What is the maximum flash hole size for a CVA Accura BH 209 QR breech plug. At what point in size of the flash hole would it affect accuracy. Is it better to purchase a new one or have a plug modified for an insert.

When the flash hole is large enough that it allows soot to be blown right through the primer, it is too large. The flash hole holds back the pressure of the powder burn, but when it grows too large , the pressure getting to the primer increases to the point where it blows right through the primer. Another tell, is when the flash hole is large enough it allows granules of powder to fall into the flame channel, it is too large.

It is my opinion the Blackhorn QRBP is not a good candidate for the modification, so it can utilize the insert (vent liner). My reasoning is the flame channel is already quite short, and installing the vent liner will make it even shorter. It is the volume of the flame channel that absorbs some pressure from the powder burn, and keeps the pressure low enough, it doesn't blow right through the primer. A Blackhorn QRBP would end up with a real small volume flame channel when the vent liner is in place.

So.. in my opinion, your best choice would be to modify your standard QRBP, so that it will utilize the insert. Thus modified the standard QRBP will reliably ignite Blackhorn, and with it's longer flame channel, the pressure on the primer will be much lower. When the flash hole in the vent liner grows too large so that soot is blowing through the primers, it can be readily replaced.

Another option would be to have PRbullet convert your Blackhorn QRBP over to use large rifle primers in their adapters. The larger worn flash hole in your plug will not cause blow by to go right through the rifle primers; they are designed for much higher pressures than they will experience in a smoking muzzle loader. The worn flash hole is actually beneficial when using rifle primers. If you already reload cartridges, you will only need to add a 22 Hornet shell holder, and you can prime, and deprime the adapters with ease. You don't need to worry about the flash hole growing larger (too large), because the flash hole will never get any larger, when one uses rifle primers.

To me, the least palatable option is to purchase a new Blackhorn QRBP, but this, in my opinion, would be better than modifying your old plug for the insert.

thanks Ron I will use BH 209 in my plugs, and a w209 primer, is this ok
Sent you a PM

Should work just fine, if you aren't using the OEM QRBP.

PM sent * * * *

I would suppose that different guns have enough difference in design that they would vary in this some, but the first thing I notice in my TC inlines is the same thing I notice in my traditional rifles when the nipple is to enlarged and that is fliers start showing up in every group.

Exactly correct Lemoyne. Too many hunters blame inside the bore when accuracy suddenly starts dropping. Many times it's that hole causing it, whether it be a nipple or breechplug.

I am so upset with myself right now. I let Knight Rifles snooker me into getting the Knight Vision with those red thing-a-ma-jigs. Guy told me over the phone that it waterproofs the breech area and reduces blowback. Now I'm reading everywhere that there's less blowback with it's naked breechplug, more-so than wearing that red ML condom.

Thank goodness I'm shooting real black and not needing hot primers. My cooler Goex powder and cooler primer combo should help my cause.

Lemoyne you kick started my memory, I have a .54 renegade that started hang firing for no reason. While cleaning it I noticed the flash hole was oblong, I didn't see how that could make a difference but replaced it anyway, problem solved.

TripleSe7en I have a brother in law that has a knight vision and he told me you can buy the bare primer breech plug, for not a lot of money.

Since no one knows the extreme of a flash hole I called CVA, they said they were not aware of any flash hole growing when shooting the gun for a length of time.
Since September I have 2 QRBP that have grown from .027 to .029 and .030
I have ordered a drill set with #61 to 80 and will keep tract and see what happens, I may not live long enough, Ha! Ha! but I will report any findings in the future as to when hang fires start or group sizes open up due to the flash hole