Forster 1.630 Go Gauge 308 cal.

C

cw308

New member
Checked the Go gauge in the RCBS Precison Mic , the Mic zero is .004 less then the 1.630 Go gauge . Checked the gauge in the Hornady comparator , it reads 1.625. The Go gauge closes in my chamber with no resistance. When sizing my cases & testing the case in my chamber , a perfect fit with very little resistance measured with the Mic is .0015 Does this mean my chamber is longer then spec. on Go gauge . Or should I just resize to that perfect fit and forget about the numbers , that seem to be all over the place. The only gage that is the same is the Lyman case headspace gage, Go gauge was even with the top step of the Lyman gage
 
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The go gauge represent the longest cartridge that still meets saami spec. It is 0.004" with reference to your mic.

Your round is 0.0015", and your chamber is slightly shorter, say, 0.001". That means certain commercial rounds may have difficulty close the bolt on.

Big problem? Perhaps, if you shoot commercial ammunitions. No problem at all if you hand load. You just size your case to fit your chamber. In fact, I have never used any gauge on any of my rifles, and I routinely have 20 loads out of a batch of new brass. Gauges to me are useless.

BTW you may not want to let your buddy shoot your hand load in his gun. It could have excessive headspace.

-TL
 
tangolima
Thank you for answering my post. I was hoping all the case measuring gages would have the same measurement as the Go gauge 1.630 When sizing my fired cases back to 0.0015 " found that length by using the bolt body only, no ejector plug or pin assembly,against a sized case. I use the Mic. to check the F/L sizing dies reading for repeat sizing, I only shoot my own reloads , I would like to know what the exact length of my chamber is. Question, if the Go gauge is 1.630". I placed a piece of masking tape on the base of the gage, it didn't chamber. Measured the tape thickness, measured .004". If I place something .002 an it Chambers like my sized case, would I be correct in thinking my chamber is 1.628" tangolima I am reloading for benchrest only , Rem.700 308 caliber. How are you sizing your brass without a gage in checking headspace. I always ask reloaders their system. Thanks again , Chris
 
The go gauge represent the longest cartridge that still meets saami spec.
Click to expand...
Actually, all of the go-gauges that I've seen represent minimum SAAMI chamber dimensions, 1.630" for .308Win.

cw308, I would trust the go-gauge way before I would trust the Precision Mic or the Hornady comparator. I went down this same route with my new (at the time) PM not zeroing out on my Forster go-gauge. I measured 2 different gunsmiths' Clymer go-gauges with the PM and got the exact same reading as with my Forster gauge, so I trust my gauge, but that's your decision to make.

The Hornady comparator is exactly that, a comparator, not an absolute gauge. I would be shocked if it read exactly 1.630" on a .308 go-gauge.

If your go-gauge measures -.004" with your PM and a case that "perfectly" fits your rifle's chamber measures -.0015" with the same PM, that tells me that your rifle's chamber is .0025" longer than the go-gauge, or 1.6325". That is within the SAAMI spec of 1.630-1.640". In that case, the bolt should close on the go-gauge with no resistance from the gauge, just like you said it does. The simplest way to verify that the rifle doesn't have excessive headspace is to test it with a no-go gauge.

A caveat here is that I would expect the base of the go-gauge to be even with the bottom step of the Lyman gauge, not the top step. My Forster 1.630" go-gauge is flush with the bottom step of a Dillon cartridge gauge.

Edited to reflect measurements as clarified by OP in later post.
 
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SAAMI cartridge 1.634 - 0.007"
SAAMI chamber 1.630 to 1.640"

That means there is overlap.
A 1.634" cartridge meets spec.
A 1.630 chamber meets spec.
--------------------------------
0.0040" of interference
Try closing a bolt on that.
 
higgite
Thanks , I feel better. My case measurement is minus 0.015 on the PM the Go gauge is
- 0.004 on the PM . I will double check the Lyman gauge with the Go gauge when I get home and get back to you . Thank You
I read a post from JeepHammer about trimming a case to the datum line to keep as a reference mark. Makes good sense to me, I'm going to try it. My cases get wider & shorter after firing, by bumping back the fired case 1 or 2 thousands I would have to much space. That's why I use a bolt body only to feel bolt lift & close with a slight resistance to get that zero case headspace measurement. Thanks again . Chris
 
Clark
I added tape to the back of the Go gauge, wouldn't chamber, the masking tape was to thick .004 I was hoping all the gages would read the same as the Go gauge. The Precision Mic read the gage -0.004" my sized cases are -0.0015 that is perfect for my chamber. Thanks for the info. Chris
 
cw308 said:
tangolima
Thank you for answering my post. I was hoping all the case measuring gages would have the same measurement as the Go gauge 1.630 When sizing my fired cases back to 0.0015 " found that length by using the bolt body only, no ejector plug or pin assembly,against a sized case. I use the Mic. to check the F/L sizing dies reading for repeat sizing, I only shoot my own reloads , I would like to know what the exact length of my chamber is. Question, if the Go gauge is 1.630". I placed a piece of masking tape on the base of the gage, it didn't chamber. Measured the tape thickness, measured .004". If I place something .002 an it Chambers like my sized case, would I be correct in thinking my chamber is 1.628" tangolima I am reloading for benchrest only , Rem.700 308 caliber. How are you sizing your brass without a gage in checking headspace. I always ask reloaders their system. Thanks again , Chris
Click to expand...
I don't own any gauges, mic, or comparator, because I am cheap. I progressively lower the sizing die, and keep checking it in the rifle chamber. I stop when felt resistance disappears. Then I have. 001 to. 002" head clearance.

I shoot mostly milsurp. Their chambers are almost all over sized. No point checking them with gauges. I hand load over a dozen different calibers. I'd go broke just buying the gauges and stuff. Not sure it is good enough for bench rest, it is no problem for brass life. 20 loads, give and take.

-TL
 
My case measurement is minus 0.015 on the PM the Go gauge is
- 0.004 on the PM .
Click to expand...

cw308, I took the case measurement in your OP to mean +.0015". I have now edited my earlier post #4 to reflect the -.0015" measurement.
 
I zero my gages meaning when I close the gage the reading is 'ZERO!', after that I am ready to go. I also have an inline, angle, butt grinder. I know that is confusing but if I want a tool that has an angle, flat end with a taper in the middle I can grind them all day long.

In my opinion you guys are using too many standards, I have one, it starts with 'ZERO!'.

F. Guffey
 
F.Guffey
The RCBS Precison Mic. Screws down past the zero mark . I felt the zero mark would be 1.630 same as the Go gage. It was .004 less when installed in the Mic.
 
So now you have a good known in the headspace gauge. Typically for a .308 Winchester the Go gauge is 1.630" and the NoGo gauge is 1.634 with 1.638 being a "Field" gauge. Buying gauges can get a little expensive so here is a simple little trick you can try with your rifle. You know the rifle bolt closes on a Go gauge. Find yourself a hole punch. the kind used in stationary for punching holes. A typical hole punch punches about a 0.250" hole. Get some good accurate shim stock, stainless steel preferred in 0.001, 0.002 thickness. All you need is some decent quality. Punch a few holes, a simple hole punch will punch out stainless shim stock. Make sure the punched out pieces are flat. Place a small (as in tiny) dab of grease on the head of your Go gauge and add pieces of the punched out shim stock. So if I add a .005 piece of shim stock to my 1.630 go gauge I am now at 1.635 or about .001 over a NoGo gauge. On a good chamber the bolt should not close.

While this is not quite, to use a highly technical term, dead on balls accurate, it will afford a good idea less adding more expensive gauges. Quality shim stock should be available in any good hardware store or from distributors like McMaster Carr Supply.

Ron
 
Reloadron
I tried that with a piece of masking tape on the back of the go gauge, it didn't close . the tape is .004 thick. Bought the Go gauge hoping all my gages would measure the same 1.630 they didn't
 
That's the point I've been trying to make,
Chambers are often 'Long' and/or 'Sloppy' (oversized around).

You want the case very slightly 'Short' for the headspace you have,
Just enough to let the bolt close unrestricted.

You are using DIES/PRESS to size the brass, don't make the bolt/chamber do it!
That's REALLY hard on the bolt locking lugs, Especally after a day of shooting and the carbon is grinding away at bolt locking lugs...

Some guys prefer SLIGHT compression, but that takes INTENSE brass control to produce the SLIGHT part, I've seen idiots hammering the bolt closed with a hammer before, and that NEVER turns out well.
 
CW 308:
Reloadron
I tried that with a piece of masking tape on the back of the go gauge, it didn't close . the tape is .004 thick. Bought the Go gauge hoping all my gages would measure the same 1.630 they didn't
Click to expand...

Yes, but on the bright side you now have a good reference. You now accurately know the error of for example your RCBS Precision Mic or your Hornady LNL Case Gauges. So for example if your RCBS gauge reads -0.004" you know that 1.630" is in fact going to read 1.626" on your RCBS gauge. The fact that the Hornady and RCBS gauges had the error they had really does not surprise me. I just note any error of mine right on the boxes. :)

Ron
 
Bought the Go gauge hoping all my gages would measure the same 1.630 they didn't
Click to expand...

I am the fan of the standard and I am the fan of verifying. First I would suggest verifying the gage. After verifying I would move on to using a comparator.

F. Guffey
 
tangolima, higgite, Clark, F.Guffey, Reloadron, JeepHammer. I thank you ALL for letting me pick your brains. As always a wealth of information & putting my mind at ease. Thanks again Chris
PS When I had my barrel replaced & action trued, I have a card from the gunsmith with specs. One was headspace .0015 .
A chamber for a 308 is 1.6300. Is mine 1.6315 correct ? This seems that my measurements are correct, based on your helpful information, with trial & error all makes perfect sense.
 
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When I do a barrel/chamber job, I always make a case gauge with the exact same reamer I used in the barrel.
This gives the owner an EXACT copy of his chamber to work from.
 
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