by B.B. Pelletier

Part 1

We sure heard from a lot of readers on the first report of the Crosman 1377. Of all who responded, only one didn’t like the gun, and he was a Canadian who later learned that we have a more powerful version in the U.S. The rest of you seem to be split 70/30 in favor of customizing the pistol vs leaving it stock. The No. 1 custom feature is a pair of wood grips, and Ralph Brown’s name came up more than once. Several said that grips are easy to make, and I agree.

Some of you also mentioned the steel breech that Crosman sells out of the Custom Shop. This is a DIY project that I’ve been assured is not beyond most of you. I’ve done the job with other Crosman CO2 guns that are quite similar, and I’ll add my vote that a breech swap is pretty easy.

Today, I’ll do the velocity testing. I learned some very interesting things about this pistol as I shot it, and I’ll pass them along as we go.

Test 1. Velocity as it relates to the number of pump strokes
For this test, I used Crosman Premier 7.9-grain pellets. The purpose is to show the relationship between the number of pump strokes and the velocity.

Pumps/Velocity
3…345
4…393
5…424
6…451
7…469
8…484
9…499
10…515 (No air remaining after shot)
11…520 (No air remaining after shot)
12…515 (No air remaining after shot)

We can learn several things from this chart. First, the velocity increase with each successive pump stroke diminishes. From 3 pumps to 4, the additional stroke raises the velocity 48 f.p.s.; but, from 9 pumps to 10, the increase is just 16 f.p.s., or one-third as much. Also, while 11 pumps did produce greater velocity than 10, pumping once more actually slowed the gun. So, 10 pump strokes should be considered maximum.

I also noted that the pistol warmed up considerably during this test. A second test revealed some interesting numbers.

Test 2. Velocity as it relates to the number of pump strokes after the gun became warm

Pumps/Velocity
3…361
4…387
5…416
6…445
7…451
8…463
9…466
10…474 (No air remaining after shot)
11…486 (Some air remaining after shot)

Some velocity was lost between this test and the first. I thought this was due to the gun being warm, but later testing revealed that wasn’t the case.

Test 3. Velocity after waiting 3 hours for gun to cool

Pumps/Velocity
3…331
6…430
10…490

I shot only three times because we know the other shots will lie at their respective places in the string. Obviously, the gun has settled into a slightly lower velocity after a short break-in. Did the over-pumped shots have anything to do with it?

Test 4. Velocity with other pellets
The surprise was that Hobbys weren’t much faster than Crosman Premiers were on the second test.

RWS Hobby
Pumps/Velocity
3…344
6…447
10…511

RWS Superdome
Pumps/Velocity
3…328
6…420
10…481

JSB Exact 8.4-grain domed
Pumps/Velocity
3…346
6…421
10…443

Test 5. Velocity with other pellets, after oiling
In this test, I oiled the pump head with Crosman Pellgunoil before starting. I put in 9 drops and worked it into the pump chamber after every 3 drops by partially pumping the handle without completing the pump stroke.

RWS Hobby
Pumps/Velocity
3…360
6…453
10…528

RWS Superdome
Pumps/Velocity
3…327
6…429
10…494

JSB Exact 8.4-grain domed
Pumps/Velocity
3…354
6…442
10…504

Oiling increased velocity a little by helping to seal the pump head. It also goes through the gun and gets on every seal along the way. This is a real health tonic for a pneumatic airgun.

Well, the 1377 is certainly not 600 f.p.s. with any pellets I would use. However, in the interest of fairness, I did try the gun on 10 pumps with Crosman Silver Eagle hollowpoints. They averaged 604 f.p.s., so this pistol met spec.

Pumping not difficult
Unlike a pneumatic rifle, the pump strokes don’t seem to get much harder as you approach 10. That’s always been true of multi-pump pistols. I suppose it has to do with a smaller compression chamber, but I’m not sure.

Next time, we’ll try her on targets and see how accurate a 1377 is.