Gunsmithing 300 Win Mag Chamber

S

smokshwn

Sergeant
Full Member
Minuteman
Dec 7, 2004
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Salt Lake UT
#1
I am sure this is a repeat but after searching until my vision is blurry, I gotta ask the question.

I have a Rem 700 in 300 Win Mag that is getting the action trued and barrel set back. In looking at the reloading forum I have decided I would like to run the 210 bergers or the 208 Amax's. However occasionally it would be nice to shoot factory length ammo as well without losing out on good accuracy.

Do I have the gun throated to accept these bullets loaded long (3.50ish) or do I go with a standard throat and load these bullets shorter (3.35ish)?

Thanks in advance, Craig
 
#2
Re: 300 Win Mag Chamber

That's a discussion that you really should have had with the person doing the work BEFORE he started working on it. Chambering reamers can be of all different sorts. There are dozens of changes available for each different caliber.
 
#4
Re: 300 Win Mag Chamber

Victor,

Sorry I may not have been clear. It is a discussion that I am having with my gunsmith and the chamber has not been cut yet. So I am sitting with bullets and brass and calipers in front of me trying to get a better sense of the compromises/pros/cons and was looking for some guidance.
 
#5
Re: 300 Win Mag Chamber

Give Randy a call at RDprecision. Aka HateCA. He just finished my 300 win mag build. Contact info is on his web site... rdprecision.net
 
#6
Re: 300 Win Mag Chamber

Do yourself a favor and call one of the big chamber reamer makers. I can't remember the guy's name at the place I have been using. But I'll bet if you call one of the bigger companies and tell one of the techs or engineers your delima, they can talk you through it. I've been using this place the last several I've ordered: http://www.pacifictoolandgauge.com/ They've been good to me.
 
#7
Re: 300 Win Mag Chamber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bozochu</div><div class="ubbcode-body">Give Randy a call at RDprecision. Aka HateCA. He just finished my 300 win mag build. Contact info is on his web site... rdprecision.net </div></div>

+1... Randy knows his business.
 
#8
Re: 300 Win Mag Chamber

thats an interesting question, could you come back here and let us know what you come up with. The guy at Pacific tool's name is Dave Kiff, he or Randy would know.
 
#9
Re: 300 Win Mag Chamber

You may also want to call Hornady and Berger and get their advice on how their bullets like to be loaded. For instance; I believe the Bergers like to be loaded long just touching the lands or, a short jump to them. I don't think Hornady has any recommendation about attaining better accuracy with a longer or shorter COL. I see your dilemma though. A longer COL can hold more powder and attain higher velocity. But a longer throat may sacrifice accuracy when using shorter factory rounds. If you have not reloaded before, once you start you may find you have no desire to use factory ammo. Then, your chamber length decision gets a whole lot easier.
 
#10
Re: 300 Win Mag Chamber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: smokshwn</div><div class="ubbcode-body">I am sure this is a repeat but after searching until my vision is blurry, I gotta ask the question.

I have a Rem 700 in 300 Win Mag that is getting the action trued and barrel set back. In looking at the reloading forum I have decided I would like to run the 210 bergers or the 208 Amax's. However occasionally it would be nice to shoot factory length ammo as well without losing out on good accuracy.

Do I have the gun throated to accept these bullets loaded long (3.50ish) or do I go with a standard throat and load these bullets shorter (3.35ish)?

Thanks in advance, Craig </div></div>

Here is something to think about. You mentioned you are having the barrel set back AND the action trued. If your gunsmith is doing both of these to your rifle, you need a new gunsmith. If he is doing a real job of trueing the action, it will need the action threads trued along with the face of the receiver, the bolt and bolt face including the receiver lugs and the bolt lugs. There are just too many guys out there who do not do the complete job.

When the receiver threads get recut, the original barrel threads will be too loose in the action. To do it right, you need a new barrel. Simply facing the receiver won't cut it.
 
#11
Re: 300 Win Mag Chamber

I thought the question was slated towards throat length, not gunsmiths...

Concerning throat length. Craig, I would go with a throat that matches the bullets you want to shoot and just see what you get with factory loads instead of trying to compromise.

Scott
 
#12
Re: 300 Win Mag Chamber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Big Bore</div><div class="ubbcode-body">I thought the question was slated towards throat length, not gunsmiths...</div></div>

Ease up- the OP just received an invaluable lesson.
 
#13
Re: 300 Win Mag Chamber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jim Kobe</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: smokshwn</div><div class="ubbcode-body">I am sure this is a repeat but after searching until my vision is blurry, I gotta ask the question.

I have a Rem 700 in 300 Win Mag that is getting the action trued and barrel set back. In looking at the reloading forum I have decided I would like to run the 210 bergers or the 208 Amax's. However occasionally it would be nice to shoot factory length ammo as well without losing out on good accuracy.

Do I have the gun throated to accept these bullets loaded long (3.50ish) or do I go with a standard throat and load these bullets shorter (3.35ish)?

Thanks in advance, Craig </div></div>

Here is something to think about. You mentioned you are having the barrel set back AND the action trued. If your gunsmith is doing both of these to your rifle, you need a new gunsmith. If he is doing a real job of trueing the action, it will need the action threads trued along with the face of the receiver, the bolt and bolt face including the receiver lugs and the bolt lugs. There are just too many guys out there who do not do the complete job.

When the receiver threads get recut, the original barrel threads will be too loose in the action. To do it right, you need a new barrel. Simply facing the receiver won't cut it. </div></div>

I think Randy Cain or R&D would disagree, here is his "Maverick Package" on customer's Remington 700:
True action, bolt, and factory barrel. Push barrel back and re-cut chamber. Cut and re-crown barrel. My tactical bolt mod. Re-finish in single color Moly or Duracoat.

From what I have seen of this package it makes a real shooter
 
#14
Re: 300 Win Mag Chamber

If the 300 Win Mag is headspaced with a headspace gauge, then the headspace will be ~ 0.2201".

I chamber 300 Win Mag rifles with ~0.2150" headspace [.005" tighter], because all the magnum brass I can find will still fit.

cd300winchestermagnum.jpg


 
#15
Re: 300 Win Mag Chamber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: adam boynton</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jim Kobe</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: smokshwn</div><div class="ubbcode-body">I am sure this is a repeat but after searching until my vision is blurry, I gotta ask the question.

I have a Rem 700 in 300 Win Mag that is getting the action trued and barrel set back. In looking at the reloading forum I have decided I would like to run the 210 bergers or the 208 Amax's. However occasionally it would be nice to shoot factory length ammo as well without losing out on good accuracy.

Do I have the gun throated to accept these bullets loaded long (3.50ish) or do I go with a standard throat and load these bullets shorter (3.35ish)?

Thanks in advance, Craig </div></div>

Here is something to think about. You mentioned you are having the barrel set back AND the action trued. If your gunsmith is doing both of these to your rifle, you need a new gunsmith. If he is doing a real job of trueing the action, it will need the action threads trued along with the face of the receiver, the bolt and bolt face including the receiver lugs and the bolt lugs. There are just too many guys out there who do not do the complete job.

When the receiver threads get recut, the original barrel threads will be too loose in the action. To do it right, you need a new barrel. Simply facing the receiver won't cut it. </div></div>

I think Randy Cain or R&D would disagree, here is his "Maverick Package" on customer's Remington 700:
True action, bolt, and factory barrel. Push barrel back and re-cut chamber. Cut and re-crown barrel. My tactical bolt mod. Re-finish in single color Moly or Duracoat.

From what I have seen of this package it makes a real shooter </div></div>

Exactly. The action has been trued, barrel set back, threads recut and the chamber will be recut.

This work has been done. I am looking for advise/experience with varying the chamber specs.

BigBore and Jumper hit it on the head. Do I set the chamber up for optimum performance with factory length rounds and compromise the length at which I can seat reloads thus losing a little case capacity/bullet performance or do I cut the chamber for the reload spec and sacrifice factory load performance.

It is in this area that I would love to hear of others experience and opinion.

Thanks, Craig
 
#16
Re: 300 Win Mag Chamber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: smokshwn</div><div class="ubbcode-body">

Exactly. The action has been trued, barrel set back, threads recut and the chamber will be recut.

This work has been done. I am looking for advise/experience with varying the chamber specs.

BigBore and Jumper hit it on the head. Do I set the chamber up for optimum performance with factory length rounds and compromise the length at which I can seat reloads thus losing a little case capacity/bullet performance or do I cut the chamber for the reload spec and sacrifice factory load performance.

It is in this area that I would love to hear of others experience and opinion.

Thanks, Craig </div></div>


i am thinking when i order my chamber reamer, i am going to have it set so the 210 vld is at the lands with a 3.6" oal. this will give me a little bit of room to chase the lands or seat further into the lands and still have mag fed ammo. factory match ammo will most likely work just fine with what ever jump it ends end up with. since i haven't cut a belted case chamber, i also want to discuss with dave kiff the best method to ensure i headspace off the shoulder while still allowing any piece of virgin brass to fit. i would assume this would push the belt cutout further into the chamber.
 
#17
Re: 300 Win Mag Chamber

I would set up that chamber for the match bullets.
What you need is a parallel throat at .3085" .
Then the factory loads will still shoot fine even if jumping to the lands.

I remember an older Ruger 77 (Douglas barrel)in .300 Win. that shot handloads and factory very well like .3 -5 rounds @100 with a throat much longer than the magazine.

http://www.saami.org/Publications/

http://www.saami.org/Publications/206.pdf

http://www.poliisi.fi/intermin/images.nsf/files/AE55118F4B9B6506C2256FBE0032C6DE/$file/TABIcal.pdf

I make my 7mm Rem cases from .300 Win brass so that I can set the shoulder at my actual chamber size- shoulder -001" .
Jim Borden had an article in Precision Shooting discussing chamber reamers for .300 Win. and 7mm Rem. Email him and I am sure that you will have an answer within a few days.

You can get RWS brass from Canada. It's expensive .



Glenn
 
#18
Re: 300 Win Mag Chamber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jim Kobe</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: smokshwn</div><div class="ubbcode-body">I am sure this is a repeat but after searching until my vision is blurry, I gotta ask the question.

I have a Rem 700 in 300 Win Mag that is getting the action trued and barrel set back. In looking at the reloading forum I have decided I would like to run the 210 bergers or the 208 Amax's. However occasionally it would be nice to shoot factory length ammo as well without losing out on good accuracy.

Do I have the gun throated to accept these bullets loaded long (3.50ish) or do I go with a standard throat and load these bullets shorter (3.35ish)?

Thanks in advance, Craig </div></div>

Here is something to think about. You mentioned you are having the barrel set back AND the action trued. If your gunsmith is doing both of these to your rifle, you need a new gunsmith. If he is doing a real job of trueing the action, it will need the action threads trued along with the face of the receiver, the bolt and bolt face including the receiver lugs and the bolt lugs. There are just too many guys out there who do not do the complete job.

When the receiver threads get recut, the original barrel threads will be too loose in the action. To do it right, you need a new barrel. Simply facing the receiver won't cut it. </div></div>
To the best of my knowledge, when a barrel is set back, you usally cut the threaded tenon off which means you are resizing this newly cut end to match the recoil lug and the thread to fit. In most cases you have gobs of metal to work with.
 
#19
Re: 300 Win Mag Chamber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jim Kobe</div><div class="ubbcode-body">

Here is something to think about. You mentioned you are having the barrel set back AND the action trued. If your gunsmith is doing both of these to your rifle, you need a new gunsmith. If he is doing a real job of trueing the action, it will need the action threads trued along with the face of the receiver, the bolt and bolt face including the receiver lugs and the bolt lugs. There are just too many guys out there who do not do the complete job.

When the receiver threads get recut, the original barrel threads will be too loose in the action. To do it right, you need a new barrel. Simply facing the receiver won't cut it. </div></div>

Not necessarily. Nothing is absolute and my 20 years of building questions the "won't cut it" statement. There are a lot of things related to rifle building that are not internet and pre-internet fact.
 
#20
Re: 300 Win Mag Chamber


I doubt that truing the receiver face OR chasing the chasing the action threads would bring a measurable accuracy increase to smokshwn's Rem700 300Win mag shooting 210 gr bullets.

If the throat is shot out, I suspect setting the barrel back WILL make a measurable improvement.
 
#21
Re: 300 Win Mag Chamber

When figuring out a reamer I have taken a few things into account...

1. OAL for mechanical function in the action or magazine (if mag fed).

2. Seating depth for adequate bearing surface to be held by case neck. Too little bearing surface in the neck and the case will not obturate completely before the bearing surface leaves the mouth.

3. Seating depth so that the bullet occupies as little space as possible below the neck shoulder junction. No sense in seating so deep as to reduce powder volume.

4. Once a dummy round with the bullet of choice has been set up with the above taken into account, measure case head to ogive length and compare findings to factory ammo dimensions (if you're ever going to use factory ammo). Additionally, compare optimized dummy round to dummy rounds with other bullets set up to the same head to ogive length to see how they meet the above criteria.

5. Send measurements or the optimized dummy round to Dave Kiff and have a reamer cut.
 
#22
Re: 300 Win Mag Chamber

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Clark</div><div class="ubbcode-body">
I doubt that truing the receiver face OR chasing the chasing the action threads would bring a measurable accuracy increase to smokshwn's Rem700 300Win mag shooting 210 gr bullets.

If the throat is shot out, I suspect setting the barrel back WILL make a measurable improvement. </div></div>

I agree however if this is a factory barrel I would forgo that and just re-barrel it.

The chambers in Remington barrels are not cut they are formed during the hammer forging of the barrel. This hammer forging can work harden the barrel to the point that it becomes a PITA to cut. I have actually seen a few magnums that the reamer wouldn't touch. So taking the chance with the factory magnum barrel isn't as successful as doing this set-back with the .223 or the one that benefits from it the most the .308. It can be but one would want to look at the cost benefit of the whole process compared to just getting a new barrel.
 
#24
Re: 300 Win Mag Chamber

Ok we do this type of thing to customers rifles all the time. if you have a lot of rounds through the barrel i would just junk it and replace it with a match barrel because of the cost of the rechamber is usualy not cost effective when droping it into a half worn barrel but they also can shoot well again.

As for the chambering to make the standard reamer work by headspacing of the shoulder you chamber the exact same way. like mentioned above to make the rims closer fit short chamber it 4 or 5 thou just make sure the brand of cases you use will not be thicker than the rebate. i have even done a 470 this way and it is better.

The diference in the headspacing of the shoulder comes into when you reload you set the die up to give the minimum amount of case sizing so ti headspaces like a 308 of the shoulder so you set the dies up just like you would with a 308 and the best wat to achieve it is with a slightly tight or shorter chamber.

Now for the OAL to set the rifle up for as mentioned above chose the brass and projectiles you want to use then seat a dummy round of the longest length you want to use and the shortest length and see if the projectiles you are using will work loaded to the same throat length.

Remember projectiles like 190gr MatchKings will shoot with lots of freebore so dont worry about factory. it should shoot if the chamber is true.

I would look at using Lapua cases and have Dave Kiff make you up a reamer in Match Specs to suit the Lapua cases and Redding Type S dies. this means it will work when you come to reloading aswell. if your smith has a match 300mag reamer like us he can then throat the chamber with a seperate throating reamer to what ever leangth you like of send the dummy round with the projectile seated to where it should work for you and he will make you the reamer you need. Dave should be able to spec your reamer over the phone as he has most match projectiles there to reference. Call him up and say you want 208 A Max's seated so the boat tail is above the doghnut and using Lapua cases then you should be able to shoot anything through it.
 
#25
Re: 300 Win Mag Chamber

IMHO unless you are looking for something specific (like driving 240's or some such) I would cut to the chase and have it cut with an A191 chamber. It's a bit "throatier" than a factory chamber, specifically to roll the military A191 round.

Cheers,

Doc
 
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