Does Throating Reamer Affect Accuracy?

[Dusty Stevens]

Thanks
I like the idea of just getting the reamer with the throat you want

thats exactly right.

 

[WayneShaw]

I use a throater fairly often. I have two unithroaters, that I bought for repeat applications. But I have several other that are normal throaters. Yes they cut fast, but it's not hard to keep from messing up. I think Dave mentioned sing a Sinclair case holder to clamp on the throater, I do the same, and hold it with my fingers. I throater after clambering in the same setup. You can turn the chuck in neutral to get the feel where it will start to cut, then advance it using the same methods you use to advance a reamer. Make sure the case is sized so it has no drag fitting the chamber and the bullet has good neck tension. Check often.

I use the throater for 6BR alone with 3 different bullet lengths. Why 3 reamers?

 

[Roeder]

I use the throater for 6BR alone with 3 different bullet lengths. Why 3 reamers?

If a guy that fits barrels for a living had to buy as many reamers as his customers want different throat lengths it would get expensive fast. Using a throater is a SKILL. It is tricky and easy to screw up, but once you master it, not really difficult.

 

[Dusty Stevens]

If a guy that fits barrels for a living had to buy as many reamers as his customers want different throat lengths it would get expensive fast. Using a throater is a SKILL. It is tricky and easy to screw up, but once you master it, not really difficult.

These days everybody wants their own reamers anyway for whatever reason

 

[shortgrass]

These days everybody wants their own reamers anyway for whatever reason

And some think the gunsmith should provide the tool for whatever it is they might want,,,,, at no extra charge, of course. Many who buy their own tool, who will not use it themselves, never bother to consult with the gunsmith who will actually do the work to get their opinion as to whether it's a good idea, or not. Or, what kind of "hiccups" one may encounter with these 'custom alterations'. "Everyone's got an idea". Every gunsmith who's been around for a good while has their own preference for throating just as they have a preference for cutting the body of the chamber. 'What works for them'.

 

[alinwa]

Another view, from one who's screwed up a 6mm throat (fixed it, but ended up with a .165 freebore LOL) luckily I had a bunch of old schoole long 108's with about a 7 ogive and managed to shoot it out over time. Poked a lot of holes in a lot of sagerats and watched 'em crawl back down their holes. Ya' don't get credits for bloodtrails on Richardson's Groundsquirrels and those 108's were like surgical needles.

ENNYways, Dave Tooley sez you'll hear 'kerchunk' 'kerchunk'....... and from my position even stepping into the ROOM with Tooley is like arguing with God..... but for me, in my case, I did my first one by hand using Kiff's uni-throater and my fingers and I didn't feel NUTTIN to speak of and no noises and I gotta' tell ya Kiff's uni-throater cuts like BUTTER, soft butter, soft, melted, settin' out on the counter butter.... I was too deep before I knew it.

Now that I've a lathe, and a DRO on my tailstock, I've done them under power and I just want to warn you it IS NOT a loud kerchunk kerchunk! I asked around and got the impression on my first one that I'd FEEL or HEAR something significant...... it's subtile, subtile I tell ya'....

I'm not arguing with Dave Tooley, he told you truth. I'm just reiterating what others have said, go slow, throats cut wikkid easy.

 

[Mozella]

........... snip............. I did my first one by hand using Kiff's uni-throater and my fingers and I didn't feel NUTTIN to speak of and no noises and I gotta' tell ya Kiff's uni-throater cuts like BUTTER, soft butter, soft, melted, settin' out on the counter butter.... I was too deep before I knew it........... snip.............

This is my experience too, all except for the "too deep" part. The OP should realize that a new Uni-throater can be a dangerous weapon in the hands of a DIY enthusiast. It's sharp and you are cutting mostly lands, so it's not like drilling SS with a worn out drill bit.

I've done several barrels with a Uni-throater, all successful. But my technique was to use the proper cutting oil and take PLENTY of time. My advice, unless you're a real gun smith, is to sneak up on the freebore you really want. I set my first cut to roughly half of what I though I wanted and got a little more than three quarters of my target. WATCH OUT, I said to myself and that is the advice I'd give to anyone doing his first DIY throating procedure.

In other words, set your first cut well short of your target and don't be surprised to find that the actual cut only takes light pressure and just a very few turns of the tool. It may feel like you're hardly doing anything at all. STOP there, clean up everything very carefully, and measure using your best technique. Then proceed from there. Take your time. If you get in a rush and go too far, fixing that screw-up will take a LOT more time.

 

[DaveTooley]

Another view, from one who's screwed up a 6mm throat (fixed it, but ended up with a .165 freebore LOL) luckily I had a bunch of old schoole long 108's with about a 7 ogive and managed to shoot it out over time. Poked a lot of holes in a lot of sagerats and watched 'em crawl back down their holes. Ya' don't get credits for bloodtrails on Richardson's Groundsquirrels and those 108's were like surgical needles.

ENNYways, Dave Tooley sez you'll hear 'kerchunk' 'kerchunk'....... and from my position even stepping into the ROOM with Tooley is like arguing with God..... but for me, in my case, I did my first one by hand using Kiff's uni-throater and my fingers and I didn't feel NUTTIN to speak of and no noises and I gotta' tell ya Kiff's uni-throater cuts like BUTTER, soft butter, soft, melted, settin' out on the counter butter.... I was too deep before I knew it.

Now that I've a lathe, and a DRO on my tailstock, I've done them under power and I just want to warn you it IS NOT a loud kerchunk kerchunk! I asked around and got the impression on my first one that I'd FEEL or HEAR something significant...... it's subtile, subtile I tell ya'....

I'm not arguing with Dave Tooley, he told you truth. I'm just reiterating what others have said, go slow, throats cut wikkid easy.

Al
I never said you would hear it. I said you would feel it when the reamer contacted the lands. Everyone knows we can't hear nuttin.

 

[alinwa]

Al
I never said you would hear it. I said you would feel it when the reamer contacted the lands. Everyone knows we can't hear nuttin.

What?

 

[Shawnba67]

You can also test out your throating procedure halfway through the chambering job. If its wrong wont matter for long. If its perfect just gotta do it again in an inch.
It is super easy to take to much.
I mounted a thing like a digital caliper with no jaws on my tailstock it is awesome for things like this and was like $20 on ebay. Think they call it a 6" dro its been handy.

 

[Tod Hendricks]

This made it much easier when doing it by hand.

 

[alinwa]

This made it much easier when doing it by hand.

View attachment 1045412

Tod Hendricks, that is a beautiful thing.

I like the way you think.

Whish't I'da thought'a that.

BTW I DO make my bore guides that way, using a well fire-formed case with an O-ring on the neck affixed to an AL tube, maybe something you can use

Cuz I WILL use your idea!

 

[Will Henry]

When I started cutting my own chambers, about forty years ago, I cut all of my throats separately, with a long throater. Most of my tooling was from Hugh Henriksen. I enjoyed pretty good success and won my share of plaques and tin; even some money. I still have no problem doing it this way although most of my reamers have integral throats. I'll give a brief description of the technique I use if anyone cares to read it.
If I'm chambering a new barrel and cutting the throat separately, I will have finished the chamber except for the throat. I'll use a dummy cartridge to establish the depth of cut. Let's assume I have cut the chamber so that the headspace gauge protrudes .135". I insert the dummy and take a measurement to the breech end of the barrel with a depth mike. We'll imagine that this measurement is .255" This means I will have to cut the throat to a depth of .120" for the bullet to just touch. In some cases, I had established depths to which I would cut the throat. For instance, I cut 6PPC's to .130". 6x47's were cut to .165" and short range 6BR's were cut the same as a PPC. Later on, I cut long range BR's to .190". My 6.5's are cut to about .255"
I support the reamer on the tailstock center and drive it with my homemade reamer wrench. I have to hold the reamer firmly against the center. I first establish about where the reamer will start to cut and note how far in the reamer has to go to make contact. Then I start the lathe, oil the reamer and throat and push the reamer in with the tailstock; stopping about 1/8 inch short and locking the tailstock in place. I then slowly feed the reamer in with the handwheel. I hold the wrench with my hand, very lightly. I feed slowly and will feel a "tick tick tick" when the reamer starts to cut. I note the mark on the handwheel and call that my zero. I allow the wrench to turn until it contacts the toolpost then, still holding it back against the center, I feed the reamer in the required amount (.120 in this case). The last five thou or so are fed in very slowly. When I reach the desired depth, I stop feeding and withdraw the reamer. The job is done. I generally run thelathe at about 300 rpm.
If I am lengthening an existing throat, the technique is essentially the same but there my be some differences. I have to be concerned with the diameter of the throat because I don't want a throat with a step in it so my throater must be at least as large as the existing throat (there are exceptions which I'll discuss later). If the throater is a couple tenths larger thasn the throat, it will, of course, start to cut before reaching the lands. However, I can tell the difference and can feel when the reamer starts to cut on the lands. I will still have established the amount I want to cut by using a dummy cartridge.
To establish as concentric a set-up as possible, I will just start the pilot into the rifling and will indicate the shank of the reamer with a .0001" gauge while, agin, maintaining contact with the tailstock centre.
I had mentioned exceptions regarding the necessity of making sure the reamer cleaned up the existing throat with no step and here they are:
1. If the original throat is a short cone, with no parallel section, it doesn't really matter.
2. If the customer doesn't care! I've not seen any noticeable detrimental effect from a throat with a visible but minute step in the throat; as long as everything is concentric. WH

 

[Shawnba67]

I made myself this for throating my own. the part the reamer goes through is bored on lathe to a tight slip fit. the outside is tapered just a little that centers it in the rear of chamber.
The collar on the end is both depth stop and turning/ holding handle. I enjoyed making it and my chamber turned out just fine. Good luck.