Re-chamber for 7RM Question...

[crazyhorse]

After 5 years it appears I've finally shot out my current barrel (Benchmark) and have already ordered a new 9 twist Bartlien as a replacement.

My question is in the value of having a custom reamer made to allow a longer seat to shoot 160-180gr bullets. Additionally my thinking is since I would own the reamer, it stands to reason I could get somewhat repeatable results or at least closer than the saami reamer my smith uses numerous times per year and will likely replace before I need another barrel. My thoughts are to measure the mag box and get a number based on the longest bullet I would use (175 Berger Hybrid or 175 ELD) and have it made. If this is feasible I would likely have custom dies made to further narrow the variables in hopes of consistent, repeatable results from barrel to barrel.

Has my boredom today caused irrational thinking, or am I just picking pepper out of the fly poop?

 

[joseph singleton]

I'm going to sit back and listen,LIKE UR PICKING PEPPER

 

[MagnumManiac]

I design my own reamers and have JGS make them.
Admittedly, I work off A191 prints for 300WM and 264WM to get minimum brass expansion. I also measure the CBTO on a round that fits my mag length with the bullet I will use. My mag length is 3.6" on my comp guns, so I load to just shy of that.
Normally, I run a throat length of .200"-.220" , even in my hunting rifles, this allows me to use VLD's that are at the heavy end for caliber.

So, yes, a custom reamer is definitely worth the cost and trouble, as you can set-back a thread and re-ream when the throat erodes.

Cheers.

 

[crazyhorse]

I design my own reamers and have JGS make them.
Admittedly, I work off A191 prints for 300WM and 264WM to get minimum brass expansion. I also measure the CBTO on a round that fits my mag length with the bullet I will use. My mag length is 3.6" on my comp guns, so I load to just shy of that.
Normally, I run a throat length of .200"-.220" , even in my hunting rifles, this allows me to use VLD's that are at the heavy end for caliber.

So, yes, a custom reamer is definitely worth the cost and trouble, as you can set-back a thread and re-ream when the throat erodes.

Cheers.

Have you used the same reamer on a barrel replacement? If so what was the result in terms of consistency from one to the next?

 

[Shawn the printer]

Watching this one.

 

[MagnumManiac]

Yes, chambers were within .001" of the 3 barrels, cases could be interchanged between the 3. Not that I do.
This is due to exacting machining of the barrel shoulder and headspace control. I set my headspace exactly at .220" for belted mags and .002"-.003" for non-belted cases. These are switch barrel rifles with pinned recoil lugs at .250" thick.

Cheers.

 

[crazyhorse]

Yes, chambers were within .001" of the 3 barrels, cases could be interchanged between the 3. Not that I do.
This is due to exacting machining of the barrel shoulder and headspace control. I set my headspace exactly at .220" for belted mags and .002"-.003" for non-belted cases. These are switch barrel rifles with pinned recoil lugs at .250" thick.

Cheers.

Thanks! This is the kind of info I'm looking to find.

The rifle is based from a blueprinted 700LA in a Manners EH-1 with the mini-chassis and BDL bottom. The mag box will allow bullets to be seated longer than practical so I just can't see a reason why a custom reamer with more throat and custom dies based off fired brass would be a bad idea.
Unless I'm missing something a $300-$400 investment in reamer and dies eliminates most of the variables we spend tons of time (and money) trying to eliminate from barrel to barrel, and will last as long as I want to keep using it.
I'm certainly not a gunsmith but have been shooting and reloading long enough to come up with this theory. I'm looking to borrow from the experience and working knowledge of this group to tell me why it's not worth the trouble or maybe I'm on to something.

 

[MagnumManiac]

Yes, you are onto a good thing, but note that you need to keep some wiggle room for other bullets, so a compromise on throat length needs to be made. All my 300's have throats that will accommodate the 230's as well as a 215. My 6.5'a are throated to match up with 140gr-142gr VLD's, their lengths vary, so a .200" throat works for most and, a .220" throat works for all.
You need to measure and re-measure until you find a happy medium.

Cheers.

 

[AZShooter]

I am absolutely sold on buying my own reamers with some specification changes. Being able to request throat length, throat angle, neck diameter, end of chamber distance etc can make a difference! My friend and I own 18 reamers between us.

Choose the brand brass you will use. Decide on how much bullet release clearance you require which may or may not include neck turning.

You can make a dummy round with your preferred bullet to ship to the reamer maker asking for contact with lands or any jump you want.

If you are not sure about throat angle a common one that works well with most bullets is 1 1/2 degree but some chamberings do well with other angles. Ask the reamer maker if you are uncertain.

I have found that many gunsmith reamers were either SAMMI and dull or altered in some way that the gunsmith thought was best. I have had mixed results with gunsmith's personal reamers for over 25 yrs till I decided enough was enough and started buying my own. Been using my own or Dan's reamers for close to 15 years and would never turn back.

Fyi did you know you can often have an existing reamer reground for far less than the original cost? Done that too.

From personal experience, Whidden makes excellent dies. Sure other posters can suggest other die makers as well.

 

[Innovative]

I wrote an article on this subject. It explains how to know you will end up with an accurate barrel .... before you spend the money.

http://www.larrywillis.com/Custom Barrel.html

It is a much better deal to purchase your own chamber reamer for your particular needs. This way you can use magazine length handloads with the exact bullet that you intend to shoot. This allows your particular bullet to contact the rifling if you prefer. It also explains how you can get great accuracy without turning your case necks.

 

[ZG47]

A gunsmith friend of mine, several years deceased, told me that there were basically two types of 'standard' reamer: factory reamers and gunsmith's reamers; the gunsmith's reamer having half the leade angle of the factory reamer, in his description. He also advised me that the gunsmith's reamer would only do six (6) or seven (7) barrels before needing to go back to the maker and be resharpened (under water by his particular supplier). I suspect that he was talking about chamber reaming without the prior use of a roughing reamer, but would need to consult with his younger brother or one of those sons whom he trained as gunsmiths, in order to confirm that speculation. Din Collings, my friend, had high standards and even got John Krieger to make him cut-rifled barrels to a spec that Mr Krieger would only do for him.
I could go into more detail, with the above assertions; but I am a carpenter, not a tool maker or gunsmith and I prefer to leave the finer details to those who better comprehend them.
This is definitely an interesting topic.

 

[Innovative]

ZG47 . . . .

You are right about the importance of using a roughing reamer . . . . then use a proper finish reamer. It's well worth the extra time and money if you value your finish reamers.

 

[drborsos]

Are you punching paper or hunting? Target shooting, go with the custom reamer. Hunting, standard SAAMI reamer will work just fine. Think, what bullet manufacturer are you going to use. Example, Berger - get the custom reamer. Barnes - don't bother.

 

[johnlittletree]

I design my own reamers and have JGS make them.
Admittedly, I work off A191 prints for 300WM and 264WM to get minimum brass expansion. I also measure the CBTO on a round that fits my mag length with the bullet I will use. My mag length is 3.6" on my comp guns, so I load to just shy of that.
Normally, I run a throat length of .200"-.220" , even in my hunting rifles, this allows me to use VLD's that are at the heavy end for caliber.

So, yes, a custom reamer is definitely worth the cost and trouble, as you can set-back a thread and re-ream when the throat erodes.

Cheers.

I agree 100% and was going to say much the same. Especially about doing a set back and re-ream. I used do that all the time prior to getting fantastic deals the last 2 years on match grade barrels at prices I could not say no to. I have done this often. Normally as as comp rig started to erode the throat it would get a set back and re-chamber and shorten the muzzle end and re-crown.This would then become a hand me down for a hunting rifle or if a friend or relative wanting to build a rig I would hand it down to them.

If it was a hunting rifle a set back and re-chamber is almost automatic unless it was an OEM factory barrel.