Pressure signs
05-04-2010, 03:08 PM
#1
Fork Horn
Thread Starter
Join Date: Jan 2008
Location:
Posts: 132
Pressure signs
I have a question for all you reloaders, what are the signs of excessive pressure? I know a bolt that is hard to open is one sign but what are the others? I bought a Hornady bullet compater so I am seating the bullets around 0015 of the lands. I understand that this may improve accuracy but also increase pressure. Any help would be welcome.
05-04-2010, 07:45 PM
#3
Guest
Posts: n/a
Flattened primers, loose primer pockets, heavy bolt lift. Extractor marks on the case. Velocity suddenly shooting up, having to use a wooden dow and hammer to knock open the bolt
Flattened primers are decieving and should be noticed in conjunction with other signs. I have been experimenting lately with case head expansion but can't get an accurate read on if I am over pressure.
Flattened primers are decieving and should be noticed in conjunction with other signs. I have been experimenting lately with case head expansion but can't get an accurate read on if I am over pressure.
05-05-2010, 08:21 PM
#4
Typical Buck
Join Date: Mar 2007
Location: Wide open Nevada
Posts: 515
Use tested data!
If you're seating longer than standard pressure should go down not up in most cartridges.
Examples , I've a 22-250 after sending 9 rounds of 40gr HP down range the 10th came out with out a primer . Rounds 7,8,9 showed gas leaks ,and 5,6 were flat. No hard lift with any of those Winchester factories. Repeat above with my handload 31grs of 3031 55 gr fmj bt. Same result. All of the loads were well under pressure limits but the 98 action and varmiter bbl were just holding too much heat for rapid fire on a hot day.
Use the tested data don't start at maximums.
In 308,06',and mauser cased cartridges you may see flatened primers ,gas leaks or loose primers,a shiney ring about 1/2"up from the case base ,or/and harder than normal bolt lift,but not always .
Example I've this 30-06' I chrono'd a 150 btsp at 3100 fps with 54grs of 4350 (I'd call bs on me too if I wasn't there) ,I believe book max is 56 or 57 (best load is 50.1) no bolt lift issues no flat primers ,no shiney rings .
I once had a 7x57 that cratered primers with about any 139gr load but shot even near max loads with 175s with no signs.
I guess my point is this by my research and expirence ,primers are large rifle primers are flat to the pocket edges around 62,000 ,they fall out around 65,000,case seperation should happen around around 65000 psi also. Hard bolt may not happen until upwards of 70000psi.
Measuring case head expantion is only valid on virgin brass and then only with known pressure tested cases of the same lots for comparison ,as I have read and understand.
If you're seating longer than standard pressure should go down not up in most cartridges.
Examples , I've a 22-250 after sending 9 rounds of 40gr HP down range the 10th came out with out a primer . Rounds 7,8,9 showed gas leaks ,and 5,6 were flat. No hard lift with any of those Winchester factories. Repeat above with my handload 31grs of 3031 55 gr fmj bt. Same result. All of the loads were well under pressure limits but the 98 action and varmiter bbl were just holding too much heat for rapid fire on a hot day.
Use the tested data don't start at maximums.
In 308,06',and mauser cased cartridges you may see flatened primers ,gas leaks or loose primers,a shiney ring about 1/2"up from the case base ,or/and harder than normal bolt lift,but not always .
Example I've this 30-06' I chrono'd a 150 btsp at 3100 fps with 54grs of 4350 (I'd call bs on me too if I wasn't there) ,I believe book max is 56 or 57 (best load is 50.1) no bolt lift issues no flat primers ,no shiney rings .
I once had a 7x57 that cratered primers with about any 139gr load but shot even near max loads with 175s with no signs.
I guess my point is this by my research and expirence ,primers are large rifle primers are flat to the pocket edges around 62,000 ,they fall out around 65,000,case seperation should happen around around 65000 psi also. Hard bolt may not happen until upwards of 70000psi.
Measuring case head expantion is only valid on virgin brass and then only with known pressure tested cases of the same lots for comparison ,as I have read and understand.
05-07-2010, 01:17 PM
#5
Typical Buck
Join Date: Nov 2008
Posts: 588
Flattened primers, loose primer pockets, heavy bolt lift. Extractor marks on the case. Velocity suddenly shooting up, having to use a wooden dow and hammer to knock open the bolt
Flattened primers are decieving and should be noticed in conjunction with other signs. I have been experimenting lately with case head expansion but can't get an accurate read on if I am over pressure.
Flattened primers are decieving and should be noticed in conjunction with other signs. I have been experimenting lately with case head expansion but can't get an accurate read on if I am over pressure.
I agree on the primers. My 3006 flattens the primer on every case fired in the gun, even some minimum loads.
05-28-2010, 05:46 PM
#6
Nontypical Buck
Join Date: Nov 2003
Location: Texas
Posts: 2,695
05-29-2010, 04:12 AM
#10
Nontypical Buck
Join Date: Nov 2003
Location: Texas
Posts: 2,695
cause zrex, the more jump you have, the farther the bullet travels before meeting the resistance of the lands, which actualy increases case capacity, more capacity with the same load produces less pressure. So yes, I'll generaly say that .015" off the lands won't increase pressure.
Another thing to note is, with no jump (loaded to or close to the lands)upon detonation, pressure has to build enough to start the bullet into the lands, and pressures peak before the bullet gets into the barrel, with some jump, it takes less pressure to get a moving bullet started down the barrel so peak pressure is achieved after the bullet is into the barrel. where your bullet is at the time of peak pressures determine pressure signs as well.
Kinda like when your out 4-wheeling, if you go to cross a rock or a log, its easier to get over something if you keep moving, stop against even a small log and its harder to get over than if you roll up to itand keep moving. Hope this makes sense.
RR
20 to 40 thou? or do you mean .002-.004?
Another thing to note is, with no jump (loaded to or close to the lands)upon detonation, pressure has to build enough to start the bullet into the lands, and pressures peak before the bullet gets into the barrel, with some jump, it takes less pressure to get a moving bullet started down the barrel so peak pressure is achieved after the bullet is into the barrel. where your bullet is at the time of peak pressures determine pressure signs as well.
Kinda like when your out 4-wheeling, if you go to cross a rock or a log, its easier to get over something if you keep moving, stop against even a small log and its harder to get over than if you roll up to itand keep moving. Hope this makes sense.
RR
20 to 40 thou? or do you mean .002-.004?
I understand all that , the point is I dont think its a good idea to tell people .15 off lands is anything to worry about, my cases will start flowing metal at the back, if I were to seat that close.
Not everyone has 120 gr capacity to play with , most are around 40-to 70 and people like to stuff them.
