Go - No Go


October 11, 2013, 10:51 PM
To summarize, I recently slugged the bore of my 25-06. It measured 1:12 twist. I had been shooting mostly 100 - 120 gr bullets. I was happy, happy, happy.

However, with that twist I discovered I "should" be shooting 75 - 90 gr bullets.

Well since then I have had amazing key holing, getting "impossible" solutions using my Sinclair gage, and other bad stuff. I have several posts about this situation on the reloading section.

I finally bit the bullet and spent the bucks on a Go, No Go, and Field Gage.

My bolt closes on the Go and the No Go gage, and damn near closes on the field gage. With no pressure the bolt is 20 - 30 degrees from closing on the field gage when it stops.

The rifle is a 98K Mauser conversion to 25-06. I purchased on an online auction. The barrel has no marking.

The thing is I was happy as a pig in poop till I started learning stuff.

Do I find a gunsmith, change out barrel, or just restrict my bullets to longer ones?

Though I am broke, safety is paramount.

Thanks for any and all advice!

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October 12, 2013, 05:04 PM
jcinnb, you could have your hands full, hope all the problems are not traced back to a shot out barrel.

F. Guffey

October 12, 2013, 05:58 PM
Are you using SAMMI gauges? A 98K Mauser probably needs mil-spec gauges.

I had to order a specially ground mil-spec field gauge for my Enfield No4 Mk1. The SAMMI no-go and field gauges were basically equivilant to mil-spec go and no-go gauges.

You're probably fine if your bolt's not closing on that field gauge, it would be like not closing on a mil-spec no-go gauge.

October 12, 2013, 06:26 PM
HexHead, 25-06 is not a military chambering. Mil spec doesn't count on this one.

October 12, 2013, 07:08 PM
If you have a 25-06 chamber, more than likely cut with a SAAMI spec reamer, then the gauges are correct. If you are pushing the envelope on your loads, it's possible you are seeing some lug setback that's giving you the excess headspace. More than one M98 and pre 98 has developed that condition from high pressure loads, but yours should be safe even though it's close to swallowing the field gauge. It can be an issue if it has just happened over a short time.
Revisit your loads and evaluate to see if you are pushing maximum on some, and adjust accordingly. And don't set your shoulders back on the brass fired in the rifle, because the fired brass is the size of the chamber.
If you're not getting case head separations, it should be ok, but you need to keep track of any changes by checking the field gauge occasionally.
fguffey has good experience concerning excess headspace, and working with it.

I thought that I would add that the only good way to check the lug seats for setback is to remove the barrel and use a visual check and depth gauges.


Jim K
October 12, 2013, 10:07 PM
I'll probably get heat on this, but headspace has damall to do with accuracy or vice versa. As long as the bolt doesn't close on the Field gauge and there are no signs of case stretching, don't sweat the headspace.

As for accuracy, the best rule is there is no rule. Experiment with loads and bullets and work to refine the ones that show the most promise.


October 13, 2013, 08:39 AM
My loads are never all that hot, just a little north of middle is as far as I get. I just don't know, I am going to local gunsmith Tuesday and pay for an hour of time just to talk this through with rifle in hand. thanks for the replies. Appreciate your time!


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