Small base dies

[Kinsman]

I have read on this forum about the use of small base dies to size brass fired in weapons with large chambers to allow them to be used in smaller chambers. I am faced with having a rifle with a tighter chamber that will not chamber rounds full length sized with a standard die.
The small base dies that I see in Midway are stated to be used to size brass for use in autos, but are not to be used for bolt guns.
Whyzzat?

 

[bowslngr]

Re: Small base dies

You can use them for a bolt gun, but the manufacturer is cautioning you that you may give up some accuracy as a result since the brass body will be slightly undersized in most cases.

 

[79M1a-texas]

Re: Small base dies

"that you may give up some accuracy as a result since the brass body will be slightly undersized in most cases."
This would only be the case for the 1st firing after you use the small base body die.
After this 1st firing, the case should match your chamber. I have used the small base body die on some once fired LC Match & NM, then after this 1st sizing, I use a FL bushing die for the neck. Yes you might be over-working the brass slightly using this method, but how would you know.

Just saying.

 

[bowslngr]

Re: Small base dies

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 79M1a-texas</div><div class="ubbcode-body">"that you may give up some accuracy as a result since the brass body will be slightly undersized in most cases."
This would only be the case for the 1st firing after you use the small base body die.
After this 1st firing, the case should match your chamber. I have used the small base body die on some once fired LC Match & NM, then after this 1st sizing, I use a FL bushing die for the neck. Yes you might be over-working the brass slightly using this method, but how would you know.

Just saying. </div></div>

Ummm...if your brass turns out undersized the first time you resize with a small base die, it will be after every subsequent use of that same die. Of course if you switch dies after the first sizing you get a different result, but I don't think that was the question.

 

[Kinsman]

Re: Small base dies

bowslngr

The idea I have is a one time trip through the small base die, to get the brass to work in the tight chamber. After fireforming, I would use the standard die,
The brass that I have been using in the rifle works well with the std die.

Thanks all for the info.

 

[bignada]

Re: Small base dies

Gonna shoot unknown LC or other military brass? Probably want to SB size the brass first, to be sure...

Lots of reasons to use a SB sizing die. Brass might have variations, even virgin. SB sizing gives you a baseline to begin from. Brass might be way under go-gauge (minimum chamber oal) this is way more important than body width, SB die could add a bit of length from base to shoulder and increase first fired precision.

Probably want a SB die set if loading for a Rem 740/7400, Browning BAR and other commercial semi-auto. Best tool to let you see what your chamber is doing is an RCBS Precision Mic or Wilson Case Gauge. Measure the virgin brass and then your 1x fired dimension. If getting lots of variation (.005+), might want to set the barrel forward to reduce oal chamber dimension.

Of course, don't want a fat-pig chamber bore either. Want to minimize your sizing as much as possible. OAL dimension is more critical to accuracy/precision than body dimension of chamber.

 

[Leaddog]

Re: Small base dies

I've had to use a small base die with some Lake City brass I had a few years ago. One time through the small base and after that, I went back to my regular full size dies after I shot them.

 

[dksac2]

Re: Small base dies

I don't know if the LC 09 brass is better than the old LC, but it chambers perfect in my semi auto with using a FL sizing die.
I used to use a SB die for the first sizing, but then found it has not been necessary with the LC brass I've been getting as of late.
The LC cases need more work than some others, but as much brass as I loose from my semi, I just can't see using Lapua, that gets saved for the bolt gun.

John K