Gunsmithing 260 reamer question

[RL15]

I would like to shoot 123gr lapuas from a DM system.
If the cartridge OAL is 2.750 with bullet touching the rifling.
What would the freebore of that match reamer be?

 

[RingingSteel]

Re: 260 reamer question

That would be a question for Dave Kiff at PT&G.

 

[The Animal]

Re: 260 reamer question

If you think that you have the bullet seated correctly in the powder column and it fits in your desired mag box, mail the cartridge (without primer and powder) to Pacific Tool and Gauge and let Dave build you a reamer. Most 260's that I've found shoot best with .005 - .015 jump with 139 & 123 Scenars. The optimum neck clearance would be appx .004 specific for the brass you are using. If you are using different brass go with the largest neck clearance required to run everything which is a .298 neck for unturned Lapua brass.

The reamer I use is a PT&G 260 Remington Tactical Match reamer with a .298 neck and .098 fb. This allows the 139 Scenars to get close to the end of the AICS mag box with a .015 jump to the lands.

 

[RL15]

Re: 260 reamer question

I am going to use the AI mags as well.
What is the jump for the 123gr scenars loaded to mag length with that reamer?

 

[The Animal]

Re: 260 reamer question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RL15</div><div class="ubbcode-body">I am going to use the AI mags as well.
What is the jump for the 123gr scenars loaded to mag length with that reamer? </div></div>

I'd stick with .098 fb so you have the option of running the 123's and 139's. The correct fb is longer than the number I mentioned because the bullet is still seated just a little too deep but it's the longest for the utilization of the AICS mags. I'm not sure on the longest or optimum fb for the 123's but Dave at PT&G will know. Give him a call Monday or Tuesday. Preferably Tuesday since he was at the Shot Show and probably needs a day or two to get situated from being away for a week. Just make sure you tell him that you are running an AICS mag box.

Again, if Dave is not sure just mail him a cartridge so that he can take measurements and build you a reamer to your specs.

 

[wnroscoe]

Re: 260 reamer question

I have two main 260 reamers, one for Lapua brass, one for all others. The specs are as follows;

#1 260 Lapua
.297" Nk
.090" Free Bore
1 degree 30 lead
minimum SAAMI from case head to neck shoulder junction

#2. All others
Same as Lapua reamer but .295" Nk

139 Scenars are at a COAL of 2.830ish with a .005" jump. Varying ogive lengths will give diffrent COAL lengths so YMMV.

 

[turbo54]

Re: 260 reamer question

The .098" FB will work great with nearly any bullet.

My recommendation is more, rather than less neck clearance. .298" is good, but .300 or even .302" would be great too, guaranteeing you never have to turn necks, and providing a little more wiggle room for a little piece of debris/trash in the chamber and still allowing chambering.

 

[wnroscoe]

Re: 260 reamer question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body"> My recommendation is more, rather than less neck clearance. <span style="text-decoration: underline">.<span style="color: #FF0000">298" is good, but .300 or even .302" would be great too</span>,</span> guaranteeing you never have to turn necks, and providing a little more wiggle room for a little piece of debris/trash in the chamber and still allowing chambering. </div></div>

Really, SAAMI is .297", why go bigger?

Limit your chamber neck to no more than +.005" over a loaded round and good things will happen, more isnt better in this case, I'm not guessing.

 

[RL15]

Re: 260 reamer question

Thanks to all for this helpfull information.