A3's bolt gas port

[milboltnut]

40066



I have two A3 bolts, and one gas port hole is larger than the other.

And the locking lug with the ejector slot has two dimples on it.

Could this be explained? (I understand why a bigger hole, but did Remington have problems with pressure?)

[Rick the Librarian]

The bolt with the small hole and "dimples" is a Remington M1903 bolt, not a M1903A3. The "dimples connected with the bolt stop feature, which was seen on earlier Remington M1903s.

In looking at your posts, you may not be aware that Remington produced some 348,000 M1903s before M1903A3 production got started in late 1942. Most of the Remington parts were similar to Rock Island and Springfield parts. A number of the parts you have shown in your other posts are Remington M1903, not 03A3 parts.

[milboltnut]

Ah... thanks for the heads up Rick, much appreciated.

what's the bolt stop feature?

[Cosine26]

The Bolt Stop is another solution looking for a problem. It is found on not other military rifle that I know of. If the rifle (M1903) were to be used as a magazine loader, the follower rising at the last round would stop the bolt from moving forward. When the clip of ammo was inserted into the clip slots the clip would prevent the bolt from moving forward. If the rifle were to be used as a single loader, the friction of the loaded magazine would stop the bolt from slipping forward.
BOLT STOP
In comparing my 1903 Springfield with
a friend's 1903A3, I noticed that the bolt
from my gun. has a small, round depres-
sion on the left side of the top locking lug,
and a little indentation or groove on the
front edge of this same lug, whereas I
do not see anything like this on the bolt
of the '03A3. What is the reason for this?
Is my bolt defective?-M.G.D.
Answer: The difference is caused by the
fact that the 1903 Springfield rifle has
what is called a bolt stop whereas the
1903A3 does not have this. The bolt stop
on the model 1903 rifle is a little spring
(with plunger attached) that lies cross-
ways in the receiver in a slot just behind
the magazine. The plunger sticks up
through a hole in the left side of the
receiver just under the rear bridge of the
receiver and just forward of the magazine
cutoff.
The first mention of the bolt stop and
the reason for it can be found in Appen-
dix I to the Report of the Chief of Ord-
nance for 1903, the report of the Board
which tested the experimental musket that
eventually became the M 1903 rifle. On
page 92 the Board recommended that


"Some device should be provided for
preventing the bolt, when open, from
slipping forward under the clip seat."
The bolt stop performs this function by
rising just in front of the locking lug
when the cutoff is in the "On" position
and the bolt is drawn fully to the rear.
This prevents the bolt from sliding for-
ward of its own weight, but when it is
pushed forward the sloping groove in
which the point of the bolt stop lies
cams it down out of the way and permits
the bolt to move forward.
Bolt stop in piace, as seen from the bottom of
M 1903 receiver
When the cutoff is in the "Off" position,
the bolt does not come far enough to the
rear to clear the bolt stop entirely. The
point of the bolt stop enters the round
depression on the side of the lug and
prevents the bolt from slipping forward
when the muzzle is depressed. If the rifle
was being used as a single loader, this
would keep the bolt from sliding down
and interfering with loading a round in
the chamber. Bolt of M 1903 rifle (lower) showing bevel on
front edge of left side of top locking lug and
circular recess for point of bolt stop near reCl~
of this lug. Bolt stop has been removed from re-
ceiver and lies in front of bolt. Bolt of M 1903A3
rifle (upper) shows no bevel or recess in left
side of top locking lug
In practice it was found that this bolt
stop was not actually needed and, as a
matter of fact, the marksmen at Camp
Perry and other big rifle matches found
that it was an annoyance in rapid-fire-
especially if the point of the bolt stop
plunger happened to be extra long or the
depression happened to be particularly
deep or sharp in the left lug. As a result
many marksmen stoned off the point of
the bolt stop plunger until it was in-
operative.
In later years, about the time of World
War II, it was the practice in ordnance
maintenance shops to remove this bolt
stop from the '03 rifles. When the '03A3
rifle was put into manufacture the bolt
stop was omitted.-J.S.H.

http://i116.photobucket.com/albums/o15/Cosine1/BoltStop/stopPic_zpsxyg0axjl.jpg

FWIW

[milboltnut]

the two arrows on the locking lug dimples aren't explained or did I miss it, not being understood.

[Cosine26]

The plunger(see first picture) goes through the receiver and engages either of the two detents depending upon the position of the cut off. If the cut off is in the "Off" position, the bolt travel is limited so the bolt stop engages the rear "dimple". ( Id est, the magazine is turned off.) If the cut off is in the "On" position, the Bolt can be drawn further to the rear and the bolt stop engages the front "dimple". The bolt can then pick up a round from the magazine. In either case, the stop engages a dimple when the bolt is as far as it be pulled back. The cutoff is designed to "turn" the magazine on/off. In the OFF position, the bolt cannot be pulled far enough to the rear to allow the bolt to pick up a round from the magazine ergo the magazine is OFF.
FWIW

[milboltnut]

Ok I see.. so how does it work on the A3?

[Cosine26]

As I previously indicated it is a SOLUTION looking for a PROBLEM that does not exist. The 03 A3 eliminated the bolt stop. See my original post

[milboltnut]

I know it's eliminated on the A3... so what stops the bolt? I tried looking for a diagram tonight.

[Rick the Librarian]

Actually, the bolt stop was eliminated during Remington M1903 production. I have seen early Remington M1903s with the bolt stop feature, I have seen somewhat later production with the "hole" but no bolt stop and later ones with no bolt stop "hole" at all.

[Parashooter]

I know it's eliminated on the A3... so what stops the bolt? . . .

I suspect the confusion arises from the odd name of the part - "bolt stop" - which doesn't actually serve to stop the bolt's travel. Rather its function is to discourage bolt from sliding forward (by gravity) when rifle is held with muzzle down and bolt open. This is useful primarily when rifle is being single-loaded by placing cartridge directly into chamber.

The part that actually arrests the bolt's rearward travel is called the "cut-off".


The Bolt Stop is . . . found on not other military rifle that I know of. . .

Most US Krags have a similar function provided by a pin mounted on the extractor that engages a shallow notch near the rear of the receiver. This was likely the inspiration for the '03 "bolt stop" function, though the mechanics are quite different. (Norwegian Krags have an arrangement similar to the US Krag, but slightly different in execution.)

[Cosine26]

Parashooter
I Have come to the same conclusion and you beat me to the answer.