Short Stroking an AR9 - Why?

[22lr]

I am in the process of piecing together an AR9 and my head is totally spinning right now trying to pick a buffer and spring.
Regardless, I have come across a few kits designed to intentionally short stroke the rifle (JP and Blitzkrieg), but have not seen an explanation of what it is and why you would want to do it.

What is the advantage of short stroking an 9mm AR? I thought short stroking was a bad thing!

Would you lose the ability to lock the bolt back? Would you also lose the last round bolt hold open?

 

[steve8140]

You would short stroke the bolt for a few reasons.
1) 9mm AR’s are known to break the bolt catch because if the bolt over travels and slams forward there is much more force that can hit the hold lever. You want enough travel to eject the spent casing and go a little past the bolt catch.
2) Having a shorter travel allows for less dwell time between shots. The gun will cycle and be ready to fire again faster. (This is the competition mindset).

 

[E.Stoner]

My guess is It's "unnessary" rearward motion to fully cycle the bolt for the shorter 9mm cartridge for faster cycling and also less felt recoil not having the bolt slam back to the buffer.

 

[22lr]

You would short stroke the bolt for a few reasons.
1) 9mm AR’s are known to break the bolt catch because if the bolt over travels and slams forward there is much more force that can hit the hold lever. You want enough travel to eject the spent casing and go a little past the bolt catch.
2) Having a shorter travel allows for less dwell time between shots. The gun will cycle and be ready to fire again faster. (This is the competition mindset).

Makes sense. For the cons though, am I correct in thinking that you will lose the bolt hold open? That sounds like it could be a pain.

 

[steve8140]

Makes sense. For the cons though, am I correct in thinking that you will lose the bolt hold open? That sounds like it could be a pain.

If you have the over travel then yes. It’s not a matter of if but when.
If you set it up properly then you should be ok. (Should be, there’s always a chance).

It’s not a big deal either way unless it breaks and jams the gun. If it does then just clean out the broken piece and the gun will run just fine but without the last round hold open. My colt style with modified uzi mags doesn’t work on those mags anyways. Some people pull out the bolt catch lever completely.

Words of wisdom that people have told me:
“If you go to slide lock you’re doing it wrong”.
“If you’re not shooting you should be reloading”.

 

[Yosemite Sam]

I have installed blizkrieg in mine
works well, but you really have to somewhat muscle it to lock in the open position
i guess that w get better with age, and lotsa lead down the tube

 

[DJBrad]

I’m going to add about $1.25 to my travel length since I did notice the bolt catch failing from over-travel last range trip.

 

[steve8140]

I’m going to add about $1.25 to my travel length since I did notice the bolt catch failing from over-travel last range trip.

I’ve done that, I carry a bunch of quarters in my PCC bag when I’m testing and making adjustment.

 

[jjm1986]

Buffer might be a bit heavy or the buffer spring. I have new frontier armory 9mm build. Works like a charm.

 

[millcity]

You would short stroke the bolt for a few reasons.
1) 9mm AR’s are known to break the bolt catch because if the bolt over travels and slams forward there is much more force that can hit the hold lever. You want enough travel to eject the spent casing and go a little past the bolt catch.

Sorry if this is a dumb question but is there a way to check this without live firing ?

 

[Uzi2]

Here's one reason to limit bolt travel.

My buffer was too light and too short allowing the bolt carrier group to travel too far to the rear. This is the stoppage I encountered just as you see it upon opening the gun.

 

[chris_1001]

What Steve8140 said.

It’s mostly for saving the bolt release.

I have a 7.5 ounce “extended” buffer in my new frontier arms build. My idpa PCC gun.

Had to slightly tweak (bend) my lrbho, but it work flawlessly now. Nothing to do with the buffer set up at all.

I did the quarter trick with a standard carbine buffer and it worked just fine. Just decided to use the correct parts.

Oh, and after a while the quarters were pretty dented.

That said I also right off the bat I used a better quality bolt release as I knew about this issue.

 

[chris_1001]

Sorry if this is a dumb question but is there a way to check this without live firing ?

Hold the bolt release (so it actuates) and cycle the bolt with the charging handle. It should lock the bolt with maybe ~1/8” of over travel.

 

[SKumar]

This got me thinking:

A polymer lower is totally appropriate for an AR9 with short stroke buffer. The big fear was the BCG slamming into the rear lower (buffer insert) thus causing a crack. With short stroke, there's no worry since the BCG won't travel that far back. The only thing polymer will need to withstand is the energy from the recoil, which we know polymer lowers can do in handguns.

 

[Lxpony]

I have 3 ar9 uppers. 4", 5.5" and 8.5" my 4" would short stroke shooting my standard go-to cheap steel case Wolf ammo with the standard Sprincoblue spring and KAK 7.5 ounce buffer. This combo was fine for the 5.5 and 8.5" barrels but not the shorty. I swapped out the Sprinco for a basic ar15 spring and kept the buffer the same. This cured all cycling issues. You need to play around with combos. Also realize that ammo affects it too. Stick with the same ammo as your control group and play with the buffer and spring combo . Good luck.

 

[Remote Camper]

Couldn't you just throw in a wooden dowel behind the buffer IN the spring to limit the travel to exactly what you'd like.
Probably cheaper than $1.25.
Or a larger Dia. dowel to sit to the rear of the spring.

Or if low tec is just too "For the Poors" for you, this one from MBX looks simple and affordable

MBX Extreme

The Next Generation Race Ready Competition Magazines & Performance Parts

mbxextreme.com

RC

 

[ReluctantDecoy]

Some of the fancy pistol or multi-stage short stroke systems remove the bolt weight and integrate with the bolt to the point that you don't even need to use the buffer spring detent anymore. Their bolt travel is much shorter by design, but keep in mind that many of the short throws don't allow for LRBHO. Your manual of arms will more likely resemble an MP5 mag changes.

 

[Wrench75]

This. PCC Adjustable Recoil System AR-9mm



and that. Standard Bolt AR-9mm

 

[ReluctantDecoy]

This. PCC Adjustable Recoil System AR-9mm



and that. Standard Bolt AR-9mm

I just got that adjustable buffer before things went haywire. Haven't really had a chance to fully test it yet. I tried to contact the company with a question about the spacers. I had to remove one to get BHO clearance. I assume that's fine considering there are two of them, but wanted to hear what they would say.

 

[Wrench75]

I just got that adjustable buffer before things went haywire. Haven't really had a chance to fully test it yet. I tried to contact the company with a question about the spacers. I had to remove one to get BHO clearance. I assume that's fine considering there are two of them, but wanted to hear what they would say.

Are you using a pistol length tube or carbine length?

 

[ReluctantDecoy]

Are you using a pistol length tube or carbine length?

Carbine for this buffer kit. I initially installed it as shown with the two silver washers in place, but I wasn't getting appropriate clearance for BHO.

 

[Wrench75]

Carbine for this buffer kit. I initially installed it as shown with the two silver washers in place, but I wasn't getting appropriate clearance for BHO.

OK just making sure. You didn't get this from me...

612-961-8619 That is the personal cell for the owner of Taccom. His name is Tim. No I'm not kidding, it really is his number. I left a message in their CS system when I was building my PCC and he called me back on his phone while driving home. We talked for about 30 min. Good guy, very helpful.

 

[ReluctantDecoy]

OK just making sure. You didn't get this from me...

612-961-8619 That is the personal cell for the owner of Taccom. His name is Tim. No I'm not kidding, it really is his number. I left a message in their CS system when I was building my PCC and he called me back on his phone while driving home. We talked for about 30 min. Good guy, very helpful.

Wow. Thanks! Although, I'd feel kind of like a douche calling him now during all of this to discuss buffer spacers. Maybe I'll wait for ranges to open back up again and give him a text.

 

[travx]

Wow. Thanks! Although, I'd feel kind of like a douche calling him now during all of this to discuss buffer spacers. Maybe I'll wait for ranges to open back up again and give him a text.

You can also email him: [email protected]
I emailed him on Sunday and he replied in less than 10 minutes.

 

[ReluctantDecoy]

You can also email him: [email protected]
I emailed him on Sunday and he replied in less than 10 minutes.

That's the one I emailed back in March where I didn't hear back. Maybe I'll try again.

 

[Wrench75]

You can also email him: [email protected]
I emailed him on Sunday and he replied in less than 10 minutes.

That's where I left a message a few min after they had closed. He must have gotten an alert or something and called me on his way home. That was actually the deciding factor in me buying their gear. I respect the shit out of that kind of work ethic.

 

[Wrench75]

Wow. Thanks! Although, I'd feel kind of like a douche calling him now during all of this to discuss buffer spacers. Maybe I'll wait for ranges to open back up again and give him a text.

I hear ya. However, considering the type of company he owns, I'm sure he'd understand.