I loaded up some 300 rum ammo for my friend with a max load of retumbo and 200gr accubonds. It was once fired factory brass from his rifle. I screwed the dies down till it hit the piston and backed it off 1/4 turn. The ammo chambers just fine. At the range it's very accurate however on some cartridges the bolt opens just fine until the last 1/4 inch or so where it gets stiff. No pressure signs on the case or primer. Any ideas?

Also the rifle strings vertically. Groups at 200 yards were .4 inches wide and 1.4 high. This is for 5 shot groups.

Thanks

The lifting of the bolt handle has to break the cartridge case loose from the chamber and handle the compression of the main spring. When you say the last 1/4 inch or so, I presume you mean bolt rotation and not moving the bolt to the rear.

I don't shoot a RUM but often Remington extractors will peel a bit of brass from the case rim, and you can feel this as you finish rotating the bolt up.

With the recoil of this cartridge you could easily get 1.4" of vertical spread in the group just from bag technique on the bench: not getting the rifle in the same place, not using the same hold each time and not getting the same rifle motion on the bags during recoil.

jim

Thanks for the reply. So the stiff last 1/4 inch of the bolt rotation isn't a preasure sign? Can anything be done to fix it?

I think it can be, don't know anything about Rems but at that stage as Jim said most bolts are hitting a cam with the bolt handle against the action. This is the first pull back on the case, before the bolt can move directly back.
So if the case is too tight, so the bolt lift will be harder.
Best fix may be to reduce the loads abit.
I usually try putting the empty case back in the chamber when testing for mag loads, and if
a tight fit from FLS'ed brass I'm too hot.
May not hurt to lube up the bolt and bearing points.
JL.

I'd take that sticky last 1/4" of bolt rotation to be a hi-pressure sign.

It might not be...but I'd assume it was until I could prove otherwise.

It is not a pressure sign. The same load in new brass will not make the bolt stick.

I think it has something to do with brass memory and out-of-square bolt face.

You can avoid it by using a less than max charges. 5% below should do it.