6mm Creedmoor Freebore Questions

[prcomte]

I am about to purchase a PTG or JGS reamer in 6mm Creedmoor. I really like the Creedmoor case design and the now ample brass selection. I know most of the specs that i want the reamer to be, though freebore is where I'm in limbo. I think I want a shorter freebore, so that I can easily chase the lands and remain inside mag length with my 107 MK and possibly run a 110 MK (they are so long). Has anyone ran a .1 freebore or lower on a 6 creedmoor or a cartridge similar? 6 SLR, 6CM, 243AI?

Here are the specs im thinking of:

OAL: 1.915 (I trim to 1.910 every time)
Neck: .274 (This depends on the brass i intend to use. Im still doing some testing. Alpha vs Lapua.)
Freebore: .100 or .090 (I need suggestions)

Thanks in advance!

 

[Seandradamus]

Mine has a .104 Freebore
hybrids at 5 off are 2.77 oal and the boat tail is just at the neck shoulder junction.
Plenty of room in the mag, I also use a bit less powder than most ....... 40.6 of h4350 gets me 3100 out of a 26" krieger

 

[prcomte]

Im currently running a .136 freebore and i feel like its just way to long for chasing the lands. I'm in the same boat with you on F*** PTG, though i think LRI only deals with them, and id really like for them to turn my barrel seeing as they did my action work. When i say mag length I mean Magpul AICS mag length. My gun loves them. With neck clearance, .275 is what i currently have, and it seems almost like to much. I'm getting a ton of brass flow into the neck which i think is attributed to the .275 neck. If you crunch the numbers, lapua brass measures out to roughly 14 thou thick. So .028+.243 is a ~ .271 loaded case (I don't feel like going and measuring one right now.). I Think a .274 neck would be plenty. Even for a .015 neck thickness.

 

[jonaddis84]

You will need a 298 neck for necking down Alpha brass without turning. If you want to turn, Id go 275 neck and turn to 2715ish loaded.

Freebore. 143 freebore puts the 110mk at 2.900 at the lands, and only around 0.190" of bearing surface in the neck.

Also, go JGS. Not sure if you are chambering yourself or not, but I have the 275 neck reamer setup for 110mk already, and have the 298 neck version for running Alpha no turn on the way.

 

[B-P-UU]

.277" nk and .109 FB working well with 105 VLD's and Hornady brass. Can't speak to the other brass manufacturer's.

 

[prcomte]

I'm leaning to the .100 - .105 freebore. I don't want to change mags. The gun feeds good with them and they are half the price of AICS mags. I'm waiting on my alpha brass to get in so I can take some measurements. Does anyone know the neck thickness of the necked down alpha brass by any chance?


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[prcomte]

.018 is thickkkkkkkkk. I thought it'd be closer to .015.


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[prcomte]

Im going to try 100 pieces. Thy should be on their way to me. Alpha didn't give me a tracking number. I hope the case capacity is about the same as the new lapua brass.


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[prcomte]

I also like lapua quite a bit, though I've seen great reviews about the alpha and it's made in the USA. Do you know the water weight of your 6.5 Creedmoor alpha brass?


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[prcomte]

I'm running h1000 in my 6 Creedmoor and the only limiting factor for me is case capacity. I'm really looking forward to getting the brass in and running it. It sounds awesome. My es is in the low teens with lapua brass. Even if it the water weight is less. That's nothing a long drop tube can't fix.


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[Supersubes]

The .183 freebore of the saami 6cm does seem long. Especially when compared to other 6mm, like the xc or 6x47. You have to consider though that of those three, the CM has the shortest neck, by about .025 iirc. So using the neck shoulder junction as a reference point for a seated bullet, the cm reamer prints will always reflect more freebore(when comparing cartridges)

As an example, the 115 DTAC 6xc chamber that was all the rage has .148 fb. Now if I trim the neck length back on the XC .025" (6CM length neck), my effective freebore is now at .173, making the saami 6mm cm freebore seem pretty much right where it needs to be with the same bullet.

If you're not planning to shoot the 115 dtac, then ya, id shorten the fb quite a bit. My manson 6cm reamer has .160 fb, and .004 clearance at the neck, shoulder, and webb on a lapua case. I havent chambered anything with it yet, so nothing to report there.

Edited: .1 or .090 is gonna be too short for the .107 I think. I dont have any left, but I do have samples of the 110smk. I can take some comparative measurements between the 110 and dtac to see how much shorter the 110 fb would need to be.

 

[prcomte]

My gun shoots 107 MK better than it does the 105s. The lack of good brass is what made me hold off on a Creedmoor for so long.


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[prcomte]

I'm really enjoying the creed so far. I want to see how long this barrel lasts with h1000. That'll be the deciding factor.


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[ZiaHunter]

I am running a .185 freebore with a .275 neck in my 6mm CM mid range F Class rifle with chamber cut with JGS reamer. Went with the longer freebore to keep the bearing surface above the neck shoulder junction as well providing additional case capacity to run slower powders. Running Berger 105 HB with Lapua brass turned to .0135. 43.5 gr. of R-26 providing 3070 fps out of a 32" Bartein 1:7.5 5R. Load is extremely accurate with SD's less than 3 fps. COAL is 2.805.

 

[JGorski]

LRI has all the reamers I ordered for my 3 builds, 104, 136 and 173 freebores, the 2 latter reamers have the 275NK, 104 has a 274nk, of the 3 Chad has I'd go with the 136fb for the 110, won't be long before you get enough throat wear that the 110MK will fit perfect, I have the 136FB on my current 600BR rifle and am shooting 105JLKS very nicely into small groups, though for that bullet the 104fb would fit more appropriately, and after about 1000 rounds thru that 104fb rifle it now has the same throat as my 3rd build which started out with the 136fb.