Q how much to open .308 to .45acp muzzle brake?

[3006mv]

I live in CA, due to dumb inexplicable laws I cannot use a flash hider, I couldnt find a .458 socom muzzle brake so i bought a .308 muzzle brake.
the biggest drill bit i had was .470 my boolits are .452 this is for a .45 acp ar15 upper.
not big enough? don't want to take the risk of blowing off the end of my muzzle and threads.

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[country gent]

Im not sure of the dimensions wish you had measured the brake as a 308 and let us know how much over it was for a 308 bullet. Then it would have been easy to figure. Im kind of thinking .470 may be on the large side. Hole could slightly larger if drill cut over any also.

[3006mv]

Im not sure of the dimensions wish you had measured the brake as a 308 and let us know how much over it was for a 308 bullet. Then it would have been easy to figure. Im kind of thinking .470 may be on the large side. Hole could slightly larger if drill cut over any also.

You know I was just thinking about that and yes I should have measured the .308 first before I drilled it open.

[Mk42gunner]

My gut feeling is that .470" is a bit small. Sure in a perfect world it (the bullet) will clear, but I would be more comfortable with a a larger diameter.

For the flash hider on M-14's, .340" runs through my mind; but I think that was for the NM ones, not rack grade.

.340 - .308 = .032"/2 = .016" per side. .452 + .032 = .484"

Maybe call one of the companies that make .458 Socom uppers to see what they recommend.

Robert

[3006mv]

Yeah good point I am sure I can find a .50 drill bit since they seem common, that will clear me for sure, but it may be too big? I don't care about looks.

[Cap'n Morgan]

The closer to size the more efficient the brake will be. If the brake is properly aligned with the bore .470 is fine. The difference between bore and brake should not be larger than .04 (2 x .02 gap) or the effect of the brake will start to diminish. That said, a low pressure round like the 45 ACP with its large boolit to powder ratio will not benefit much from a brake.

[reed1911]

I've always been taught that you need to be groove size * 1.05 so that would be .47355". I would be personally okay with it at .4700" if it were a personal item. I would just approach shooting it carefully and check to make sure you are concentric with the center of the bore and check when shooting to make sure you are not getting any lead wiped on the edges.

[lefty o]

if the bore is perfectly in line with the hole in the brake, you are probably OK, however i'd sure feel more comfortable at .030" over bore size.

[3006mv]

Success! Thanks guys I was able to get to 0.486 I think I am gtg! Yeah I agree a muzzle protector would have sufficed but I am happy with this
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[reed1911]

Now the fun begins, we used a carbine to develop the 300g loads for our RBBT bullet in .45 ACP. I'm not in the office so I don't recall the load off the top of my head but it was VV3N38 Worked great and sure took the hogs with authority.