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.

Pertinax,

You say the problem exists with new cases so that eliminates tired brass, unless the Bell brass is shit to start with.

You also say that the bolt lift problem occurs at 80 grains but also feels the same at 83 grains.

We know that under normal circumstances if bolt lift was difficult with 80 grains of anything in any caliber and was because of pressure, then at 83 grains of any thing in any caliber we would definitly be looking at loose primer pockets, ejector marks and other signs.

So it would appear to be reasonable to say that the pressure with 80 grains is OK.

Since it is happening with new brass not only can we eliminate tired brass (again assuming the brass is not shit to start with) but also sizing problems, case lenght problems.

The general thrust of your post is that none of this use to happen with this rifle and these loads.

One thing we do know is that since it happens on the last half of the bolt lift, the resistance to the bolt lift is either due to the case being more difficult than normal to pull back from the chamber or there has been some problem develop with the extraction cam on your action.

Since your pressures appear to be OK and it happens with new brass and the problem was not there before, then either some problem has developed with:

1) The chamber; or

2) The extraction cam; or

By the way, is the new brass you are using from your previous supplies, where there was no problem, or is it from new brass you have purchased in recent times.

Mike

Here's another angle to look at, Your action threads may be slightly off center or the bolt face may be slightly undersized or both.Did your Lott begin life as a 30/06? If you have no problems in chambering a round made up with a new case and difficulty in chambering fired cases this is another place to look. Shaved brass deposits in the recoil lug area would suggest this.I have had to open up the bolt face to .540-.542 on some M-70 bolts. I'm still banking on the dies being the root of the problem.

This forum is the best!

OK, to answer some questions asked of me:

1.) The cases are not too long. I trim them back to 2.750 before loading the first time, so that the Hornady bullets will crimp into the cannelure and still be under the 3.6" magazine limit.

2.) I don't think the case necks are too thick, since this problem appeared suddenly, and now occurs with fresh brass, as well as two and three times loaded brass.

3.) No extractor marks on the brass, and the cases were fine before. I'm still using the same batch of brass I bought when I first got the gun. (So the problem didn't appear when I happened upon a new box/batch/lot of brass.)

4.) Bolt lug seat, and other lug and extractor problems: I'll have to take the gun into my 'smith. I just want to rule out high pressure first!

5.) Mr. Echols: The gun did indeed start life as a .30-06. I'm left-handed, and it was available, so I used it as the starting point. I'm not having problems chambering either loaded rounds or fired cases. The fired cases also extract fine. I do have a set of Lott dies that I received a couple of weeks back (Hornady). But I haven't tried them yet.

So, I believe, based on the wisdom of the assembled, that I will try loading up some cases with the Lott dies before I take the gun in to my 'smith. Meanwhile, I'll look and see if I can find any brass shavings anywhere.

Thanks, everyone! I'll report back as this progresses-- in case anyone is interested, and to get my post count up...



Pertinax

Frighteningly so!

OK, so I cleaned the heck out of the gun, especially in the locking lug area, and the situation is markedly better. But it's still not as smooth as I would like-- or as easy as it used to be.

I tried real Hornady .458 Lott dies, and that didn't make a difference. I also tried a couple of more brand new cases (trimmed to 2.750), and that didn't help either.

And I fired a few cartridges loaded by Superior Ammo. They exhibit the same lift problem. So I'm doubting that it's me generating excessive pressure.

I'm taking it back to the 'smith for a checkup.

Pertinax

Let me get this straight, when you chamber a virgin round or un-chamber and extract an unfired round there is no problem. It is only after the round goes off that you have the problem with bolt lift or on re-loaded rounds.
Also this became a problem after the rifle had been shot for some period of time? Is there any gauling on the rear of one or both of the recoil lugs? Can you tell if the 42 degree cone slope on the bolt nose is in contact with the cone breech in any way? use a marks all pen on the this slope and then chamber one of these problem rounds and lift and close the bolt a number of times then remove the round to see if there is contact from the bolt nose on the cone breech.

Check the belt of the cartridge for major expansion!. If it's greater than .003 from the stock brass, this may be what is causing the difficult bolt lift. I've seen exactly this same problem when I pushed a 460 WBY a bit too far. You will see excessive belt expansion and sticky bolt lift well before you see case head marks particularily on a M-70 action. Depending on the reamer used to make your Lott, the belt recess might also be on the tight side. -Rob

Mr. Echols:

You are correct: 1.) I have no problem un-chambering any unfired round. 2.) I have no problem unchambering a fired and previously extracted case. 3.) I only have problems after the round is fired. It will go right back in, and come out easily.

And yes, this only became a problem after around 100-120 rounds through the gun.

I'll take a look for the things you mentioned tomorrow. Thanks for the suggestions!

Robgunbuilder: I'm not going to get a chance to measure it tonight, but I'll do it tomorrow. But I don't think that's it, as the fired cases go right back into the chamber and extract normally. I am assuming an expanded case belt would bind up if re-chambered, but perhaps I'm wrong about that.

Thanks guys.

Pertinax