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I am relatively new to reloading long range .308 and .338 Lapua.

I had a tough time extracting shells after firing and found it was because of lube on the reloaded cartridges. After cleaning cartridges and chamber, shells extracted easily.

Being a curious engineer type, does anyone have a technical explanation as to why/how lube causes a shell to be difficult to extract?

Thanks.
 

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I found this somewhere, kinda makes sense but the experienced guys here can probably explain it better:

NHgunNut
make sure the cases are dry and clean on outside with no lube when you shoot them. A lubed case wont "stick" to the chamber walls like it is designed to and it therefore acts like a 50,000 PSI wedge pushing against your boltface, temporarily stretching your action, and when your action and chamber contract back to normal size, is pushing on the case. I can envision whats happening, and ive seen where making sure your loads are clean of lube and dry is key, i guess anything that will cause a dimension shift will cause an ejection problem. I dont reload, but, prior to shooting/hunting i make sure my chamber is completely free of any oil, cleansers or debris, i think its possibly along the same lines, if you continue to have problems, what i would try is some factory ammo, if it fires and ejects like it should, take a loadrd factory round and mic out the dimensions and compare them to yours. Also, you said for long range, are you loading the ammo hot? Meaning loading more powder? I dont know the technical term, i have a .30/06 that i get loaded "hot" because it can handle it, but my other '06 doesnt like those at all and i have problems, hope this helps and may give you an idea of what might be happening.
 

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Ricochet, Hospes only change was no lube which cured the sticky extraction.
I don' t have the explanation but what you posted from NHgun nut works for me.
 

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Thats all i could find this morning getting the kids ready for school, plus im not very internet savvy, if it leads you down the right path to the answer im happy to help.
 

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If oily cases are hard to extract it usually means your bolt face is not square.
 

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RR-- I gave the technical explanation for that specific occurrence as the OP asked. If you don't believe it, that's your problem.
There is an alternate reason, too. The lugs are set back in the action. Hard bolt lift on a set-back action only happens with fixed ejector guns with a slit lug.
 

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I didnt say i had a problem, quite the contrary i agreed with that. I said that i had a bolt face that wasnt square, reworked a new bolt and it fixed the problem. I dont see how i was being contrary? Or obtuse? I said i forgot about that as a cause of that happening, im sorry if the way i wrote it seemed offensive
 

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(Excess) oil in the chamber is well known to increase force needed for extraction. In fact I have read that's how the British make a proof test when no specific proof round is otherwise available.

Forget where, but think it was in one of the Gun Digests or Handloader's Digests.
 

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.

I suspect another reason is that excess lube left on the outside case walls inhibit the normal brass "spring back" after firing, leading to difficult extraction.

.
 

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Let's clarify some, please--

The English proof system used a lead pellet under a moveable breech or bolt face and a greased cartridge. On firing the grease prevented obturation and forced the base of the case HARD against the breech. That compressed the lead pellet a known amount and the result is listed in "tons" on the bottom of English guns.

IF the lugs are flat and smooth and IF the bolt face is square with the bore, there is very little increased bolt lift. All there is is friction of the lugs sliding in the recesses and the bolt face rotating smoothly on the base of the case.
IF a split lug has set back into the action or IF a bolt face is out of square, the case has to be 're-sized' by the bolt lift before the bolt can be opened.

If bolt lift gets gradually harder during a group, re-lubricate the locking lugs. Each firing squeezes more lube from those surfaces.

One more thing--- Lapping lugs perfectly smooth can REALLY mess up a rifle. Just like crankshafts and cams, the surface has to be smooth but not polished. There has to be 'space' for lubrication, otherwise you risk galling a lug which is a major injury. Cross hatch the back of the bolt lugs to hold some high pressure lube (STP). Do NOT use gun scrubber or other degreaser on high pressure surfaces.
 

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Yes, if a bolt face is not square, as it was in my case, it was easier to just replace the bolt entirely, and check the headspace. My bolt face was not square, so much so when i placed a casing on it, i could see that it was way out of square by the ammount of light i could see between the bottom of the casing and the bolt face. It was a quick and simple fix for me, it was on a Mauser action, got a stripped bolt, reassembled it, and it was perfect. Cleared the problem right out
 

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I don't know about square bolt faces but hard extrication is a pressure sign! You cleaned the oil off and the problem went away. Seem's to me you inadvertently shot over max loads. Oil can do that. What lube were you using? For many years now I've been using One Shot, never have the problem. In my oil days it happened now and then! That skim of oil on the case takes up room in the chamber effectively making the case not fit the chamber right.
 
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