Homemade No. 5 - real No. 5 question

[Boone]

Hello all -

I picked up for cheap a Lee-Enf. No. 4 Mk 1 that had already been shortened and sporterized. Having a number of parts on hand from two other No. 4's I own, I decided to convert the sporter into a jungle carbine.

All in all, I am pretty happy. The barrel had to be shortened another 1 1/2" for proper length and the homemade crown is crude but seems to be functional (maybe).

I was out sighting in the rifle on the 25 yard line and every 150grain Prvi Partizan SP load tumbled. I was really bummed. I switched to 180grain handloads using Speer Hot Cor and 41.1 grains of Reloader 15 and my first three shots were touching. All handloads were perfect, all factories tumbled.

Does anyone with a real No. 5 have this problems with short, lighter bullets or is this something unique to this rifle and perhaps the crown job?

Thanks in advance -

Information

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[#5MK1]

Tumbling bullets in Enfields is a real can of worms.

Let me start off by stating that from my experience and other #5MK1 collectors.

We have never experienced this problem with any ammo in original #5s.

Tumbling was fairly common in the #4MK1 and other Enfields we bought from Century for cheap many years ago.

Then it occured only on the ones with worn crownds and certain type of bullets. Boatail vs. flat base etc.

Tumbling seemed to be related to bullet type and bore and crown wear.

I'm sure someone will chime in with more precise info. for you.

[Dave_n]

Can occur if the bore just ahead of the chamber is eroded from (and Ed Horton will love me for this!!) "corrosive cordite ammo" or more precisely the hotter burning cordite used by prior owners. I have tumbling in a Mk III due to this and Mk VIIIz ammo (boat-tailed round) but the Mk V just swallows them and gives nice round holes as no erosion ahead of the chamber. Dave_n

[Peter Laidler]

We had a saying that BSO's (broad side on's which is our way of saying tumbling) was caused by breech erosion in Brens but crown damage in rifles.

Mind you we only used factory issue ammo. Either Mk7, Mk7z or Mk8z in Brens and Mk7 in rifles although I did see a lot of 7z used in rifles. Old SMLE's did suffer from a defect called ' muzzle cordwear' that caused BSO's

This could be the start of a great informative thread and I'll pass the comments on to the ammo ballisticians at RMCS

[tenntex32]

.............It was a sporterized Longbranch that slugged near .314". The bullet I was testing, that outing, was a handpulled .310" semi-boattail that was around 170 grains in weight, from some American contract Igman 7.62x54r. What I mean by semi-boattail is that they were more of a rounded tapered base, not a distinct boattail, and not a flat-base bullet. What I found was that I got so-so groups at a lower velocity of 2200fps, then as I got closer to 2300fps I started getting flyers and as I got above 2300fps I started getting TUMBLING flyers! This may have been a combination of low quality military bullets, the .310" bullet diameter/.314" rifle barrel groove, the funky bullet base, as well as the collet style handpulling process, as they were quite difficult to pull, even after "popping" the sealant. The rifle used, during testing, shoots commercial and military flat-base and boattail bullets just fine, .3105" and larger. It just did not like the semi-boattails at normal velocities. I've since tested the same semi-boattail bullet out of 2 different M39's and found, at normal velocities, they performed O.K., nothing stellar, but no extreme flyers or keyholing. In all fairness, this could be due to the M39's having 310" grooves instead of .312" or larger, like the Brits.

Dale

[Bruce_in_Oz]

I am looking at a drawing for the barrel for a SMLE (No1 Mk3*) sadly, undated but it is sheet 2 of 4 of A.I.D. 1318A. Refer to Specification S.A. 435A

S.A. 242 is the spec for the Mk1 SMLE, 1903, and S.A. 462P is the 1939 spec for the No.1 Mk.3, 14 December 1938, so it is probably from sometime in the 1930's.

Right there in black and white it gives the bore and groove specs:

Dia of Bore: .303" Accept, .305" Reject.
Dia of Groove: .313" Accept, .319" Reject.

What is known around here as a "racing fit" to the bullet.

I suspect that bullet and barrel relationships were founded on principles established in muzzle loading days and changed very slowly. Boot a paper patched lead bullet in the backside with a few thousand p.s.i. and it will expand into the grooves. Ditto, hit a military style, jacketed flat based bullet with 45,000 psi plus and it will also expand.

You have found out the essential truth about military firearms: they are built around the ammo. When you start using bullets with jackets closed at the tail, the expansion is a lot less, radically less with boat-tails.

Military barrels are (with some exceptions), not match barrels. Check out the specs on a Finn M1939 or a NM M-14 barrel to see a different approach.

Furthermore, When the Brits went from the Mk6 ammo to Mk7, lots of things happened.

The projectile had to be a lot lighter, otherwise there would be no velocity advantage. Making it pointy at the front helped, but there was another catch. The loaded round had to function in all service weapons without major mechanical modification. The only way to make a lighter projectile of the same length was to cheat the ballistic coefficient; hence the little aluminium or bakelite plug in front of the lead core.

All of this creates a bullet with its centre of mass well to the rear.

Further, according to Greenhill's formula, it is the length, rather than the weight of the projectile that is critical in determining ideal twist rate. So, the 174gn bullet had to be spun at much the same rate as the previous projectiles. But, with the center of mass being a lot further back, the tendency to precess (fly in a wobbly spiral around the nominal trajectory) is increased. This is why the old-timers talked about the bullet "going to sleep" at longer ranges. It takes flight time for the precession to minimise, which is why some holes on targets at 100-200 yds sometimes look a bit odd.

Mk8 boat tailed projectiles are essentially the same length as a Mk7, but, the forming of the boat tail and deleting the plug gave us a 180gn bullet. Again, loaded rounds are much the same length; absolutely necessary for reliable feeding in machine guns. The boat tail, however, reduces the tendency to expand into the bore and also allows greater gas bypass and consequent throat erosion, especially in max. spec barrels. An attendant problem is that the forming of the boat tail reduces the bearing surface of the bullet. If the barrel is over sized and/or has bad throat erosion, the boat tailed bullet may start down the barrel off-centre and at a slight angle.

So, if you have a .303 barrel with lots of miles up, boat tails are not recommended.

[Bindi2]

Bruce in Ozz you are on the money. Find the right projectile and powder and the old girls can still sing with best, it is all in your hands

[louthepou]

I've read many comments about boat-tails being a bad choice for Enfields.

Only tumbling (or BSO, thanks Peter) in my short experience is with a P14 Enfield I'm currently refurbing; I was shooting .311 180gr. Just got it counter-bored about 2.5 inches, hope to shoot it soon to see the result; I've got a few bullets that are .312, and should receive a few .313 soon.

I have a No4 that had it's barrel shortened (just front of the front sight) and the crown properly redone, shoots well...

Lou

[Roshi]

I had a sporterized Long Branch No4 Mk1 and using Greek HXP ammo the bullets would tumble. I tried some 50's vintage RG and it shot fine. The barrel of this rifle was cut back to the front of the front sight base and was properly crowned. The bore was not perfect but wasn't to bad.

[Boone]

All very interesting and helpful. I guess I got lucky in that the 150g boat tails did not tumble from either my Mk1 or Mk1*. I continue to learn about shooting. I can understand how the closed base, boat tail would provide less "bearing surface" in the lands and and not expand to fit the grooves and also that the center of gravity would be different. Very interesting. Thanks again -