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Small base dies


Julien Boit

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Hi all,

Do you guys uses small bases dies for reloading the 223 for your AR15 ?

I recently had trouble with my newest rifle.

It seems to come from the cases which would be not correctly resized, despite they went through a total resizing with LEE dies and went Ok with the Dillon gauge.

I did not have the same problem with brand new cases from Remington.

The faulty cases are HP (Hirtenberger) and were fired through a Sig 552 and HK G36, maybe in full auto.

I heard about Dillon making some as well as RCBS, right ?

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With brass outof full-auto guns I'd be more worried about case stretch causing overly long cases. And also leading to case separations after a few loadings. Measure o.a.l. I've never used small base dies and never needed them, so I can't speak to their usefulness or costs.

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I believe the chamber is not "stock".

The rifle is called BR20 by the maker (SDI), BR stands for Bench Rest.

This is a match type AR with stainless 1/8 bull barrel, and all the bells and whistles (RRA match trigger, free floating handguard, PSG1 style grip...) .

The chamber had been measured by a gunsmith and it's 5/100 mm bigger than the smaller CIP measurements.

So it's more on "match chambering" side.

OTOH I tried to load the same rounds in my DPMS M4 which is larger and sometimes the same problem appear : The case is not totally chambered and stuck halfway.

Somebody told me to trim a bit my resizing die, I've done this before on pistol cartridge dies but would it work for a necked case ?

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Julien,

I am not sure trimming the die would be a good idea.

Headspace would be affected.

Your chamber is larger than the small side in which dimension ?

If diameter wise, you could go with a small base die.

Or

Different brass.

I am not familiar with the brass you mention, but if the problem resolves with other brass, it could very likely be a brass related problem.

I have never used a small base die.

Travis F.

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I have had a similar problem with reloads in my Bushmaster barrel. I switched to SB dies, and the problem persists. It is not so much a problem of the case not going all the way into the chamber. But if I chamber a live round and don't shoot it, it is very difficult to pull the charging handle back and extract the live round from the chamber. It can be a pain at the end of a stage to unload and show clear at times.

I have tried loading once-fired brass and older, Fired from my chamber and others. I have made sure to trim the cases so they are not too long. Maybe it's the die setting at the shoulder.

But for the time being, I am just shooting factory ammo. That doesn't seem to have any problem.

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Sounds like a tight throat to me. I had a Krieger "match" chambered barrel and it's throat was next to nothing. Everything would "stick" in the darn thing. All my loads showed pressure signs. I had JP run his reamer into the darn thing and bump the throat out to his specs and then it was great!! It was a very finky B#^$tch befor, now it shoots most everything well. BTW the most "sticky" ammo was WW 193 ball, Q3131 and Q3131A. KURTM

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PACMAN - Most dies are flared out a little at the bottom of the die to help the case enter easier. The case is not sized in this area, but it is at the base of the case where the brass is thickest and shouldn't expand. SB dies size a little farther down the case.

Maybe someone can explain it a little better though.

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In fact I think my question was incorrect.

The small base will resize the case lower than a regular die, what I need in fact would be an Undersized die such as what EGW does for handgun cases.

In my upper, the cases are stuck about halway and they shows marks about an inch under the mouth of the case, not at its base.

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  • 4 weeks later...

Hi all, I'm back, still stucked with that damned thing.

I made some experiments :

I took the upper out of the lower and hand chambered Factory ammos.

Everything is ok so far, I did the same thing with new brass (RP) and everything is fine too.

I did it again (oups ;) ) with resized cases from different makers and it's also fine.

When I try to do the same with the upperback on the lower, here comes the trouble.

If I handload the rifle the bolt will lock, if I do it from the mag, it seems that the bolt head does not catch properly the bottom of the case and it get stucked.

What could that be ?

:(

It starts to piss me off, I want to shoot factory ammos , not manually but in repetition, it's not a bolt rifle, it's an AR !

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Julien:

Does the back of your chamber have a champher to it, or is it square sharp? I noticed all the factory barrels I have are nicely rounded in this area. Yours might be cut square and never beveled after final reaming and extention installaton. Are the marks on the case kind of a scrape and then a sharp half moon shape crease in the case??

Garrett: I think I would also check the neck area of that Bushy barrel. Maybe a bit tight there. Does a bullet easily drop into a fired case? Checking the neck length might pay off also. I'm shooting in the dark but I would bet on throat or neck. Going to Mississippi 3-gun?? KURT

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Kurt,

Should a bullet be able to drop into a fired case? I would think that would be a bit loose.

I'll be in Chicago the day before the MS 3-gun. Makes for a bit of a drive. I might still be able to swing it, though. I'll have to see when we get closer, if it hasn't sold out by then.

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Garrett:

Yes it should be able to fit into a fired case with not too much problem. If it doesn't the neck is under size for what we do, Real tight bench rest chambers won't even chamber standard brass, and for those you end up neck turning to true the case and gain clearance! I don't think MS will be full but you might give them a shout! KURT

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  • 3 weeks later...

Julien,

Is your Lee sizing die bottomed out on the shellplate when the handle on your press is all the way down? I have a Colt Hbar that does what yours does with reloads. I think what's jamming on mine is the neck of the cartridge. If my die doesn't totally bottom out on the shellplate, all my reloads stick in the chamber (even before I fire them).

The next time I set up for 223, I'm going to grind down the bottom of the die about .010-.020" to see if I can set the neck of the case back just a bit farther.

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