7-300 Win chamber issues


Well-Known Member
May 23, 2012
Hey all,

So I had a 7-300 win built for me by Rbros rifles late last year and love everything about it! I love it so much I wanted to build one for my Dad. I called PTG and talked with Dave and ordered a 7-300 win reamer with no shoulder changes and a long throat for a 180 vld. I got an email with the print, and I'm no pro at reading prints, but everything looked great. First pic is that print

Six days later I got another email from PTG with what I thought was the same print, but it said 7mm pratical. I didn't look it over very well, and now I notice that it has a 30 degree shoulder. The reamer showed up, I gave it to my gunsmith and he cut the chamber. A 300 win go gauge closes in the chamber just fine, but I couldn't get the brass I had prepared to chamber. On closer inspection, I realized that the reamer does have a 30 degree shoulder angle and a longer neck. Looking at the print, its very similar to the balistic studies 7mm Practical.

SO, my question is this. I feel like the chamber needs to be cut deeper to acomodate a 30 degree shoulder, but if the go gauge fits as it is, it seems obvious that cutting the chamber deeper would create some serious headspace issues. My thought would be to take the brass I prepared for my other 7-300 that chambers just fine, and cut the problem chamber deep enough to chamber my prepared brass. Then would the brass not fire-form to a 30 degree shoulder and I could continue life as normal with my redding type s neck die?? Any comments would be greatly appreciated.


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sable tireur

Well-Known Member
Oct 8, 2010

I will cover just a couple of the high spots in your situation without the benefit of talking to Dave Kiff about this.

First and foremost, Dave (or whomever) should not have sent you a drawing of another reamer design if you specified yours originally without stating that they had one of the latter in stock and asked if they could substitute. Then, they should not have sent the second reamer without asking if that was acceptable to you.

You should have contacted them and asked questions about why the two sets of prints and what the differences were.

Failing this, your gunsmith should have read the information about the reamer on the shank of the reamer then asked you about whether or not it was acceptable. He should have checked the prints first also.

Your solution will not work since the headspace will be wrong. These two cartridges headspace on the belt until fireformed and neck sized only, at which point you can call the shoulder your headspace feature if you want. By deepening the chamber, you are pushing the belt deeper which deepens the headspace. The belt and the shoulder are always in relations to each other since they are ground into steel.

Even with the oversights by you and your gunsmith, I would contact Dave personally, not one of his helpers, in order to resolve this issue.

This is a quick evaluation due to a lack of time. Other details of the dimensional differences will have to wait.



Official LRH Sponsor
Mar 26, 2006
Tumwater, WA
First off, Rbros didn't chamber the rifle in question, just to clarify that.

Denton, have your smith set the barrel back 2 turns and recut with a straight 7-300 reamer. This will cleanup the 7 practical chamber.



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