improves or stays the same.

Ryan

Iowegan · « **Reply #2 on:** May 31, 2004, 06:51:52 PM »

Primer flattening is not a good indicator of pressure in rifles. With handguns, I tend to pay attention to it a little more. In rifles, it is an indication of pressure but not necessarily over pressure.

Cross reference your load between two or more good reloading manuals (Hornady is a good one). If the listed loads agree with your charge, and your chronograph results are in order, then you probably don't have a pressure issue. Now if you're experiencing difficult extraction, case head separation, or split cases, that's a true sign of over pressure.

On another note: The 7mm-08 optimizes with 140 gr bullets. I load 42 gr of Varget and get one hole, 100 yd groups, with a MV of 2800 fps. I use the 139 gr Hornady BTSP. With heavier bullets, my Rem 700 groups will open up to 2 or 3 inches. If you chart the 139 vs the 162, you'll see the 139 starts with 200 ft lbs more energy and remains more clear out to 300 yds. From that point on, the 162 gr bullet retains more energy. Seeing that a 7mm-08 is considered a 250 yd max gun for deer, I really can't see a good reason for using a heavy bullet in that light cartridge.

PAShooter · « **Reply #3 on:** June 01, 2004, 12:59:13 AM »

I have come across primer flattening in 2 different Savage rifles, my 111 in .243, and my friends 110 in .300 Win Mag. Both rifles showed no other signs of pressure. This was both with factory and low to moderate reloads. I asked around a few other shooters I know, and the only thing I can figure is that it is a Savage thing, maybe something in the way they machine their bolts or chambers. I just live with the flattened primers, as my .243 is a good shooter.

Donna · « **Reply #4 on:** June 01, 2004, 01:48:44 AM »

Hello PAShooter,

Case head separation and split cases are not necessarily a sign of over pressure. Most of the time case head separation is an indication of either head spacing problem or a sizing die that is setting the case shoulder back too far and split cases could be form work hardening of the brass. As I understand it flattening primers is an indication of pressures that are getting close to over pressures and cratering primers are the begging signs of excessive pressures in either handguns or rifles alike. It is not unknown to have over pressure signs while still in the range of published load data. This is one reason it is suggested to start at the low side of the published load data or 10% below your load if you change components and work up. Reloading manuals can vary greatly on their load data from one to another. The best advice I can give you is to have quite a few manuals on hand and reference them and take the lowest powder charge weight of all of them, work up slowly and stop at the pressure signs. If that load is unsatisfactory change the appropriate component/s and start over again.

Donna

Dave in WV · « **Reply #5 on:** June 01, 2004, 02:43:40 AM »

LouisV, shoot some factory ammo and compare the primer condition to your hand loads. If the factory ammo primers look the same or worse then you know you're ok. If your bullets in your hand loads are against the lands you can get high pressures. Dave

LouisV · « **Reply #6 on:** June 01, 2004, 04:39:46 PM »

Thanks for all the responses, I got more than I expected. It's good to hear that this maybe common to Savage rifles as PAshooter relates. But I'll find other data to check it against. I have found great differences for loads in other calibers between sources. The only reason I use such a heavy bullet is for ram loads at silhouette matches. Our rams can be very tough sometimes so I need the retained energy at 500 meters. I mostly use 130 MKs for the other targets and 120 Ballistic tips for deer. Duffy mentioned seating them alittle deeper. I'm back off the lands some already but I may give that a try. Accuracy is good and I haven't noticed the bolt being stiff. Thanks again. LouisV

Iowegan · « **Reply #7 on:** June 01, 2004, 07:21:22 PM »

Seating the bullet deeper will increase chamber pressure and compound your problem.

Some more primer tidbits: SAAMI has standardized the flash hole diameter in rifle cases to .080" (about 5/64"). If you do the math, a 50,000 psi chamber pressure load will exert about 1000 psi through the flash hole and into the primer. A token increase in flash hole size of a few thousandths, will increase the pressure on the primer by 300-400 lbs (caused by the decapper pin). This would make a very safe load appear to be over pressure if you use the flat primer as an indicator. The pressure inside the case didn't change, just the pressure exerted on the primer changed. Some primers have softer cups than others. Using exactly the same load, one primer might flatten while another brand looks normal. I wouldn't put much faith in "reading" the primer.

Donna hit on headspace so I'll expound. The weakest place on a bottle neck rifle case is the point where the case wall meets the solid head. This is the place where case head separation occurs. Assume a rifle has an "in spec" headspace. When fired, the case will be pushed forward by the firing pin. Then the internal pressure will push the primer out slightly. As pressure increases, the case is driven back against the bolt face and forces the primer back into the hole. If the load is over pressure, the case will show a bright ring at the head/wall point. In extreme pressure cases, the head may separate from the body, even if the headspace is in spec. If the headspace is excessive, it's almost sure to cause a bright ring or even head separation with normal pressure loads. The movement of the case within the chamber will cause a primer to flatten too.

A cheap trick for testing headspace is to fire a case loaded with only a primer, (no powder or bullet). When the case is extracted, check the primer to see if it has backed out. If the primer backs out more than .005" higher than the head, it's an indication of excessive headspace.

PAShooter · « **Reply #8 on:** June 02, 2004, 01:40:54 AM »

Hello Donna,
Thanks for the feed back. I reload for several different calibers, chambered in different makes of rifles. I have on hand several manuals, and also check the component manufacturers data on line. I always start low, and work my way up when creating a load for a specific rifle. I inspect my brass for signs of high pressure. I just noticed the Savage rifles tend to flatten primers for some reason. This is with several different powder and primer combinations. I haven't seen any other signs of excessive pressure. Like I said earlier, I have spoken with several other shooters, and they noticed the same thing with Savage rifles.

LouisV · « **Reply #9 on:** June 02, 2004, 05:50:23 PM »

Iowegan.I'll take your advice about primers along with the Savages tendency to flatten primers and leave the load as it is for now. Headspace should be ok with this load as I only use a collet die to necksize after the first fireing. I learned that lesson years ago when loading for an old mauser. I followed the die makers instructions and turned the die all the way down to the shell holder. I was lucky, the first shell I fired didn't separate completely, the rest went in the trash. Duffy mentioned the T/C Encore which I noticed is the gun that Hornady used as the test gun for their 7-08 loads in the manual that I have. I'm sure they have other equipment or methods to check it with, but I wonder how they deal with something like this.LouisV

Donna · « **Reply #10 on:** June 02, 2004, 06:26:27 PM »

LouisV

I had the same thing happen to me with a Hornady die in 22-250. The die was setting the shoulder back to far with the die turned down to touch the shell holder. I readjusted the die so that it no longer set the shoulder back and that solved the head separation problem. And the die still resized the cases just fine.

Donna

Duffy · « **Reply #11 on:** June 02, 2004, 06:38:46 PM »

Indeed seating the bullet deeper into the case will eventually raise pressure but it has to be moved back quite a bit. I noticed a pressure drop when going from .010 off the lands to .030 and didn't notice it increasing again until it was at least .070 off. Besides the accuracy had gone to pot by .050 anyway, I just kept going to see the results. On the smaller cases like the 22 Hornet it's going to climb quicker but on the medium cap cases there seems to be quite a bit of leeway.

Ryan

Iowegan · « **Reply #12 on:** June 02, 2004, 07:02:58 PM »

LouisV, I used to work in a lab and got to see how everything was tested. The pressure tests were all done with a special barrel that didn't even resemble a gun. It had piezo sensors attached that measure the pressure on a graph. You could see the primer flash, start of the burn, ramped up pressure, peak pressure, and tapering down pressure as the bullet traveled down the barrel. Very slick device. When they actually tested the ammo in a real gun, the pressure limits had already been established. Then it was a matter of firing for accuracy and using a chronograph to document velocity.

I got several opportunities to see Winchester and CCI / Speer's facilities. They liked to use guns that were common with the cartridge under test, ie Winchester '94 for a 30-30. In my lab, we tested all makes and models along with all American made ammo. It was very interesting to see how some of the guns performed when tested against a different gun in the same chambering. We saw all types of variations with headspace, throat depth, and bore diameter. It was not unusual to see one gun work just fine with a given cartridge and another would shoot lousy. Switch ammo and the conditions might reverse. This is one reason why reloading manuals vary so much with their recommended loads. Everything is "gun dependent". No one cartridge would shoot well in all guns and no one gun would shoot all cartridges well. That's why it's so fun to reload. You can taylor your cartridges to the gun for optimum performance and compensate for variations in headspace, throat depth and bore.

Wlscott · « **Reply #13 on:** June 04, 2004, 05:32:14 AM »

Donna, I think I was having the opposite problem you were having with your 22-250. I am loading for a Winchester Md 70 in 300WSM. I full length resize with an RCBS die, and all of the sudden I started seeing flattened and cratered primers. I was also experiencing difficulty lifting the bolt. It wasn't on every round though. I also noticed a drop of about 200 fps in velocity. This was the exact same load, just a different batch. You can imagine the confusion at seeing high pressure signs, but going from 3100 fps to 2900 fps.

After much discussion on the Short Mags board, we finally decided that I was not bumping the shoulder back FAR ENOUGH. I was just screwing the sizing die in until it touched the shell holder. When I barely bumped it in (Maybe another 1/32 of a turn), and resized the cases, the problem went away.