30 BR Rail Gun, Redux

jackie schmidt

jackie schmidt

New member
First, let me say that doing something like this is not easy. I am trying to see if I can achieve competitive accuracy in the Unlimited 10-shot Format with my Rail Gun chambered in 30BR. For those that are not familiar with the concept, that means having the capability to shoot 10-shot groups at a sub .200 level.

I have not reached that goal yet.

What I did yesterday was spend 11 hours at Tomball trying quite a few different combos, shooting close to 160 rounds in the proccess.

I tried velocities from 2850 to 3150. I tried seating depths from .010 off jump to a .030 in jam.

Anything over 3050 fps gets VERY eratic in the 95 degree temperature. By eratic, I mean it will pop a shot as much as .400 off the group.

The seating depth seems to be optimized at .010 into the lands. Thw way I find that is by seating a bullet untill I finall see a faint mark with a 10x loop, and then going in about .008 more.

The best charge of 4198 seems to be what shoots in all of my 30 BR's, enough to push it an average 2990 to 3010 fps. In this 24 inch barrel, that turns out to be 33.7 grns with the 112 BIB.

In the end, I wound up right back where I was at Seymour two weeks ago. Maybe I need to admitt that I was not on my game as well as I could have been at Seymour. I could have finished as high as 4th at 200 yards, that is not the Rifle's fault.

Yesterday, I could not shoot a 10 shot "one". I did, however, (when I got the thing working as good as I can), shoot four good solid "twos", on the clock, under match conditions. They measured, (with an official measuring tool), .232, .251, .258, and .238.

Each group had at least eight shots under that magic .200 level, but one or two shots managed to "ruin" the group, usually in the verticle.

But, keep in mind, every shot would have been an "X" if I had been shooting score.

Shooting 10-shot groups is not easy, especially at a range like Tomball. I add the challenge of putting myself on the clock so that I do not fool myself into reaching conclusions that will not play out where it counts, in the Competitive Arena.

I was going to go back today and shoot at 200 yards. But I had a tiring week on a job down in Palacios, and its 100 degress out. I think I am going to sit here and watch the NASCAR Race, and think about chamberring up the two new gain twist Bartliens that were waiting on me when I got back to the Shop this week.

But that is another subject..........jackie
 
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Jackie,

Considering that an official screamer 10 shot 100 yard group is .199", you shot four groups that weren't much over that and if you could shoot one more "two" you'd have a pretty darn competitive agg for unlimited anywhere in the country! Perhaps you're upset that one or two shots popped out of the group, but they can do that real easy with a ppc as well. But if they pop out to a near screamer group though, I wouldn't be too upset.
 
GoodGrouper

I really cannot look at it that way. Although a .199 is what we call a "screamer", they are not that uncommon. Heck, at Seymour, there were probably 10+ shot over the course of the eight 10-shot groups.


Compare that to how many 5-shot "zeros" you see in Registered Competition. Heck, I know shooters who have won their share of aggs who have never shot a "zero" in Competition.

I had a couple of "spotters" helping me yesterday, Vic Smith and Gary Walters. They were watching the conditions as I was shooting, and the consensus was the conditions had nothing to do with the shots that added substantially to the groups. When you are able to catch a really nice quatering left to right at only 5 mph, and a shot just goes straight down, that ain't condition. That is in the combination.

Don't get me wrong. I did ruin at least one group by flat out missing a push. I was shooting that "dreaded straight accross", and turned a mid two into a mid three with one shot. I got really aggravated at that, felt like I just wasted 10 bullets, primers, and 330+ grns of powder.

I define a perfectly tuned, (as in capable), combination as one where the ONLY thing that will cause one bullet to take a different path as the one before is the conditions you are shooting into. I am not quite there yet with this set-up.........jackie
 
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Jackie...a recomendation...call Ronnie Cheek and get some 118 grn bullets...the 17 twist is better suited to them...
 
Cheeks

He is supposed to be sending me some. I think they are made on a 1 inch jacket and feature a nine ogive.

Hard to beat the BIB, though.........jackie
 
I have shot both (brands) and can tell you that there is a difference..:)
We have a local shooter that changed from 115 grn Eubers to Cheek 118 and he has been beating us like a rented mule with that bullet and he is using a Krieger 17 twist with H4198...I just wish I hadn't recommended the 118 Cheek...it has delt me nothing but misery...:eek:
 
eww

I shot 112 Cheeks at one of the 100's at The Bluebonnet, did quite well. I shot the 112 BIB'S the next day.

In my Sporter and HV, I Have to add about 1/2 grn of powder to get the cheeks to agg the same as the BIB. I figure tyhis is because the Cheek's measure about .0003 smaller on the gas ring, and are exactly .308 on the body just forward, and the BIB will measure about .3082 at the same spot..............jackie
 
Jackie, some time ago Wilbur & I both built .30 BR rail guns -- I forget just when, Wilbur is younger & may remember the year. Far as that goes, almost all my experience with the .30 BR is in group shooting.

Anyway, we found what you're finding, that the hotter loads always seemed to pop one out. That was with different powders, though. The build quality of Wilbur's gun may have been suspect, It was sort of a committee effort. I donated a barrel, Randy some bullets, and I-don't-remember did the gunsmithing.

Mine was built by Tooley, so if anything was suspect, it was only the barrel (& maybe the shooter). But it shot well. I was leading the 10-shot unlimited for 3-4 matches at the 300 yard SER regional at Charlotte with it that year, until I tipped the powder can a bit much (IMR 4227 gets too hot in a hurry) & had to start pounding the bolt open -- and popping a shot or two.

I'd echo trying the 118s. My experience is with the 10-ogive BIBs, but a 9-ogive Cheek should be similar. Might be better, might not, but surely worth a try.

I'd also waste a few cases and turn the necks .003 undersize, then use a LOT of neck tension. Not a guarantee, but worth a try. This is Al Nyhus' experience, and also fits with some of the bigger .30s & bigger BIBs we are using at long range -- Fewer "where the heck did that come from" shots.
 
Charles

Right now, I am using exactly .002 overall clearance with the BIB, it would be about ..0025 with the Cheeks.

As for tension, I made a die that is solid, it uses a .325 "bushing", that gives a pretty good neck tension.

One thing I notice, even though the brass just falls out of the chamber, (this is a light pressure load compared to my usual practice), the neck tension seems noticably lighter after just a few firings, although the cases measure tyhe same out of the die.

Old cases seem to shoot just bas well as the brand new ones, though.

Charles, did you and Wilbur ever shoot consistant "mid twos" in the 10-shot format with your set-up.???.......jackie
 
Jackie,

I don't think so. This was about 10 years ago, as I remember. Wilbur's gun was never competitive. He gave one final try with some bullets Jef Fowler was starting to make, and it still wouldn't shoot as well as his PPC. For some reason, I changed barrels to a PPC -- but I couldn't get it to shoot as well as the .30BR . I was spending more of my dollars and time at 1,000 yards & set the rail aside.

You are blessed in the Gulf region -- even 10 years ago, many of our Southeastern regional matches were 5-shots in unlimited. Some of us complained, but the various match director's answer was always that people wouldn't shoot 10-shot unlimited.

Based on the performance of the rail gun, I did build a .30BR HV, which I still use today when I shoot point-blank. I think I've won more with it than the PPC's (all group shooting).

My home range is holding the SER unlimited this fall. I think I'll make a new top for my rail, and chamber it in .30 BR. Probably I'll learn more from you that you'll learn from me.
 
When I used the BIB 112 bullets in my 17 twist...I had unexplained dropped shots...I quit shooting it...I am waiting for the 118 grn Cheecks for my 17 twist...but my 18 (Krieger) twist always shot the 112 grain bullets better, but the Cheeks worked a little better that the BIB...
I am convinced the best combination would be a 19 twist cut rifle barrel and 112 grain bullets...
I just haven't had the success with my 17 twist barrel that I have with the 18twist...and I feel there is more accuracy to be gained with a 19 twist and 112 grain bullets...
I hope to find out later this year...when my stimulus money arrives..:rolleyes:
 
Great

I have a barrel that cost me damned near $400, plus my time to chamber it up, plus 3000 112 grn bullets that would work better in a 1-18, not to mention range time, primers, powder, etc.

Got any more good news. The evening is still young.:D...........jackie
 
Jackie,

It may be a dumbass thought, but I remember something from an interview about .30s in long range needing more clearance to shoot their best. In fact, I know one NBRSA record holder that told me that his neck clearance is between .002 and .003. for his 6PPCs. It would only take re-turning a few cases and a different bushing to try this. Of course if you have made a one-piece die, then it gets more complicated.

Boyd
 
eww1350 said:
When I used the BIB 112 bullets in my 17 twist...I had unexplained dropped shots...I quit shooting it...I am waiting for the 118 grn Cheecks for my 17 twist...but my 18 (Krieger) twist always shot the 112 grain bullets better, but the Cheeks worked a little better that the BIB...
I am convinced the best combination would be a 19 twist cut rifle barrel and 112 grain bullets...
I just haven't had the success with my 17 twist barrel that I have with the 18twist...and I feel there is more accuracy to be gained with a 19 twist and 112 grain bullets...
I hope to find out later this year...when my stimulus money arrives..:rolleyes:
Click to expand...
While I don't doubt your experience with a particular 17-twist barrel and the 112s, I don't think it is a principle. The equivalent with a PPC would be going from 14 twist to 13.25 twist. Shouldn't cause shots to pop out. You can find a ragged edge when *reducing* the rate of twist (reducing Sg under say, 1.2), which is predictable in both ballistic theory any experience. Going the other way, nothing in ballistic theory or often-repeated experience predicts this with a slight *increase* in Sg. Theoretically, shot dispersion goes up, but this reduction in twist rate is too small for it to be measurable on target.

So much for the theory. I'd explain you results with the old "some barrels prefer some bullets." Better to admit we don't know some things than to ascribe a reason which later turns out to be wrong.
 
I think you should try some H322. It works for me, especially in hot weather.
 
Charles...I agree on paper there should be no difference between a 112 and a 118 grain bullet accuracy in the 17 twist...but watching the equipment list of the winners in the VFS matches and it's rare to see the 112 grain bullet...
I have put about 5,000 rounds thru my 2 30BRs and I have shot 110 Bergers, 112 BIBs, 112 Cheeks, 115 Eubers, 118 Knights, 118 Cheeks...to name a few..
and I have found that the barrel/twist has a preference...and we have several local shooters that have 30BRs and there is a notible difference in accuracy when a certain bullet and twist combo is used...I am see something in the way my 12 pound 18 twist 30BR shoots with 112 Cheeks that I shows me if I slowed down the tist a little more it would really come alive..
 
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