I have a #3 in 7mm-08 that I am considering rebarreling/reboring/rechambering to a cast bullet cartridge for off-hand paper punching at 100 and 200 yards.
I'd like something accurate enough to compete with, cast bullets only. Breech seating is live option. (smokeless powder for me, but maybe not for your answers)
What would y'all pick - caliber, bullet and twist?
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A tighter chambered 30-30 with a “real” throat is hard to beat.Most 30-30's have a transition from end of case to rifling of about zero.Really i think its 15 deg or something.I have a Savage 99 in 30-30 with a tighter chamber and a .0050 x 1.5” leade and it is a wonderful thing often shooting sub MOA.It seems to forget its a lever gun.
CBA's Region 7 director Bill Anderson built up a #1 in 308/307 Winchester.It has the cut for the rim and can use either case..(He also has a twin in 358/356)He uses the rimmed 307's for cast loads and standard .308 for jacketed bullet loadings.Ruger #1 extractors are pretty forgiving and the system works slick.The chamber was cut with a 7-08 reamer with a 308 pilot and the neck was then cut seperate with a 30-40 Krag reamer to give a nice tight neck condition without being too tight.
George
"if it was easy we'd let women do it" don't tell my wife I said that!
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TRK,
The 7-08 ought to shoot good for off-hand matches. The CBA off-hand program is 100yds, so most people shoot mild loads, no recoil easy to shoot and not flinch. Breech seating is not necessary for an off-hand rifle.
A rifle I plan on dedication to off-hand shooting, I angle the rifle so the rifle butt rest into the ball of my shoulder, better fit with a factory stocked rifle. Then I rotate the scope to lever the cross hairs. Works better for me................Dan
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What powders would y'all use with such large case capacities? Say for .30-30 or 7mm-08?
Obviously a question of %fill - accuracy - variation.
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For 100yd you could use Ed's favorite of 11-12grs of Red Dot with a PBB, or like linoww uses about 14-16gr of Al2400. The 7mm would be a little less. You don't need to fill the case with powder for accurate shooting at 100yds off-hand, probably 1” groups.
If you're bent on converting the rifle, a 32-20 I think would be a good off-hand cartridge. Stay with a 165gr bullet and you'd be able to get plenty of velocity if you want to still shoot at 200yd. OR, stay with the same extractor, a little easier conversion and make it a 30BR if you want to go to the work of making the brass. Probably a 1-12” twist shooting a 165gr range CB, with the RCBS 165 or 180 SIL coming to mind.
I consider breech seating to be more work while you're trying to concentrate of your shooting. A good match chamber CB loaded cartridge will shoot practically as good for off-hand shooting, or for BR shooting really..........Dan
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If you want a rimless case of small capacity for which brass and ammo are common, the 7.62x39 works great. The SAAMI or Lapua style chamber attached is fine. YOU DO NOT want the AK or SKS style chamber.
Use an ordinary .30 cal. barrel with either 12” or 14” twist, and 20 grs. of RL-7 with just about any match quality 150-180-gr. cast bullet. Easy to get to shoot well.
73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia
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Dan - thanks, that's where I'll start with what I've got.
Ed - you read my mind. I have a Baical in 7.62x39 - you don't have to tell me twice to avoid their style of chambering! Thanks also for the drawing - well worth my time examining!
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ED: Isn't the 7.62x39 kinda sort in the neck for cast? I would be inclined to blow the shoulder out a bit and straighten up the case but move the shoulder back 2-3mm.
Any thoughts?
Cheers from New Zealand
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If I go 30 cal. I'm inclided to do a standard .300/.308 bore/groove for availability (in my collection and elsewhere) of moulds.
That brings me to .30 car; .30-20; and 7.62x39 (to minimize case capacity).
Am I wrong in thinking that the most critical thing then is seating the bullet into a lightly engraving throat for most of the bullet diameter? That would leave a small portion of the base in the neck.
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In .30-30 size cases 4227 works well as does AA #9 for top notch accuracy in the 1300 fps to 1500 fps range. Neither requie fillers. Some single shot guys are now using VV N120 and are impressed.
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ED: Isn't the 7.62x39 kinda sort in the neck for cast? I would be inclined to blow the shoulder out a bit and straighten up the case but move the shoulder back 2-3mm.
Any thoughts?
For target rifle I've always had best results seating the bullet out and letting the throat align and guide the bullet, rather than having the sloppy neck and chamber tolerances do it. If you require sturdy fixed ammunition for a hunting rifle, that is quite different, then you want a longer neck to preclude the bullet base from poking below the neck and into the powder space.
A short neck is no problem if the throat is long enough for the bullet to fit when seated so its base is contained to the base of the neck, short or long, it doesn't care.
I seat out 180 or 200-gr. bullets in the 7.62x39 for single-shot, boltgun use all the time. But for semi-auto in the SKS and magazine feeding the 155-162 gr. bullets I designed for the cartridge are as heavy as “works."
73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia
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I have a BSA Marini action Australian cadet rifle I rebarreled with a Shilen barrel to 30-30 AI & it does a fantastic job with an RCBS 165 gr Silhouette mold. I use 20 gr of 2400 for a mv of around 1,850 fps & it shoots way tighter than I can hold offhand!
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I have a BSA Marini action Australian cadet rifle I rebarreled with a Shilen barrel to 30-30 AI & it does a fantastic job with an RCBS 165 gr Silhouette mold. I use 20 gr of 2400 for a mv of around 1,850 fps & it shoots way tighter than I can hold offhand!
LH -
I also have a BSA Martini action (cadet) rebarreled in .30-30. Do you have any issues with the AI flavor and chambering a round with a bullet seated long?
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...
What does the geometry of the chamber/throat look like? Long throat to hold the bullet closely and pressed into the start of the rifling?
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Hmmm. So how far out-to-lunch would I be to set-back and rechamber the existing 7mm barrel to a 7mm-20? (between a .25-20 and a .32-20)
Cost - minimal Objective - 'pistol' cartridge (engergy/velocity) in a rifle. Aiming at 1200-1800 fps with 1” 100yd accuracy with cast bullets.
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Hmmm. So how far out-to-lunch would I be to set-back and rechamber the existing 7mm barrel to a 7mm-20? (between a .25-20 and a .32-20)
TRK,
Two fairly standardized cartridges come to mind, the 7mmTCU and the 7mmBR; reamers, sizing and loading dies readily available. The TCU is made from 223 Win brass, you'd have to cut a lot of barrel off to do that so it probably wouldn't work. Same as a wildcat 7mm-20 or something would have to cut too much off the chamber end.
The 7mmBR might work if you have enough barrel diameter at the breech end. I doubt you'd gain much over the now 7mm-08, except to have a fresh and correct throat for the bullet you want to shoot. You should be able to achieve what you want (below statement) with what you have now, unless the barrel is in really poor condition......................Dan
Cost - minimal
Objective - 'pistol' cartridge (engergy/velocity) in a rifle. Aiming at 1200-1800 fps with 1” 100yd accuracy with cast bullets.
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Dan - thanks, good points. I'll measure and calculate. The barrel is round for 6 or 8” and then straight octagonal - it NEEDS to be shorter for off-hand (weight) and the crown is perfect, bore is perfect (does under 1/2” groupa at 100yds jacketed bullets with ease. 7tcu is to my liking - SMALLish capacity, straight walls, abrupt but small shoulder.
As you've said, the throat work will be one of the major benefits.
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Keep us updated if you go forward with this TRK, it should prove to be an interesting project!
In fact this would be an exceptional project for the Special Projects section of the forum..
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I certainly will, Jeff. Looking for a 'smith now to do it. It has a 26” bbl and enough (6-6-1/2") that's cylindrical that will allow the shortening - fast rate of twist too.
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What does the geometry of the chamber/throat look like? Long throat to hold the bullet closely and pressed into the start of the rifling?
Look at the print posted.
73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia
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I figured that it was likely that, but didn't want to ASSUME. :DWhat does the geometry of the chamber/throat look like? Long throat to hold the bullet closely and pressed into the start of the rifling?
Look at the print posted.
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Bryan Austin
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fc60
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Ed Harris
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Bud Hyett
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linoww
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DanLH
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Aaron
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RicinYakima
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Wilderness
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9.3X62AL
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