Triage time for the 280AI

muleman · Jun 17, 2015

Last time at the range my Ackley seemed to freak out. A tried and true load opened up by an inch on several groups and another load that I had verified and was trying to improve on with an OAL regression went into shotgun mode. Here is what I've checked and ruled out. Rings and bases tight. Action screws torqued to their standard 55"lbs. Barrel was dirty but not overly fouled. Scope is tracking correctly. Barrel crown appears normal(no burrs) and had a carbon pattern that was near perfect. Trigger is normal and firing pin and spring are functioning normally. Brass is correct length and has no marks, bulges or donuts to indicate any problems.
What I did find was a small piece of bedding compound that was in the action screw hole threads had come loose and ended up in the lug area. This explains the slightly increased bolt closing effort I experienced. The bolt closes normally now. I had a bunch of ammo that I demilled from that session because I hit pressure really early with some RL26 150gr ABLR loads and some others with 7828SSC that were very inaccurate. I had a load that I verified three times and shot at 3/4"-1". I started a OAL regression to see if I could tighten up the 2 in and 1 out syndrome but the original load wouldn't shoot 4"! I used a RCBS bullet puller die and remeasured the powder charges and checked to see if the brass was in spec. It was and the charges were all within .1 gr of what it should have been. I weighed all the bullets. They were all 149 to 151grs. Then I measured them with the comparator............Hmmmmm. I measured base of bearing to tip and ogive to base. The new bullets were all within .001" on both measurements. The pulled bullets were up to .020" shorter shank base to tip and up to .010" shorter ogive to base. Some of the pulled bullets showed no variance. My first thought was that the collet puller was damaging the bullets. On further examination of the collet puller I realized it wasn't the culprit. The collet grabs the bullet just above the case and squeezes the bullet. This couldn't cause the bullet to shorten base of bearing to tip but might effect the ogive to base. There are no marks or dents in the bullets just some rub marks where the neck of the case was. My Hypothesis is that these ABLRs are very soft and that they might be damaged when seating them. I use a set of competition Hornady dies.
What do you all think?

Scott

nvbroncrider · Jun 18, 2015

Well Scotty had some red tipped 160 AB he work up a load with then got some white ones that was very slightly different and they went awry on him. Might be the same deal. Unless your using the same lot? Have you shot it since you found the epoxy? If not try again.

SJB358 · Jun 18, 2015

Jake brings up a valid point about the bullets Scott. My Mashburn and 7mm WSM require two entirely different seating depth between the old red tipped 160 ABs and the newer white tipped 160's. The WSM requires them to be shot at 2.950" and the white ones won't shoot for beans until they are down around 2.850.

Don't rule out a different lot of bullets throwing a wrench in your works.

DrMike · Jun 18, 2015

Each time a new lot of any component is introduced, the potential for significant variation is introduced. It has happened for me, just as Scotty states, and it has happened on multiple occasions. I cannot anticipate that a load will work consistently when any single lot is changed. Other than that, you're back to examining the rifle/scope. And it sounds as if you've thoroughly examined that possibility.

muleman · Jun 18, 2015

Thanks for the input guys. I checked the bullets and they are all from the same box. I'll try shooting the gun again with some other verified loads and see if it goes back to it's old self. Then I'll load up the ABLRs again and checking each bullet before I load it.

Scott