How tell tell if a load is too "hot"??
- Thread starter logan1080
- Start date
Difficulty closing the bolt indicates problems with case length, resizing or a bullet sticking into the lands. I think you said your rifle was a .300WSM and the WSM's sometimes need the shoulder bumped back a few thousandths during resizing in order to easily chamber. For most calibres this isn't necessary, but the WSM's do seem to push the shoulder forward some. If it was a custom target rifle, it could also indicate that the case neck walls are too thick and are binding in a very tight fitting chamber. Since you are shooting a factory rifle, that is very unlikely.
If you are getting up to high pressures you should first notice flattened primers. They are not a truly reliable sign, but do at least indicate you are getting up there. Next will be difficult bolt lift and/or hard extraction. You may also start seeing extractor impressions on the base of the brass. Pay attention to every round fired as you work up in your loads, carefully feeling the effort needed to lift the bolt and extract. When I have had bolt lift get harder it is not for the whole motion, just the first little bit as the case is cammed loose from the chamber, so be aware of the operations on every round.
To minimize the number of rounds you load during development, it is not a bad idea to load a string of 5 to 10 rounds with a one round at each charge weight, working up to max in around 0.5gr increments. In 10 rounds or less you will find the upper load limit for your rifle and know where to stop when you load batches for accuracy testing.
Mark
Exceeding the maximum load in the manual does not mean that your load is producing excessive pressure in your rifle.By the same token,just because your load is not over the maximum listed in the manual,it may not be within the SAAMI pressure standard for the cartridge.There are far too many variations in chambers,barrels,powder lots,brass volumes,to make such assumptions.
Fouling is also not an accurate way to determine pressure.
Fouling is also not an accurate way to determine pressure.
If you can beg, borrow or steal a chronograph you will get more info to add to your list. Flattened primers means you are close or right at limit. Stiff bolt lift means you are too hot. A chronograph will let you know if your velocity is in the normal range.
However every rifle is different so the more info you have to base your decisions on the safer you will be. I love having a chronograph, I view it as my #2 "extra" tool in my reloading setup. (after basic setup; dies, press, etc. my #1 extra is digital scale) Plus when I go to the range often I get to shoot other fellas rifles so they have a velocity value.
Start low and work up watching how flat the primers get. Stop when you get accuracy. A max load giving a 2 MOA group is less useful than and 1 MOA group thats 100 FPS slower.
However every rifle is different so the more info you have to base your decisions on the safer you will be. I love having a chronograph, I view it as my #2 "extra" tool in my reloading setup. (after basic setup; dies, press, etc. my #1 extra is digital scale) Plus when I go to the range often I get to shoot other fellas rifles so they have a velocity value.
Start low and work up watching how flat the primers get. Stop when you get accuracy. A max load giving a 2 MOA group is less useful than and 1 MOA group thats 100 FPS slower.
Already got a chrono. My question with that is: Longer barrels can create higher velocities, therefore if my 26" barrel has a higher velocity out of the same bullet than a 23" barrel rifle how do I know if I am hot or not? Or is that possible?
Add about 50fps for every inch of barrel length over the test barrel. Gives an approximate idea.
I had the same experience with a mentor here in Edmonton, 2 of them actually. Prosper (where are ye, Brad?) on this forum and Doug at Wholesale (RIP Sir.). If you can find someone local to give you a bit of a hand DO IT.
I bought 3 manuals and read them cover to cover twice, including all the cartridge histories and minutae. That helped me a ton.
The Lyman manual is very good in all respects and probably gives the most detail. Hornady's pretty good, Speer I wouldn't buy again. There are other good manuals, I forget offhand what gets recommended around here.
Velocity alone is not an indicator or pressure,unless the velocity is way out of line for the load.As for barrel length,a 24" barrel with a tight chamber can produce as much or more velocity than a 26" barrel with a loose chamber,but it will normally be developing more chamber pressure to do so.
TargetNorth
Regular
- Location
- Southern Alberta
I've found that the minimum in one manual was producing pressure signs for me. Mind you, my velocity was showing at the maximum even though it was a minimum load.
I'd say hard bolt lift, flattened primers, bright spot on the base of the brass from it flowing into the extractor hole, and chrono velocities at the max listed in your manual.
I'd say hard bolt lift, flattened primers, bright spot on the base of the brass from it flowing into the extractor hole, and chrono velocities at the max listed in your manual.
- Location
- The Conservative part of Ontario
If you fire such a load, the rifle should fire form the case so that extraction should be normal.
That's been my experience anyway.
It's unlikely that your rifle will have tight headspace. Loose headspace is much, much more common.
If your load is hard to chamber, you likely f**ked up. Over crimping is the number one cause of hard chambering with jacketted rounds IMO. Too hard a crimp (with standard dies) slightly buckles the case near the shoulder, increasing it's diameter, and making it hard to chamber.
Test No.1 - is the load within the range provided in a current, major component manufacturer? If the answer is "No.", look no further.
Starting at the recommended start load, or 10% off the max if no start load is suggested, except for those powders where the powder manufacturer recommends not downloading a full 10%, watch the chronograph. As you increase powder charge, it is proper to expect the velocity will increase as well. If, before you get to the listed maximum, you blow a primer, have sticky bolt lift, or, most significantly, either a drop in velocity or a much smaller increase in velocity than you would predict based on previous incremental increases, STOP.
This of course assumes all cases were prepped identically between each reloading, such that changes in case capacity, neck length, god forbid neck encroachment of the throat, are not factors in the assessment of the load. Or, preferably, to avoid those issues, a nice fat bag of new brass was prepped, fireformed, and each load increment was loaded in some fraction of the total case count. YMMV
Starting at the recommended start load, or 10% off the max if no start load is suggested, except for those powders where the powder manufacturer recommends not downloading a full 10%, watch the chronograph. As you increase powder charge, it is proper to expect the velocity will increase as well. If, before you get to the listed maximum, you blow a primer, have sticky bolt lift, or, most significantly, either a drop in velocity or a much smaller increase in velocity than you would predict based on previous incremental increases, STOP.
This of course assumes all cases were prepped identically between each reloading, such that changes in case capacity, neck length, god forbid neck encroachment of the throat, are not factors in the assessment of the load. Or, preferably, to avoid those issues, a nice fat bag of new brass was prepped, fireformed, and each load increment was loaded in some fraction of the total case count. YMMV
Fire some factory ammo.
Take a 0-1 mic and measure the expansion 1/4-3/8 above the extractor groove 3 different place's and figure out the average and record it.
That will be your baseline on expansion.
When you make up a load make sure you measure this area.
If you are below it you should be O.K.
If your at it or above be careful!
Take a 0-1 mic and measure the expansion 1/4-3/8 above the extractor groove 3 different place's and figure out the average and record it.
That will be your baseline on expansion.
When you make up a load make sure you measure this area.
If you are below it you should be O.K.
If your at it or above be careful!
Every time I read one of these threads about how to detect excess pressure, I kick my butt for not saving the definitive article debunking all of these techniques, based on empirical testing by a very credible gun writer, and then pressure tested in White's Labs. If I had not lost it, I could cite the article, and doubters could look it up for themselves.
In sum, one of the better current gun scribes set out to load several popular cartridges, incrementally increasing powder charges, assessing each round for bolt lift, primer shape, case head expansion, and all the other "failsafe" techniques. One method tracked decently, and that was the lack of a predicted velocity increment to match the powder increment, but even that method was far from predictive or failsafe. And, while sudden expansion of case head diameter, or difficulty in bolt lift, or blown primers in previously normal cartridge/rifle combinations were all indicative of excess pressure, the scary part was just how excessive the pressure was before those indicators presented.
Some loads which still did not exhibit any traditional pressure signs, White's Lab's refused to test, as they were incrementally larger charges than loads which, when tested in industry standard pressure barrels, were unsafe. In modern bottleneck cartridges, it was not unusual to see pressures ten or twenty thousand psi (or CUP, or whatever the SAMMI unit of the day is ) over standard without visible signs on the case.
Now, some of those posting here will say "See, in my rifle, since there are no signs, I am safe at X load." But the lesson to take a way is, even if SAMMI and American design engineers put in a safety margin of 100%, or 150%, you keep beating away at a bolt and chamber at 150% of design standard, and you will hasten failure. Failure may be catastrophic when playing at 80 or 90 thousand psi.
The lesson the gun writer took away, (and remember he is a guy who makes his living yarning about how fast he got his most recent most favorite deerslayer to spit the latest in magic bullets) was, NEVER EXCEED BOOK.
In sum, one of the better current gun scribes set out to load several popular cartridges, incrementally increasing powder charges, assessing each round for bolt lift, primer shape, case head expansion, and all the other "failsafe" techniques. One method tracked decently, and that was the lack of a predicted velocity increment to match the powder increment, but even that method was far from predictive or failsafe. And, while sudden expansion of case head diameter, or difficulty in bolt lift, or blown primers in previously normal cartridge/rifle combinations were all indicative of excess pressure, the scary part was just how excessive the pressure was before those indicators presented.
Some loads which still did not exhibit any traditional pressure signs, White's Lab's refused to test, as they were incrementally larger charges than loads which, when tested in industry standard pressure barrels, were unsafe. In modern bottleneck cartridges, it was not unusual to see pressures ten or twenty thousand psi (or CUP, or whatever the SAMMI unit of the day is ) over standard without visible signs on the case.
Now, some of those posting here will say "See, in my rifle, since there are no signs, I am safe at X load." But the lesson to take a way is, even if SAMMI and American design engineers put in a safety margin of 100%, or 150%, you keep beating away at a bolt and chamber at 150% of design standard, and you will hasten failure. Failure may be catastrophic when playing at 80 or 90 thousand psi.
The lesson the gun writer took away, (and remember he is a guy who makes his living yarning about how fast he got his most recent most favorite deerslayer to spit the latest in magic bullets) was, NEVER EXCEED BOOK.
