How to spec a custom chamber reamer?

[thefitter]

I'm building a custom .338 LM on a BAT action this spring and I'm getting ready to send off some loaded rounds to PT&G. The necks will be turned and I will be using AI magazines. My gun smith is recommending I go .002 neck clearance.

What other things do you specify to the reamer manufacturer?

Throat length?
Freebore?

Thanks

 

[jonbearman]

Tell ptg(dave) exactly what type of bullet and weight and he will tell you what you need.

 

[thefitter]

Tell ptg(dave) exactly what type of bullet and weight and he will tell you what you need.

Thank you for the reply, but I would like to have more input into the decision.

I just need help understanding what my options are.

 

[Hombre0321]

Please take this message in the positive way I mean it.

Dave at PTG is a professional he grinds reamers all of the time, he has the experiance you are paying for. This is his business and he is very good at it.

You on the other hand have turned to a public Talk Forum seeking advice and wanting to learn the "Questions" you need to ask. In coming here and asking questions to this forum you are seeking advice from people who may or may not have a clue as to how design a reamer. What is wrong with this scenario?

If you want input in the design of your reamer, that is probably not a bad thing. To do that not already knowing what you need to know is foolish.

Just food for thought. It is your money and you get to spend it the way "YOU" want. The end product will be much better if the professional you hire to do this job guides you, not you guiding him.......

Roland

 

[fdshuster]

I leave the freebore decision up to Dave Kiff. I just provide him with the primary bullet I intend to use, usually seated to touch the lands, with the base of the bullet as close to the neck/shoulder junction as possible, without contacting the donut that may form.

I also specify the chamber neck diameter that I want. That's my decision. And finally, the chamber over-all-length, usually .010" longer than maximum published case length. 1.570" for the 6BR, 1.510" for the 6ppc, etc. if it's for a wildcat or something I will be fire-forming, like the 6BRX.

The point is, I do not want a chamber length that is so long, that I will be left with a long gap in front of the case mouth, where a ring of carbon will form.

Just my way of doing it & has always worked for me.

 

[thefitter]

Please take this message in the positive way I mean it.

Dave at PTG is a professional he grinds reamers all of the time, he has the experiance you are paying for. This is his business and he is very good at it.

You on the other hand have turned to a public Talk Forum seeking advice and wanting to learn the "Questions" you need to ask. In coming here and asking questions to this forum you are seeking advice from people who may or may not have a clue as to how design a reamer. What is wrong with this scenario?

If you want input in the design of your reamer, that is probably not a bad thing. To do that not already knowing what you need to know is foolish.

Just food for thought. It is your money and you get to spend it the way "YOU" want. The end product will be much better if the professional you hire to do this job guides you, not you guiding him.......

Roland

I understand your point. But no where in my post did I ask about "wanting to learn the "Questions" you need to ask".

I want to learn how to decide what to TELL them I want for myself.

..."If you want input in the design of your reamer, that is probably not a bad thing. To do that not already knowing what you need to know is foolish."...

That's the point of my post. It's foolish to try and learn? I should already know it somehow?

I want to learn about all the variables in specifying a chamber reamer. And I want to decide myself on each variable. I do not want to just let someone tell me what I need. If I wanted that I would buy a rifle off the shelf.

I am also acquainted with Dave and respect his expertise. But I want to be able to send him my loaded rounds, rifle configuration and my own preliminary specs. Then if he has some input we can discuss it.

Thanks

 

[thefitter]

I leave the freebore decision up to Dave Kiff. I just provide him with the primary bullet I intend to use, usually seated to touch the lands, with the base of the bullet as close to the neck/shoulder junction as possible, without contacting the donut that may form.

I also specify the chamber neck diameter that I want. That's my decision. And finally, the chamber over-all-length, usually .010" longer than maximum published case length. 1.570" for the 6BR, 1.510" for the 6ppc, etc. if it's for a wildcat or something I will be fire-forming, like the 6BRX.

The point is, I do not want a chamber length that is so long, that I will be left with a long gap in front of the case mouth, where a ring of carbon will form.

Just my way of doing it & has always worked for me.

Chamber over-all-length is helpful. Thank you!

 

[Scott Harris]

.002 clearance between your neck and chamber for a magnum cartridge? I think that advice is questionable and possibly dangerous. Do some searches, but many respected folks here and elsewhere have recommended a minimum of .004 clearance for 30 cal and larger cartridges with .006 being safe and not hurting accuracy. I aim for .005 clearance with my 308WIN and would consider that a minimum for your cartridge.

Along the same lines, the .010 clearance between the case length and chamber is debatable. .040-.050 is a normal dimension and much safer. Regarding the carbon ring comment, I've recently heard the contra-argument that you might want a lot of room between the cartridge length and chamber length. That way, regular cleaning techniques will ensure the carbon ring never gets anywhere close to impinging on the case. In that case, who cares if there is a carbon ring so long as your regular cleaning keeps it well clear of the cartridge case? If you agree with that reasoning, then lots of clearance is desired....

I have always relied on Dave Kiff's advice, but always preface any discussions with him that safety and reliable function always take precedence. Each to his own, but with a 338LM, I'd think you should consider safety and reliable function paramount also.

 

[thefitter]

.002 clearance between your neck and chamber for a magnum cartridge? I think that advice is questionable and possibly dangerous. Do some searches, but many respected folks here and elsewhere have recommended a minimum of .004 clearance for 30 cal and larger cartridges with .006 being safe and not hurting accuracy. I aim for .005 clearance with my 308WIN and would consider that a minimum for your cartridge.

Along the same lines, the .010 clearance between the case length and chamber is debatable. .040-.050 is a normal dimension and much safer. Regarding the carbon ring comment, I've recently heard the contra-argument that you might want a lot of room between the cartridge length and chamber length. That way, regular cleaning techniques will ensure the carbon ring never gets anywhere close to impinging on the case. In that case, who cares if there is a carbon ring so long as your regular cleaning keeps it well clear of the cartridge case? If you agree with that reasoning, then lots of clearance is desired....

I have always relied on Dave Kiff's advice, but always preface any discussions with him that safety and reliable function always take precedence. Each to his own, but with a 338LM, I'd think you should consider safety and reliable function paramount also.

Thank you very much this is exactly the kind of info I need. I will revisit the .002 neck clearance issue with my gunsmith.

 

[alf]

Clearance is clearance.

As long as there's enough to release the bullet is all that's necessary....

You should buy some brass, neck turn it to your requirements, seat a bullet, measure the diameter, add the clearance you want, and order away. A target type gun, I'd feel comfortable with .002" over.

Freebore needed is dependent on the OAL of your loaded round to fit the AI mag of your bullet(s) of choice. Same thing.... seat you bullet(s) where you need them, allow some for the throat moving, and send it (them) in to the maker.

I could never understand, the most dreaded chore in reloading is trimming brass, but most people order reamers to SAMMI case length. Why? Why not order .020, .030, or .040" over? Most new brass after one firing is already at max length. I can understand the carbon ring.....kinda..... but I don't see it as a problem.....most times.

 

[thefitter]

Clearance is clearance.

As long as there's enough to release the bullet is all that's necessary....

You should buy some brass, neck turn it to your requirements, seat a bullet, measure the diameter, add the clearance you want, and order away. A target type gun, I'd feel comfortable with .002" over.

Freebore needed is dependent on the OAL of your loaded round to fit the AI mag of your bullet(s) of choice. Same thing.... seat you bullet(s) where you need them, allow some for the throat moving, and send it (them) in to the maker.

I could never understand, the most dreaded chore in reloading is trimming brass, but most people order reamers to SAMMI case length. Why? Why not order .020, .030, or .040" over? Most new brass after one firing is already at max length. I can understand the carbon ring.....kinda..... but I don't see it as a problem.....most times.

Yeah, the only reason I trim brass at all is consistency. I wish each case grew the same after firing, sure would make things easier.

Thanks for your input.

 

[Frankr]

I am for the big neck clearance on the big cartridge,.005-.006..some say better long range accuracry with more clearance..im also for .030-.040 case length over the OAL with the big cartridge.

The carbon ring really comes into play uasually in short throat ..some freebore's are .0005 over bore dia so if you build .001-.002 of carbon in there you kind of size the bullet.. that may be a area to really talk to dave about as to the dia of the free bore and the lead in to the bore angles..

 

[Keith Glasscock]

I'd suggest this:

Send Dave some DUMMY (not live) rounds to measure. Be certain to tell him if the seating depth you are using is intended to be just touching, jammed, or jumped and let Dave work his magic.

For neck clearance, I'd tell Dave what I intend to do with the rifle. He knows what works and what doesn't. For example, a really tight neck works great for a bench rifle, or a rifle where dirt isn't a problem. If you are going to shoot a lot of rounds, run it in dirty conditions, etc. You might need a little more clearance.

All in all, you are best off sending the dummies in with a note that says:

"Dave,

Make me a reamer for my 338LM that will fit this round just touching the lands. The rifle will be used for XXX (note if it is magazine fed). I will be turning necks like the dummy round and prefer a tight neck. I value accuracy [very highly, above functionallity, balanced with functionality, whathaveyou]. Please call me to discuss. "

Be very aware that Dave is extremely busy and does not have time for anything other than getting the particulars down on a reamer. By that same token, he does a wonderful job.

Then wait for several weeks and a reamer will appear on your doorstep. It is the coolest thing ever to have a rifle chambered with your own personal reamer custom designed for what you want and need.

 

[coonhunter70]

I just ordered my first reamer yesterday from Dave, I just told him what I wanted to do and he new immediately what I needed from his experience with this cartridge (25-284) everything he said made sense to me about what I was wanting to do so within a couple minutes on the phone I had a reamer on order. Piece-o-cake!

 

[fdshuster]

scotharr: With my match chambers, ( 6ppc,4 6BR's, 6 30BR, 6BRX, and a few others), I'm running between .005" (minimum) to a maximum of .010 clearance between the front of the case mouths & the front of the chamber.

As regularly seen with my Hawkeye, there is a burn ring around the circumference of that "gap", but never a trace of any buildup. There is just no empty space to fill up with carbon, so, none to remove.

On the other hand I have a 222 Remington factory chambering with a huge amount of empty space between the case mouth & the front of the chamber, that does fillup with carbon, again, as seen with my borescope. It measures .041" longer than my normal trim length of 1.700".

I did have signs of high pressure, took it to one of our local well-known, premier rifle builders, he 'scoped it out ( before I bought my Hawkeye & one of the reasons I bought my own) & showed me the heavy buildup of carbon. And, yes I have always cleaned using a snug fitting bronze brush, & even JB as needed.

Keeping the close tolerences has resulted in never having an issue with carbon in that area.

I'm not advocating that anyone use .005" to .010" as a clearance standard, it does require constant monitoring, and many will not spend the time required, but by the same token, based on my experience with .041", that is way too much.

Following the advice in most loading manuals to trim ".010" shorter than max case length", plus the .010" built into the reamer = .020" of clearance, more than enough to be "safe".

But, to each his own, do whatever you like.

 

[wwbrown]

I am in the camp of telling Dave what you are shooting (caliber and bullet) and how you are using it, hunting, tactical, BR, etc and listening carefully to what he says. I made the mistake of not listening to him once and now have a very nice slight turn 6.5 x 55 AI reamer when I wanted a no-turn, the neck diameter was what I thought would work not what Dave KNEW would work.

A while back I needed a 338 LM reamer to shoot 300 g Scenars out of a mag cut and Dave specced the 338 Tactical Match reamer that had been tested extensively in some testing at Crane Lake. The 338's cut with that reamer and tremendous performers. Not only do we civilian shooters rely on Dave so do quite a few military weapons testers, so Dave learns from everyone what works and does not and shares that wealth of knowledge with everyone just by asking for it.



wade

 

[BoydAllen]

This is what I would do. First I would see if I could locate some high mileage brass that was at the end of its useful life, having been sized and fired numerous times so as to be work hardened to the probable maximum. This brass will have appreciably more spring back than new brass, and will be the basis of a worst case sizing situation. Next I would purchase a bushing FL die, and size the cases so that they have a .002 bump from their fired shoulder to head length. (At this point, it is not important that the case "headspace" be in reference to any standard or the rifle to be built.) Next I would carefully measure the sized cases, and using the largest one, spec the body dimensions of the reamer for .002 clearance .200 from the head, and half that much at the shoulder (diameter). For the neck diameter, I would do a clean up turn on some new brass and spec the neck diameter to give .003 clearance on a loaded round, and in reality I would probably turn necks a little thinner so as to have a clearance of .005. Lots of knowledgeable shooters have figured out that more clearance works better, starting with around .003, or a little less at 6mm, and increasing as the caliber gets larger.....something about a cleaner bullet release. With the body diameters and neck diameter settled, I would make up some loaded rounds with my preferred bullets. loaded to the length that I wanted so that Dave could put them on the optical comparitor to come up with an appropriate throat length so that I can load all the way to a soft seat if I wanted, without any interference problems, and with enough bullet in the case necks. The other thing that I would pay some attention to would be freebore diameter, which I would spec. at .0003 over the measured maximum diameter of the largest diameter bullet that I planned on shooting. Obviously, before I could make up the previously mentioned dummy rounds, I would need some sort of seater. I would probably buy a Wilson seater. I already have an arbor press, and prefer that kind of seater. My second choice would be a Forster.

 

[thefitter]

This is what I would do. First I would see if I could locate some high mileage brass that was at the end of its useful life, having been sized and fired numerous times so as to be work hardened to the probable maximum. This brass will have appreciably more spring back than new brass, and will be the basis of a worst case sizing situation. Next I would purchase a bushing FL die, and size the cases so that they have a .002 bump from their fired shoulder to head length. (At this point, it is not important that the case "headspace" be in reference to any standard or the rifle to be built.) Next I would carefully measure the sized cases, and using the largest one, spec the body dimensions of the reamer for .002 clearance .200 from the head, and half that much at the shoulder (diameter). For the neck diameter, I would do a clean up turn on some new brass and spec the neck diameter to give .003 clearance on a loaded round, and in reality I would probably turn necks a little thinner so as to have a clearance of .005. Lots of knowledgeable shooters have figured out that more clearance works better, starting with around .003, or a little less at 6mm, and increasing as the caliber gets larger.....something about a cleaner bullet release. With the body diameters and neck diameter settled, I would make up some loaded rounds with my preferred bullets. loaded to the length that I wanted so that Dave could put them on the optical comparitor to come up with an appropriate throat length so that I can load all the way to a soft seat if I wanted, without any interference problems, and with enough bullet in the case necks. The other thing that I would pay some attention to would be freebore diameter, which I would spec. at .0003 over the measured maximum diameter of the largest diameter bullet that I planned on shooting. Obviously, before I could make up the previously mentioned dummy rounds, I would need some sort of seater. I would probably buy a Wilson seater. I already have an arbor press, and prefer that kind of seater. My second choice would be a Forster.

That is a lot to digest, thank you.