Pressure signs 7mm-08

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gstprecision

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I have a 7mm-08 with a 26” heavy barrel and fast twist. I want to shoot 162 bthp Hornady.

I have been using H414 powder and been getting flatten primers. I have only been loading to below max loads. My manual and Hodgdon site have loads from 43 gr to max 45 gr.

I thought it was my brass at first, I was using Norma 308 necked down. I got some Hornady 7mm-08 brass, much better but still flattening the primers at 43gr loads.

I am thinking now either the COAL is too short and compressing powder creating pressure. Or the recommended loads are a bit hot for the the long heavy bullets.

I have measured fired brass and the chamber is within specs. Neck is right a 0.315”

Any ideas/experience.
Thanks
 
First off the primer is a poor indicator of pressure.

You can get flattened primers by not sizing the brass properly.

Suggest measure a fired brass from base to datum line of the shoulder, now measure a sized piece. There should only be 1 or 2 thousands difference, the sized piece being the 1 or 2 thousands shorter.

What happens is, the firing pin drives the cartridge forward, due to a sloppy fit, this leaves a larger than design space between the bolt face and the cartridge base. The cartridge case when fired will push the primer back toward the bolt face as well as the case causing the flattened appearance of the primer.

Your case life will be short and you will be trimming cases frequently.

Brass sized correctly will last a long time (10's and10's of firing) with very little occasion to trim.
 
There's many variables that could cause high pressure so it's often a process of changing one thing at a time until the solution is found.
Every once in a while I run across a rifle that will get high pressure long before getting to the book listed max load and I've found that changing powder often calms things down a bit. I had a 270 Winchester once that would send pressure through the roof with light loads of 4350 and 4831, I eventually changed to 7828 and was able to load up to listed max loads with no high pressure.
 
I have a 26" Kreiger on a 7/08 and my loads are quite low compared to book.

I have an accuracy load at 42(H4350) grains and hunting load at 42.8(W760.H414).150gr projectiles.

Your longer, and tighter barrel/chamber is going to give you more pressure.

How is your bolt lift and what are your speeds?

In this case I'd probably start at 39 grains or less of 414 see what your speeds are as you increase.

Also, there are softer and harder primers , so like said it is not the best indicator but it can be a tool.

If nothing remedies , you could go to a slightly faster powder.

****I just checked my load history and when I was testing it looks like I tried 162 AMAX , 41.6 to 42.4(W760) was my test range , I didn't settle on this projectile.

You need those velocities to determine whats happening.A 162gr out of a 7/08 shouldn't be much faster than 2600 ft/sec or so.
 
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An interesting read. I have 2 plain Jane 7-08s; a Stevens 200 and a Savage 11. I loaded some significantly less than max loads with 140 and 150 grain bullets ahead of H4895 last year and got pierced primers. I figured maybe due to the heat I had some elevated pressures. I haven't loaded any more of them yet/since, but I'll definitely be following the discussion here as a result.
 
What velocity are the loads producing? I have had rifles produce the max velocity listed in a manual, at 5% below the max load. I have also loaded five percent above the load in a manual, to achieve the max velocity listed. Case volume, powder lots, and barrel and chamber dimensions can vary enough to cause these discrepancies
 
Hornady No.10 Reloading Manual
7mm-08
162 gr BTHP No.28405 COL 2.755

H414 powder, - Start load 37.5 - Max load 46.6

Question, how far out (Max OAL) will your rifle let seat your bullets, meaning how much further out than recommended OAL can you seat this bullet.
 
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Thanks for all the replies.

I took the measurement from a sized case vs a fired one and there is very little difference, both in length (to the shoulder) and also in expansion which was about 0.002” to 0.003”. At first I was leaning toward neck tension but even that is within specs.

I have not chronographed the loads yet. I will put a few loads together this week and go chrony them.

Tha ks
GST
 
Flattened primers are not the greatest indicator of hot loads, It can happen with new brass that has not been fired in your gun. You need to look after the base to shoulder datum length, your COAL as well as your neck OD. The sized 308 cases could well be bigger on the neck OD than the Hornady brass, just remember, that results in a tighter ID on fired cases. 2 thou shorter on the sized brass vs fired brass is tolerable, people partial size or neck size to maintain the closer shoulder fit on fired brass, all you get there, is whatever the brass springs back to. That stuff is what you have to sort out first. I have one 7-08 that makes 2860 with a 140gr bullet and 760, and a different one that is nearer to 2725 with the same load, which shows as 1.5gr under max with the original data, at the time I bought that powder. I don't worry about initial new case OAL except to make sure there are no weird ones in there, that can occasionally happen. I check them again on first firing, and trim them all to the same length. Don't worry about OAL case length til 3rd firing, then I check them all again, make sure they are at least .005 under, but, all mine are neck sized after first firing. FLS sized cases should be checked every time you shoot them, depending on how much you bump the shoulder. And pickup a Forster or Lyman or Imperial dry neck lube kit, check lubed vs no-lubed with that, you will immediately feel the difference, helps save neck stretching when sizing.
 
Agree with BCBRAD, primers can be a poor indicator of pressure. Over the years I've had 3 different 7mm/08 rifles. I presently have 2. In all 3, WW760/H-414 was a great powder with 140-150 gr bullets. In 2 of my rifles I was able to work up to 49 grs of WW760 with a 145 gr Speer. In the other the max was 47.5 grs. Velocity in all were 2850/2900 ft/sec. Lately in my heavy barreled 26" 1/8.5 twist I've been using RL-15 with 160 gr class bullets and find the accuracy to be outstanding.
 
I had similar issues with my 308. I would look at your throat length. In my case I couldn’t get any where near mag length because of a short throat causing me to load short and spike higher pressure. I ended up having it reamed out 0.100” longer to get to mag length with the bullet I shoot and that had helped a lot.
 
GST There is often a misunderstanding in what a max load is. Many assume what is printed in a loading manual to be gospel for all rifles. That just isn't so. A loading manual is a reference or guide. The max load in YOUR rifle could be a couple grains higher or lower than what is published in a loading manual. There are a number of things that can affect pressure. Some bores may be a little tighter than others .A tighter bore will increase pressures. Different cases will have different internal volumes. A heavier case will have less internal volume and will result in higher pressures. Some manuals tell you when using military cases to reduce powder charges by 2 grs due to the reduced internal capacity. I have found that for every 10 grs more a case weighs the internal capacity is reduced by 1 gr. Some barrels have shorter throats and will build pressure quicker that a barrel with a longer throat or freebore. How far out you seat your bullets will affect pressure. As already mentioned how you size your cases can affect the appearance of the primers. Don't worry about loading to the max listed in some manual. Start at powder charge at least 3 or 4 grs below what is listed as max and work up with your components and seating depth etc. Pay attention to things like primer deformation, case expansion and accuracy of your load. Tight groups are far more important than wringing out the last 30 or 40 fps.
 
Winchester had some crappy brass a while back.Had a proven load with Win brass in a 22-250 and used some new brass .The primers went to twice the diameter and you could hardly open the bolt.Tossed the brass and used the same load in Win range brass business as usual no pressure signs.
 
Gstprecision, Richard Lee, in his book Modern Reloading, talks about an experiment where a compressed load caused a drop in pressure, compared to the same load with airspace in the case.
 
Hodgdon's loads are really hot compared to Hornady's book.
I've seen starting loads higher than max loads when you look at both. 162 is a long bullet for 7 08. Mine really likes 140-150
 
I finally went to the range with reduced loads. I am still getting somewhat flat primers but I would say they are normal.

I am getting about max velocity with 40-41 gr loads, 2600-2700 fps. Accuracy was very good. Will need to fine tune but it should be good.

Thanks all for the replies.
GST
 
I run 38.5 gr of varget behind the 162 eld match. It's a light load. Gives me 2566 fps sd of 3 and es of 7 fps. It is a .6-.7 moa load at 200m out of a gas gun. I'm also using lapua brass and cci br primers.

I think you're pressure issue was due to the resided 308 cases having to thick of a neck and not letting go of the bullet enough. I've seen this problem in my tight necked 22-250. 32.5 varget would loosen primer pockets on unturned brass and have no signs on turned brass.
 
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