Gunsmithing Howage question

[spife7980]

I got in on the McGowen labor day sale and ordered up a howage in 22 creedmoor. I finally tried to go and install it and Im running into something that I have never encountered in my limited experience, and it may be just fine, but I want to ask the smiths first.

I put the go gauge under the extractor and threaded the barrel in until it stopped on the go gauge... only it didnt stop on the go gauge, it bottomed out on the bolt nose. I have colored the bolt nose in sharpie as well as the barrel counter bore and you can see where its rubbing.
Blacked

Rubbed

In measuring the counter bores from the factory barrel to the new barrel and I have ~.020 of difference. The old barrel measured .136" of counter bore depth and the new barrel measures .117 of counter depth. With the go gauge in and measuring its protrusion from that counter bore depth in the old barrel I had .1385 and in the new barrel I have .1195

So that tells me why I was bottoming out. The relative difference in go gauge protrusion was equal between the two, its just where their absolute position is in regard to the bolt face thats the issue I think.

Next I wanted to know how much short the go gauge was I screwed the barrel in until it just touched the bolt nose and moved it out ever so slightly and tightened it down. With the barrel in that spot the bare go gauge measures 1.690 oal, with 2 pieces of tape at 1.6945 and the bolt still closes. 3 pieces of scotch tape measures 1.6975 and thats where the bolt finally bottoms out on the gauge and the handle can no longer fall.

Do we think that .007 over the go is bad? That would fall right in between the nogo and the field gauge (if I had them). Since this is a wild cat of sorts (well, at least nonsaami) I will be reloading only so I suppose is do we think that extra growth will have a negative impact or will be it just fine after its initial firing stretch.

 

[spamassassin]

How deep is your bolt face from the nose? Looks like your bolt nose isn't square to the breech. It only knocked the sharpie off of part of the recess.

 

[spife7980]

Good question and I noticed that as well... the left/top lug is where it would appear to be out of shape based on the rub but I figured that nose clearance would/should have been accounted for in the counterbore depth as it seems thats how it was in the factory barrel.

Im showing around .1235-.125 from the bolt face to the end of the bolt nose.

In measuring the overall bolt body length with firing system removed Im getting 5.837-5.838 from the rear of the bolt body to the end of the nose. So that seems like the bolt body is straight and square.
I dont really have the tooling to measure this properly but from the rear of the lug to the bolt nose Im getting ~.6565 on both lugs (+/- .001 with my range of measuring error).

Im measuring from the action face to the lug recess Im getting 1.235-1.236.

 

[spife7980]

Ive also thought about taking some lapping compound and trying to see if I could lap it clear but Id rather not lap the bolt nose if its the barrel. Maybe a bit of dremel sanding pad to take that counter bore down a smidge. But Im still waiting to hear back from McGwoen before I go and do any of that.

 

[spamassassin]

I got the McGowan barrel nut on my rifle but because of the bolt-nose recess I dropped the whole works off to the smithy when I was having the thing set up. Guess that got me out of this issue. /me wipes forehead and says phew. In any event, if I were McGowan I'd have you send in your bolt and the barrel and set it up right for you.

 

[whatsupdoc]

The variation between the two looks extreme.
Send the barrel back, if I remember correctly you should have like .008-.010 clearance between the barrel and the bolt nose.

 

[spife7980]

That’s what I thought too, it should have .010 of clearance between the nose and the breech. I don’t necessarily mind having .001 though, it’s just that .001 of clearance leaves the go gauge .007 short, unscrew that to the proper clearance and the go gauge would be .017 short which is way too much.

 

[whatsupdoc]

.001 clearance will not work, when the chamber gets hot you may not be able to close the bolt.

 

[spife7980]

Yep, and as it’s a hunting rifle I would want a grain of that south Texas sand blocking it up either. But if that alone is the issue then maybe I wouldn’t care too much. But that plus the headspace problem compounds the issue which is what I was trying to get at, we are in agreement.

 

[Praeger]

Here's the build sheet from Gavin Toobe's Howa 1500 re-barrel. It looks like the bolt nose recess on his build (0.140") is much closer to your factory barrel than the (0.117") on the new barrel. The bolt nose recess on your new barrel needs to be deepened. Don't worry about the uneven rub marks on the Sharpe. It's not supposed to touch and the critical interface is the back of the bolt lugs to the lug abutments.

 

[spife7980]

They have sent me a return label, I just have to get to a printer and then drop it off.

 

[spife7980]

Shipped it back Monday when I got to a printer finally for the label, it’s on its way back now today. Pretty good turn around.