Go gauge almost doesn't go

YippeeKiYoRed

Messages
43
Reactions
42
Bought a used bolt-action .308 WIN rifle. Tested it with go and no-go gauges. Go gauge went in but just barely. No-go did not go at all. Tried chambering a couple of rounds, both commercial and handloaded, and they all chambered without difficulty. Seems like should be good to go. Anyone see any issues?
 
Messages
352
Reactions
655
Measure your loaded brass and compare it to your go gauge.
Usually new brass a is a few thou smaller.
You have minimal initial case growth which is very helpful for long brass life.
 
Last Edited:

osprey

Messages
2,825
Reactions
5,959
I have a savage 308 with a chamber cut to minimum dimensions. No problems with most factory ammo but you will have to pay attention if you reload for multiple 308 rifles. For example I bump shoulders back .002 -.003” for a couple military 308 rifles and they will not fit in the savage 308 bolt gun. Moving forward I may find a happy medium for shoulder bump that will fit all my 308 rifles. For now I just keep brass separate and have different sizing dies set for each.
 

Gomer

Messages
36
Reactions
28
In most cases, I don't use a go gauge, only the no-go gauge, unless I'm trying to diagnose a problem. You probably already know, the no-go gauge is machined to be just over the maximum size that the chamber specification will allow, and is used to confirm that the headspace is not too big/long. If the bolt still closes on a no-go gauge, then that indicates that the headspacing is too much. Likewise, the go gauge is the minimum headspace based upon specifications for that chambering. In the case of excessive headspacing, one might experience too much case stretching, or even case ruptures or other catastrophes because the chamber is too long. However, in the case of too little headspace, the end result may be that the bolt won't close. From my perspective, if the chamber/headspace is tight, it doesn't really matter as long as the ammo I'm using chambers properly. The benefit to a go gauge fitting properly is that your more likely to be assured that any ammo that is within spec will chamber. Personally, I would rather have a rifle that the go gauge just fits because it tells me that chamber is the smallest possible and still be within specs, and theoretically still chamber any (in spec) ammo you may come across. A chamber/headspace will grow, but it will never shrink! And when you say go gauge went in "barely", I presume you meant that you could feel some resistance when closing the bolt, but you didn't need to beat it closed with a hammer... :)
 
Messages
862
Reactions
984
Interesting issue. I 'discovered' that my reloads for the .308 would not work, or were hard/impossible to chamber in both bolt guns and LR 308s with 'match' chambers. Commercial brass and steel case were fine. But my salvation is a PTR 91 which eats almost anything. Going forward I will have to bump the cases back to fit the bolt guns and the LR's. Bottom line is to use commercial (factory) or fine that sweet spot to fit in multiple guns.
 

ma96782

Messages
10,611
Reactions
17,899
There is a balance/finesse on how to do it.

I remember that time......
When I brought along my gauge set intending to buy a used bolt action Mauser sporter in 30-06. I showed the owner the gauges and told him that I intend to "test" before buying.

He grabbed the go gauge and just "ran the bolt home".

Awwww.....

Thas_NOT_how_this_works.jpg

Aloha, Mark
 

YippeeKiYoRed

Messages
43
Reactions
42
Gomer: "...didn't have to close it with a hammer." True, but it was tight.
ma96782: My LR308 has a loose chamber that feeds anything. My 308 bolt guns are much tighter. It's noticeable with Lake City NATO brass. More on that some other day.

Part of my concern was discovering light rust in the chamber and bore when cleaning it. Hence being cautious and using both gauges. Cleaned the chamber with a brass chamber brush. Used some JB bore polish on the bore.

3/4" and 7/8" groups @ 100 yrds using IMI Match 308 with 168 gr bullets. I think I can bring that down to 1/2" using 175 grain SMKs and VV N140 powder.
 

Gomer

Messages
36
Reactions
28
I was being a smart-aleck about the beating with a hammer! I wouldn't be surprised if the go gauge "fits" better now that you have the rust cleaned out of it. I'm tickled when I find one that shoots 3/4" groups - sounds like you found a winner!
 

po18guy

Messages
3,567
Reactions
7,784
Gomer: "...didn't have to close it with a hammer." True, but it was tight.
ma96782: My LR308 has a loose chamber that feeds anything. My 308 bolt guns are much tighter. It's noticeable with Lake City NATO brass. More on that some other day.

Part of my concern was discovering light rust in the chamber and bore when cleaning it. Hence being cautious and using both gauges. Cleaned the chamber with a brass chamber brush. Used some JB bore polish on the bore.

3/4" and 7/8" groups @ 100 yrds using IMI Match 308 with 168 gr bullets. I think I can bring that down to 1/2" using 175 grain SMKs and VV N140 powder.
Very good accuracy. Excellent starting point. You may know all this, but in case, a tight chamber is, IMO, to be preferred to a slightly deep chamber. You can set your resizer and seating depth to extract the max accuracy from the combo. A tight, round case with a centered bullet helps maintain bullet coaxiality. Then, once you have the load, you can play with seating depth.

As to brass: LC - essentially all military - brass is thicker and somewhat softer than commercial and that may account for the chambering differences. This is also claimed for Federal Gold Medal Match cases.

If you have tight extraction, you might JB polish the chamber to smooth it up just a tad. Overall, it sounds very good.
 

Upcoming Events

Oregon Arms Collectors May Gun Show
Portland, OR
Rimfire Challenge
Canby, OR
Wes Knodel Gun Shows
Redmond, OR

Latest Resource Reviews

New Classified Ads

Back Top