Questions About 'long throating' a 260 Rem

[TikkaSporter]

I'm in the process of having a custom 260 Remington built. FWIW, Defiance Deviant action, Manners stock, 24" Bartlien barrel, Timney trigger. It's a BDL magazine setup with a Wyatts extended box. I intend to shoot 140 gr Berger Hybrids and 140 gr Hornady AMax bullets and have about a 1000 of each ready to roll. Lapua brand brass.

My intention was to take advantage of the extra COAL available with the Wyatts extended box and have the barrel chambered/throated to seat the heavy bullets out further and gain a little extra case capacity (velocity?). The gunsmith says to just send him a few dummy rounds with the length I want and he can throat it appropriately.

The questions I have are:

1) Is it even worth it to deviate from a standard/proven throat length to be able to seat the 140 class bullets out further?
2) Would I gain any noticeable velocity by doing this? Any guesses or experience on how much?
3) and the biggie; at what COAL length should I make up the dummy rounds? Which of the two bullets should I make the dummy rounds up with? I would need the throating to work for both bullets, but I don't have a way to compare length-to-lands verses OAL difference between these two bullets (does that even make sense?)... From what I have read, the max available COAL with the BDL Wyatts box would be at least 2.990"... Then I need to leave some room for throat erosion, right?

I would really appreciate some advice or tips from someone that has had some experience with this caliber/bullet combination, and especially with long throating or long seating these particular bullets.

 

[watercam]

If I may, since you are going to feed from a magazine, use a SAAMI throat length to start. It is fairly easy to cut the throat longer down the line if you want to. If you use VLD bullets they will want to be longer than magazine length anyway simply because of the longer nose. For me I have not really been able to gain any significant velocity gains with seating bullets out with the exception of the 6.5/284 Norma which is noticeably different.

 

[hogan]

Go with an Ackley Improved chamber and fagedaboutit...

No kidding... Might also try the Sierra 142smk and fagedabout them Berger and A-maxes... Could even find some in stock these days. Probably be fine seating them flush to the neck or just into the shoulder with your extended box.

The extra flexibility with your powder charge could outweigh using the standard .260 case with the higher BC bullets; IF they are higher bc than 142smk. Velocity is why the 6.5/284 delivers at longrange. The gain you will get from AI'ing your chamber will overcome not using the highest bc bullets, or necessity of seating them a bit deeper than you would prefer to keep mag-length feeding.


One other thought, since mag-length seems to be the issue... Consider a 6.5/XC.... A bit shorter than the .260, but extremely efficient. Can even use necked-up .22-250 brass to make your XC. Lots more barrel life, shooting low 30gr charges than mid 40gr. Maybe even look at the Grendel...

 

[mikegaiz]

the standard use a SAAMI throat length will not shoot bullets lighter than 120 as it is. I would not go any longer. I want to shoot 107 for varmints and do not have enough contact with brass to get a good seal. My buddy also has the same problem.

 

[justme]

I did a single shot 260. 2.980 oal with 139 lapua keeps the bullet barely away from the neck/ shoulder area. Barrel is 28 inches and 2800 and a bit more shoots well and brass lasts a long time.

 

[justme]

seat both of your bullets so the base of the boattail is slightly above the neck/ shoulder, and measure the oal. Then pick one!

 

[rockcreek1]

I have a barrel being chambered with a PT&G reamer designed to shoot the 140 Berger Hybrids and Lapua Brass. I used a long action so OAL would not be a problem. IMHO, I think the 2.990 inches will be very close on length.

Just my 2 cents,
Jim

 

[DHD]

I'm in the process of having a custom 260 Remington built. FWIW, Defiance Deviant action, Manners stock, 24" Bartlien barrel, Timney trigger. It's a BDL magazine setup with a Wyatts extended box. I intend to shoot 140 gr Berger Hybrids and 140 gr Hornady AMax bullets and have about a 1000 of each ready to roll. Lapua brand brass.

My intention was to take advantage of the extra COAL available with the Wyatts extended box and have the barrel chambered/throated to seat the heavy bullets out further and gain a little extra case capacity (velocity?). The gunsmith says to just send him a few dummy rounds with the length I want and he can throat it appropriately.

The questions I have are:

1) Is it even worth it to deviate from a standard/proven throat length to be able to seat the 140 class bullets out further?
2) Would I gain any noticeable velocity by doing this? Any guesses or experience on how much?
3) and the biggie; at what COAL length should I make up the dummy rounds? Which of the two bullets should I make the dummy rounds up with? I would need the throating to work for both bullets, but I don't have a way to compare length-to-lands verses OAL difference between these two bullets (does that even make sense?)... From what I have read, the max available COAL with the BDL Wyatts box would be at least 2.990"... Then I need to leave some room for throat erosion, right?

I would really appreciate some advice or tips from someone that has had some experience with this caliber/bullet combination, and especially with long throating or long seating these particular bullets.

The Deviant Tactical is made with the cutout for AI/AW magazines (DBM only). The Deviant Hunter can use a BDL type B/M (which will allow the use of a Wyatt box). Make sure you get the correct action for your planned build.

I don't have any 260 Rem, but have many other 6.5 calibers. If it was me, I would not use a long throat on a short action I plan to use with a magazine. That throat is going to get "long" on it's own soon enough......

Both of the bullets you plan to use are good one's, but they are very different as far as nose length/bearing surface is concerned. I use both, and my rifles prefer both to be jammed. With the Hybrid's, I don't have much room left and I use AICS magazines with the spacer removed (6.5 Creedmoor). The loaded OAL is way different. Who knows, your new rifle may like to jump them......

You have what sounds like a good build with good components on the way.

 

[TikkaSporter]

It's the Deviant Hunter Integral action and it is already sitting at GA Precision with the Wyatt box and BDL bottom metal waiting for the barrel to arrive ... I went round-and-round on the caliber decision between the 6.5 Creedmore, the 6.5x47 Lapua, the 260 AI, and the straight 260. I choose what I did for a reason, right or wrong, (hint, it's not a match rifle), and I already bought the dies and brass, mostly so I couldn't change my mind.... Again

I know the throat will erode and grow on its own, which is why I want to leave some room for that.... But with 2.990"+ in the Wyatt box shouldn't I have enough room to seat long and still account for it?

The Deviant Tactical is made with the cutout for AI/AW magazines (DBM only). The Deviant Hunter can use a BDL type B/M (which will allow the use of a Wyatt box). Make sure you get the correct action for your planned build.

I don't have any 260 Rem, but have many other 6.5 calibers. If it was me, I would not use a long throat on a short action I plan to use with a magazine. That throat is going to get "long" on it's own soon enough......

Both of the bullets you plan to use are good one's, but they are very different as far as nose length/bearing surface is concerned. I use both, and my rifles prefer both to be jammed. With the Hybrid's, I don't have much room left and I use AICS magazines with the spacer removed (6.5 Creedmoor). The loaded OAL is way different. Who knows, your new rifle may like to jump them......

You have what sounds like a good build with good components on the way.

 

[TikkaSporter]

I can't imagine any scenario where I would want to shoot a bullet lighter than 130 gr in this build. Even wanting to shoot the 130 is unlikely.

the standard use a SAAMI throat length will not shoot bullets lighter than 120 as it is. I would not go any longer. I want to shoot 107 for varmints and do not have enough contact with brass to get a good seal. My buddy also has the same problem.

 

[idahoorion]

Tikka,

you just need to talk to your builder, he has likely built 100's of 260's and 6.5's.

I use AICS in a short action borden. freebore is .060 and I shoot 139 Lapua. with 1300 on this barrel I am out to 2.800 over all length with some room still to grow before I out grow the Aics. .098, and .1 reamers are out there and would likely be better for your use. I would discuss this with Mr. Gardner I can't imagine him not having a handle on it.

Idahoorion