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SKULL 03-07-2013 06:13 AM

brass barrel bore size advice

i am raising money for a custom built brass nasty spring-feed pump.

i have 2 options for bore size

.678 and .686

i have used a unisizer ATS for most of my play, so bore never mattered a damn im lost. i have read a lot about over and underboring but i want to hear from the borg collective on this one.

what is better generally? i will be almost always using field paint so you never really know what they will be selling that day for sure.

I also live in toronto canada. indoor fields are generally fairly cool to play in, outdoors in the summer is brutal hot here half the time, i dont know anything about humidity levels but id say it can get bloody humid here.

whats my best bet between the two...but first you must know that i aim to double or even triple pump this sucker to get 2-3 balls stacked into each barrel for a 4-6 shot buckshot blast (for milsim room entry drills and general awesomeness).

but when i dont do that, id still like decent efficiency. i figure no matter what, i should get 30 shots (60 shots due to the double barrels) out of 2x 12g's that are in a buffertube air stock

accuracy i assume will always be quite good on a brass closed bolt system.

the .678 will also cost me about 75$ extra in build price, so matters a bit. but not if it will net me huge improvments

please correct me if im wrong in my assumption and shoot your advice this way, thanks for your input guys

jellyghost 03-07-2013 07:19 AM

I am very interested to hear other people's opinions, but when I play with .678 at my field, I get some ball breaks. The decreased accuracy from ball breaks outweighs the increased efficiency from the tighter bore, and two barrels probably means twice the ball breaks.
I am not sure if you can double pump with wedgits. Can someone tell me if that is possible?
I found this post by Craig Palmer on a sticky in the palmer section.

Originally Posted by CraigPalmer (Post 532667)
I mostly shoot a .690. It shoots just about anything.

In just the past few years paint has been getting smaller, Although, I think makers have heard the complaints and are making the balls a little bigger now. Smaller balls feed better.

As the cost of materials go up, the manufactures are less likely to throw the bad/small stuff out. Some of them would mix all of the bad stuff together, recap it and sell it as a cheaper ball. We don't see too much of that these days.

Humidity and storage plays a big part of the ball size. Sugar is used to to make the ball brittle. So yes, you can make the ball bigger by letting it soak up moister, but you will also get more bounces.

Really Cold DRY winter days and a small bore can be really hard on brittle paint.
I'll use a 690 and no wedigts for days like that with crappy paint.

A ball dropped at shoulder height should bounce off concrete 90% of the time.

If your stuck with small field paint, get the 685. If you have a choice in brand get the .690.

.685 and .690 are standard price. Any other size bigger than .685 and .690 requires a $40 hone charge.

Stilgar 03-07-2013 08:01 AM

I have .685 on my Brass (KP2 like) pirate and I have not really had any issue with that yet. It does have a cocker detent to hold in a ball.

I have been shooting almost everything out of a .675 brass freak insert on my other guns. I shoot Valken Redemption and Graffiti 99% of the time which sized around .682?

If you intend to double pump on a regular basis, I would recommend going with the .685 but I would also make sure you get some kind of detent system installed. Either the palmers ones, Widgets or whatever...

Getting 60 shots off 2 12gs in the config you want might be a stretch...but might be possible. 20 each side might be a more reasonable estimate and if you get more it is a bonus.

SKULL 03-07-2013 05:29 PM

thanks for the advice guys. Jelly that was a helpful article also

though i should clarify. im not getting this built by palmers. im going with someone else and they dont offer the .685. the size i can get is .686 ....i know, not a big diff but i dunno, maybe worth re-mentioning. I will be tuning this thing and using palmers guts though so i hope your wrong about efficiency stilgar...i hope.

anyone have any other advice? the more the merrier

Cunha 03-07-2013 09:37 PM

If it has wedgits, .686 is fine. Wedgits rule. Or a non PPS version of wedgits.

Doubles aren't the most efficient, for whatever reason..40 shots total with 2 12ies as posted above is pretty realistic, but thats just my guess.

SKULL 03-07-2013 10:15 PM

hmm maybe i should just go with 2 20 ball springfeeds then? then run out of both air and paint at the same time

im leaning towards the larger bore now, thats still not a huge bore, seems pretty in the middle

senghing27 03-08-2013 12:17 AM

I would go .686 and punch shallow to medium wedgits (or wedgit like) setup.

As for your tube length for the springfeed, I've been a fan of the 12-15ish range. 20 balls stacked side by side, the springfeed, and ramp is a lot of real estate. Double that by 2 and... well have fun reloading that sucker.

SKULL 03-08-2013 12:23 AM

agreed that will be 19 inches long or so. 15 x 2 sounds good. ill just try to get the efficiency to fire 60 shots worth on 2 12g's. might help that my field limit is 250fps

senghing27 03-08-2013 12:48 AM


Originally Posted by SKULL (Post 2647783)
agreed that will be 19 inches long or so. 15 x 2 sounds good. ill just try to get the efficiency to fire 60 shots worth on 2 12g's. might help that my field limit is 250fps

Anything double barreled just drinks propellant be that CO2 or HPA.
On my fully tuned PPS Painter, I would get 25-35 good shots off a 12 gram with FPS 280-290.

On double barrels, it only get's worse. If you want to go 12 gram only, then so be it, but it will get really expensive, really quick. Plus, the added stress when playing because you have to reload two springfeeds and 12 grams.

Shooting a nasty is one of the most satisfying things in the world, but I would suspect that you will probably have about 10-12 at speed shots (20-24 due to the double barrel config).

Also, what did you have in mind to have the 2 12 gram setup? Are we talking one 12 gram, full to empty, and then the second one punched open? Or both 12 grams punched open at the same time ala cooper t double 12 gram style?

IMO, get a vertical adapter and have it built in a way that you can have a 12 gram bucket changer, a 3.5 oz, or a bottomline to setup. That would be the most practical way to go about this.

SKULL 03-08-2013 12:59 AM

i plan on getting a rap4 12g adapter that holds 2x 12g's in a i gues similar to that coopert setup.

i really dont want air lines on this thing as it will be mil-sim looking when im done, but i do have a rap4 air through buffer tube i can attach a remote to if i need constant air, also i could go 13ci tank stock or 88g tank stock with my straightback asa.

im thinking the "stock" options should do me just fine. i am a bit sad by that shout count you described using 12ies but i at least have my bases covered. now i just need a 8ci or 13ci tank.

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