help determining what to have freebore cut to

[Forest]

I'm building a 7 saum on tikka action. Carbon six just got my barrel done so its time to start giving my smith some specs of what I want. Doing it on a long action so I have no real restrictions in mag length. I know i can get a lot more out of it if i have it cut longer than saami, so no reason not to. I am just struggling to decide what he should cut it to.

As of now I plan on starting with the 155HH, just looks to me to be a good balance of speed, weight & bc. I can likely order a dummy round from a custom ammo manufacturer, but would need to know what ideal seating depth would be. (I've never loaded hammers myself.) Or I could easily have them send me a dummy round with something like a 175gr ablr. The 155HH has a similar length to the 168-175gr bullets so seems like if I have freebore cut for one of these it should give me lots of options down the road??

So for those of you who have custom throats how did you decide on what to have done?? If later on I decide to go with something like a 143 will I be able to???

I'm sure i'm overthinking this, my first real build and just want to get the most out of it.

Thanks for the help!

 

[HighUintas]

I would just get ayour bullets and brass and make a dummy if you know what bullet you're going to be shooting. If you want the most speed with the bullet you're choosing (155hh), then seat it to where it's as far out as possible but still has 1xbullet diameter in the neck (actual bearing surface/neck contact, not including length of boattail). Ask HH if those bullets do best seated close to or far from lands.

If you're wanting to use a shorter bullet also, research that bullet's jump preference. Get some of those bullets and see if you can accommodate the it's jump preference with decent seating depth while still having your HH bullet work.

 

[Keith Stone]

-Order what bullets you want to shoot
-Seat 3-4 at the boat tail/neck shoulder junction
-Tell your gunsmith you want them jumping 15thou or whatever the manufacturer recommends.

Sounds like your a bit scattered on your bullet options so a bit more research(in the heavier variety) on what your after may be in order before you pull the plug. Not that other bullets won’t work but if your going through the effort of custom throating make sure it’s really what you want.

 

[mxgsfmdpx]

What barrel did you order from carbon six? Looking for a barrel for my Tikka 7 SAUM build right now as well.

 

[Forest]

What barrel did you order from carbon six? Looking for a barrel for my Tikka 7 SAUM build right now as well.

20" sendero contour, 1-8" twist. Came much quicker than they initially said it may take. So gotta love that!! This is my first carbon six, have a couple friends that have had great success with them. And my Smith also highly recommended one

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[Forest]

-Order what bullets you want to shoot
-Seat 3-4 at the boat tail/neck shoulder junctionView attachment 347632
-Tell your gunsmith you want them jumping 15thou or whatever the manufacturer recommends.

Sounds like your a bit scattered on your bullet options so a bit more research(in the heavier variety) on what your after may be in order before you pull the plug. Not that other bullets won’t work but if your going through the effort of custom throating make sure it’s really what you want.

I know where I want to start, and while I have a lot of confidence in the hammers I'm new to them and just want to keep my options open down the road.
Killed more critters with standard accubonds than anything, just wish they made a heavier standard ab. Not a fan of bergers, been using eld-x the past few years with mixed results. Which leaves me at the ablr, however I haven't used it on game yet.

And the end of the day I just don't want to be married to one bullet for the life of the gun, but I definitely don't want to use the lightweight lead bullets that the cartridge was designed around years ago either

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[sndmn11]

I don't have an answer, but this concept was brought up to me by a barrel maker on the one single barrel I have ordered.

Going with the shortest freebore that you think you might find acceptable will let you chase the lands as the throat moves and therefore give you more barrel life. No clue if that is correct, or a weird opinion, or anything other than what one barrel guy told me.

 

[Mike D Texas]

Have it throated for the bullet you have the most confidence in. Hammers are *mostly* insensitive or less sensitive to seating depth variations than traditional cup/core bullets.

The image above is the ideal way to maximize case capacity for any given round. Unless you are going to be hammering lots of rounds down the barrel don’t worry about throat erosion. In my experience chasing that lands is way overrated especially for a hinting rifle.

2 of my most accurate rifles have a ridiculous amount of freebore and one it a 1/4 MOA (257 Wby that has .375 freebore) and the other is a factory Remington 700 5R mil spec and with a SAAMI length cartridge it has about .200 freebore.


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[ApeComic]

I built a 7saum in a long action so I could get all the length I wanted. My Smith used a Sammi reamer with a throater to lengthen out the freebore. I had my chamber setup to run 190 a tips which I get 3050fps. All that being said go with the freebore that gives you the most options. In your case I dont think its super important to have it maxed out length wise unless you're wanting absolute top performance with a long bullet.

 

[762 ULTRAMAGA]

I know where I want to start, and while I have a lot of confidence in the hammers I'm new to them and just want to keep my options open down the road.
Killed more critters with standard accubonds than anything, just wish they made a heavier standard ab. Not a fan of bergers, been using eld-x the past few years with mixed results. Which leaves me at the ablr, however I haven't used it on game yet.

And the end of the day I just don't want to be married to one bullet for the life of the gun, but I definitely don't want to use the lightweight lead bullets that the cartridge was designed around years ago either

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I've used the 175 ablr and they don't kill nearly as well as a 180 berger, personally I'd avoid them all together.
I'd have your smith go with .225 freebore, that'll give you the option to run 160- 180 vld's

 

[Forest]

I've used the 175 ablr and they don't kill nearly as well as a 180 berger, personally I'd avoid them all together.
I'd have your smith go with .225 freebore, that'll give you the option to run 160- 180 vld's

That does seem to be in the middle of the numbers that I am commonly finding, so that is kind of what I am leaning towards, thanks.

The problem i have with bergers is i've witnessed just as many failures as i have successful shots. (Fairly limited experience tho to be honest.) Ive seen them pencil through deer and ive seen them essentially blow up on elk shoulders. I also know they make a lot of different jacket types and i cant speak to the ones ive watched.

 

[762 ULTRAMAGA]

That does seem to be in the middle of the numbers that I am commonly finding, so that is kind of what I am leaning towards, thanks.

The problem i have with bergers is i've witnessed just as many failures as i have successful shots. (Fairly limited experience tho to be honest.) Ive seen them pencil through deer and ive seen them essentially blow up on elk shoulders. I also know they make a lot of different jacket types and i cant speak to the ones ive watched.

I hear you
I've seen penciling issues from the 215’s, they definitely need the tips cleaned out.
The 175 eldx would be a good choice as well

 

[Ucsdryder]

that’s a hard one. I knew what I wanted to shoot. 180 eldm, which is also one of the longest bullets out there. I sent the smith a dummy round.

 

[Ice-kub]

OP what did you end up doing? I built a 7 wsm on a rem 700 long action for the same reason. Put a couple dummys together and gave them to the gunsmith. Told him I wanted 0.015 off the lands and that's how he built it.

 

[Forest]

OP what did you end up doing? I built a 7 wsm on a rem 700 long action for the same reason. Put a couple dummys together and gave them to the gunsmith. Told him I wanted 0.015 off the lands and that's how he built it.

I've got a dummy round sitting here with the 155 hammer and will have my smith extend the throat to that. Won't get it all fully together till later this winter/spring. Dummy round is 3.045" if I remember correctly, so not a huge gain over saami but decent. I think it will give me some flexibility up/down in size down the road if I decide to switch bullets and definitely worth the small cost of having him extend it.

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