.308 shoulder setback

[Stats Shooter]

Question for y'all

How far do y'all set back the shoulder in an AR-10 (.308)?
In my bolt action rifles I neck size but in my semi's I full length size which sets the shoulder back 6 thousandths using standard base FL RCBS dies in my .308.

I'm just curious how far everyone else bumps the shoulder in a semi automatic.. also, how big of a bump do y'all do in .223?

[Mobuck]

Full length size by bumping the die with the shell holder--no measuring required.

[ireload2]

I load the 8X57 for an autoloader and I bump the shoulder back .002.

I also manually run all rounds through the rifle to verify they will chamber without fail.

[shootbrownelk]

I've got an AR-10 in .308. I use RCBS dies made especially for AR's. They squeeze the case down to minimum dimensions at the base. They work great. I have a set for my AR-15 in .223/5.56 as well. Never had a chambering problem after using them.

[Stats Shooter]

. Full length size by bumping the die with the shell holder--no measuring required

Yea that's pretty much what I'm already doing....I use RCBS FL die and RCBS press and RCBS shell holder (standard, not short base). I use this combo in all my semi automatic rifles and pistols.

It results in a 0.006 bump in my AR-10, which I have a very accurate load for. I neck size my bolt guns but I wonder if I can extend my brass life while still feeding reliably in semi automatic rifles by not setting the shoulder so far back.

[F. Guffey]

In my bolt action rifles I neck size but in my semi's I full length size which sets the shoulder back 6 thousandths using standard base FL RCBS dies in my .308.

Again, I do not want to be a part of confusing reloaders so I will make an attempt to explain for the benefit of new reloaders. I do not have a full length sizing die that will shorten the length of a case from the shoulder to the case head .006". I have cases that refuse to be sized because of their ability to resist sizing. In the perfect world my dies will shorten a 30/06 case .005" from the shoulder to the case head.

And then there is that part about 'bump', I have presses that 'bump' because they are cam over presses. I find it impossible to bump the shoulder back with a die that has case body support, again; I know it sounds cool to 'bump' the shoulder back.

If I ever wondered about the ability of a die and shell holder to size a case I would measure.

F. Guffey

[Metal god]

I'm in the middle of my first 308 AR type build so no info there for you but I will say that I'll likely set them back .003 and no more then .004 . which is the same as I do with all my AR-15 firearms .

. Full length size by bumping the die with the shell holder--no measuring required

Me to with one very big catch . I use Redding competition shell holders for all 223 & 308 sizing
https://www.midwayusa.com/s?userSear...temsPerPage=48

They allow you to still have the die and shell holder make contact while sizing the case longerby as much as .010 in .002 increments depending on the shell holder you use . I absolutely love these things . You get very consistently sized cases at the size you want . For me outside of the obvious must haves ( press , scale , calipers , dies etc ) . The competition shell holders are at the top of the list of must haves that you really don't need

See post #6 to see how they help press deflection
http://thefiringline.com/forums/show...37#post6409737

[Road_Clam]

Originally Posted by Mississippi

Question for y'all

How far do y'all set back the shoulder in an AR-10 (.308)?
In my bolt action rifles I neck size but in my semi's I full length size which sets the shoulder back 6 thousandths using standard base FL RCBS dies in my .308.

I'm just curious how far everyone else bumps the shoulder in a semi automatic.. also, how big of a bump do y'all do in .223?

By design you (in theory) will achieve adequate shoulder set back by setting your sizing die to have a slight amount of interference overcam with the shell holder. I purchased the Larry Willis headspace gauge for acquiring ideal shoulder setbacks. I have set my rock chucker press using the "overcam" method then checked my sized casings vs. new factory ammo and I find the results to be pretty close to ideal. The overcam method gets the shoulder to within +0 / -.004 of new brass. (a negative value is the better condition as it will create a larger headspace gap, but it will always allow complete chambering of the round). Complete chambering is important for semi auto feeding. The only downside of excessive headspace clearance is the fact it's tough on the brass expansion and can cause case separations. I have created dummy fire formed casings for all my rifle chambers and I use these to establish my ideal shoulder setback of about -.003". Since I started doing this I have not had any case separations. I had several case separations on my 300 Win Mag which is inherently really tough on brass if you don't have ideal headspace set.

http://www.larrywillis.com/

[Stats Shooter]

. Me to with one very big catch . I use Redding competition shell holders for all 223 & 308 sizing

I didn't even know these existed. That would take the guess work out of trying to get a consistent shoulder setback. No adjustment necessary. I might try those metal God to see if I can help extend the life of my brass....... Especially in my .300 WM and .338LM

[ed308]

I usually bump once fired brass for my ARs .002 to .003. But I have a 270AR that I need to bump .005 in order for it to feed without problems. Same for my bolt .308. I don't mix the brass between the two.

[F. Guffey]

I didn't even know these existed. That would take the guess work out of trying to get a consistent shoulder setback. No adjustment necessary. I might try those metal God to see if I can help extend the life of my brass....... Especially in my .300 WM and .338LM

The 300 WMm as we all know, is a belted case and we all know it head spaces on the belt. If you have plans on increasing case life I suggest you determine the length of the chamber from the shoulder of the chamber to the bolt face.

And then it gets complicated; The Redding Competition shell holder can hold the case off and out of the sizing die and prevent the case infront of the belt from being sized. I have collets for my lathes for JIC work, as in just in case the case expands in front of the belt and refused to be sized I can reduce the diameter with collets. But, I am one of the few that measures; when I find case expansion in front of the belt that measures .518 I know the cases have been hammered with heavy loads. Then there is the complete story, if the case has been hammered and the case has expanded in fron to the belt the case head has been crushed and the case head has increased in diameter etc.

And then there is the remote chance the cases had soft case heads.

F. Guffey

[Road_Clam]

I've gotten myelf into the prudent method of giving all my 300 win mag casings the internal "paper clip test". I've had to prematurely retire many casings because of the stressed ring down near the belt. R-P brass seems to be the worst as far as the premature case separation issue.

[F. Guffey]

Then there is the complete story, if the case has been hammered and the case has expanded in fron to the belt the case head has been crushed and the case head has increased in diameter etc.

I always say "think about it"; judging by the responses I do not believe I am getting responses from reloaders that "think about it".

A builder/reloaders was having trouble forming cases for his new wildcat ('actually' 2 wildcats). First, before I go to help him I have to determine if 'it can be done'. The first tool he ask me to bring was the 'other' #4 RCBS shell holder. Instead of bringing the #4B shell holder I added a gasket cutting ball peen hammer. The purpose of the small hammer is to drive the cases into the #4 shell holder, the case heads were upset with heavy loads and the extractor groove in the case head had expanded to the point the case could not be shoved into the shell holder. With the expanded case head the case body in front of the belt has also been expanded meaning there was no sizing the cases without a collet; not a problem, he has 2 lathes with 4 sets of collets.

Anyhow I talked him out of using cases that would not fit the shell holder and or cases that had expanded ahead of the belt. He only lost 40 cases out of 240.

F. Guffey

[Stats Shooter]

The 300 WMm as we all know, is a belted case and we all know it head spaces on the belt. If you have plans on increasing case life I suggest you determine the length of the chamber from the shoulder of the chamber to the bolt face.

F. Guffey: I plan to do that...I am waiting on the barrel for my .300 wm I ordered from Shilen. I have the Hornady set that measures how much your brass is expanding by measuring the bottom of the case to the shoulder of a fired case, in that rifle. But before that you measure an un-fired case to see how much it expanded. In that way, you know how far a FL sized case from your setup is expanding in your gun, and also the size of the chamber.
Then, you can determine, from the fired case, how far back you are setting the shoulder of re-sized brass.

As for my .308's, I was just curious how far back folks who reload for semi-auto guns set the shoulder to get reliable feeding in their guns. I have reloaded tens of thousands of AR-15 and AR-10 fired brass but have always just used an RCBS FL die and RCBS shell holder and pushed until the base and the die touched. I shoot ALOT, (maybe 300-500 rounds per week) so extending brass life by simply not pushing the shoulder back so far (assuming it still feeds and extracts reliably) is attractive to me. Plus, every time I change brass, I do a mini-workup to see if my load works in the new brass which costs me components and time ( I have two little boys and I like to spend time with them too).

But I thank you ALL for the info, mr Guffeys posts are always appreciated as it seems he knows more than I will ever know....but I am getting better.

Oh, and one other question real quick...Do any of yall see any accuracy improvement or accuracy loss due to limiting shoulder setback?

[JeepHammer]

I'm reluctant to tell anyone to do anything other than SAAMI specification, simply for safety's sake.
The big idea is to have the round be safe in every firearm chambered for that caliber.

This would be for reference only, not recommending anything but standard SAAMI specification.

The big idea is to set the shoulder back, squeeze the case sides back in, AND and resize the neck to hold another bullet.

*IF* the case shoulder is set back to fit ONE SPECIFIC CHAMBER,
And the case sides allow that case to fit into that one chamber,
And the neck will hold another bullet,
Then the brass fits the chamber better, 'Tighter' fit means the combustion doesn't have to swell the case as far to reach chamber limits.

The theroy...
(and I stress 'Theroy' since there are people successfully shooting 'Factory' rounds accurately)
Is a brass that fits tightly in the chamber won't be a variable.

In practice I have found that hand fitted brass will usually increase consistancy, and therefore accuracy.
Consistancy is the big deal here, premium new brass that is CONSISTANT produces the same results in most cases...

In my LONG RANGE BOLT rifles I size the brass specifically for that rifle.
Semi-autos I usually knock back to some semblance of SAAMI so they interchange in any rifle of the same caliber.
The reason being semi-autos have consistancy issues that exceed what ever case expansion issues there might be...

Without getting into it too much, rotating semi-auto bolts rarely line up or lock up in the same position two times in a row...

Getting a good fitting brass in the chamber will certainly cut back on inconsistencies which can't hurt a thing, but these will be for specific firearms & cant be interchanged with other firearms.

I set the shoulder back about 0.002" at a time until it fits the chamber, and no more. This is a HUGE pain in the behind to get the dies set up correctly, and EVERY case has to be gauged since you are so close to the headspace of the rifle.

Once set up, you sure don't want to change settings, and stubborn cas s will need an extra 'Push', so a feeler gauge set helps with that.
An appropriate blade(s) between case & shell holder will bump stubborn cases a 'Smidge' without having to reset dies.

Hyper accurate cases are NOT the territory for progressive loaders, single presses are not created equal, so a solid press is a requirement.

[F. Guffey]

Once set up, you sure don't want to change settings,

I am not one of those reloaders that is afraid to loose my place; I adjust my dies ever time I use them, I secure the die to the press with the lock ring, I do not secure the lock ring to the die.

And I noticed you move the shoulder back when you size a case and, again, I wonder how you do that because I find it most difficult to move the shoulder; and if not difficult it has to be near impossible.

Thank you in advance.

F. Guffey

[308Loader]

Guffy, I would love to buy you a cup of coffee and pick your brain so that I might better understand some of your posts. Always thought provoking but not quite clear, some times self contradicting. good stuff. If your ever in the twin cities send me a pm.

As for my ar10 loads I stick with saami spec. I find that a small base die is the way to go. An auto extracting and feeding rifle is going to be rough on the brass.

[zeke]

If I was only reloading for one 308 AR-10 style, would measure the shoulder on new brass, and compare it to once fired for a starting point. Then would try moving shoulder back about .003, and see if that adequately sized brass to feed and fit in chamber.

With RCBS dies, am capable of setting shoulder back fair amount, and now think i know why the redding dies do not operate the same. Thanks to Metal God.

But most (and like everything else, there be exceptions) of my 308 loads are designed to fit into multiple semi auto/bolt actions. Then I set the shoulder back to original spec.

Can even set the shoulder back on new brass with a CZ 550 vermin rifle. It crush fits new brass shoulder back .oo1, then fire forms it.

"I am not one of those reloaders that is afraid to loose my place; I adjust my dies ever time I use them, I secure the die to the press with the lock ring, I do not secure the lock ring to the die. " This, and use a once fired case to square up the die.

[Stats Shooter]

You guys have explained a lot, and confirmed some of my assumptions as well as explained some things I was not aware of.

With respect to the .308, think I am going to stick with FL sizing since it is in an AR-10, and my FL RCBS dies size Federal cases to nearly the exact same deminsions as Federal GMM....And my 175 gr load is 1/2-1/4 MOA. Plus it is a bit hard on brass anyway so I'm not sure the longevity gain is worth the risk of not feeding properly.

However, my .300 win mag might benefit from the Redding bases metal God mentioned because the .300 wm is tough on brass and I am using it for F-CLASS 1k once I get the new barrel put on...And Norma brass ain't cheap!