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November 29, 2015, 02:14 PM | #1 |
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Lee-Enfield (or ammo) problem.
OK, a question or two on an odd pair of incidents today at the range.
The Bubba’d No5 ("jungle carbine") I rescued has only been fired with my handloads. Its been checked for lug engagement (its fine even & about 40% on both). Headspace it passes both the Okie NO-GO (0.067") & obviously the FIELD (0.074"). The bolt head is a No “0”. Not surprising as the bolt & receiver serial numbers match. Checking the FP protrusion, it mics to 0.048”, a little long, but within tolerance for the 0.040”~0.050” range listed. Weather at the range was cool & damp with a light mist so there were no temperature concerns. Working up a load for this rifle using virgin R-P brass & CCI #200 primers has functioned perfectly with absolutely no issues. FWIW the loads were 150 Gr & 174 Gr Hornady & Sierras run to moderate pressures & velocities. This is a 60 or so rounds in a few lots, as the load was being developed. Until today these were the only loads run through this particular rifle, but today I tried some S/A MilSurp “7.7 ~ R1M3Z ~ A81” ammo which I’ve previously used other rounds from in the no4MK2 with no problems at all. I immediately started getting odd results. On round 3 (1&2 were fine) something struck my thumb, which is odd! Looking at the action after firing, but before cycling, the bolt it was fully cocked, even though the trigger had been pulled & the striker detonated the cap & fired the round. ? Hmm, odd. Once I de-cocked & opened the action the primer was pierced. I assume the venting gas actually forced the striker back & the sear caught the bent! I stopped & checked everything out & cleaned the mess as the gas had vented through the ports in the bolt head & receiver ring. The next 3 rounds were normal, then another pierced primer. Finally I fired & the bolt attempted to open fully! This was NOT the usual 1/8~1/4” of bolt lift, but it almost unlocked completely the handle was rotated about 65~70 degrees & I could see about 1/16” of the case Past the rim in the breech the bolt & head had moved back so far! There were also random incidents of stiff unlocking of the bolt. Needless to say that was it for the day. So far all I can find wrong is the pin protrusion being a little long & the radius being a little tight. However the excessive unlocking has me concerned. Has anyone else had a similar experience with pierced primers having enough gas venting to re-cock the striker fully & rotate the bolt 60 or so degrees? The primers were not slightly pierced but a full disc was punched out of the primer cup.
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November 29, 2015, 10:59 PM | #2 |
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So-called "pierced" primers are not caused by excess firing pin protrusion, but by too light a firing pin spring or a too light weight firing pin.
The reason is that when the firing pin dents the primer and ignites it, the first thing the forces inside the primer try to do is to blow the dent back out. The firing pin has to be heavy enough or the spring strong enough to resist that. If that is not the case, the pressure inside the primer will blow part of the primer back into the firing pin hole in the bolt and the result will be a "pierced" primer. Some folks think the cause is too strong a firing pin spring, so they weaken it further, resulting in more "pierced" primers, so they weaken the spring still more until the rifle won't fire, which does solve the problem. Incidentally, those little "discs" don't just go away; they go somewhere, which is inside the bolt where enough of them will get in the way of the firing pin and result in the rifle not firing. Jim |
November 30, 2015, 05:04 AM | #3 |
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Not always the case. A F/P that is too long WILL blow the primer, but it is usually very hard to open the bolt. What is left of the primer will weld around the pin and into the F/P hole.
I don't know is the Mark 4 the same set up as a Mark III ? Are the threads good on the bolt where the head screws on? |
November 30, 2015, 11:04 AM | #4 | ||
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Striker spring tension matches that of my other no4 & is within specs.
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*Update with pics* This is a Q&A from another site who are also helping me out, but its stuff I hadn't thought of initially. * All dimensions are the averages of several reads at different points round the circumference of 3~4 rounds. Fired case neck OD of the S/A R1M3z in the No4 0.3435" In the No5 0.3460" so the No5 is looser. Chambers: the No4 Mk2 is tighter & with less "generous" shoulder area. Rim thicknesses: My (R-P) reloads are 0.0590" The R1M3Z is 0.0620" so the S/A is a tighter fit in the breech with the bolt closed. Here are the fired cases: Top row (blue rectangle) is my reloads fired in the (problem?) rifle with no side effects. Middle row (green rectangle) is R1M3Z rounds from the same lot fired in a different rifle with no problems. Bottom row (red rectangle) is the fired R1M3Z cases some of which exhibit pierced primers & a stiff bolt lift. (All images (c) Wogpotter 2015)
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Allan Quatermain: “Automatic rifles. Who in God's name has automatic rifles”? Elderly Hunter: “That's dashed unsporting. Probably Belgium.” Last edited by wogpotter; November 30, 2015 at 12:49 PM. |
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November 30, 2015, 02:05 PM | #5 |
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A Bubba’d No. 5 is most likely a No. 4 Rifle.
Serial numbers matching does not mean the bolt head is original to either the rifle or the bolt. The only part that matters is that the bolt didn't close on the N0-G0. No reason to check with the field if it doesn't. Since you're not having issues with your handloads, but are with the milsurp, the ammo being the cause is a safe bet.
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November 30, 2015, 06:12 PM | #6 |
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Nope its an actual 4-digit NO5 Mk1 verified as such.
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Allan Quatermain: “Automatic rifles. Who in God's name has automatic rifles”? Elderly Hunter: “That's dashed unsporting. Probably Belgium.” |
November 30, 2015, 08:34 PM | #7 |
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My 1942 Maltby had a similar problem. The lugs on the bolt body were worn. I changed the bolt body and the problem went away. I still don't shoot that one too often, but I have 9 Lee-Enfield to choose from.
Before and after pictures TK |
November 30, 2015, 09:04 PM | #8 | |
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http://thefiringline.com/forums/show...1&postcount=26 August 1993 reloads. Anyone shooting older? http://thefiringline.com/forums/show...=high+pressure I would recommend that you stop shooting this ammunition before it damages your rifle. Pull the bullets, dump the powder, examine the cases for signs of corrosion. If the cases are pitted, throw them out. If not, maybe you can reload them with new powder and the old bullets.
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December 1, 2015, 09:43 AM | #9 |
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If the powder is degraded why don't I get the same problem in other rifles?
I pulled down a couple of them to check the loads out & there's no indication of deterioration, no discoloration or odd smells either? Accuracy is (surprisingly) good, ignition is consistent & immediate & velocity & deviations are well within limits as well.
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Allan Quatermain: “Automatic rifles. Who in God's name has automatic rifles”? Elderly Hunter: “That's dashed unsporting. Probably Belgium.” |
December 1, 2015, 11:02 AM | #10 |
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How tight is the firing pin hole? In your picture, the red group has a donut shape in the primer around the firing pin indentation. That makes make think you may have a over sized firing pin hole in the bolt head.
It also looks like the milsurp (green and red) are hotter than your hand loads. Do you have picture of the pierced primers? -TL Last edited by tangolima; December 1, 2015 at 11:33 AM. |
December 1, 2015, 01:12 PM | #11 | |
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Yes the handloads are backed off 100 FPS from the military load. The R1M3z clocked through a Chronograph at a standard 2450 FPS, but I download the handloads a bit as that's a sweet spot for accuracy. The bottom right 3 are the pierced primers. FWIW the handloads are Boxer & the MilSurp are Berdan primed. They also show the same pressures & velocities in the "control" No4 Mk2 rifle, but without the piercing.
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Allan Quatermain: “Automatic rifles. Who in God's name has automatic rifles”? Elderly Hunter: “That's dashed unsporting. Probably Belgium.” |
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December 1, 2015, 01:36 PM | #12 | |
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Have some German and Austrian 8X56R from 1938. Have some Greek 8X57 dated 1940. Have a bunch of Czech 8X57 and some Russian 7.62X54, both with headstamps from the late 40s. All of which shoot fine. Last edited by emcon5; December 1, 2015 at 07:51 PM. |
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December 1, 2015, 04:38 PM | #13 | |||
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-TL |
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December 1, 2015, 05:10 PM | #14 | |||
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Maybe because of different rifle. Let me use an analogy: the feather that broke the Camel's back. The poor Camel was loaded up to the point it only took a feather to buckle the knees and break its back. Different rifle was the feather. Quote:
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Never measured the velocity with known bad powder, so what did you get with your 303 Brit?
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December 2, 2015, 10:49 AM | #15 | ||||
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This was from a test I did for different reasons, but it has the load velocities, spreads & so on. Quote:
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