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7 SAUM freebore recommendations in a short action

mattmcg

mattmcg

Gunny Sergeant
Full Member
Minuteman
Apr 19, 2007
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CA
#1
I'm in the process of building a 7 SAUM on a Surgeon 591R short action. I'll be shooting the 7mm Sierra 180gr Matchkings and the 7mm Berger 180gr Hybrid bullets.

I am looking into a finishing reamer for the project and could really use some freebore dimension recommendations that would be optimal for the above setup. I've seen off the shelf 7 SAUM reamers with as little as 0.0900" on up to 0.2200".

Appreciate the advice in advance!
 
#2
Re: 7 SAUM freebore recommendations in a short action

Those 2 bullets have pretty different COL for the same relation to the lands. Do you plan to fit them in a magazine?
 
#3
Re: 7 SAUM freebore recommendations in a short action

What magazine are you using? AI, Alpha, or CDI? Big difference in what reamer you will use based on the mag.

I'm having a 7 SAUM built off the Alpha mags, which puts me at 2.950-ish" OAL. I loaded a blank round with the 180gr Berger Hybrid and sent it to Dave Kiff at PT&G and he is cutting me a custom reamer for that load.
 
#4
Re: 7 SAUM freebore recommendations in a short action

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: McFred</div><div class="ubbcode-body">Those 2 bullets have pretty different COL for the same relation to the lands. </div></div>

Yes they do!

I just did a one with .078 freebore for the Berger 180vlds-168vlds in a Alpha mag. The hybrids are going to be a lot different in setting length. If I load the hybrids to touch the lands. They are not even close to fitting in the Alpha mags.
 
#5
Re: 7 SAUM freebore recommendations in a short action

Yes, am planning on using the Alpha 300 WSM mags with a 2.985" OAL capability.

Perhaps the better question is what is the optimal freebore for either of these bullets?

If I use the SMK 180gr which is 1.455" long, what is the optimal freebore?

If I use the Berger 180gr Hybrid which is 1.525" long, what would it be?

FWIW, here is a link to a 7 Saum reamer from JGS with the 0.090" freebore. Link
 
#6
Re: 7 SAUM freebore recommendations in a short action

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JamesBailey</div><div class="ubbcode-body">What magazine are you using? AI, Alpha, or CDI? Big difference in what reamer you will use based on the mag.

I'm having a 7 SAUM built off the Alpha mags, which puts me at 2.950-ish" OAL. I loaded a blank round with the 180gr Berger Hybrid and sent it to Dave Kiff at PT&G and he is cutting me a custom reamer for that load.

</div></div>

Have you received a reamer print from Dave Kiff with the optimal freebore calculation? That would be an excellent resource to see what the print might look like.
 
#7
Re: 7 SAUM freebore recommendations in a short action

The best thing to do is send Dave a dummy round loaded with the Hybrid with an OAL to fit in the Alpha mag. Or just call them.

All the guns that i reload for that shoot the Berger vlds. Shoot good at touching or +.010 jammed into the lands. Not sure with the SMK. I think it will be tough to find a good free bore for both of the Berger and SMK.
 
#9
Re: 7 SAUM freebore recommendations in a short action

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mattmcg</div><div class="ubbcode-body">
JamesBailey said:
Have you received a reamer print from Dave Kiff with the optimal freebore calculation? That would be an excellent resource to see what the print might look like. </div></div>

Negative, I don't have print of it. I will see if my gunsmith does and will post it here if so.
Click to expand...
 
#10
Re: 7 SAUM freebore recommendations in a short action

Appreciate it JamesBailey.

Yeah, trying to piece together some brass and bullets now to build some dummy rounds.
 
#12
Re: 7 SAUM freebore recommendations in a short action

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mattmcg</div><div class="ubbcode-body">Appreciate it JamesBailey.

Yeah, trying to piece together some brass and bullets now to build some dummy rounds.

</div></div>

Matt-
I spoke w/ my gunsmith (Jeff Walker, Walker Custom Rifles, Culpepper VA). The custom reamer is not in yet from PT&G, so we don't have a print on it yet. I will try to remember and post it to you once I get it.

In the mean time, did you see a 7SAUM w/ 180g Hybrids won the US National Open F-class match recently? Clearly, this chamber/bullet combo has outstanding long range potential.


 
#14
Re: 7 SAUM freebore recommendations in a short action

Got ahold of the PTG reamer print today and only a few minor differences between the two. The PTG also has a 0.0900" freebore as well.

Would love to know the justification for that and what it was designed for.
 
#15
Re: 7 SAUM freebore recommendations in a short action

Well, that print you have from JGS is the SAAMI print, so I imagine that the PT&G print is also SAAMI. SAAMI is built around a 2.85-ish" OAL, which isn't optimal for you if you are going w/ the Alpha mags at 2.95-ish".
 
#16
Re: 7 SAUM freebore recommendations in a short action

Couple thoughts:

I am building a 284win on a short action with Alpha 300wsm mags. From what I can tell by loading some dummy rounds and loading the magazine, count on ~2.950" MAX COAL. Any longer and they tend to bind/drag. I did this with 162amax, perhaps the plastic tipcreates more drag in the box.

Assuming a loaded COAL of ~2.95", most of the high BC 7mm bullets are gonna need between .070" and .100 freebore. In my application, which is designed around the 162amax, .088" FB was the magic number.

Good luck! I considered the 7RSAUM briefly before settling on 284.
 
#17
Re: 7 SAUM freebore recommendations in a short action

Hey, just a heads up for anyone building a 7 SAUM:

Midway has 7 SAUM brass from Nosler Customs in stock (this was a long wait for me). Its $50/50pcs. Given how expensive the Remington brass is (close to $0.70), this ain't a bad price.
 
#18
Re: 7 SAUM freebore recommendations in a short action

I just went to order some and it is backordered already....and the back in stock date is Sept 2012! I have been waiting for months for this brass as well....I guess you snooze you lose.
 
#19
Re: 7 SAUM freebore recommendations in a short action

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kgw43</div><div class="ubbcode-body">I just went to order some and it is backordered already....and the back in stock date is Sept 2012! I have been waiting for months for this brass as well....I guess you snooze you lose. </div></div>

Sorry KGW-
I saw it in my inbox this morning and I immediately bought 200 pcs at 0800 hours east coast time. Not sure why Nosler doesn't make more given the clear demand. Maybe Nosler is tight because Norma isn't making enough brass for them.
 
#20
Re: 7 SAUM freebore recommendations in a short action

I guess a guy can always neck down the 300 Saum brass, I was just excited about having a good quality brass option ready to go out of the box.
 
#21
Re: 7 SAUM freebore recommendations in a short action

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Gofaster23</div><div class="ubbcode-body">It seems like everyone has a 7 SAUM in the works. It's hard to keep up with the jones's around here!</div></div>

Haha! I know what you mean. I have a couple 7mm SAUM projects lined up. We will be getting started on Dane's after we get some 6.5mm busted out.
 
#22
Re: 7 SAUM freebore recommendations in a short action

Today I called up Kerry (sp?) at JGS Precision and talked a little about modifying their standard SAAMI 7 RSAUM print to tighten up the specs around the Sierra 180gr 7mm HPBT.

I'm in the process of putting some dummy rounds together to have mic'd and then send them up to JGS for a new draft print. I'll post it here once I've completed the project.
 
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