Went out to test some new loads in my 280 tang m77. Hit and 15mph winds. Tried some rl-19 with some sst, eldx, gmx. 2.7moa would be the best I did. Then again my shooting platform wasn’t super solid(prome with no back support). My scope is a 3-9x. Tried different coals. The longer gmx load seemed to do best, but they are a fraction too long for my magazine. Only good news I learned. I got in a hurry and just shot off a bunch of rounds while my barrel was too hot to touch on a different target. Didn’t seem to affect the accuracy at all(gun is cryno treated, I’d that does anything.

Just figured I’d vent a bit. I have to drive 1.5 hours to shoot my rifle. And today’s 5 hour trip gave me very little useful info. This gun was owned by a decently known gunsmith, he definitely modded the rifle. I have some of his load data.

In my opinion it's like building a house, get the foundation right and solid. When you are evaluating loads and or rifle, you need the best conditions and rock solid rest...otherwise you are just burning ammo. I recently had a chance to shoot long range off of a portable bench made from just one sheet of plywood...I was impressed, it was as solid as my bench which probably weighs 250 pounds of timbers and lag bolts. The kid said he got the plans off you tube. His bags were the legs from worn denim work pants.
And this is just opinion...but I wouldn't get too worked up chasing the lands until you can see what your rifle is doing with suggested, proven loads that have worked in a number of rifles. John Barsness lists some universal loads for most popular calibers in his books, research that. Good luck.

Mono bullets can be picky.

In addition to multiple OAL, it's also prudent to load multiple powders behind them, especially when the range is a long ways from home.

But you did learn something. Your gun doesn't like GMX's with RL-19.

My gun does like 139gn interlocks with imr4350. I have some mrp powder(which shot like crap with partitions). Havnt used it since. Also have some h4831 I tried with 139gr interlocks. It didn’t like that powder nearly as much as the 4350

I'd move, first off.

SST suck ass, GMX, about the same. LUCK

1) Make sure the bore is clean
2) Make sure all all things are tight on the mounts,rings,action screws etc
3) Shoot from the same position using the same technique everytime all the time.
4) Select 1 load and stick with it, don't change this variable, resist the temptation
5) Practice, practice, practice!!! As you develop you will be able to out shoot your load/gun combination. Then start tweaking the variables one at a time and documenting the changes.
6) Don't get discouraged the starting point is 2.7 MOA, it's a learning curve thing. Enjoy the process.

Got a dumb question I just thought of. Can grass majorly affect a bullets flight path. I was laying down while shooting. And with it being summer there was longer grass. I avoided as well as I could but there was deffinetly some grass 5-10 feet infront of the barrel.

I've got a 90 minute drive to my shooting range, too. Due to the long drive, I work hard to maximize each shooting session: Rock solid rest. Nothing in front of the barrel. Shoot slow so the barrel doesn't over heat. Clean the bore when switching bullets or powders. Make sure everything on the rifle is properly assembled/torqued/Loctited. Do some research so I am starting off with powder/bullet combinations that have a reputation for producing good results. Bring multiple rifles to test. Take careful and complete notes.

Yes,

Shooting through grass can affect your groups.

Believe it or not, prone is one of the positions that is very much affected by technique. Consistency of holding the rifle and positioning is critical. That's why the vast majority of shooting to test accuracy is done off of a solid bench. If you need to, build yourself a portable bench.

A great shooting rifle will not automatically shoot great groups unless you can hold it very steady.Having a good set up helps you hold steady.This is what I use.

I have one of those front stands. Mines a bit beefier than that one. I just need to get a rear one and actually build a bench I can take with.

The rear support makes a huge difference.

Agree when it's a 280rem. cartridge but if you're shooting a BRUSH BUCKING cartridge limbs/logs/trees won't change the coarse of the bullet . Any misses are ''on you'' ………..

Doing load development in windy conditions without a good rest is like heading out sled riding when there's no snow .

There are NO cartridges that "buck brushes" and not change coarse! None!!!! The term brush buster is completely useless and should be avoided completely.

The closer to the muzzle a bullet touches anything, the more the deflection is possible.

Sounds like you have inaccuracy factors all stacking upon one another.

As one member here likes to say, “start at the beginning” which is a good stable and repeatable foundation and work up from there.

Any obstruction between the muzzle and the target can cause issues but as has been said the closer to the muzzle it is the worse the potential issue.

This is good advice. What was the temperature during your shooting session? Anything over 80 with RL 19 can be problematic IME. I had an issue with it in 30-06 (same case) on a Florida hunt and was soured by it quite a while ago. Storing ammo in the sun can cause issues as well. Have you read any of MD's gun gack books? Lots of good info there.

The temperature sensitivity wont reveal itself without a chronograph

Good luck and shoot straight y'all.

My immediate thought was this post was a joke from the get-go. A second and third reading did not shake the thought....

Yup another joined Aug 2020

You can believe that if you want.

It was 90+ degrees. I’ve heard rl-19 is temp sensitive. But I’ve also read that people exaggerate the sensitivity a bit.

Holy chidt are you mistaken.

Yeah, hes just trolling.

What, you've never shot prone without back support?

Don't listen to Dixie Rebel or bsa1917hunt - listen to me and get yourself a 45-70 brush bucking rifle .
I shoot a 444marlin w/300gr. bullets through anything - limbs brush , hail storm once hail balls big as softball I could see them exploding as the bullet tracked perfectly to the bullseye .
1/2'' groups all day long if I do my part .

I believe that RL 19 and 22 are about the same at least that is what my experience indicates. Here's a list which indicates that 19 is a little more temperature sensitive than 22.

I'm surprised to see RL15 with a high number I thought it was pretty good. From what I gather powder and cartridges can vary. Some powders will work fine with this cartridge and not so with that one.

https://www.longrangehunting.com/attachments/tempsens-jpg.207726/

Good luck and shoot straight y'all