Centerfire bolt action, Integrally suppressed?

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mr fixit
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Centerfire bolt action, Integrally suppressed?

Post by mr fixit »

Just curious for information and knowledge mostly, but what are the pros and cons of integral bolt action centerfires? specifically around the .308 type cartridges'. I'm assuming that is a whole 'nuther animal from a screw on can.
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Re: Centerfire bolt action, Integrally suppressed?

Post by whiterussian1974 »

Cons: It is similar to shortening the barrel. You bleed off pressure sooner, so less motive power imparted to the bullet.
Pros: You "uncork" the barrel quicker, so it's also like adding to the length of the suppressor, which has benefits that volume alone doesn't account for.
However....you are also creating a "sump" similar to a tank's bore evacuator. This prolongs internal dwell time, thus lowering peak pressure by "smoothing" it over time.
Effectively, it's like taking a .300WM and lowering the blast pressure to .308Win. If you have enough barrel to begin with, you aren't losing much Muzzle Velocity.
Now if you are using a slow, low pressure round to begin with....major difference. Like .30 carbine or 9mm/.45ACP. Then you can get Hollywood Quiet where the firing pin and action cycling will compete to be the loudest part of the firing sequence.
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Re: Centerfire bolt action, Integrally suppressed?

Post by whiterussian1974 »

Which Cartridge and barrel length are you considering?
That makes answering your questions much easier.
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Re: Centerfire bolt action, Integrally suppressed?

Post by mr fixit »

308. Was already planning on cutting barrel to 16" so i could add suppressor
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Re: Centerfire bolt action, Integrally suppressed?

Post by whiterussian1974 »

By the time that you cut back to 16" you are already losing a LOT of energy/velocity.
I'd suggest just having the can reach back over the barrel, and then port the barrel into the "reflex" volume. This sets aside a chuck of the gas mass, and allows it to cool and swirl, while the remainder is exiting the muzzle and processing through the can. Then the "sump" empties into the barrel, and is sequentially processed through the baffle stack, after that volume has gone through the first several baffle stages.

I imagine that you are using this for Hunting? If not, then velocity might not matter to you, and that would change things a bit. But generally, I think that my above advice and input are sound.

Hopefully others will weigh in and give their input and experiences also. :)
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Re: Centerfire bolt action, Integrally suppressed?

Post by mr fixit »

My complete thought on it was to have a 16" barrel and add a can on the end, trying not to make it so long as to be unwieldy. IF doing an integral, I could see having an overall length of 22" or even 24". Finished overall length is a big matter either way.

There is always the advantage of being able to use the can on multiple platforms, but I could always just do another stamp.

So let me ask this;
specifying .308 and overall barrel length being less than 26" max (either as integral or with can added) What are the pros and cons of integral vs the add on can?
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Re: Centerfire bolt action, Integrally suppressed?

Post by a_canadian »

Integral can be a bit more forgiving in terms of integrity of the blast baffle, a significant reduction in pressure in that chamber owing to the large expansion volume behind it and around the barrel. This becomes even more the case with a ported barrel but that's not what you're doing here.

Alignment/strength of an integrated suppressor design can be significant. Of course a muzzle mounted suppressor can be perfectly aligned, but it is all coming from the threads and shoulder which are relatively tiny. Aligning from some inches back on the barrel, provided the bore and barrel outside surface are concentric with each other (far from guaranteed, but often the case), makes for an easier time in establishing that alignment as a new suppressor maker, while resulting typically in a can which is hard to damage should the gun take a fall while scrambling in steep terrain etc. a 1/2" thin-walled threaded section of the barrel can even be snapped off by a muzzle can in such a fall. An integral probably won't notice.

With an effective blast baffle design correctly spaced and adequate venting back over the barrel, there can be a small improvement in noise reaching the shooter. It's not as significant as good baffle design compared to poor design, but every bit counts. The baffle stack portion can be slightly shorter for the same level of noise reduction compared to a muzzle can. This seems key to your particular requirement of keeping the OAL short. For example, I get identical numbers and subjective noise impression from one with 9" of baffle space, muzzle mounted, and a 13" integral with only 6" of baffle space, mounted on the barrel of a 9mm carbine, the two cans using the same baffle type and the barrel being 18.6" long. Shortening that barrel to 10" and porting it midway, using the integral slightly modified to work in this configuration, results are identical to the long barrel but velocity is significantly reduced and OAL of the carbine is vastly more practical for carrying around the woods.

An integral looks cooler, continuing the lines of the gun instead of having a pencil barrel hanging out there with a big cylinder dangling from the end. :D
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Re: Centerfire bolt action, Integrally suppressed?

Post by whiterussian1974 »

You are far more eloquent than I, a_canadian.
Thanks for the excellent explanation. :D
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Re: Centerfire bolt action, Integrally suppressed?

Post by whiterussian1974 »

Here is a good example of a reflex design: https://www.youtube.com/watch?v=ZUDwCC0 ... _rel_pause
Porting 4 inches behind the muzzle still has benefits that a true reflex can't replicate. The VSS 9x39mm suppressor vented gas from a series of barrel ports behind the muzzle. Of course the bent metal baffle strip was complete crap, replace that portion with 60* cones or radials.
Image
Image
If you are thinking about a 16" bbl. Then start with 20-22" and mount the can OVER the last 8"s of the barrel. Then port 4" behind the muzzle and allow the gas to dump into the coaxial volume.
20" bbl, ported at 16" and extending 4" of baffle section in front of the muzzle for OAL of 24".
Or 18.5" bbl, ported at 14" and extending 5.5" of baffles would give better suppression, but sacrifice velocity. If you are handloading, you can minimize the velocity drop, so maybe this doesn't matter for your application.
If you extend the can all the way back, you can maximize volume, rigidity, and perhaps that is your best option?
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Re: Centerfire bolt action, Integrally suppressed?

Post by ECCO Machine »

.308 class cartridges are about perfect for an integrally suppressed rifle that still has enough oopmh to do things like hunt big game or print small groups at several hundred yards.

You're still going to give up some velocity if you want something that's not a truly long stick, but the short action cartridges do much better in 16"-18" barrels than larger rounds. That said, I would avoid the more overbore varieties like .22-250 or .243, as those still need some barrel length to achieve their performance. .264-.30 caliber cartridges burning 40-50 gr. charges is the sweet spot for integral rifles, IMO. So 6.5 Creed, .260 rem, 7x57, 7mm-08, .308, 300 savage, etc. The short mags may be short action and slightly more efficient than "full size" magnums, but they still burn a lot of powder and will still see dramatic loss in velocity going from ~24" to 16"-18", becoming little more effective than the .308 based rounds while also being more difficult to suppress.

At any rate, a 16"-18" barrel with porting, and then a core as long as you're willing to tolerate. Diameter-wise, I would still plan on 1.5" tube. They don't look too wonky, and most stocks can be inlet for them without turning the fore end into the likes of what you find on old SxS shotguns.

Here is an example, one I just finished for a shop demo. It's a Mossberg Patriot 7mm-08, 18" ported barrel, 10.5" core for a 28" effective barrel length. The actually suppressor length is 25.5", and the whole thing weighs 8-1/4 pounds. Firing normal Winchester 140 gr. factory loads, the sound is about the same as a good .22 pistol host with a premium rimfire suppressor. Yes, I'm serious.

Image

This is another I did this summer, a Bergara B14 in 6.5 Creed. It has a 16" ported barrel with a 9" core for an effective barrel length of 24.5". I don't recall the weight exactly, but it was heavier than the Patriot, over 9 lbs. Heavier stock, beefier barrel. Anyway:

https://www.youtube.com/watch?v=wpi0A0Z ... HPfBd658rk

In terms of what to do with the chamber behind the core, I say not much. I have not found any type of filler to help. The gasses bleeding back through the ports is the least of the noise on the front end anyway, so you're really only hurting your internal volume by putting stuff in that chamber.
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Re: Centerfire bolt action, Integrally suppressed?

Post by gunny50 »

I found that using a reflector tube like the enfield Delissle integrals better than packing material. It also lengthens the path for gassflow to the front.
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Re: Centerfire bolt action, Integrally suppressed?

Post by mr fixit »

ECCO Machine wrote: Sat Dec 12, 2020 11:49 am
Here is an example, one I just finished for a shop demo. It's a Mossberg Patriot 7mm-08, 18" ported barrel, 10.5" core for a 28" effective barrel length. The actually suppressor length is 25.5", and the whole thing weighs 8-1/4 pounds. Firing normal Winchester 140 gr. factory loads, the sound is about the same as a good .22 pistol host with a premium rimfire suppressor. Yes, I'm serious.

Image


In terms of what to do with the chamber behind the core, I say not much. I have not found any type of filler to help. The gasses bleeding back through the ports is the least of the noise on the front end anyway, so you're really only hurting your internal volume by putting stuff in that chamber.
Mind if I ask how you mounted that, I like the looks. I'm assuming some type of 2 point mount, a taper on the breech end?
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Re: Centerfire bolt action, Integrally suppressed?

Post by ECCO Machine »

mr fixit wrote: Tue Dec 15, 2020 8:10 pm
Mind if I ask how you mounted that, I like the looks. I'm assuming some type of 2 point mount, a taper on the breech end?
It's essentially a 10.5" tubeless muzzle mounted suppressor with a big tube over it that extends back to the receiver. The barrel is ported, and there is a collar with O rings inside and out that seals to the barrel & the tube. The barrel is profiled for it with a shoulder.

This is a different build that had a thicker barrel, so I cut the O ring grooves on the barrel instead of inside the collar bore, but basically the same set up:

Image
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Re: Centerfire bolt action, Integrally suppressed?

Post by ECCO Machine »

Finally got around to chronographing with the 18" ported barrel (30 ports from the 14.5" to 17" mark) on this integral. 7mm-08 proved to be a good choice. With a 46.0 gr. charge of H414 (not a max load), 150 gr. bullets averaged 2,641 FPS. These loads would probably clock around 2750-2800 from a 20" unported barrel, closer to 2,900 in a 24" tube. Some loss was expected, but the efficient little cartridge fared pretty well in the short tube.

The 150 gr. bullets over 46.0 grs. IMR4350 were a bit slower, averaging 2,549 FPS.

Factory Winchester 140 gr. loads averaged 2,623 FPS.
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