Bullet weight with ultralight gun?

[TerryYu]

I'm messing around with a p320rx/x5 based open gun (just for fun) and it's really light ~35oz with empty mag.

 

I tried my normal open load 10.5gr aa7 115gr tmj through it and it kindof hurts! A ton of straight back recoil of the very sharp variety. 

 

I think I'm looking for a softer recoiling load or perhaps more side ports in my comp (I can mangle it up with my drill press)? Currently I'm running a no name steel comp with 3 top ports and no side or poppel holes.  

 

I have 115, 124, 147 and aa7, autocomp, cfe pistol, hs6, and blue dot in stock. 

 

Any suggestions?

[Hi-Power Jack]

What kind of gun are you using for your 10.5 gr AA7 loads ?

[jim vaughan]

I found a great load using 160 grain coated bullets using a relatively slow powder, 6.5 grains of Somchem S221.

Admittedly I use a 9x23 case and a long overall length of 31.7mm. 

[kneelingatlas]

I agree with Jim, always use the slowest power with the comp, but a heavier bullet will soften that slap.

 

I suggest the 147s over 7-8gr of AA7

[jcc7x7]

A friend who is having elbow problems switched to 147 bullets in his 2011 open gun and it helped his elbow pain etc.

His splits to the a zone stayed the same time.

Fwiw

[zzt]

10.5gr is an awful lot to put through a no-name three-port comp.  It sounds like you have a lot of gas jetting out the front.  That's what is giving you the hard hit to the hand.  You have to match your powder to the comp.  You don't automatically use the slowest powder you have.  It may be that 124s over WAC or CFE might be all the gas your comp can handle.  Try the Brazos test.  If you get a lot of splatter, you want to add ports to your comp, move to a faster powder, go to a heavier bullet, or change comps to one with more chambers/baffles.

 

Here is an example.  Two of my Open guns have identical comps.  One has two 3/16" poppels.  When I was shooting Silhouette, the gun with no ports shot softer. The gun with poppels shot flatter, but hit my hand harder.  When I switched to Major Pistol powder, it was the opposite.  The no port gun hit harder, because there was too much gas for the comp.  The poppeled gun shot flatter and softer than it did before.  The extra gas worked the comp better, so the gun shot softer.

[TerryYu]

On 4/10/2019 at 6:35 AM, Hi-Power Jack said:

What kind of gun are you using for your 10.5 gr AA7 loads ?

 

It's a CZ75 Open gun that has a top end that kneelingatlas built. It shoots flat with that load but it also has a brazos thundercomp.

 

I'll try 147 with AA7 and 124 with WAC and see how that feels.

 

zzt, what is the brazos test? I don't think I've heard of that before.

[echotango]

38 minutes ago, TerryYu said:

 

It's a CZ75 Open gun that has a top end that kneelingatlas built. It shoots flat with that load but it also has a brazos thundercomp.

 

I'll try 147 with AA7 and 124 with WAC and see how that feels.

 

zzt, what is the brazos test? I don't think I've heard of that before.

http://www.brazoscustom.com/magart/0607.htm

[TerryYu]

Just now, echotango said:

http://www.brazoscustom.com/magart/0607.htm

That looks like a fun test, i'll see what I can see!

[TerryYu]

So I did the test and the comp well, sucked.

 

Going to try and machine my own now and was wondering if there’s any downside aside from weight if you build a comp that has an excess of ports and can dump all the gas before it reaches the last port. 

 

Also any opinion on angled side ports like on a muzzle brake? Was thinking of putting two in the last chamber to try and “pull” the gun forward to reduce the smack into my arm.