with Andrew L. Butts
4 new M16 bolt design fixes
New Relia-Bolt promises to improve rifle design weaknesses
In an effort to improve the M16’s design without changing parts commonality, Sharps Rifle Company — based in Wyoming — has announced the Relia-Bolt that is designed to address several weaknesses in the original bolt design.
At first glance, the Relia-Bolt looks like a standard M16 bolt with the locking lugs beveled off. While there is some new geometry in play, there also is more to the new part than just some reshaped lugs.
The new bolt is made from S7 tool steel rather than the more common Carpenter 158. S7 is a shock-resisting tool steel and because it is air-hardening steel, it is stable in heat treatment.
It also is used for medium cold work tools and dies, for plastic-molding dies, shear blades, medium hot work dies, master hobs and for component parts of many products.
While Carpenter 158 has done an excellent job over the years, there are still cases of bolts failing at either the cam pin hole or on the locking lugs closest to the extractor. The change to S7 will hopefully result in a bolt that will last significantly longer under the stresses found in a self-loading rifle.
In addition to the change in material, the Relia-Bolt is coated with NP3. NP3 is an electroless nickel plating that contains Teflon as a lubricant. The NP3 coating provides corrosion resistance.
The bolt is also smooth, so most of the crud from use will wipe off with a patch and a little solvent. Carbon build-up deposited behind the gas rings is removed easily after soaking for a few minutes in BoreTech C4 carbon remover.
From the front, the lugs around the face of the bolt are tapered or sloped where they enter the barrel extension. This reduces the surface area of the lugs and basically turns each lug into its own crud cutter. The idea here is to allow the bolt to enter the barrel extension even if there’s heavy fouling present inside the rifle.
Relia-Bolt in the Field
Based on my own personal experiences with the AR platform over the years, I can think of only one or two instances where the Relia-Bolt might have made a difference.
One was a loose primer that came dislodged during firing and found its way into the barrel extension. The second instance was based on a failure to feed that resulted in bullet setback and spilled gunpowder inside the rifle.
In both these occurrences, a nasty malfunction was the result.
To simulate the primer malfunction, I de-primed two fired .223 cases and dropped spent primers inside the barrel extensions on two guns. One rifle was fitted with a traditional M16 bolt while the other had the new Sharps product.
On the conventional AR, the bolt fully closed on the first drop but wouldn't close on attempts two and three. On the last attempt, I had to mortar the gun to get it open. The spent primer was smashed badly and was no longer recognizable as a spent primer.
The Relia-Bolt rifle closed and opened fine on the first and second attempts. On the third attempt, the action didn't fully close and it took a pretty good pull on the charging handle to get the rifle open.
After I dumped the spent primer out, I noticed it was slightly flattened on the edges but was not nearly as deformed as it was in the first rifle.
I repeated the spent primer test live fire with the Relia-Bolt. The first round chambered and fired but the bolt failed to close fully on the second round. Opening the bolt a couple inches and then letting it close again got it fully into battery, and I fired an additional four rounds without issue.
Continuing with my testing, I poured a cartridge case’s worth of gunpowder into the barrel extension. Some of the powder went into the extension but more also went into the chamber.
While the action would still cycle, the chamber was too clogged to allow a live cartridge to chamber. A quick plunge with a GI chamber brush cleared enough of the fouling away to let ammunition fit, and the rifle fired fine afterward even though there was quite a bit of spilled gunpowder remaining in the barrel extension.
Sharps recently submitted a rifle and Relia-Bolt to an independent lab for testing. The rifle/bolt combo completed a 7,500 test fire with no malfunctions, according to the company. In Sharps’ own in-house tests, they have a sample bolt nearing 10,000 rounds fired.
In my opinion, Sharps has taken a new and interesting approach at improving the legacy M16 system with the Relia-Bolt. In should be interesting to see how it holds up over the long haul.