Sub bore cartridges and suppressors.

[germanlongbow]

Any fellow shooters with sub bores, specifically hot rod 20's shoot with suppressors? If so, anyone having issues with accuracy with can on versus off? I build a 20 BR two years past to shoot 55 gr Bergers. Shot sub 0.2 with can off and 1 MOA with can on. Frustrated I moved onto a 20-250. Phenomenal acurracy with can off. Shot a 0.210 inch three shot (outside to outside) at 100 yards. Can on same load 1.5 inch group. Not an issue with any of my larger caliber rifles. Any clues??? Thanks Scott

 

[5spd]

I will have to test my 20P w/can off as I have only been shooting w/can on to date.
This is on an AR15, 22' bbl, so Im not getting .300" groups either.

 

[BradY]

Any weight added to a barrel after load development is going to alter group performance. Your basically putting a non adjustable tuner on your gun. The good thing is you have proven that the barrel can shoot, you just need to tune it with the weight on.

Try the load development process again with the can on. It may just be seating depth that you need to change.

 

[germanlongbow]

Not to be a smarty pants. All loading for this rifle was done with can on except first load to insure no baffle strikes. Just to make sure the can was the issue I went back and reloaded all previous loads x 2. Shot all loads with can on. Then shot identical loads with can off. Can is the issue. The barrel is 28 inches 1.250 straight diameter. Not a lot of harmonic fluctuation going on here. Now with that being said, I have several other heavy barrel rifles chambered in 223, 243 AI, 25-284, 6-284, 6.5x284, 280AI and 308. All were developed loads with can off. Can on has no effect on accuracy what so ever. I shoot both a 223 and 30 P1 TBAC direct thread cans. My buddy shoots a Surgeon 260 with 26 inch Krieger heavy varmint contour with Yankee Hill thread on can. I did the test loads for his rifle with can off. Shoots sub 0.2's all day long with can off. Can on his groups open to 0.4-5moa. I went back same load but with my can. Back to 0.2 groups. Cans will mess with as well as maintain / improve groups depending on can. With this being said. What is it about 20 cal barrels that don't like cans on??? I appreciate the insight of members of this forum. No disrepect is intended. THanks Scott

 

[AusFclass]

OK first a disclaimer. . . . suppressors are illegal in Australia so I have no first hand experience with using them but I have a couple ideas.

My first thought was the harmonics. Removing or replacing a weight would have some effect but as you say probably not that much with the barrel profiles and the range that your using them.

My second thought is that I know some suppressors are marketed as being "universal" or designed to work over a range of bore diameters. I'm thinking that if the holes through the baffles are disproportionately too large for the small caliber that you are using some gas may be getting ahead of the bullet and bouncing off the baffles and back against the bullet disrupting it's flight inside the suppressor?

Are you using a suppressor specifically designed for sub calibers?

Further from that you say some cans work better with specific barrels than others. Could the way they are crowned and the design of baffles determine what combinations work better together depending on how the gas is angled and captured as the bullet leaves the barrel.

 

[5spd]

My test this weekend had my 20P shooting 1.5" high and 1.5" right with the can off, with it on dead on at 100yds.

 

[rvn1968]

What dia bullets do you use in a 20-250 ?

 

[germanlongbow]

20 caliber (204). 55 gr Bergers

 

[rvn1968]

That's what I thought,I was surprised by your .006 three shot group at the start of this thread. Very impressive,what kind of rifle are you using ? Any pictures ? Tom

 

[germanlongbow]

I built a 20-250 on a Surgeon 591 Repeater short action. Pacnor 1x9 twist 1.250 x 28 fluted heavy barrel. Jewel HVR trigger. McMillan A5 in Desert Tan. Surgeon bottom metal / detachable 10 round magazine. Yes its heavy. I have a friend in Winfield Iowa build all my rifles. I built this one to prove to another friend I could shoot 1K yards with it. The fact that I can't get it or the 20 BR to shoot with can on is quite frustrating to say the least. Send me a pm I'll send a pic. Still struggling to upload pics here for some reason. Scott