First Form 1 Build 6.5 CM

[fulldraw 11]

OK, building my first form 1 for my 6.5 Creedmoor. I am using all size D titanium parts from SD Tactical. My question is, what is the minimum safe sized hole for my baffles/end cap? I have access to a fabrication shop and they said they can precision cut/tap anything. Obviously, I want it is tight as possible (this can will never go on anything but my 6.5 CM) but don't want baffle strikes etc. Is there a definitive safe ID over caliber size? Any help is sooooo much appreciated.

[CMV]

I'd do a P or 21/64 size. .060" over. That's just me, some would go tighter. There is very little gain going as tight as possible on bore size all else equal and 6.5CM is still going to be loud. I've never seen published subsonic load data for it but if you were planning to work down a light trailboss load with 150ish gr pills that would be even more reason to go with a larger, not tighter bore because no idea how well that stabilizes....

[fulldraw 11]

Thank you for the insights. I found some info saying that .040 over is tightest you want to go, but if there isn't much advantage to 'as tight as possible' and it will stabilize better at .060 over, than accuracy always reigns supreme when comparing trade-offs. I will likely shoot SOME subsonics now that they are becoming commercially available, but will shoot 99% 140 grain Nosler, both range and out hunting. Not looking for 'hollywood' quiet, just something I can shoot in the woods without muffs (so I can actually hear the animals roaming about) and not bleed from my ears. Thanks again!

[Mousehouse]

The last one I built was .320. The one I am building now will be about the same. Using a bigger tube this time (1.625” OD)

The first one i built was a 1.5” OD, 8.8 inches long. It works but want to see if there is any difference.

[748]

How long are you going to go on that size D tube?

[fulldraw 11]

It's a 10 inch can, but I think it actually measures out to 9.8 inches or something close to that.

[748]

Let us know how it goes.
If I make a 6.5cm silencer I will use size D for sure, don't know if I would go with a 10 or a 12.

[a_canadian]

Thanks to spamming idiots this forum is rather sad, but still... felt like sharing. I acquired a Sig Cross in 6.5Creedmoor and because I don't like loud noises, made a suppressor for it. Lacking a proper lathe, just working with what is basically a tiny toy one, I improvised something using a Soda Stream CO2 bottle and some 6061 aluminum. Rod stock, plus some 10mm thick discs ordered from eBay, intended as glass table support things, which I modified to have stepped faces, slightly concave back sides, and steps at the edges to engage with tubular 6061 spacer sections which leave a 2mm gap between them and the bottle wall.

Mounting is via a section of rod stock bored out to fit a steel linear compensator, which is fitted with high temperature steel filled epoxy and drilled/threaded with stainless bolts, then that plug itself epoxied and bolted into the bottle from the outside. Not an ideal assembly method but it's what I can manage, and so long as I keep rate of fire to about a shot per minute it won't heat up so much as to weaken the epoxy. Gets quite uncomfortable to the touch after a 10-round magazine in 10 minutes, but the glue is rated to over 600 degrees Farenheit.

Bored to 11mm, I was more interested in staying well clear of the bullet than in ultimate quiet - understanding from the start that 6.5Creedmoor isn't going to be quiet in any case, just wanting it quiet enough that a very basic pair of fitted ear plugs make shooting very comfortable. The rifle shoots very accurately with it on, and I haven't even tried it without this 2.5lb can mounted. I made a small delrin button which snapped into the MLOK along the bottom of the handguard, carefully fitted such that it just barely touches the barrel, nicely preventing any barrel sag when this very heavy suppressor is mounted. That's so I achieve approximately the same POI should I ever have to shoot it unsuppressed on a hunt due to proximity of nosy people...

Fit to the barrel just meeting the handguard's end, this makes for about 2.5" of overlap, assuring excellent alignment. A dense low-friction technical plastic sleeve is bonded into the bottle neck and machined to achieve perfect concentricity.

[Historian]

"Thanks to spamming idiots this forum is rather sad, but still... felt like sharing."
Well said.

Sad there are folks that need to despoil rather than build.

If they accepted an offer to meet and share a meal I bet they could be saved -
as a Great Man said so long ago before someone CROSSED HIM up.

As for your build, kudos. Most appreciated.
Long ago here I brought up the use of spent CO2
cartridges for .22 build. Our esteemed NZ luminary Enfield did so and
shared results.

Best

[a_canadian]

I don't recall seeing Enfield's implementation of spent steel CO2 bulbs, but I did give it a try myself in an airgun suppressor. Tried both ends actually, the nipple ends as sort of convoluted cones and the other ends as domes. Didn't find suppression to be very effective. Certainly nowhere nearly as quiet as K baffles - which for a lower powered airgun such as I was testing on, about 10fpe in .22", can be delrin or aluminum with no difference in durability nor quietude.

I'd like to have a big enough lathe to have turned down the long Soda Stream aluminum bottle, as the thing is probably much stronger than necessary. On the other hand, with this being my first foray into something so high pressure, I didn't want to take chances. So it's a heavy beast and I've compensated for barrel droop with a delrin button, and that'll have to be good enough. Perhaps some day I'll have a lathe capable of cutting threads, then I can start using proper materials like stainless tubing and build something more comfortable to carry.

In general I've wasted a number of hours making conical baffles for various airgun and .22lr builds and found them all unsatisfying. So K baffles live in most of my suppressors. The exceptions are machined almost-flat cones with some surface steps and symmetrical triads of grooving around the entry points for a 6.5 Creedmoor build, and a dozen domed stainless steel washers (intended to secure skid plates on ATV bottoms) turned slightly smaller OD, opened out to 11mm, and stacked between aluminum tube sections for both an integral 9mm PCC tube and for a couple of muzzle-mounted cans for the 9mm PCCs of friends.

Seems the more intense pressures of 9mm and 6.5CM make for relatively little need for complex baffles, so steeper cones would make sense there - I just lack the machinery to make such things on that scale. But making K baffles for .22lr cans with 1" OD tubes is old hat by now, I've made perhaps a couple of hundred such baffles, mostly from 0.875" 7075 rod. Settled long ago on baffle length of 0.55" with just a slight radius at the waist and a shallow cone for the face to leave room for fairly deep grooving, to 'scoop' and swirl gases. These seem to drop a few decibels compared to baffles 0.75" or longer. My first few were about 1.25" long and left rather too much noise coming out the exit hole.

Even worse than with cones, I wasted far too much time and a lot of material (especially delrin, but also ertalyte and some aluminum) making monocores. Never liked the results much, but I persisted in all sorts of patterns for the cut out volumes, arrays of bored cylindrical and conical holes angling in from the sides, balancing internal and external volumes with vent holes... nope, nothing very useful there at all. So it's boring old K baffles for me. And several of those will go into a 3" long suppressor for the WSP I've started for my son, probably with a urethane wipe at the front. Won't be quiet, but it'll make him flinch less than unsuppressed. With the patent drawings for Downsizer's tiny pistol in hand, figuring out how to make it work shouldn't be too difficult, just tedious, mostly 'milling' on a cheap drill press as the tiny jig for milling on my lathe is proving too wobbly.