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Posted: 9/19/2009 5:15:31 PM EST
Does anybody know, or can you direct me to, the calculations used to determine the proper (approximate) gas port dimension for calibers other than .223 used in the AR-15/AR-10 series weapons? THX.
Link Posted: 9/19/2009 6:01:04 PM EST
Good luck with that one!

I don't think that there are any easy formulas. There are so many variables involved, it is probably best learned by experimentation. I have called or emailed several custom barrel makers with gas port questions - and they have all refused to provide specs, saying that it is "proprietary information."

You don't say what you are working on, but when you get it all figured out and working - let us in on all the details.
Link Posted: 9/19/2009 6:38:30 PM EST
Link Posted: 9/19/2009 7:03:26 PM EST
LOL! Actually, I was hoping some internal ballistics geek on the forum here would jump right in with the answer!

There must be some powerfull V00-D00 at work here, because I had disscussions with two darn good service rifle smiths yesterday regarding this subject and both answers were the same––––"I'll start small and see if it functions. We can always make the port bigger".

I thought people went to school to learn this stuff?

BTW, the project is a .264 PPC Imp. in an AR15. When it is finished I will provide the "secret" hole diameter. HA!
Link Posted: 9/20/2009 4:42:09 AM EST
Originally Posted By wizzer666:
LOL! Actually, I was hoping some internal ballistics geek on the forum here would jump right in with the answer!

There must be some powerfull V00-D00 at work here, because I had disscussions with two darn good service rifle smiths yesterday regarding this subject and both answers were the same––––"I'll start small and see if it functions. We can always make the port bigger".

I thought people went to school to learn this stuff?

BTW, the project is a .264 PPC Imp. in an AR15. When it is finished I will provide the "secret" hole diameter. HA!


When one is in unknown territory, that is the best approach. I would hazard a guess with your wildcat being based on a PPC case that it would be close (slightly smaller) to the 6.5 Grendel port size.

Link Posted: 9/20/2009 5:29:33 AM EST
[Last Edit: 9/20/2009 5:31:35 AM EST by advntrjnky]
Quick Load can help a little by giving you the internal pressure at a given distance down the barrel....ie port pressure. I don't remember what the AR needs for minimums (or dwell time), but the info is out there. then start small and open it up as needed. Quick Load will also help you to refine your powder choice and start loads to give you your desired pressure curve.

advntrjnky
Link Posted: 9/20/2009 12:28:50 PM EST
Originally Posted By wizzer666:
Does anybody know, or can you direct me to, the calculations used to determine the proper (approximate) gas port dimension for calibers other than .223 used in the AR-15/AR-10 series weapons? THX.


I use an adjustable gas system, like an adjustable gas tube or gas block. The amount of gas pressure is due to the type of powder, primer, and bullet weight. That's IMHO.

Mike

Link Posted: 9/20/2009 1:46:46 PM EST
Originally Posted By MikeinGA:
Originally Posted By wizzer666:
Does anybody know, or can you direct me to, the calculations used to determine the proper (approximate) gas port dimension for calibers other than .223 used in the AR-15/AR-10 series weapons? THX.


I use an adjustable gas system, like an adjustable gas tube or gas block. The amount of gas pressure is due to the type of powder, primer, and bullet weight. That's IMHO.

Mike



+1 on the adjustable gas block.
But we still need a hole to start with.
Does anybody happen to know the port dia. used on the 24" Grendel brl?
Link Posted: 9/20/2009 7:40:43 PM EST
I have quit a few ar-15 barrels; ill get a list of gas port diameters and post them in the next couple of days.
Link Posted: 9/20/2009 7:47:41 PM EST
Originally Posted By wizzer666:
Originally Posted By MikeinGA:
Originally Posted By wizzer666:
Does anybody know, or can you direct me to, the calculations used to determine the proper (approximate) gas port dimension for calibers other than .223 used in the AR-15/AR-10 series weapons? THX.


I use an adjustable gas system, like an adjustable gas tube or gas block. The amount of gas pressure is due to the type of powder, primer, and bullet weight. That's IMHO.

Mike



+1 on the adjustable gas block.
But we still need a hole to start with.
Does anybody happen to know the port dia. used on the 24" Grendel brl?


You might want to try using set screws with different size holes, that is how I found the proper gas port for the 50AE I built.
Link Posted: 9/21/2009 6:30:51 AM EST
I have done a couple of wildcats. Start small lets say .070" and test it. That is the only true way of getting the proper gas port hole size. Mike
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