Throat angle

I think some of the popular Palma Reamers have a 3-4 degree lead, probably to fit that particular bullet style.

I think everything has been tried at one time or another. We all tend to forget that people have been doing this for quite a while..........jackie
 
I was just talking with one of the reamer makers yesterday .
He said that one guy ordered a 4* on a reamer and he couldn't reach the velocity he wanted with the chosen bullet , before max pressure was reached. They reground the reamer to 2* and he was able to reach his chosen velocity.
He went on to say some of the 600 yd. shooters were using a 3/4* lead on their reamer. The reasoning was, that seamed to be the angle of a well worn throat.

Hal
 
Rifleshooter,

In the 1995 Precision Shooting Annual, there is a good chapter on leade angles, throats, etc. IIRC, Mike Walker said the original leade angle for the .222 was 3 degrees a side, 6 included. Dan Lilja opined that one of the reasons leade angles in the neighborhood of 1.5 degrees seem to work well is that the lead angle corresponded well with the ojive on many accuracy bullets.

This is from memory...I'll look it up when I get home.

Justin
 
In a conversation about this I had with Jeff Summers a while back -- when he was still shooting Fowlers -- he remarked that he'd had a reamer ground with a 3-degree angle, and it was "fussy." If Jeff Summers finds it "fussy," it's nothing I want to try. His "fussy" is my "impossible."

I had mine ground with a 2-degree angle -- I was also using the Fowler 66 grain bullet -- an angle Jeff had also tried and found to work well. IIRC, the 66-grain Fowlers were a 6-1/2 tangent ogive. Far more gentle than most BR bullets of today.

When all's said and done though, good bullets are good bullets. I fired a SE regional at 300 yards, using those old Fowlers for HV and LV, and 8-1/2 ogive BIBs in Sporter. My aggs were better with the Fowlers, but I got the small group in Sporter with the BIBs. Well, one match and the driver's suspect, but I'd have no quams about shooting either at 300 yards, or anything shorter. We're back to it's more about what your barrel prefers.

Far as I'm concerned, the only difference with a 1-, 1.5-, or 2-degree throat angle is it makes you adjust your freebore length.
 
Dan Lilja has some information on his web site pertaining to what throat angles match what bullet ogives. I noticed that 1.5 is a match for 9. Perhaps this explains the trend toward double radius ogive bullets, that have a larger number where the rifling engraves. The pointing die that Tom Libby had made, and the late Del Bishop made great bullets with, is a 9 at the back, and a 5 at the front. It has the reputation of not being fussy at all about seating depth. I think that it is because it works kind of like a Morse taper.
 
Gents,

I have the 95 annual in hand. Mr. Walker did indeed make the Deuce leade angle 3 degrees a side. It is also his opinion that throat angle is not important as long as it is shallow enough to prevent shaving of the bullet.

Dan Lilja included a table in his section in which lists the various ogive shapes and their corresponding throat angles. His general conclusion based on this information:

A 7 caliber tangent ogive has an angle of 1.7 degrees
A 8 caliber tangent ogive has an angle of 1.6 degrees
A 9 caliber tangent ogive has an angle of 1.5 degrees

The above is for 6mm caliber only.

A link to the article is below.

http://www.riflebarrels.com/articles/bullets_ballastics/throat_angles.htm

Hope this helps,
Justin
 
Hugh Henriksen ground a 3° per side on a 6mm PPC a few years ago for me. I found the same problems that Jeff Summers found...very sensitive to tune.

My theory went out the window on less ogive to lead contact variation using a sharper throat from barrel to barrel with differing bore diameters. Apparently it is a pressure issue, rather than an alignment issue with the curve of the ogive tangent to the lead.

I had Hugh regrind the reamer to 0.75° per side, but I never got around to trying it.

Greg Walley
Kelbly’s Inc.
 
4Mesh: You might be right. I’ve had a few customers complain about a few chamberings other than a PPC that have a 0.75° lead (I assume to match the secant ogive of VLD bullets). Coincidentally, they too were very erratic performance – drastic changes with even small incremental changes in seating depth. One of these was a 6mm XC.
 
A .75 degree throat per side in a 6mm would be a taper of approx. .2435 to a .236 bore @ 1.5 degree included . That results in a throat length of .2865 assuming no freebore.
I think the angle is relevant to what size the throat starts at and the bore diameter and where you want to seat the bullet with reference to the lands.
The deeper the lands have to go to seat the bullet where you want the less the throat angle will be . I don't think there is any BEST angle only suitable angles for the bullet length and ogive shape , throat start diameter and bore diameter . Once you have a certain bullet you want seated to a certain place in the case neck and the bore then the throat angle is fairly set if you want to keep the throat start diameter to the minimum diametere for the caliber which in this case is .2435 . The bore diameter and the ogive position in the bore is fixed. That's how I understand it anyway correct me if I have missed anything.
 
My experiences mirror what Greg mentions above. When I tried too much angle, pressure went too high and velocity dropped. Shooting a 6BR @ 100/200, that's no big deal. At 1K, it's a big deal. When I went to too much angle, I had the same trouble, but now, added ES issues to the mix. The powder would not burn up cause there wasn't enough initial pressure. Now, I say these things in reference to what "I" say is best for my guns. What others do, that's their business.

PS. My chambers are bored, throats and all. trying various throat angles/shapes was quite easy for me. My findings were, conventional, like Sammi, worked great. Steep or shallow for no good reason did not. Others have reported success with shallow, but I know of nobody who'd done a real steep one that performed well in competition. Steep to me meaning >3/side.
 
Do you use a solid carbibe boring bar for turning chambers? Also, what corner radius on the tip? Do you think the finish is up to par with reaming a chamber?

I have cut a few 6mm PPC this way but using a roughing and finishing boring bar going down to .230 diameter gets a little fussy. Just curious what you have tried and had success with. Got any pics?
 
I don't want to hijack the thread but.

I've tried solid carbide tools inserted into a custom steel holder and thought they sucked for barrel work.

For chambers I did, I made a specific tool for the cartridge. The were all coolant through, indexables using either 120 deg for 30 cal or 80deg for smaller. Radii were .007 and .002. All Circle Machine inserts. All the bars were one piece tool steel holders and bars together, heat treated and drawn. Started with 2" material. Profiled both front and back (as viewed via x axis). All blow chips down the barrel and make big chore-boys in the spindle bore.
For really small stuff, I used a Bokum bar (solid carbide) in a custom holder. I've done 17,22,6, 6.5 and 30. As to finishes, they seemed to work ok for me. How nice do they have to be?
 
4Mesh said:
I don't want to hijack the thread but.

I've tried solid carbide tools inserted into a custom steel holder and thought they sucked for barrel work.

For chambers I did, I made a specific tool for the cartridge. The were all coolant through, indexables using either 120 deg for 30 cal or 80deg for smaller. Radii were .007 and .002. All Circle Machine inserts. All the bars were one piece tool steel holders and bars together, heat treated and drawn. Started with 2" material. Profiled both front and back (as viewed via x axis). All blow chips down the barrel and make big chore-boys in the spindle bore.
For really small stuff, I used a Bokum bar (solid carbide) in a custom holder. I've done 17,22,6, 6.5 and 30. As to finishes, they seemed to work ok for me. How nice do they have to be?
Click to expand...

Very interesting tooling choices. I've always wondered if that guy at AW Warner tool would be interested in making HSS inserts for the little carbide boring bars that are available.
 
I guess I should have been more clear. Yes, I did also try a solid carbide bar once, but I wasn't really referring to that. I used Circle's F series carbide bar with the TDAB-505-CG5 inserts. I found that making my own steel bars from a hardenable material that were profiled to fit the chamber, offered far more stability and no resonance. The tapers on them keep the bar from ringing. The straight cylindrical bars are terrible for that, especially in carbide. They just ring like crazy. I had mine sweated 3" deep into a steel holder, and still it was awful. I probably should have run the holder ID in the internal here, but life is too short for that. It's easier to just make a bar...

I can run my homemade bars in anything and they work perfect.
 
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