30 cal throating reamer?

  • 4.4K Views
  • Last Post 21 December 2012
Chargar posted this 14 December 2012

I have a couple of 30 caliber rifles with very short throats, a Marlin 336 (30-30) and a Remington 141 (30 Rem). A throating job is in order to get them up to speed and flexible with cast bullets. I would also like to use this is just about any other 30 caliber rifle for cast bullets.

So here are my questions;

  1. What are the best dimensions needed for such a reamer?

  2. Where to buy or have made such a reamer?

  3. What about pilots?

Thank you for any counsel you might give.

  1. Where to buy handles and extensions?

Attached Files

Order By: Standard | Newest | Votes
pat i. posted this 14 December 2012

I'd look at a Pacific Tool and Grinding Uni-Throater with both 308 and 30-30 sleeves dimensioned .311 x 1 1/2 degree. You can buy a set of .30 caliber pilots in .0002 steps but could probably get by with just a .300. A call to Dave Kiff with your questions would be the best bet but I think what I suggested would fit the bill.

Attached Files

lmcollins posted this 15 December 2012

All of the reamer makers make throating reamers: Pacific Tool and Gauge, JGS, Dave Mansion, Clymer, and there might be others that I cannot think of of of the top of my head. If you want a specific throat diameter or angle over standard you might have to order it, and pay more.

The big problem you must realize is that in most cases you have to put stops on the reamer handle that you must buy or make, and inter the barrel from the rear. In many cases this means that the barrel must be dismounted from the rifle, and at least put into a vise, if not a lathe run at low spead with cutting fluid. If you are not  equiped with the tools or skills to do this don't try. The Marlin 336 you could probably do with the rifle partially disassembled. Bolt actions of the standard types can always be done without a big problem. It all depennds on what you have to drive your reamer with. Its length, etc. Remember, you are only trying to remove thousands off of the lands above the grooves for a very short distance. A 1/16 of an inch is only .063 thousands, and would be a major increase in throat length that would be excessive in most cases.

You might buy a reamer to get what you want for specifications, and get someone qualified to do the work.From my playing with centerfire rifles I'd say a nominal .300 pilot with a 3 degree or less included angle, and a cutting diamater of not more than .309 for the diamater to recieve the bullet. If the barrel is of good quality this should work. If it is a junker, clunker you are probably spitting into the wind playing with throating rather than seating deapth or a differnt bullet.

A wartime expedient barrel for jacketed bullets and limited accuracy, is probably a bad investment to play with to this extent with special tooling made to meticulous modern standards. The barrel maybe up, down, and all-around its entire lenght.

The above is just my opinion, from my life experience, and I don't pretend to be an expert. I just have some experience, and some common sense.

 

Attached Files

pat i. posted this 15 December 2012

The Uni-Throater has a graduated stop incorporated into the reamer and .309 wouldn't clean up the existing ball seat on most chambers that have them including the .308 which has a .310 ball seat according to my book of chamber prints. My suggestion is for barrels being set up for cast bullets which is what the OP said he was looking for.

Attached Files

TomG posted this 17 December 2012

What dimensions you want on your reamer depends on what you will do with it.  If you are throating an existing factory chamber you need one with a .310 to .312” freebore diameter.  If you are going for the best accuracy with a new barrel, the best dimensions I've found are a freebore diameter of a half thousandth over bore diameter going into a 1 degree ( included angle) lead angle. There is a difference in an included angle and per side angle when describing the angle you desire. 

If changing the lead angle of an existing factory chamber ( usually 3 degrees or greater) I would use a 1 degree included reamer.  We have experimented with 3/4 degree included and it worked just as well. 

I like to use a throat freebore diameter just a little larger than the bore diameter.  My belief is that I would rather size the bullet down in a sizing press than shoot an oversize bullet into a barrel and do the sizing down under the violent conditions generated during the firing process. I always shot bullets that were sized to be only a light interferance fit in the freebore.  They were also tapered in a die to the angle of the lead in a bump press so that they were a perfect fit to the throat of the gun.  I always found that they shot better if they were seated long in the case and were pushed back slightly into the case as the bolt was closed. 

If you cut the throat too deep, you run the risk of your COAL being too long to fit in a magazine or feed off the lifter of a lever gun.  So do your homework first before getting too wild with a throater reamer.

Lead bullets are relatively soft compared to jacketed bullets.  They seem to shoot much better if they have a nice shallow lead angle in the throat and are seated solidly into the throat when chambered. The more support you can give the bullet in the throat, the better it will shoot.

If you are throating a Marlin lever gun, you may find that the COAL will be too long to work through the action and still have the bullet touch the lands when chambered.  If the bullets are really blunt, it may be that the factory throat angle will work quite well. I've shot one of the LBT Wide Flat nose bullets in my Marlin 45-70 lever shoulder buster with amazing accuracy in the standard throat. This bullet was designed very well and when crimped into the crimp groove, would touch the lands and feed through the action. Again, it's very blunt and was a good match to the factory throat angle. 

Dave Kiff of Pacific Precision grinding will make you any reamer you want at no extra cost over that of a standard reamer.

For best accuracy buy a selection of rotating pilots for your reamer and choose one the is a light slip fit in your bore  Don't forget that they heat up and get slightly tighter so I call for a light slip fit. 

I've made my own tee handles extensions to finish the last thou or two when chambering.  I'm sure Dave probably sells one if you can't make your own.  I actually do my throating at about 200 rpm in my lathe in the same set up after I finish the chamber.  Pushing it with the tail stock keeps it right on center with no wobble. Wobble translates into an oversize throat and must be avoided. I use the micrometer advance on the tailstock to take out a precise amount as I deepen the throat. It's a cut and try till you get the bullet to push back to the OAL cartridge length you want. Go really slow.  Cause you can't put it back in if you go too far.  

Tom G.

Attached Files

Chargar posted this 17 December 2012

I am not interested in chambering barrels. I have two rifles that are cast bullet problem children.

  1. A 1960 Marlin 336 Texan with almost no freebore/throat. Traditional cast bullets like 311291 won't chamber unless the bullet is seated with no shoulder out of the case.

  2. I have a 1935 Remington 141 in 30 Remington with the same problem.

Therefore, I want a throating reamer to give enough freebore/throat to seat 311291 or similiar bullets with the case mouth given a slight crimp in the crimp groove. Not a difficult thing to do, just need to know where to buy a reamer.

Thanks, now know where to go. I will have Pacific make me one .311 and pilots to fit the bore. I have hand reamed 30 caliber throats before, but used a borrowed reamer. That was 40 plus years ago. But the process is not a deep dark mystery to me.

thanks all..Charles

Attached Files

frnkeore posted this 17 December 2012

charger, in both your cases, you don't have a existing ball seat/freebore. don't make it .311, go no larger than .3095. what tom says is right on, although if a rifle has a .310 freebore, such as the 308 win,i would not enlarge it unless i knew for sure it wasn't concentric. if .3095, size you bullets in a .309 die and they'll have a 2 or 3 tens slip fit.

in your application, i would go at either 1 or 1.5 deg per side for your lead and .080 - .090 for the freebore. your extemely limited on your oal @ 2.56 on the 141 rem and probably the 336, too. i have a 141 and 14.

if it were a match rifle, i would go 3/4 to 1/2 like tom says, i had my 30 cal reamer made back in the '90's with a .309 x .110 freebore and a .7 deg lead based on ardito's work with his approx 1/2 deg lead.

load them out as far as the feed mech will allow.

frank

Attached Files

Chargar posted this 18 December 2012

frnkeore...Why would one want to limit himself to cast bullets of .309?

The aforementioned 1960 Marlin 336 has a Microgroove barrel with a groove diamter of .309 and a bore of .304, both specs on the large size. I would choose to shoot at least .310 bullets with .311 being a stronger preference.

You seem quite strong about a throat being no bigger than .3095 and I don't understand your reasoning.

Bear in mind here, I am not talking about building target rifles here, or high grade bolt actions of any kind. I am talking about older lever and pumpguns that currently are not cast bullet friendly, due to short throats. In both cases, there really is not any freebore, just a bevel on the end of the chamber.

I think you guys sometimes are more concerned about the ideal, that you lose sight of the issue on the table.

As an aside about ten years ago, I had Mountain Molds make me a custom mold for the Marlin. It has no full diamter outside of the case neck and a taper nose that will allow the bullet to be chambered with light engraving and still have good nose support. It shoots very well when sized .310 which is the as cast diamter. I would just like to load ammo for it that will shoot in my other 30-30s of which I have a 5 more.

Attached Files

tturner53 posted this 18 December 2012

Just for an alternative, Ranch Dog designed a bullet specifically for the Marlin 30-30. It's 165 gr. Has a good reputation in that gun. If you want to try some I can send you a sample.

Attached Files

Chargar posted this 18 December 2012

Thank you for the offer, but I own 50 plus caliber moulds. I want these rifles to shoot the bullets I want them to shoot. I want to enforce my will on them and not the other way around. It is man against metal and I want man to win.

Attached Files

Ken Campbell Iowa posted this 18 December 2012

tomG sez:

If you are going for the best accuracy with a new barrel, the best dimensions I've found are a freebore diameter of a half thousandth over bore diameter

ken sez: great stuff as usual ...when you mention bore diameter did you mean groove diameter ? actually, the idea of a bore dia. free bore is interesting ! i could envision a bore diameter freebore about 3/4 inch long, with properly nose-fitted bullet ... working pretty well ... that would be similar to the A.Neidner chamber system, of which i keep thinking is worth a try.

thanks for the good dope. ken

Attached Files

TomG posted this 19 December 2012

Hi Ken, 

Yep, I meant groove dia.  Had a brain fart. 

Back when I was shooting in the CBA BR matches heavy class, that's the throat I would use.  I'd have a 30 BR reamer with a tight neck made up and then get a separate throater at .309 freebore into a half deg. per side leade.  Then I'd make up a bump die off the throater reamer to taper the bullets noses to the same taper as the chamber throat.  I'd adjust the bump die to give me a dia. on the bullet rear bands that was a slight interferance fit in the chamber throat for perfect sealing. 

These bullets would seal up so well that one time I forgot to put powder in the case and when I fired it. The primer went off and generated enough gas pressure to seat the bullet in the throat and seal off the neck.  When I opened the bolt it released the gas pressure that was held in the case.  I was running a 0 to one thou. neck clearance so the neck didn't even work harden from so little sizing and would seal easily. I'd shoot bullets cast of monotype or foundry type at 2500 to 2700 fps. with no leading.

It was a lot of work to make the bullets etc. but it sure shot well. 

Tom

Attached Files

RKing22 posted this 21 December 2012

Be careful with COL on the 141. I have one from 1939 and it shoots the 311041 well (for a hunting rifle). Any way ,the 141 action is very picky about the cartridge length thru the feed cycle,some say exactly to the factory OAL. A too long round creates a VERY interesting tieup. I would load a dummy round the way you want and see if the rifle will feed it. My 311041 seated even slightly to the long side will not feed.( still in the crimp groove)

Attached Files

frnkeore posted this 21 December 2012

Chargar wrote: frnkeore...Why would one want to limit himself to cast bullets of .309?

The aforementioned 1960 Marlin 336 has a Microgroove barrel with a groove diamter of .309 and a bore of .304, both specs on the large size. I would choose to shoot at least .310 bullets with .311 being a stronger preference.

You seem quite strong about a throat being no bigger than .3095 and I don't understand your reasoning.

Bear in mind here, I am not talking about building target rifles here, or high grade bolt actions of any kind. I am talking about older lever and pumpguns that currently are not cast bullet friendly, due to short throats. In both cases, there really is not any freebore, just a bevel on the end of the chamber.

I think you guys sometimes are more concerned about the ideal, that you lose sight of the issue on the table.

As an aside about ten years ago, I had Mountain Molds make me a custom mold for the Marlin. It has no full diamter outside of the case neck and a taper nose that will allow the bullet to be chambered with light engraving and still have good nose support. It shoots very well when sized .310 which is the as cast diamter. I would just like to load ammo for it that will shoot in my other 30-30s of which I have a 5 more.

charger,

I don't size bullets anymore than I have to, i'm a target shooter and always go for the best of everything.

Are both your rifles .309 grooves? I believe that you'll find that the Rem is closer to .306. I have 3 of them and they are all .306. If you shoot .311 in it, you'll be sizing them .005 in the barrel. Like Tom, I make my freebores a little over groove dia but, in my case my reamer is .309, .001 over a .308 groove.

If you wanted to digest .311 bullets then by all means do your freebore at .311/.3115. It will shoot better than a none freebore chamber but, remember that your limited on OAL. Make up a dummy round at the max length that you can feed it, then measure the full diameter bullet and freebore that much in front of the case or sent it to PT&G and let them do it for you.

Always remember, the more you size your cast bullet, the more distorted it will be.

Frank

Attached Files

Close