Suppressors FN PBR Suppressor

M

malefactor

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Minuteman
Feb 7, 2010
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Colorado
#1
I have an FN PBR with the factory muzzle brake. I contacted FN about thread size as I am about to put a suppressor on it. The gentleman at FN said the thread in 5/8" x 20. This tread is evidently unpopular as I can't find a company that make adapters in that size. Usually they are 5/8" x 24.

Anyone else run into this problem? Tips? Solutions?

Thanks
 
#2
Re: FN PBR Suppressor

Most likely you can have a gunsmith make you an adapter to fit the barrel. There is also a chance one of the suppressor manufactures might have the adapter you need. Have you checked with tornado technologies they do not have this adapter listed but they might make them.
 
#4
Re: FN PBR Suppressor

I'm no machinist but I do work in pipe and threads and I don't think you can make a x20 into a x24 at the same size. There wouldn't be enough material to make the threads...

...right?

Besides I might would want to put the muzzle brake back on from time to time.
 
#8
Re: FN PBR Suppressor

To check the thread pitch on your barrel go to a hardware store and get you a 1/4" 20 bolt 1" long now place the 1/4 20 bolt next to the threaded portion of your barrel if the thread pitches match you have 20 threads per inch. To check 24 threads per inch get a 5/16" 24 bolt. this makes a cheep (.20 cent) easy to use thread pitch gage. The adapters are simple to make if you or a friend have access to a lathe. To make the adapter start with 7/8" dia. bar 2" long. First drill 5/16 hole through the center. Next one end needs to be drilled out to 19/32" deep enough to accommodate the barrel threads. This end can now be tapped 5/8" 20 TPI. After threading the ID I like to screw the adapter on a mandrill this will help assure the adapter will be concentric. At this point cut the un-machined end down to .625 dia. to a length of .620" next thread the od. 5/8" 24 ( the lengths of thread can depend on the suppressor manufacture specifications this is from AAC.) I like to use the ends I have cut off barrels to make adapters.
f2sxmf.jpg
 
#9
Re: FN PBR Suppressor

Best to cut old threads off and have it redone. Extending everything out past the muzzle and using a long suppressor as most .30 cal are, is asking for trouble should it rattle loose.
 
#10
Re: FN PBR Suppressor

I agree the best option is to have the correct threads to fit the mount or suppressor, adapters are a second choice. Depending on what suppressor is being used the mount can be re-threaded to 5/8 20. AAC offers the 762 SD Blackout mount in 1/2 28, this mount can be modified for the .30 cal 5/8 20 barrel. I bored out one of these last month for a 7.62mm barrel that was threaded 1/2-28. You can call AAC if you are interested in a AAC suppressor, other manufactures will have similar products
30xbled.jpg
 
#15
Re: FN PBR Suppressor

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Malefactor</div><div class="ubbcode-body">I am worried about making the barrel too short for any kind of long range shooting. At 18" it's at the low end already. </div></div>

Not true. I shoot out to 1000 yards with an 18.5" barreled 308 all the time
 
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