New Barrel for a Marauder...what length?

[1stElmerFudd]

I have a new .25 cal. Marauder that I am trying to get to 100fpe. So far it has a WAR valve, 17# spring, and a no bounce 94g hammer. I'm still quite a ways away from 100fp. I was thinking that a longer barrel might help use all that air I'm sending through it, but have no idea how long that barrel should be. Was hoping you guys might have some experience with this or at least have some food for thought. Any help would be much appreciated!

[screwwork]

Contact Travis at WAR and he can assist you without changing the 25Cal barrel.
He has larger poppets ID's and other poppet springs as well I believe for the WAR valve assembly to reach higher fps with 43 grain pellets.

[Bill G]

This probably a dumb question but here it goes.  Did you increase the port in the barrel?  If not, it could be restricting flow.  .188 is the max for a typical round port. 

[1stElmerFudd]

As per Travis' instructions, the port has been increased to .1875.

This gun is going to end up with a new barrel anyway, as I want to shoot slugs instead of pellets. Hoping for an idea of how long it can be, before the length hurts instead of helps performance. And also how much a longer barrel might increase the FPE. I've noticed that most of the .257 and larger calibers out there have barrels that appear to be about 28 inches. At this point, without doing a bunch of testing, I don't know that I'm pushing enough air to make full use of that much barrel.

[RayK]

I installed the same parts you have in mine and was able to get 4 good shots at a peak of 100 FPE with 71 grain black mamba pellets, but I had to fill to 3500 psi to get the peak of my shot string.  The 17# spring was maxed out and it was difficult cock and to hand load those ultra-long black mambas by hand without a single shot tray.  I decided that set-up was not for me.

I currently have it tuned for 16 good shots (845-865-841) at a peak of 71 FPE with 43.2 grain Eunjins from a 3150 psi fill.  If I fill to 3000 psi, I get 8 good shots within 15 FPS.  I took it out to shoot with Ron and the gang, but forgot my EunJins.  I had to shoot JSB Kings and I was surprised how accurate they were up at that speed (over 1100 fps).

Ray

[1stElmerFudd]

Thanks Ray and Don

That's what I was hoping to find. Someone who has had some experience with this set up or could point me to the people who might know.  You're very correct...it's a bugger to cock and my performance is still 30-40fp away from 100 with 43g EJ pellets

Ultimately I was thinking of turning this thing into a 500cc 250bar bottle gun, shooting 55-68gr boolits @ 900 to 1000 fps. That's the goal anyway.

[Rdsail]

I'm currently working on the same thing. I have a 26" TJ .25 barrel coming and also a war valve and a back up. My barrel is being machined for bullets and not pellets. The lead is made for 55g slugs this way I Can go up to 65 or down to 45.

I added lead to my hammer and turned it form 78gr to 109gr.

I don't have any numbers at yet but hoping to go over the 100 fpe. What size tport are you using? I bored out the opening on the breech to accept .306 tports. This way, I was able to have have a .203 tport. I believe that the war exit port is .203 but if you don't match the tport or barrel port it will not make any difference.

I will first test my modified valve to have .203 exit port and .256 throat.

[1stElmerFudd]

How did you choose the length for your barrel? At this point I don't have someone to machine a new barrel. The local gunsmiths don't seem to want to touch a airgun. Not sure why that is....
Who, may I ask, is doing your machining? Since TJs is on that side of the country it would make sense to have someone over there do the work and then ship it over here.

The exit port in my valve and port in the barrel are both .1875. The transfer port is just slightly larger at .190

Travis tells me that he has other people who have reached the 100fpe mark, so I'm a little puzzled as to why I can't seem to get mine there.