weird groups any thoughts?

[Elk868]

hello all
of course it would be good to have more info . but mainly this Looks like wrong powder . i have had Close same Groups with 8x68S . then i just got me a slower and a faster powder .
at least i got very good results with hodgon 1000 .
wolverin338

 

[tweek1142]

I have a Remington BDL 30-06 that did this exact same thing. With 165-180 grain bullets and 4350, 4831. It came out to be powder/bullet selection. Once I dropped down to a 150 with a faster powder (varget) my problems went away. It wasn't the direction I wanted to go but PA white tails don't seem to mind and the rifle now shoots 1/2 moa. I use this as my woods hunting rig and it's accurate enough for me to make slick shots in tight spots between trees and through openings in saplings when needed. You can also try a flat base bullet to see if it shoots any better.

 

[Elk868]

@ teek1142 : i planed to use barnes TSX 180 grains for my 8x68S . tests gave me always two lucky spots - either 2 bullets up and 3 down or other way round . so i tryed faster powders and the result was same . sometimes bit more space between those two lucky spots sometimes less . then i stepped back to hodgon 1000 and suddenly i got 5 shot Groups size 0.1-0.2"
so it might not be necessarily the bullet/powder Combo - maybe it is just to fast or too slow for .
wolverin338

 

[Mikecr]

I've had two guns that double grouped. One shot great until one day it changed, the other double grouped right off the bat.

I eventually figured out the early offender(a new custom) with a scope swap. NF identified the problem as a lens bedding issue. They fixed it free, 2-day turnaround, no more double grouping. This is where it pays off to hold a reference scope(known good) in the safe.

The problem with the gun that changed from great to double grouping was very difficult to find.
It turned out the firing pin had started slipping under cocking piece set-screw.
The pin spring would push the pin to a forward location, and firing would intermittently move the pin to a second back location, where it occasionally stuck -until freeing up with further shooting.. The gun always fired ok, and both groupings were reasonably good(but not together).
Took 2mos to figure this out as there was no way to physically see the unknown cause, even with disassemble. I took many actions mentioned here & questioned/tested any stretch of recent changes,, no affect. Then one day I had a misfire. Within a few rounds, a second misfire. Now I knew for sure that I had a striking issue. I examined the hardened pin under magnification/angled lighting and found slight evidence of slipping under set-screw.
Now all I had to do was put the pin back where it should be and better secure it. Where should it be? Uh Oh...I didn't know for sure..
I had to do firing pin testing just like I do seating testing, and it turned out there was one setting that was better than all others. With this, it turned out a blessing, as I gained a solid 1/8moa over previous best performance. Locked it down, and the gun has shot fantastic ever since.
This is a Cooper M21 in 223.
I learned here that there is so much more to learn. That it's possible the abstract behind a gun favoring one primer over another -is firing pin setting, or spring, drag, trigger sear position, lube, temps, cocking piece, pin diameter, headspace,, anything affecting striking. That we can have any marginal combination of issues here that are not apparent, as every primer still fires, and their indentation is still fine. Those misfires I eventually had? Normal indentation!

Today I have a revolver that double groups due to a headspace issue with certain ammo. It always fires, but if I bring the gun from upward pointing down to target, -vs- downward pointing up to target, Jekyll and Hyde.
I've removed load density/powder shift from question by manually tweaking headspace from level. Same results. It's a delta in primer striking.

 

[Elk868]

i can imagine how this is for you Mikecr. but isn t that the way we learn and a part of the fun ?
ok can be sometimes really frustrating .
but i m sure you will figure why this happens . Is it concentric ?
and it s good to read about - lessons for free
as well it s hard for me sometimes because english isn t my native
but thanks for sharing with us

 

[YOTA]

ive been too busy to work on the gun much but i did get the stock and action separated. there are 4 screws that hold the stock on and all 4 where really torqued down hard. i could see the barrel relax as i was unscrewing the for-end screw.it is glass bedded. the scope is brand new so after i shoot a few more rounds through it with the for-end screw loose or taken out all together then ill switch scopes. the double group thing wasn't happening when i first started shooting the gun so maybe it is the scope. i don't have much time to get it figured out because my son and i drew antelope tags that start on the 19th of September.

 

[LoneTraveler]

It could be the bedding or barrel contacting the forearm or a unproven scope may be causing this. Have you been using a proven lot of primers?? Shoot through a chronograph and log each shot by velocity and location on target. You may find you are getting different velocities because of bad primers and bullets of one speed going into one group and slower shots going into the other group. Had a 338 WM doing this and the chronograph proved it was the primers. Changed the primers and the gun went back to one group. Check the bolt and firing pin and firing pin spring is there any dirt or junk in the firing pin way. Do you have good main spring tension soft firing pin hits can cause another night mare problem. Good Luck in finding the solution so you can get ready for your hunt.

 

[red dawg]

Pretty sure its your bedding job or your powder selection or both, your action screws should not have been that tight if the bedding is done correctly

 

[red dawg]

If you have a tipton cleaning device where you can set your gun on it so that there is no weight on your stock, you can take a piece of paper or dollar bill and slide it between the barrel and the stock to see if your barrel is making contact with your stock, or maybe take stock off the action and look at your fore end of the stock to see if it has a shinny spot from contact with the barrel

 

[YOTA]

i loaded 8 more shells 4 at 67.8 and 4 at 68 grains the 67.8 only had one flyer at 3oclock about an inch away from the other 3 that wee all touching but i got a deep ring around the belt. it looked like the case head was about to separate so i didnt shoot the 68 grain load. im going to load some 67.5 grain loads and take the forarm screw out ( this gun has 4 action screws) then tighten it by two inch pounds every string and see if that fixes it. ive given up trying to get it read for antelope season. my son will have to shoot his 280 ai its all dialed in.

 

[LoneTraveler]

I looked at your target, and turned computer and studied the target. My thought is the problem is somewhere in the primers or firing pin. Dirt in the bolt, or the rifle being a PRE 1964 Model 70 Winchester. Unless it has the firing pin spring replaced. It has set in a gun rack maybe cocked and time has taken the tension out of the Firing pin spring. I inherited a 722 Rem. from my father that was over 50 years old, and had problems, The cure was a new main spring and all is well. Check the edge of the firing pin crater in the primer with the edge of your finger nail. If you have a sharp shear where the firing pin is getting moved back a few thousands into the bolt, The firing pin spring does not have enough force to crush the primer the same every time. Good Luck.

 

[YOTA]

i took my torque wrench and tightened the action screws at 60 inch pounds except the forearm one i put that at 2 then i loaded up rounds with the reloader 25 of 67.6, 67.8 and 68 grains. the hotter the load the better the group i got but a ring formed right in front of the belt and got more pronounced, i only shot one round of 68. so then i switched to reloader 22 and the double groups went away but still 1.5 inches the hotter the load the better the group. i started to put strips of aluminum foil under the recoil lug to raise the barrel so it wouldn't contact the stock but thought id ask if anyone has tried this.

 

[livtoohunt]

My money is going to bet the scope and or mount. I had a 300 WM did the same, come to find out I dented the tube.