The Accurate Reloading Forums
throat angle

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17 August 2017, 19:04
gwahir
throat angle
I need to buy a throat reamer with the correct angle for a 30 cal 210 Berger. Suggestions?

Thanks
17 August 2017, 20:06
dpcd
Bullet noses are secant or tangential ogives. A common throat angle is 1.22 degrees for the 30-06.
I don't know the type of nose for that bullet but you should ask Berger and order a reamer to match.
17 August 2017, 20:46
Duane Wiebe (CG&R)
Gotta keep in mind that different angles can result in different throat lengths
18 August 2017, 02:55
farbedo
Lilja has a good discussion of this on their website along with some calculations for different bullet designs.

Generally speaking 1.5 degrees is a common leade angle on benchrest reamers. However, throat depth is probably more important.

What I have seen on the topic is all over the map from 1 to 3 degrees and everyone has their reasons. Some claim accuracy, others claim pressure, and still others claim throat life for whichever angle they choose. Or some combination.

I would talk with Berger, then talk to Dave Manson. Between those two sources, you will have talked with the bullet guys and one of the top reamer makers.

Jeremy
18 August 2017, 19:54
Duane Wiebe (CG&R)
In my experience, this angle can be a deal breaker.

I had a brand new Brand X reamer for 270 Win, built a rifle for a client...wouldn't shoot worth a s....! Actually replaced the barrel twice with same results. Client was not happy and indeed lost all faith in me, never built him another rifle.

This scene was almost repeated a year or so later with another client. I replaced the barrel but used my old Hartford reamer..viola! damn near a tack driver

Brand X at that time used a "universal leed angle", which was somewhat different than SAAMI.

New reamer from JGS and I was back to being able to turnout accurate 270's.


Like to point out that this was many years ago, Brand X has since abandoned the universal leed angle.....but I still lost a good customer!
18 August 2017, 21:51
gwahir
Yup. Throat depth is an issue. I see this bullet needing at least .35 off the lands. My main objective is getting the base of the bullet ahead of the neck/shoulder junction and avoiding the dread doughnut.
19 August 2017, 02:17
dpcd
Why do you want it to jump over 1/3rd of an inch? Just curious.
19 August 2017, 03:07
Grenadier
Here is a table from Lilja:

THROAT ANGLES IN DEGREES FOR VARIOUS OGIVES

30 CALIBER: (.300″ BORE DIAMETER .308″ GROOVE DIAMETER)
7 CALIBER TANGENT -- 1.74 degrees
8 CALIBER TANGENT -- 1.63 degrees
9 CALIBER TANGENT -- 1.54 degrees
12 CAL SECANT .75″ LONG X .07″ MEPLAT -- 3.40 degrees


I don't know what the ogive is for the Berger 210 grain bullets (they have two shapes) but I'm sure Berger can tell you.




.
19 August 2017, 05:19
gwahir
Sorry about that. Should read .035.
19 August 2017, 06:30
D Humbarger
Most thoaters are 1 degree 30 minutes.



Doug Humbarger
NRA Life member
Tonkin Gulf Yacht Club 72'73.
Yankee Station

Try to look unimportant. Your enemy might be low on ammo.