03A3 2 Groove vs. 4 Groove Barrels

[Multigunner]

Multigunner,
Thanks for that post and it makes sense to me- it kind of ties a lot of loose ends together about the various powder types. Although academic for the most part it may explain some of the latest generation powders like the Vihtavuori 500 series and others. Exactly how it all plays into the 2 vs 4 groove stuff I dunno as it's well beyond my level of understanding but very interesting nonetheless.

Two groove bores have broader lands, a bore with broad lands is less affected by erosion. The Remington two groove barrels compressed the bullet more in the initial engraving, which made up for any looseness in bullet to bore fit due to manufacturing tolerances.
The tighter fit caused some concern when it was found that firing steel core M2 AP bullets in a two groove bore resulted in a increase in pressure of up to 4K CUP, about 8%, while delivering slightly lower velocity compared to a four groove bore.
British experiments with two groove .303 machine gun barrels indicated that the greater compression and friction caused their .303 tracer bullets to break up. U S .30-06 Tracers were not subject to break up in two groove bores, but this illustrates a potential concern with some bullet types.

A two groove bore 03A3 or M1917 with Johnson two groove rebarrel is less affected by poor cleaning technique and can digest a wider range of propellent types without rapid loss of accuracy due to erosion.
A two groove bore may cause an increase in chamber pressure, but well withing the safety margin of the 03A3 and M1917 actions.
The British two groove No.4 .303 barrels are most often of generous dimensions which prevents excessive engraving pressure and friction, so increased chamber pressure has not been a problem.

[1Shirt]

As usual find it hard to disagree with anything that Larry Gibson writes! Same case here! Have an old cobbled together 2 land springfield that shoots well enough with most all weights of cast from 150 on up, but best with the long heavies-emphasis on 311284 in HP.
1Shirt!

[rjathon]

Thank you Multigunner for your excellent reply.

[Multigunner]

then seems like a micro groove bore would burn out in no time??

How many .30-06 rifles have you seen with a microgroove bore?
The Marlin .30-30 with microgroove bore benefits from the mild pressures and low charge weights of that cartridge. Even so I have no doubt that the same rifle with fewer grooves and broader lands would last a bit longer.
.22 Rimfire rifles with microgroove bores will last just about forever, just as a .22 rimfire with any other type bore because the cartridge does not erode bores quickly.
In earlier times .22 RF barrels were made from very mild steel and were subject to erosion as well as corrosive primer salts. A microgroove bore of that sort of soft steel and used with the highly corrosive ammo of the day would probably have been worn out very quickly.

Modern sniper rifles use an updated version of Enfield rifling in order to reduce the effects of erosion on accuracy, they don't use micro groove barrels because those would not last nearly as long, even with the best modern stainless steel alloys.

[Larry Gibson]

Larry,
I find it interesting that you are now shooting normally cast bullets (i.e. w/o copper) at 2600 fps after posting for years that the cast bullet threshold is <1800 for a 10 twist. A "Palma" rifle would normally have a 12 twist at the very slowest and that wouldn't fit the "threshold" either.

So, what's the secret? Or doesn't the threshold apply anymore? Or do you just need more lube grooves? I'm sure that we woulld all like to know the answer.

So we can all know, what is the average differance in group size or score between the 2 groove vs 4 groove @ 500 or 600 yards.

Have any of your groups or scores been recorded at a offical CBA match so we can compare your 4 groove scores against 2 groove scores?

Respectfully,

Frank

Frank

I have been reporting on the 2600 fps in the Palma rifle (it has a 14” twist BTW) for several years now, nothing new there and what it has to do with threads topic?

The RPM threshold for the 10" twist is in the 120 - 140, 000 RPM range (I've been saying that fact for many years also) which tops out around 1950 fps......the math is simple to do but if you have problems with it please ask and we'll explain it.

Most Palma barrels have 13 or 14" twists if chambered in .308W. The standard twist for the .308W is 12" (standardized by Winchester who introduced the cartridge) although several makers use 10" twists because that’s what is common in most other 30 cals.....an ease of production cost thing.......some manufacturers have gone back to the 12" twist (Remington for one).

The 2600 fps from a 14" twist is not crossing the RPM threshold........if that's what you mean? And really what does all this about the RPM threshold have to do with the OP’s question? You really need to get your facts straight before you pull the trigger..........I got an email from joe (starmetal) and he is quoting you or are you quoting or proxy posting for him? The RPM threshold has nothing to do with which type of barrel is more accurate so I won’t discuss that topic with you on this thread, period.

However, back to the OP’s question; " Is there really any appreciable difference between the two with regard to overall accuracy? Looking for a good cast bullet shooter. Is one really any better or worse than the other?”

Perhaps you're not aware that CBA isn't the proponent for High Power matches? The NRA is. In a HP match at 500 and 600 yards the group size is not measured as each shot previous shot is pasted before the next shot. A little experience or research on your part would have revealed that.

I have already said the 4 grooves shot better at longer ranges in High Power matches in answer to the OP’s question and in response to some misunderstandings.....anyone would know that means the scores were better......1 point or 50 points, average difference in group size or score is not relevant; better is still better.......now isn't it and doesn’t that answer the OP’s question?

CBA matches are not long range belly matches (High Power) or the NMC.......and yes the scores of the registered matches were recorded with the NRA.......that's how one gets a Service and Match rifle classification.......in my case when I went from a shooting 2 groove M1903A3s with Lyman M48 rear sights (the M1903s fall in with "Match" rifles so the change in sights is ok) to M1903A1s with the same Lyman M48 rear sights my scores with the same 311284 cast bullet load took me from Marksman up to Expert classification. My scores at 200 yards were pretty much the same, a couple points better at 300 yards but were noticeably better at 600 yards where the real difference was very apparent.

The difference in accuracy was apparent with several 2 groove and several 4 groove rifles. I made the change to 4 groove barrels at one of the coach’s insistence. He said the 4 groove M1903s always shot cast better at long range and they indeed did shoot better at long range for me. I also had access to several M1903A4s in excellent condition in my SF unit. I shot those at 500 yards with the same cast load on the V bull. I could actually shoot higher scores with the M1903A1four groove barreled rifles with Lyman 48 sights than with the 'A4s with 2.5X scope on it having 2 groove barrels. BTW; I was not shooting groups either but 22 shot (2 sighters + 20 for record) strings for score.

Larry Gibson

[45 2.1]

These are simple basic yes and no answers:
1) Are we to assume that the "four groove out shoots the two groove" was done with the 311284 in all rifles?
2) Your basis of accuracy was score instead of group or string measure?

See if you can keep the answers short and to the point...........

[Larry Gibson]

See if you can keep the answers short and to the point...........

45 2.1

1) Yes, most of the early 200 - 500 yard shooting on the V bull was done with the 311284. Somewhere I did switch to the 311299 as it proved more accurate in both 2 and 4 groove barrels at 600 yards as it has the better BC.

2) That is correct. Since the "group" was centered over the bull (both V and Decimal targets) the better the score the smaller the group. I shot enough to have good zeroes. But I recall comparing the overall group size and center of the group in my record books to have those zeroes. The "group" is actually the cone of fire and since every shot placement is recorded in the record book it's easy to see which was the more accurate by score and group size even though the "groups" were not measured. If you don't understand that then you've not much experience shooting High Power and using a record book.

BTW; just how much experience do you have shooting both 2 and 4 groove M1903s with cast bullets at 300 - 600 yards, either for record or for group size?

Larry Gibson

[argie1891]

Larry i am not questioning your results but dont understand how one that shot well at shorter ranges would shoot less well at longer ranges all other things being equal... unless there is damage to the bullet as it engraves the rifeling that dosent affect it till it slows down or well i cant think of anything right off hand. again i dont want to start a fight over which is better i just would like to understand the reason for the difference. there has to be some damage to bullet or something. did you ever come to any conclusion as to why the scores were better with one than the other. argie1891 aka joe gifford

[Multigunner]

The break up of .303 tracer bullets in two groove machinegun barrels suggest that a two groove bore may damage or distort bullet jackets. It depends on bullet construction since U S .30 tracer bullets were not subject to break up in two groove MG barrels.
The increased chamber pressure when firing AP bullets, along with a slight reduction in velocity compared to the same ammo fired in a four groove barrel sugest some increase in stresses which would have some effect on the bullet.
Also if you notice arrows with only two vanes of fletching are more subject to deviate in flight if one vane is damaged than arrows with three vanes. Crossbow bolts of olden days, and some modern bolts, usually had two vanes, to make it easier for the bolt to ride the rail, and were not noted for long range accuracy compared to bows. The Swiss and Germans developed crossbows for precision target shooting that did not rely on fletching. Instead the metal bolt had spiral grooves passed though a opening with studs that engaged the spiral grooves, the forward motion imparting spin. A sort of mirror image form of rifling.

[HARRYMPOPE]

Larry- i have two buddies with very minty 03A4's and neither shoot any better than good 2 groove A3's.I kind of thought they would be tack drivers but were not.
How much larger were the groups at 600 yards when comparing the 2 to 4's? i have only tested them(6 or 8 barrels ea i bet) to 300 yards and could detect no accuracy difference with cast.It mostly depended on me reading the right wind condition at that particular day.

[FAsmus]

Harry & Larry;

My comparison of 2 vs 4 (or 6) groove barrels shooting as they do, similar groups @100 yards and then moving out to 830 yards in stages is like Harry's ~ any basic difference in accuracy is lost, undetectable (for me) due to the much more significant problems associated with condition.

Good morning,
Forrest

[45 2.1]

It mostly depended on me reading the right wind condition at that particular day.

My comparison of 2 vs 4 (or 6) groove barrels shooting as they do, similar groups @100 yards and then moving out to 830 yards in stages is like Harry's ~ any basic difference in accuracy is lost, undetectable (for me) due to the much more significant problems associated with condition. Good morning, Forrest

Since Larry was shooting Hi Power, he wasn't on a good solid bench. Wind and light conditions plus variable holding effect results greatly as conditions cycle (mechanical zero changes with condition, you either change the sights or hold off). He was testing what he could do, not what the rifle was capable of. Had he of picked one of four designs, available then, and known to produce excellent results with the two groove, he would have seen quite different results. I know I did and I bench tested them extensively at long range.

[Larry Gibson]

... unless there is damage to the bullet as it engraves the rifeling that dosent affect it till it slows down or well i cant think of anything right off hand.....

As several are mentioning that is what is happening. However the "damage" to cast bullets greates and unbalance where a large part of the bullets mass (the opposing parts of the bullet formed in the grooves) is farther from the center of axis, the center of spin and the center of balance. Also the larger the area of the bullet swaged by lands (the 2 groove has a larger land surface than the 4 groove) then the more the bullet is distorted. All that leads to small imbalances which show up and are more pronounced at longer range in larger groups or.....inaccuracy.

Larry Gibson

[Larry Gibson]

Deleted, I have no idea where that post came from out of the blue on this thread????

Larry Gibson

[Larry Gibson]

Larry- i have two buddies with very minty 03A4's and neither shoot any better than good 2 groove A3's.I kind of thought they would be tack drivers but were not.
How much larger were the groups at 600 yards when comparing the 2 to 4's? i have only tested them(6 or 8 barrels ea i bet) to 300 yards and could detect no accuracy difference with cast.It mostly depended on me reading the right wind condition at that particular day.

Harry

There was nothing all that "select" about the 'A4...

At 500 yards on the V bull the the 2 grooves held 3 ring and the 4 grooves held 4 ring with the 311284 bullet. At 600 yards on the Decimal bull the 311299 held 7 ring with the 2 grooves and the 4 grooves held 8 ring. Using the 4 groove rifles and the 311299 bullet I made the jump from Marksman to Expert.

Larry Gibson

[Larry Gibson]

Since Larry was shooting Hi Power, he wasn't on a good solid bench. Wind and light conditions plus variable holding effect results greatly as conditions cycle (mechanical zero changes with condition, you either change the sights or hold off). He was testing what he could do, not what the rifle was capable of. Had he of picked one of four designs, available then, and known to produce excellent results with the two groove, he would have seen quite different results. I know I did and I bench tested them extensively at long range.

Max effective range of that excuse is 0 meters.........once again you come up with an excuse why someone can not do what say can be done.......

As I mentioned above had there been a one time test perhaps what you say could be. However, given the use of several rifles of each barrel type over several years with numerous 500 and 600 yard 22 shot scores/groups and the 4 groove barrel M1903s consistently shooting better than 2 grooves answers the question.

BTW; your lack of High Power shooting knowledge is self evident. Many shooters, especially those of expert or higher classification, shoot as good if not better slow fire prone than off the bench. With a good shooting jacket and sling which is properly adjusted the prone position is as solid as the bench position. Back in the day when I was in practice I definately shot my match riflesas well prone as off the bench as many others do. Again, a little research before pulling the trigger.................

Larry Gibson

[45 2.1]

BTW; your lack of High Power shooting knowledge is self evident. Many shooters, especially those of expert or higher classification, shoot as good if not better slow fire prone than off the bench. With a good shooting jacket and sling which is properly adjusted the prone position is as solid as the bench position. Back in the day when I was in practice I definately shot my match riflesas well prone as off the bench as many others do. Again, a little research before pulling the trigger................. Larry Gibson

By that logic..... the bench rest shooters and CBA record holders would be doing that...... And they're not, nor are they going to..... they know better, so that stone bird don't fly. Current records in the CBA for group shooting is in the 0.1" to 0.2" range. We've seen your Palma rifle groups... or lack of group as it shows in line with current practices. Maybe you can post some Cast Boolit groups showing its worthiness. As for the NRA high power, maybe you can provide your participation dates and scores..... because some folks here have looked for your name and scores and didn't find you listed.

[Larry Gibson]

45 2.1

Tell ya what; how about you get several 2 groove M1903A3s and several M1903 with 4 groove barrels and benchrest them at 600 yards with a cast bullet load shooting 20 shots for "group" or for score in front of credible witnesses and see what you come up with. That way instead of the usual criticism based on your own opinion instead of facts you will have something factual that you have actually done yourself that you can talk about?

As for the NRA high power, maybe you can provide your participation dates and scores..... because some folks here have looked for your name and scores and didn't find you listed.

What "folks"? Let them come forth and state their claim to fame! However I'm calling BS on that as it is more likely your usual personal attack on someone's credability when you can't stake a claim with facts. If you are talking about *** as the "folk" (we all know who) he has no credibility.

I have a Master classification in NRA High Power (200 - 600 yards) and Long Range (600 - 1000 yards). You get that by shooting registered matches and shooting the required number of scores over a number of matches at those actual ranges. You don't get that by shooting groups with a keyboard or by posting "what others have done"....BTW what classification in any shooting sport do you have? I could post my credentials but it is for you and the "folks" to prove me wrong, good luck with that.

As usual 45 2.1 is ruining another thread with his inane personal attacks and attempts to discredit someone. Until he can come up with something substantial to disprove my answer to the OP's question then further discussion with him isn't worth the effort.

Moderator (any) who wants to see my credentials please PM me and I will gladly show them to you.

Larry Gibson

[Multigunner]

Bench rest shooter with 35 pound rifles can do as they like.
I've always shot tighter groups from the sitting position with elbows braced to inside of thigh or knee than from a shooting bench or other solid rest. Thats with rifles of aproximately ten pounds or less.
Were I using a heavy weight custom long range target rifle I might do better from a rest.
I do as well from the prone position, but its uncomfortable for me.

Far as I can tell no maker of target grade barrels uses a two groove bore. Some three groove matchgrade barrels are offered, and three groove barrels have a long history in the U S dating back to early .50 Trapdoor Springfield days when cast bullets were the norm.

From what I've read on the subject WW 2 wartime four groove Springfield barrel had a lower standard of accuracy than earlier manufacture four groove barrels. In 1916 any thing over 2 MOA on four of the first five shots fired through a new barrel was unacceptable.
The rifle with four groove bore used as a control when testing accuracy potential of the two groove barrel was only giving 3.5 MOA groups.
Its entirely possible that the four groove barrels coming off the line at that time were inferior to the two groove barrels, at least the two groove barrels from that first batch.
If theres twice as much work being done to rifle a barrel then theres twice as much chance of screwing something up.
I've run across complaints of two groove bores that varied in internal diameters , though with the age factor that could be due to wear from poor cleaning practices or internal bulging from bad ammo or blockages.
When theres a similar complaint about a four or more groove bore the cause is usually more obvious.

I do believe the two groove barrel can stand more abuse and continue to give a reasonable level of accuracy.

[swheeler]

Bench rest shooter with 35 pound rifles can do as they like.
I've always shot tighter groups from the sitting position with elbows braced to inside of thigh or knee than from a shooting bench or other solid rest. Thats with rifles of aproximately ten pounds or less.
Were I using a heavy weight custom long range target rifle I might do better from a rest.
I do as well from the prone position, but its uncomfortable for me.

Far as I can tell no maker of target grade barrels uses a two groove bore. Some three groove matchgrade barrels are offered, and three groove barrels have a long history in the U S dating back to early .50 Trapdoor Springfield days when cast bullets were the norm.

From what I've read on the subject WW 2 wartime four groove Springfield barrel had a lower standard of accuracy than earlier manufacture four groove barrels. In 1916 any thing over 2 MOA on four of the first five shots fired through a new barrel was unacceptable.
The rifle with four groove bore used as a control when testing accuracy potential of the two groove barrel was only giving 3.5 MOA groups.
Its entirely possible that the four groove barrels coming off the line at that time were inferior to the two groove barrels, at least the two groove barrels from that first batch.
If theres twice as much work being done to rifle a barrel then theres twice as much chance of screwing something up.
I've run across complaints of two groove bores that varied in internal diameters , though with the age factor that could be due to wear from poor cleaning practices or internal bulging from bad ammo or blockages.
When theres a similar complaint about a four or more groove bore the cause is usually more obvious.

I do believe the two groove barrel can stand more abuse and continue to give a reasonable level of accuracy.

??? I thought they were broached/ broach cut barrels? twice what, one pass 2 or 4 groove, done.