Reamer recs for 7mm rem mag

[pmr14]

Hello,

Hoping to use the Berger 190gr and 184 in my new 7mm barrel. Have an 8 twist that needs to be reamed in rem mag.

Looking for recommendations for lengthening the freebore from the standard SAAMI spec to accommodate the longer 190 grain bullet for accuracy. I believe the overall length of the bullet is 1.601". I am not planning on magazine feeding.

Any other recommendations would be appreciated.

Thx
RG

 

[crazyhorse]

I went through a very similar situation with my 7RM and the Berger 175 EH.
Loaded a dummy round with ADG brass, sized with my die and bullet seated where I wanted it. Sent it off to JGS (preceded by a phone call of course) and waited a couple months for them to finish. They did an awesome job and hit the delivery date spot on.

The result is a 7RM that shoots incredible with average velocity for the 175's at 3059fps verified by magneto speed. The cool unintended consequence is the standard 160 Accubond, due to having the ogive much further forward seats with the base of the boat tail just past the neck shoulder junction and I'm getting a scorching 3150fps using IMR8133 with no pressure signs and it shoots great.

 

[pmr14]

Crazyhorse,

Did you get the standard SAAMI 7mm rem mag spec for your freebore?

I will likely call one of the reamer companies to help me identifying the amount of freebore clearance needed.

Btw, those are some crazy speeds you are posting.

Thank you,

Rani

 

[crazyhorse]

Crazyhorse,

Did you get the standard SAAMI 7mm rem mag spec for your freebore?

I will likely call one of the reamer companies to help me identifying the amount of freebore clearance needed.

Btw, those are some crazy speeds you are posting.

Thank you,

Rani

I had the free bore set based on my dummy round and requested an additional .005. This gave me enough room to play around with seating depth but not so much that I can't chase the lands with a bullet already seated way out there.

I was amazed by the velocity gains that come from getting the bullet further out of the case and allowing for more of the slow burning powders such as Retumbo and IMR 8133. I'm only .5gr past book max on the Accubond load but it would certainly be a compressed load without the additional freebore. As it stands now there's no "crunch" when seating but it's definitely full.

 

[crazyhorse]

My inspiration came from a few threads on here about people doing similar things with the 300WM and the 215 Berger Hybrid.

 

[keithcandler]

We are getting 3060 with Berger 180's with std freebore, in 26" Rem ss sendero's using R#26.

A standard load of 71.0g of Retumbo with fed 215's and 168g bergers is 3100, work up to this load in your rifle, not for federal brass.

Pard is shooting a 28" barrel and shoots the 160g AB 's at 3200 with about the same load. I don't know the freebore on his reamer.


my PTG 7 Rem Mag match reamer is .115 fb with 3* leade angle, .307 neck which is a turn neck to clean up
PTG 8/14

Many gunsmiths have unithroaters and can throat pretty close to what you want.

 

[crazyhorse]

I'm shooting a 26" barrel.

The 175 Berger load is .5 below book max using Retumbo and the 160 AB load is .5 above book using IMR 8133, both with no sign of pressure.

 

[FURMAN]

I would want .200 plus for the 175-180. I would probably want .250-.280 for the 190-195. I would probably split the difference and go ~.220 to compromise for all of them.

 

[pmr14]

I would want .200 plus for the 175-180. I would probably want .250-.280 for the 190-195. I would probably split the difference and go ~.220 to compromise for all of them.

Rfurman24,

I have shot the 180 hybrids in a standard SAAMI spec chamber which I believe has a freebore of ~.115. The gun shoots extremely well. Have about 1k rounds in the barrel.

With the longer bullet of about 60 thousands, I am thinking increasing it but I am afraid your numbers would be too great. I am thinking about this correctly. I was thinking like 20-30 thousand. Like a freebore of .135-145.

Rani

 

[FURMAN]

Rfurman24,

I have shot the 180 hybrids in a standard SAAMI spec chamber which I believe has a freebore of ~.115. The gun shoots extremely well. Have about 1k rounds in the barrel.

With the longer bullet of about 60 thousands, I am thinking increasing it but I am afraid your numbers would be too great. I am thinking about this correctly. I was thinking like 20-30 thousand. Like a freebore of .135-145.

Rani

Yes I've shot countless 180s out of a couple different Sammi spec chambers we don't shoot or pick chamber dimensions because a bullet will or will not shoot we choose it for optimal performance go check a Sammi chamber and see how much of that 180 is down in the case if you're building a reamer you might as well get it right. The optimal freebore for 180 grain bullet is roughly .200 to .220 the bigger bullets need more most guys are running in the 280 range. It is your rifle do what you want I'm telling you what the optimal numbers are.

 

[pmr14]

Yes I've shot countless 180s out of a couple different Sammi spec chambers we don't shoot or pick chamber dimensions because a bullet will or will not shoot we choose it for optimal performance go check a Sammi chamber and see how much of that 180 is down in the case if you're building a reamer you might as well get it right. The optimal freebore for 180 grain bullet is roughly .200 to .220 the bigger bullets need more most guys are running in the 280 range. It is your rifle do what you want I'm telling you what the optimal numbers are.

Thank you for your insight. I will follow your lead and info and talk to my gunsmith.

Appreciate it.

Rani

 

[X47guy]

I use a sammi spec reamer with the .115 freebore and then throat it to .180. I use the 180 eld m to take my measurements. You will need .190-.210 for the 184s. The 190s will need to be .210-.220 ish.

I am running the 180 eld m at 3150.

 

[keithcandler]

I am running .115 with the 180's at 3050 with R#26 and 215's in Rem brass shooting tiny groups, 9.25" Twist, Rem SS Sendero.

If I were to go with IMR 8133, perhaps I would see more velocity.

I have shot the 7 STW's with a zero freebore reamer shooting the 140's in the area of 3650, 27" pac nor three groove 11 Twist barrel. The same reamer has cut 7 Mag Sendero barrels that finish at 25" and shoot the 140g at 3550 and the 120's at 3850 shooting very small bug holes.

When you throat out, you decrease the accurate rounds you are going to get on the barrel, so go down this road with your eyes open wide. You will be replacing barrels more often with .190-.220 freebore because the 180's like to be near or touching the lands.

Current thinking for 180's is .190-.220 because the shooters are not smart or diligent enough to monitor for doughnuts, first, More velocity from throating out is a second reason, some think that the bullet's base being below the shoulder/neck junction is bad for accuracy, and finally seating the bullet out will allow room for more powder.

In choosing this freebore, Hunters may differ greatly from Target shooters due to barrel life and magazine constraints. This brings up another issue, is it logical for a long range hunter to ever use a magazine due to COAL to get close to the lands and magazine constraints?