New Lapua brass headspace?

[broncman]

Just ordered some new lapua 308 brass for my FTR gun. How much of an accuracy difference does headspace with new brass make? My headspace is in the neighborhood of 1.632. If most new brass is .004-.005 under SAAMI spec of 1.630, how much will this effect accuracy?

I allways resize brass to .002 under my chamber size.

Thanks
Ken

 

[KT]

After you fire it the first time you will be good to go. It will take shape of your chamber.

I wouldn't expect your best accuracy on brand new brass anyway.

KT

 

[jlow]

308 brass cannot have a headspace of 2.632 since the SAAMI spec for brass length is only 2.015. FWIW, the last batch of Lapua 308 I received had a factory headspace of 1.619.

 

[broncman]

Sorry, I meant 1.630 for headspace......

So at 1.619...that will deffinitely take a firing to get to chamber length.

Thanks for the info!

 

[CatShooter]

Just ordered some new lapua 308 brass for my FTR gun. How much of an accuracy difference does headspace with new brass make? My headspace is in the neighborhood of 1.632. If most new brass is .004-.005 under SAAMI spec of 1.630, how much will this effect accuracy?

I allways resize brass to .002 under my chamber size.

Thanks
Ken

It is not under SAAMI - SAAMI for the .308 is 1.627" to 1.634"

It will have no effect on accuracy.

 

[jsthntn247]

The first firing on my 300 WM had to expand .025 to form to my chamber and never had a problem.

 

[bronkman]

A bit off topic but it does concern case size.
I ordered some .30-06 Lupua cases recently and the case bases only measured .464 and half. I have never used Lupua .30-06 cases before but all other Lupua cases such as br, .308 and such have measured .468 to .469. Also, I picked up some R-P cases from a local gunshop that only measured .463 and half.
What is everyone else finding on their new case orders?
Jim

 

[BoydAllen]

One little detail that seems to have escaped someone's attention is that belted cases such as the .300 WM do not headspace off case shoulders, but rather on the belt. This is not to say that strict attention should not be paid to setting FL dies for these calibers so as not to push back shoulders of fired cases any more than one would a rimless case. Generally, I think that for best results from really accurate rifles, with highly tuned loads, using brass that has been fired at least once is preferred, but the need to do this depends on the application, and its accuracy requirement. For average field use, I doubt that the difference would be noticed.

 

[CatShooter]

The 300 WM has TWO headspaces.

The first is the belt @ 0.220 (-0.008") tolerance.

The second is the 0.420 Datum line on the shoulder, but holds a slightly larger tolerance than normal cases.

On the first firing, the belt controls the headspace, but after that, the shoulder controls the headspace (unless you are "ignorant" enough to shove the shoulder all the way back).

Negative headspace is your friend

 

[Raythemanroe]

That's kinda what I'm thinking on my 300 wm build!

 

[jlow]

Sorry, I meant 1.630 for headspace......

So at 1.619...that will deffinitely take a firing to get to chamber length.

Thanks for the info!

Sometimes people will be surprised at how well new brass that has not expaned to chamber dimentions will shoot. The reason I think is because unfired brass has not have a chance to banana at all.

 

[CatShooter]

Sorry, I meant 1.630 for headspace......

So at 1.619...that will deffinitely take a firing to get to chamber length.

Thanks for the info!

What makes you think your brass has a headspace of 1.619". Did you measure it?

 

[Down South]

308 brass cannot have a headspace of 2.632 since the SAAMI spec for brass length is only 2.015. FWIW, the last batch of Lapua 308 I received had a factory headspace of 1.619.

All the brand new Lapua brass i have measures 1.618 with the Hornady tool on my calipers. On my older FTR rig a piece of brass that had been fired "HOT" and was hard to chamber measured 1.622. I have my FL die setup to bump the shoulder back to 1.621 and it works great. Now the new rifle is a different story. Using the same new brass it only moved the shoulder forward .001 even with a "HOT" round. Aint much play with this thing!.......

 

[broncman]

Have you used your Hornady gage to check a go gage and verify the reading? A go gage is 1.630 and your chamber should at least be that..something sounds off...

I will check my new lapua brass when it arrives tomorrow.

I make my gages and verify to the go gages.

 

[Down South]

Have you used your Hornady gage to check a go gage and verify the reading? A go gage is 1.630 and your chamber should at least be that..something sounds off...

I will check my new lapua brass when it arrives tomorrow.

I make my gages and verify to the go gages.

No, never checked it with a go gage. Only on brand new and fired brass.

 

[broncman]

Your Hornady gage is most likely off. You can calibrate it with a go gage by setting your caliper dial. Since 1.630 is SAAMI CHAMBER go gage spec, Brass must be under that from manufactures in order to chamber safely etc...

 

[BoydAllen]

FYI the Hornady tool is merely a comparitor that is mislabeled a headspace gauge. You can use one to measure a GO gauge and then compare that measurement to fired and unfired brass if you like, but that does not make it a real headspace gauge. There have been several posts about the confusion caused by Hornady's choice of name for this tool. This is what a real headspace gauge looks like, actually a GO gauge. http://www.westernshooter.com/wp-content/uploads/2009/12/Go-Headspace-Gauge.jpg
There are also NO GO and FIELD gauges, but for your purposes the GO gauge is the one that you would make comparisons to.

 

[broncman]

The first box of Lapua brass measured 1.627. Wow! This is seriously nice brass. NO flashole burrs, nice case mouths!

 

[LongRanger]

Just ordered some new lapua 308 brass for my FTR gun. How much of an accuracy difference does headspace with new brass make? My headspace is in the neighborhood of 1.632. If most new brass is .004-.005 under SAAMI spec of 1.630, how much will this effect accuracy?

I allways resize brass to .002 under my chamber size.

Thanks
Ken

Ken... (I probably ought to stay out of this one but here goes).

Even on high $ brass I find that non-concentric necks are more detrimental to good accuracy than sloppy headspace on new brass. Think about what happens when a neck that is .004 "crooked" goes into the chamber. Depending on how tight the chamber is, especially the neck, the case neck (and maybe even the whole case) can get pushed to one side and bind any where from 0-359 degrees around the chamber. So, you insert one that binds at 3 o'clock, and the next one binds at 10 o'clock....Hellooo? They will probably straighten out on the first shot....just don't use them for record.

FWIW, I find that if my necks aren't beat into shape with less than .001 runout after the second firing, that more firings, trimming, annealing,resizing does not, usually, improve them.

Frank B.

 

[treeman]

catshooter, would you please try and be a little nicer. people that push shoulders back too far are ignorant of the subject not DUMB
thanks, Darrell Blanchard