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chamber throat angle

LCazador

LCazador

Competitive shooter and reloader for 50 years+
Gold $$ Contributor
I must be getting bored with the ordinary so I thought I'd try fixing something that doesn't need fixing, LOL! Has anybody tried a chamber reamer with a different throat angle than the default 1.5 degree match throat angle? I'm looking to try a steeper angle on my 6X47L 40' chamber reamer for the longer ogive bullets. Maybe some of the bullet and reamer makers can expound a little on this. Also thoughts on throat longevity with a steeper angle vs. shallower angle?
 
Id talk to your favorite reamer maker before you think too much about it. Theres been a ton of experimenting over the years, lots of useless reamers in drawers, and the reamer makers are the only ones that have the compiled info in one place and can save you a ton of money- kiff more than anybody but cary at jgs also knows whats going on.
 
Back in the early eighties when I was shooting score, my brother-in-law shot score & group and shot very well against the best and I know that he as well as many others experimented with everything imaginable trying to gain an edge. I know that throat angles were among those experiments. all I can tell you for sure is all of them returned to a 3" included and got back to winning. :)
 
Sorta related...I've been wanting to try a reamer with say a 15° bevel at the case mouth rather than the standard 45°. Anyone have any thoughts on this?
It would smooth that transition area and possibly improve barrel life, are my thoughts. It would also reduce the freebore area so that will have to be factored into the exact angle for a given freebore.
 
Chuckhunter said:
Back in the early eighties when I was shooting score, my brother-in-law shot score & group and shot very well against the best and I know that he as well as many others experimented with everything imaginable trying to gain an edge. I know that throat angles were among those experiments. all I can tell you for sure is all of them returned to a 3" included and got back to winning. :)
Click to expand...
There's no doubt that the 3" included angle is a winner in a 6PPC or 30 BR as those bullets usually fall into the 6-9 ogive range which the 3" is designed for. I'm thinking along the lines of increasing that angle for 13-15 ogive bullets like the Bart's Hammer's or Gungenir's.
 
Dusty Stevens said:
Id talk to your favorite reamer maker before you think too much about it. Theres been a ton of experimenting over the years, lots of useless reamers in drawers, and the reamer makers are the only ones that have the compiled info in one place and can save you a ton of money- kiff more than anybody but cary at jgs also knows whats going on.
Click to expand...
Kiff did that reamer for my 6X47 and we talked about it. Reamers don't have to lay in drawers unused I've sent several back for regrinds. Like I said in my post the 1.5 degree angle has worked quite well for me but I'm looking to try something different! Maybe I have too time on my hands, LOL! Thanks for your post Dusty.
 
While the 1.5 degree will accommodate most of the longer rounded ogive bullets you can create some improvement with the Hybrids and the more angular ogives at the front of these bullets by switching to the 3/4 degree throat. I've had Dave Manson make a few of these reamers and modify a few existing reamers trying to save a little time.

I do not have any definitive data yet as other more timely projects are in front of this. Although, it appears that when using some Hybrids in the heavy for caliber category, there is some improvement in group size and consistency. I have rifles chambered using both styles of throats so when shooting comparisons, I'm not having to make another barrel. I shoot them back to back, same day, nearly the same time. The reamers are complete, no separate throating reamers.
 
johara1 said:
Look at the 110 SMK.613 BC. and it matches the 1.5 degree throat angle..... BTW I shoot Barts bullets and I have great success with his 15 ogive 105 with a 1.5 lead... jim
Click to expand...
Jim, I have no doubt that you have had great success with the 1.5 lead. I have too! My question is has anyone tried anything different and what was your experience?
 
Last edited:
Kurz said:
While the 1.5 degree will accommodate most of the longer rounded ogive bullets you can create some improvement with the Hybrids and the more angular ogives at the front of these bullets by switching to the 3/4 degree throat. I've had Dave Manson make a few of these reamers and modify a few existing reamers trying to save a little time.

I do not have any definitive data yet as other more timely projects are in front of this. Although, it appears that when using some Hybrids in the heavy for caliber category, there is some improvement in group size and consistency. I have rifles chambered using both styles of throats so when shooting comparisons, I'm not having to make another barrel. I shoot them back to back, same day, nearly the same time. The reamers are complete, no separate throating reamers.
Click to expand...
I like the way you did that comparison. Side by side. I'm curious about throat erosion. Are both chambers the same?
 
Yes, both chambers are the same except for the throat angle. The side-by-side comparison can be fraught with small disparities because of manufacturing but I tried to make everything as close to the same as possible. I explained the idea to the reamer maker and the barrel maker so we were all on the same page right from the start.

Throat erosion is one of the questions we all have regarding this test. We'll know more when I get the decks cleared of work so I can play!;):D
 
Has anyone here cut open a used barrel, and measure the throat angle after wearing from use? I would think that the angle would change over use, but would it start to follow the angle of the bullets that are being used?
 
Jim, like I said in my original post I'm trying fix something that doesn't need fixing. Well maybe, LOL!
Enjoy that new barrel.
 
Ringostar said:
Has anyone here cut open a used barrel, and measure the throat angle after wearing from use? I would think that the angle would change over use, but would it start to follow the angle of the bullets that are being used?
Click to expand...

I haven't, no, but I've read reports about how over time pretty much any leade angle will end up at nearly 1.5° despite whatever it starts at. Nothing I can refer back to here other than my recollections of reading discussions on this topic in the 20-odd years I've been shooting. Yes the lead does move forward, away from the chamber, as a result of throat erosion, while the leade angle "seeks its own comfort level" so to speak.
 
Actually throats do not “move” they become bigger so it seems theyre moving forward because its a taper. Every shot expands the barrel because of pressure and it doesnt go back to zero. So every shot it gets bigger and bigger until it seems like its moving. Looking at the shape of a chamber gage like for military rifles youll see how it works
 
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