Chambering a .260rem

Goose25

Goose25

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I have a new barrel that I'll be having chambered in .260rem. I'll mostly be using R-P 260 brass, but also have lots of .308 brass that I might end up trying later down the road. Will I need to neck turn my .308 brass to avoid chambering issues?

What should be the chamber dimensions (neck area ) to have a .260rem no-neck chamber(~.2970?)?

How much potential accuracy is given up between a tight neck chamber, requiring neck turning and a No-neck turn chamber?

Can I have my .260 chambered with a short throat and still shoot 140's without losing much case capacity?

Should I bother to send 2-3 pieces of brass to my gunsmith so he can use it to measure headspace when chambering my new barrel (use it as a go guage)? I'd use my Redding body die to FL-size my new unfired brass, I'd put a 3 to 5 thou shim under the lock ring so that the base of the body die doesn't quite hit the shell holder to allow me to turn down the body die later to bump the shoulder enough for easy chambering. Should I bother?

I want the best accuracy I can get, but most importantly I need a rig that is reliable and trouble free. Waiting for your suggestions.











:)
 
If you are ordering a reamer, a 260 "no turn" would be .294 neck. this gives you 2 thou clearance on a typical 14 thou neck (X2) It also allows you enough room to clean off a thou and still stay tighter than the SAAMI 5 thou clearance. If the rifle is to be a repeater, go .296. If single shot, go .294.

If the chamber is throated for a 142 Sierra, you will have no issues shooting 139 Lapuas, 140 Bergers, or 142 SMK's.

You can throat short, but if going long bullets, I'd go longer throat.

FYI, there is some fabulous Nosler and Norma 260 brass that makes the re-sizing a non-issue. I found that by necking up 243 brass in a gun throated for the 142, the bullet sat deep enough that doughnuts were not a problem. I now use an expander mandrel as my only source of neck tension now anyway.

Good luck with the new 5R! Keep us posted!
 
20" 260rem

Just finish, rem700SA 260rem 20"LTR, very Nice handling.
Everything from this Gun is From Rembo part storage, left over since the last Couples of Year.
Except Scope.
IMG_2876.jpg
 
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I have a couple of 260 Rem, one with standard SAAMI specs and one with a .292 NK and shorth throat. The I think the standard SAAMI neck tapers from .299 to .298.
With just a light clean up on Remington and Nosler brass, mine size down to .288 and with the resulting loaded diameter being .290 - I have resized Fed Gold Medal 308 (which is thick) and it has to be turned a couple of thou to be OK in the SAAMI chamber as it's unturned diameter is about .296. Winchester brass is not as thick so it may not have to be turned, but you will need to check carefully to make sure you have about .002 clearance for bullet release.
I am just in process of deciding on another reamer and plan to go with a match chamber with a .292 NK. I am waiting for Dave Kiff to get back to me with a freebore estimate to seat a 120 SMK at approx 2.85 OAL which should put the bullet bearing surface just above the neck/shoulder junction ---with the bullet taper starting shy of where the bearing surface could contact the potential donut area. This spec will make the throat longer than "normal" but will seat longer bullets so they leave a greater case capacity.
The 260 I have with the .292 NK has a short throat (not sure what it is)...that really reduces case capacity. I had one bad experience where I seated a a 120SMK just short of the lands with a max load of H4350. So much pressure that the primer fell out and could be reseated by hand. The lesson here, seating bullets too deep into the case can be a problem because of the reduced capacity. The other lesson, it really hurts to screw up a piece of Nosler brass!
I think the standard SAAMi freebore is about .118 ? That would seat 140gr -- long, match profile bullets fairly deep. But, remember, if you are shooting game bullets, there is much less taper...
Now, you are probably really confused, I know---I am!
 
Goose25 said:
I have a new barrel that I'll be having chambered in .260rem. I'll mostly be using R-P 260 brass, but also have lots of .308 brass that I might end up trying later down the road. Will I need to neck turn my .308 brass to avoid chambering issues?

More then likely YES. I neck down Win 308 brass for my 6.5 and it works really well. Starts off a bit thinner and with alight neck turn cleans up perfectly.

Make the brass fit the chamber. Take brass you have, turn them to clean them up, seat a bullet, measure your neck diamter, decide how much clearance you need, spec your reamer. If you shoot your rifle, the barrel will be toast before you get bored and sell it. Just make sure to note what neck diameter you decide on if non SAAMI.

I like my neck thickness to be around 12 thou. Seems to work just fine for me.

What should be the chamber dimensions (neck area ) to have a .260rem no-neck chamber(~.2970?)?

A true no turn neck is SAAMI spec BUT you may still need to neck turn IF you use 308 Brass. Something like 308 Lapua will definitely need a turn - maybe even before you neck down.

How much potential accuracy is given up between a tight neck chamber, requiring neck turning and a No-neck turn chamber?

NOTHING. The accuracy is not in the chamber neck diameter. That just determines how much your case necks will expand and can extend brass life. The accuracy part is in the throat dimensions and how well aligned the chamber is with the bore.

Can I have my .260 chambered with a short throat and still shoot 140's without losing much case capacity?

First, determine how long an OAL your mag will allow. This is almost always the limiting factor. If you have a 2.80" mag, then set the throat to be 10 thou longer then the ogive of the bullet you want to use. You will loose case capacity but you can adjust a bit by using a higher density powder. My 6.5's are set to almost 3" OAL and this puts the boattail just at the base of the neck and 100% load density

Should I bother to send 2-3 pieces of brass to my gunsmith so he can use it to measure headspace when chambering my new barrel (use it as a go guage)? I'd use my Redding body die to FL-size my new unfired brass, I'd put a 3 to 5 thou shim under the lock ring so that the base of the body die doesn't quite hit the shell holder to allow me to turn down the body die later to bump the shoulder enough for easy chambering. Should I bother?

YES, absolutely. Dies are the product that we have little control over so why not set the chamber to suit your dies? Otherwise, you end up with a miss match which is truly silly in a custom rifle.

I want the best accuracy I can get, but most importantly I need a rig that is reliable and trouble free. Waiting for your suggestions.

:)
Click to expand...

Quality barrel, quality install, true ammo with accurate bullets over a well tuned load. It'll shoot.

Jerry
 
Goose25 said:
Should I bother to send 2-3 pieces of brass to my gunsmith so he can use it to measure headspace when chambering my new barrel (use it as a go guage)? I'd use my Redding body die to FL-size my new unfired brass, I'd put a 3 to 5 thou shim under the lock ring so that the base of the body die doesn't quite hit the shell holder to allow me to turn down the body die later to bump the shoulder enough for easy chambering.
Click to expand...


mysticplayer said:
YES, absolutely. Dies are the product that we have little control over so why not set the chamber to suit your dies? Otherwise, you end up with a miss match which is truly silly in a custom rifle.
Click to expand...



I'm having a hard time getting my hands on some .260rem brass, everywhere I've looked I've been told that its on backorder. Time is a factor, and I need to get this project completed as soon as possible. I don't have a neck turning device, but do have lots of .308 and .243 brass on hand. Another option, I could also order 7-08 Lapua, and resize that to .260R. Bottow line, I was really hoping to use brass with the appropriate headstamp because I also own and shoot a .243 & .308. Good or bad idea to resize the above mentionned brass without neck turning to send to my gunsmith with my new barrel?

What brass should I use to send to my GS?
 
If you have dies, then size some 243W to push the shoulder back where you want it.

I am not a fan of using 243 brass in a 260 because of the doughnut but it will work just fine as a headspace guage.

Jerry
 
243brass neck up to 260 is a better choice then neck down 308 or 708 since doing that you will have to shave some brass of at the neck.
 
Goose25 said:
I'm having a hard time getting my hands on some .260rem brass, everywhere I've looked I've been told that its on backorder. Time is a factor, and I need to get this project completed as soon as possible. I don't have a neck turning device, but do have lots of .308 and .243 brass on hand. Another option, I could also order 7-08 Lapua, and resize that to .260R. Bottow line, I was really hoping to use brass with the appropriate headstamp because I also own and shoot a .243 & .308. Good or bad idea to resize the above mentionned brass without neck turning to send to my gunsmith with my new barrel?

What brass should I use to send to my GS?
Click to expand...



scratch that... had a member on CGN PM me for some Nosler brass 20minutes after I posted this. Its a done deal now. Man, is CGN G-RRRRRR-EAT!
 
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