FB vs BT Bullets

[Walkalong]

um…

Benchrest competition is held out to (at least) 1,000 yards…

True, but the FB bullet rules at 100 & 200 yard Benchrest.

 

[Varminterror]

True, but the FB bullet rules at 100 & 200 yard Benchrest.

Definitely so.

 

[nettlle]

That doesn't necessarily mean a FB or BT is going to be the most accurate in a certain gun.

 

[JerkyFreak]

On average by far the majority of cases, flat base bullets are more accurate at short range.

Simple reason is at muzzle exit, the flat base direct the following muzzle blast to the sides. Boat tail bullets are nicely shaped to direct the muzzle blast around it from the base to the tip to create a pocket of disturbed gasses right in front of it.

Any small imperfection on the crown has a dispropotionately larger effect on boat tail bullets as opposed to flat base bullets. If it wasn't for the fact that boat tail bullets have better BC's than similar weight flat base bullets, nobody would use them.

 

[Chief TC]

Let us add to the problem that the OP is shooting full stocked service rifles. Having many myself, we don't know how compressed the wood is around the receiver, whether the action is bowed. And in how many places in the fore end, does the barrel touch. Those full stocked military rifles shoot well with a very narrow spectrum of bullets and loads.

as an example of the troubles with bedding, this rifle was bedded according to the best practices of the time. It has a custom barrel, and Joe the original owner, carefully inletted the for end of the stock so the barrel was in complete contact with the fore end . Joe thought the rifle was accurate.

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the rifle shot horribly

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I bedded the action, free floated the barrel, groups became round

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It is "right" to say the bullet is why the OP's group has shifted. But then, if the OP had rubber banded a fishing weight on the end of the barrel, it is very likely he would have seen a point of impact shift regardless of bullet. Action and barrel dynamics have a huge affect on point of impact, and without measuring devices, about the best that can be said is a change in components will make a change on target. But what exactly is causing the shift is probably a combination of factors.

And those wartime barrels were built fast, the primary consideration was to get them out the door. Many have been used in training, the bore rubbed large by cleaning rods. A 115 year old service rifle is not going to be a consistent nor calibrated test device.

The OP should find a load that shoots well in his military rifles, set the sights so the point of aim and point of impact coincide. And never change his load. Leave things alone. And have no expectation that a different load will hit paper.

Thanks Slamfire, always appreciate the detailed explanations you give. This is why I posed the question. To learn possible reasons why, not to solve a problem. My M1917 when I got it was not bedded correctly and took me awhile to get it all in shape. Major trainwreck pattern, no grouping, then large grouping, then vertical, then horizontal before I got it dialed in with 180 BTs. So many folks hate the sights on it but it shoots just as well as the 1903A3.

 

[9x56MS]

In my experiences, every rifle is an entity unto itself. They have different preferences for bullets, powders, primers and ammo brands. I can honestly say I have not experienced that degree of difference due to bullets but have had shifting impacts due to multiple variations. The trick is finding what your rifle likes then tweaking to maximize accuracy.

 

[S.Crockett]

Since this is with both my 1903A3 and 1917 with standard sights, it is not a scope issue. I shot 5 shot groups of each type of bullet with each rifle and got the same result.

Since you’re shooting each rifle with iron sights, maybe a shooter issue accounts for the 4 MOA difference?

 

[JerkyFreak]

4 MOA does sound a bit excessive. But probably not impossible.

On both of my target rifles, when changing from Berger 155gr VLD to Lapua 155gr Scenar I have to adjust my sight 1 1/2 up and 3/4 right. This is repeatable and holds true from 100yrds to 800yrds. And yes, both bullets were loaded to the same velocity.

 

[pert near]

Could be due to an imperfection in the crown. It would interesting to see the effects of a re-crown.

 

[Turkeytider]

Anybody know if ANYBODY manufactures a factory target ( preferably match grade ) round in .223 with a FB bullet? Can find hunting rounds but have never seen a target round with FB bullet.

 

[Hugger-4641]

Can find hunting rounds but have never seen a target round with FB bullet.

There might be a clue there. I've shot both in .223 and by far the most accurate factory rds were the Hornady Black 75gr bthp. I"d venture to say the better BC of a Bthp has more consequences in a smaller lighter bullet as opposed to say, a .308 cal bullet.

 

[Chief TC]

Since you’re shooting each rifle with iron sights, maybe a shooter issue accounts for the 4 MOA difference?

Don't claim to be an expert rifleman, but I developed the load my rifles liked with BTs and they shoot 1 MOA at 100 and group in the bullseye. When I decided to try some FBs, they group at 2 MOA and print 4 inches diagonal from the BTs. This was both M1917 and 1903A3, so 2 different rifles. Could it be me? Sure. But based on the results of shooting and switching, seems my POA is unchanged with each shot.

 

[Slamfire]

Since you’re shooting each rifle with iron sights, maybe a shooter issue accounts for the 4 MOA difference?

Not that it takes years to learn how to shoot irons, (decades without coaching!) but sight alignment and positional errors are things typically discounted by most. However, shoot Smallbore Prone where the recoil and blast of the cartridge do not mask sight alignment and positional errors, and you will see things you never saw shooting centerfire. When you slide up and down on the stock, the group moves up and down. When the buttplate is moved in and out on the shoulder, the group also moves laterally. Flinching will shift a group. The stock drop on a M1917 is huge, and all that is under your chin is a pistol grip, not a cheek rest.




The straight grip 03 stock is horrible in this aspect, and if you try to use your thumb for a stock weld, your lips will pay the price.



Ergonometrics are huge when it comes to consistent shooting, and the shooting ergonometrics of WW1 era service rifles were hugely compromised to met the demand of the bayonet fighters. A poor shooting stock, but effective in sticking people



this is Joe Farmer's rifle, he was 86 at the time, and Senior Smallbore National Champion. Joe made this stock, and you can see (expect for the buttplate) how much effort Joe put into getting his trigger hand position exactly in a stress free position, the cheek piece comfortable and having his eye in line with the sights. I don't remember the buttplate but usually they are adjustable for distance and cant. And of course, the wood is amazing. Joe said he purchased the blank for around $65.00 at Camp Perry in the 1960's and had been offered $1000 for it. Prone and 3P shooters want their position on the stock to be stress and pain free, and they want to line up exactly the same each time when they look through the sights. Repeatable positional alignments are not possible with military stocks optimized to stick people with pointy objects.




You learn in rifle competition not to break your position!

 

[Chief TC]

Not that it takes years to learn how to shoot irons, (decades without coaching!) but sight alignment and positional errors are things typically discounted by most. However, shoot Smallbore Prone where the recoil and blast of the cartridge do not mask sight alignment and positional errors, and you will see things you never saw shooting centerfire. When you slide up and down on the stock, the group moved up and down. When the buttplate is moved in and out on the shoulder, the group also moves laterally. Flinching will shift a group. The stock drop on a M1917 is huge, and all that is under your chin is a pistol grip, not a cheek rest.

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The straight grip 03 stock is horrible in this aspect, and if you try to use your thumb for a stock weld, your lips will pay the price.

View attachment 1158196

Ergonometrics are huge when it comes to consistent shooting, and the shooting ergonometrics of WW1 era service rifles were hugely compromised to met the demand of the bayonet fighters. A poor shooting stock, but effective in sticking people

View attachment 1158197

this is Joe Farmer's rifle, he was 86 at the time, and Senior Smallbore National Champion. Joe made this stock, and you can see (expect for the buttplate) how much effort Joe put into getting his trigger hand position exactly in a stress free position, the cheek piece comfortable and having his eye in line with the sights. I don't remember the buttplate but usually they are adjustable for distance and cant. And of course, the wood is amazing. Joe said he purchased the blank for around $65.00 at Camp Perry in the 1960's and had been offered $1000 for it. Prone and 3P shooters want their position on the stock to be stress and pain free, and the want to line up exactly the same each time when they look through the sights. Repeatable positional alignments are not possible with military stocks optimized to stick people with pointy objects.


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You learn in rifle competition not to break your position!

Yes! The key is being repeatable in how you do everything touching and shooting the rifle. My M1917 load was developed from a benchrest position and I focus a lot of all the components of sighting and holding techniques that are the same. Ran a competition course of fire to practice and was 26 of 28. Got to the competition and was told we shoot military bolt off of cross sticks (this group mainly shoots buffalo silhouette but they add military single shot and military bolt). Shooting off of cross sticks, I was 20 of 28. Sitting on a short stool on cross sticks was a major change. Not to mention, I didn't know if I had the rifle placed on the sticks in the best location to minimize jump/bounce.

 

[DMW1116]

I’ve only seen this in one of my rifles and that involved switching from jacketed to cast & coated bullets. The jacketed shoot right of the cast ones by about 2.5” at 100 yards. I’ve also seen it in my 357 revolver. Cast bullets shoot a fair bit left of jacketed.

 

[lysanderxiii]

Out to 300yds, the boat tail has no advantage.

No.

Boat tail bullets will always maintain velocity better than flat based bullet, at all ranges.

 

[Random 8]

My M1 and M1917 act similarly to yours. The POI is a random shift, but FB and BT of same weight and loading definitely have a different POI. I have a few rifles where I haven't noticed any difference.

 

[Walkalong]

Out to 300yds, the boat tail has no advantage.

No.

Boat tail bullets will always maintain velocity better than flat based bullet, at all ranges.

But the subject was accuracy, no advantage concerning accuracy out to 300 yards, which I tend to agree with. If they did, they would rule short range Benchrest, which they do not.

 

[GooseGestapo]

Thanks Walkalong!
Reading comprehension is golden!

 

[redneck2]

Thanks Walkalong!
Reading comprehension is golden!

or, in the unforgettable words words of Richard Nixon in 1970

“I know you believe you understand what you think I said but I not sure you realize what you heard is not really what I meant “

 

[Slamfire]

But the subject was accuracy, no advantage concerning accuracy out to 300 yards, which I tend to agree with. If they did, they would rule short range Benchrest, which they do not.

I will bet concentricity is better maintained in a flat base bullet, and it is easier to make a FB bullet in which the center of gravity stays in the axis of rotation. Jackets are punched out, than punch extruded, and the cores (used to be) punched in. Has to be easier to control in a flat based bullet than a boat tail.

If someone here works for a bullet manufacturer, I would be interested in reading their opinion.

 

[Jim Watson]

Benchrest shooters seem to agree.
I shot a good many JLK bullets with rebated boattails, meant to give a sharper square transition from tail to bearing surface. Maybe it worked, they were accurate.

 

[JerkyFreak]

No.

Boat tail bullets will always maintain velocity better than flat based bullet, at all ranges.

Yes. Which is why BT rule longer range precision competition.

At shorter ranges there is some doubt if the marginally faster boat tail bullet can overcome the sligtly worse precision caused by traveling through it's own muzzle blast.