300 blk coaxial build almost done -- Range Report.

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policetruck
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300 blk coaxial build almost done -- Range Report.

Post by policetruck » Thu Oct 06, 2016 10:39 pm

Sorry this is pretty much just a teaser for now. Just pictures of the outside.

I was going to build an omega based can, but have decided to change my spacers and vents to the coaxial space and add 2 baffles. I'll finish it in the next week (I hope) and get some pctures of the finished stack.

Image

Image
Last edited by policetruck on Thu Oct 13, 2016 7:10 pm, edited 1 time in total.

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Re: 300 blk coaxial build almost done

Post by policetruck » Fri Oct 07, 2016 12:36 am

Ok some more of what is already done...

Blast baffle and blast baffle spacer. Spacer is .080" at the small diameter and .050" at the large. Baffle is supposed to be .080 but I think it's closer to .095". I don't have the right tools to measure The cone but taking other measurements and calculating it says it's thicker than should be. Both made from 17-4ph h1100. The tube and rear endcap are also 17-4ph h1100. The front endcap is 7075 Al.

Image

Here are two out the four baffles that I have made so far. Four are the same and the two I have left are minus the coaxial divider plate. These are 316 ss and are .055".

Image

My spacers are roughed out but not ported, I'll get pictures of them after I cut the ports.

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Re: 300 blk coaxial build almost done

Post by Hatchetjoe » Fri Oct 07, 2016 5:49 am

This looks pretty heavy duty, I'm guessing a short bbl and lots of full auto?

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Re: 300 blk coaxial build almost done

Post by policetruck » Fri Oct 07, 2016 7:25 am

Short barrel, yes. Full auto or mag dumps? I don't have that much money. Partly why I'm building my own can. I'm also really enjoying the design and work involved in making something nice.

About it being heavy duty, I'm trying to shave all the weight I can. Actually trimming the blast baffle is on my list of things to do, but yeah it's an all steel can so it'll be a miracle if it's under 20oz when I'm done. Unfortunately there's a lot of weight in the rear end cap but it's welded together so I can real only trim stuff on the outside.

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Re: 300 blk coaxial build almost done

Post by Rich V » Fri Oct 07, 2016 10:10 am

Nice job machining your can. With 17-4 SS you can go much thinner than what is typical of 300 series SS as 17-4 has 3-4x the strength. I would trim the thickness on the baffles & tube to 0.050in to give you a lighter overall weight. Most rifle cans use 300 series SS for the tube and they typically run @ 0.065 in wall. With 17-4 you can half that thickness and still be stronger that the thicker 300 SS tube.

Did you buy the 17-4 tube or core out a bar?

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Re: 300 blk coaxial build almost done

Post by policetruck » Fri Oct 07, 2016 3:39 pm

I bored it from bar stock. I was very fortunate to have about a foot of leftovers from another job.
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Re: 300 blk coaxial build almost done

Post by propeine » Fri Oct 07, 2016 3:57 pm

policetruck wrote:Ok some more of what is already done...

Blast baffle and blast baffle spacer. Spacer is .080" at the small diameter and .050" at the large. Baffle is supposed to be .080 but I think it's closer to .095". I don't have the right tools to measure The cone but taking other measurements and calculating it says it's thicker than should be. Both made from 17-4ph h1100. The tube and rear endcap are also 17-4ph h1100. The front endcap is 7075 Al.

Image

Here are two out the four baffles that I have made so far. Four are the same and the two I have left are minus the coaxial divider plate. These are 316 ss and are .055".

Image

My spacers are roughed out but not ported, I'll get pictures of them after I cut the ports.

Use a ball bearing and a micrometer to measure wall thickness on the cone. Specifically I use a bucky ball since they're magnetic but any bearing should work. Measure the bearing, put it on the inside of the cone, measure the bearing + wall, subtract the bearing.

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Re: 300 blk coaxial build almost done

Post by policetruck » Fri Oct 07, 2016 5:01 pm

Yeah I was actually being lazy. I know we have some mics around with a ball end instead of two flats. I just have to find it. One of those things that gets buried cause we don't use it very often.

Also most of the bearings we have around are questionable on roundness since they are used/bad machine parts.

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Re: 300 blk coaxial build almost done

Post by policetruck » Sat Oct 08, 2016 2:29 pm

I know people like pictures of machine setups and stuff so here are some pictures of parts of the machining process. I'm not the best at remembering to take pictures while I'm building things.

Machining end cap outter face in our CNC mill
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Setup for machining 60 deg cone ID
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All done
Image

Setup for cone OD
Image
I started turning the OD with carbide tools but they were too big and I would have too much waste in removing steel for to clearance. Then decided to use a smaller piece of HSS and saved an inch of material from being wasted per baffle.

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Re: 300 blk coaxial build almost done

Post by policetruck » Mon Oct 10, 2016 5:56 am

Can complete! Now to shoot and see how it sounds.

I'm not sure if my steps in the cones are deep enough. I was reading the post where curtistactical was talking about his tests with different cuts in the cone entrance. His conclusion was that the half diameter step/clip cut, .125" deep yielded the best results. Mine are .100" deep. I did this to avoid opening up the bore of the cone at all. But the more I think of it that extra little bit of depth may help the cross jet to shoot across to the inside of that baffle and into the next chamber. Does that sound right or is keeping the bore diameter tight & symmetrical more important.

I was also thinking of drilling a small hole in the coaxial dividers to help equalize the coaxial spaces. But I'm going to wait on this. I was thinking that one small hole in each of those might help the pressure in the coax chambers to stay a little lower and aid in filling these spaces.

Anyway here's a picture of the finished stack. Now I wish I had another stamp to work on. A pistol can next time I think...

Image

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Re: 300 blk coaxial build almost done

Post by policetruck » Mon Oct 10, 2016 6:00 am

Also here is a picture of my muzzle brake from a long time ago it seems.

Image

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Re: 300 blk coaxial build almost done

Post by T-Rex » Mon Oct 10, 2016 8:08 am

policetruck wrote:Can complete! Now to shoot and see how it sounds.
I'm waiting, I'm waiting. :D
policetruck wrote:I was also thinking of drilling a small hole in the coaxial dividers to help equalize the coaxial spaces. But I'm going to wait on this. I was thinking that one small hole in each of those might help the pressure in the coax chambers to stay a little lower and aid in filling these spaces.
I looked at your stack, before reading your post, and wondered the same thing.

Very nice, I hope it performs well.
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Re: 300 blk coaxial build almost done

Post by fishman » Mon Oct 10, 2016 1:01 pm

the .125" deep step cut recommended by curtistactical may not be exactly what you're looking for, you have more of an omega baffle than a regular cone baffle. you might benefit from an even deeper cut, maybe not.

nice work, very well done. i cant wait to hear about how it shoots
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Re: 300 blk coaxial build almost done

Post by policetruck » Mon Oct 10, 2016 6:56 pm

fishman wrote:nice work, very well done. i cant wait to hear about how it shoots
Thank you and me either. I've been working nights so... I think I'm going to put a couple rounds through it tomorrow morning. I have some Remington 220 gr subs just waiting around for this occasion.

Also for build documentation the can weighs right at 22 oz. Definitely heavier than I was shooting for but manageable. It's on an SBR anyway so the rifle is fairly light and only adds about 5" past the barrel muzzle.

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Re: 300 blk coaxial build almost done

Post by whiterussian1974 » Tue Oct 11, 2016 12:39 am

Sweet! Can you post more Pics of the Ported Spacers? They seem to perform a coaxial venting function similar to Omegas.

Great Build! I'm too jealous. :cry:

It looks overbuilt for a 300BLK. It would probably perform great on a .300WSM. :idea:
I'm going to incorporate some of these elements in my next Magnum build. 8) :mrgreen:
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Re: 300 blk coaxial build almost done

Post by policetruck » Tue Oct 11, 2016 3:56 am

whiterussian1974 wrote:Sweet! Can you post more Pics of the Ported Spacers? They seem to perform a coaxial venting function similar to Omegas.

It looks overbuilt for a 300BLK. It would probably perform great on a .300WSM. :idea:
I'm going to incorporate some of these elements in my next Magnum build. 8) :mrgreen:
I'll post some pictures of the ported spacers. They are kind of like an omega but no port on the other side and I think I may also make them bleed into the next coaxial space. I'm sure it is overbuilt for a 300 blk, I'm probably going to make a brake for my H&K G3 clone and use it on that too.

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Re: 300 blk coaxial build almost done

Post by John A. » Tue Oct 11, 2016 12:24 pm

I'm interested in seeing how it works out for you.

Nice job on the machining.
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Re: 300 blk coaxial build almost done

Post by policetruck » Wed Oct 12, 2016 8:18 am

Still on nights, not able to go shooting until probably next week. Oh this is worse than waiting for the stamp.

Whiterussian, here is a picture of a spacer, they are all the same right now. And a picture of it disassembled which also shows the spacers.

Image

Image

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Re: 300 blk coaxial build almost done

Post by policetruck » Thu Oct 13, 2016 7:10 pm

Shot about six rounds through it this morning. I would've shot more but I am extremely low on ammo and only have about 6 more subs left (about 100 more supers). It's pretty good but, I think it could be a little quieter.

I can hear the bullet impacting the ground about 25 yards away but it's still not 100% comfortable without ear plugs. I shot 3 or 4 without earplugs and didn't get any ringing in my ears. I also noticed I get a lot of echo coming back from the tree line and probably from a nearby barn. I'm shooting in an open field with a barn 50 yards away and to my 2 o'clock. And trees to my right 100-150 yards away and trees in front of me about 250 yards away and plenty of open space behind and to my left. Open but not a safe direction to shoot.

I'm thinking I may re-orient some of my baffles and spacers. I was also thinking about cutting the steps a little deeper. I'm at .100" deep on my step cut on the baffle, this should be, and looks like it as well, about .010" or so above the start of the inner cone diameter. I'm thinking of removing another .025-.030" to get the step down into the cone ID.

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Re: 300 blk coaxial build almost done -- Range Report.

Post by T-Rex » Thu Oct 13, 2016 10:07 pm

In this pic, the clips pretty decent.
Image

But, in this pic, the one at 9 o'clock looks real shallow. They're all even?
Image

What's your orientation for the spacer notches, in relation to the cone clips?
Is your stack indexed the same throughout or did you vary it?

Have any pics of the brake inside of the blast chamber? Just curious how they mingle.
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Re: 300 blk coaxial build almost done

Post by John A. » Thu Oct 13, 2016 11:02 pm

policetruck wrote:Shot about six rounds through it this morning. I would've shot more but I am extremely low on ammo and only have about 6 more subs left (about 100 more supers). It's pretty good but, I think it could be a little quieter.

I can hear the bullet impacting the ground about 25 yards away but it's still not 100% comfortable without ear plugs. I shot 3 or 4 without earplugs and didn't get any ringing in my ears. I also noticed I get a lot of echo coming back from the tree line and probably from a nearby barn. I'm shooting in an open field with a barn 50 yards away and to my 2 o'clock. And trees to my right 100-150 yards away and trees in front of me about 250 yards away and plenty of open space behind and to my left. Open but not a safe direction to shoot.

I'm thinking I may re-orient some of my baffles and spacers. I was also thinking about cutting the steps a little deeper. I'm at .100" deep on my step cut on the baffle, this should be, and looks like it as well, about .010" or so above the start of the inner cone diameter. I'm thinking of removing another .025-.030" to get the step down into the cone ID.
OK, some questions.

1. Is it factory made subsonics?

2. Is it handloads? If yes, which powder?

reason I ask, I noticed a lot of first round pop with factory ammo and generally disappointed in the performance with my latest 9mm suppressor or earlier 308 can until I switched powder and obviously started rolling my own.

Also, it looks possible to open up the vents more to allow more gas away from the bore. Or add some holes in the spacer on the opposite side of the existing vents. That would also lighten the can some at the same time.

Just trying to throw some ideas out there.
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Re: 300 blk coaxial build almost done -- Range Report.

Post by policetruck » Fri Oct 14, 2016 9:33 am

T-Rex, the spacer vents were towards the exit end and aligned opposite of the step cut. I took plenty of pictures of the carbon and how it flowed through the cones and such. I think it can provide some clues. I did drill a small hole on the perimeter of the coaxial dividers and I noticed something interesting in the carbon patterns. It actually looks like the coaxial space refills through that port. But it looks like each coax space blows backwards into the previous one. I have a picture to show what I saw.

Here is the picture of that odd pattern. All the spacers had this pattern on them right at this hole.
Image

Here are some other pictures. Of the cross jet on the ID of the cones and the flow down the cones to the coax ports. And the flow through the spacer into the coaxial spaces.

Image

Image

Image

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Re: 300 blk coaxial build almost done -- Range Report.

Post by policetruck » Fri Oct 14, 2016 9:37 am

John,

They are factory subs.

I was also thinking of opening the ports more. I figure it couldn't hurt.

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Re: 300 blk coaxial build almost done -- Range Report.

Post by T-Rex » Fri Oct 14, 2016 11:35 am

Try spinning the spacer vents 180* along their axis.
Also, move the cleaner baffles towards the muzzle so you can get some good carbon comparisons.

I'm wondering if using the lower spacial pressure will help out.
I'd try some reorientation before cutting more material. Just for some more data.
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Re: 300 blk coaxial build almost done -- Range Report.

Post by John A. » Fri Oct 14, 2016 1:19 pm

Factory subs are loud.

There have been several of us have a lengthy discussion about it over at 300blackout talk forum.

The thing about factory subs, they're made so they're reliable in most all guns.

The thing with that though is, that isn't really optimal for how well it sounds.

I have been loading my own with a faster burning powder and it sounds so much better. Though I admit that I have had to replace my factory buffer spring with a lightweight spring, but for me was the logical choice because it's a dedicated subsonic/suppressed gun.

Now, mine sounds as good or maybe better than a suppressed 9mm or 38 special. Before I changed loads, it was as you described. Loud. And umistakable. Now, it's pleasurable because the fast powder has burned by about 6 inches of barrel length, and there is little the suppressor itself has to mitigate in terms of unburned powder that you're probably getting with the factory subs.
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