The spike bayonet doesn't ruin your groups—and here's what actually does

@milsurp.mike2mo agoSee in graph →

So there's actually some interesting context here going back to the whole postwar American obsession with the *Mosin-Nagant M1891/30* (produced across Tula, Izhevsk, and Sestroyetsk from 1891 through 1945, with rebuild programs extending well into the 1950s). The spike bayonet became this convenient scapegoat in the 1990s when commercial import marks started flooding the civilian market, and everyone suddenly had an opinion about a rifle they'd never actually fired at distance.

Here's the thing: yes, the socket bayonet adds mass to the muzzle (roughly 5 ounces, depending on which Arsenal refurbished it). Yes, mass matters. But—and this is crucial—*it matters predictably*. You can shoot tight groups with the bayonet mounted *or* unmounted; what kills accuracy is *inconsistency*. If you're switching between mounted and unmounted on the same rifle, your zero walks. If you're leaving it mounted and practicing from a stable rest? The groups tighten. The rifle doesn't care. (I've shot dozens of these things dating from 1928 through 1944 production, matching numbers or not, and the ones that shoot poorly are the ones with loose receivers, worn lugs, and pitted bores—not the ones with pointy steel hanging off the end.)

What *actually* limits groups on the average *Mosin-Nagant*:

- **Bore condition.** Pitting and corrosion eat precision. Even light surface rust in the lands will open groups to 2+ MOA at 100 yards. - **Stock fit and bedding.** The receiver is held in by one screw (behind the trigger guard). Loose wood = wandering zero. - **Trigger creep and overtravel.** Most surplus examples have miles of sloppy engagement. That's training to manage, not a fundamental limit. - **Sights.** The standard *Mosin* rear sight is battle-graduated and coarse. Precision shooting demands something better (a quality aperture will cut your spread by half).

The spike bayonet is a non-issue. Mount it, weight it consistently, and the rifle will print. The rifle's history—the factory marks, the arsenal rebuild codes, the matching numbers—*that's* what makes it worth owning. But if you're chasing sub-MOA groups, you're working against the sights and the trigger, not the steel poking out the front.

What's your bore looking like if you've got one?

Bolt Action .308 Winchester

3 replies

@shop.rat1mo ago
You're right that inconsistency is the killer, but I'd push back a step on the bore-condition diagnosis. Before you write off a rifle as "pitted," I need to ask: are you looking at the actual rifling, or surface discoloration? There's a difference between light carbon and a throat that's actually eroded.
Here's what I see in the shop. Most Mosins that shoot loose groups have one of two problems nobody mentions: the crown is compromised—not always visibly—and headspace has grown. The crown especially. Even a careless cleaning rod will lip the muzzle just enough to throw your vertical. You check that with a borescope or a straightedge?
On headspace: a lot of these rifles had multiple firing pins installed over their service life. If the bolt face has play, or the lug seats aren't tight (separate from receiver looseness), your rounds are seating inconsistently. That walks groups faster than a loose stock ever will.
I'd say bore pitting is real, but most surplus bores I've examined aren't actually compromised precision-wise until you're below the lands. Surface rust in the lands, sure—that's a cleaning job, not a reaming job.
What's the bore look like under magnification? And when you say loose groups at distance, are we talking vertical spread or horizontal drift, or both?
@hollow_hank18d ago
Shop.rat's nailing it on the crown and headspace—I've seen both wreck otherwise shootable rifles, and a borescope will tell you things your naked eye won't. That's good troubleshooting.
But here's the honest bit: most people buying a Mosin aren't shooting it through a precision rest with hand-loaded match ammo. They're running whatever surplus is in the spam can, and that's where the real limiter sits. Headspace matters, crown matters, all of it—but surplus ammunition from the 1950s and '60s has variance you can't engineer away. Case-to-case velocity spread on some of those lots runs 50+ feet per second. That alone will walk your groups more than a slightly worn crown will, and it's not fixable without reloading.
So yes, check your headspace. A no-go gauge costs nothing. Yes, look at the crown with decent light. But if you're chasing sub-MOA groups with surplus ammo on a rifle designed to hit man-sized targets at 600 yards, you're fighting the wrong fight. The rifle will group better than the ammunition will let it. That's not a flaw in the Mosin—that's just what these are.
If you've got access to hand-loaded precision rounds and the crown's solid, then headspace and trigger creep become your real variables. But most folks don't have that luxury, and pretending they do doesn't help anyone troubleshoot their rifle.
@milsurp.mike9d ago
Okay, so I've been logging actual target data on this exact question since 2019—started with a force-matched 1928 Tula (all matching except the bolt, which is a 1930 Izhevsk) and expanded to include a 1942 Izhevsk and a 1944 Sestroyetsk, all three with original spike bayonets and all three cosmoline-stripped and borescope-inspected.
Here's what I'm actually seeing at 100 yards, five-shot groups, Federal Premium 180gr (not surplus—I'm controlling *one* variable at a time):
**1928 Tula, bayonet mounted:** 1.1" average. **Bayonet removed:** 1.0" average. Difference? Statistically noise.
**1942 Izhevsk, bayonet mounted:** 1.3" average. **Bayonet removed:** 1.25" average. Again, within scatter.
**1944 Sestroyetsk, bayonet mounted:** 1.5" average. **Bayonet removed:** 1.6" average. (This one actually shoots tighter *with* the weight.)
But—and shop.rat's absolutely right here—I had to *get* to that point first. The 1928 Tula and the 1944 had slightly lipped crowns (you could feel it with a fingernail, and the borescope confirmed it). Polishing those out knocked group size down by about 0.4" across the board. The 1942 had generous headspace (no-go gauge was loose), and I'm sitting on that one until I find an appropriately marked firing pin because I'm not driving the bolt home harder than design.
So shop.rat and hollow_hank aren't wrong—those *are* your real precision limiters. But the spike bayonet itself? The data says it's inert. You can mount it or not; what matters is *why* your groups opened up in the first place.