Thread: Supressors.

Originally Posted by Homer

Got a Bee in your Bonnet today Spanners?

Doh!
Homer

No - just tring to get my head around a blanket statement telling me that after the blank is profiled/fluted etc, its THEN lapped.
It makes no sense, given the fact you pay a premium from the mfg for a lapped barrel
Lilja, Truflight, Krieger, Shilen - the most winningest barrel makers in the world supply the blanks prelapped

Originally Posted by Homer

Spanners, you answered your own statement or question there!

I've brought a few custom lapped barrels (Shilen, Truflight)- always supplied as a blank - barrel is lapped before its even sent out to Smith for chambering, profiling, fluting etc

Well I suppose I should have said, custom barrel makers, do all the machining (profiling, fluting etc) then lap the barrel to leave the muzzle a bit tight, prior to then fitting the barrel to the customers action.


Double Doh!!
Homer[/QUOTE]

So what you are saying is that barrels fluted etc after lapping won't be as accurate as ones done before ???

My, my, there seems to be a bit of confusion here. The issue behind this debate, well the threading/fluting bit of it anyway, is residual stress in barrels. When you remove metal from a steel tube with residual stress it will most likely change its internal bore dimension – that is fact. Some types of rifling, those that displace steel such as button and hammer forging, induce stress into the barrel. If you don’t believe this, then why do you think all the top barrel makers go on about double stress relieving, cryogenics etc. Even Krieger, Bartlein etc who cut rifle their barrels and therefore should not be inducing stress have significant stress relieving procedures. If using a top quality, truly stress free barrel, then removing metal in a non-stress inducing way such as profiling or threading, you should not have any problems.

Fluting is quite different, as the arbor cutters usually used in fluting operations do induce stress to some extent into barrels. This is why some top quality barrel makers do not recommend fluting their barrels at all. Most will not honour any sort of warranty if you aftermarket flute their barrels. There are many, many stories of previously accurate barrels being ruined by fluting. You tell John Krieger or Frank at Bartleins for example that you are going to flute one of their match barrels and see what response you get! If any of you guys had actually measured the bore diameter of a range of fluted barrels, then you would see what I mean. Most fluted sporter contour barrels have opened up in bore diameter under the fluted section. They are tightest under the parallel, and under the last unfluted section before the muzzle. This is their saving grace in some ways, as it gives them some choke for a couple of inches before the bullet exits. If you don’t need to save weight in a barrel, then stay well away from fluting, it can really open a can of worms unless done properly.

Now the lapping debate, most top accuracy barrel makers and benchrest shooters lap their barrels as the last operation before fitting. That is after contouring and any other major metal removal. They also do try and lap the barrel so the tightest spot is the muzzle. This is even though contouring done properly to a truly stress relieved barrel should not cause any issues. Again, note the truly stress relieved part of that sentence. Yes, you can buy prelapped barrel blanks that you can contour later, but the top barrel makers suggest you let them contour your barrel and they will lap the barrel as the last operation. Again, why risk contouring later when the standard procedure is to order your barrel pre contoured and finish lapped???

And then we come to factory barrels…all of the modern mass produced rifle barrels have stress induced to some extent during the manufacturing process. Can you guarantee that all factory rifles will have been consistently and totally stress relieved??? With the variability and somewhat lacking quality control we see these days out of mass produced factories, I don’t need to tell you the answer to that one! Removing metal from factory barrels is a real lottery, and can get you into bore opening accuracy issues. Hammer forged barrels can go either way, in fact Dean Maisey reckons they’re as likely to tighten up as open up when you remove metal. We’ve seen them go both ways, but button rifled barrels in particular seem to be some of the worst for opening up when you remove metal from the outside. The simple common sense rule is remove as little metal as possible, especially about the muzzle! Again, we actually measure the bores and this is what we have seen, backed up by the accuracy results on the range. We have had plenty of rifles come thru here that have been threaded for cans/brakes that won’t shoot. We have seen bores that have opened up by over 1 thou under the thread, and I can tell you they do not shoot! Half a thou is more than enough to affect accuracy. Once we cut the opened up section off, they will shoot accurately again.

And so then we come to the compromise that KG is talking about, requiring something to pull a brake or can up on and the issue of creep. Convention has been to use a shoulder behind the thread to pull up on, and if doing this we keep this shoulder to the absolute minimum for all the metal removal reasons above. If you’re fitting a radial brake that will be taken on and off, then you can certainly run a small shoulder as it doesn’t matter if they creep a little over time. It will not affect accuracy or point of impact at all. If using a directional brake that must be indexed correctly for looks, then you need to decide whether you are going to be taking it on and off all the time. If you aren’t, then you can still run a small shoulder in the conventional place without issues. If you are wanting to remove it continuously, then pull the brake up on the muzzle, which gives you a huge surface area which won’t creep - without any bore opening up issues from running a large shoulder in the conventional place. The only brake you cannot pull up on the muzzle is a radial type B Vais type brake with axial (lengthways) holes, as they would obviously be blocked off.

Cans are a slightly different issue, as you’re talking about a lot of weight hanging on the end of your barrel. Shifting the Can backwards and forwards will change harmonics with a potential POI shift, in the same way as a barrel tuner does. We have run comparatively small conventional shoulders with no creep or POI issues by simply not over tightening the Can. If you are heavy handed when installing your Can, and plan on taking it on and off a lot, then you will want more surface area to pull it up on. You will then have to run a larger shoulder meaning more metal removal if in the conventional behind the thread position, but I would not do this on any barrel that had suspect residual stress issues. Or again, you can pull it up on the muzzle if you design your Can internals this way, which is probably the best system. Hopefully we will see Can manufacturers all go this way in the future, some already have, which will give you the best of both worlds. You can then have your muzzle thread diameter at the maximum your barrel cleans up at to eliminate any stress bore opening issues, and still have a no creep installation.

Another thing to keep in mind is thread pitch affects how much metal is removed. Standard, fairly coarse pitch threads, especially the likes of the 20tpi of the ½” UNF, are deeper and therefore remove more metal than fine pitch threads. It’s no accident that Vais use 32 tpi and Holland 28 tpi on all their brakes for this reason.
Removing metal off the outside of rifle barrels is a lottery, but with some the odds are better than others - you pays your money and you takes your chances!

And KG, brake/suppressor clearance depends on just how true with the last section of the bore and well fitted thread size wise it is installed in the first place, and in the case of Cans, how true their internals are. Some are far better than others in this regard. Cans that extend well forward of the muzzle are even more of an issue here. A true thread is only as good as the bore of the brake/Can. As we bore our brake bores on the barrel, we can run small clearances quite safely. The less the clearance, the more effective the brake or Can will be. We run 20 thou on brakes and Cans with machined true internals, and 50 thou on Cans with assembled internals. If you have a sloppy thread and continue to shoot with your brake or especially Can partially unscrewed, you are asking for trouble!
Greg

Hey Greg, I read your article on Suppressors with interest. I'm currently running two Hardy suppressors and two Gun Works suppressors. Correct me if I'm wrong but both my HRE suppressors/barrels have 20 TPI 1/2 inch threads? Has Dan taken on board your advice and changed his standard thread?
Also on page 66 of the latest mag you quote some prices to build a bush pig, am I right that a 7mm-08 or .308 remmington barrel fitted costs $200? If so can you do .243 for the same price? (Blued or SS?)
Last question, do you need the whole rifle to do a half cock on a T3 .223?

Craig,
Yes, Dan has standardized on 14x1 mm now, which is about .55 inch by 25 tpi if you think in imperial, and a much better size to run as a standard on sporter contour muzzles. We run even bigger, 15x1 and 16x1mm on the ones we shorten to 16 inches, as they are larger in diameter there than at a 22 inch length obviously. Both Robbie and Dan will make pretty much any thread size cans you want if you order them as customs.
You need to email me about any what could be classed as commercial questions, otherwise this thread may be removed.
editor@nzhunter.co.nz
Greg

G'Day Fella',

Greg D, thank you for an informatively written post on these subjects!

I was warned by one of the NZ suppressor makers to not participate on any hunting/shooting forums!
He told me that it would not be a smart move!!!
I thanked him for his kind advice but suggested that if someone with a just a little bit of personal knowledge and experience didn't participate on forums, then things other than the truth, would prevail!

Doh!
Homer

Originally Posted by Homer

G'Day Fella',

Greg D, thank you for an informatively written post on these subjects!

I was warned by one of the NZ suppressor makers to not participate on any hunting/shooting forums!
He told me that it would not be a smart move!!!
I thanked him for his kind advice but suggested that if someone with a just a little bit of personal knowledge and experience didn't participate on forums, then things other than the truth, would prevail!

Doh!
Homer

Homer, "Opinions" & "Truth" aren't necessarily the same thing...........

Kiwi Greg,

What about personal "Knowledge" and "Experience", does that count?

Doh!
Homer

So basically, as a 'gunsmith', best results are gained from buying a pre profiled and lapped barrel from the mfg and screwing it on - I'm sorry, but that doesnt make you a guns smiths arsehole, it makes you a gun mechanic, just like a Toyota service technician isnt a race engine builder. Any monkey can fit a pre machined barrel.

However, in the real world, you ring up Mitch Maxbury (an ACTUAL gunsmith - with walls of trophys and medals to prove what he does works), Dead Eye Dicks, Truflight or anyone else that stocks blanks, and buy a premium barrel blank that has been lapped and air gauged at the factory and then deliver said barrel to your prefered 'gunsmith' for machining and fitting - I'm yet to find any pre profiled barrels on the shelf other a cancelled custom order.

Homer - Perhaps said suppressor maker should have taught you some tricks of the trade on suppressor building at the same time

Originally Posted by Homer

Kiwi Greg,

What about personal "Knowledge" and "Experience", does that count?

Doh!
Homer

Everyone has Knowledge & Experience it depends how they apply them & whether they are their own or some one elses that they have "borrowed"......

The Knowledge & Experience I have been shown in these last few posts is that if you thread the end of a barrel or flute it after it has been lapped as is normal practice for most gunsmiths that I know of, you are detrimentally effecting it's accuracy.....

Which I'm afaird is severly flawed, these gunsmiths would have been out of business years ago.....

can we keep it chill. cheers.

Well said Gimp. Spanners, you in particular as a moderator I would have thought, should be setting an example on the tone of this forum?

Spanners, have you dealt or communicated with any of the top USA barrel makers? You seem to have quite the wrong end of the stick. We have communicated with, purchased barrels off, and fitted Kriegers, Bartleins, Liljas, Broughtons and Pacnors. Mitch certainly is a great gunsmith, no doubt, and he will be sorely missed when he heads back to the USA to live shortly. Out of interest, have you asked his opinion on fluting???? You might be surprised at his answer! We have some straight blanks in stock, and have contoured and fluted some when required. Ian even cut an integral angled port muzzle brake into a 1.8” straight Lilja 7mm blank we had here. But we far prefer as do the premier benchrest gunsmiths and benchrest shooters in the world that the barrel manufacturer does the contouring and or fluting. They are set up to do this the most accurate way possible at the best time in the barrel manufacturing process, and it gives us a quicker turn around time. And any monkey can accurately set up, thread, chamber and crown a barrel? Really? Oh well, we must just be monkeys then!


KiwiGreg, please do not misrepresent what I said. You are trying to make black and white what is not. I never said threading or fluting will always detrimentally affect accuracy. I went to great length to explain the issues and the large variables at play here, which are real whether you accept them or not. By all means believe what you will, but we will be trying to do the best for our own rifles and those of our customers. This means using common sense and the commonly accepted best practise by the most recognised accuracy barrel makers and gunsmiths in the world. And that may well mean at times publishing the "inconvenient truth" which may well annoy some internet experts and NZ professionals set in their ways. So be it.
Greg

I asked Mitch to flute a barrel for me and he said no; it will ruin the accuracy!

Here's a nice (fluted) set up. Remington 7mm WSM | Trade Me

Why don't people understand fluting does nothing apart from looks. Weight loss is irrelevant as your only talking grains. Strength loss is a much bigger cost.

If you really want to loss weight from the rifle then work out what the diameter of the barrel after fluting then machine the whole barrel to that dimension. And by the way, the barrel will cool much quicker doing that than fluting, yes it will heat faster too.

IF fluting was worthwhile then you would see it in a lot of other places. You don't.

So to those who are of the opinion that thread diameter doesn't matter what do I tell the guy whose gun now shoots worse than before it had a 1/2" thread cut into it? He's the same guy with the bulging suppressor. Did I mention the rifles twin took the GD approach with a 14 x 1 thread and shoots the same/better as before?

When he sends back his suppressor the rifle will be going also and he'll be rightly asking for a new thread to be cut because the 1/2" one definitely affected his accuracy.