Accura- Optima day - Also modded BP

[frontier gander]

I took both the Optima and Accura out to play. I shot the Optima first using my shooting stix set up and the highest shot was due to the owner failing to remove the oil from the barrel I was using the 10# as my aiming point. All at 100 yards

Next up was the Accura and for the first 6 shots i was all over the damn place. I finally figured it out.. Needed a few minute cool down between shots! Next 2 shots at 100 yards were perfect! Not to shabby for open sights

Alright, Saxman when he sent his Kodiak to me, included a factory plug and 2 modded plugs with the lehigh vent linters installed, as well as the flash channels i believe being enlarged to 1/8". While shooting his kodiak i noticed a lot more blow by with the modded plugs. Theres a pretty big difference and so i wanted to double test but use that plug in my Accura has its much easier to see the blow by. Sure enough, #1 shot had blow just flowing out the forearm, Popped it open and it was a mess.

Factory Plug after 8 shots,

Modded Plug after 8 shots today,

The factory plug basically just had primer dusting that wiped off with my thumb. The modded plug is going to take some scrubbing to get clean now.

Either way, both rifles are ready to hunt! After i shoot the Accura with the original plug to make sure everything is still ok accuracy wise.

 

[Anonymous]

Did the modified breech plug shoot just as accurate as the unmodified plug?

 

[GM54-120]

What primers are you using? I found Win209s to be the cleanest BY FAR in the Accura in terms of blowby. They are the longest too.

One has the vent liner mounted nearly flush just recessed a bit. In mine the one with a deeper vent liner pocket and a head spaced primer pocket is about as clean as possible.

The one that is nearly flush and no head spacing of the primer pocket is as clean as the OEM plug but has better ignition with milder primers than the OEM plug. Plus carbon builds up slower in the breach plug. I can go an entire range session without a drill bit or torch pic. Using a OEM plug i had to clean the channel and flash hole at some point during the longer range sessions.

If i used CCI209M mag primers and a OEM plug it needed cleaning sometimes in as little as 10 shots.

 

[ronlaughlin]

..............................Alright, Saxman when he sent his Kodiak to me, included a factory plug and 2 modded plugs with the lehigh vent linters installed, as well as the flash channels i believe being enlarged to 1/8". While shooting his kodiak i noticed a lot more blow by with the modded plugs. Theres a pretty big difference and so i wanted to double test but use that plug in my Accura has its much easier to see the blow by. Sure enough, #1 shot had blow just flowing out the forearm, Popped it open and it was a mess..............................................

I imagine the flash channels have been drilled with a # 21 drill, so they are 0.1590" not 0.1250", which is your guess. A 5/32" drill is a good size to use to clean the hard carbon from the flash channel of them modified breech plug.

It has been suggested that the lehigh vent liner would reduce blow by some, because of it's shape. That is possible, but i have seen nothing in my shooting to make me believe this is the case. Apparently, nor have you.

It is my experience that blow by is most influenced by a smooth primer seat, and head space. A nice tight head space will eliminate all blow by, if the primer seat is smooth. If you have a caliper, it would be instructive to us all if you could compare the 'head space' of these three breech plug.
It is not very likely, in my mind, that modifying these breech plug 'caused' them to allow more blow by. Too much head space and/or a rough primer seat is the likely cause.

It also has been my experience when shooting an Accura, Omega, and Triumph that a 'new' breech plug usually has very little blow by. After many shoots, the breech plug in my Accura, and Omega started to exhibit flame cutting in the primer seat. This results in more and more blow by. When a breech plug shows wear, it is a good time to 'fix' one or both ends.

Hopefully you have a caliper, and can investigate, and share with the forum the cause of the blow by, when using these breech plug.

 

[frontier gander]

No way of measuring inside of there. Both plugs are messy in the Accura and down right filty in the Kodiak. I put the factory plug back into the Kodiak and used tape. No longer messy in there, Same with the Accura.

All i use are CCI 209M's as they are nice and hot and i dont have to second guess them.

On the Factory plugs, ive gone over 30 shots without cleaning out carbon. No hang fires with the CCI 209M's.

 

[ronlaughlin]

No way of measuring inside of there. Both plugs are messy in the Accura and down right filty in the Kodiak. I put the factory plug back into the Kodiak and used tape. No longer messy in there, Same with the Accura.

All i use are CCI 209M's as they are nice and hot and i dont have to second guess them.

On the Factory plugs, ive gone over 30 shots without cleaning out carbon. No hang fires with the CCI 209M's.

All it takes is to measure the length of the breech plug with the primer installed. This is what makes the head space. The length of a 'new' Accura breech plug with a Federal 209A primer in my hands is 1.291". The length of the breech plug and primer installed in my Accura is 1.304". Hence, the head space is reduced by 0.013" with this modified breech plug.

The reason it is modified is because the primer seat had severe flame cutting. I drilled the primer seat some deeper with a letter C drill which removed the flame cutting, and am now using a silicone o-ring. This combination of reduced headspace, and a compressed o-ring results in zero blow by. The other end of the breech plug is also modified to accept a vent liner. Currently, the installed vent liner is one supplied by Precision Rifle. It is possible this breech plug will give 100% ignition using W209 primers with BH209, but will one ever 'know' this for sure.

As you know, a new breech plug works just fine without any modification, if one uses magnum primers with BH209.

 

[frontier gander]

oh okay, i can do that then. It will be a few days though as im busy with some new gear to play with.

 

[GRANDBOW]

blowback

ronlaughlin;
I agree with you on the primer, and that is the sole purpose of blowback. I have had two Remington 700's converted to Denny's ignition system. I get no blowback whatsoever, as long as the primer is seated quite firmly. In this conversion a .32 case is used, and if is just a smite short, blow back will accur. I check each case for fit, and if the bolt closes easy I discard it. If that case is not tight, one gets blowback. Changing the breach plug will aid in ignition, depending on the change. I have also tried this on my kight KRB7, by adding an " O " ring inside the primer pocket. With it, no blowback, without it blowback is terrible. The primer is the culprit.

 

[GM54-120]

Agreed, mine that has been primer head spaced is awesome in the WinApex AKA CVA Kodiak. It has NEVER shot this clean. Using the factory plug in low light you could even see a flash in the breach area and always a puff of smoke.

Now primers look new and the only carbon is on the flame side of the primer. Almost none is ever on the sides of the primer. In my Accura i mainly wanted better ignition with Win209s and i got exactly what i wanted. Its not really any cleaner than the OEM plug but ignition with Win209s sofar is perfect. Not a single hangfire and end of day cleaning the BP is a breeze to get it totally spotless with the removable liner.

The older CVA plugs flash hole is close to only .028 and that is really small for BH209 and a mag primer. All the gurus ive talked to recommended a minimum of .032 and sofar any flash hole that size or a couple thousandths larger have been totally reliable with any standard 209 primer.

But opinions vary