IVI Brass sizing issue

Riven

Riven

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I have a been loading 308 for about a year with no issue.
I have now got a large amount of IVI brass that i have been prepping.
The issue is the IVI will not chamber after sizing but 308 in the same set up will. Well some IVI will but they are VERY hard to close the bolt on.
My gun is Mossberg MVP chambered 7.62X51 so thats not the issue.
Trim length is good & i have resized some a couple times with no luck.

Is there a die that pushes the shoulder back more?
 
I am full length sizing & my die is set as deep as it can go. Using Lee dies

So if i use a small base will i have to use it every time with this brass? or only the first time to get them to chamber?

This brass was way over size, was from a MG for sure. actually used a 30-06 to body size then full length with 308.
Had to buy a decapping die! crimped primers suck!!!
 
Assuming your chamber isn't too loose you should only have to use the SB dies once. They work the brass more than regular dies so if you don't need them afterwards return to your neck or regular FL sizing.
 
I've never needed small-base dies. If brass is stubborn I will hold the brass fully inside the sizing die, camed over, for several seconds before extracting it. This seems to help a lot with hugely oversized brass I've gotten that may have been fired in machine guns. Some of it I found beside piles of steel belt links so it's a safe assumption. Gotta love it when the military rents a civilian range and leaves neat little piles of brass everywhere.
 
So i ran my die 1/8th turn deeper & left the shell in it for 30 seconds and it does fit in the chamber now. Very tight but action will close.
Im not sure if that setting the die deeper made the difference as it was already bottomed out or it was the wait time but it helped!
Thanks every one!

Still going to look into a small base die and see if my buddy's dad has a set of 308 dies i can try sizing in as well.
 
Riven said:
So i ran my die 1/8th turn deeper & left the shell in it for 30 seconds and it does fit in the chamber now. Very tight but action will close.
Im not sure if that setting the die deeper made the difference as it was already bottomed out or it was the wait time but it helped!
Thanks every one!

Still going to look into a small base die and see if my buddy's dad has a set of 308 dies i can try sizing in as well.
Click to expand...

check when sizing if there is a space between the sizer and the shell holder.
there might be more spring / play in your press than you think and you might need to over cam more
 
Chambers and resizing dies vary in size, meaning in length and diameter. Sometimes you can get by with a standard die and sometimes you need a small base die.

Example, I have a standard Lee .223 die that will size the cases smaller in diameter and push the shoulder back more than my RCBS small base die.

I buy bulk once fired military Lake City 5.56 and 7.62 brass and size it the first time with small base dies and also pause at the top of the ram stroke for 4 to 5 seconds.

Pausing at the top of the ram stroke reduces the amount of brass spring back after sizing. I would try pausing and even sizing twice with a standard die and see if that works before getting a small base die.

Small base dies will reduce the case diameter .002 to .003 more than a standard die. And a small base die will also push the case shoulder back .002 to .003 more than a standard die.

Bottom line, a small base die reduces the case to SAAMI minimum dimensions. So watch the amount of shoulder bump when using a small base die and not push the shoulder back too far.

I'm just finishing up sizing and prepping 300 Lake City 7.62 cases and some of then needed sizing a second time with my small base die for the correct amount of shoulder bump.

Military cases can have have thicker necks and I highly recommend lubing the inside of the cases necks, My Lake City 7.62 cases have a neck thickness of .014 to .015 and if you do not lube the inside of the case neck the expander drag can pull the shoulder forward.

This is where having a Hornady cartridge case headspace gauge comes in handy to measure the exact shoulder location vs a drop in case gauge.
 
If the rounds chamber smoothly up until you try to close the bolt, the problem is likely with the shoulder position more so than the body diameter.
Have you tried measuring the case head- shoulder datum dimension? If you have the tools to measure it, compare to a case that does fit properly. Even a couple thousandths of an inch makes a big difference in feel.
 
Yes I did. I dropped 2gr and even started with the starting load with a 10 thou jump. I went back through some threads about this brass here and a few people were saying to drop a few. I believe you were even one of them. :)


Bought some lapua and havent tried these since
 
Below are two .308 drop in gauges, a Dillon and a JP Enterprise case gauge.

In the Dillon gauge below is a "fired" 7.62x51 Lake City case and is one of the longest fired cases from a half a coffee can of 03 dated fired Lake City 7.62 cases. These fired cases varied .006 in headspace length to show you variations in military chamber headspace. And what you are fighting against when resizing once fired military 7.62 cases and the brass spring back after sizing. Meaning the resized case wants to spring back to its fired size after sizing and grows and springs back after sizing.

You normally do not have this problem with cases fired in "your" rifle because the case was fire formed to "your" chamber and springs back smaller than "your" chamber. But with once fired brass and range pickup brass there is no guaranty that a full length resized case will fit in "your" chamber. And this is where a small base die comes into play, because the small base die will push the case shoulder back .002 to .003 "more" than a standard die. "BUT" even with my RCBS .308 small base die I'm getting .003 variance in shoulder location after sizing because of brass spring back from the military chambers. (maching gun fired brass)

UPCvxyL.jpg


Below is the same fired case in the JP Enterprise gauge that is a smaller diameter than the Dillon gauge. And after sizing if the case drops all the way into the JP Enterprise gauge between the headspace slot it will fit in any chamber. Meaning the JP Enterprise gauge is closer to minimum SAAMI dimensions in diameter and headspace length.

zOVqgmU.jpg


Below is my .308 RCBS Precision Mic and if I put a .308 GO gauge into the gauge it measures two marks to the right of zero. (-.002) And when I place the fired Lake City case above in this gauge it measures +.010 or .012 longer than the GO gauge. This means the chamber this case was fired in was .003 longer than a commercial .308 Field gauge, which is .009 longer than the GO gauge. And why you have problems pushing the case shoulder back to fit in your .308 rifle. The distance between the .308 GO and NO-GO is .003 and the field gauge is .009 longer than the GO gauge. Meaning a used worn .308 rifle is allowed .006 wear past the NO-GO gauge.

fXsKe7r.jpg


NOTE, I only have one Precision Mic above and prefer the Hornady cartridge case headspace gauge because it will measure any normal caliber case and is cheaper than the RCBS Precision Mic.

Below headspace gauges explained, if you look at a SAAMI cartridge and chamber drawing it lists headspace as min and max with .010 in between.

Pacific Tool and Gauge offers three lengths of headspace gauges per rifle caliber. In order from the shortest to longest, they are: GO, NO-GO, and FIELD:

1. GO: Corresponds to the minimum chamber dimensions. If a rifle closes on a GO gauge, the chamber will accept ammunition that is made to SAAMI’s maximum specifications. The GO gauge is essential for checking a newly-reamed chamber in order to ensure a tight, accurate and safe chamber that will accept SAAMI maximum ammo. Although the GO gauge is necessary for a gunsmith or armorer, it usually has fewer applications for the collector or surplus firearms purchaser.

2. NO-GO: Corresponds to the maximum headspace Forster recommends for gunsmiths chambering new, bolt action rifles. This is NOT a SAAMI-maximum measurement. If a rifle closes on a NO-GO gauge, it may still be within SAAMI specifications or it may have excessive headspace. To determine if there is excessive headspace, the chamber should then be checked with a FIELD gauge. The NO-GO gauge is a valuable tool for checking a newly-reamed chamber in order to ensure a tight and accurate chamber.

3. FIELD: Corresponds to the longest safe headspace. If a rifle closes on a FIELD gauge, its chamber is dangerously close to, or longer than, SAAMI’s specified maximum chamber size. If chamber headspace is excessive, the gun should be taken out of service until it has been inspected and repaired by a competent gunsmith. FIELD gauges are slightly shorter than the SAAMI maximum in order to give a small safety margin.


Below in the .308 chamber drawing at the circled X marks you will see 1.630 as min and 1.640 max headspace and .010 between.

L6eq7Cc.jpg


Below you can see how much longer military 7.62 NATO headspace gauges are than commercial .308 headspace limits. And why the resized cases spring back longer than "your" chamber and chamber hard or not at all.

51URdr8N%2BmL.jpg
 
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sucks that you sized a thousand of them before determining there could be a problem

Annealing the brass and then running them through a SB sizer die should make them chamber like butter. You may need a Redding competition shell holder set which will allow you to fine tune headspace in .002" increments
 
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