Throat pics

[FrankG]

Hmm.. I'd like 4R 30 cal tubes

Not happening!

Nothing to be gained...accuracy, barrel life etc...nothing to be gained except making more tooling and charging the customer more money.

5R has proven to help fight bullet failure as well as help the flight of the bullet. Both by the Army and one of the ammo/bullet makers a few years ago.

 

[FrankG]

Hi Frank,

There has been some debate on this forum recently about whether or not the reamer pilot is supported while chambering 5R barrels, What is your opinion on this? I would assume the 4R would not have this perceived problem?

Debate away!

Guys say this and guys say that about the support and the odd number of grooves like in the 5R. If it really does happen....it's nothing in my opinion that is really measurable and or effect anything accuracy wise. NOW THE CAN OF WORMS IS OPEN!

We ourselves chamber something to the tune of a 1000+ barrels a year. If it was a problem we wouldn't offer it to do the work! We chamber ammunition test barrels besides building/rebuilding guns. Just on the test barrel side of things....4 groove, 6 groove, 5R and 5 groove conventional and 8 groove are the most common.

Just on 5.56 and 7.62 and 50BMG barrels. Before we ship them out to the Gov't the chambers have to be checked with 10 different ball gauges for size. In some cases like on the 5.56 barrels...we are only allowed a total tolerance of +.0008" for two of the ball gauges. We've done more than just one or two test barrels with 5R rifling and haven't had a single one rejected back to us because it was out of spec.

Also for ASR....the spec. is 5R rifling for the 308w/7.62 nato barrel, 300 Norma and 338 Norma.

If the reamer is pushing off or not cutting the chamber concentric we don't see it per say.

 

[Will Henry]

To back up what Dave said....

It's not ratchet rifling. That is 5R it just looks different with how the scope is looking into the barrel. Angle etc....

We don't do ratchet rifling. Never have and never will. Guess I should never say never!? I'll say never in this case.

OK. It's kind of one of those "looks like a duck, quacks like a duck" things! Two of my ratchet rifled barrels look just like that, complete with the little flat on top of the lands. I was just curious is all. The other RR barrel is a very early one and is much more rounded than the newer ones. All shoot fine; just like the conventionally rifled barrels (whether cut, buttoned, or hammered) I have. I noticed the 5 grooves but didn't make the connection here. By the way, I have a button rifled 5R blank in the vise that is not as smooth as that one. Very nice. WH

 

[Will Henry]

If the reamer is pushing off or not cutting the chamber concentric we don't see it per say.

I have not experienced this except when cutting the throat separately, with a six flute reamer. I circumvented this by using spiral fluted throaters and that seemed to work. With an integral throater, it seems to be a non-issue since the body of the reamer supports the neck and throat. WH

 

[Jud96]

Why no 3 groove barrels? @FrankG

 

[Sniperhandle]

Debate away!

Guys say this and guys say that about the support and the odd number of grooves like in the 5R. If it really does happen....it's nothing in my opinion that is really measurable and or effect anything accuracy wise. NOW THE CAN OF WORMS IS OPEN!

We ourselves chamber something to the tune of a 1000+ barrels a year. If it was a problem we wouldn't offer it to do the work! We chamber ammunition test barrels besides building/rebuilding guns. Just on the test barrel side of things....4 groove, 6 groove, 5R and 5 groove conventional and 8 groove are the most common.

Just on 5.56 and 7.62 and 50BMG barrels. Before we ship them out to the Gov't the chambers have to be checked with 10 different ball gauges for size. In some cases like on the 5.56 barrels...we are only allowed a total tolerance of +.0008" for two of the ball gauges. We've done more than just one or two test barrels with 5R rifling and haven't had a single one rejected back to us because it was out of spec.

Also for ASR....the spec. is 5R rifling for the 308w/7.62 nato barrel, 300 Norma and 338 Norma.

If the reamer is pushing off or not cutting the chamber concentric we don't see it per say.

Thank you Frank, I was curious as to what you thought about it, Thanks again, Mark

 

[Dgd6mm]

That's beautiful!

This was exactly what I said out loud just before I read your postl

 

[BoydAllen]

Damn Dave! beautiful work.

 

[FrankG]

Why no 3 groove barrels? @FrankG

One is tooling. The wider the groove….the wider the cutting tool needs to be to fit the pocket in the rifling head. So a rifling head that can hold a 4 groove tool, a 5 groove tool and a 6 groove tool….will not hold a 3 groove tool.

So your looking at several thousand dollars in tooling per rifling head. So we need a rifling head just for the 3 groove. If there is real no demand for it we can’t justify tooling up for it. Unless possibly the customer is willing to flip the bill? No you don’t get the tooling!

No gain in barrel life. No gain in accuracy. If I recall correctly back when we were at Krieger we made several barrels for 30cal Palma for Mid Tompkins. Accuracy was great. Ran neck and neck with the 4 groove barrels we made but the 3 groove coughed up like 50 to 100fps in velocity loss. Mid said after 800 yards due to the velocity loss with the 155gr bullets out of the 308win….everything went to hell because he couldn’t keep the bullets above the speed of sound. Remember these where tight bore 30cal barrels. You could probably play with the bore and groove dimensions to help with the velocity loss but if there is no gain here….

So for all practical reasons if no gain anywhere…..why do it?

 

[INTJ]

I like 4 groove cut barrels, as do a very large number of my fellow 1K BR shooters. They chamber well and shoot exceptional. Some think the 6mm bore is not optimum with 5R rifling. I have no idea. All I know is the 4 groovers work very well and I see no reason to change.

They make me chamber a lot of 5R barrels at work. Usually, the little "u" shapes at the beginning of the rifling go away with enough RPM--somewhere around 250-340, which is about the RPM JGS recommends for HSS. With carbide and a flush I guess we could easily go 500 rpm and never see anything but nice square cuts.

BTW, I don't pretend to know 1/100th of what @FrankG and @DaveTooley know about barrels and chambering.......

 

[FrankG]

Why no 3 groove barrels? @FrankG

Plus if the 5R helps the flight of the bullet and overall accuracy…..again why offer the 3 groove?

 

[FrankG]

I like 4 groove cut barrels, as do a very large number of my fellow 1K BR shooters. They chamber well and shoot exceptional. Some think the 6mm bore is not optimum with 5R rifling. I have no idea. All I know is the 4 groovers work very well and I see no reason to change.

They make me chamber a lot of 5R barrels at work. Usually, the little "u" shapes at the beginning of the rifling go away with enough RPM--somewhere around 250-340, which is about the RPM JGS recommends for HSS. With carbide and a flush I guess we could easily go 500 rpm and never see anything but nice square cuts.

BTW, I don't pretend to know 1/100th of what @FrankG and @DaveTooley know about barrels and chambering.......

The only exception I make to the 5R barrels is in 6mm but in regards to the short range 6PPC bench shooters. Those short jacket 65 to 68gr bullets and it’s worse with the boat tail bullets. There isn‘t enough bearing surface on the bullet for the lands to bite the bullet and drive it properly. I’ll tell you the best it will shoot is upper .2xxs to flat .3xxs. That’s all you will get out of them. So in this case a conventional 4 groove or 5 groove.

Now stay with 6mm but go to long heavy bullets like 95gr and heavier like the 107smk, 105’s, 108 and 110gr etc….give me a 5R every time.

 

[JMA]

The finish with HSS reamers will vary some. Under magnification the cutting edge on a HSS reamer looks very rough. Different grinding wheels are used on carbide which leads to a better finish. 50 or so rounds down the barrel and things are smoothed up. Flush systems can speed things up but I'm not sure we get a better finish using them. I take .020" to .040" out on the last pass and am not concerned about chip evacuation.

When I worked in a machine shop we found finishes varied greatly with differant brands of HSS end mills on cnc machining centers. Some of them you could feel the roughness by running finger nail down the cutting edge. Back in the 80's + 90's Osg was by far the best.

 

[clowdis]

Dave, that is some nice work, really impressive! Also, that ain't no $60 borescope camera. What do you use?

 

[LVLAaron]

Dave, that is some nice work, really impressive! Also, that ain't no $60 borescope camera. What do you use?

jewelers loupe and iphone

 

[DaveTooley]

Dave, that is some nice work, really impressive! Also, that ain't no $60 borescope camera. What do you use?

Samsung S20
No loupe
Sometimes you just have to try something different

 

[LVLAaron]

Samsung S20
No loupe
Sometimes you just have to try something different

I'm gonna frame them and hang them in the shop.

 

[Alex Wheeler]

Right now my favorite barrel for a 6mm is probably the 4g gain twists I have been getting from Bartlien. But I have actually grown to prefer 5r for anything bigger.

 

[V35]

I’m beginning to second guess my next build. I have a Bartlein 1:8.25 to 1:7.5 gain twist 5R for a 6GT build. I planned on shooting 108 ELDX’s in it.

 

[tthomp302]

I’m beginning to second guess my next build. I have a Bartlein 1:8.25 to 1:7.5 gain twist 5R for a 6GT build. I planned on shooting 108 ELDX’s in it.

why are you second guessing? im doing the same exact thing minus the gain twist. However the gain twist is an amazing thing too.