I posted this in "Reloading" first, but this crowd may be better able to help me, as it could be something peculiar to reloading for the Lott.

Additionally, I'm getting the same difficult lift with 80 gr. of IMR-4320. Furthermore, the bolt lift doesn't seem worse with 83 gr. of IMR-4320. Hence my belief that it's something else. (I would NOT have fired the heavier loads, but 83 gr. gave me no trouble in the past. I've fired roughly 100 of those loads.)

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OK, I know the "usual" suspect: high pressure. But the load I'm shooting (.458 Lott, 500 gr. Hornady Interlock, 80 gr. H-4895) is basically a starting load, and it's one that gave me no trouble previously. And it's from the same can of powder.

I have a Win M-70, custom built as a .458 Lott. I'm using BeLL brass, and I'm loading the cases with .458 Win Mag dies. I'm having the bolt lift problem with brand new cases, as well as 2-5 times reloaded cases.

The "difficulty" is raising the bolt handle the second half of the way up. It moves about halfway just fine, then gets difficult. Cases and primers look normal, and the velocity is 2245-- an expected level of performance with a lighter load.

I'm doubting that it's a pressure problem. So my question for the assembled experts: What other causes are there for this bolt lift problem? I've never experienced this before, and I have (with other guns) run quite heavy loads.

Or does it sound like a pressure problem?

Pertinax, the perplexed

Thick necks???? Check the outside diameter of the empty cases at the neck and then check the ourside diameter of a loaded round. You need a certain amount of leeway.

Bill, I think you are mostly right, but I bet it's over long cases. I don't have all the data (or energy to dig it out right now) but some lott chambers are bitchy about case length.
jeffe

Are there any extractor marks on the brass?

Has this brass been fired before, if so were there any issues then?

SRS

Another thing to have checked, esp. if this was a used receiver, is the bolt lug seat. It may be pounded back, and actually be trying to shove the spent cartridge further into the chamber during the bolt lift cycle.

I would consider investing in a set of lott dies.Standard 458 Win dies will not re-size the base and belt area enough allow trouble free loading after the brass expands and begins to stiffen up. I use a neck bushing die on my brass but still resize the base area after each shot to insure trouble free operation. I use a 5 die set up to prevent having an undersized case at the seated bullet's base.In short the case fills the chamber with better bullet alignment and this pays off in better accuracy. With our chamber specs 80 grs of H-4895 is often a max load with a FMJ and could hadly be considered "a starting load". Most Bell brass is 2.780-2.785 out of the bag and if the reamer was to spec the cases would not be to long for quite some time. You may have one lug seat inside the action to shallow or to high which could cause the fired round to expand in lenght just long enough to retard the primary extraction. In otherwords as you open the bolt you are in effect re-sizing the case as you operate the bolt, that's a long shot from way out in left field, but I did see this once when the lug seats had been machined on a reverse helix. I would spend the money on a set of proper dies first, resize and trim all the case's and start fresh.