Advice needed!!!

[7mm08mo]

I have a .28 Nosler in the 48 Nosler Liberty, I have owned it since January or Feburary and had a very accurate load worked up for the gun. I always test several loads and pick the most accurate then chrony them so I am not tempted to pick the fastest as I like accuracy. My problem is I am now shooting my 300 yard target with a 100 yard zero and striking right where I aim. Group size is not an issue my groups are tight, it is just shooting high. I have checked all the mounts on the gun and scope and they are fine, like I stated group size is not a problem just shooting bad high and creating a sticky bolt sometimes. I had chalked it up to high temps here when I was shooting some mornings it was 75 with 80% humidity, but shot on Wednesday and it was a balmy 57 degrees and had the same problem. The only thing that has changed it my lot of powder, I was using bottle that I still had from my .300 rum and when it ran out a I picked a pound up at a local shop. I use retumbo powder. That is the only thing that has changed is the lots of powder. I am thinking it was bad and bought another pound from a different place today and going to load up three rounds tonight and go to range tomorrow and see what happens. Anybody have and experience like this? If the powder doesn't fix it I do not know what to look at. My load is 160 grain NAB over 83 grains of Retumbo and cci LRM primers and when I developed it, my 5 shot average was 3300 fps with no more than 40 fps spread from greatest to least.

 

[MThuntr]

Lot to Lot variability combined with high temps could be the culprit. If you like Retumbo buy an 8lb tub and work up a load again is one option. Here's an interesting issue Nosler's starting data is at Hodgdon's max for 160 grain bullets.

Random thoughts...Is this new brass or oncefired? Are you full length sizing or neck sizing? How's the bolt close on the ammo before you fire it? Are you seating the primers deep enough?

 

[7mm08mo]

All of the brass is at least once fired but through my rifle. It was ammo I bought when I bought the gun. I am full length resizing, and the bolt closes well, and as far as the primers they are as deep as I can get them they are not flush or sticking out but a little sunken in with the brass. It is interesting I checked that out when I started working up my load and all has went well until now, actually this summer.

 

[cahunter805]

Lot to lot variations is very common. Retumbo is known to have some big swings. You need to chrony your load. In my opinion your probably over pressure with the new lot. Back down a little like maybe a grain or 2 and rework up your load over your chrony.

 

[Doublecluck]

Mix all the retumbo you have togeather and load up the same load. If it shoots good groups, load thru the rest of the batch and re-adjust your zero and go hunt. If not than start over. That's what I did and I still have 10 fingers...

 

[Millsworks]

Powder lot variation sounds most likely. But, I have a friend that saw a similar problem in a .300 win mag years ago. It turned out that he had never trimmed his brass and there was a pinch being created in the throat, squeezing the neck around the bullet, and raising pressure.
You probably trim your brass when needed I'm guessing.

 

[Don Fischer]

Sounds like pressure to me. Back off the load a bit and do it again. 100yd zero I couldn't handle. With that cartridge you should be able to go 3" high at a hundred and be able to hold dead on out to or beyond 300yds. My chronograph has a computer in it. I feed a bit of data and feed in for max point blank range with an 8" target. I hold dead on for every thing is shoot. But get the pressure down a bit. Look at your bolt face, high pressure can start flame burning there, be real noticeable. Around the firing pin hole same size as the primer. it is possible it could be from something else but I'd take the most obvious first and work through it. drop down a couple grains and see if you still get the sticky bolt. You don't, you likely have your problem.

 

[Curvebow]

I've had similar things happen when loading for 253 and 284 Hunt Talk when changing to a new pound of powder. As always suggested, back down the charge to get rid of bolt stickiness. Then resign to your gun as long as accuracy remains. Then go it more pounds of powder st the same place you got it. Be sure it's the same lot number!

Good luck....

 

[7mm08mo]

Got it figured out. Backed off a grain of powder and had the correct velocity and impact point. Thanks for the advice.