.575" x 40 Versus .578" x 28

[Historian]

Packing away my really old Brownells' catalogues to make room for new
tomes I saw a sticky I had placed on the page for tap and die
pairs for .45 barrels. The two subject sets popped into view.

Some searching then found that barrels for .45 1911A1 are made in both
TPIs. I have always thought that suppressors use the 28 TPI.

Does the 40 TPI fit some esoteric cans?

Appreciate any input to fill in this information gap in my notebook.
Always finding new data.

Thanks.

[ksbowhunter]

If memory serves me correctly the .575x40 is for a muzzle brake.

[Historian]

[quote="ksbowhunter"]If memory serves me correctly the .575x40 is for a muzzle brake.[/quote]

Thank you for this info which led me to follow up which led me to an interesting
and technically informative YouTube of a smith fitting a muzzle brake.
In this case he was cutting a 28TPI thread for his muzzle brake like that for a suppressor.

If I find a reason for the 40TPI thread I shall pass it on.
From first pass I have not found a reasonable one.

Thanks again.

Note: The large lathe he uses will make your heart beat faster.

[Historian]

The YouTube mentioned above:

<< http://www.youtube.com/watch?v=JV6jTZzsNBw >>

[gunny50]

If memory serves me correctly the .575x40 is for a muzzle brake.[/quote]

If I find a reason for the 40TPI thread I shall pass it on.
From first pass I have not found a reasonable one.

Historian,

40 TPI is most common for compensators, here in EU I use 0,75 and 0,50 mm pitch for that (in pistols)
Has to do that a lot of the pistol barrel walls are not that thick, and pistol barrel compensators do not always use a shoulder that they index on.
The comp is machined in contour of the slide, barrel threaded and than timed.
Also gives the option for some pistol barrels to make a cone on the comp for smoother lockup and better lockup, better accuracy downrange. Bull barrel contour on light weight 1911 barrel, the bull barrels are not that often with extended threads. This is also a great way to upgrade your old 1911 with just the cone and make it more accurate.
No need to buy extended barrels, just take barrel bushing out or open up the slide, all depending what pistol it is.

Gunny

[Historian]

If memory serves me correctly the .575x40 is for a muzzle brake.[/quote]

If I find a reason for the 40TPI thread I shall pass it on.
From first pass I have not found a reasonable one.

Historian,

40 TPI is most common for compensators, here in EU I use 0,75 and 0,50 mm pitch for that (in pistols)
Has to do that a lot of the pistol barrel walls are not that thick, and pistol barrel compensators do not always use a shoulder that they index on.
The comp is machined in contour of the slide, barrel threaded and than timed.
Also gives the option for some pistol barrels to make a cone on the comp for smoother lockup and better lockup, better accuracy downrange. Bull barrel contour on light weight 1911 barrel, the bull barrels are not that often with extended threads. This is also a great way to upgrade your old 1911 with just the cone and make it more accurate.
No need to buy extended barrels, just take barrel bushing out or open up the slide, all depending what pistol it is.

Gunny

Most appreciative for clarifying things. Thanks to you the light bulb lit up.
Of course: thin walls finer thread.

As with say the PPK threads.

I was fortunate in the 1960's to have purchased one of the last US Government Springfield
Armory National Match on a GI .45 1911A1 frame before they were closed down. ( ~$125.00 (?) )

e.g.. << http://media.liveauctiongroup.net/i/122 ... 74F850D7C0 >>

To get comparable accuracy friends had to send their commercial Colt National Matches
to Bob Chow for his tune up, at many times the price I paid for mine alone.

To this day it still is as accurate as the day I got it. My other .45's just come up to it.
In 1970 I got a Bar-Sto SS extra long barrel for one of the 1911A1's and in the hands of a top shooter
who tested both he got all X's.

Motto: Buy the best up front, it is 'cheapest' in the long run.

Best.