match rifle head space tolerance

[tensnxs]

how much head space is too much? my newly built Palma rifle in 308 Win measures .0045" over the standard 1.630 'GO' guage. That's .0065" over the virgin Lapua brass.
The bolt closes half way down on the 1.635 guage but not on the 1.636 guage.

what problems will I need to worry about with this set up?

thanks in advance.

Tensnxs

 

[Rustystud]

The SAAMI spec difference between a Go and No-Go gauge is .0035.
In 35 plus years of chambering I have been told and personally found that one should always use "STEEL" Go and No-Go gauges made by the same manufacture. The sole purpose of using gauge is to insure you are within the desired spec. As one is sneaking up on proper headspace the bolt handle will get closer and closer to completely closing on the Go gauge. You must make sure there is not any chips and/or trash in the chamber when you are gauging. I use a nylon bore brush and an air hose. Just at the point when your bolt completely closes on the gauge is when you quit reaming. At that point your bolt should close on the Go gauge and not close on the No Go gauge. Some smiths will stop reaming when the bolt will not close any on the No Go gauge and others will ream until the bolt will fall just a little bit but not completely close. Don't forget your crush factor. Your barrel when it tightens up will close up another .001 to .0015 depending on the quality of your threads. You will find a slight difference in the bolt closing on a gauge and the bolt closing on a piece of virgin brass. You may need to polish the chamber just a bit. With 308s and Lapua Brass, they may be tight in the web area. I like for my 308s to close on the Lapua brass with just the slightest amount of resistence. I like for my spent brass to want to just fall out. If your chamber is put together a little tight your brass will not get as much exercise and last much longer.

RUSTYSTUD

 

[tensnxs]

I did use a set of steel guages from the same make. The bolt closes w/o effort on the "No Go" guage,1.634") but closes half way down on the 1.635" guage. so i figured the head space is about 0.0045". A smith built the rifle for me and this is my first time studying into the topic of 'head spacing'.

thanks Nate!

 

[treeman]

tensnxs,If you watch how much you resize,i.e. shoulder bump or shoulder set back your casses. you should not have any problems. have your smith make you a stub guage from a peice of barrel that has about half of the shoulder of your chamber. he can cut the top end until it reads zero with a peice of your fired brass and you can use it to gauge how much you are pushing the shoulder back. .002" set back is plenty. most military bolt rifles were built with 10 or 12 thousandths excess head space so if the was grit on the amunition it would still chamber. my brother in law gave me some 7x57 brass that had been streched .013" I cut one open to see if it had started thinning back by the head and from 1 fireing it was undetectable. I found a good way to set up a die for sizeing casses is to screw in the die until it touches the shell holder put a dab of lip stick on the shoulder of a lubed case and run it up in the die. keep doing this screwing the die in 1/16 turn until it starts to squish the dab of lip stick. then start using a new fired case until you get the headspace you are looking for. hope i was clear on the procedure. if you are not sure what i was saying send me an email and i'll run through it again for you. best of luck, treeman ,treeman59@cox.net)

 

[TRECustom]

If a bolt will close on any brand of no-go gage, the chamber is too deep. You could go back to the 'smith who built it and see if he gets the same results with his headspace gages. He will.
I would pull the barrel and set it back enough to re-establish proper headspace. In my opinion, for a match gun, headspace ought to be just enough to allow the bolt to close on a new case,even if it can't close on the go-gage). When you check it after make-up, if the bolt won't close on the go-gage, try a new case in it before you break it down. If it will close on the unfired case, check it with several more new cases. If it closes on them, leave it alone. Tight headspace is good on anything except a dangerous game gun.

I would never use a rifle that would close on a no-go gage.

Just my opinion and my way of doing it.

Good luck, Tom

 

[memilanuk]

Actually... I think it depends on whose GO/NO-GO gauges you use.

Here's my experience: Got a brandy new tactical rifle built up in .308 Winchester, by a very reputable gunsmith who specializes in that particular field, using a match chamber reamer from Kiff. The gun shoots little bug holes, but as I was in my reloading room showing someone else how to measure headspace, etc. the subject of GO/NO-GO gauges came up. I happen to have a set of Forster .308 Win GO/NO-GO gauges,I believe they are labeled 1.630 and 1.634 respectively) that I use for setting the barrels on my Savage rifles in .308 Win. Dropped in the GO gauge, bolt closed easily. Dropped in the NO-GO gauge... bolt closed w/ a hint of pressure. Obviously, I was not a happy camper at that point.

I emailed the gunsmith asking if his special match chamber was supposed to close on a NO-GO gauge, and his response was 'No, and it didn't when it left here'. Apparently he'd checked it w/ the GO/NO-GO gauges that came with his reamer,from Kiff) and it had *not* closed on the NO-GO gauge. Here's the trick, though: those gauges had no dimensions written on them anywhere.

So... now the gunsmith wants to know as well what is going on, so he contacts Kiff... short version is that apparently Kiff's NO-GO gauge is made to 1.636", not 1.634" like Forster's. So the gunsmith *had* chambered the gun correctly using the gauges he had in hand... they just didn't happen to agree with the ones I had in my possession. The happy ending was the gunsmith offered to rechamber the barrel using my gauges, which I took him up on. He mentioned that with the new chamber, FGMM ammo chambered pretty tightly. I almost never use factory ammo, even match grade stuff, so it didn't bother me too much.

Anywho, I thought it might be a useful illustration of how the bolt closing on a Forster gauge marked 1.634 or 1.635 is *not* necessarily chambered incorrectly if the gunsmith used a different set of gauges, i.e. those provided by the reamer manufacturer.

YMMV,

Monte

 

[billmo]

Monte, Good info. One would assume that all go and no-go gauges would have a standard and would be closely examined by the manuf.
before they were put out in the marketplace. Q C inside the plant or mill should be looking for out of spec. machinery,loose or worn components) at time of manuf. But quality don't seem to matter anymore man. Bill

 

[tensnxs]

Tom, I feel the same way you do. Though I'd refer my chamber is .001" to .002" longer than the 'Go' guage for reliability reasons. I called up the manufacturers and JGS makes their 'No Go' guage 1.636" and Forster 1.634".

I believe the 'Go" guage is the largest dimension that ammo makers can make their ammo to. and typically they make them about 1 or 2 thousandths shorter.

Monte thanks for that insight. i was told that too. here is my question... how much head space is too much for a 1000-yard competition rifle?

for someone that shoots factory loads or using virgin brass, what would a head-space of +0.0065" do to the performance in a competition?

why do most custom smiths cut chambers to around +.001" on their match rifles? I mean, for someone paying $1,000s for a match rifle done with close tolerance on everything else but the chamber just doesn't make much sense to me. maybe my expectation is too high or just don't understand head-spacing.

what really bothers me is that 3 other factory 308 rifles including a pencil barrel hunting gun have chambers of less than +0.003" measured by the same set of guages.

 

[JayIdaho]

This is not to disagree with any of the previous postings, it is just how some of us set up our 600/1000 yard rifles.
Match the headspace to the dies you are going to use is a good approach. You can FL resize with the shellholder bumping the die and get .001-.002 "shoulder bump" if you set the headpace properly.
Another option: Make your chamber a bit deeper and use the Redding +.002 to .010 TALLER shellholders to fine tune your bump.
These methods work good for some of us. You may have to anneal brass if the shoulder bump is inadequate after the brass begins to harden, somewhat.
Opinoins vary, these are just from someone that does it different.
I will not argue about this, if you don't like it and say so, that is fine with me.

 

[memilanuk]

Bill,

I was in no way insinuating anything about manufacturer quality control, etc. I don't believe that was the case at all... just a matter of different standards - one uses a different number, no more, no less.

tensnxs,

Honestly, it doesn't really make a bit of difference what that chamber measures with your set of headspace gauges. I'd advise you put them away and forget about 'em unless you are chambering a gun or setting up something like a Savage w/ barrel nut.

Really.

Adjust your dies to cases fired in your chamber. It could be undersized, oversized, or somewhere in between and it won't matter a damn after the first firing. Take your fired cases, measure them with a Stoney Point or Hornady comparator, an RCBS Precision Mic, or a barrel stub from the gunsmith, whichever tickles your fancy, bump them back a little,0.001-0.002 for a slow-fire bolt gun works pretty well in my experience) and call it a day. At that point, the only measurement that matters is relative to your fired case dimension - what it is relative to some arbitrary case gauge standard really doesn't affect a thing. Yes, it stinks having multiple guns of the same caliber, all with different headspace values - but thats life unless you do your own barrels or have the same gunsmith do all the work. If you are using a regular 7/8-14tpi press,other than a Forster Co-Ax) the Redding competition shellholders that Jay mentioned work very simply and quickly for this - size a case w/ the +0.010" shell holder, measure to see if it got bumped enough. If not, try the +0.008" one, and re-measure. Once you find the one that gives you the right amount of bump, write it down somewhere - saves on re-measuring when you go to set up the dies again after a long lay off,DAMHIKT!!!).

Now if your sizing die cannot squeeze the case enough - and it does happen - then you might use the headspace gauges to see if it is the chamber or the die at fault. Otherwise, leave 'em in the drawer and get busy loading and shooting!

Good luck,

Monte