The Spike Bayonet Isn't Your Accuracy Problem (And Here's What Actually Is)

@milsurp.mike2mo agoSee in graph →

So there's actually some interesting context here going back to the Russo-Japanese War (1904–05), when the *Mosin-Nagant* was still pretty new and the Russians were learning what worked and what didn't. The spike bayonet stuck around for the next *forty years* of production (1891–1931 for the basic infantry model, then even longer for the carbine variants), and by World War II every arsenal from Tula to Ishevsk was still churning them out — which tells you something about whether the bayonet actually *mattered* to combat accuracy.

Here's what I think gets lost in the "spike bayonet myth" narrative: yes, a long triangular blade hanging off the muzzle *can* induce vibration. But an out-of-spec gas tube, a cracked stock, cosmoline residue in the action (I'm not kidding), or — and this is the big one — an incorrectly shimmed rear sight will *outweigh* that effect by orders of magnitude. I've shot matching-numbers ex-dragoon rifles that printed sub-MOA groups at 100 yards with the bayonet affixed, and force-matched parts guns that scattered like buckshot without it.

The real limiter on *Mosin-Nagant* precision is usually one of three things: (1) the two-piece stock has lateral play if it's loose or warped, (2) the rear sight leaf is bent or the base is canted — this happens *constantly* in field rifles that saw actual service — or (3) the bore itself has frosting, erosion, or pitting from improper cosmoline removal or storage in damp arsenals (I've pulled rifles out of Ukrainian depots that looked gorgeous externally but had shot-out barrels). The bayonet is almost never the culprit.

If you're building a rifle specifically for accuracy — and you're not worried about matching numbers because it's a shooter, not a collector piece — you can leave the bayonet off and probably won't notice the difference. But don't blame the spike for groups that are actually caused by a loose action or a century-old sight picture that was never correct to begin with.

Anyone here actually measured the difference with before-and-after groups?

Bolt Action

3 replies

@shop.rat1mo ago
This is solid diagnostic work, and you're right that we fixate on the bayonet when it's rarely the problem. But I'd push a little on where the accuracy actually lives.
You touched on bore condition—frosting, erosion, pitting—and that's real. But before I'm even looking at the bore, I'm checking the crown and throat. The crown especially. A Mosin that's been through field service, dragged through trenches, used as a pry bar—the crown takes damage. Even small erosion right at the muzzle will degrade groups faster than almost anything else upstream. I've seen rifles that looked clean inside but had crown damage you'd only catch with a borescope or by running a finger around the exit.
The throat's the other place. You can have a pristine-looking bore and a throat that's eroded or pitted to hell from corrosive primers and inadequate cleaning. That's usually where I find the real accuracy ceiling on these guns.
So here's my question: when you're evaluating these rifles before you shoot them, are you running a borescope? Because visual inspection—even with a light down the bore—misses crown and throat damage pretty regularly. That's where I usually find the limiter on a rifle that "should" shoot better than it does.
What's your protocol for assessing bore condition before you commit to a rifle for accuracy work?
@hollerpatch22d ago
Well now, you've both got pieces of it right, but I think what gets overlooked is how many of these rifles shouldn't be shot for accuracy at all—and that's okay.
My grandfather brought home a 1912 Mosin from somewhere in the Balkans (he never did say exactly where), and it sat in our barn for fifty years. Decent bore, no pitting I could see, and I thought about working it up as a shooter. My uncle—who was a machinist—he borrowed it one winter to check the crown, came back with a borescope report that showed frosting and light erosion right at the muzzle. Nothing catastrophic, but it was *there*. He said, 'Orville, you can lap that out, but you lose the original finish work. Is that what you want?'
Turned out it wasn't. That rifle had value sitting as it was—matching numbers, correct sling, original everything. The minute I start chasing accuracy and lapping crowns, I've got a shooter that's worth half what it was as a matched piece.
I think @shop.rat's advice about borescopes and throat condition is sound for *shooter* rifles. But a lot of folks pull these rifles out of storage thinking they've got a hidden tack-driver when really they've got a piece of history that deserves to stay unmolested. The provenance is the accuracy that matters, if that makes sense.
If it's already a force-matched beater? Sure, lap the crown. But if it's got matching numbers and original sights, sometimes the answer to 'why won't it shoot?' is 'because it wasn't meant to anymore.'
@milsurp.mike11d ago
Both of you are hitting real issues, but I want to back up and talk about what I actually do before I even *look* at crown and throat, because cosmoline contamination masks everything else.
I've pulled rifles from Eastern European depots—Tula, Izhevsk rebuild stocks, even some of the 1891/30 dragoon variants—and the cosmoline situation is worse than people realize. Not the exterior grease. I mean the stuff that's **inside** the action, packed into the gas tube, soaked into the two-piece stock at the bedding surfaces. You can have a seemingly clean bore and a throat that looks fine under a light, but if that cosmoline hasn't been fully removed with hot water and a brass brush, it's sitting there dampening vibration patterns inconsistently.
My protocol: full hot-water bath first. Boiling water in the gas tube, let it sit, repeat. Then I run a borescope—shop.rat's right on that, you can't visual-inspect your way past it—but *after* cosmoline removal, not before. Crown and throat erosion are real limiters, absolutely. But I've seen force-matched shooters that printed terrible groups until the cosmoline came out, then tightened up 2–3 MOA just from proper degreasing.
As for @hollerpatch's point on provenance: dead-on. If it's matching numbers and original sights, leave it alone. But if you're already working on a shooter and considering a lap, you might solve half your problem first with heat and patience instead of reaching for the crown lap. I've done both. The lap is the nuclear option.
What cosmoline removal method are you guys using on your shooters?