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.338 Lapua Mag. excessive case length ?

 
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  #1  
Old 03-04-2011, 12:25 AM
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.338 Lapua Mag. excessive case length ?

I have been shooting the same .338 Lapua cases now for about 5-6 times without trimming the brass. I went to the range today and found that my groups started growing dramatically since they were fire formed. Trim length is recommended to be 2.714". Measuring the cases after I fired them, I noticed that the average length has grown to 2.737" and a couple rounds didn't allow the bolt to close easily. Will this cause excessive pressure spikes, and as a result have a significant impact on group sizes?

Last edited by 805_Sniper; 03-04-2011 at 12:37 AM.
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Old 03-04-2011, 09:16 AM
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Re: .338 Lapua Mag. excessive case length ?

[quote 805_Sniper] I've never seen so much talk over a press in my life! Who cares what press one thinks is better than another. The real question is can you shoot?! You can make the most consistent loads in the world, but if you can't shoot, you have worse issues! Most older folk can't compete with the younger generation due to the fact that you guys shake to much, are out of shape and breathe to hard, and your eyesight is out of wack... So Use your 15 presses and I'll see you at the range!!! [quote]



It's your press.


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Last edited by Broz; 03-04-2011 at 09:39 AM. Reason: add 805_Sniper quote
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Old 03-04-2011, 09:34 AM
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Re: .338 Lapua Mag. excessive case length ?

Quote:
Originally Posted by 805_Sniper View Post
I have been shooting the same .338 Lapua cases now for about 5-6 times without trimming the brass. I went to the range today and found that my groups started growing dramatically since they were fire formed. Trim length is recommended to be 2.714". Measuring the cases after I fired them, I noticed that the average length has grown to 2.737" and a couple rounds didn't allow the bolt to close easily. Will this cause excessive pressure spikes, and as a result have a significant impact on group sizes?
If the case neck is jamming into the end of the neck chamber Pressure will go up because
this condition will prevent the case neck from releasing the bullet as easy as one that is trimmed
to the proper length.

The reason for the groups opening up is the difference from round to round pressures caused by
this condition.

Also if the cases are growing that much it may be time to retire them or anneal them and trim
to length.

J E CUSTOM
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Old 03-04-2011, 11:26 AM
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Re: .338 Lapua Mag. excessive case length ?

805 sniper,

Good possibility that it's because you're crimping your bullets. Likely as not, you're doing this when you try to close the bolt and that long case neck is being jammed past the end of the chamber and being forced into the bullet walls, in effect, crimping them. You could be fixin' to have a truly nasty experience if this is the case. We may be older, wear glasses and out of shape, but we DO monitor our case length and make sure that this never happens. Incidentally, while I'm sure you can beat Mid Tompkins in a foot race, trust me, you'll never beat him on the firing line.

Trim your cases, and check your headspace. Bump it if you need to and consider the use of a body die from time to time, and this will all become a thing of the past.
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Old 03-05-2011, 12:28 AM
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Re: .338 Lapua Mag. excessive case length ?

Not monitoring your case length is some bad ju ju man!! Major pressure spikes going on when the brass jams into the throat with a bullet still in the neck of the case. I measure every case every time I reload after learning some of the undesirable effects of waaayyyy over pressure!!!
I figured this out when I had a few shots going like 6 MOA higher at 1200yrds, couldn't figure it out till I was getting ready to reload and I found I was .012 long on a few cases. Do the math 270 WSM @ 3341 fps gaining 6 MOA, it scared the crap out of me so I started paying attention to what I was doing!!!
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Old 03-05-2011, 01:29 AM
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Re: .338 Lapua Mag. excessive case length ?

Thanks for the info!!!!!!!! I loaded some rounds today with NEW Lapua brass and they shot like a dream! I am gonna anneal the old ones that caused me problems and trim them to length... I never shoot loads this hot and found that they have stretched the brass quicker than expected... Yeah, I got off easy this time... I have heard horror stories of ER visits because of excessive pressure... I'm glad I'm in one piece. Who would have thought that .020" could have been disastrous?!!! I guess only those that didn't pay attention in class...
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Old 03-05-2011, 11:15 AM
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Re: .338 Lapua Mag. excessive case length ?

Snatch the bullet from my hand, grasshopper
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