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head space??


Albert 888
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Having problems with my howa 308. At first I thought that my brass was showing over pressure sighns as I am getting a half moon shape mark on my brass from the bolt face which could be my fault,but on further inspection my bolt lug has score marks on it,I have run some factory and home load ammo through the mag and into the chamber and then extracted, the brass is marking as the bolt face is rubbing the brass. I have stuck a fag papper on the brass and chambered and it's rubbing the papper off. So is my head space to tight. The barrel has been removed from the action before this as my chamber had a machine mark in it and it was marking my brass. can anyone shed any light on the matter please and it's beginning to p##s me off.

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Think your stressin for nuffin bro.

Black your lugs, if only one is contacting stone it until the other contacts as well.

 

U.

We were always told if you have black lugs you got a clip round them and told to get them washed straight away :innocent::innocent::/

Edited by hawkeye
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I'm using Lapua brass and that's been fired 3 times now. I have only necksized as I'm waiting for a rcbs fl die to turn up. The last load I put through it where 2.2g over max book, Using N140 and 155 scenars the Base of the brass had a proud half moon shape from the bolt face extractor pin cut out,it started to do this at 44.5g,but didn't notice untill I cleaned the brass:-o ,so I'm going to back it off to around 44g,still have some test amo made up and it gave a 0.5" group will put over a chrono to see what they do. The 308 mark on the barrel isn't obviously out of position,will check for match marks and report back,I can remember seeing two punch marks when I stripped it down.

The score marks on the lugs could be down to tight bolt lift after firing,it didn't seem that tight but it was raining and i was shooting the 223 whilst waiting to cool,I'm now putting a very light film of pneumatic grease on the lugs. Thanks for the info Im sure with everyones help I will get there in the end. I always clean behind my lug and wear clean underwear.

Cheers Albert

Edited by Albert 888
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Just a suggestion, I loaded some hotter than intended once (I meant to go up a grain but went up 2 for some reason which put it a gn and a half over max) and no matter what I did after that the brass still got scraped - I came to the conclusion the extruded "bump" in the head of the brass was causing it. New brass sorted the problem 100% though I've no idea how you'd check for the bump I'm talking about, that said you've had three firings out of your current brass so it wouldn't break the bank too much to get some new brass.

 

I've also taken to f.l. sizing each time, seems much less hassle though you may get less life out of your brass that way. Seating the bullet further out will also lower the pressure a bit so might help too.

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My lapua brass was tight after a few reloads, the half round scrape my remmy did, I just sized a fraction more.

Fister is spot on with the brass losing its elasticity.

You could anneal them or wait till necks start splitting and bin them.

I would not assume it is down to being over book at first.

 

U.

Edited by Underdog
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Yes using 155 scenars and coal in my book is 2.795 that I have been using. The bolt face is marking 155g sp ppu unshot live amo when run through the mag into chamber then extracted,that's why I thought it was the head space. The chamber is as clean as, and I'm almost certain that I haven't got any lube in the chamber. I run a oiled patch through the chamber for storage after cleaning then clean out before shooting with 3 wet patches with brake cleaner then 2 dry patches. It was heavy rain when I test shot,I did my best too keep everything as dry as I could. I am going to back off the load. I won't put any more home loads through it untill I source a fl die.

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reading this it appears you only got pressure signs at higher charge levels.....

 

back them off

 

highly unlikely it passed proof with a very short chamber

sound like you have

 

a) neck sized lapua cases which are notoriously hard and don't have the same spring back

b ) hot load for your bullet/case choice

c) a small but in spec chamber

d) previously had some crud in your lug recess and scored the lugs (don't go stoning the lugs without headspace measuring equipment)

 

back off your charges and FL size your brass and see what happens

Edited by Bewsher500
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I have had a few chats and explanations of some experienced rifle shooters and they are coming up with the same as yourself. I'm currently doing my best to track down a fulllength die,going to have to order one. The chamber is stainless and I'm 80% I hand no contamination on the bolt or chamber.

Apparently the ppu 150 g sp factory rounds I have been chambering are notoriously tight,and chambering them with no grease on the lugs has caused the bolt to mark,never shot them just chambered.One of my fellow shooters has offered to spend some time with me and shoot some loads over the chrono. When i get the fulllength die I will make some more loads. Studying the brass my max load will be around 44g of n140.the book says max is 43.3g at 2624 fps. I had touching groups at 100m with 37.5g but the drop was over 20" at 300m,estimated at 2350 fps.

Looking at the Lapua data thier spec is 2820 fps at the muzzle with the 155g scenars. Thanks for the explanations.

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