twist,bedding?

sniperman

lads what do the above terms mean?and do i need to pay attention to them when buying a 223 for fox?

valerossi

Do you mean twist rate? If so it's the rifling which spins the round eg how many rotations the bullet will do in the barrel making it more accurate in theory but barrel length effects this too.
Bedding is when you work the factory stock with a goal of getting more contact with the action and stock which also aids accuracy.

I say keep them in mind but don't fuss unless you thinking serious target shooting.

Cass

Twist rate is important to bullet choice and type of shooting. The faster the twist rate the more suited it is to heavier bullets. The slower the twist the more it is suited to lighter bullets.

So a 1:12 would be ideally suited for 40 - 55 gr in .223. A 1:9 would suit heavier bullets such as 68 - 75 gr. Lighter bullets are flatter and drop less but only over shorter distances. Heavier bullets suffer more from drop due to their slower speeds, but maintain their speed better over longer distances due to superior ballistics making them suited to long range shooting.

Some rifles and twist rates buck this trend. My old CZ 527 was a 1:9 twist meaning it should prefer heavier bullets such as 75 gr. Now while it shot them, and well it also performed excellently with 53 & 55 gr bullets. Even some 40gr. They shouldn't really work as the fast, light bullet in a fast twist should not stabilise and hence not be as accurate.

Bedding is the use of a resin, block or pillars (or combination of all three) to have contact between the stock and action only, and have the barrel completely free floated. This prevents any distortion in the barrel harmonics from touching the stock when firing and increases consistency and accuracy. Vital in target shooting not so much in hunting. However something that if given the chance/money i would get done.

FISMA

+1 to what Valerossi said.

If you are just getting in to the game, the factory twist rates should be fine and you will not need to trick out the stock - pillar and bedded.

A Boyd's stock would be just fine.

I had a Hogue SPS stock that shot fine out to 300ya.

It wasn't bedded, pillared, or free-floated. Nothing I would ever use nowadays, but in the early days when I was climbing ditches at night and taking shots inside of fields that rarely were bigger than 200ya, she was just fine.

Save your money and when you have the cash, get a custom stock.

clivej

Here is a link to how I bedded my rifle, from the tips section in hunting forum

http://www.boards.ie/vbulletin/showpost.php?p=66882815&postcount=62

yubabill1

I would not worry too much about twist rate or bedding at this stage.

For a start almost all RFD's will know little, if anything about twist rate.

Get yourself the most metal, with the best reputation for your money and you won't go far wrong.

When you need to hit something less than 1/2" @ 100yds on a regular basis, you might want to look into twist and bedding.

Jonty

Cass wrote: »

Twist rate is important to bullet choice and type of shooting. The faster the twist rate the more suited it is to heavier bullets. The slower the twist the more it is suited to lighter bullets.

So a 1:12 would be ideally suited for 40 - 55 gr in .223. A 1:9 would suit heavier bullets such as 68 - 75 gr. Lighter bullets are flatter and drop less but only over shorter distances. Heavier bullets suffer more from drop due to their slower speeds, but maintain their speed better over longer distances due to superior ballistics making them suited to long range shooting.

Some rifles and twist rates buck this trend. My old CZ 527 was a 1:9 twist meaning it should prefer heavier bullets such as 75 gr. Now while it shot them, and well it also performed excellently with 53 & 55 gr bullets. Even some 40gr. They shouldn't really work as the fast, light bullet in a fast twist should not stabilise and hence not be as accurate.

Bedding is the use of a resin, block or pillars (or combination of all three) to have contact between the stock and action only, and have the barrel completely free floated. This prevents any distortion in the barrel harmonics from touching the stock when firing and increases consistency and accuracy. Vital in target shooting not so much in hunting. However something that if given the chance/money i would get done.

Just on this, rate of twist is dependent on length of bullet, not weight. It just so happens that longer bullets are generally heavier. However some 40gr ballistic tips are long for their weight. I'll try and dig up the link I found.

As the rest of the lads said, they will all be capable of doing .5MOA, if you can do your part

Cass

Jonty wrote: »

Just on this, rate of twist is dependent on length of bullet, not weight. It just so happens that longer bullets are generally heavier. .

I know and understand this, but given the OP is asking what twist rate and bedding is i didn't think an indepth debate on ballistics was warranted so kept it to a minimum (no offence intended to anyone there).

The majority of bullets work on the basis that the heavier they are the longer they are. It's common sense. If the caliber (hence diameter) is fixed then the only way to make something heavier is to make it longer. Now this is not to be confused with overall length of the bullet from base to tip. It only applies to bearing surface (when talking about twist rate). IOW the part of the bullet that actually engages the lands & grooves of the barrel. Everything from the "end" of the bearing surface onward (Ogive to tip) is never in contact so has little bearing on the twist rate/bullet decision.

There are some that buck this trend as described above. For example in .308 the 185 gr works well in a 1:11 or 1:10 twist. Now if you compare a Lapua Scenar against the 185 there is not a huge amount of difference in length of bearing surface even though the 185 is longer than the 155, and if you compare the Lapua 155 against the Berger 155 the Lapua is longer. Hence the Lapua will actually work well in a 1:11 or 1:10 twist rifle but the Berger being shorter and hence having a shorter bearing surface will not.


The manufacturers obviously differ the process for making the bullets to allow for a lighter yet longer bullet.


So while twist rate should not be too much of a deciding factor when picking a rifle it should be considered and more importantly when a rifle is chosen find out what the twist rate is to help aid you in your bullet choice.

FISMA

My latest addition has a twist of 1:28.:eek: I think the lads at Thomond have a similar rates of rotation!

Turns, out muzzleloaders do not have much of a rotation. Spot on at 100ya, haven't tried it out to 200ya, but will soon. I heard you should not expect much more than 200ya out of a ML.

I suppose a 300gr 12ga sabot should't have a 1:9 twist though!

Zxthinger

clivej wrote: »

Here is a link to how I bedded my rifle, from the tips section in hunting forum

http://www.boards.ie/vbulletin/showpost.php?p=66882815&postcount=62

Tasty work Clive, ye'd know ye have plenty of free time on yer hands

Zxthinger

Cass wrote: »

. IOW the part of the bullet that actually engages the lands & grooves of the barrel. Everything from the "end" of the bearing surface onward (Ogive to tip) is never in contact so has little bearing on the twist rate/bullet decision.

That is wrong!! Bullet beyond the point OD swaging on the land has a considerable impact on twist rate decision. The diff profiles on bullet tips leads to the diff arodynamics that can cause instability. Longer bullets need faster rates of spin! With you get it with a faster ywist rate in your barrel or you churn the pill out faster.

Cass

Firstly that post is somewhat illegible. Not trying to be a dick (it's good to have a debate on ballistics) but short hand, abbreviations, etc. are making it hard to understand.

I've highlighted the bits i'm having trouble understanding .

Zxthinger wrote: »

That is wrong!! Bullet beyond the point OD swaging on the land has a considerable impact on twist rate decision. The diff profiles on bullet tips leads to the diff arodynamics that can cause instability. Longer bullets need faster rates of spin! With you get it with a faster ywist rate in your barrel or you churn the pill out faster.

However here is my response to what i think it says.

That is wrong!

No it's not. You're discussing external ballistics, and i'm talking about internal ballistics.

Bullet beyond the point OD swaging on the land has a considerable impact on twist rate decision. The diff profiles on bullet tips leads to the diff arodynamics that can cause instability.

If i'm reading this right you are saying that the tip of a bullet, it's design (secant/tangent/hybrid ogive) and hence it's aerodynamics have an impact on the performance in terms of internal ballistics? Well that's simply wrong.

Internal ballistics deal with the bullet from the moment of ignition (firing) to the moment it leaves the barrel. There are no wind or aerodynamic aspects to consider. Only the bullets engagement with the lands, the length of bearing surface of the bullet, and twist rate of the rifle.

The very moment the bullet leaves the barrel then external ballistics come into play and it's only then the shape of the bullet, it's ogive design, and aerodynamics come into play.

Longer bullets need faster rates of spin! With you get it with a faster ywist rate in your barrel or you churn the pill out faster.

As i said above the length of the bullet in terms of internal ballistics, and twist rate is only applicable to the length of the bearing surface. All other aspects do not come into play.

I gave an example of this with the comparison between Lapua 155 gr, Berger 155 gr, and Berger 185 gr bullets. The Lapua 155 and Berger 185 have longer bearing surfaces than the Berger 155 and so even though the Berger 185 is heavier than the Lapua 155 they both perform well out of a faster twist rifle (1:10 - 1:11). Whereas the Berger 155 bullet with it's shorter bearing surface will not. The lighter bullet, with shorter bearing surface, in a fast twist rifle will cause excessive RPM once it exits the barrel and cause instability in flight either at the tip or the base of the bullet. This is what contributes to keyholing.


So let's recap. What i said was spot on. You have mistaken external ballistics for internal ballistics, and are arguing about aerodynamics when it's not relevant to internal ballistics. Lastly you have repeated what i said above about a longer bullet needing a faster twist rate, but omitted the reasoning i provided above as to why and that it only applies to bearing surface and not overall length of the bullet when speaking in terms of twist rate.

A discussion on internal AND external ballistics would require a different approach. As now you must not only determine how the bullet performs in the barrel (internal ballistics), but also it's performance once it leaves the barrel (external ballistics). This is why when choosing ammo we must test different brands as different manufacturers produce differently designed bullets in terms of bearing surface length, overall length, and Ogive design.

EWQuinn

"The Lapua 155 and Berger 185 have longer bearing surfaces than the Berger 155 and so even though the Berger 185 is heavier than the Lapua 155 they both perform well out of a faster twist rifle (1:10 - 1:11). Whereas the Berger 155 bullet with it's shorter bearing surface will not."

That is correct, people often think it is bullet weight that is the governing factor in the affect of twist rate. The twist rate of a barrel and the affect on bullets is more dependent on the length of the bullet (as in bearing surface) rather than weight. As stated previously, generally speaking or on average heavier bullets have more bearing surface.