I was given a Douglas XX 30 cal 1-14 twist barrel blank. This is kind of an unusual twist for 30 cal. I had ideas of rebarreling my 788 Rem 30-30, using this barrel. I had been using the 311291 previously in the factory barrel, which I believe is 1-10 twist. How does the 1-14 twist rate in actual use for mid weight cast bullets? Greenhill's formula claims 178gr max weight. Also, I was given a box of reamers, which included a 30 Herett rougher and finisher. In a rifle, is there any advantage of this over the 30-30.
30 cal 1 - 14 twist barrel
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- Last Post 17 September 2014
Regardless of what the magazine writers tell you, the only advantage of the 30 Herrett is that it is shorter with less powder capacity. The 1/14 twist was all the rage for shooting the jacketed 130 HP bullets at 3200 f/s in Hunter Benchrest about 25 years ago. FWIW, Ric
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"G”
A 14 twist may be marginal for that bullet. To find out whether it will be stable go to this web site and use the “bullet drag and twist” application. It is very accurate and much more sophisticated than the Greenhill one.
JBM ballistics is the site. http://www.jbmballistics.com/ballistics/calculators/calculators.shtml It's free to use.
I have used it many times in designing guns and it is always accurate. If it says it's marginal, it will be marginal and may not stabilize the bullet on a cold day. I know from first hand experience. You want your stability factor to be 1.5 to 2.5 to be safe. You cannot “overstabilize” a bullet but you can sure over spin it and make any out of balance of the bullet worse by spinning it faster than needed. I always used a 12 twist to be safe myself.
Don't fool yourself and think that shooting it faster will raise the stability factor much. It won't. It has a small effect. Be conservative. Play with the program and you will see what the result really is by increasing velocity and looking at stability. Then you will see what I mean when I say that.
You will have to estimate the nose radius of the bullet for input into the program. I did it by drawing some nose shapes with a compass scaled to 30 cal. and comparing the bullet for the best fit. You're probably going to be around a 2 to 3 caliber nose radius. Also make sure you tell the program that you have a lead bullet with no boat tail. The density of the bullet makes a difference.
Also note that many inputs are expressed in calibers. So you will have to convert from decimals. It's a little work but worth it to make sure your gun will stabilize the intended bullet.
I think this will answer your question. If you use this program, let us know the predicted results.
If you get stuck on something feel free to PM me and I'll see if I can help.
Tom Gray
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Tom, your URL isn't working.
I fooled around and http://www.jbmballistics.com/index.shtml works fine.
Mike
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I've been shooting numerous different cast bullets, including the 311291 in a 14” twist barrel. It is a Palma rifle in .308W with a 27.5” barrel. It stabilizes the 311291 just fine down in the 1800+ fps range. I might add it also stabilizes the 311299 just fine but at a bit higher velocity. Velocity does increase the stabilization factor as, with a given twist, increased velocity increases RPM. Also consider the 32 SPL with it's 170 gr bullet which has a 16” twist. Those bullets are stabilized just fine.
I would whole heartily suggest putting that 14” twist barrel on that M788 and chambering in 30-30. You might also want to keep the barrel as long as practical (I'd favor a minimum 26” barrel). With the 26” barrel with a 14” twist the 311291 loaded over LeveRevolution Powder should be an excellent performer. For best accuracy a 311466 over 4759 or H4895 should prove excellent.
LMG
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I own a few 14 twists and if I were you I'd get a bullet about 1.020 long , the RCBS 165 Sil. is a good one although there's others in that length range. Any bullet under 1.050 should work well if it fits the throat. If it doesn't fit get the barrel throated so it does. 14 twists perform pretty well as Larry Rickertsen and other guys that use them can tell you.
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the 30 Herett has a very short neck. Just something to think about. I like the 30-30 much better for cast bullets.
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GBertolet
I would also recommend chambering to 30-30 for use with the 311291 or most any other cast bullet in a rifle with the 14” twist. The increased case capacity for use with slower burning powders over the 30 H and the longer neck of the 30-30 will be definite advantages with heavier cast bullets in the 150 - 180 gr grange. I suggest also searching for a 311466 mould and you will find it probably will perform excellently in regards to accuracy and velocity out of M788 with a 14” twist.
LMG
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I got the barrel all set up, and now I am waiting for the custom 30-30 reamer. Perfect for cast bullets, I hope. It has a shortened throat with a 1.5 degree leade. It's considered custom, so it could be 5 or 6 months wait. Too bad. I had a hard time deceiding on what contour to make the 24” barrel. I finally made it for the final 10 inches, .810 straight to the muzzle. The finished unchambered barrel weighs 4 lbs. The factory barrel weighs 2.55 lbs. After throwing the new barrel and all the parts on the scale, I found the finished rifle with scope, is going to be around 9.75 lbs . I sort of like heavy rifles for offhand shooting, but fear this may be too much. The last rifle I did, I wished was heavier after it was done, so this time I think I went overboard. I guess I will see when it's finished, and I try it out. If so, I can always put the barrel back in the lathe. The original stock is beat up pretty bad, and just plain ugly, so I was eyeing up a Boyd's laminate stock for the 788 also. They look pretty nice, and they are less than $100.
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hi G; by shorter throat do you mean a short free bore ? what is the diameter and length of the free bore ? sounds as if you will have a nice setup.
fwiw, ptg makes custom reamers at no extra charge; also i never had to wait over 2 weeks from ordering. a few years back, tho.
ken
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According to the print I was given, the freebore length is .100, and is .3095 in diameter. I did not design this reamer, but rather I selected it as custom reamer design, on file from a previous customer. I corrosponded with this customer, and he was well pleased with it's performance. I also selected a .3005 live pilot to fit my .301 bore diameter barrel. It's a Manson reamer. It's my understanding that all the reamer manufactures are backed up, just like the rest of the shooting sports industries.
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If you haven't already placed the reamer order, call PTG. They've made 5 reamers for me (they're only 5 mi from me) and like Ken said they can usually supply reamers within 2 weeks. I've actually never had to wait 2 weeks for a reamer. Frank
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The reamer was ordered already in the beginning of July. Manson had the design on file that I wanted. I just hope it doesn't take the estimated 5-6 months to get it.
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My reamer came early after only a 2 month wait. It came with a .3005 live pilot which fit the bore perfectly. I got the barrel chambered and installed on the rifle. I had to relieve a good bit of the stock's barrel channel to fit the fat barrel profile. This stock has been beat pretty bad over the years, so a new one is in the works.
Tenative grouping with the 311291 shows some promise. No bullet tipping with the 1-14 twist. Only tried two powders so far, 4198 and 4759. 5 shot group size has been running 1.5 to 2 inches at 100 yards. Not bad, but I should be doing much better than that, as that's what the factory barrel would do. Typically I have 3 shots cutting the same hole and 2 shots strung vertically 1 to 1.5 inches above. Can't figure out so far what is causing this. 15gr 4759 has worked the best so far. I tried a 10 shot group with this load. 6 shots in 3/4 inch and four shots about an inch above that. Maybe this barrel doesn't like the 311291 bullet and should start looking for another mold.
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have you tried to establish an accuracy baseline with developed mj loads ? i would think a 788 with a good barrel, bedding, bullets ... would shoot well under 1 moa.
bedding ... is it pillar plus glass bedded ?
bullets ? nosler ballistic tips are usually very accurate, but also try others.
keep us informed.
ken
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I'd look really hard at the new NOE 310-165-FN. It is designed for that length of case neck. I've been shooting it quite a bit in my 14” twist .308W and it is excellent providing better accuracy than any other bullet.
LMG
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just a thought ... but timney makes a great trigger for the 788 ... i got one on my factory 788 in 223; it shoots close to 1/2 moa ( mj of course ) .. with a light rifle i figger the light trigger is worth 1/2 moa over 10 shots. oh, i use a trigger shoe also.
oh, it brings a tear to my eye when cast bullet shooters ” only ” get 1.5 moa groups ... my 100 yard chipmunks often survive a 5 shot barrage.
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Update: I think the Midway/Caldwell rifle rest I was using was the culprit. It seems to vibrate upon firing. I tried shooting over shot bags filled with sand instead, and the group size shrunk considerably. Final 5 shot group size using 15.0 gr 4759 and 311291, was 4 shots slightly under 1/2", and the 5th shot enlarging the group to 7/8” at 100 yards. The stray shot was likely me, as I was only using a Weaver K4 scope, and my eyes weren't what they used to be.
I did attempt to do a poor man's pillar bedding. I put .025 aluminum spacers under both action screws. Barrel is completely floated, as I can easily run a business card from the forend to the recoil lug. I had previously done a trigger job by replacing the trigger return spring. I'm down to about 2.5 lbs and I am satisfied with that. The rifle is not to be a bench gun, but rather an offhand shooter. The rifle with scope weighs in at 9.5 lbs. I like the heavier rifles.
If I can repeat these results the next time at the range, I will be good!
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Don't overlook the Lyman 311284 . It is very accurate in my 1 in 14 twist bench gun.
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For what it's worth, 10 lb or so isn't really very heavy for an offhand rifle, and less so if you know that for offhand, rifles should be stocked short by 1/2” or a bit more, which makes them feel lighter. Grouch
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