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Go Gages Belted Magnums

warnera1102

Sergeant of the Hide
Full Member
Minuteman
Feb 25, 2020
322
159
Are go- no go gages on belted magnums only different by 0.002" (no go being 0.002 longer)? I tried to measure the distance from the gage base to the flat and I came up with 0.005" but it is a little difficult to measure with standard calipers.

The reason I ask is I removed my remage barrel to have it threaded for a muzzle brake the other week. I reinstalled the barrel and went to go shoot to make sure everything was working properly to find out my previous load is shooting like dog crap. I know the brake will change POI but the grouping size was terrible.
I went back to make sure my case bottom to lands measurement didn't change and found out it has increased. The barrel only has a few hundred rounds of 7mm RM so I find it hard to believe the lands have moved ( to what i measured another 0.040"ish). I ordered a Hornady OAL gage to make sure over the using a sized case and having neck tension hold the bullet.
 
How did the crown look after the threading? Can you check the bore at the muzzle maybe got damaged during threading process? Depending how hot your loads are 7rm is known for short barrel life.
 
How did the crown look after the threading? Can you check the bore at the muzzle maybe got damaged during threading process? Depending how hot your loads are 7rm is known for short barrel life.
The crown and the threading are perfect. The only thing I dont understand is how the lands moved so much unless the tolerances of the remage barrel and setting of the gages combined to increase the depth.

I had some old 162 gr hornady loads that I shot with it and it shot ragged holes but they seemed to always love a huge jump vs the bergers I am shooting now.
 
No-go gauge lengths are somewhat arbitrary. It's one of the reasons why you can make a pseudo-No Go Gauge using scotch tape (which is usually around 0.002-0.003" thickness) taped to the back of a Go-Gauge. No-Go Gauge dimensions can be anything in between minimum SAAMI spec (Go gauge) and maximum SAAMI spec (Field Gauge).

Your headspace could've theoretically increased by a bit if you didn't torque the barrel back on to the same torque specification it was at previously.
 
No-go gauge lengths are somewhat arbitrary. It's one of the reasons why you can make a pseudo-No Go Gauge using scotch tape (which is usually around 0.002-0.003" thickness) taped to the back of a Go-Gauge. No-Go Gauge dimensions can be anything in between minimum SAAMI spec (Go gauge) and maximum SAAMI spec (Field Gauge).

Your headspace could've theoretically increased by a bit if you didn't torque the barrel back on to the same torque specification it was at previously.
I think you may be on to something.
Originally I used a no go but I tried the scotch tape on my go gage this time. I really didn't think there would be a huge difference between the no go and scotch tape trick.
Thinking out loud here : Wouldn't the score tape tape trick bring the distance in closer vs the no go gage?
 
I think you may be on to something.
Originally I used a no go but I tried the scotch tape on my go gage this time. I really didn't think there would be a huge difference between the no go and scotch tape trick.
Thinking out loud here : Wouldn't the score tape tape trick bring the distance in closer vs the no go gage?
Not quite understanding the question. Are you asking if the tape trick on a Go gauge would be shorter/have shorter headspace than a No Go gauge? If so, it's possible as long as the No Go Gauge is longer by roughly 0.003"-0.004" than the Go Gauge. However if your No Go gauge was made to be 0.001" larger than your Go Gauge, then the scotch tape trick would be longer. If the No Go gauge was 0.002"-0.003" longer than the Go Gauge then you'd get the exact same result as the tape trick.
 
I’ll attack this from a slightly different angle- since what you really identified in the OP was a good load going out of tune.

Depending on how many hundreds of 7mm, yes, your lands could have moved 40k.

Also yes, changing the brake could change how the load shoots. You just chopped, threaded, and changed the weight at the end of the barrel. I’d expect some small load tweaking. I wouldn’t be so quick to attribute those load changes to headspace, as long as it passes a gauge and the brass chambers.