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ASG Factory Upgrade Tightbore Inner Barrel for McMillan M40A3 Sportline Airsoft Sniper Rifles

ID: 11924 (BRL-ASG-18471)
4.7 stars, based on 3 reviews
ASG Factory Upgrade Tightbore Inner Barrel for McMillan M40A3 Sportline Airsoft Sniper Rifles
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The manufacturer of this product enforces a strict minimum advertised price (MAP) policy which excludes this product from any additional discount coupon codes. This item, however, may qualify for free shipping.


  • Brass construction
  • 6.03mm diameter bore
  • Factory OEM drop-in upgrade barrel
Increase your precision and range with the precision inner barrel.

An upgrade barrel for M40A3 SportLine Airsoft sniper rifle. This precision barrel features a slightly smaller inner diameter to provide an improvement in accuracy.

Manufacturer: ASG


Length: 465mm
Inner Diameter / Bore: 6.03mm (+0.01mm)
Material: Brass
Compatibility: For ASG McMillan M40A3 SportLine Sniper Rifles

About ASG

ActionSportGames is a worldwide leader in the business of replica firearms and accessories manufacturing including Airsoft guns, Airguns, CO2 guns and firearms replicas. We specialize in 1:1 scale replica guns and accessories for fun, action, sports, entertainment and collection. Today were proud to be recognized as the innovator and manufacturer of the CZ EVO3 A1 AEG and having introduced several Airsoft versions of this popular Airsoft gun to the market.One of our goals is to become the preferred supplier in the firearms replica business through worldwide license agreements, quality brands and premium service before, during and after sales.

3 Customer Reviews

(Write a review)

by Darryl W. on 10/23/2021
"Very happy with this upgrade. It was easy to install but you do need to shave down the barrel spacer as the new barrel does not have the soccer groove of the original. The barrel to hop up fit was identical to the original barrel so no modifications were needed on that end. The M40A3 was pretty accurate out of the box so this just helped improve and already well performing rifle, I’m now grouping all my shots in a 2 inch square at 120 ft.
by Daniel S. on 12/16/2019
"Nice upgrade for the M40A3 to a tightbore inner barrel. Mine wasn't made quite right, and was missing the groove for the barrel spaces, so I had to shave down the spacer a little bit... still works great though!

Be careful when opening the hopup as there are a few small parts that you can easily lose... I highly recommend looking it up on youtube before you start!
by michael z. on 06/20/2022
"it fits in my ASG M40A3 just fine, minus the barrel stabilizer, there's no notch in the barrel to accommodate. luckily the thread adapter on my outer barrel helps hold it in place but it like to think the stabilizer is there for a reason so i may need to see if i can dremel the spacer out

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