05 November 2016, 09:09
EXPRESSrechambering - grinding recoil lug instead of setting barrel back?
I would like to rechamber my 7mm-08 to 7SAUM.
it seems the 7SAUM would need another 0.065" of depth to get a proper chambering.
Being as little as it is, would it be easier to grind/mill the recoil lug instead of intervening on the threads?
05 November 2016, 16:50
sliversIf were talking Remington 700, your recoil lug will end up being less than 1/8" thick (if were talking 'factory' recoil lug/barrel bracket)and you'll be 'intervening on the threads' to get the now thinner lug (barrel bracket) 'squeezed' between the action and barrel, you will run out of threads . You will have some serious work ahead of you making a rifle , original set-up for 7mm/08 Rem. feed that 7MM SAUM. IMO, more trouble than what it's worth. And, if you could ever get it accomplished, the strength of the recoil lug (barrel bracket) will have been compromised.
05 November 2016, 18:44
Jim Kobequote:
Originally posted by EXPRESS:
I would like to rechamber my 7mm-08 to 7SAUM.
it seems the 7SAUM would need another 0.065" of depth to get a proper chambering.
Being as little as it is, would it be easier to grind/mill the recoil lug instead of intervening on the threads?
Don't understand the question, If a rechamber is desired, why cut the recoil lug? For this conversion, why would you not just deepen the chamber? I guess I don't understand this. If going to a longer cartridge you need to deepen the chamber.
It probably won't feed anyway. Sorry, but I am confused.
05 November 2016, 20:11
sliversI hadn't bothered to look, but SAAMI says the case length for both the 7mm/08 Rem and the 7mm SAUM is 2.035" -.020. Rechambering a factory barrel is rarely worth the effort or the cost.
05 November 2016, 20:31
WoodHunterYou will never have a flat lug if you try to grind the standard M700 lug. Plus you will make a too thin lug even thinner, yes they will bend under recoil.
The M700 lug is junk anyway, this is why we replace it with a nice thicker lug.
No flies on a 7mm08, fooling with the SAUM is generally a waste of time and invites feeding problems as Jim mentioned.
And as Jim says I think you have the operation backward.
05 November 2016, 20:52
jplThe SAUM is also a magnum bolt face. Check out the 284 Win. That's a bigger 7mm that uses the 308 bolt.
05 November 2016, 22:20
LuckyduckerI am trying to understand this topic. If you are rechambering the barrel anyway what is so difficult about setting the barrel back a little bit. The barrel will have to be headspaced which might require some setback to get it right.
05 November 2016, 22:25
WoodHunterquote:
Originally posted by Luckyducker:
I am trying to understand this topic. If you are rechambering the barrel anyway what is so difficult about setting the barrel back a little bit. The barrel will have to be headspaced which might require some setback to get it right.
Maybe trying to do it without a lathe: T-handle on the reamer. Guarantees a non concentric chamber/throat.
05 November 2016, 22:41
EXPRESSOK;
the barrel is a custom - Krieger with just a couple of hundred rounds through it.
My idea of grinding the lug was because I didn't want to have to cut anymore of the shank, because it is already a featherweight profile. Aslo, the lug is a custom, thicker lug.
However, once you have it set up and dialed in, I realized that taking a few though off the threads and shoulder isn't going to be a problem.
The same rifle comes from the factory chambered in both 7mm-08 and 7saum in this same action and model (Titanium), so feeding should not present a huge problem.
Yes, the bolt face will need to be opened up, but I got this with a 1:8.5 twist to shoot heaver bullets and it just hasn't satisfied me in either accuracy or oomph. It is getting a brake and new stock and hopefully will find it's final configuration.
The barrel has been gathering dust for years since I had it pulled, so I'm not really risking much.
Best I can tell, the 7saum is:
0.0216" shorter at the bottom of the shoulder
0.0268" shorter at the top of the shoulder
0.0107" shorter over case length
So it should only need 0.0268 taken off the stub in order to headspace properly, right?
06 November 2016, 00:26
LuckyduckerShould be something around that number.
07 November 2016, 04:06
jplquote:
Originally posted by EXPRESS:
Yes, the bolt face will need to be opened up...
Looks to me like a 284 reamer would clean out a 708 chamber. No need to mess with the lug or threads or bolt face.