Measureing a five groove bore

[Dusty Stevens]

Lots of 5R bbls out there willing their fair share of matches.

Even more thats not though. It sells liquor for gunsmiths too

 

[Intheshop]

60* anvil mic or V block for 3 flute,90* for even numbers,and 108* anvil mic or V block for 5 flute.

I use a V block because it's easier to make,and cheaper than an anvil mic. You can use a 1-2" mic in a small precision vise held vertically,with a reasonably accurate home spun 108* V block. Investment about 20$ gets you you a .0001 Brown&Sharpe 1-2 off evilbay.

This is all much to do about nothing.... besides the dead simple to make 108* arrangement.


But if you're talking cast it really doesn't matter what your metrology confirms or specs to. You need to test a few sizes to see what shows up on paper. Put it this way.... even if I measured your slug into .00001's,that dosen't tell you whether a .358 or .359 bullet is going to shoot better? And forget any notion that you're gonna be able to "track" any data WRT another barrel("all odd groove barrels like ? diameter"). It dosen't work that way.

Oh,I'd measure the dang thing,but that's just because there's 5 fluted tooling in the shop. But it would be just for S&G's.... trying a cpl different diameters "over" nominal is still the acid test.

 

[tobnpr]

It has a land opposite the groove so when an attempt is made to measure via conventional mic or caliper the full diameter is not realized

So why not just take a small shim of "X" thickness, bridge the land (which is the groove in the slug) on that side, measure over it- then deduct "X"

Or fill it flush with epoxy, then measure.

This just doesn't seem to be rocket science to me.

 

[jackieschmidt]

Reason #54 to stay away from odd grooved barrels

Even those that make odd groove barrels admit the concept revolves around marketing more than any actual performance advantage.

For us that have been around a while, we have seen a shooter shoot a phenomenal score with a certain configuration and suddenly everybody has to have one.

The truth was that was just a great barrel, and it would have been great in any configuration.

I think one of the more “humorous” episodes in this happened back in the mid 2000’s. A very prominent cut rifled barrel manufacturer was furnishing a lot of winners, especially in Short Range Group Shooting.

many of us who indicate our barrels with indicators in the lands and grooves started to notice that some of our new barrels had groove diameters that were not a true arc. The indicator stylus would dip into what seemed like a “trough” as it traveled in the grooves between the lands.

In the mean time, a very well known shooter from out in West Texas had a couple of these barrels that were giving great performance.

The barrel manufacturer even came up with a name for this “special” groove shape. I can’t remember that name, but perhaps someone else can.

But the truth finally came out. The “special” groove shape was actually the product of the way the were re-sharpenning the tool that produced the grooves in their cut rifled process. From strictly a machinist view, it was a cost cutting attempt to get more barrels from a given tool.

Perhaps they did not think we would notice.

We’ll, long story short, the vast majority of the barrels that had this “special” groove shape were no better or worse than previous offerings. The shooter in question just happen to score a couple of really great blanks.

It wasn’t long after tha the manufacturer ceased doing this, and suddenly all of the barrels had nice round grooves again.

Through the years, we have seen all sorts of “new” ideas hit the market, some manufacturers even build an entire business profile around a certain “shape“of the lands and grooves. PacNor touts their profile that imparts more of a radius at the base of the land, Shilen‘s “ratchet” rifling looks like a buttress profile.

All shoot just fine, but none of it is the holy grail of “Hummer”.

 

[1951]

Thank you all for your replies.
I don't have a CMM, whatever that is, or a 70 degree vee block. I do have a couple 90 Degree Vee blocks I use to measure camshafts, is there a formula or a way to use 45,90,45 vee blocks instead of 70? I can measure down from the top using a deck bridge and a dial indicator gauge or up from the bottom with a micrometer.

Wasn't my intention to start a debate on the merits of one number of rifle lands over another, after all this barrel was made 160 years ago and I don't think anyone was punching one hole five round groups at 50 yards with it. I just want to know what the groove diameter is. The guns shoot a heeled bullet, which seem to always have a diameter the same as the outside diameter of the case. The Remington cases used in1863 are pretty much non existent, but a 44 Colt case will fit the chambers so I'd like to know if a .449 diameter/.427 heel bullet will seal or if it will just bounce off the lands as it goes down the barrel before I get too much more involved in moving from a wall hanger to a shooting firearm.

Thanks again,
Al

 

[1951]

OK, I don't know if this makes any sense at all or if I'm grasping, but.

I made two barrel slugs, one I tapped all the way through the barrel and one just and inch or so then back out the muzzle.

I put the slugs into my V block with a land groove up. (because it's a slug of the rifling I'll call the groove diameter the slug lands and the land diameter the slug grooves.) The groove lands were resting against the sides of the V. I rotated the slug until a groove land was up and there was still groove lands touching the sides of the V. I zeroed my dial indicator on a land at the highest point then I measured the difference between the land and groove positions from the top of the V block. I got .007" I tried it on all five groves and lands with both slugs and got the same seven thou every time. Now I may be making an erroneous assumption thinking the slug is going to be the same height off the bottom of the V block as long as there are two lands in contact with the sides, but upon that assumption I've come to the conclusion the rifling depth is 0.007" or the diameter of the barrel grooves is 14 thou more than the diameter of the lands.

Can anyone see and error in my thinking?

I know by measuring the slugs across from from a land to a groove is .442" and if I add the 0.007" I measured the groove depth to be, I come up with a barrel groove diameter of .449" and a barrel land diameter of .435"
Which seems like a lot, I'm not sure but I think lead bullet rifling is cut deeper than jacketed bullet rifling.

 

[Will Henry]

Sounds good to me. You know, ring gauges are another good way to measure five groove slugs but I think you have come "close enough" with your method and your measurements make sense (always a good indication). WH

 

[Alex Wheeler]

So I assume your looking for this number because you want to size a lead bullet? Im no expert in this area but I have worked up some very accurate lead bullet loads and a little fat wont hurt. If your getting leading go bigger until it stops. Since its a revolver the cylinder is going to determine the slug size anyhow. You can ream them up if they are too small. I think you can end up where you want to be with a little trial and error.

 

[jackieschmidt]

Thank you all for your replies.
I don't have a CMM, whatever that is, or a 70 degree vee block. I do have a couple 90 Degree Vee blocks I use to measure camshafts, is there a formula or a way to use 45,90,45 vee blocks instead of 70? I can measure down from the top using a deck bridge and a dial indicator gauge or up from the bottom with a micrometer.

Wasn't my intention to start a debate on the merits of one number of rifle lands over another, after all this barrel was made 160 years ago and I don't think anyone was punching one hole five round groups at 50 yards with it. I just want to know what the groove diameter is. The guns shoot a heeled bullet, which seem to always have a diameter the same as the outside diameter of the case. The Remington cases used in1863 are pretty much non existent, but a 44 Colt case will fit the chambers so I'd like to know if a .449 diameter/.427 heel bullet will seal or if it will just bounce off the lands as it goes down the barrel before I get too much more involved in moving from a wall hanger to a shooting firearm.

Thanks again,
Al

Sorry we went off on a tangent with the groove discussion. Many of us look at these threads as open discussions, not much different than if we were at the range and someone asks..”hey, any of you ever rin into this………”

Good info is good info, no matter how you come across it.

 

[Dusty Stevens]

I would think youd get close by measuring with calipers, spinning the bullet in the jaws letting it open up freely as it spins

 

[LVLAaron]

Even more thats not though. It sells liquor for gunsmiths too

While I was in one of Gordy's classes - I texted the guy who does my barrels and apologized, and promised to never bring him a 5R barrel again.

 

[RedfootRanch]

Alan,
I picked a CMM up at Harbor Freight for cheap!

CMM?

 

[Alex Wheeler]

I really dont mind dialing in 5r barrels, with my setup it's not any more difficult but I do hate poor quality barrels. When the grooves vary .0003 with ratchet or radius error then you have a job on your hands.

 

[BigGame]

I put the slugs into my V block with a land groove up. (because it's a slug of the rifling I'll call the groove diameter the slug lands and the land diameter the slug grooves.) The groove lands were resting against the sides of the V. I rotated the slug until a groove land was up and there was still groove lands touching the sides of the V. I zeroed my dial indicator on a land at the highest point then I measured the difference between the land and groove positions from the top of the V block. I got .007" I tried it on all five groves and lands with both slugs and got the same seven thou every time. Now I may be making an erroneous assumption thinking the slug is going to be the same height off the bottom of the V block as long as there are two lands in contact with the sides, but upon that assumption I've come to the conclusion the rifling depth is 0.007" or the diameter of the barrel grooves is 14 thou more than the diameter of the lands.

Can anyone see and error in my thinking?

I would do it slightly differently. The 0.007 you found should be an addition to the overall diameter of the circle encompassing the lands. Get the perimeter of that circle. Now calculate its diameter and radius. Diameter=your land-to-land distance. Subtract the radius from your groove-to-land distance (.442) to get your groove-to-groove radius, then double it for your groove-to-groove distance.

 

[TylerFromMS]

I really dont mind dialing in 5r barrels, with my setup it's not any more difficult but I do hate poor quality barrels. When the grooves vary .0003 with ratchet or radius error then you have a job on your hands.

How does yours differ than something like a spider? I just got a lathe and I’m always looking for something a little more user friendly.

 

[butchlambert]

How does yours differ than something like a spider? I just got a lathe and I’m always looking for something a little more user friendly.

It ain't about a spider or 4 jaw or whatever. It how he indicates his barrels.

 

[Alex Wheeler]

How does yours differ than something like a spider? I just got a lathe and I’m always looking for something a little more user friendly.

I dont know that it differs but when you dial in barrels 5 days a week you better figure out a really good method or your gonna waste a lot of time. No different than any skilled labor it just comes with paying attention and experiance. If you think about what people think makes a 4 groove easy to dial in and apply that to a 5 groove problem solved.

 

[DaveTooley]

I dont know that it differs but when you dial in barrels 5 days a week you better figure out a really good method or your gonna waste a lot of time. No different than any skilled labor it just comes with paying attention and experiance. If you think about what people think makes a 4 groove easy to dial in and apply that to a 5 groove problem solved.

I've dialed in probably north of 7,000 5 groove barrels. It's not that hard. Finger tight until It's close. Then once you a zero number gradually tighten each screw until tight. Almost took longer to type this than dialing it in.

 

[WayneShaw]

You can slip a pilot bushing in the bore, indicate off the inside of it to get close as Dave said, then snug down.

 

[Dusty Stevens]

I dont have a problem at all dialing one in. I have issues with the stupid chatter