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LAPCO Autococker Breech-Sizer

© Ravi Chopra, 1998

Just about everyone who shoots an Autococker eventually runs into a situation where their barrel has too large an ID for the paint they’re shooting. There is no problem as long as you keep the barrel up or keep shooting, but the moment you stop and tilt the barrel down, the next paintball rolls out the end of the barrel. A loose barrel also can lead to poor efficiency and inconsistent velocities over the chronograph.

You could just buy another barrel, this one with a tight-bore for small paint. But then, not everyone has the money (or the desire) to go out and buy another top-dollar barrel just for small paint.

LAPCO designed the breech-sizer to adress just this problem.


The breech sizer is essentially a step or tight-bore section of barrel that is threaded in between your ’gun and loose-bore barrel. Screw your barrel into the breech sizer, then screw the breech-sizer into the ’gun. As a very tight initial section, the breech-sizer should stop your paint from rolling out and provide a much better seal for your small paint. It is important to make sure that the barrel you use with the breech-sizer has a larger ID than the sizer you’re using or you will likely get very poor performance and a lot of barrel breaks.

LAPCO is manufacturing these in two IDs: 0.685" and 0.683". The 0.685" reducer is meant for use with most smaller paints like Marballizer and Pro-Ball. The 0.683" reducer is meant for extremely small-size tournament paint like All Star and Evil. For most people experiencing roll-out, the 0.685" sizer is going to be the appropriate one to use.

The breech-sizer is manufactured from aluminum and has the same black industrial hardcoat used on LAPCO barrels. After years of using LAPCO barrels, I can say with confidence that this is a very smooth and durable surface that will not significantly scratch or wear with extended use.The quality of construction is typical LAPCO: meticulously designed and dimensioned to WGP specifications for a perfect fit. The outside of the sizer is knurled to give you a good grip to make it easy to remove, and it is engraved with the ID and paintgun type it is for use with (LAPCO makes a similar product for other ’guns as well).

Design/Construction rating [4]


Assesing the performance of the LAPCO breech-sizer is a difficult task. There are just too many barrels out there to test it with all of them. After using it for a while, I do feel that there are a few general aspects of its performance that will be consistently found.

First, the breech sizer will definitely stop roll-out if you use the right one with the right paint. The 0.685" sizer will stop anything but the tiniest tournament paints, and the 0.683" will stop even those microscopic paints dead.

Second, if your paint is loose enough to be rolling out of your barrel, the breech sizer will improve your efficiency measurably. Depending on how much better a fit the brech sizer gives you, you could see anywhere from a 10 to 50 fps increase in velocity, allowing you to dial it down and save air.

LAPCO claims that you will see an improvement in accuracy with the breech-sizer as well. I found this to be only occasionally true. The improvement in range and accuracy will depend highly on the barrel and paint you are using. With some combinations you will find an improvement. With others you won’t. Unfortunately, it is not very predictable. The only way to find out is to try it. Though it didn’t always improve accuracy, I never found it to degrade performance.

It is important to note that these advantages will only be found it your barrel is too loose for the paint you are using (the paint can roll right through it), and that the reducer is of a smaller ID than the barrel you are using it with.

It is also important not to use these sizers with paint that is too large for them. Huge paint like Nelson will very likely break in the 0.685" sizer when you try to push it through that narrow stricture. And anything that fits well in the 0.685" (most paints out there) will be too large for the 0.683".

Performance/Versatility rating [3]


The LAPCO breech sizer has an a street-price around $17.50. This price is more than fair given that a whole new barrel can cost anywhere from $60-$150 these days. It also comes with a full money-back guarantee.

Price/Warranty rating [4]


The simple fact is, nothing can really beat a barrel that is itself perfectly sized for the paint you are shooting. Not everyone can afford a bag full of barrels, though. If you can only afford one good aftermarket barrel, buying a good medium bore barrel (0.689"-0.691" ID) and a LAPCO breech-sizer is an economical and effective way to get an acceptably good fit for just about any paint you might run into. It won’t give you all of the advantages of a perfectly sized barrel, but it will give you about 90% of the performance for 20% of the price. This is a particularly good solution if you already have a great medium bore barrel and you can’t find a tight-bore that shoots as well for you.

All material at this site is © Ravi Chopra, 1999