Pressure test on gas gun question

[RyeGuy338]

Just starting reloading for my 224 Valkyrie (Gas gun) and curious how to check for pressure signs? Thanks

 

[RegionRat]

Are you familiar with the procedure for bolt guns? It really is the same for the brass, but with just a few extra points to study.

One is the ejection pattern. Once you are past the concept of the bolt locking back on empty, you will also want to study the ejection pattern. Something closer to 3 o'clock is better than way forward or way backward.

Also, the condition of the rim. You can still have an over-gassed system if the port pressure is higher than needed and end up with rim damage.

So in addition to close inspection of the brass dimensions and primer condition, you will learn what the port pressure needs to be to keep the automatic functions happy and balanced.

There are several threads and resources to study the condition of brass and primers to estimate pressure problems. It all starts with a good study of the brass specs and your sizing dies.

You will need a decent set of inspection tools and specs to understand how your virgin brass is affected by the pressure and learn that going by just the primers is risky but better than nothing. I'll try to paste in the typical specs, but you should do the homework to make sure what reamer they used on your rig.

Try not to wildcat or play with lo/hi pressure till you learn the ropes. Play it safe and study up before you try to explore the margins.

Your 224 Valkyrie is intended to have a MAP of 55 KSI, but try to remember that it may want less in a semi-auto. You may find an adjustable gas port is an advantage, maybe not.

In addition to the lengths, watch this 0.4207 diameter and the 0.4031 diameter before and after firing. Do your "paper clip" inspections every time on a small set of brass that you run several times and learn when to retire the case well ahead of case head separations.

https://www.accurateshooter.com/technical-articles/primers-and-pressure-analysis/
https://www.floridareloading.com/index.php/2015/09/14/reading-pressure-signs/

 

[JR1200W3]

An overgassed AR and high pressure loads can be two different things. If you have an Adj gas block you can turn your gas off and shoot the ammo as single shot. Then look for pressure signs on the case head. Ejector prints, flat primers, etc. If you're gun is overgassed you can get torn up rims and confuse that with high pressure loads.

 

[RyeGuy338]

Are you familiar with the procedure for bolt guns? It really is the same for the brass, but with just a few extra points to study.

One is the ejection pattern. Once you are past the concept of the bolt locking back on empty, you will also want to study the ejection pattern. Something closer to 3 o'clock is better than way forward or way backward.

Also, the condition of the rim. You can still have an over-gassed system if the port pressure is higher than needed and end up with rim damage.

So in addition to close inspection of the brass dimensions and primer condition, you will learn what the port pressure needs to be to keep the automatic functions happy and balanced.

There are several threads and resources to study the condition of brass and primers to estimate pressure problems. It all starts with a good study of the brass specs and your sizing dies.

You will need a decent set of inspection tools and specs to understand how your virgin brass is affected by the pressure and learn that going by just the primers is risky but better than nothing. I'll try to paste in the typical specs, but you should do the homework to make sure what reamer they used on your rig.

Try not to wildcat or play with lo/hi pressure till you learn the ropes. Play it safe and study up before you try to explore the margins.

Your 224 Valkyrie is intended to have a MAP of 55 KSI, but try to remember that it may want less in a semi-auto. You may find an adjustable gas port is an advantage, maybe not.

In addition to the lengths, watch this 0.4207 diameter and the 0.4031 diameter before and after firing. Do your "paper clip" inspections every time on a small set of brass that you run several times and learn when to retire the case well ahead of case head separations.

View attachment 8523418
https://www.accurateshooter.com/technical-articles/primers-and-pressure-analysis/
https://www.floridareloading.com/index.php/2015/09/14/reading-pressure-signs/

Thanks for the this Yes I’m familiar with bolt guns and reloading for them. I do have an adjustable gas block. I will mess around a bit and follow above info. Thanks

 

[RyeGuy338]

An overgassed AR and high pressure loads can be two different things. If you have an Adj gas block you can turn your gas off and shoot the ammo as single shot. Then look for pressure signs on the case head. Ejector prints, flat primers, etc. If you're gun is overgassed you can get torn up rims and confuse that with high pressure loads.

That’s a good idea, wouldn’t have thought of that. I’ll try that, thanks