Home Forums Reloading Big Game Rifles POP! goes the primer.

I blew a primer yesterday with a really mild load, and I'd like to learn the lesson the experience is trying to teach me.

I have three .303 Lee Enfields; let's call them A, B and C. I neck-sized some cases that had been fired in A, reloaded them with a really mild load, and fired them in B and C. The chamber in rifle A must be a little larger in some dimension(s) than the chambers of B and C, because it required some mild force to close the bolt on the cases.

Everything worked fine with five shots in rifle B. However, I only made three shots with rifle C. All three shots required a yank to open the bolt. The primer was a bit flattened from the second shot. With the third shot the primer fell out of the case. Subsequent shots using new unfired cases with the same load in rifle C gave no problems or pressure indications.

My working hypothesis is that forcing the bolt closed on the oversize case somehow scrunched the case and caused the bullet to be effectively clamped in the case neck, resulting in the excessive pressure.

I'm open to criticism of this analysis, and would appreciate your comments.

Many thanks.
--Bob

BullShooter: Is it possible that with the previously fired cases, you seated the bullets for an overall cartridge length that was appropriate for rifle A, but that rifles B and C do not have such deep throats as rifle A, so that the cartridges were too long for B and C, and were jamming the bullets into the lands when you closed the bolt? If so, that could cause excessive pressure.

if i remember right lee enfields are well known for developing excessive headspace. so common was the problem that the armorers had 3 or 4 different size bolt heads so that as headspace grew you just changed out the bolt head to take up the slack. do you suppose that #1 has "looser" tolerances at this point than the other 2? they are great old rifles though. i have a sporterized No 4 Mk 1 made here in the states by Savage that i just love.

Rattler

Agreed,
Too much headspace.
Mike

(Long winded post follows, but inquiring minds want to know...)

Many thanks for your replies. I try to be conservative, seeking accuracy and staying far from high pressures in these old rifles. That is why this incident is upsetting and I don't want just to shrug it off.

BigBrass-
I checked on your suggestion that the bullets might be jammed into the rifling is pertinent. I don't think that is the problem. (A) The bullets were seated to a maximum overall length cartridge length of 3.075 inches, which is the recommended OAL in the Sierra manual for their 180-grain spitzer, which I was using. (B) Since it is possible that the rifle has a throat shorter than it should have, I checked that with my homebrew Stoney Point-like gauge. This showed that the OAL needed to put that bullet into the lands is 3.235 inches. I was probably a good 0.15 inches away from that problem. (C) I seated the bullets in the new brass cases to the same OAL as in the used brass, and encountered no pressure problems with the new brass.

rattler and mikeone-
Your suggestions about headspace problems are also relevant, so I checked on that too. According to SAAMI specs published in the NRA's "Handloader" book, the headspace dimension for the .303 British should be between 0.064 and 0.071 inches. Cartridge rim thickness can vary between 0.054 to 0.064. I think this means the allowable slop between the case head and the bolt face can be 0.000 to 0.017 inches. A rough measure of this space on the problem rifle is 0.010, so I don't think that caused the problem. The W-W brass that I used measures 0.060 +/- 0.002 in rim thickness.

From reading Hatcher's discussion of headspace (again in the NRA "Handloading" book), I understand that excessive head space results in stretching and separation of the cartridge case near the head at normal pressures. It does not seem to cause excessive radial expansion of the case head so that the primer falls out, which is what happened to me.

And again, if headspace was a problem, it should have shown up when I shot the loads assembled in unfired brass.


rattler-
You're almost certainly right that the chamber on the first rifle is looser than that on the other rifles. I assume that is what made the fired brass from the first rifle difficult to chamber in the other two. What I'm trying to figure out is how that could have caused high pressures.

In effect, headspace was zero as a result of the case being oversized and forced into the chamber - there was no space between the bolt face and the case head. I'm hoping somebody can explain how forcing a slightly oversized case into a chamber can lock the bullet into the case neck, or otherwise produce excessive pressure.

The load was really mild: 37.5 grains of Reloader 15 with the 180-grain bullet. Alliant lists 43.7 grains as the maximum load with a 180-grain Speer bullet.

Lee Enfields are notorious for case stretching, even when headspace is correct. The military chambers are reamed with shoulders that allow a lot of forward expansion of the case on firing, which is why Steve Redgwell on 303british.com recommends neck sizing only. (The English seemingly invented mild Ackley Improving before Ackley was born!) The rear locking arrangement on the Lee Enfield bolts also permits case stretching. Even with neck-sizing exclusively, I can only get about 4 reloads from the R-P cases, and 6 from the heavier W-W cases before I have to discard them to prevent head separations.

In my parts box I gave Enfield bolt heads labelled 0, 1, 2, and 3. Rifle C that cause the problem came with a 0 bolt head, the shortest, but the rifle doesn't appear to have problems in that regard.

So, thank you for the suggestions, which I appreciate. I know about the warnings not to use neck-sizing for reloading for semi-auto rifles. I don't recall reading any warnings about swapping neck-sized brass among bolt rifles.

Thanks, and if there are other ideas, please post them.
--Bob

Hi guys. I may be able to help here.

Primers that back out of a case with a mild load is not uncommon. I should also say that it can happen in rifles of any cal.

There was no high pressure. It has to do with the chamber size, or, in the case of a rimmed cartridge, the recess into with the rim fits. There is a tolerance of a few thou. Call it a bit of extra room or tolerance allowed when building a rifle. The firing pin strikes the primer and the cartridge moves forward within that extra space, the primer ignites and ignites the powder. The gas pressure generated in the case acts equally in all directions and begins to push the case (and primer) rearward.

The primer partially unseats and at virtually the same time, the case moves rearward, pushing a partially backed out primer against the bolt face. The primer flattens a bit.

When a primer pocket is loose, the primer will more easily slide out. So, what I suspect is that the primer pocket was probably expanded and the pressure generated simply pushed it out. In this case, You could check the headspace, but since you didn't have this problem with new cases, it seems to me that the blame lies with the reloaded case.

Safe Shooting! <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />
Steve Redgwell
303british.com

Without, of course, actually seeing your case, I'm inclined to think you had too little pressure rather than too much. Did you check to see if the pocket was actually expanded?

After a similar problem, I attributed some of the fault to headspace, and bought a RCBS Precision Mic to set the FL die to .002 or .003 shoulder setback specific to my chamber, rather than to SAAMI minimums. It improves case life by minimizing how much the case needs to be worked.

How hot was the action when you fired the shot? Another step was to move entirely to using less temperature-sensitive powder, such as the Hodgdon Extreme line. Using "standard" powder, I observed pressures climb alarmingly, even though successive shots were from the same load lot. I attributed that to the case (and thus the powder) absorbing heat from the chamber. Ambient heat, whether from outside air or from the rifle's chamber does increase cartridge pressure. I'm told that's the main reason competitive shooters chamber a round as late as possible.

Finally, I stopped using neck sizing dies. Another way to interpret the difficulty with closing the bolt on a round is wear on the lugs and action - that wear was changing my headspace. Using a quality die (mine's Forster), I get consistent headspace, and a concentric neck, and no difficulty closing on a cartidge. The only downside is the need to lube the case each time.

When I do neck size a case that's previously been set back only .002, I will consistently see flattened primers from even mild loads. From this I conclude that my cartidge needs some headspace, and that it isn't present in a neck-sized case.

Jaywalker

It is possible that rifle C simply requires that brass be trimmed to a shorter length.
"All three shots required a yank to open the bolt"
"With the third shot the primer fell out of the case"
Considering that this rifle headspaces on the flange of the cartridge, this definitely sounds like excessive chamber pressure to me. It could have been caused by case necks which were longer than the chamber. This situation would cause difficult chambering as the neck of the cartridge is crimped into the bullet. Then excessive resistance to initial movement would cause pressure spikes. I would compare the length of the high pressure brass to that of the new unfired brass with a good set of calipers.

Thank you for all the suggestions about the reason for the popped primer. Your ideas prompted me to go do some more measuring.

Here are some case head measurements that might help in figuring out what went wrong. I was using W-W cases, which have a shallow, narrow groove immediately in front of the rim. With calipers I measured diameters just in front of that groove. Measurements are in inches, given as average of "n" cases. Standard deviation is in parenthesis.

1. New cases
0.4500 (.0001) n=10

2. New cases fired once in Rifle A
Same load that popped primer in Rifle C with 4X fired cases
0.4501 (0.0001) n=10

3. New cases fired once in Rifle C
Same load that popped primer in Rifle C with 4X fired cases
0.4518 (0.0004) n=10

4. Cases fired 4X in Rifle A - Assorted loads
The case with popped primer came from this batch of cases
0.4506 (0.0003) n=10

5. The problem cases: fired 4X in Rifle A (as 4 above), then neck sized and fired in Rifle C, using same load as in 2 and 3 above.
Shot #1: 0.4509
Shot #2: 0.4541
Shot #3: 0.4582 (popped primer)

As I stated in a post above, the load was 37.5 grains of Reloader 15 with a Sierra 180 grain .311 bullet, CCI #200 primer. I called this was a mild load, based on a maximum load of 43.7 grains as published by Alliant.

What I think these measurements indicate:

A. The load appears to be really mild in Rifle A. There is no apparent head expansion.

B. The same load is not so mild in Rifle C. Expansion of 0.0018 in the web is considered excessive by some.

C. The cases that had been fired 4X in Rifle A showed probably normal expansion.

D. The case with the popped primer had 0.0073 expansion. I think this shows that the cause of the primer coming out was indeed high pressure, and not one of the usual odd things that can happen because of loading to low pressures.

I talked the problem over with one of the tech support persons at Sierra. The Sierra maximum load for their 180-grain bullet is 38.5 grains of Reloader 15 using W-W cases with a Remington primer. Sierra worked up to that maximum not with a pressure gun, but with an Enfield No 4 Mk 2 watching for signs of pressure. I'm not sure why their maximum loads differ by 5+ grains; Alliant used a Speer 180-grain roundnose bullet, which may account for some of it.

Some replies to helpful persons:

Steve Redgwell-
Your jumping in is appreciated. As I think the case head measurement shows, there really was high pressure involved. I've seen the riveted primers produced by low pressure loads in other cartridges. In this instance though, the primer was well and truly blown. I'm sure you're correct in stating that the problem was made worse by using the 4X reloaded case.

OK Shooter-
Most of this post was prompted by your suggestion to check whether the primer pocket was really expanded. Yes, it was. Very. Thank you.


Jaywalker-
The action was pretty cool when I fired the shot that popped the primer. Only two shots had been fired previously. The interval between these three shots was several minutes, which I spent moving the target from 25 to 50 to 100 yards. Also, the powder was Reloader 15; Mule Deer has noted several times that recent lots of this powder respond to temperatures like Hodgdon's Extreme powders.
Your suggestion about avoiding neck sizing because of possible wear to lugs and locking recesses is an interesting one. On these old rifles I try to keep these areas free from dust and grit, and lubricated with a good grease. The choice between neck vs FL sizing in the old Lee Enfields is a real problem; .303British.com has lots of good pertinent thoughts.


Idaho Shooter-
It's possible that the neck needs trimming. However, standard case length for the .303 is 2.222 inches; before I loaded the 4X-fired cases, I trimmed them to 2.205. The case that popped the primer measured 2.212 when it came out of the chamber. I'll make a chamber cast of Rifle C when I get a chance.


My tentative overall conclusions about the incident:
1. The load was mild in Rifles A and B, but it was at or just above max in Rifle C.
2. Switching the fired case from Rifle A to C caused something to push pressure way up. Perhaps the forcing of the case into the smaller chamber of C cramped the bullet in the case neck.

Thank you again.
--Bob

I might of missed it in the reading somewhere, but do you have the same problem when you full length resize?

Or with factory/surplus ammo?

Strider-
You ask good questions that bear directly on finding out what happened.

A couple of days after the primer popped on me, I bought a box (18 US $$- Ouch!) of Remington 180-grain round-nose factory loads, and fired three rounds in each of Rifles B and C. There were no obvious pressure signs from either riifle. Unfortunately, I failed to measure the case heads before firing. The R-P cases show much case-to-case variation before firing, unlike the W-W cases, so it is difficult to make useful head measurements after firing from only three cases.

I have not tried full-length resizing for any of my .303 rifles; in fact, I don't have a full-length .303 Brit die. However, when I felt the resistance to closing the bolt of Rifle C on the neck-sized cases from Rifle A, I did wish for one.

I would guess that the primer would not have popped had the case been full-length sized. I did not loosen any primers with the same load in new cases, and resized cases should have the same or greater interior capacity, with similar pressures.

If you've read or heard any warnings about dangers caused by swapping neck-sized cases between rifles, I'd really like to learn about it.

Thank you.
--Bob

Well I'm packed for moving and my references are put away, but ...

I remember reading on more than one occasion that you should restict "neck sizing only" for use in the same chamber again. Chamber dimensions vary from rifle to rifle, and can cause problems like these.

I have a similar issue with an old .300 savage. The chamber is slightly long (headspace) from age. I can set my full length die to only resize the neck and have no problems - in fact better accuracy. I also seat the bullet about 1/4 turn off the lans. This ammo works fine in my rifle, but will chamber hard in a tighter rifle.

Try a dry erase marker on the bullet and shoulders of a neck sized only round from "A" and chamber it in the rifle in question. Remove the cartridge without firing the rifle and examine. I bet you will find that the bullet is being pushed into the rifling and/or the shoulder is being compressed.

I've actually seen a bullet pulled from the case and stuck in the barrel when reopening the action on an instance like this.

Try either getting a full length die or keep your brass sorted for each rifle separately when you neck size and I bet your problems will go away.

best of luck