Winchester MP4 CO2 rifle: Part 4
by Tom Gaylord, The Godfather of Airguns™
Writing as B.B. Pelletier
Today’s report is the final part of the guest blog from HiveSeeker. He tells us about the various pellets he tested and gives their results.
If you’d like to write a guest post for this blog, please email me.
Over to you, HiveSeeker.
This report covers:
• Scope notes
• More pellet testing
• I know there’s something going on
• The Winchester trio
• RWS Diabolo Basic pellets
• RWS Hobby pellets
• H&N Match Pistol pellets
• The magic bullet? Beeman hollowpoint coated pellets
• Retesting the best
• Other military pellet rifles to consider
In Part 2, I found five pellets that would group 7/8 of an inch (0.875 inches) or better with the Winchester MP4 CO2 rifle at 10 yards (Crosman Destroyer pellets, Crosman Destroyer EX pellets (sold only in discount stores), Crosman Premier Hollowpoint pellets, H&N Finale Match Pistol pellets, and Air Arms Falcon pellets). This was about as good as I expected based on my research before purchasing this gun. However, I’d hoped that I could do better, and most of the reader comments on this blog expressed even greater concern with the mediocre accuracy of this gun than with the ammo feed problem. I’m pleased to report some slightly better news.
But first, I made a minor modification to my scope setup. I mentioned the trouble two other shooters had sighting through the Leapers UTG 3-9X32 Bug Buster scope I mounted on this rifle. I had positioned the scope for my own eye relief, and eye placement proved to be a lot more critical for this compact scope than it is with my full-sized Leapers UTG 4-16X40.
However, at least part of the difficulty they experienced may have been due to a fairly low Picatinny rail on this rifle. When the included factory scope rings loosened after 300 shots, I decided to try a different style mount and also decided to go with high-profile rings. I was surprised at how much easier it became to sight through the scope — especially since I would have thought I wasn’t having any real difficulty before. For most shooters, I believe high-profile scope rings will be the way to go on this rifle. With my new scope setup, I was ready for some final accuracy testing.
One minor note here. On Picatinny rails there’s usually a little play in the scope mounts within the individual recoil grooves, and I usually slide both my mounts forward until they contact the forward stops and then snug them up right there. This is the direction the laws of inertia demand that the scope and mounts will want to go in relation to a rifle recoiling backwards beneath them (especially pneumatic or CO2 guns with simpler recoil than a springer). If the mounts are already braced against the forward stops, then there’s less chance for them to slip. However, on the Winchester MP4, I believe the semi-auto bolt re-cocking generates some recoil in the opposite direction — this may have actually loosened my initial scope installation. This time, I braced both scope mounts against the rear stops, and they seem to be holding fast, so far. I don’t have the equipment to verify this recoil theory, but it’s something to try if you run into a similar problem.
[Editor’s note: While Picatinny rails and Weaver rails both have cross slots to stop the rings from moving, Weaver slots are 3.5mm wide and Picatinny slots are 5mm wide. That’s the reason for the extra slop when Weaver rings are installed on Picatinny bases. And, for airguns, the pins should touch the rear of the slots.]
More pellet testing
I continued testing with seven new pellets, shooting 10-shot, 10-yard groups outdoors from a benchrest. I shot three groups with each pellet, and reported the best of three below. With my original accuracy testing, all the pellets I tried grouped about 1 inch, give or take a little. However, this time, the groups were generally tighter — even with pellets I’d previously tested. I believe this barrel may have a break-in period — roughly 500 shots by my estimation — and is now smoothed out a little. For this test, I used digital calipers to provide more exact group measurements — though, even with my sharp eyesight and a science background, you can take that third decimal place with a grain of salt!
I know there’s something going on
There definitely seems to be something going on between the number of pellets in the rotary cylinder and accuracy. I’d already mentioned that the last two shots of my 10-shot groups, involving a magazine swap, often opened up the final grouping. Remember that the ammo mag has 8-round cylinders, so finishing off a 10-round group required switching to a cylinder with only the two final pellets loaded. I could blame the repositioning of the rifle between magazine swaps, except that this is not a problem I’ve had with rifles that require pumping or cocking and get repositioned with every shot. This time, I kept specific track of when my final two shots opened up a group, with the results illustrated below.
This batch of testing also confirmed something else I thought I’d noticed before — groups often started off very small, then opened up as I emptied the magazine. Obviously, shooting more pellets will continue to open up a grouping. What I’m saying is that shot 10 was much more likely to miss the bullseye than shot 1, rather than having a similar probability of hitting or missing it. With this semiauto, I could lock myself into a rested shooting position and do nothing but breathe and squeeze the trigger for 8 shots. Barely moving, my aim and hold were rock solid. However, I almost felt like a spectator at times as I watched pellet strikes begin to roam wider and wider around my point of aim. I believe this is the same phenomenon I observed with my final two shots of each group. My best guess is that adjacent pellets in the magazine cylinder help reduce some CO2 blow-by, or that a full magazine cylinder does not shift or flex during firing as much as an empty one.
On the left, the first three shots with Beeman coated hollowpoint pellets go into 0.261 inches, center-to-center. Keeping my fingers crossed at this point! But the fourth shot (circled) opens this group up a bit more to 0.323 inches. Six increasingly scattered shots later, the final group on the right is now even broader at 0.682 inches (that fourth shot is circled on this target as a reference point). This pattern was observed repeatedly. This was not the best example I saw. It was just the one I interrupted to photograph.
The Winchester trio
Since this is a Winchester air rifle, I felt duty-bound to put the Winchester pellets through their paces. While they were the poorest performers of all the new pellets, their best groups were all still 1 inch or less: Winchester hollowpoint pellets (0.826 inches, center-to-center), Winchester pointed pellets (0.859 inches), and Winchester round nose pellets (1.000 inches exactly). As mentioned, the Winchester hollowpoints extended past the front of the rotary cylinder when fully seated and had to be pushed back in slightly before shooting. However, they caused no jams or other firing problems.
RWS Diabolo Basic pellets
The RWS Diabolo Basic pellets yielded the next largest group of the bunch, with its best-of-three at 0.791 inches. This pellet also produced the largest group that I observed during this second round of testing — 1.324 inches.
RWS Hobby pellets
The RWS Hobby’s smallest group measured 0.644 inches. This was the best group I’d seen from this gun so far. It’s approaching the as-of-yet elusive half-inch mark, but not quite there.
H&N Match Pistol pellets
I’d tested the more expensive H&N Finale Match Pistol pellets last time, but then I read about H&N Match Pistol pellets actually outperforming the Finales in another gun I own. That’s why I ended up with a tin of these to try. At 0.716 inches, they grouped slightly better than the Finales (even with retesting, as you’ll see in a minute) in this gun, too.
The magic bullet? Beeman hollowpoint coated pellets
Okay, I’ll concede right up front that half-inch groups at 10 meters aren’t all that magical in today’s airgunning world. However, with a review quoting Daisy Customer Service as stating that MP4 owners should expect 1-1/2 inch groups at 10 meters, and with no measured groups under 1 inch reported by anybody, I was pleased to finally break the half-inch barrier with Beeman hollowpoint coated pellets.
I did not have high hopes for what is literally the cheapest pellet I tested. However, a single Pyramyd Air review mentioned it performed well (thank you, DaveTee!); and, for under five dollars a tin, it went into the shopping cart. I shot this pellet last, and it surprised me. My three test groups yielded 0.682 inches, 0.386 inches and 0.442 inches. At the eleventh hour, I’d finally found a pellet that could shoot under half an inch. While one thing that became clear during accuracy testing is that my rifle does not perform the same with specific pellets as other’s MP4s, the Beeman hollowpoint coated is definitely one to try for anyone who owns an MP4, especially at this price point.
Thar she blows — these two groups shot with Beeman hollowpoint coated pellets clock in at under half an inch, at 0.386 and 0.442 inches, left to right. (Yes, the pellets are black.) Summer sun heating the barrel on one side caused the point-of-impact shift that can be seen here.
Retesting the best
To wrap up Part 4, I wanted to retest the best-performing pellets from before, which had all grouped 7/8 of an inch (0.875 inches) or less. I was pretty sure one or two could do better, and it seemed that my rifle was starting to produce tighter groups than it had straight out of the box. These were my results: Air Arms Falcon pellets (0.622 inches, beating out the RWS Hobby pellet for second place), Crosman Destroyer EX pellets (0.630 inches, taking third place and booting the RWS Hobby pellet to fourth), Crosman Destroyer pellet (0.742 inches, just a hair better than before), and H&N Finale Match Pistol pellets (0.963 inches, actually a little wider than first time’s 0.875 inches and still getting beat out by the H&N Match Pistol pellet). A small surprise were the Crosman Premier Super Match pellets (0.707 inches) and Crosman Competition Wadcutter pellets (0.720 inches), which I used for initial sighting-in of my new scope mount setup. Both bettered their original 1-inch groups by more than a quarter inch. Again, I believe this barrel is now broken in after 500 shots or so, contributing to these tighter groups and providing better overall accuracy than we saw in the first tests.
Below is a summary of best groups one inch or better from all accuracy testing:
While discovering the Beeman hollowpoint coated doubles my effective shooting range to around 20 yards for a 1-inch target, it’s a shame that this gun seems to be a “one-shot wonder” that shoots best with only one specific pellet. From the list above, there’s no single pellet type that this gun seems to prefer as direction for additional testing, so I hope that blog readers will be kind enough to comment if they find other pellets that group under half an inch in the Winchester MP4.
Other military pellet rifles to consider
For the conclusion to my evaluation of the Winchester MP4, I’d like to mention some of the other military replica pellet rifles prospective buyers might consider if they decide that the MP4 is not for them. (BB-only rifles and machine guns are not included here.)
I’ve already mentioned the MP4’s historically older sibling, the Winchester M14. A replica of its namesake, this rifle is also a dual-CO2 canister BB and pellet semi-auto. It uses the same ammo mag and offers the same velocity as the MP4. However, it has no scope rail and many don’t like the fact that the stock is composite instead of wood.
The unquestioned dominator of the military pellet rifle arena remains the Crosman M4-177. This M4 replica is a reliable single-shot BB and pellet pneumatic and bears the coveted Gaylord “Tom’s Picks” seal in the Pyramyd Air catalog. It’s available in a variety of tan or black color and accessory combinations. The new Crosman USMC MOS 0311 Rifleman (an exclusive Crosman variation of the M4-177) appears to be another variant of this very popular replica. This is the gun I had in mind when I mentioned that more accurate rifles than the Winchester MP4 are available for half the price.
The Crosman MK-177 is a replica of the Magpul Masada (now being produced as the FN SCAR). This composite-stock pneumatic offers higher velocity and similar accuracy to the M4-177 (also beating the Winchester MP4 in the latter department, and for half the price). This rifle is a BB and pellet single-shot. B.B. Pelletier recently used the MK-177 to test the Leapers Accushot Scout Scope. While many disparage the bolt placement on the left side of the receiver, I own — and love — one of these rifles and never minded it (this is a replica — check on which side the bolt is actually located on the Magpul Masada). The MK-177 is available in tan or black and has two kit variations.
The Crosman Crosman MTR77NP is an M16 replica that is a single-shot Nitro Piston gas springer. This pellet rifle offers the highest velocity of any of these military replicas but requires heavy cocking effort due to the short barrel. It’s available in only black but comes in open-sight or scoped versions.
If you actually own an AR/M4 firearm, the Crosman MAR177 AR-15 Upper PCP conversion kit replaces the firearm upper with a .177-caliber competition precharged pneumatic unit. Designed specifically for 10-meter competition, velocity is a very nominal 600 fps. This is the most expensive option for a military pellet rifle (and a significant detour from the standalone guns listed here), but it seems like an ideal way to expand where and when you can shoot your military long gun.
The Beretta CX-4 Storm is an 88-gram CO2-powered replica of the tactical firearm of the same name. This semiauto’s claim to fame is the 30-pellet belt magazine, capable of ripping through a tin of pellets in no time. Open-sight and red-dot versions are available, though a scope can be mounted on the Picatinny rail.
The Gamo MP9 copies the B&T MP-9 9mm SMG and is unique among the CO2-powered BB submachine guns in handling pellets as well. Interestingly, this gun is listed as using the same ammunition magazine as the Winchester MP4 and M14, making it a 16-shot semi-auto (with the magazine flip). I included this odd-gun-out because it has a (collapsible) stock and scopeable Picatinny/Weaver rail.
The options for new military replica pellet rifles are very limited at the moment. I hope that this blog has sufficiently informed readers about the Winchester MP4 to make an educated choice if buying one — or to achieve the best performance from their rifle if they already own one. I also hope that manufacturers will look to success stories like the Crosman M4-177 as well as the burgeoning airsoft market and bring some novel products to this mostly unexplored marketplace.
Editor’s final comment: HiveSeeker has done a super job in testing, researching and documenting his work on the Winchester MP4. I think his report will stand as the best article written about the airgun for a long time.