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Flattened primers

Mlgrace

Hello, I have been loading the 7mm-08 for a few years. All of a sudden I am seeing flattened primers although I am no where near max on the load. No other signs of pressure. Group is excellent. Currently loading Hornady 139 SST on IMR4350 at 45.5grains. Am I just seeing the primer wrong maybe?

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If you haven't changed lots of powder or weren't shooting in a significantly higher temperature than you have shot with this load in the past - my first suspicion would be that you pushed your shoulders back just a bit too far when resizing. The "loose" cartridge case is then allowed to slam rearward, striking the bolt face. The kinetic energy causes the primer to keep going in that direction, thus being allowed to flatten - giving "false" signs of being over pressure. You could also shoot a few rounds over a chronograph to ascertain they are (or not) hot loads.
 
searcher said:
If you haven't changed lots of powder or weren't shooting in a significantly higher temperature than you have shot with this load in the past - my first suspicion would be that you pushed your shoulders back just a bit too far when resizing. The "loose" cartridge case is then allowed to slam rearward, striking the bolt face. The kinetic energy causes the primer to keep going in that direction, thus being allowed to flatten - giving "false" signs of being over pressure. You could also shoot a few rounds over a chronograph to ascertain they are (or not) hot loads.
Click to expand...
This might be. I will check it tomorrow but I do not recall making any changes to this die Set.
 
look fine to me..unless heavy bolt lift..carbon rings dirty barrels...and longer bearing surface on bullets may cause flat prims..horny bullets usually have a longer bearing surface...the sst may have a longer bearing surface that can cause pressure issues...in my rifles it does, I shoot a 6xc with 108 bergs and tried the 105 horny match and I got heavy bolt lift with same load...but that's my rifle they r all diff most of the time
 
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What was the temp that day ? Maybe it went up somewhat higher than you usually shoot in, this could cause a slight increase in pressure.
And also are you OAL of the case within max length ? Or could your necks have gained and are pushing into the chamber some ? Some thing to check.
 
6MMsteve said:
look fine to me..unless heavy bolt lift..carbon rings dirty barrels...and longer bearing surface on bullets may cause flat prims..horny bullets usually have a longer bearing surface...the sst may have a longer bearing surface that can cause pressure issues...in my rifles it does, I shoot a 6xc with 108 bergs and tried the 105 horny match and I got heavy bolt lift with same load...but that's my rifle they r all diff most of the time
Click to expand...
Lot lift is smooth as can be. Like I say I see no other indicators of pressure issues.
 
Bill K said:
What was the temp that day ? Maybe it went up somewhat higher than you usually shoot in, this could cause a slight increase in pressure.
And also are you OAL of the case within max length ? Or could your necks have gained and are pushing into the chamber some ? Some thing to check.
Click to expand...
75 degrees and low humidity. I live and shoot at 7000 feet. I will double check the COL. I actually check every single charge and COL. But maybe it got by me.
 
Measure the base to shoulder of fired and sized brass with a comparator. If you have 0.004" or more difference your primers are backing out then reseating as the case head reaches the boltface and causing flattening. Not harmful but if this is your finding consider a little less bump. I think this was alluded to in one of the first responding posts.
 
How long is it between the time this ammo was loaded and when it was shot? If there is any more of this particular batch, if the bullet is seated slightly deeper into the case is there a perceptible pop?
 
Those primers are not what people are talking about when they say flattened primers.
Most flattened primers result from using new brass. New brass has to fit every gun chambered in 7mm-08 so the shoulders are generally short of even a match type chamber.
When fired in the rifle the only thing keeping the brass from moving forward 0.010 of an inch is the extractor.
The firing pin pushes the sloppy loose brass forward into the chamber and upon firing the casehead slams back into the boltface flattening the primer.
 
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Mlgrace said:
This might be. I will check it tomorrow but I do not recall making any changes to this die Set.
Click to expand...
Shell holders vary in dimensions. Could you be using different s/h's with that die. It is always best to measure H/S vs. assuming the die/ s/h are sizing correctly.
Are the chamber and brass free of any lube?
 
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