Twist for 150 Accubond?

[edge]

Does anyone know the "Real" twist rate needed for the 30 caliber 150 grain AccuBond?

The conditions would be zero degrees F, sea level and about 30 in Hg.

I am not looking for Greenhill or Miller which do NOT take into account the specific gravity.
( for instance Berger requires a 14 twist but their bullet has more lead which is considerably more dense than the extra copper in the AccuBond with the ballistic tip )

Thanks in advance.

edge.

 

[JD338]

SAAMI spec is 1:12 twist but several rifle makers offer 1:10 twist.

JD338

 

[edge]

SAAMI spec is 1:12 twist but several rifle makers offer 1:10 twist.

JD338

Thank you, and you may be correct.
Down to 30 degrees they shoot excellent in my 1:14 twist...well sub moa.

Down between zero and 10 my accuracy went away, I mean completely away!

I shoot these in a muzzleloader and the reason for the question is am I losing accuracy due to:

too slow of a twist;
sabot integrity;
lose of sabot bullet contact, due to temperature resulting in loss of rotation;
something else.

I don't know the problem, but this would/should be my go to bullet for short and medium range but it has to be consistent!!

edge.

 

[SJB358]

SAAMI spec is 1:12 twist but several rifle makers offer 1:10 twist.

JD338

Thank you, and you may be correct.
Down to 30 degrees they shoot excellent in my 1:14 twist...well sub moa.

Down between zero and 10 my accuracy went away, I mean completely away!

I shoot these in a muzzleloader and the reason for the question is am I losing accuracy due to:

too slow of a twist;
sabot integrity;
lose of sabot bullet contact, due to temperature resulting in loss of rotation;
something else.

I don't know the problem, but this would/should be my go to bullet for short and medium range but it has to be consistent!!

edge.

Can you speed them up? Sometimes speed will help with stability.

 

[FOTIS]

Edge....

Let's work this out,

what is your velocity?

 

[edge]

Edge....

Let's work this out,

what is your velocity?

Depending on which load I use it is somewhere between 3,000 and 3,200 fps.
3k as a minimum is fair and leave me plenty of margin for error.

edge.

 

[Guy Miner]

Let me see if I've got this straight:

You're shooting a muzzle loader, with a .30 cal bullet in a sabot, at 3,000 - 3,200 fps.

Right?

Just wanted to make sure - because I think there's way too many variables there for my conventional .30 cal experience to be of much help. Out of curiosity - what sort of muzzle loader is this? I've been successful while hunting with my muzzle loader, but just loaded a full .50 cal soft-lead bullet to do so. Never saw a sabot for a .30 cal bullet from a typical .50 cal muzzle loader.

Interesting application for sure!

Guy

 

[edge]

Let me see if I've got this straight:

You're shooting a muzzle loader, with a .30 cal bullet in a sabot, at 3,000 - 3,200 fps.

Right?

Just wanted to make sure - because I think there's way too many variables there for my conventional .30 cal experience to be of much help. Out of curiosity - what sort of muzzle loader is this? I've been successful while hunting with my muzzle loader, but just loaded a full .50 cal soft-lead bullet to do so. Never saw a sabot for a .30 cal bullet from a typical .50 cal muzzle loader.

Interesting application for sure!

Guy

I built it myself with a Shilen .458 1:14 twist barrel on a Savage 110 action.
No barrel nut and a 1.24 diameter.

I machine my own sabots.

Since having the problem with the AccuBond I switched to the Custom Comp 8 mm 200 grain bullet under 87.5 grains of smokeless powder.

Here were the Accubonds in their sabots:

edge.

 

[Guy Miner]

Well I'll be darned. Now that's different!

 

[Guy Miner]

For info - the slowest twist .30 cal I used were some 1:13 twist Kriegers for a match rifle. Typically I used the 155 gr Nosler HPBT match bullet, but was also able to properly stabilize the 168's.

A few of my pards are into "hunter benchrest" and use a relatively slow 1:14 twist, but they typically limit themselves to a flat base 125 gr bullet, or lighter.

For a 150, that AccuBond is a fairly long bullet too. Just a thought. My current .308 Win uses a 1:12 twist and has been accurate with 110 - 180 gr bullets.

Guy

 

[IdahoCTD]

I've shot tons of 168's in a .308 with a 14 twist barrel considerably slower than your shooting. So the 150AB's should stabilize no problem. What I think is going on is either your projectile weight with sabot is considerably higher than 150grs or because it's in a sabot the weight is further forward than normal. So your probably marginal on the twist for your particular set up and as it gets colder (and possibly more humid) the air gets more dense and you totally lose stability (your probably losing velocity too). The reason I think that is because if you look at the 190gr Matrix VLD in 7mm they will stabilize in a 9 twist. The reason being is they keep the lead back away from the nose of the bullet. The further the weight is forward the more it acts like a heavier/longer bullet. The sabot is part of the projectile and is probably throwing off conventional wisdom for twist.

The AB's are typically longer than a BT because the jacket is a bit thicker. You might try BT's and see if they do the same thing. You might also try a different 150 like a Hornady or Sierra. They might be short enough to stay stabilized.

 

[edge]

I've shot tons of 168's in a .308 with a 14 twist barrel considerably slower than your shooting. So the 150AB's should stabilize no problem. What I think is going on is either your projectile weight with sabot is considerably higher than 150grs or because it's in a sabot the weight is further forward than normal. So your probably marginal on the twist for your particular set up and as it gets colder (and possibly more humid) the air gets more dense and you totally lose stability (your probably losing velocity too). The reason I think that is because if you look at the 190gr Matrix VLD in 7mm they will stabilize in a 9 twist. The reason being is they keep the lead back away from the nose of the bullet. The further the weight is forward the more it acts like a heavier/longer bullet. The sabot is part of the projectile and is probably throwing off conventional wisdom for twist.

The AB's are typically longer than a BT because the jacket is a bit thicker. You might try BT's and see if they do the same thing. You might also try a different 150 like a Hornady or Sierra. They might be short enough to stay stabilized.

A lot of good stuff to think about

The sabot breaks off as it leaves the muzzle, so the weight of the sabot itself should not be an issue.
The season before I started with the AB I used the 150 SST and it was very accurate.
It seems the more I practice for long range the shorter the distance I end up shooting deer :lol:
At any rate, I shot a buck from about 75 yards.
The deer I shot was headed toward me but his head was turned 90 degrees to his left. The 150 grain bullet hit just left of his right leg which was a little far back at very close to 3000 fps.
The bullet centered a rib, continued through one lung, liver, stomach, intestines, and exited through the ham. Actually the jacket was recover inside the hide next to the ham but the core exited.
Here was the Jacket, I can't argue the penetration, but I wanted more weight retention.

edge.

 

[edge]

I would be remiss if I did not note that the following year I switched to the 150 AB.
Since I fire my load out at the end of each day, one day I shot the AB at a tree from about 30 yards and the impact was easily over 3k fps.
I saw that the bullet exited and was lodged less than 1 inch into a tree a few yards away. I came back a few days later with a cordless sawzaw and cut it out.

Here are pictures of the tree with a can of Goex for size comparison and the bullet from both ends.

edge.

 

[jmad_81]

:shock: Looks good!

 

[IdahoCTD]

The sabot breaking away should not be a issue but your in uncharted territory and could be effecting the bullet prior to release. How far away from the muzzle are the sabots?

BTW your on Doug's message board site aren't you? I've been thinking about building a smokeless but to shoot elk here in Idaho we are limited to short range weapons hunts and .50 cal. I have a Krieger .50 cal 24 twist barrel and can't decide on BP or smokeless. Our normal BP hunt became a draw (and about 16% chance of drawing) but there are typically more chances to hunt BP over smokeless. I currently have 2 Rem. 700mlss muzzleloaders but they both shoot pretty well and with one I've killed numerous elk from 180 to 220yds. If I did smokeless it would probably be more for play than hunting as our F&G changes stuff all the time and if they actually caught wind of someone using smokeless and a scope they would probably change the rules for short range weapons. Currently the short range weapons rule just states any muzzleloader rifle or musket of .50 or bigger for elk. The muzzleloader only rules are much more restrictive. It says only open or peep sights, loaded only from the muzzle, you can only use loose BP or equivalent, single or double barrel, the projectile must be within .010" of bore diameter and sabot are prohibited, loaded with only patched round balls or conical non-jacketed made of lead or lead alloy only, can only use flint/percussion cap/musket cap for ignition, and the ignition system must be exposed or visible.

 

[edge]

Doug's yes

The base is very heavy and generally ends up 50 or more yards downrange.
The petals are concave in the front so in theory they peel away almost instantly.
If I don't machine the reliefs in the sabot below the bullet base the accuracy is hurt, so when designed properly they do not interfere.

Your Rem ML is easily converted, but since you know of Doug's you must know that already :wink:

My first custom ML barrel was a 505 Gibbs from Krieger with a 1:20 twist.
I never tried to shoot it without sabots but I bet that it could.
BP equivalent hmmm perhaps a loophole

A paper patched conical can be pretty good way out there...but no scope, that would really handicap someone with my eyesight!

edge.

 

[IdahoCTD]

I might just build a switch barrel and do a 45 and a 50 but I might have to try and find another junker 700ml so I don't have to tear these apart. You can never have enough guns :lol: . I might also just rebarrel the one I don't use much to .50 for BP and build another just for smokeless in .45 so it's still legal for deer.

I first signed up on Doug's about 2-3 years prior to the site change. I was wondering how long it was going to take for people to do the Remmies back in the beginning. I wish we had the rules you guys have back east. If we did I'd probably of built 2 or 3 by now. It's just hard for me to build a gun I may not get a chance to shoot something with unless I hunt with it in the general rifle season. I guess there is always varmints too.

 

[SJB358]

I would be remiss if I did not note that the following year I switched to the 150 AB.
Since I fire my load out at the end of each day, one day I shot the AB at a tree from about 30 yards and the impact was easily over 3k fps.
I saw that the bullet exited and was lodged less than 1 inch into a tree a few yards away. I came back a few days later with a cordless sawzaw and cut it out.

Here are pictures of the tree with a can of Goex for size comparison and the bullet from both ends.

edge.

That 150 looks really good!

 

[edge]

That 150 looks really good!

I agree 100%

BUT the problem is that was shot at about 40 degrees and it was sub moa.
When I shot it last year at a much lower temperature I could not hit a 4 foot target at 100 yards!

That is the reason for this thread!

I just don't know if it is:
not stable @ zero degrees;
sabot failure of some sort due to temperature.

If it is sabot failure then I may have to rethink the polymer that I use, if it is just bullet instability at that temperature then I just need a different bullet or a different barrel.

Now if the 300 grain AB comes close to their predicted BC I will be thinking a new barrel

edge.

 

[IdahoCTD]

Wow a 300gr .338 in a muzzleloader would be a long range killing machine if you could shoot it fairly fast (kill out of both ends too)