Throat reaming a chamber?

T

thisguy65

Guest
Have to be extremely careful because the throating reamer will cut the rifling like a hot knife through butter.

This all steamed from a video I watch about throat reaming for a certain bullet type. Smith used a SAAMI spec reamer inserted the cartridge. The case head was not flush with the breech of the barrel but stuck out a few thousands. His goal was to ream the throat enough to allow the dummy round to be .020 from the lands.

So if he has .125 of the case sticking out of the breech. He would ream it .125+ 0.20, correct? **I'm using fictional number here**


lastly is there away to determine throat length from the reamer's drawing? I'm getting something wrong because I'm using a rifle here at the house that was chamber using a SAAMI spec reamer, I a copy of that reamer drawing as well. I'm doing something wrong or misinterpreting it.
 
Not if the throater is a diff design than the reamer throat.
Best to just touch and check.
 
There is a thread on accurate shooter going now about it. You may be money ahead getting the gunsmith who chambered your barrel to throat it for you. In about 39 seconds you can render that chamber unusable
 
Dusty Stevens said:
There is a thread on accurate shooter going now about it. You may be money ahead getting the gunsmith who chambered your barrel to throat it for you. In about 39 seconds you can render that chamber unusable
Click to expand...

I'm not trying to throat ream just after watching the video I'm more curious how it's done correctly.

Just as long as I say under 39 second I'm good. ;)
 
Order a throat img reamer of the correct diameter that has a removable pilot bushing. Modify a cartridge case by renaming the primer end to where it will support the back of the throater shank. Insert the modified cartridge, insert the throater and PROCEED VERY CAREFULLY. This is best done with the barrel removed.

.
 
The new throaters come with a cartridge case adapter and a t handle. Go slow and check often it cuts with no effort so you cant feel it
 
Checking every turn seems to be good point.

I'm really looking at how the calculations come up and if my thinking is correct. The video I watch he didn't mention the reamer he was using so I guess it was a reamer that has very little fb or none at all.


He placed the dummy round in the camber and a good bit stuck out from the end of the barrel. Lets call it .125. So he would have to cut the throat .125 for the rear of the cartridge to fully seat in the chamber. Then ream addition .020 if he wanted the bullet to jump .020 to the lands. SO in total he would have to jump ream it .145 correct?
 
again, not if the original chamber reamer and the throater are
cut at diff angles.
best to measure as you go with the throater.
 
Yea you cant really calculate it like chuck said the reamers are gonna be different. And you never know if the ctg sticks out any because of headspace or whatever unless you measure the headspace with a gage then compare
 
thisguy65 said:
Checking every turn seems to be good point.

I'm really looking at how the calculations come up and if my thinking is correct. The video I watch he didn't mention the reamer he was using so I guess it was a reamer that has very little fb or none at all.


He placed the dummy round in the camber and a good bit stuck out from the end of the barrel. Lets call it .125. So he would have to cut the throat .125 for the rear of the cartridge to fully seat in the chamber. Then ream addition .020 if he wanted the bullet to jump .020 to the lands. SO in total he would have to jump ream it .145 correct?
Click to expand...

That is, for the most part, correct. If the chamber was cut with no throat at all, the amount to be cut can be measured quite precisely. If the chambering reamer has an integral throater but this is found to be too short, it is a little more difficult to measure and cut as precisely. This is because, with no throat, the point of contact on the bullet ogive is equivalent to the bore diameter. If the throat is cut but short, the point of contact may be further down on the ogive depending upon the angle of the throat.
When I am cutting a throat separately, I do it this way:
The reamer is held in a tap wrench and supported on the tailstock center. I hold the reamer with my thumb and forfinger so I can feel immediately when it touches the lands. The lathes run fairly slowly (90 rpm) because I've found, if I run it faster, it is more difficult to feel the start of the cut. Once contact is made, I hold the reamer back against the center firmly and advance it quite slowly. The last five thou are cut in about 20 revolutions so as to minimize the feather edge left by the reamer.
If I am lengthening a throat, I will first ream it just ten or fifteen thou then re-check with the dummy (and no, this does not refer to a shop assistant) and use this measurement as the starting point. This is so that I am measuring with the angle I am cutting so I can judge the length more precisely. Regards, Bill
 
I guess thats for the guys that already have one. I got one about a month ago and it came with a handle, reamer holder adapter and ctg specific sleeve. Think thats what they call the deluxe pkg. the t handle is quite nice its long enough to use thru the action if so inclined
 
This has been my experience with the Kiff Uni Throater the last couple throats I have had to lengthen. I needed to move the throat, or desired bullet length forward .060 What worked put for me was that I only had to move the Uni Throater forward .030 to obtain the target length. This has been the case the last two times I have fooled with a Uni Throater. I always go slow when I'm not sure of a situation, and in this case I'm glad I did. had just assumed I needed to move the locking rings on the Uni Throater forward .060 I would had had a mess on my hands. My experience!! Lee
 
skeetlee said:
This has been my experience with the Kiff Uni Throater the last couple throats I have had to lengthen. I needed to move the throat, or desired bullet length forward .060 What worked put for me was that I only had to move the Uni Throater forward .030 to obtain the target length. This has been the case the last two times I have fooled with a Uni Throater. I always go slow when I'm not sure of a situation, and in this case I'm glad I did. had just assumed I needed to move the locking rings on the Uni Throater forward .060 I would had had a mess on my hands. My experience!! Lee
Click to expand...

Yeah, I ordered a .223 barrel originally intending to short lighter bullets, but I later changed my mind and wanted a longer throat for heavier bullets. I'm no gunsmith, but I play one in my garage.

I bought a PTG uni-throater, and since I didn't know what I was doing, I took it slowly. The actual cutting required was less than I calculated, which is the same experience you had. It was a cut-measure-cut-measure procedure and, like you, I'm glad I took my time.

Ignorance is bliss, until you screw up. But if you recognize your own lack of experience and use some common sense, it's quite possible to perform precision DIY projects with success.
 
A year or so back, I ordered a 257 throater from PTG and got a uni-throater in the mail. I took one look and thought, "what the heck is this?" I sent it back and wrote that I wanted a simple 25 caliber throating reamer. I ended up with a throater for the 25 ACP! Now I was just pissed off so I just stoned down a spare 6.5 throater I had and did the job. Took me two hours to stone down the 6.5 so it cost more than just buying another one but at least it got done. Now, I guess I'll stone down the stupid ACP reamer to .2435 and make another 6mm out of it. It's a 3/4 degree reamer and I'd kind of like to try it anyway but it seems like the hard way to go about it. Regards, Bill
 
I think I would have to tape a five dollar bill to it to get someone to steal it. I guess I wasn't clear enough when I ordered it. Regards, Bill
 
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