How much clearance?

[Rickstwowheels]

I have an Airgun Capital LDC in .25 cal. and .30 cal. The .30 caliber is too fat to fit and hits the tank. I measured the cones and the openings are (on average) 0.32". The Zan slugs I am using measure 0.29" or less. I tried firing several rounds through and it is very quiet. I am sure this is not ther recommended clearance but there did appear to be any clipping on vistual inspection. There is one post on this forum that discusses a ratio of over 2% needed. By my calculations I have less than 1%. What is the danger in running too tight a bore clearance?

 

[Berserkeley Mike]

How is the accuracy? Air strippers have about that level of clearance.

 

[Rickstwowheels]

How is the accuracy? Air strippers have about that level of clearance.

I just finished converting it (zelos) to 30 cal and don't have a scope on it yet. I will throw something on there and do some testing.

 

[rangur1]

If too tight, is there possibly an option to drill out/ream an additional 1/32” diameter clearance? You could also ask anyone with a Donnyfl Yokozuna 30 cal or impulse air owners what diameter they have as both are also cone style mods.

 

[Airgun-hobbyist]

@Rickstwowheels So long as there is no interference in regards to projectile clipping or on accuracy then you should be fine. Knowing whether there is clipping with a slug is hard to tell sometimes (especially with light clipping and maintaining fairly consistent accuracy) without seeing the projectile's marred shank. Shooting it into a block of gel or down into a bucket of water will usually produce a good specimen to examine. Otherwise, the inside of the cone holes may show light lead streaks.

If you feel there isn't enough clearance or if some of the cone hole ends show any lead streaking, simply opening up the ends evenly with careful strokes using a large diameter round chainsaw file works well.

 

[Rickstwowheels]

@Rickstwowheels So long as there is no interference in regards to projectile clipping or on accuracy then you should be fine. Knowing whether there is clipping with a slug is hard to tell sometimes (especially with light clipping and maintaining fairly consistent accuracy) without seeing the projectile's marred shank. Shooting it into a block of gel or down into a bucket of water will usually produce a good specimen to examine. Otherwise, the inside of the cone holes may show light lead streaks.

If you feel there isn't enough clearance or if some of the cone hole ends show any lead streaking, simply opening up the ends evenly with careful strokes using a large diameter round chainsaw file works well.

Thank you, I am going to try shooting it into water. That is a great idea.

 

[karl_h]

Awfully tight, I wouldn't do it. Commercial PB will not go below about 0.05 over bore size, and many/most not even that. Custom built for a single rifle never to be used on another where the machinist does both the rifle barrel and suppressor to assure close to perfection, they sometimes go tighter than that. But at least in PB land, going tighter essentially makes no difference, correct meters for impulse noise(thousands of dollars for a real meter) have shown that over and over again ad nauseum but people just won't listen. Case in point, my >1k 30 cal suppressor has an end cap of 0.380x" where x is at least .0005 (can't measure tighter than that with my tools, I just measured it after writing the previous sentences t,hat is greater than .07 over bore which is pretty much the norm for commercial suppressors.




You can have a safe to shoot alignment of suppressor/rifle bore but have accuracy/consistency issues if it is off enough but still safe. I had issues with an accurate 30 cal shooting 240 grain bullets subsonic, it was just fine without the suppressor attached, and the suppressor bore alignment was fine by manufacturer's drawings. I sent pictures with alignment rod to manufacturer (lawyers..) and they said it was fine and safe but refused to comment on any barrel manufacturer for the most part. Got on the phone with them, and they went so far as to say "we have not had any problems with that manufacturer" when I went through a list of pre-made barrels, but no other comment at all. My barrel they made no comment... Took a while but I got most of my money back and bought an actually slightly cheaper well known barrel that the supprossor manufacturer on the phone said they never had issues with them. Solved my problem, only wasted 100 dollars, give or take, in bullets/primers/powder chasing my tail before. Picture is roughly my alignment now, with a safe to shoot alignment that with my combination of equipment led to accuracy problems.

 

[Rickstwowheels]

Awfully tight, I wouldn't do it. Commercial PB will not go below about 0.05 over bore size, and many/most not even that. Custom built for a single rifle never to be used on another where the machinist does both the rifle barrel and suppressor to assure close to perfection, they sometimes go tighter than that. But at least in PB land, going tighter essentially makes no difference, correct meters for impulse noise(thousands of dollars for a real meter) have shown that over and over again ad nauseum but people just won't listen. Case in point, my >1k 30 cal suppressor has an end cap of 0.380x" where x is at least .0005 (can't measure tighter than that with my tools, I just measured it after writing the previous sentences t,hat is greater than .07 over bore which is pretty much the norm for commercial suppressors.




You can have a safe to shoot alignment of suppressor/rifle bore but have accuracy/consistency issues if it is off enough but still safe. I had issues with an accurate 30 cal shooting 240 grain bullets subsonic, it was just fine without the suppressor attached, and the suppressor bore alignment was fine by manufacturer's drawings. I sent pictures with alignment rod to manufacturer (lawyers..) and they said it was fine and safe but refused to comment on any barrel manufacturer for the most part. Got on the phone with them, and they went so far as to say "we have not had any problems with that manufacturer" when I went through a list of pre-made barrels, but no other comment at all. My barrel they made no comment... Took a while but I got most of my money back and bought an actually slightly cheaper well known barrel that the supprossor manufacturer on the phone said they never had issues with them. Solved my problem, only wasted 100 dollars, give or take, in bullets/primers/powder chasing my tail before. Picture is roughly my alignment now, with a safe to shoot alignment that with my combination of equipment led to accuracy problems.

View attachment 550659

Great write up, thank you very much. Knowing that close tolerances doen't yield a better result is really valuable.

 

[karl_h]

Great write up, thank you very much. Knowing that close tolerances doen't yield a better result is really valuable.

I was talking PB land, I don't know how much translates to air rifle land, but shouldn't be too much different. I actually had a machinist freind cut me an adapter for my big 30 cal suppressor mount so I could put it on the uragan barrel. I put it on my uragan compact with the shroud removed, it was as quiet or so close as it was irrelavent with the 30 cal endcap on, the alignment was good so I put the 22 end cap on and it was probably more quiet than the uragan with the baffled shroud, and as quiet with the baffled shroud + adding on the uragan suppressor on the end. Lower muzzle pressures in general with air rifles, and smaller volume of gas except in rare cases. The most quiet suppressed PB I ever didn't hear, was a friends 1920's winchester pump .22 short only gallery gun he inherited from his grandmother a few years after his grandfather died. Without the suppressor on the end of the barrel, it was more quiet than a standard 16" 22 rifle with a really good suppressor. Put on the 1920's tiny little suppressor, shorter than my little finger, and smaller in diameter than my little finger, with I think 5, maybe 6, small pressed spring steel baffles in it you could put your ear 2 feet from the muzzle and hear a very quite push of air that you could do way louder with your mouth blowing for 1/2 a second. There are always exceptions to the rule, the muzzle pressure on that 18" 22 short rifle was likely significantly less than a 10 meter olympic air rifle.