Thursday, March 27, 2003

I've been busy with other things, like shooting!

One of the products I've been working on is the Thompson Center Contender Custom Shop .25-35 21" barrel (standard taper profile) with Weaver mount and Swift 1.5-4.5x scope.

I acquired from some person who will remain un-named, approximately 250 cases of which 55 cases were reformed .30-30. All were supposed to be "once fired". They were not. Also, it seemed that they had been fired in an assortment of chambers. The end result is that even after the standard case preparation (polish, lube, resize/deprime, trim, chamfer, clean primer pockets) there was still some difference in case neck tension. This seems to differ based on manufacture and date of manufacture (based on headstamps).

Still, even with mixed brass, groups were acceptable if not at all impressive, running in the 1½-3½ inch range with like brass grouping in tight 1-1½ "sub-groups". Unfortunately, differing bullet weights do not shoot to anything like the same POI, differing by as much as 10"! Also unfortunate, my scope does not have the range of adjustment required to make it usable with the desired range of bullets.

What range of bullets am I talking about? Well, first I had zeroed with the Winchester factory load which features the 117 grain "RN" bullet (actually a flat point). This load moves out at about 2200 fps from my barrel. I was pretty pleased with this load. It was accurate, I was able to zero quickly and the recoil and muzzle blast was pretty mild, even with the 21" barrel and 6 pound weight of my carbine with Rynite stock. I then tried the Sellier and Bellot (S&B) 6.5x52mmR load which features a FP jacketed bullet of the same 117 grain weight and a velocity of 2008 fps. That it is a mild load goes without saying. I'm sure it would be effective on smallish deer in found in some parts of the country, but on our local whitetails I'd want to get closer AND I wouldn't feel comfortable in stretching the range given the trajectories of these "slow" loads.

So, I decided I create an effective coyote load (which has proven impractical) of the 75 gr. Hornady VMAX, 34 gr. of Hogdon's BL(C)2, CCI200 and a factory .25-35 case. Velocities are supposed to be high and they are. Averaging 2837 fps, I sure the spread (from 2937 to 2766 fps) being due to the aforementioned varying case neck tension. Still it grouped fairly well and "sub-groups" of 1-1½" gave hints of great promise for this load. Unfortunately... yes, there is a "but"... groups were a full 10" higher on the target than the Winchester factory POA... at 50 yards. This was unacceptable and the scope's range of adjustment was insufficient to adjust the bullet strike to the proper place on the target.

So, the base was shimmed and scope remounted. That did not make enough difference, bringing the group only 3" lower. Doubling the shim thickness (to the limit of my personal comfort zone with this modification) predictably only lowered the group another 3", still a good 4" above the POA. Also, factory loads would have required equally radical sight adjustment. I decided I just did not want to mess with this further.

Now, I will be trying the Hornady 117 gr. RN and the Remington 86 gr. FP (for the .25-20). I'll push the former at max velocities (for this case) in new factory brass and load the latter bullet to approximate the .25-20 velocities it was built for. Approximate because I will adjust the velocities so that the sights will not have to be changed in order to use both loads. If this works out I'll be very happy with this light and light recoiling rifle. Additionally, it will clearly do what it was intended to do, provide me with hours of enjoyable shooting in experimentation.

As a side note, I have noticed that better velocities can be achieved with the .257 TCU cartridge. Provided the throat is properly matched to the barrel this would make it better for those wanting to achieve top velocities in the Contender with the .25 caliber bullets. Another alternative is a custom barrel for one of the improved forms of the .25-35 such as Francis Sell's Tomcat, the .25 Bullberry or slightly different .25 Bullberry Improved.

No comments: