Just measure my chamber, very long CBTO

4guyz1stool · Dec 20, 2019

I just used the Hornady Lock and load to measure the chamber in my Remington 700 (308). It does not look like the ELDX 178 I purchased are going to fit in my Magpul AICS mags unless I back off of the lands considerably.

Has anyone filed down the front of those mags so they can fit longer bullets?
How far off the lands is too far to gain any precision advantage over buying match ammo?
I'm probably going to buy some Accurate mags since they are longer, but I don't want to have a bunch of useless Pmags lying around if I can help it.

steves1911 · Dec 20, 2019

My rem 700 in 308 is the same. I have some loads that jump .10 but still shoot 1/2 moa. Lots of factory barells are like this but still shoot fine.

pcfixer · Dec 24, 2019

steves1911 said:
My rem 700 in 308 is the same. I have some loads that jump .10 but still shoot 1/2 moa. Lots of factory barrels are like this but still shoot fine.

I haven't measured my LR-308 DPMS, but shoots MOA with only some
powders. 2.800 does fit into HexMags.

Pinecone · Dec 24, 2019

Rem 700s are known to have long throats.

Why not shoot it and see how it does. If you need to shorten the chamber, a good smith can do it. They remove the barrel, cut a bit off, then rechamber.

When I did my OCW with Sierra Match King 175s, the longer I got them, the smaller the group, out to max mag length. And at that point, the groups were quite good.

If I need more, I will rebarrel with a precision barrel.

4guyz1stool · Dec 26, 2019

Can you recommend any gunsmiths that can do this type of work?

E.Shell · Dec 26, 2019

Pinecone said:
Rem 700s are known to have long throats.

Why not shoot it and see how it does. If you need to shorten the chamber, a good smith can do it. They remove the barrel, cut a bit off, then rechamber.

When I did my OCW with Sierra Match King 175s, the longer I got them, the smaller the group, out to max mag length. And at that point, the groups were quite good.

If I need more, I will rebarrel with a precision barrel.

This.

I have bore scoped 50 or 60 Remington rifles and have also set up students' dies for a few dozen Remington .308s and the long/rough/crooked throat problem is both well known and seldom a real issue. Some are scary-bad... I have an LTR in .308 with a throat that cannot be reached and looks like a kid did it, but it consistently shoots FGMM into 1/2 MOA and often will put three into one hole. I do not know why.

Load your ammo to feed RELIABLY through the mag and be happy...unless it actually doesn't shoot well, then just rebarrel it.

Rebarrelling is usually the best option, for several reasons:
1) The OEM Remington barrel is probably not worth the gunsmithing labor to re-work it. Most of the cost in precision rifle work is labor and most 'smiths will tell you not to bother with the factory tube. For about the same labor, I'd put a new barrel on it, and know that I can count on good results.
2) Usually, the chamber must be cut back pretty far to correct most of the conditions I have seen, and you may end up with a lot less barrel, especially since you will also want to re-crown it while he has it off the rifle.
3) Many/Most gunsmiths don't like cutting a new chamber in a used barrel unless you provide the reamer and understand that it may be damaged from this application. Reason being that the chamber area will be work-hardened by firing and will kill a reamer unless hogged out with carbide first, contributing to the loss of length. Learned this for myself the hard/expensive way.

As an aside, many folks get caught up in absolute rifle accuracy and don't really shoot well enough to consistently demonstrate a difference. If you can't shoot 1/2" groups at 100 yards with a good rifle and Federal Gold Medal match 168s/175s, the long throat isn't the impediment to accuracy it may initially seem.

As Pinecone suggests, don't holler before you're hurt. Try the rifle, it may be fine.

Pinecone · Dec 26, 2019

Gunner421 said:
Can you recommend any gunsmiths that can do this type of work?

I have not used anyone locally.

But I have used Short Action Customs in Ohio and Long Rifles Inc in Sturgis, ND.

Both do SUPERB work, and quickly.

4guyz1stool · Dec 26, 2019

E.Shell said:
This.

I have bore scoped 50 or 60 Remington rifles and have also set up students' dies for a few dozen Remington .308s and the long/rough/crooked throat problem is both well known and seldom a real issue. Some are scary-bad... I have an LTR in .308 with a throat that cannot be reached and looks like a kid did it, but it consistently shoots FGMM into 1/2 MOA and often will put three into one hole. I do not know why.

Load your ammo to feed RELIABLY through the mag and be happy...unless it actually doesn't shoot well, then just rebarrel it.

Rebarrelling is usually the best option, for several reasons:
1) The OEM Remington barrel is probably not worth the gunsmithing labor to re-work it. Most of the cost in precision rifle work is labor and most 'smiths will tell you not to bother with the factory tube. For about the same labor, I'd put a new barrel on it, and know that I can count on good results.
2) Usually, the chamber must be cut back pretty far to correct most of the conditions I have seen, and you may end up with a lot less barrel, especially since you will also want to re-crown it while he has it off the rifle.
3) Many/Most gunsmiths don't like cutting a new chamber in a used barrel unless you provide the reamer and understand that it may be damaged from this application. Reason being that the chamber area will be work-hardened by firing and will kill a reamer unless hogged out with carbide first, contributing to the loss of length. Learned this for myself the hard/expensive way.

As an aside, many folks get caught up in absolute rifle accuracy and don't really shoot well enough to consistently demonstrate a difference. If you can't shoot 1/2" groups at 100 yards with a good rifle and Federal Gold Medal match 168s/175s, the long throat isn't the impediment to accuracy it may initially seem.

As Pinecone suggests, don't holler before you're hurt. Try the rifle, it may be fine.

Thanks. I'm going to AGC next week to work up my first load. Hopefully it shoots well right off the bat.

I agree with you that I would probably just rebarrel it if it came down to that.

4guyz1stool · Dec 26, 2019

Pinecone said:
I have not used anyone locally.

But I have used Short Action Customs in Ohio and Long Rifles Inc in Sturgis, ND.

Both do SUPERB work, and quickly.

Awesome. I will check out their websites. :party29:

Nanook · Dec 26, 2019

Gunner421 said:
Thanks. I'm going to AGC next week to work up my first load. Hopefully it shoots well right off the bat.

I agree with you that I would probably just rebarrel it if it came down to that.

And if you can't make it go worth a darn, see if you can get in one of E Shell's sessions before you do expensive gun surgery. Lots of members here have come away much better distance shooters.

rbird7282 · Dec 26, 2019

Nanook said:
And if you can't make it go worth a darn, see if you can get in one of E Shell's sessions before you do expensive gun surgery. Lots of members here have come away much better distance shooters.

I don't believe Ed teaches anymore. I still learn more from one of his posts than probably an entire book.

Nanook · Dec 26, 2019

rbird7282 said:
I don't believe Ed teaches anymore. I still learn more from one of his posts than probably an entire book.

Well....damn. Looks like I missed my window.

I thought I understood reading a mirage until the Atlantic Fleet matches in 2012 (2011?) when I snuck a stool and a scope behind Major Ed Land and Commander "Walt" Walters on Quantico's Range 4. They were the OICs of the Marine and Navy teams long ago and by then had been long retired. Listening to two living legends and friends, sitting in the sun and quietly calling the seemingly random wind changes to each other, as I looked through my scope and learned was one of the neatest things I have ever done. One day I hope to be good enough to learn half the stuff they forgot.

E.Shell · Dec 26, 2019

Very sorry guys, but I'm out of it. Thank you for your kind words though!

Dan Newberry at BanG Steel does a great job. Not too bad a run down I-81.

PowPow · Dec 26, 2019

rbird7282 said:
I don't believe Ed teaches anymore. I still learn more from one of his posts than probably an entire book.

Ed's posts on shooting-related topics are always sticky material! (Thanks, Ed)

KRC · Dec 27, 2019

You might consider trying another bullet with a different ogive, one that gets the bullet closer to the lands with the same COAL. (You may have to research and/or experiment.) I've not modified M700 mags, but have made "window" mags for two of my AR's, one in .223 Wylde and the other in 224Valkyrie. The 224V only performs with bullets loaded to a COAL of 2.340", which is only possible with the modified mag.

Pinecone · Dec 27, 2019

Since Ed is not teaching, Dan Newberry at Bang Steel is a bit further away, but also very good.

Dan can also help with working up your load. If you sign up for a course, he may not charge consulting fees for a few questions on your load.

Surt · Dec 27, 2019

I have a 300 WinMag Rem 700 I've noticed likes a longer jump with heavier bullets. My Krieger barrel 1/10 on this particular rifle has the lands .04" longer than standard, and I use a Berger 200.20X hybrid bullet with a longer ogive than normal. These bullets, even though I seat them long, still have a .084" jump to the lands, and they do spectacular past 200m.

I'd say don't over-game the problem. If you're not seeing pressure signs, try seating them just a smidge deeper and see if they don't actually work better or just the same that way. The only thing to look out for I would say is that the case neck is still in contact with the bearing surface and again, keep an eye for pressure signs.

Park ranger · Dec 28, 2019

Surt said:
I have a 300 WinMag Rem 700 I've noticed likes a longer jump with heavier bullets. My Krieger barrel 1/10 on this particular rifle has the lands .04" longer than standard, and I use a Berger 200.20X hybrid bullet with a longer ogive than normal. These bullets, even though I seat them long, still have a .084" jump to the lands, and they do spectacular past 200m.

I'd say don't over-game the problem. If you're not seeing pressure signs, try seating them just a smidge deeper and see if they don't actually work better or just the same that way. The only thing to look out for I would say is that the case neck is still in contact with the bearing surface and again, keep an eye for pressure signs.

Good post.

Just measure my chamber, very long CBTO

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