Trying to Understand the Why on Load Data

buck460XVR said:
I have a 1917 Eddystone. Seems as long as the bullets weights are the same, it will put virtually any good production ammo in the same 1" circle @ 100 yards. Been that way since the day I got it back in 1970. Barrel has been shortened, recrowned and original sights replaced with Williams. Was my primary deer rifle for 35 years until I quit hunting deer with a long gun completely and went with revolvers. Was like carrying a tree trunk around in the woods, but it never missed.
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My 1917 came from my father's passing. Being the only one in my family into firearms the way I am. I didn't do anything then clean it the first few years. As I started reloading, and took it the one day to double check my .308 mossberg for deer season I learned it shot an amazing group. I figured it would do well, just impressed as to how well. It is all original. I am wondering if it has foregrip pressure or bedding warp from time. The front site is almost perfect center. I think the armory would have been on point setting it
 
Chief TC said:
So I am working on developing a new load for my M1917 because I got a good deal on 500 of 180gr SMK factory seconds. These perform much differently than the Hornady 178 match bullets I currently use. My question is what are the factors behind the vast differences between these 2 bullets. I noticed the max charge on AA4350 was 55.9gr for the Hornady 178gr match bullet and 60.3gr max for the 180gr SIE SBT. Since the weight is almost exactly the same, then is it the angle of the ogive that dictates how much pressure the bullet can handle? Thanks.
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Overpressure events don't blow up bullets, they blow up guns...
 
Thanks everyone. Appreciate all the replies. Really helped me understand some things better about pressure, testing, various bullets, etc.

My M1917 is definitely one of my favorite rifles. It is a Winchester from 1918 that has the original receiver and barrel but has a few eddystone parts and was parkerized. It is a sub-moa shooter. I tried 150s and 168s and they did ok but tried Hornady 178 match and paired with aa4350 and achieved 1 moa at 330 yds with consistency. I got a good deal on 500 factory seconds 180gr sie sbt, so I need to develop a load for these guys. When I went to look at accurate and hogdon load data, I noticed how this bullet varied quite a bit from other types of 180s. This is what got my gears turning and trying to understand why. Thanks everyone.
 
OP- One thing I noticed you posted a couple of times was questioning if “the bullet” can handle the pressure.

The pressures you see listed in reloading guides for the bullets you listed are for the chamber pressures generated by the load that the gun has to contain when a cartridge is fired, not the pressure the bullet can withstand. If you exceed these pressures, and the gun can’t handle it, it will disassemble violently in your hands.

As the guys posted, there are lots of variables between two different bullet brands or types that cause differentials in powder charge weights to keep pressures within acceptable limits.

There are some bullets that have velocity maximums due to their construction, these Sierra pistol bullets have a 1,400 fps maximum speed for example, because they aren’t constructed to perform well at higher velocities then they were designed for. (They come apart or disintegrate, rather than penetrate and mushroom, for example). The XTP bullets have no velocity limit listed, so these I use in my .45 Colt rifle and leave the Sierras for handguns.

IMG_4343.jpeg

You also may run across long-for-caliber bullets that list a recommended twist rate for optimum stability. (These Barnes .264 127 gr bullets list a 1/8” or faster twist rate on the box. ) Anything slower will probably lead to inaccuracy or even a bullet tumbling in flight.

IMG_4344.jpeg

Just pointing out a bit of possible confusion in the earlier posts, trying to help out. :)

Stay safe.
 
Riomouse911 said:
OP- One thing I noticed you posted a couple of times was questioning if “the bullet” can handle the pressure.

The pressures you see listed in reloading guides for the bullets you listed are for the chamber pressures generated by the load that the gun has to contain when a cartridge is fired, not the pressure the bullet can withstand. If you exceed these pressures, and the gun can’t handle it, it will disassemble violently in your hands.

As the guys posted, there are lots of variables between two different bullet brands or types that cause differentials in powder charge weights to keep pressures within acceptable limits.

There are some bullets that have velocity maximums due to their construction, these Sierra pistol bullets have a 1,400 fps maximum speed for example, because they aren’t constructed to perform well at higher velocities then they were designed for. (They come apart or disintegrate, rather than penetrate and mushroom, for example). The XTP bullets have no velocity limit listed, so these I use in my .45 Colt rifle and leave the Sierras for handguns.

View attachment 1195681

You also may run across long-for-caliber bullets that list a recommended twist rate for optimum stability. (These Barnes .264 127 gr bullets list a 1/8” or faster twist rate on the box. ) Anything slower will probably lead to inaccuracy or even a bullet tumbling in flight.

View attachment 1195682

Just pointing out a bit of possible confusion in the earlier posts, trying to help out. :)

Stay safe.
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Many thanks. I totally get this now and I was doing a poor job of explaining myself and using the correct language. I already knew load data was discussing chamber pressure and exceeding it can blow up a gun. I thought maybe there was a pressure limit on different billets based on the load data and was not doing a good job of asking my questions. Appreciate all of you bearing with me and explaining it all.
 
Chief TC said:
Many thanks. I totally get this now and I was doing a poor job of explaining myself and using the correct language. I already knew load data was discussing chamber pressure and exceeding it can blow up a gun. I thought maybe there was a pressure limit on different billets based on the load data and was not doing a good job of asking my questions. Appreciate all of you bearing with me and explaining it all.
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Lots of bullets have speed limits, berry's and a lot of plated have speed limits. One can also over spin a bullet in a fast twist barrel... it wouldn't be any fun if there weren't multiple roads to failure. The best news is there are just as many to success!!!!
 
Chief TC said:
So I am working on developing a new load for my M1917 because I got a good deal on 500 of 180gr SMK factory seconds. These perform much differently than the Hornady 178 match bullets I currently use. My question is what are the factors behind the vast differences between these 2 bullets. I noticed the max charge on AA4350 was 55.9gr for the Hornady 178gr match bullet and 60.3gr max for the 180gr SIE SBT. Since the weight is almost exactly the same, then is it the angle of the ogive that dictates how much pressure the bullet can handle? Thanks.
Click to expand...
research the two bullets for jacket hardness/thickness
then, wet mark up a surface and roll each onto it, to get the length of bearing surface

if the two match up, they will act the same regarding internal ballistics, in ONE particular gun

the big difference is simply different companies and their position

there simply is NO specific reason other than that is what they post

I have often found, when researching, the SAME bullet/cartridge/powder combo with wildly varying charges from different companies
I believe this is due to MANY factors, not the least of which is the Lawyers on retainer, but also, EVERY gun is different
as is every cartridge capacity etc....

What I have often done, when starting with a different gun/bullet/powder...
I gather as many loads I can, Min/Max from EVERYWHERE
then compare them... and disregard the lowest/highest published
Then I take the average mean and make a note of that
then I go 10% (if powder appropriate) BELOW that, and check velocity, compare to published. This proofs the mean.
Then I take the mean/New max and go up 90% and that is MY max
Then I ladder loads and go from mean to MY max, checking for accuracy nodes, and work from them

I have found there is NEVER a good reason to load to max if you can find an accurate load between mean/max

Targets and Game NEVER know the difference
 
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