"Double firing"

[Joseph Scott 0]

I had two inquiries about double firing recently. Thought I would pass on my suggestions and solicit input from others.

First check that the little clip on the firing pin is in the locator groove. It should not move up/down the length. FP return spring should have one end hooked under the clip. If the clip moves position, lightly peen the sides right over each wing of fp to force metal into slot. Do not use grease on firing pin, only oil.

Second check the trigger group and look at the small cross pins right over the trigger. They should be equal on both sides and staked to prevent movement. I found one which had slipped sideways and dropped one end inside housing. This allowed sears to improperly disengage. These small pins are extremely important to be staked on each side.

Third, be sure firing pin stop is in the bolt. Some are not retained and easy to drop out when assembling bolt. Please share any experience you may have.

[LoboMike 0]

Joe,

I'd also add be sure the shooter is not "limp wristing" while firing. My sporter can produce a double by "bump firing" if the rifle is not secured to the shoulder. I did check all you suggested & it was as spec'd.

Also, did you get my private email about restoring the sporter to mil configuration?

Mike

[Alasdair MacDonald 0]

Joe, I had extensive experience with rifles doubling. I Have two Johnsons. One is a military and the other a Windfield. I also have an extra barrel in 7X57mm. I first experienced doubling when using the 7X57. It especially did it with 139 grain bullets and even the heavier. It was more consistant with the light bullets. I began replacing every single part with new or new after market parts to see if I could get the doubling to stop. I swapped trigger housings, every single part in the trigger housing, bolts (they all had the firing pin spring attached and in the proper position with zero movement.) I even doubled up on the firing pin springs to increase the resistance and check the inertia of the firing pin and keep it from slam firing. Primers on casings that doubled had only a slight dimple on them and not as severe as the fired rounds, but the dimple was sufficient to set off the primers. As you know, generally military primer cups are usually thicker and therefore take a stronger hit to set them off. I pulled military bullets to use the military powder and primers and replaced them with the lighter 139 grain bullets. Primers and powder did not seem to make any difference, but they did double with the light bullets. The only way I got the rifle to stop doubling was to put back into the recoil tube the 3/4 inch too short recoil spring which caused the bolt to return to battery more slowly and therefore less inertia and therefore the bolts firing pins setting off the rounds was checked. I recreated this problem with both of my rifles. It appears that with the new not yet tired springs being compressed during recoil, causes the bolt to go forward faster and the springs and primer cups can't check the increased celerity. I made some posts on this a few years ago and still have my copies of my research on this problem. Altough you get some evil eyes from the rangemaster, it was kind of neat and fun to shoot them this way. I told the rangemaster what I was doing and he had no problem with it. Not too cool if you are shootin a match though. Hopes this helps, cordially, Alasdair

[Joseph Scott 0]

Alasdair, certainly an influence that I never thought of. I have to think about how a slower recoil would be effected by lighter bullets when the gun is designed for M2 ammo. Also have to think about what happens if barrel has not returned to forward position in time and is pushed forward by bolt. A rare event that is hard to solve.

Lobo, I have had some e-mail problems due to someone sending me a huge picture which clogged my dial-up email. At this time, I am not doing any restorations. Installing a CNC mill and rearranging shop plus have a large backlog of small parts to make. Perhaps in 3-4 months.

[Alasdair MacDonald 0]

Joe, a slower recoil is accomplished by the lighter bullet not being able to compress the recoil spring back any farther than to cycle the action. (Newton's Third Law of physics) Since the recoil spring is not so compressed, its forward response is slower with the tired spring and therefore lacks the enertia to overide the firing pin spring and cause a slam fire. It can get a little involved sometimes can't it? All the best Joe, cordially, Alasdair. Lets see if we can pick some other brains out there.

[Joseph Scott 0]

Another possibility occurred to me. I wondered if the sear bar was not catching the hammer and it rode the bolt home causing ignition. I don't normally disassemble trigger groups if they seem OK. I stripped one which I considered normal and found crud under the bar, in the trigger return spring, hammer spring and the various pivot pins. After complete cleaning and oiling, it was obviously faster acting, harder hitting hammer action and smoother than another "normal" one. I now consider this a possible cause and suggest disassembly/cleaning the trigger group. Be careful of a small plunger piece in the trigger return spring, I lost mine and took 45 minutes to find it. It is in the end of spring against the trigger to take wear. I believe this faster return of the sear bar will insure catching the hammer hooks. Be sure to restake the pins. Not sure if this is a cause of doubling but it changed my mind about disassembly and cleaning trigger groups.

[TomW 0]

In 2002, when Allistar, Joseph, Walt & others were discussing doubling, I was experiencing the same problem.

I took their advice & put in a fresh recoil spring and firing pin spring. The old recoil spring measured 10 1/2 inches in length.(new should measure 12 inches)

This cured the doubling in this rifle.

In other rifles, I have found recoil springs with lengths of 11 1/4 and 11 3/8 inches, which were replaced, to play it safe.

[Alasdair MacDonald 0]

Good idea Joe, that could also be a possibility. The genius of Mel Johnson was the bolt rotating 20 degrees to lock up before the hammer could engage the firing pin. If this doesn't happen, then you could get an eight lug looking face. I also had a rifle that the machine work was too rough and when the double stage hook was to be caught by the sear, it failed because of vibrations caused by the rough machining. As to your springs recovery, been there,done that. While attending S&W armorers school we had a real problem with mortar rounds trigger rebound recoil springs flying across the room. The instructor said," the next mortar spring that flys, that student is going to buy everyone a beer after class." We then took to covering the spring with a towel while compressing it to save our pocket books. Cordially, Alasdair

[Gman 0]

I experienced this with Ugly Betty two days ago. I went back to an old thread so we can keep all of the information together. Upon disassembly, I found that the firing pin ring (part #77A) which keeps the firing pin spring in place was loose and had slid backwards and jammed causing the firing pin to stay at its most forward position.

I reassembled the bolt, firing pin, and locking cam with the fp against the stop. What I found was as the bolt is rotated by the locking cam the firing pin starts to protude from the bolt face. I'm sure this is what caused the second bang. I put the ring back into position and crimped it into place. Seems OK now.

I hesitate to call this a slam fire as others have in similar cases because the bolt was closed and at least partially locked. In my opinion, a slam fire is one that occurs out of battery (Garand-read about it, M14-saw it happen). The way Mr. Johnson designed his action, this will not occur. I found that even with the firing pin held at its most forward position, it does not protude through the bolt face until the bolt is closed and is being locked into place by the locking cam. This underscores the importance of not shooting your rifle without the bolt stop in place.

To quote from the Johnson instruction manual, Section II, paragraph 2e, ". . . By camming action of the firing pin stop, the firing pin is not in a position to strike the primer of the cartridge until the bolt is closed."

BTW, I got the old gal down to under 1" MOA at 100 yards! She's a great shooter.