No. 4 Mark I splits cases

Joe Boleo · Posted: Tue Sep 20, 2011 3:16 pm Post subject: No. 4 Mark I splits cases

I picked up a mint No. 4 Mark I .303 Enfield from WWII at a gun shop and took it to the range. The first reloads were S&B cases with 150 grain .311 bullets and moderate charge of IMR 4895. Accuracy was great and two of the S&B cases had complete head separations. I am sure glad the Enfield is gas proof. I had no idea of the case separation until I worked the bolt. The rim came out and the case body was still in the chamber. I used a loaded round to go inside the case and extract the case from the chamber. Eight more S&B cases worked fine. The tenth S&B case separated and I removed it. The reloads were loaded once or twice and were neck sized only.

I ran some reloads with Federal cases and everything was fine. I intend to replace the number 1 bolt head with a number 2 and see what happens. At this point I do not know whether it is a gun problem or an ammo problem. That was my experience at the last range session. Take care...
Joe

Aloysius · Last edited by Aloysius on Wed Sep 21, 2011 4:05 am; edited 1 time in total

excessive headspace...
or you replace the first part of the bolt (the come in different lengths), as you already mention,
or you fire-form the case and make sure your round is touching the bolt BEFORE it's fired. To do this you put a small rubber O-ring on the neck of the round, just before the shoulders and then put the round in the chamber.
Afterwards you only neck-size ofcourse! (till the complete round is difficult t0 chamber, then you full-length-size a little, just enough the put the shoulder a little back till it fits the chamber again)

slimjim · Posted: Wed Sep 21, 2011 3:29 am Post subject: Re: No. 4 Mark I splits cases

Aloysius wrote:

excessive headspace...

+1. Let us know how it turns out, Joe. My experience with Federal cases is they are thicker and softer brass. Maybe they could absorb the excess head space without splitting.

Pumpkinslinger · Posted: Wed Sep 21, 2011 4:31 am Post subject: Re: No. 4 Mark I splits cases

I'll follow this thread with interest! I've got a SMLE No. 1 Mk III* and a No. 4 Mk 1* that I'll eventually handload for. While firing the No. 1 some time back I had a military surplus (Greek?) case split and that made me a little wary of the rifle, and ammo. I figure I'll start with new brass and reduced loads whenever I finally get around to that project. I'm wondering if a load using 125 grain bullets and Trail Boss powder might be a good way to fire form some brass for measurement.

slimjim · Posted: Wed Sep 21, 2011 5:23 am Post subject: Re: No. 4 Mark I splits cases

I'm not sure that light loads are a mitigation for excessive head space to prevent brass split. I was using light loads on my .45-70 and I still split a case due to excess headspace. The firing pin will always drive the case forward unless you use a trick like Aloys suggested.

SingleShotLover · Posted: Wed Sep 21, 2011 5:43 am Post subject: Re: No. 4 Mark I splits cases

I would have to lean toward a head-space issue too, though S&B has had the occasional run of brittle brass.

Another way to make your brass safely fit chambers that have slightly excessive head-space (or just a slightly over-sized chamber) is to seat the bullets to just touch the lands (if possible) over moderate powder charges. The bullet holds the case firmly against the bolt-face and, upon firing, the case expands forward (rather than to the rear which thins the web and causes case failures) causing the shoulder to conform to the chamber dimensions. Then set your normal sizing die to barely bump the new shoulder position and load as normal.

I know the .303 is a rimmed case, but you will find that rim thicknesses vary and making it head-space on the shoulder will work much better while probably improving over-all accuracy.

I had to do this with one of my Contender barrels in .35 Remington that has an excessively long chamber (common with the .35 Rem) that resulted in miss-fires. Once the brass fit the chamber and I adjusted the sizing die accordingly the miss-fires went away and accuracy improved. The brass also lasts a lot longer now, which eliminates a common complaint with the .35.

Ominivision1 · Posted: Wed Sep 21, 2011 6:32 am Post subject: Re: No. 4 Mark I splits cases

I agree with all that what said above, my only suggestion is have you tried factory loadings to see how the cases hold up?

44marty · Posted: Wed Sep 21, 2011 8:09 am Post subject: Re: No. 4 Mark I splits cases

SingleShotLover wrote:

I would have to lean toward a head-space issue too, though S&B has had the occasional run of brittle brass.

Another way to make your brass safely fit chambers that have slightly excessive head-space (or just a slightly over-sized chamber) is to seat the bullets to just touch the lands (if possible) over moderate powder charges. The bullet holds the case firmly against the bolt-face and, upon firing, the case expands forward (rather than to the rear which thins the web and causes case failures) causing the shoulder to conform to the chamber dimensions. Then set your normal sizing die to barely bump the new shoulder position and load as normal.

I know the .303 is a rimmed case, but you will find that rim thicknesses vary and making it head-space on the shoulder will work much better while probably improving over-all accuracy.

I had to do this with one of my Contender barrels in .35 Remington that has an excessively long chamber (common with the .35 Rem) that resulted in miss-fires. Once the brass fit the chamber and I adjusted the sizing die accordingly the miss-fires went away and accuracy improved. The brass also lasts a lot longer now, which eliminates a common complaint with the .35.

Great post, thanks. Worth repeating.

Gil Martin · Posted: Wed Sep 21, 2011 3:04 pm Post subject: Re: No. 4 Mark I splits cases

I agree with everything that has been said. My experience with British Enfields has often resulted in stretched cases. Like Joe, I neck size only and have installed a higher number bolt head. I will be interested in what Joe finds out. All the best...
Gil

SingleShotLover · Posted: Fri Sep 23, 2011 5:54 am Post subject: Re: No. 4 Mark I splits cases

I remembered another trick that might work also for you. It's one most wildcatters use when working with exotic chamberings and often those who shoot belted-magnum cartridges too. It might be especially useful for those who either can't load the bullets out to the rifling (as described in a previous post) due to chamber restrictions or aren't comfortable doing so.

Preferably starting with new brass, run the case mouths over the next sized larger expander ball (in your case the 8mm would be perfect) only far enough to expand the neck without touching the shoulder in the die. Now adjust your .303 sizing die to just size part of the neck and try it in your chamber. By adjusting the die downwards by tiny degrees, you will reach the point where the case will enter the chamber with a firm amount of resistance. At that point you can lock the die in place, size the rest of your cases the same way and load your brass as normal. The slightly larger area in the neck will ensure that the round is being held firmly against the bolt-face upon firing.

Once you have fired your "modified" rounds you can then re-adjust your sizing die to just touch the shoulders of the fired brass (using the .303 expander) and your head-space will be correct for that rifle. The shoulders now match your chamber.

Starting with new or once-fired brass is best since it is less likely to be brittle. If you have to use used brass, you should anneal the case necks to prevent splitting.

Whatever you decide, keep us informed as to your progress. Good luck.

Elvis · Posted: Tue Sep 27, 2011 12:44 am Post subject: Re: No. 4 Mark I splits cases

there is heaps of good factory 303 ammo around now to choose from the above suggestions pretty much cover it all. treat your self to some factory ammo and start with new brass.somewhere out there is the info on these rifles about which mk of ammo to use in which rifle. they like 1 more tham the rest. the other thing I remember about them is the tendency to shoot different loads to different points of impact.