"Crunch" OK???

oneshot onekill

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Real quick. I have some IMR4064 and decided to make up some .308 rounds with it. I'm using Lake City Match Brass and 168gr Sierra BTHP. I loaded 42gr of the IMR4064 and noticed I'm crunching the powder at the very bottom of the bullet seat. Could that create an over-pressure problem? I stayed well below the MAX according to my book but I also realize LC Match Brass is thick and therefore holds less powder.

What say ye...
 

bohem

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Re: "Crunch" OK???

It's OK if you start low and work into it.

I shoot 4064 with a hefty crunch under 75 Amax in 223's without any trouble.

I crunch RL22 with 208's in my 30-06 and 180's in the 7/270.

I worked up all of the loads from something that still "shook" and kept going til I made the extractor groove change (increase) in diameter by 0.001" after firing, that's my realistic pressure limiter.

Then I work out the accuracy node.
 

johndoe

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Re: "Crunch" OK???

It is pretty normal for the crunch but if it bothers you get
a long drop tube problem fixed.
 

High Binder

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Re: "Crunch" OK???

Yep crunch is OK. Most of my hunting rounds crunch as I load them mag length.

I run LC brass as well and it's important to note that your should back off the loads the book say by a full grain just because of the LC brass.
 

High Binder

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Re: "Crunch" OK???

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: johndoe</div><div class="ubbcode-body"> if it bothers you get
a long drop tube problem fixed. </div></div>


Edited!
 

bohem

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Re: "Crunch" OK???

The long drop tube helps "stack" the powder better. It will fix a 102% case fill usually, it will not fix a 110% case fill like I'm running in the 223.

With such good control over the airspace due to a good crunch I actually get better ES numbers with a 105% ish fill than I do from a 95% fill with a faster powder.
 

High Binder

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Re: "Crunch" OK???

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bohem</div><div class="ubbcode-body">The long drop tube helps "stack" the powder better. It will fix a 102% case fill usually, it will not fix a 110% case fill like I'm running in the 223.

With such good control over the airspace due to a good crunch I actually get better ES numbers with a 105% ish fill than I do from a 95% fill with a faster powder. </div></div>

Oh, I only throw from a chargemaster 1500 so I have zero experience with the manual throwers so a long drop tube packing the powder does make sense, thanks!
 

lightman

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Re: "Crunch" OK???

My hunting load is 46.0 gr of 4064 with a 150gr bullet in a LC match case.Been crunching them for years with no problem.As someone else said,if it bothers you,get a long drop tube and trickle it in kinda slow.This charge (46gr)is about half way up in the neck,and my chamber is cut so that I seat the base of the bullet even with the base of the neck.So you may be compressing a little more,but not to worry,4064 don't care. Pete
 

High Binder

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Re: "Crunch" OK???

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Pete Theodore</div><div class="ubbcode-body">My hunting load is 46.0 gr of 4064 with a 150gr bullet in a LC match case.Been crunching them for years with no problem.As someone else said,if it bothers you,get a long drop tube and trickle it in kinda slow.This charge (46gr)is about half way up in the neck,and my chamber is cut so that I seat the base of the bullet even with the base of the neck.So you may be compressing a little more,but not to worry,4064 don't care. Pete </div></div>

That's exactly why I swaped my LC loads from 4064 to Varget. Varget gets me the same FPS with less grains.
 

oneshot onekill

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Re: "Crunch" OK???

Well, I tried out those rounds. They worked OK with no signs of over-pressure but I wasn't all that impressed with the performance. Back to the drawing board. My rifle seems to perform best (so far) with 42gr. of IMR4064 pushing Sierra 150gr. SPBT in the same Lake City brass with CCI200 Primers. Haven't checked the velocity but I can keep them around an inch at 300yds.
 

desertHK

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Re: "Crunch" OK???

My 155 scenar load is quite "compressed". As long as you work up your load accordingly and look for signs of high pressure, then you should be okay.
 

psinclair

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Re: "Crunch" OK???

Also make sure you have enough neck tension to hold the bullet in place on compressed loads....I've seen some bullets squirt back out a bit after seating throwing the COAL out of whack.