.45ACP barrel length?

[Murmur]

The 1 1/2" 45/70 is listed in Cartridges of the world as the 45 Silhouette. Could be interesting if you wanted to sling some 500gr bullets down range.
I've just found out that 45 cal is the largest to do safely on the Contender action. Which brings me back to using the 45ACP if I want to use factory ammo alreadly subsonic or the 44 Magnum or 45 Colt if handloading. I've read about good results of the later two with bullets in the 300gr range. Question is what would be the correct twist rate to use to accurately pitch 300gr 44 or 45 cal bullets at subsonic speeds? I think the norm for the 44 mag is 1-20 so maybe a 1-16 might improve things.

[d-mon]

The 45/70 shortened down is a good idea for the contender.

I am not sure but can one of you confirm the base diametre of the .458 socom? I thaught it was the same as a 7.62x39 and not the 308.
The 308 version has another name I believe.
I am not sure that the bolt head of an m-16/ar-15 can be opened to accept a .308 diametre case, that why the socom base is designed smaller.

Regarding the 44 mag with 300gr bullets, I do not think it will work in a barrel with a 1 in 16 twist for the following reason: The 1 in 16" is what is used in 44 special, which in turn uses a much shorter and lighter bullet(200-210 gr) launched at subsonic velocities.
I have a program somewhere to caculate the proper required twist, but I haven't any of the Hornady 300gr on hand.
I would guess that 1 in 12 or 13 should work just fine.
ND

[Bigfoot]

I've never been on a hog hunt so I don't know if a standard .45ACP would be enough. I know that a Marlin 45 Carbine will handle +P and .45 Super ammo with a stiffer Wolfe recoil spring, I'm hoping the Hi-Point will also. The .45 Super with 255 grain hard cast bullets should be enough, but if not look into the .460 Rowland it's about even with than the 45 LC. Load data is pretty scarce but here are some 260 grain loads from a handgun, add a couple hundred FPS for a carbine length barrel. Make sure to click the load data at the bottom. http://www.realguns.com/archives/106.htm

Here's a 1911 Colt carbine conversion for it. http://www.mechtechsys.com/index.html

I ran the Rowlands 1:16 twist into an online twist calculator and it said it should stabilise really long bullets. I'm not sure that I trust that calculator, it might not be accurate at handgun velocities. http://www.shortmags.org/shortmags/r...stRateCalc.asp Remember that the longer barrel will stabilise a bullet better than a short handgun barrel with the same twist.

Alan, what was the velocity of that 250 grain Speer SWC and the range of the deer? Nice performance.

[Murmur]

Theres the heap of info at this link http://www.teppojutsu.com/458.htm
Makes me think that the 1 1/2" 45/70 could be fun. The case capacity is looks close to the socom, cases are easy to get and will suit the contender. The above web site lists that a 1-14 twist will handle 500-600gr bullets at sub speeds even with a short barrel. Anybody have a link to a twist rate calculator to confirm what barrel twist would be required if I went down the 1 1/2" 45/70 route with 500-600gr bullets at sub speeds?

[d-mon]

I will try to put my hand on a very good one i have somewhere on my computer.
Far better than the greenhill formula.

ND

[tp555]

The 458 socom has the same head size as the 308 or base if you want to call it
that.The ar bolt can be machined to .510" which is about the max.Tromix made and sold ar's in 50 AE which has the .510 dia bolt faces. It required a special extractor. So does the socom. Machining the ar bolt to .510 leaves a paper thin
amount of material from the original round part. The bolt held up to the pressures and worked.The biggest cal in an ar15 is the 510 phantom. It is 510 cal same blank as 50bmg. The bolt face is .530".to do this they use olympic
arms wssm parts.The bolt.bolt carrier,upper and barrel extension are redesigned
and bigger then the standard ar15 parts. I had the opportunity to examine a wssm barrel recently.regards.

[d-mon]

Hello tp555,
I guess I was wrong about the rim dimension. Sorry for that.

Murmur, I have a twist calculator, unfortunatly, it's creator does not which me to give it away on the web.

If you can provide me with the following info, I would be glad to calculate the right twist for your bullet.
I would need:
1 the bullet diametre in inches
2 the total bullet lenght in inches
3 the nose lenght in inches
4 meplat diametre in inches
5 Nose shape (tangent, secant, conical)
6 the material of your bullet :jacketed or lead

This is for a flat base bullet, the program needs more info for a boattail.

ND

[pug]

Whats up fellows. Didn't realize it had been so long since I last visited here. I see you are on one of my favorite subjects again but don't forget one of the oldest rules about the sound level of subsonic ammo. The sound pressure level is directly proportional to the cross sectional area of the bullet or in other words .45 is one of the hardest ones to quiet and .17 is one of the easiest. Fast burning powder in a long barrel will get you started and most go middle road with 9mm or 308 to get the quietest with the most energy delivered to the target. One of the cheapest to try is an old sks with the gas piston removed shooting 308 150gr and up with a fast pistol powder. Always check for a clear bore after each shot until you are sure of the load and wear eye protection (the sks gas tube vents to the sides and rear unless packed or plugged).

[Bigfoot]

Didn't know that Pug. That explains why the long barreled 45ACP is louder than I expected. How much quieter would a 9mm 147 grain subsonic load be in the same length barrel?

Originally Posted by d-mon

If you can provide me with the following info, I would be glad to calculate the right twist for your bullet.
I would need:
1 the bullet diametre in inches
2 the total bullet lenght in inches
3 the nose lenght in inches
4 meplat diametre in inches
5 Nose shape (tangent, secant, conical)
6 the material of your bullet :jacketed or lead

This is for a flat base bullet, the program needs more info for a boattail.

ND

Now THAT'S a calculator that I can trust, very nice. My software can provide the length of most factory bullets, tell me the bullet and I'll post the length. The meplat, nose length and tangent I can't help with.

[Wrangler]

If the sks is .311 what does the difference of .012 for the .308 bullet do to mess up accuracy since the bore is for the larger diameter bullet?