Why do my groups open up over time?
- Thread starter Hawkertactical
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- 308 help load development varget
No, Varget isn't that temperature sensitive.
You'll have to provide a lot more information for the guys here to help diagnose your problem. It could be anything from carbon buildup in the chamber, something you're doing, something wrong with the scope, action screws, the price of rice in China is going up, maybe you were on the wrong node and a change made a difference, Epstein didn't kill himself, what about lot changes between primer or bullet or powder,
You'll have to provide a lot more information for the guys here to help diagnose your problem. It could be anything from carbon buildup in the chamber, something you're doing, something wrong with the scope, action screws, the price of rice in China is going up, maybe you were on the wrong node and a change made a difference, Epstein didn't kill himself, what about lot changes between primer or bullet or powder,
Well it has been a while since I've cleaned my rifle, but it doesn't get shot very much, and yes the primer lots did change several times. Scope and mounts are all good and still torqued to spec
Clean your barrel and start over. If you’re using a nylon brush, get a bronze brush and run it only in one direction. Clean it real good.
What is your load? What brass? What is your coal? How close to the lands?
What is your load? What brass? What is your coal? How close to the lands?
I’m not on the level of allot of guys on here, but (and I don’t mean this in a dick way). I would look to improve the Indian first before the bow. I know if I’m shooting for groups my early groups are always better than my last, and that’s all me.
If is the Howa in your profile pic check that your brake is not loose. I had a similar issue with an A2 flash hider and an Accuwasher. Didn't know it was loose until I touched it and it was a tiny amount of movement.
Going from groups touching to 3", any number of things could be involved. Without a lot more details, it's a blind guess as to what might be going on. Temperature alone is not likely the problem. In the last 6 months I've been shooting my .308 almost exclusively in the Phoenix area as well and so I know our shooting can be in quite an extreme range of temps. But, unless your leaving your cartridges sit in the sun, your Varget isn't likely to react that way.
It very well could be a combination of things, like the barrel getting too dirty and the lands has moved to a point where you're loads are no longer in your accuracy node. I've found that I need to do at least a light cleaning of my barrel after about 250 rounds as my groups "start" to open up there and after a light cleaning, my groups come back to touching. But, I've not seen my groups open up to that extreme.
Most
All test groups are shot from sand bags with rear bag, plus 3 or so dry firing pulls between each round
Good to know, I was shooting some nasty Tula ammo just for shits and giggles so I am sure those dirtied her up, looks like cleaning is one of the issues over all
I had this exact thing happen to me last weekend. Only difference between the previous range trip where I printed a .477" 5 shot with 5.50 SD and that one was groups were pushing 1.5 MOA. 7th shot felt a vibration. Tightened the break, and one ragged hole.
I never doubted your effort. I‘ve just spent allot of time and money over the years chasing accuracy and most of the time it came down to me assuming I was using a quality rifle. That may not be the case with you, but just a thought.
Just an FYI: Varget tends to be a bit dirty compared some others. Add that to such a light load like you're using where about 7% of the Varget is not being burnt (assuming you have a 20" barrel) leads to having a barrel that'll dirty up in no time.
How bout the coal? How did you arrive at this coal? What kind of load development did you do?
Lol! For some reason I read coal as like the stuff you pull out of the ground. The COAL is just what the books stated, 2.80 inches, i will eventually load to what my chamber wants but has yet to happen
That could explain why your groups increased. If you choose a book coal and work up a load you might get some nice groups today that will fall apart tomorrow due to environmental changes. Working up a good load requires testing which range of coals will give you stable accuracy no matter what the weather is like. Same goes for powder charges. You need a range of accurate powder charges and pick the middle.
I can't understand why people don't clean there rifles on a regular basis. It doesn't hurt your gun unless you do something stupid. I would scrub the hell out of it and try them again. Some barrels foul out with under a 100 rounds threw them and some don't.
What kind of speeds are you getting with that load. Seems like a very light load.
What kind of speeds are you getting with that load. Seems like a very light load.
I live in Mesa AZ. My groups open up after 20 rounds due to barrel heating up with a M40 contour Bartle in my 6.5x47 Lapua. Vs using a #7 contour Shilen on my .308 which will take the heat. I know there's a ton of variables but it's so hot I spend time on my patio in the am with trigger time.
Unless you damaged the crown somehow, assuming your touching load hasn't changed scope, rings, brake or just fouled up real bad.
Usually your groups open up after time on any barrell. After 100 rounds i check my bullet seating depth due to throat erosion. Also heat will open them some as well.
Check your scope and the mount hardware. You could have broke the mechanism in the scope and now it's just flopping around and randomly changing your POA with every jolt.
Firstly clean your barrel properly. Secondly check everything is tight. Thirdly have you changed anything in your load. Are your bullets, powder and primers all the same batch numbers loaded in the same cases. If not your old load is irrelevant. Have you checked your cbto measurement. I once had this issue and it took me months to figure it out. Turned out my seating die had come loose and I was running a 100 thou jump instead of a 10 thou jam and it didn't like it.
That is an extremely low charge weight. The low node with Varget is typically around 43 grains. I suspect you are not getting consistent ignition and burn, along with a dirty barrel. Where did you get your load data from.?
