Strange things happening in load development. Thoughts???

[Mikee36]

So recently I have been doing quite a bit of load developing for an LWRC REPR. The strange part, to me, is as the powder charge, velocities, and pressures increase, bullet impacts get lower. This doesn't make sense to me. And I've used three different bullets, two different powders, and shot at 100 and 200 yards. Still the results are always the same. As powder charge goes up, bullet impact goes down. I use a MagnetoSpeed chrony and as powder charges increase so do the velocities. Can someone please help me make sense of this? I'm not complaining, the gun shoots great. Short and long range. I am just confused. Thanks in advance.

Mikee

 

[RampedRaptor]

Barrel harmonics is the answer I do believe.

 

[Mad_Charlie]

Recoil starts at the instant the bullet starts moving, the instant the bullet starts moving, the muzzle starts to rise. The less time in the barrel, the less the muzzle rises.

Works for pistols too.

All things considered, standing position shots tend to impact a little higher than benched shots because the muzzle can rise easier.

 

[wilecoyote]

....macroscopic in .44mag revolvers: the less the speed,(at feebler .44spl. level), the higher the POI_
at full .44mag charges, and more even w.light bullets at high speeds, the POI will be lower_

 

[Mad_Charlie]

....macroscopic in .44mag revolvers: the less the speed,(at feebler .44spl. level), the higher the POI_
at full .44mag charges, and more even w.light bullets at high speeds, the POI will be lower_

Especially in .44 Mag revolvers!!

 

[Smokerroller]

I have a REPR 20 that I am doing some load development for. My load work up was done at 300 & 400 yards. At 300 the POI was the same as you described. At 400 the POI was as you would expect. Higher charges hitting higher. I'm curious what your loads you are coming up with are. I have come up with 44.2 grains of Varget, 178 Amax, and win brass. I'm still going to play with different primers and might try a couple other tweeks but that charge got me 2.3" at 400 yards. There was also a node at about 41 grains but it didn't do as well at 400.

 

[thrusty]

You're shooting the gun upside down...

It's harmonics...although, atypical. As long as you are seeing good, consistent, groups - go with it. That's another reason why your sights have up, down, left and right movements.

 

[Graham]

As velocity increases the bullets go faster.

 

[Dan Newberry]

....macroscopic in .44mag revolvers: the less the speed,(at feebler .44spl. level), the higher the POI_
at full .44mag charges, and more even w.light bullets at high speeds, the POI will be lower_

10-4 for sure... I had to speed the 240 grain LSWC's up so fast in my Ruger SuperBlackhawk they were wanting to lead the barrel before I got the impact low enough for a dead on hold at 25 yards.

So what you're seeing with your rifle isn't out of the ordinary at 100 yards, anyway.

Dan

 

[Mikee36]

Thanks guys. I figured it was barrel vibrations. Although what Mad_Charlie said makes sense too. Probly a combination of the two.
Smokeroller, I think I have found a good load for 168 grain SMKs... 42.2 grains of Varget in Lapua brass with GM210M primers. I am now working up loads for 175 SMKs. I am not too confident in my tests though. And I started showing signs of pressure at 44 grains of Varget and the groups weren't great. What are your velocities with that load?

 

[Smokerroller]

Mike, I don't have a chrono so I don't know what my speed is. My drop at 400 yards is almost 34", and using a couple ballistics programs my fps should be about 2509. Its not precise but it will do for now and I will continue truing as I move out further, until I get a chronograph. Why are you unsure about your tests? I also had a group at 400 that was about .6" vertically but was 6.6" wide. I am going to load up a grouping of that charge and see how they do again since I was shooting in some breeze. This load I am working up now is with A-maxs for hunting but my primary load will be with 175 SMKs as I have a lot of those stocked up. I also have some 165 SMKs and A-maxs but I will work on those later. What size groups and speed are you getting and what barrel are you shooting? I had no pressure signs all the way through 45.2 grains. My groups started opening up so I didn't go higher. All my reloads as low as 40.8 grains had flattened primers and nipples around the firing pin hole but that seems to not be uncommon for REPRs.

 

[stranded]

As velocity increases the bullets go faster.

Are you sure? Can I see the math? Sounds to good to be true.

 

[Mikee36]

Mike, I don't have a chrono so I don't know what my speed is. My drop at 400 yards is almost 34", and using a couple ballistics programs my fps should be about 2509. Its not precise but it will do for now and I will continue truing as I move out further, until I get a chronograph. Why are you unsure about your tests? I also had a group at 400 that was about .6" vertically but was 6.6" wide. I am going to load up a grouping of that charge and see how they do again since I was shooting in some breeze. This load I am working up now is with A-maxs for hunting but my primary load will be with 175 SMKs as I have a lot of those stocked up. I also have some 165 SMKs and A-maxs but I will work on those later. What size groups and speed are you getting and what barrel are you shooting? I had no pressure signs all the way through 45.2 grains. My groups started opening up so I didn't go higher. All my reloads as low as 40.8 grains had flattened primers and nipples around the firing pin hole but that seems to not be uncommon for REPRs.

Yeah I was surprised that almost all my loads had flattened primers and craters. I started to see ejector marks so that's when I stopped increasing charge. I'm unsure of my tests because I can't see any obvious nodes. My shooting with semi autos could use more practice and my velocities aren't as consistent as they should be (in my reloads and factory match grade ammo) so I'm a little worried there is something in the gun affecting pressures and velocities. My gun is identical to yours other than I have an ATACR not a USO

 

[Temp9]

As velocity increases the bullets go faster.

The speed will also increase as the bullets go faster, believe it or not.

 

[Smokerroller]

Mike, it might help you if you try your load work up at 300 if you can. 400 was a little long but gave me some good info in addition to the 300 yard line. Is your gas setting on N? Does the gas knob move freely? I only had 2 nodes from 40 up to 45 grains. There are two good articles you can find on here about doing a ladder test and an OCW test. The OCW test is by dan newberry who posted above and he has a link to it, and you will have to search for the ladder test article. Both were extremely informative.