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Author Topic: Don cothran 308  (Read 2918 times)

oneshot61

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Don cothran 308
« on: November 18, 2016, 07:46:56 PM »
So, I have been blessed with the opportunity to own one of Mr. Cothrans creations in 308. Not only to own one, but because of my job I had the opportunity to meet him in person and pick up my new gun. I  Cannot say enough good things about Mr. Cothran. A pleasure to deal with, a craftsman that puts his heart into his work, and a real gentleman.
 I've not had but about an hour to shoot this gun but what a joy to shoot. I weighed the gun and stock on my bath scales (all I had at the moment) it says it weighs 5 lbs! TJ 1/20 twist barrel, 25'' in length, rear cocker with hammer spring adjuster and the hammer is adjustable for stroke as well. The valve is his balanced valve that he makes for the discovery. (He makes one for the marauder as well)
 As a bonus, this gun came with a custom stock, that upon research, appears to be a Michael Chavka stock, made on November 12 2012, and is either the first or one of the first thumbhole stocks that he made. In need of some tlc, I refinished the stock and laid on 4 coats of clear satin before reinstalling the action.
 The short hour I had at the range, this thing has some good power and accuracy for a 25'' barrel. 110 grain @ 841 with just a bit of adjusting and 102 grain @ 850 fps. These numbers are on a 3100 fill, and I can go a bit higher if I desire. Very easy to cock using the rear cocker and of course loading is a breeze as there is no tension on the bolt. There is a tipping point so to speak with this valve where more hammer spring really doesn't do anything but maybe waste air, I think due more to the length of my barrel and weight of the bullet. Backing off until at the tipping point, then using the clock as a reference, counter clockwise at one hour at a time (1/12) until I found a sweet spot. There is more power to be had for sure and spoke with Mr. Don about opening up the valve a bit more for the 308. I'm at .257 port now. Just for fun I put on a barrel extension and went 110@ 865, 102@ 890 on the original tune :). Ill be doing some more tuning this weekend and hopefully have some numbers to post.

« Last Edit: November 19, 2016, 01:27:34 PM by oneshot61 »



Monkeydad1969

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Re: Don cothran 308
« Reply #1 on: November 18, 2016, 07:50:44 PM »
That is a beautiful rifle.  Once you get it right, you'll really need to take it out for a hunt.

Joe
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oneshot61

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Re: Don cothran 308
« Reply #2 on: November 18, 2016, 07:58:35 PM »
Thanks Joe! I agree, the combination of the two craftsman could not compliment each other better. Air rifle season just kicked in here in Alabama, so it will see some deer and hog action in the next week!

Monkeydad1969

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Re: Don cothran 308
« Reply #3 on: November 18, 2016, 10:42:25 PM »
You're lucky.  I don't have the ability to hunt large game with an air rifle here in Colorado.  But Jan. will soon be here and I will be bound for Texas for a air rifle hunt for Spanish goats, hawgs, predators and some rabbits and P-Dawgs after I get back from Shot Show.  Going to take my .25 Can Gun or the .30 along with a few others.  Both are Cothran PowerHouse equipped.

Joe
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Prouzy

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Re: Don cothran 308
« Reply #4 on: November 19, 2016, 04:24:42 AM »
Thats is a gorgeous rifle, congratulation! Great cal to shoot!

Extreme .457

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Re: Don cothran 308
« Reply #5 on: November 19, 2016, 04:27:08 AM »
    The .308 is SWEET!!! I have 2 guns in that caliber! I have shot small groups with great accuracy I love that cal.

Best of luck Brother Man

Alan

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Re: Don cothran 308
« Reply #6 on: November 19, 2016, 06:54:12 AM »
Joe, a friend of mine who lives in Anton, CO, tells me feral pigs are invading southeast Colorado in Baca county. I can't imagine where, as there isn't all that much cover as I recall. If that's true, they're fair game with a pellet rifle.
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rsterne

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Re: Don cothran 308
« Reply #7 on: November 19, 2016, 08:27:10 AM »
My limited experience with the Cothran valve is that you want to find the "tipping point" as you call it, below which the velocity tanks.... and operate just ABOVE that point in terms of preload.... If you try and operate right on the spot where the velocity starts to drop, or below that, I find the velocity can be inconsistent, and any change in bullet weight or fit, or slight "sticktion" in the hammer, can result in those 800 fps shots becoming 400 fps in a heartbeat.... I have found that the best efficiency, in terms of FPE/CI, occurs just above the point where the drop occurs.... You are absolutely correct that increasing the preload past that point gradually uses more and more air with no benefit, however.... Pressure is the primary velocity control with the Cothran valve....

Bob
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grumpy

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Re: Don cothran 308
« Reply #8 on: November 19, 2016, 11:39:36 AM »
Can we have some bigger pics ?
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oneshot61

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Re: Don cothran 308
« Reply #9 on: November 19, 2016, 01:25:56 PM »
Hey guys.... well the wind is howling here in Alabama. We have a cold front coming in tonight so no shooting today. Maybe tomorrow if the weather cooperates.
 Good luck Joe on your Texas hunt! Sounds like a blast and plenty of game to take with your rifles. I saw your build write up on your .25, man that's an awesome gun! Looks like they would at least let you take hogs in your state. They will be glad to let you soon enough. Those things breed like rats and take everything in their path.
 Chris, Chacho,...thanks guys! Been watching your threads on your 308's,.. made me want one all the more. With the tj barrel, I'm sure it will be accurate and I'm jonesing to get some shots on paper.
 Mr. Sterne.. I saw your post on the double disco as I was getting a few shots out of mine. Your post is spot on with this valve. Man your double makes some nice power and I'm looking forward to see what it does in .25 for you. I'm having a .257 breech and barrel made for this one also and I think it will make a great coyote gun for my neck of the woods. I don't get many long shots here but the speed and energy should make for a great combination against a coyotes reflexes.
  I may try a sorbithane washer in front of this valve just for a test run sort of the way Mr. Lloyd did, just to see the results. The sorbithane works well with an adjuster as it is flexible and will compact a small amount with a harder hit, lending itself to allow a shallow or deeper valve stroke depending on the tune. May not work, but its worth a try and will only take a few minutes to find out.  That's half the fun... right?:0-
  Ill mod the first post and insert some medium pictures. Those are small as I didn't know if they would post.
 

Monkeydad1969

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Re: Don cothran 308
« Reply #10 on: November 19, 2016, 07:10:13 PM »
Joe, a friend of mine who lives in Anton, CO, tells me feral pigs are invading southeast Colorado in Baca county. I can't imagine where, as there isn't all that much cover as I recall. If that's true, they're fair game with a pellet rifle.

Nice, I'll look into it and let you know for sure.

Joe
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Monkeydad1969

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Re: Don cothran 308
« Reply #11 on: November 19, 2016, 07:11:19 PM »
Me and Chacho will def kill some goats and hawgs in his neck of the woods.

Joe
« Last Edit: November 19, 2016, 09:33:51 PM by Monkeydad1969 »
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grumpy

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Re: Don cothran 308
« Reply #12 on: November 20, 2016, 05:17:24 AM »
Much better sir. Looks like a beauty. Had several Chavka stocks. Miss every one of them.
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oneshot61

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Re: Don cothran 308
« Reply #13 on: November 28, 2016, 12:29:54 PM »
I had a few minutes to shoot so I ran down to the range. They are starting to log off some of the back area so I only had a few minutes. I don't have a designated scope in yet for the 308 so I put on the open reticle that I used on the .25. Left my targets, chrony at the house. :(. 50 yards, open reticle. 5 shots showing, top three and one below it are on one fill. Had to reuse a target, not what I like to do but, improvising. Can cover those with a quarter. Cant wait till my new scope arrives.., ill stretch out to 75-100 yards. Just not possible for me past 50 yards with the open sight to try and get better groups.
 The bullet is the 31-118A accurate molds bullet with hollow point. 110 grains

Dairyboy

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Re: Don cothran 308
« Reply #14 on: November 28, 2016, 01:12:45 PM »
Love the look of that gun! Looks like it's a shooter as well!
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